Unit - 6
Steam condensers
Q1) What is steam condenser?
A1)
Steam condensers
A steam condenser is a closed vessel-kind warmth exchanger implemented to transform low-stress exhaust steam from the turbine to water.
A steam condenser is a mechanical tool hired to condense exhaust steam of the turbine into the water. It conducts this procedure with the assist of cooling water that circulates interior it from the cooling tower. The stress inside a steam condenser is held under the atmospheric stress to decorate efficiency. It is generally used to decrease the backpressure of the exhaust on the turbine quit.
Functions of the Steam Condenser
The reason of the usage of a steam condenser is: supporting maintain the stress low (under atmospheric stress) on the steam turbine quit to get most feasible strength and decrease the unique steam intake of an electricity plant.
Offering natural feed water to and from the new nicely.
The water is once more pumped to the boiler the usage of a boiler feed pump. Elevating the warmth switch fee with the aid of using casting off different non-condensable gases from the exiting steam.
Q2) Explain various Steam Condenser Parts
A2)
Steam Condenser Parts
The additives required to perform a steam condenser are as follows.
Condenser
It is used to condense the steam.
The steam with low stress offers its warmth to the coolant (right here water from the cooling tower), and it converts into the water thru the condensation procedure.
Condensate Extraction Pump
A Condensate Extraction Pump (CEP) is a pump mounted among the condenser and the new nicely to switch the condensate from the condenser to the new nicely. Hot Well It is a pit among the condenser and the boiler. It takes the condensate with the aid of using condensate pump from the condenser. The feed water is carried from the new nicely to the boiler.
Boiler Feed Pump
It is a pump positioned among the new nicely and boiler to supply the feed water from the new nicely to the boiler. This is achieved with the aid of using growing the condensate stress above boiler stress.
Air Extraction Pump
It is a pump applied to extract or take away the air from the steam condenser. Cooling Tower It is a tower containing bloodless water, and this water is furnished to flow into within the condenser to chill the steam. Cooling Water Pump It is a pump mounted among the condenser and the cooling tower. It circulates the coolant inside the condenser.
Q3) Write a short note on principle of steam condenser.
A3)
Steam Condenser Working Principle
In this section, we are able to supply a simple description of the way a steam condenser works. A glide of cooling water is constantly circulating from the condenser interior a steam condenser to the cooling tower and the cooling tower to the condenser.
When low-stress exhaust steam leaves the turbine and passes thru the condenser, it loses the warmth and condenses into water. The circulating cooling water plays the extraction of the warmth from the steam.
Two forms of gadgets are mounted at the condenser: the condensate extraction pump and the air extraction pump.
Therefore, whilst the steam condenses into water, it re-circulates once more to the steam generator with the assist of a condensate extraction pump. Using the air extraction pump, a vacuum (the stress under the atmospheric stress) is created within the condenser in order that cooling water can flow into effortlessly and additionally the condensate glide may be stabilized.
Due to the low stress within the condenser, the air enters the gadget in order that the condenser is packed with a combination of water, air, and steam.
Types & Classification of condensers
Three Main and Different Types of Condensers.
- Air-cooled condenser
- Natural Convection
- Forced Convection
- Water-cooled condenser
- Double Tube Shell and Coil Condenser
- Shell and Tube Condenser
Evaporative Condenser
Condensers primarily based totally at the condensing medium used to eliminate the warmth from the system, consist of 3 one-of-a-kind kinds. None of those 3 one-of-a-kind styles of condensers has mainly no blessings over the alternative. Depending at the situation, everyone have to be used appropriately. We are going to tricky at the features of those 3 condenser kinds with inside the following.
Air-cooled Condenser
Condensers of this kind use air because the outside fluid to reject the warmth from the system. Air-cooled condensers typically have copper coils in which refrigerant flows in. But this isn't always the complete story; this kind is subcategorized into subsets: herbal convection and compelled convection.
Q4) What do you mean by natural convention?
A4)
Natural Convection
In this kind of condenser, air involves touch with heat coils, soaking up the warmth of refrigerant in the coils, therefore the temper
Natural Convection
In this kind of condenser, air involves touch with heat coils, soaking up the warmth of refrigerant in the coils, therefore the temperature of air increases. As the nice and cozy air is lighter, it is going up and the bloodless air replaces and once more the bloodless air comes to the touch heat coils to reject the warmth. This herbal cycle maintains till the refrigerant loses its warmth. Since the glide charge of air is small and the radiation warmth switch is likewise now no longer very high, the blended warmth switch coefficient in those condensers is small.
As a result, an especially massive condensing floor is needed to reject a given quantity of warmth. Hence those styles of condensers are used for small capability refrigeration structures like family fridges and freezers.
Forced Convection
One of the alternative styles of condensers is compelled-convection. A fan or a blower does play the maximum essential position in casting off warmth from the refrigerant in the coils. The fan blows the air into the finned coils. A critical tip needs to be referred to right here and its miles that the fins of compelled convection condenser are positioned tightly subsequent to every other; so, if the dirt and dust fill the mild area among the fins, the air flowing and warmth rejection faces huge trouble.
Forced convection kind condensers are usually utilized in window air conditioners, water coolers, and packaged air con plants.
Water-cooled condenser
As it is able to be guessed, this kind of condenser makes use of water as fluid to eliminate warmth from the refrigerant. It is apparent that water-cooled condensers are used in which we've got an ok deliver of water. This kind, itself has 3 one-of-a-kind kinds: See All Water-Cooled Condenser for Sale
Q5) What is double tube?
A5)
Double Tube
Double tube condensers have a tube of water inner a massive refrigerant tube. The water absorbs maximum of the refrigerant warmth, however because the refrigerant tube is in touch with the herbal move of air, a part of the cooling system is on herbal convection. Although double-tube condensers usually had been used with inside the past, the massive wide variety of gaskets and flanges utilized in those warmth exchangers ends in protection problems.
Shell and Coil Condensers
In a shell-and-coil condenser, a welded shell consists of a coil of finned water tubing. In this kind of water-cooled condenser, the new refrigerant flows with inside the shell even as the cooling water circulates in the coils and condenses the refrigerant. It is normally maximum compact and occasional in fee.
Shell and Tube Condensers
One of the styles of condensers plays the system of rejecting warmth with the aid of using having a cylindrical shell including water tubes. In a shell and tube condenser, water is pumped thru the pipes even as refrigerant flows with inside the shell.
Installations of fins in pipes permits higher warmth switch. The shell-and-tube condensers are normally low in fee and smooth to maintain. The maximum not unusual place kind of shell and tube condensers is the horizontal shell kind. However, vertical shell and tube condensers are typically used with ammonia in massive capability structures in order that cleansing of the tubes is viable from the pinnacle even as the plant is running.
Q6) Explain quality and quantity of cooling water required
A6)
Cooling towers are a crucial thing of refrigeration systems. They are not unusual place in industries together with oil & gas, chemical processing, electricity plants, datacenters.
Water is the maximum not unusual place cooling medium utilized in cooling processes, because of its availability and excessive warmness capacity. These makes use of require massive quantities of water and frequently gift ability for water saving.
This financial savings bring about decrease water and sewer payments and reduced remedy costs. In the commercial marketplace there may be discovered 3 kinds of cooling towers: open circuit, closed circuit and as soon as thru machine.
Cooling towers may be air-cooled or water-cooled. Water-cooled cooling towers are extra not unusual place, because the cooling electricity of water is more potent than air.
Hybrid cooling towers have become increasingly more appealing for Datacenter cooling in critical Europe.
During low temperature months, air is used for cooling, whilst in excessive temperature months, water is used. The water intake is composed at the manager of the makeup water, the blow down water and the evaporated water quantities. These 3 waters decide the cycles of awareness that may be reached with inside the cooling tower.
Make – up = Blowdown + Evaporation loss
The mass stability of a cooling tower machine may be written because the following:
This equation doesn’t take account of the method leaks, the wind age and flow that are simply kinds of out of control blow down. Moreover, the cycles of awareness is a ratio of the awareness in suspended solids among the blow down water and the makeup water.
Cycles = 
Water cooling is a technique of warmth elimination from additives and commercial equipment. Evaporative cooling the use of water is regularly extra green than air cooling. Water is less expensive and non-toxic; however, it may include impurities and reason corrosion.
Water cooling is typically used for cooling vehicle inner combustion engines and strength stations.
Water coolers utilizing convective warmness switch are used internal excessive-quit non-public computer systems to decrease the temperature of CPUs.
Other makes use of consist of the cooling of lubricant oil in pumps; for cooling functions in warmness exchangers; for cooling homes in HVAC and in chillers.
Water is less expensive, non-toxic, and to be had over maximum of the earth's surface. Liquid cooling gives better thermal conductivity than air cooling.
Water has surprisingly excessive particular warmness capability amongst typically to be had drinks at room temperature and atmospheric stress permitting green warmness switch over distance with low fees of mass switch.
- Cooling water can be recycled thru a recirculating machine or utilized in an unmarried by skip once-thru cooling (OTC) machine.
- Water's excessive enthalpy of vaporization lets in the choice of green evaporative cooling to get rid of waste warmness in cooling towers or cooling ponds.
- Recirculating structures can be open in the event that they depend upon evaporative cooling or closed if warmness elimination is performed in warmness exchangers with negligible evaporative loss.
- A warmness exchanger or condenser can also additionally separate non-touch cooling water from a fluid being cooled, or touch cooling water can also additionally without delay impinge on gadgets like noticed blades in which segment distinction lets in clean separation.
Environmental guidelines emphasize the decreased concentrations of waste merchandise in non-touch cooling water
Q7) Write a short note on calculations for surface condenser
A7)
In a surface condenser vapor is brought into contact with a solid surface which is cooled to a temperature below the saturation temperature of the vapor at its prevailing partial pressure. The surface is usually in the form of a "nest" or "bundle" of metal tubes, the coolant flowing inside the tubes and the vapor condensing on the outer or "shell-side."
The Overall Heat Transfer Coefficient, U (based on the condensing surface area), may be expressed in terms of local coefficients, a, via the sum of thermal resistances:
From through vapor condensate tube wall fouling coolant
1/U = 1/αU + 1/αf + 
+ F +
Where D0, Di are the tube outer and inner diameters and λw is the thermal conductivity of the tube material.
Heat alternate in unmarried section flows is commonly impeded with the aid of using the presence of insulating boundary layers.
On condensation, however, the huge discount in quantity because the vapor turns to condensate consequences in an influx of vapor toward the floor; the warmth switch is impeded handiest with the aid of using a skinny movie of condensate at the floor.
As a result, the condensation warmth switch coefficient is commonly better than that at the liquid coolant aspect, the latter turning into the controlling process.
The thermal resistance, F, of fouling at the coolant aspect is consequently a vital consideration. Condensing warmth switch prices are normally orders of importance better than the prices for a fuel line at the shell aspect, so condensers do now no longer typically require prolonged floor tubing. In a few packages spirally grooved tubing has been used to useful resource drainage of the condensate movie and to growth inner warmth switch with the aid of using tabulating the coolant flow.
If no wetting may be maintained (e.g., with the aid of using surfactants), drop wise condensation occurs, lowering the regions of condensate movie and ensuing in a warmth switch coefficient a few 4 instances that of film wise condensation.
More importantly frictional strain losses because the vapor passes among the intently pitched tubes lowers the partial strain—and subsequently saturation temperature—lowering the warmth alternate using temperature difference. (See additionally Condensation and Condensers.)
The important goal in floor condenser layout is to offer identical get right of entry to of vapor to all of the floor. Early tries to offer standard warmth switch coefficients for the layout of steam condensers took no account of the exact format of the tube nest, e.g., HEI (1978).
Modern exercise is to version the proposed nest on pc to calculate thermal overall performance and to make sure that any non-condensable gases gift are extracted on the factor of lowest strain, e.g.,
Rhodes and Marshland (1993). Poorly designed nests can also additionally go through immoderate frictional strain losses and comprise areas in which the tubes are protected with the aid of using no condensable gases.
Q8) Explain Dalton’s law of partial pressure
A8)
Dalton’s regulation of partial pressures is a fuel line regulation which states that the entire strain exerted through a combination of gases is identical to the sum of the partial pressures exerted through every man or woman fuel line with inside the combination. For example, the entire strain exerted through a combination of gases A and B is identical to the sum of the man or woman partial pressures exerted through fuel line A and fuel line B (as illustrated below).
Dalton’s Law Formula
Dalton’s law of partial pressures can be mathematically expressed as follows:
Ptotal = ∑ni=1pi∑i=1npi (or) Ptotal = P1 + P2 + P3 + …. + Pn
Where,
- Ptotal is the total pressure exerted by the mixture of gases
- P1, P2,…, Pn are the partial pressures of the gases 1, 2,…, ‘n’ in the mixture of ‘n’ gases
Expressing Partial Pressures in Terms of Mole Fraction
The mole fraction of a specific gas in a mixture of gases is equal to the ratio of the partial pressure of that gas to the total pressure exerted by the gaseous mixture. This mole fraction can also be used to calculate the total number of moles of a constituent gas when the total number of moles in the mixture is known. Furthermore, the volume occupied by a specific gas in a mixture can also be calculated with this mole fraction with the help of the equation provided below.
Xi=Pi /Ptotal = Vi / Vtotal = n1 / ntotal
Where Xi is the mole fraction of a gas ‘i’ in a mixture of ‘n’ gases, ‘n’ denotes the number of moles, ‘P’ denotes pressure, and ‘V’ denotes volume.
Q9) A mixture of hydrogen gas and oxygen gas exerts a total pressure of 1.5 atm on the walls of its container. If the partial pressure of hydrogen is 1 atm, find the mole fraction of oxygen in the mixture.
A9)
Given, Phydrogen = 1 atm, Ptotal = 1.5 atm
Applying Dalton’s law formula, Ptotal = Phydrogen + Poxygen
Therefore, Poxygen = 0.5 atm
Now, the mole fraction of oxygen, Xoxygen = (Poxygen/Ptotal) = 0.5/1.5 = 0.33
Therefore, the mole fraction of oxygen in the mixture is 0.33
Q10) At a temperature of 300K, 30 liters of gas A kept under pressure of 1 atm and 15 liters of gas B kept under pressure of 2 atm is transferred into an empty 10L container. Calculate the total pressure inside the container and the partial pressures of gas A and gas B (Assume that A and B are ideal gases).
A10)
From the ideal gas equation, PV = nRT
Number of moles of gas A = (30L*1atm)/ (0.08206 atm.L.mol-1.K-1 * 300K) = 1.22 mol
Number of moles of gas B = (15*2atm)/ (0.08206 atm.L.mol-1.K-1 * 300K) = 1.22 mol
Total number of moles in the gaseous mixture = 2.44 mol
Total pressure inside the 10L container = Ptot = nRT/V
Ptot = (2.44mol*0.08206 atm.L.mol-1.K-1*300K)/10L = 6.006 atm
Therefore, the total pressure inside the 10 litre container is 6.006 atm
Mole fraction of gas A = mole fraction of gas B = (1.22 mol/2.44 mol) = 0.5
Therefore, partial pressure of gas A = Therefore, partial pressure of gas B = 0.5*6.006 = 3.003 atm
Thus, the partial pressures of gases A and B in the 10L container are both equal to 3.003 atm.
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Q11) Explain sources of air leakages and air removal
A11)
SOURCES OF AIR LEAKAGE IN CONDENSER:
Following are the manner thru which air is found in a condenser,
(i) Leakage thru packing glands and really small holes with inside the shell.
(ii) Leakage thru joints and vents from atmospheric alleviation valves and different accessories.
(iii) Dissolved gases or air in boiler feed water, which in the long run enters the condenser with exhaust steam.
EFFECT OF LEAKAGE AIR ON CONDENSER PERFORMANCE:
The presence of air with inside the condenser has the subsequent consequences on condenser operation Back stress (or exhaust stress) with inside the steam engine or turbine will increase and therefore work done reduces.
Thermal performance of the strength plant reduces.
For the equal absolute stress (partial pre. Of steam + partial pre. Of air), the partial stress of steam decreases with air infiltration. Saturation temperature decreases; latent heat (enthalpy of evaporation) will increase. So, condenser calls for large amount of cooling water. Air being a bad conductor of warmth, its presence with inside the condenser influences fee of warmth transfer.
Thus to fulfil the requirement, floor vicinity of tubes is to be increased. The Size of condenser will increase. Rate of steam condensation is reduced.
AIR PUMP:
Presence of air in condenser has awful consequences at the condenser operation. Air have to be absolutely extracted out the use of extraction pumps.
The pump can be of dry kind which eliminates best air, or moist kind which eliminates air, condensate and non-condensable gases.
Fig indicates the operating of Edward's reciprocating moist kind air pump (or air extractor). It has no suction valve as it's far there with inside the regular pumps. It is hooked up to the condenser.
When the piston is on the pinnacle of the barrel, the condensate and air from the condenser are accumulated with inside the conical part of the barrel.
On the downward stroke of the piston, partial vacuum is created above the piston on account that transport valve is saved closed. When the piston uncovers the ports at some stage in its similarly downward movement, the air and water vapor entrapped with inside the conical portion, rush into the barrel area above the piston thru those ports.
During go back journey (upward movement) of the piston, the above aggregate is compressed and stress rises. When stress exceeds the atmospheric stress, the transport valve opens.
The aggregate of air and water vapor escapes out to the recent well, over a weir. The weir continues enough head of water above the transport valve to save you air leakage into the pump barrel. The water sealed alleviation valve operates while the stress with inside the barrel exceeds atmospheric stress.
Q12) What is Condenser Vacuum?
A12)
The vacuum available with inside the condenser relies upon on tightness of valve joints, quantity of air infiltration and temperature of steam after condensation.
Vacuum will now no longer be uniform throughout. It is least on the air pump section, excessive in.
The frame of the condenser and nonetheless better at exhaust valve. The diploma of vacuum measured via way of means of the vacuum gauge established on condenser may be expressed with inside the following ways.
(i) By extra of atmospheric stress over the found vacuum: For instance 650 mm vacuum manner, atmospheric stress is 650 mm of Hg above the condenser stress.
(ii) By the share vacuum: It is the ratio of found vacuum to atmospheric stress. For instance, if the gauge reads 650 mm Hg, with the barometer analyzing of 750 mm Hg, the share vacuum 650/750 x 100 = 86.67%.
(iii) By absolutely the stress: It is the distinction among barometric analyzing and vacuum gauge analyzing.
The characteristic of condensers in steam electricity flora is to hold a low temperature. This is important to attain the most thermal performance from a given plant.
The lowest temperature attained relies upon the temperature of the circulating water which condenses the steam. When the steam expands to a stress under the atmospheric stress, it can't be exhausted into ecosystem and consequently it exhausts in a vessel that is at a decrease stress than that of the exhaust steam.
The exhaust steam is condensed with inside the vessel that is called condenser. The temperature of condensed steam, normally called condensate, leaving the condenser is better than that of the circulating water at inlet and the condensate is eliminated from the condenser with the aid of an extraction pump which discharges the condensate to the hot-properly from in which the boiler feed pump feeds it to the
Thus floor condensers offer each a low exhaust stress and restoration of the condensate, while jet condensers offer handiest the low exhaust stress; there can be greater intimate warmth trade among cooling water and the steam with a realistic drawback because of blending of the cooling water the condensate, which drawback is obviated in floor condensers.
With jet condensers, exhaust steam mixes with cooling water, so this cooling water ought to be sparkling and loose from dangerous impurities if the condensate is to be re-used for feeding into boiler.
Salt water may be used; accordingly all marine steam installations are geared up with floor condensers.
In big steam turbine installations jet condensers are impractical due to the fact there may be lack of condensate, the excessive electricity intake of jet condenser pumps and the primary price of needful air pumps.
Therefore, for contemporary-day steam electricity plant floor condensers are used. However, with reciprocating steam engines and slight length turbine units, the jet condensers are used particularly in which a considerable deliver of desirable water is available.
Q13) What are air ejectors?
A13)
A vacuum ejector, or actually ejector is a kind of vacuum pump, which produces vacuum via the Venturi effect.
In an ejector, a running fluid (liquid or gaseous) flows via a jet nozzle right into a tube that first narrows after which expands in cross-sectional area.
The fluid leaving the jet is flowing at an excessive pace which because of Bernoulli's precept consequences in it having low strain, therefore producing a vacuum.
The outer tube then narrows right into a blending phase wherein the excessive pace running fluid mixes with the fluid this is drawn in with the aid of using the vacuum, supplying sufficient pace for it to be ejected, the tube then usually expands with the intention to lower the speed of the ejected stream, permitting the strain to easily boom to the outside strain.
The electricity of the vacuum produced relies upon on the speed and form of the fluid jet and the form of the constriction and combining sections, however if a liquid is used because the running fluid the electricity of the vacuum produced is constrained with the aid of using the vapor strain of the liquid (for water, 3.2 kPa or forty six psi or 32 mbar at 25 °C or 77 °F).
If now no longer thinking about the supply of the running fluid, vacuum ejectors may be considerably greater compact than a self-powered vacuum pump of the equal capacity.
The reasonably-priced and easy water aspirator is typically utilized in chemistry and biology laboratories and includes a tee becoming connected to a faucet and has a hose barb at one side.
The waft of water passes via the instantly part of the tee, which has restrict on the intersection, wherein the hose barb is connected. The vacuum hose ought to be linked to this barb.
However, they're water-intensive, and relying on what the vacuum is getting used for (e.g. Solvent removal), they are able to violate environmental safety legal guidelines together with the RCRA with the aid of using blending doubtlessly dangerous chemical compounds into the water stream, then flushing them down a drain that frequently leads immediately to the municipal sewer.
Their use has reduced extremely as small electric powered vacuum pumps are a ways greater effective, environmentally safe, and feature emerge as greater affordable, however the unrivaled simplicity and reliability of this tool have induced it to stay famous for small labs or as a backup.
Another, a good deal large model of this tool is utilized in maritime operations as a tool to dewater (drain) regions in a deliver which have been flooded in emergency conditions.
Typically called an educator in those packages, that is desired over electric pumps because of their simplicity, compact length, and substantially mitigated threat of explosion with inside the occasion that flammable drinks and/or vapors are gift.
Additionally, in contrast to many mechanical pumps, they also can by skip particles because the educator has no transferring elements that may be fouled.
This makes an educator specifically beneficial in conditions wherein becoming a particles strainer to the suction port will gift greater problems than it resolves.
Sizes, waft ratings, and packages vary, along with educators which might be completely installed (usually utilized in very big areas, together with a deliver's major engine room), or transportable fashions that may be reduced into areas with the aid of using a rope and provided and tired via firefighting hoses.
Most are provided via a deliver's firefighting major, and transportable fashions also can be provided with the aid of using an emergency pump, supplied it may deliver enough waft to perform the educator.
Let’s discover how an Ejector works. Firstly, it's far really well worth noting that Ejectors also are called Educators, Surface Jet Pumps, and Velocity Spools.
Q14) Write a working of air ejectors
A14)
- Based upon Bernoulli’s Principle, as the speed of a fluid increases, its strain decreases, and vice versa.
- This is regularly known as the suction chamber of the Ejector.
- Where the strain on this area is decrease than the strain of the suction fluid linked to the Ejector side-inlet or ‘suction branch’, it will likely be entrained/sucked into the frame of the Ejector.
- The fluid streams then tour via the diffuser phase of the Ejector, in which pace is reduced due to the diverging geometry and strain is regained.
- Importantly, the low strain suction circulation stories a strain increase/compression, even as the cause circulation sees a lower in strain, as a number of its power has been used to ‘do work’ at the suction circulation.
- The resultant discharge strain is consequently someplace among the cause and suction pressures.
- Ejectors are pipeline established gadgets and may be synthetic in nearly any fabric to match the manner conditions.
- They have three connections; Motive, Suction and Discharge.
Q15) What are cooling towers?
A15)
A cooling tower is a warmness rejection tool that rejects waste warmness to the ecosystem thru the cooling of a coolant move, generally a water move to a decrease temperature.
Cooling towers may also both use the evaporation of water to take away method warmness and funky the operating fluid to close to the wet-bulb air temperature or, with inside the case of closed circuit cooling towers or dry cooling towers, depend entirely on air to chill the operating fluid to close to the dry-bulb air temperature the use of Common programs encompass cooling the circulating water utilized in oil refineries, petrochemical and different chemical flowers, thermal electricity stations, nuclear electricity stations and HVAC structures for cooling homes.
The category is primarily based totally at the form of air induction into the tower: the primary styles of cooling towers are herbal draft and triggered draft cooling towers.
Cooling towers range in length from small roof-pinnacle gadgets to very huge hyperboloid systems (as with inside the adjoining image) that may be as much as 2 hundred meters (660 ft) tall and one hundred meters (330 ft) in diameter, or square systems that may be over forty meters (a hundred thirty ft) tall and eighty meters (260 ft) long.
Hyperboloid cooling towers are regularly related to nuclear electricity flowers, even though they're extensively utilized in a few coal-fired flowers and to a point in a few huge chemical and different business flowers.
Although those huge towers are very prominent, the good sized majority of cooling towers are a good deal smaller, inclusive of many gadgets established on or close to homes to discharge warmness from air conditioning.
This reduces the returned pressure, which in flip reduces the steam consumption, and as a consequence the gasoline consumption, at the same time as on the identical time growing electricity and recycling boiler-water.
However the condensers require an adequate deliver of cooling water, without which they're impractical. While water utilization isn't always an trouble with marine engines, it paperwork a substantial difficulty for plenty land-primarily based totally structures.
By the flip of the twentieth century, numerous evaporative strategies of recycling cooling water have been in use in regions missing a longtime water deliver, in addition to in city places in which municipal water mains might not be of enough deliver; dependable in instances of demand; or in any other case ok to fulfill cooling needs. In regions with to be had land, the structures took the shape of cooling ponds; in regions with confined land, including in cities, they took the shape of cooling towers.
These early towers have been placed both at the rooftops of homes or as free-status systems, provided with air with the aid of using fanatics or counting on herbal airflow.
At the pinnacle is a fixed of dispensing troughs, to which the water from the condenser have to be pumped; from those it trickles down over "mats" fabricated from wood slats or woven cord screens, which fill the gap with inside the tower.
Unit - 6
Steam condensers
Q1) What is steam condenser?
A1)
Steam condensers
A steam condenser is a closed vessel-kind warmth exchanger implemented to transform low-stress exhaust steam from the turbine to water.
A steam condenser is a mechanical tool hired to condense exhaust steam of the turbine into the water. It conducts this procedure with the assist of cooling water that circulates interior it from the cooling tower. The stress inside a steam condenser is held under the atmospheric stress to decorate efficiency. It is generally used to decrease the backpressure of the exhaust on the turbine quit.
Functions of the Steam Condenser
The reason of the usage of a steam condenser is: supporting maintain the stress low (under atmospheric stress) on the steam turbine quit to get most feasible strength and decrease the unique steam intake of an electricity plant.
Offering natural feed water to and from the new nicely.
The water is once more pumped to the boiler the usage of a boiler feed pump. Elevating the warmth switch fee with the aid of using casting off different non-condensable gases from the exiting steam.
Q2) Explain various Steam Condenser Parts
A2)
Steam Condenser Parts
The additives required to perform a steam condenser are as follows.
Condenser
It is used to condense the steam.
The steam with low stress offers its warmth to the coolant (right here water from the cooling tower), and it converts into the water thru the condensation procedure.
Condensate Extraction Pump
A Condensate Extraction Pump (CEP) is a pump mounted among the condenser and the new nicely to switch the condensate from the condenser to the new nicely. Hot Well It is a pit among the condenser and the boiler. It takes the condensate with the aid of using condensate pump from the condenser. The feed water is carried from the new nicely to the boiler.
Boiler Feed Pump
It is a pump positioned among the new nicely and boiler to supply the feed water from the new nicely to the boiler. This is achieved with the aid of using growing the condensate stress above boiler stress.
Air Extraction Pump
It is a pump applied to extract or take away the air from the steam condenser. Cooling Tower It is a tower containing bloodless water, and this water is furnished to flow into within the condenser to chill the steam. Cooling Water Pump It is a pump mounted among the condenser and the cooling tower. It circulates the coolant inside the condenser.
Q3) Write a short note on principle of steam condenser.
A3)
Steam Condenser Working Principle
In this section, we are able to supply a simple description of the way a steam condenser works. A glide of cooling water is constantly circulating from the condenser interior a steam condenser to the cooling tower and the cooling tower to the condenser.
When low-stress exhaust steam leaves the turbine and passes thru the condenser, it loses the warmth and condenses into water. The circulating cooling water plays the extraction of the warmth from the steam.
Two forms of gadgets are mounted at the condenser: the condensate extraction pump and the air extraction pump.
Therefore, whilst the steam condenses into water, it re-circulates once more to the steam generator with the assist of a condensate extraction pump. Using the air extraction pump, a vacuum (the stress under the atmospheric stress) is created within the condenser in order that cooling water can flow into effortlessly and additionally the condensate glide may be stabilized.
Due to the low stress within the condenser, the air enters the gadget in order that the condenser is packed with a combination of water, air, and steam.
Types & Classification of condensers
Three Main and Different Types of Condensers.
- Air-cooled condenser
- Natural Convection
- Forced Convection
- Water-cooled condenser
- Double Tube Shell and Coil Condenser
- Shell and Tube Condenser
Evaporative Condenser
Condensers primarily based totally at the condensing medium used to eliminate the warmth from the system, consist of 3 one-of-a-kind kinds. None of those 3 one-of-a-kind styles of condensers has mainly no blessings over the alternative. Depending at the situation, everyone have to be used appropriately. We are going to tricky at the features of those 3 condenser kinds with inside the following.
Air-cooled Condenser
Condensers of this kind use air because the outside fluid to reject the warmth from the system. Air-cooled condensers typically have copper coils in which refrigerant flows in. But this isn't always the complete story; this kind is subcategorized into subsets: herbal convection and compelled convection.
Q4) What do you mean by natural convention?
A4)
Natural Convection
In this kind of condenser, air involves touch with heat coils, soaking up the warmth of refrigerant in the coils, therefore the temper
Natural Convection
In this kind of condenser, air involves touch with heat coils, soaking up the warmth of refrigerant in the coils, therefore the temperature of air increases. As the nice and cozy air is lighter, it is going up and the bloodless air replaces and once more the bloodless air comes to the touch heat coils to reject the warmth. This herbal cycle maintains till the refrigerant loses its warmth. Since the glide charge of air is small and the radiation warmth switch is likewise now no longer very high, the blended warmth switch coefficient in those condensers is small.
As a result, an especially massive condensing floor is needed to reject a given quantity of warmth. Hence those styles of condensers are used for small capability refrigeration structures like family fridges and freezers.
Forced Convection
One of the alternative styles of condensers is compelled-convection. A fan or a blower does play the maximum essential position in casting off warmth from the refrigerant in the coils. The fan blows the air into the finned coils. A critical tip needs to be referred to right here and its miles that the fins of compelled convection condenser are positioned tightly subsequent to every other; so, if the dirt and dust fill the mild area among the fins, the air flowing and warmth rejection faces huge trouble.
Forced convection kind condensers are usually utilized in window air conditioners, water coolers, and packaged air con plants.
Water-cooled condenser
As it is able to be guessed, this kind of condenser makes use of water as fluid to eliminate warmth from the refrigerant. It is apparent that water-cooled condensers are used in which we've got an ok deliver of water. This kind, itself has 3 one-of-a-kind kinds: See All Water-Cooled Condenser for Sale
Q5) What is double tube?
A5)
Double Tube
Double tube condensers have a tube of water inner a massive refrigerant tube. The water absorbs maximum of the refrigerant warmth, however because the refrigerant tube is in touch with the herbal move of air, a part of the cooling system is on herbal convection. Although double-tube condensers usually had been used with inside the past, the massive wide variety of gaskets and flanges utilized in those warmth exchangers ends in protection problems.
Shell and Coil Condensers
In a shell-and-coil condenser, a welded shell consists of a coil of finned water tubing. In this kind of water-cooled condenser, the new refrigerant flows with inside the shell even as the cooling water circulates in the coils and condenses the refrigerant. It is normally maximum compact and occasional in fee.
Shell and Tube Condensers
One of the styles of condensers plays the system of rejecting warmth with the aid of using having a cylindrical shell including water tubes. In a shell and tube condenser, water is pumped thru the pipes even as refrigerant flows with inside the shell.
Installations of fins in pipes permits higher warmth switch. The shell-and-tube condensers are normally low in fee and smooth to maintain. The maximum not unusual place kind of shell and tube condensers is the horizontal shell kind. However, vertical shell and tube condensers are typically used with ammonia in massive capability structures in order that cleansing of the tubes is viable from the pinnacle even as the plant is running.
Q6) Explain quality and quantity of cooling water required
A6)
Cooling towers are a crucial thing of refrigeration systems. They are not unusual place in industries together with oil & gas, chemical processing, electricity plants, datacenters.
Water is the maximum not unusual place cooling medium utilized in cooling processes, because of its availability and excessive warmness capacity. These makes use of require massive quantities of water and frequently gift ability for water saving.
This financial savings bring about decrease water and sewer payments and reduced remedy costs. In the commercial marketplace there may be discovered 3 kinds of cooling towers: open circuit, closed circuit and as soon as thru machine.
Cooling towers may be air-cooled or water-cooled. Water-cooled cooling towers are extra not unusual place, because the cooling electricity of water is more potent than air.
Hybrid cooling towers have become increasingly more appealing for Datacenter cooling in critical Europe.
During low temperature months, air is used for cooling, whilst in excessive temperature months, water is used. The water intake is composed at the manager of the makeup water, the blow down water and the evaporated water quantities. These 3 waters decide the cycles of awareness that may be reached with inside the cooling tower.
Make – up = Blowdown + Evaporation loss
The mass stability of a cooling tower machine may be written because the following:
This equation doesn’t take account of the method leaks, the wind age and flow that are simply kinds of out of control blow down. Moreover, the cycles of awareness is a ratio of the awareness in suspended solids among the blow down water and the makeup water.
Cycles = 
Water cooling is a technique of warmth elimination from additives and commercial equipment. Evaporative cooling the use of water is regularly extra green than air cooling. Water is less expensive and non-toxic; however, it may include impurities and reason corrosion.
Water cooling is typically used for cooling vehicle inner combustion engines and strength stations.
Water coolers utilizing convective warmness switch are used internal excessive-quit non-public computer systems to decrease the temperature of CPUs.
Other makes use of consist of the cooling of lubricant oil in pumps; for cooling functions in warmness exchangers; for cooling homes in HVAC and in chillers.
Water is less expensive, non-toxic, and to be had over maximum of the earth's surface. Liquid cooling gives better thermal conductivity than air cooling.
Water has surprisingly excessive particular warmness capability amongst typically to be had drinks at room temperature and atmospheric stress permitting green warmness switch over distance with low fees of mass switch.
- Cooling water can be recycled thru a recirculating machine or utilized in an unmarried by skip once-thru cooling (OTC) machine.
- Water's excessive enthalpy of vaporization lets in the choice of green evaporative cooling to get rid of waste warmness in cooling towers or cooling ponds.
- Recirculating structures can be open in the event that they depend upon evaporative cooling or closed if warmness elimination is performed in warmness exchangers with negligible evaporative loss.
- A warmness exchanger or condenser can also additionally separate non-touch cooling water from a fluid being cooled, or touch cooling water can also additionally without delay impinge on gadgets like noticed blades in which segment distinction lets in clean separation.
Environmental guidelines emphasize the decreased concentrations of waste merchandise in non-touch cooling water
Q7) Write a short note on calculations for surface condenser
A7)
In a surface condenser vapor is brought into contact with a solid surface which is cooled to a temperature below the saturation temperature of the vapor at its prevailing partial pressure. The surface is usually in the form of a "nest" or "bundle" of metal tubes, the coolant flowing inside the tubes and the vapor condensing on the outer or "shell-side."
The Overall Heat Transfer Coefficient, U (based on the condensing surface area), may be expressed in terms of local coefficients, a, via the sum of thermal resistances:
From through vapor condensate tube wall fouling coolant
1/U = 1/αU + 1/αf + 
+ F +
Where D0, Di are the tube outer and inner diameters and λw is the thermal conductivity of the tube material.
Heat alternate in unmarried section flows is commonly impeded with the aid of using the presence of insulating boundary layers.
On condensation, however, the huge discount in quantity because the vapor turns to condensate consequences in an influx of vapor toward the floor; the warmth switch is impeded handiest with the aid of using a skinny movie of condensate at the floor.
As a result, the condensation warmth switch coefficient is commonly better than that at the liquid coolant aspect, the latter turning into the controlling process.
The thermal resistance, F, of fouling at the coolant aspect is consequently a vital consideration. Condensing warmth switch prices are normally orders of importance better than the prices for a fuel line at the shell aspect, so condensers do now no longer typically require prolonged floor tubing. In a few packages spirally grooved tubing has been used to useful resource drainage of the condensate movie and to growth inner warmth switch with the aid of using tabulating the coolant flow.
If no wetting may be maintained (e.g., with the aid of using surfactants), drop wise condensation occurs, lowering the regions of condensate movie and ensuing in a warmth switch coefficient a few 4 instances that of film wise condensation.
More importantly frictional strain losses because the vapor passes among the intently pitched tubes lowers the partial strain—and subsequently saturation temperature—lowering the warmth alternate using temperature difference. (See additionally Condensation and Condensers.)
The important goal in floor condenser layout is to offer identical get right of entry to of vapor to all of the floor. Early tries to offer standard warmth switch coefficients for the layout of steam condensers took no account of the exact format of the tube nest, e.g., HEI (1978).
Modern exercise is to version the proposed nest on pc to calculate thermal overall performance and to make sure that any non-condensable gases gift are extracted on the factor of lowest strain, e.g.,
Rhodes and Marshland (1993). Poorly designed nests can also additionally go through immoderate frictional strain losses and comprise areas in which the tubes are protected with the aid of using no condensable gases.
Q8) Explain Dalton’s law of partial pressure
A8)
Dalton’s regulation of partial pressures is a fuel line regulation which states that the entire strain exerted through a combination of gases is identical to the sum of the partial pressures exerted through every man or woman fuel line with inside the combination. For example, the entire strain exerted through a combination of gases A and B is identical to the sum of the man or woman partial pressures exerted through fuel line A and fuel line B (as illustrated below).
Dalton’s Law Formula
Dalton’s law of partial pressures can be mathematically expressed as follows:
Ptotal = ∑ni=1pi∑i=1npi (or) Ptotal = P1 + P2 + P3 + …. + Pn
Where,
- Ptotal is the total pressure exerted by the mixture of gases
- P1, P2,…, Pn are the partial pressures of the gases 1, 2,…, ‘n’ in the mixture of ‘n’ gases
Expressing Partial Pressures in Terms of Mole Fraction
The mole fraction of a specific gas in a mixture of gases is equal to the ratio of the partial pressure of that gas to the total pressure exerted by the gaseous mixture. This mole fraction can also be used to calculate the total number of moles of a constituent gas when the total number of moles in the mixture is known. Furthermore, the volume occupied by a specific gas in a mixture can also be calculated with this mole fraction with the help of the equation provided below.
Xi=Pi /Ptotal = Vi / Vtotal = n1 / ntotal
Where Xi is the mole fraction of a gas ‘i’ in a mixture of ‘n’ gases, ‘n’ denotes the number of moles, ‘P’ denotes pressure, and ‘V’ denotes volume.
Q9) A mixture of hydrogen gas and oxygen gas exerts a total pressure of 1.5 atm on the walls of its container. If the partial pressure of hydrogen is 1 atm, find the mole fraction of oxygen in the mixture.
A9)
Given, Phydrogen = 1 atm, Ptotal = 1.5 atm
Applying Dalton’s law formula, Ptotal = Phydrogen + Poxygen
Therefore, Poxygen = 0.5 atm
Now, the mole fraction of oxygen, Xoxygen = (Poxygen/Ptotal) = 0.5/1.5 = 0.33
Therefore, the mole fraction of oxygen in the mixture is 0.33
Q10) At a temperature of 300K, 30 liters of gas A kept under pressure of 1 atm and 15 liters of gas B kept under pressure of 2 atm is transferred into an empty 10L container. Calculate the total pressure inside the container and the partial pressures of gas A and gas B (Assume that A and B are ideal gases).
A10)
From the ideal gas equation, PV = nRT
Number of moles of gas A = (30L*1atm)/ (0.08206 atm.L.mol-1.K-1 * 300K) = 1.22 mol
Number of moles of gas B = (15*2atm)/ (0.08206 atm.L.mol-1.K-1 * 300K) = 1.22 mol
Total number of moles in the gaseous mixture = 2.44 mol
Total pressure inside the 10L container = Ptot = nRT/V
Ptot = (2.44mol*0.08206 atm.L.mol-1.K-1*300K)/10L = 6.006 atm
Therefore, the total pressure inside the 10 litre container is 6.006 atm
Mole fraction of gas A = mole fraction of gas B = (1.22 mol/2.44 mol) = 0.5
Therefore, partial pressure of gas A = Therefore, partial pressure of gas B = 0.5*6.006 = 3.003 atm
Thus, the partial pressures of gases A and B in the 10L container are both equal to 3.003 atm.
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Q11) Explain sources of air leakages and air removal
A11)
SOURCES OF AIR LEAKAGE IN CONDENSER:
Following are the manner thru which air is found in a condenser,
(i) Leakage thru packing glands and really small holes with inside the shell.
(ii) Leakage thru joints and vents from atmospheric alleviation valves and different accessories.
(iii) Dissolved gases or air in boiler feed water, which in the long run enters the condenser with exhaust steam.
EFFECT OF LEAKAGE AIR ON CONDENSER PERFORMANCE:
The presence of air with inside the condenser has the subsequent consequences on condenser operation Back stress (or exhaust stress) with inside the steam engine or turbine will increase and therefore work done reduces.
Thermal performance of the strength plant reduces.
For the equal absolute stress (partial pre. Of steam + partial pre. Of air), the partial stress of steam decreases with air infiltration. Saturation temperature decreases; latent heat (enthalpy of evaporation) will increase. So, condenser calls for large amount of cooling water. Air being a bad conductor of warmth, its presence with inside the condenser influences fee of warmth transfer.
Thus to fulfil the requirement, floor vicinity of tubes is to be increased. The Size of condenser will increase. Rate of steam condensation is reduced.
AIR PUMP:
Presence of air in condenser has awful consequences at the condenser operation. Air have to be absolutely extracted out the use of extraction pumps.
The pump can be of dry kind which eliminates best air, or moist kind which eliminates air, condensate and non-condensable gases.
Fig indicates the operating of Edward's reciprocating moist kind air pump (or air extractor). It has no suction valve as it's far there with inside the regular pumps. It is hooked up to the condenser.
When the piston is on the pinnacle of the barrel, the condensate and air from the condenser are accumulated with inside the conical part of the barrel.
On the downward stroke of the piston, partial vacuum is created above the piston on account that transport valve is saved closed. When the piston uncovers the ports at some stage in its similarly downward movement, the air and water vapor entrapped with inside the conical portion, rush into the barrel area above the piston thru those ports.
During go back journey (upward movement) of the piston, the above aggregate is compressed and stress rises. When stress exceeds the atmospheric stress, the transport valve opens.
The aggregate of air and water vapor escapes out to the recent well, over a weir. The weir continues enough head of water above the transport valve to save you air leakage into the pump barrel. The water sealed alleviation valve operates while the stress with inside the barrel exceeds atmospheric stress.
Q12) What is Condenser Vacuum?
A12)
The vacuum available with inside the condenser relies upon on tightness of valve joints, quantity of air infiltration and temperature of steam after condensation.
Vacuum will now no longer be uniform throughout. It is least on the air pump section, excessive in.
The frame of the condenser and nonetheless better at exhaust valve. The diploma of vacuum measured via way of means of the vacuum gauge established on condenser may be expressed with inside the following ways.
(i) By extra of atmospheric stress over the found vacuum: For instance 650 mm vacuum manner, atmospheric stress is 650 mm of Hg above the condenser stress.
(ii) By the share vacuum: It is the ratio of found vacuum to atmospheric stress. For instance, if the gauge reads 650 mm Hg, with the barometer analyzing of 750 mm Hg, the share vacuum 650/750 x 100 = 86.67%.
(iii) By absolutely the stress: It is the distinction among barometric analyzing and vacuum gauge analyzing.
The characteristic of condensers in steam electricity flora is to hold a low temperature. This is important to attain the most thermal performance from a given plant.
The lowest temperature attained relies upon the temperature of the circulating water which condenses the steam. When the steam expands to a stress under the atmospheric stress, it can't be exhausted into ecosystem and consequently it exhausts in a vessel that is at a decrease stress than that of the exhaust steam.
The exhaust steam is condensed with inside the vessel that is called condenser. The temperature of condensed steam, normally called condensate, leaving the condenser is better than that of the circulating water at inlet and the condensate is eliminated from the condenser with the aid of an extraction pump which discharges the condensate to the hot-properly from in which the boiler feed pump feeds it to the
Thus floor condensers offer each a low exhaust stress and restoration of the condensate, while jet condensers offer handiest the low exhaust stress; there can be greater intimate warmth trade among cooling water and the steam with a realistic drawback because of blending of the cooling water the condensate, which drawback is obviated in floor condensers.
With jet condensers, exhaust steam mixes with cooling water, so this cooling water ought to be sparkling and loose from dangerous impurities if the condensate is to be re-used for feeding into boiler.
Salt water may be used; accordingly all marine steam installations are geared up with floor condensers.
In big steam turbine installations jet condensers are impractical due to the fact there may be lack of condensate, the excessive electricity intake of jet condenser pumps and the primary price of needful air pumps.
Therefore, for contemporary-day steam electricity plant floor condensers are used. However, with reciprocating steam engines and slight length turbine units, the jet condensers are used particularly in which a considerable deliver of desirable water is available.
Q13) What are air ejectors?
A13)
A vacuum ejector, or actually ejector is a kind of vacuum pump, which produces vacuum via the Venturi effect.
In an ejector, a running fluid (liquid or gaseous) flows via a jet nozzle right into a tube that first narrows after which expands in cross-sectional area.
The fluid leaving the jet is flowing at an excessive pace which because of Bernoulli's precept consequences in it having low strain, therefore producing a vacuum.
The outer tube then narrows right into a blending phase wherein the excessive pace running fluid mixes with the fluid this is drawn in with the aid of using the vacuum, supplying sufficient pace for it to be ejected, the tube then usually expands with the intention to lower the speed of the ejected stream, permitting the strain to easily boom to the outside strain.
The electricity of the vacuum produced relies upon on the speed and form of the fluid jet and the form of the constriction and combining sections, however if a liquid is used because the running fluid the electricity of the vacuum produced is constrained with the aid of using the vapor strain of the liquid (for water, 3.2 kPa or forty six psi or 32 mbar at 25 °C or 77 °F).
If now no longer thinking about the supply of the running fluid, vacuum ejectors may be considerably greater compact than a self-powered vacuum pump of the equal capacity.
The reasonably-priced and easy water aspirator is typically utilized in chemistry and biology laboratories and includes a tee becoming connected to a faucet and has a hose barb at one side.
The waft of water passes via the instantly part of the tee, which has restrict on the intersection, wherein the hose barb is connected. The vacuum hose ought to be linked to this barb.
However, they're water-intensive, and relying on what the vacuum is getting used for (e.g. Solvent removal), they are able to violate environmental safety legal guidelines together with the RCRA with the aid of using blending doubtlessly dangerous chemical compounds into the water stream, then flushing them down a drain that frequently leads immediately to the municipal sewer.
Their use has reduced extremely as small electric powered vacuum pumps are a ways greater effective, environmentally safe, and feature emerge as greater affordable, however the unrivaled simplicity and reliability of this tool have induced it to stay famous for small labs or as a backup.
Another, a good deal large model of this tool is utilized in maritime operations as a tool to dewater (drain) regions in a deliver which have been flooded in emergency conditions.
Typically called an educator in those packages, that is desired over electric pumps because of their simplicity, compact length, and substantially mitigated threat of explosion with inside the occasion that flammable drinks and/or vapors are gift.
Additionally, in contrast to many mechanical pumps, they also can by skip particles because the educator has no transferring elements that may be fouled.
This makes an educator specifically beneficial in conditions wherein becoming a particles strainer to the suction port will gift greater problems than it resolves.
Sizes, waft ratings, and packages vary, along with educators which might be completely installed (usually utilized in very big areas, together with a deliver's major engine room), or transportable fashions that may be reduced into areas with the aid of using a rope and provided and tired via firefighting hoses.
Most are provided via a deliver's firefighting major, and transportable fashions also can be provided with the aid of using an emergency pump, supplied it may deliver enough waft to perform the educator.
Let’s discover how an Ejector works. Firstly, it's far really well worth noting that Ejectors also are called Educators, Surface Jet Pumps, and Velocity Spools.
Q14) Write a working of air ejectors
A14)
- Based upon Bernoulli’s Principle, as the speed of a fluid increases, its strain decreases, and vice versa.
- This is regularly known as the suction chamber of the Ejector.
- Where the strain on this area is decrease than the strain of the suction fluid linked to the Ejector side-inlet or ‘suction branch’, it will likely be entrained/sucked into the frame of the Ejector.
- The fluid streams then tour via the diffuser phase of the Ejector, in which pace is reduced due to the diverging geometry and strain is regained.
- Importantly, the low strain suction circulation stories a strain increase/compression, even as the cause circulation sees a lower in strain, as a number of its power has been used to ‘do work’ at the suction circulation.
- The resultant discharge strain is consequently someplace among the cause and suction pressures.
- Ejectors are pipeline established gadgets and may be synthetic in nearly any fabric to match the manner conditions.
- They have three connections; Motive, Suction and Discharge.
Q15) What are cooling towers?
A15)
A cooling tower is a warmness rejection tool that rejects waste warmness to the ecosystem thru the cooling of a coolant move, generally a water move to a decrease temperature.
Cooling towers may also both use the evaporation of water to take away method warmness and funky the operating fluid to close to the wet-bulb air temperature or, with inside the case of closed circuit cooling towers or dry cooling towers, depend entirely on air to chill the operating fluid to close to the dry-bulb air temperature the use of Common programs encompass cooling the circulating water utilized in oil refineries, petrochemical and different chemical flowers, thermal electricity stations, nuclear electricity stations and HVAC structures for cooling homes.
The category is primarily based totally at the form of air induction into the tower: the primary styles of cooling towers are herbal draft and triggered draft cooling towers.
Cooling towers range in length from small roof-pinnacle gadgets to very huge hyperboloid systems (as with inside the adjoining image) that may be as much as 2 hundred meters (660 ft) tall and one hundred meters (330 ft) in diameter, or square systems that may be over forty meters (a hundred thirty ft) tall and eighty meters (260 ft) long.
Hyperboloid cooling towers are regularly related to nuclear electricity flowers, even though they're extensively utilized in a few coal-fired flowers and to a point in a few huge chemical and different business flowers.
Although those huge towers are very prominent, the good sized majority of cooling towers are a good deal smaller, inclusive of many gadgets established on or close to homes to discharge warmness from air conditioning.
This reduces the returned pressure, which in flip reduces the steam consumption, and as a consequence the gasoline consumption, at the same time as on the identical time growing electricity and recycling boiler-water.
However the condensers require an adequate deliver of cooling water, without which they're impractical. While water utilization isn't always an trouble with marine engines, it paperwork a substantial difficulty for plenty land-primarily based totally structures.
By the flip of the twentieth century, numerous evaporative strategies of recycling cooling water have been in use in regions missing a longtime water deliver, in addition to in city places in which municipal water mains might not be of enough deliver; dependable in instances of demand; or in any other case ok to fulfill cooling needs. In regions with to be had land, the structures took the shape of cooling ponds; in regions with confined land, including in cities, they took the shape of cooling towers.
These early towers have been placed both at the rooftops of homes or as free-status systems, provided with air with the aid of using fanatics or counting on herbal airflow.
At the pinnacle is a fixed of dispensing troughs, to which the water from the condenser have to be pumped; from those it trickles down over "mats" fabricated from wood slats or woven cord screens, which fill the gap with inside the tower.
Unit - 6
Unit - 6
Steam condensers
Q1) What is steam condenser?
A1)
Steam condensers
A steam condenser is a closed vessel-kind warmth exchanger implemented to transform low-stress exhaust steam from the turbine to water.
A steam condenser is a mechanical tool hired to condense exhaust steam of the turbine into the water. It conducts this procedure with the assist of cooling water that circulates interior it from the cooling tower. The stress inside a steam condenser is held under the atmospheric stress to decorate efficiency. It is generally used to decrease the backpressure of the exhaust on the turbine quit.
Functions of the Steam Condenser
The reason of the usage of a steam condenser is: supporting maintain the stress low (under atmospheric stress) on the steam turbine quit to get most feasible strength and decrease the unique steam intake of an electricity plant.
Offering natural feed water to and from the new nicely.
The water is once more pumped to the boiler the usage of a boiler feed pump. Elevating the warmth switch fee with the aid of using casting off different non-condensable gases from the exiting steam.
Q2) Explain various Steam Condenser Parts
A2)
Steam Condenser Parts
The additives required to perform a steam condenser are as follows.
Condenser
It is used to condense the steam.
The steam with low stress offers its warmth to the coolant (right here water from the cooling tower), and it converts into the water thru the condensation procedure.
Condensate Extraction Pump
A Condensate Extraction Pump (CEP) is a pump mounted among the condenser and the new nicely to switch the condensate from the condenser to the new nicely. Hot Well It is a pit among the condenser and the boiler. It takes the condensate with the aid of using condensate pump from the condenser. The feed water is carried from the new nicely to the boiler.
Boiler Feed Pump
It is a pump positioned among the new nicely and boiler to supply the feed water from the new nicely to the boiler. This is achieved with the aid of using growing the condensate stress above boiler stress.
Air Extraction Pump
It is a pump applied to extract or take away the air from the steam condenser. Cooling Tower It is a tower containing bloodless water, and this water is furnished to flow into within the condenser to chill the steam. Cooling Water Pump It is a pump mounted among the condenser and the cooling tower. It circulates the coolant inside the condenser.
Q3) Write a short note on principle of steam condenser.
A3)
Steam Condenser Working Principle
In this section, we are able to supply a simple description of the way a steam condenser works. A glide of cooling water is constantly circulating from the condenser interior a steam condenser to the cooling tower and the cooling tower to the condenser.
When low-stress exhaust steam leaves the turbine and passes thru the condenser, it loses the warmth and condenses into water. The circulating cooling water plays the extraction of the warmth from the steam.
Two forms of gadgets are mounted at the condenser: the condensate extraction pump and the air extraction pump.
Therefore, whilst the steam condenses into water, it re-circulates once more to the steam generator with the assist of a condensate extraction pump. Using the air extraction pump, a vacuum (the stress under the atmospheric stress) is created within the condenser in order that cooling water can flow into effortlessly and additionally the condensate glide may be stabilized.
Due to the low stress within the condenser, the air enters the gadget in order that the condenser is packed with a combination of water, air, and steam.
Types & Classification of condensers
Three Main and Different Types of Condensers.
- Air-cooled condenser
- Natural Convection
- Forced Convection
- Water-cooled condenser
- Double Tube Shell and Coil Condenser
- Shell and Tube Condenser
Evaporative Condenser
Condensers primarily based totally at the condensing medium used to eliminate the warmth from the system, consist of 3 one-of-a-kind kinds. None of those 3 one-of-a-kind styles of condensers has mainly no blessings over the alternative. Depending at the situation, everyone have to be used appropriately. We are going to tricky at the features of those 3 condenser kinds with inside the following.
Air-cooled Condenser
Condensers of this kind use air because the outside fluid to reject the warmth from the system. Air-cooled condensers typically have copper coils in which refrigerant flows in. But this isn't always the complete story; this kind is subcategorized into subsets: herbal convection and compelled convection.
Q4) What do you mean by natural convention?
A4)
Natural Convection
In this kind of condenser, air involves touch with heat coils, soaking up the warmth of refrigerant in the coils, therefore the temper
Natural Convection
In this kind of condenser, air involves touch with heat coils, soaking up the warmth of refrigerant in the coils, therefore the temperature of air increases. As the nice and cozy air is lighter, it is going up and the bloodless air replaces and once more the bloodless air comes to the touch heat coils to reject the warmth. This herbal cycle maintains till the refrigerant loses its warmth. Since the glide charge of air is small and the radiation warmth switch is likewise now no longer very high, the blended warmth switch coefficient in those condensers is small.
As a result, an especially massive condensing floor is needed to reject a given quantity of warmth. Hence those styles of condensers are used for small capability refrigeration structures like family fridges and freezers.
Forced Convection
One of the alternative styles of condensers is compelled-convection. A fan or a blower does play the maximum essential position in casting off warmth from the refrigerant in the coils. The fan blows the air into the finned coils. A critical tip needs to be referred to right here and its miles that the fins of compelled convection condenser are positioned tightly subsequent to every other; so, if the dirt and dust fill the mild area among the fins, the air flowing and warmth rejection faces huge trouble.
Forced convection kind condensers are usually utilized in window air conditioners, water coolers, and packaged air con plants.
Water-cooled condenser
As it is able to be guessed, this kind of condenser makes use of water as fluid to eliminate warmth from the refrigerant. It is apparent that water-cooled condensers are used in which we've got an ok deliver of water. This kind, itself has 3 one-of-a-kind kinds: See All Water-Cooled Condenser for Sale
Q5) What is double tube?
A5)
Double Tube
Double tube condensers have a tube of water inner a massive refrigerant tube. The water absorbs maximum of the refrigerant warmth, however because the refrigerant tube is in touch with the herbal move of air, a part of the cooling system is on herbal convection. Although double-tube condensers usually had been used with inside the past, the massive wide variety of gaskets and flanges utilized in those warmth exchangers ends in protection problems.
Shell and Coil Condensers
In a shell-and-coil condenser, a welded shell consists of a coil of finned water tubing. In this kind of water-cooled condenser, the new refrigerant flows with inside the shell even as the cooling water circulates in the coils and condenses the refrigerant. It is normally maximum compact and occasional in fee.
Shell and Tube Condensers
One of the styles of condensers plays the system of rejecting warmth with the aid of using having a cylindrical shell including water tubes. In a shell and tube condenser, water is pumped thru the pipes even as refrigerant flows with inside the shell.
Installations of fins in pipes permits higher warmth switch. The shell-and-tube condensers are normally low in fee and smooth to maintain. The maximum not unusual place kind of shell and tube condensers is the horizontal shell kind. However, vertical shell and tube condensers are typically used with ammonia in massive capability structures in order that cleansing of the tubes is viable from the pinnacle even as the plant is running.
Q6) Explain quality and quantity of cooling water required
A6)
Cooling towers are a crucial thing of refrigeration systems. They are not unusual place in industries together with oil & gas, chemical processing, electricity plants, datacenters.
Water is the maximum not unusual place cooling medium utilized in cooling processes, because of its availability and excessive warmness capacity. These makes use of require massive quantities of water and frequently gift ability for water saving.
This financial savings bring about decrease water and sewer payments and reduced remedy costs. In the commercial marketplace there may be discovered 3 kinds of cooling towers: open circuit, closed circuit and as soon as thru machine.
Cooling towers may be air-cooled or water-cooled. Water-cooled cooling towers are extra not unusual place, because the cooling electricity of water is more potent than air.
Hybrid cooling towers have become increasingly more appealing for Datacenter cooling in critical Europe.
During low temperature months, air is used for cooling, whilst in excessive temperature months, water is used. The water intake is composed at the manager of the makeup water, the blow down water and the evaporated water quantities. These 3 waters decide the cycles of awareness that may be reached with inside the cooling tower.
Make – up = Blowdown + Evaporation loss
The mass stability of a cooling tower machine may be written because the following:
This equation doesn’t take account of the method leaks, the wind age and flow that are simply kinds of out of control blow down. Moreover, the cycles of awareness is a ratio of the awareness in suspended solids among the blow down water and the makeup water.
Cycles = 
Water cooling is a technique of warmth elimination from additives and commercial equipment. Evaporative cooling the use of water is regularly extra green than air cooling. Water is less expensive and non-toxic; however, it may include impurities and reason corrosion.
Water cooling is typically used for cooling vehicle inner combustion engines and strength stations.
Water coolers utilizing convective warmness switch are used internal excessive-quit non-public computer systems to decrease the temperature of CPUs.
Other makes use of consist of the cooling of lubricant oil in pumps; for cooling functions in warmness exchangers; for cooling homes in HVAC and in chillers.
Water is less expensive, non-toxic, and to be had over maximum of the earth's surface. Liquid cooling gives better thermal conductivity than air cooling.
Water has surprisingly excessive particular warmness capability amongst typically to be had drinks at room temperature and atmospheric stress permitting green warmness switch over distance with low fees of mass switch.
- Cooling water can be recycled thru a recirculating machine or utilized in an unmarried by skip once-thru cooling (OTC) machine.
- Water's excessive enthalpy of vaporization lets in the choice of green evaporative cooling to get rid of waste warmness in cooling towers or cooling ponds.
- Recirculating structures can be open in the event that they depend upon evaporative cooling or closed if warmness elimination is performed in warmness exchangers with negligible evaporative loss.
- A warmness exchanger or condenser can also additionally separate non-touch cooling water from a fluid being cooled, or touch cooling water can also additionally without delay impinge on gadgets like noticed blades in which segment distinction lets in clean separation.
Environmental guidelines emphasize the decreased concentrations of waste merchandise in non-touch cooling water
Q7) Write a short note on calculations for surface condenser
A7)
In a surface condenser vapor is brought into contact with a solid surface which is cooled to a temperature below the saturation temperature of the vapor at its prevailing partial pressure. The surface is usually in the form of a "nest" or "bundle" of metal tubes, the coolant flowing inside the tubes and the vapor condensing on the outer or "shell-side."
The Overall Heat Transfer Coefficient, U (based on the condensing surface area), may be expressed in terms of local coefficients, a, via the sum of thermal resistances:
From through vapor condensate tube wall fouling coolant
1/U = 1/αU + 1/αf + 
+ F +
Where D0, Di are the tube outer and inner diameters and λw is the thermal conductivity of the tube material.
Heat alternate in unmarried section flows is commonly impeded with the aid of using the presence of insulating boundary layers.
On condensation, however, the huge discount in quantity because the vapor turns to condensate consequences in an influx of vapor toward the floor; the warmth switch is impeded handiest with the aid of using a skinny movie of condensate at the floor.
As a result, the condensation warmth switch coefficient is commonly better than that at the liquid coolant aspect, the latter turning into the controlling process.
The thermal resistance, F, of fouling at the coolant aspect is consequently a vital consideration. Condensing warmth switch prices are normally orders of importance better than the prices for a fuel line at the shell aspect, so condensers do now no longer typically require prolonged floor tubing. In a few packages spirally grooved tubing has been used to useful resource drainage of the condensate movie and to growth inner warmth switch with the aid of using tabulating the coolant flow.
If no wetting may be maintained (e.g., with the aid of using surfactants), drop wise condensation occurs, lowering the regions of condensate movie and ensuing in a warmth switch coefficient a few 4 instances that of film wise condensation.
More importantly frictional strain losses because the vapor passes among the intently pitched tubes lowers the partial strain—and subsequently saturation temperature—lowering the warmth alternate using temperature difference. (See additionally Condensation and Condensers.)
The important goal in floor condenser layout is to offer identical get right of entry to of vapor to all of the floor. Early tries to offer standard warmth switch coefficients for the layout of steam condensers took no account of the exact format of the tube nest, e.g., HEI (1978).
Modern exercise is to version the proposed nest on pc to calculate thermal overall performance and to make sure that any non-condensable gases gift are extracted on the factor of lowest strain, e.g.,
Rhodes and Marshland (1993). Poorly designed nests can also additionally go through immoderate frictional strain losses and comprise areas in which the tubes are protected with the aid of using no condensable gases.
Q8) Explain Dalton’s law of partial pressure
A8)
Dalton’s regulation of partial pressures is a fuel line regulation which states that the entire strain exerted through a combination of gases is identical to the sum of the partial pressures exerted through every man or woman fuel line with inside the combination. For example, the entire strain exerted through a combination of gases A and B is identical to the sum of the man or woman partial pressures exerted through fuel line A and fuel line B (as illustrated below).
Dalton’s Law Formula
Dalton’s law of partial pressures can be mathematically expressed as follows:
Ptotal = ∑ni=1pi∑i=1npi (or) Ptotal = P1 + P2 + P3 + …. + Pn
Where,
- Ptotal is the total pressure exerted by the mixture of gases
- P1, P2,…, Pn are the partial pressures of the gases 1, 2,…, ‘n’ in the mixture of ‘n’ gases
Expressing Partial Pressures in Terms of Mole Fraction
The mole fraction of a specific gas in a mixture of gases is equal to the ratio of the partial pressure of that gas to the total pressure exerted by the gaseous mixture. This mole fraction can also be used to calculate the total number of moles of a constituent gas when the total number of moles in the mixture is known. Furthermore, the volume occupied by a specific gas in a mixture can also be calculated with this mole fraction with the help of the equation provided below.
Xi=Pi /Ptotal = Vi / Vtotal = n1 / ntotal
Where Xi is the mole fraction of a gas ‘i’ in a mixture of ‘n’ gases, ‘n’ denotes the number of moles, ‘P’ denotes pressure, and ‘V’ denotes volume.
Q9) A mixture of hydrogen gas and oxygen gas exerts a total pressure of 1.5 atm on the walls of its container. If the partial pressure of hydrogen is 1 atm, find the mole fraction of oxygen in the mixture.
A9)
Given, Phydrogen = 1 atm, Ptotal = 1.5 atm
Applying Dalton’s law formula, Ptotal = Phydrogen + Poxygen
Therefore, Poxygen = 0.5 atm
Now, the mole fraction of oxygen, Xoxygen = (Poxygen/Ptotal) = 0.5/1.5 = 0.33
Therefore, the mole fraction of oxygen in the mixture is 0.33
Q10) At a temperature of 300K, 30 liters of gas A kept under pressure of 1 atm and 15 liters of gas B kept under pressure of 2 atm is transferred into an empty 10L container. Calculate the total pressure inside the container and the partial pressures of gas A and gas B (Assume that A and B are ideal gases).
A10)
From the ideal gas equation, PV = nRT
Number of moles of gas A = (30L*1atm)/ (0.08206 atm.L.mol-1.K-1 * 300K) = 1.22 mol
Number of moles of gas B = (15*2atm)/ (0.08206 atm.L.mol-1.K-1 * 300K) = 1.22 mol
Total number of moles in the gaseous mixture = 2.44 mol
Total pressure inside the 10L container = Ptot = nRT/V
Ptot = (2.44mol*0.08206 atm.L.mol-1.K-1*300K)/10L = 6.006 atm
Therefore, the total pressure inside the 10 litre container is 6.006 atm
Mole fraction of gas A = mole fraction of gas B = (1.22 mol/2.44 mol) = 0.5
Therefore, partial pressure of gas A = Therefore, partial pressure of gas B = 0.5*6.006 = 3.003 atm
Thus, the partial pressures of gases A and B in the 10L container are both equal to 3.003 atm.
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Q11) Explain sources of air leakages and air removal
A11)
SOURCES OF AIR LEAKAGE IN CONDENSER:
Following are the manner thru which air is found in a condenser,
(i) Leakage thru packing glands and really small holes with inside the shell.
(ii) Leakage thru joints and vents from atmospheric alleviation valves and different accessories.
(iii) Dissolved gases or air in boiler feed water, which in the long run enters the condenser with exhaust steam.
EFFECT OF LEAKAGE AIR ON CONDENSER PERFORMANCE:
The presence of air with inside the condenser has the subsequent consequences on condenser operation Back stress (or exhaust stress) with inside the steam engine or turbine will increase and therefore work done reduces.
Thermal performance of the strength plant reduces.
For the equal absolute stress (partial pre. Of steam + partial pre. Of air), the partial stress of steam decreases with air infiltration. Saturation temperature decreases; latent heat (enthalpy of evaporation) will increase. So, condenser calls for large amount of cooling water. Air being a bad conductor of warmth, its presence with inside the condenser influences fee of warmth transfer.
Thus to fulfil the requirement, floor vicinity of tubes is to be increased. The Size of condenser will increase. Rate of steam condensation is reduced.
AIR PUMP:
Presence of air in condenser has awful consequences at the condenser operation. Air have to be absolutely extracted out the use of extraction pumps.
The pump can be of dry kind which eliminates best air, or moist kind which eliminates air, condensate and non-condensable gases.
Fig indicates the operating of Edward's reciprocating moist kind air pump (or air extractor). It has no suction valve as it's far there with inside the regular pumps. It is hooked up to the condenser.
When the piston is on the pinnacle of the barrel, the condensate and air from the condenser are accumulated with inside the conical part of the barrel.
On the downward stroke of the piston, partial vacuum is created above the piston on account that transport valve is saved closed. When the piston uncovers the ports at some stage in its similarly downward movement, the air and water vapor entrapped with inside the conical portion, rush into the barrel area above the piston thru those ports.
During go back journey (upward movement) of the piston, the above aggregate is compressed and stress rises. When stress exceeds the atmospheric stress, the transport valve opens.
The aggregate of air and water vapor escapes out to the recent well, over a weir. The weir continues enough head of water above the transport valve to save you air leakage into the pump barrel. The water sealed alleviation valve operates while the stress with inside the barrel exceeds atmospheric stress.
Q12) What is Condenser Vacuum?
A12)
The vacuum available with inside the condenser relies upon on tightness of valve joints, quantity of air infiltration and temperature of steam after condensation.
Vacuum will now no longer be uniform throughout. It is least on the air pump section, excessive in.
The frame of the condenser and nonetheless better at exhaust valve. The diploma of vacuum measured via way of means of the vacuum gauge established on condenser may be expressed with inside the following ways.
(i) By extra of atmospheric stress over the found vacuum: For instance 650 mm vacuum manner, atmospheric stress is 650 mm of Hg above the condenser stress.
(ii) By the share vacuum: It is the ratio of found vacuum to atmospheric stress. For instance, if the gauge reads 650 mm Hg, with the barometer analyzing of 750 mm Hg, the share vacuum 650/750 x 100 = 86.67%.
(iii) By absolutely the stress: It is the distinction among barometric analyzing and vacuum gauge analyzing.
The characteristic of condensers in steam electricity flora is to hold a low temperature. This is important to attain the most thermal performance from a given plant.
The lowest temperature attained relies upon the temperature of the circulating water which condenses the steam. When the steam expands to a stress under the atmospheric stress, it can't be exhausted into ecosystem and consequently it exhausts in a vessel that is at a decrease stress than that of the exhaust steam.
The exhaust steam is condensed with inside the vessel that is called condenser. The temperature of condensed steam, normally called condensate, leaving the condenser is better than that of the circulating water at inlet and the condensate is eliminated from the condenser with the aid of an extraction pump which discharges the condensate to the hot-properly from in which the boiler feed pump feeds it to the
Thus floor condensers offer each a low exhaust stress and restoration of the condensate, while jet condensers offer handiest the low exhaust stress; there can be greater intimate warmth trade among cooling water and the steam with a realistic drawback because of blending of the cooling water the condensate, which drawback is obviated in floor condensers.
With jet condensers, exhaust steam mixes with cooling water, so this cooling water ought to be sparkling and loose from dangerous impurities if the condensate is to be re-used for feeding into boiler.
Salt water may be used; accordingly all marine steam installations are geared up with floor condensers.
In big steam turbine installations jet condensers are impractical due to the fact there may be lack of condensate, the excessive electricity intake of jet condenser pumps and the primary price of needful air pumps.
Therefore, for contemporary-day steam electricity plant floor condensers are used. However, with reciprocating steam engines and slight length turbine units, the jet condensers are used particularly in which a considerable deliver of desirable water is available.
Q13) What are air ejectors?
A13)
A vacuum ejector, or actually ejector is a kind of vacuum pump, which produces vacuum via the Venturi effect.
In an ejector, a running fluid (liquid or gaseous) flows via a jet nozzle right into a tube that first narrows after which expands in cross-sectional area.
The fluid leaving the jet is flowing at an excessive pace which because of Bernoulli's precept consequences in it having low strain, therefore producing a vacuum.
The outer tube then narrows right into a blending phase wherein the excessive pace running fluid mixes with the fluid this is drawn in with the aid of using the vacuum, supplying sufficient pace for it to be ejected, the tube then usually expands with the intention to lower the speed of the ejected stream, permitting the strain to easily boom to the outside strain.
The electricity of the vacuum produced relies upon on the speed and form of the fluid jet and the form of the constriction and combining sections, however if a liquid is used because the running fluid the electricity of the vacuum produced is constrained with the aid of using the vapor strain of the liquid (for water, 3.2 kPa or forty six psi or 32 mbar at 25 °C or 77 °F).
If now no longer thinking about the supply of the running fluid, vacuum ejectors may be considerably greater compact than a self-powered vacuum pump of the equal capacity.
The reasonably-priced and easy water aspirator is typically utilized in chemistry and biology laboratories and includes a tee becoming connected to a faucet and has a hose barb at one side.
The waft of water passes via the instantly part of the tee, which has restrict on the intersection, wherein the hose barb is connected. The vacuum hose ought to be linked to this barb.
However, they're water-intensive, and relying on what the vacuum is getting used for (e.g. Solvent removal), they are able to violate environmental safety legal guidelines together with the RCRA with the aid of using blending doubtlessly dangerous chemical compounds into the water stream, then flushing them down a drain that frequently leads immediately to the municipal sewer.
Their use has reduced extremely as small electric powered vacuum pumps are a ways greater effective, environmentally safe, and feature emerge as greater affordable, however the unrivaled simplicity and reliability of this tool have induced it to stay famous for small labs or as a backup.
Another, a good deal large model of this tool is utilized in maritime operations as a tool to dewater (drain) regions in a deliver which have been flooded in emergency conditions.
Typically called an educator in those packages, that is desired over electric pumps because of their simplicity, compact length, and substantially mitigated threat of explosion with inside the occasion that flammable drinks and/or vapors are gift.
Additionally, in contrast to many mechanical pumps, they also can by skip particles because the educator has no transferring elements that may be fouled.
This makes an educator specifically beneficial in conditions wherein becoming a particles strainer to the suction port will gift greater problems than it resolves.
Sizes, waft ratings, and packages vary, along with educators which might be completely installed (usually utilized in very big areas, together with a deliver's major engine room), or transportable fashions that may be reduced into areas with the aid of using a rope and provided and tired via firefighting hoses.
Most are provided via a deliver's firefighting major, and transportable fashions also can be provided with the aid of using an emergency pump, supplied it may deliver enough waft to perform the educator.
Let’s discover how an Ejector works. Firstly, it's far really well worth noting that Ejectors also are called Educators, Surface Jet Pumps, and Velocity Spools.
Q14) Write a working of air ejectors
A14)
- Based upon Bernoulli’s Principle, as the speed of a fluid increases, its strain decreases, and vice versa.
- This is regularly known as the suction chamber of the Ejector.
- Where the strain on this area is decrease than the strain of the suction fluid linked to the Ejector side-inlet or ‘suction branch’, it will likely be entrained/sucked into the frame of the Ejector.
- The fluid streams then tour via the diffuser phase of the Ejector, in which pace is reduced due to the diverging geometry and strain is regained.
- Importantly, the low strain suction circulation stories a strain increase/compression, even as the cause circulation sees a lower in strain, as a number of its power has been used to ‘do work’ at the suction circulation.
- The resultant discharge strain is consequently someplace among the cause and suction pressures.
- Ejectors are pipeline established gadgets and may be synthetic in nearly any fabric to match the manner conditions.
- They have three connections; Motive, Suction and Discharge.
Q15) What are cooling towers?
A15)
A cooling tower is a warmness rejection tool that rejects waste warmness to the ecosystem thru the cooling of a coolant move, generally a water move to a decrease temperature.
Cooling towers may also both use the evaporation of water to take away method warmness and funky the operating fluid to close to the wet-bulb air temperature or, with inside the case of closed circuit cooling towers or dry cooling towers, depend entirely on air to chill the operating fluid to close to the dry-bulb air temperature the use of Common programs encompass cooling the circulating water utilized in oil refineries, petrochemical and different chemical flowers, thermal electricity stations, nuclear electricity stations and HVAC structures for cooling homes.
The category is primarily based totally at the form of air induction into the tower: the primary styles of cooling towers are herbal draft and triggered draft cooling towers.
Cooling towers range in length from small roof-pinnacle gadgets to very huge hyperboloid systems (as with inside the adjoining image) that may be as much as 2 hundred meters (660 ft) tall and one hundred meters (330 ft) in diameter, or square systems that may be over forty meters (a hundred thirty ft) tall and eighty meters (260 ft) long.
Hyperboloid cooling towers are regularly related to nuclear electricity flowers, even though they're extensively utilized in a few coal-fired flowers and to a point in a few huge chemical and different business flowers.
Although those huge towers are very prominent, the good sized majority of cooling towers are a good deal smaller, inclusive of many gadgets established on or close to homes to discharge warmness from air conditioning.
This reduces the returned pressure, which in flip reduces the steam consumption, and as a consequence the gasoline consumption, at the same time as on the identical time growing electricity and recycling boiler-water.
However the condensers require an adequate deliver of cooling water, without which they're impractical. While water utilization isn't always an trouble with marine engines, it paperwork a substantial difficulty for plenty land-primarily based totally structures.
By the flip of the twentieth century, numerous evaporative strategies of recycling cooling water have been in use in regions missing a longtime water deliver, in addition to in city places in which municipal water mains might not be of enough deliver; dependable in instances of demand; or in any other case ok to fulfill cooling needs. In regions with to be had land, the structures took the shape of cooling ponds; in regions with confined land, including in cities, they took the shape of cooling towers.
These early towers have been placed both at the rooftops of homes or as free-status systems, provided with air with the aid of using fanatics or counting on herbal airflow.
At the pinnacle is a fixed of dispensing troughs, to which the water from the condenser have to be pumped; from those it trickles down over "mats" fabricated from wood slats or woven cord screens, which fill the gap with inside the tower.
Unit - 6
Steam condensers
Q1) What is steam condenser?
A1)
Steam condensers
A steam condenser is a closed vessel-kind warmth exchanger implemented to transform low-stress exhaust steam from the turbine to water.
A steam condenser is a mechanical tool hired to condense exhaust steam of the turbine into the water. It conducts this procedure with the assist of cooling water that circulates interior it from the cooling tower. The stress inside a steam condenser is held under the atmospheric stress to decorate efficiency. It is generally used to decrease the backpressure of the exhaust on the turbine quit.
Functions of the Steam Condenser
The reason of the usage of a steam condenser is: supporting maintain the stress low (under atmospheric stress) on the steam turbine quit to get most feasible strength and decrease the unique steam intake of an electricity plant.
Offering natural feed water to and from the new nicely.
The water is once more pumped to the boiler the usage of a boiler feed pump. Elevating the warmth switch fee with the aid of using casting off different non-condensable gases from the exiting steam.
Q2) Explain various Steam Condenser Parts
A2)
Steam Condenser Parts
The additives required to perform a steam condenser are as follows.
Condenser
It is used to condense the steam.
The steam with low stress offers its warmth to the coolant (right here water from the cooling tower), and it converts into the water thru the condensation procedure.
Condensate Extraction Pump
A Condensate Extraction Pump (CEP) is a pump mounted among the condenser and the new nicely to switch the condensate from the condenser to the new nicely. Hot Well It is a pit among the condenser and the boiler. It takes the condensate with the aid of using condensate pump from the condenser. The feed water is carried from the new nicely to the boiler.
Boiler Feed Pump
It is a pump positioned among the new nicely and boiler to supply the feed water from the new nicely to the boiler. This is achieved with the aid of using growing the condensate stress above boiler stress.
Air Extraction Pump
It is a pump applied to extract or take away the air from the steam condenser. Cooling Tower It is a tower containing bloodless water, and this water is furnished to flow into within the condenser to chill the steam. Cooling Water Pump It is a pump mounted among the condenser and the cooling tower. It circulates the coolant inside the condenser.
Q3) Write a short note on principle of steam condenser.
A3)
Steam Condenser Working Principle
In this section, we are able to supply a simple description of the way a steam condenser works. A glide of cooling water is constantly circulating from the condenser interior a steam condenser to the cooling tower and the cooling tower to the condenser.
When low-stress exhaust steam leaves the turbine and passes thru the condenser, it loses the warmth and condenses into water. The circulating cooling water plays the extraction of the warmth from the steam.
Two forms of gadgets are mounted at the condenser: the condensate extraction pump and the air extraction pump.
Therefore, whilst the steam condenses into water, it re-circulates once more to the steam generator with the assist of a condensate extraction pump. Using the air extraction pump, a vacuum (the stress under the atmospheric stress) is created within the condenser in order that cooling water can flow into effortlessly and additionally the condensate glide may be stabilized.
Due to the low stress within the condenser, the air enters the gadget in order that the condenser is packed with a combination of water, air, and steam.
Types & Classification of condensers
Three Main and Different Types of Condensers.
- Air-cooled condenser
- Natural Convection
- Forced Convection
- Water-cooled condenser
- Double Tube Shell and Coil Condenser
- Shell and Tube Condenser
Evaporative Condenser
Condensers primarily based totally at the condensing medium used to eliminate the warmth from the system, consist of 3 one-of-a-kind kinds. None of those 3 one-of-a-kind styles of condensers has mainly no blessings over the alternative. Depending at the situation, everyone have to be used appropriately. We are going to tricky at the features of those 3 condenser kinds with inside the following.
Air-cooled Condenser
Condensers of this kind use air because the outside fluid to reject the warmth from the system. Air-cooled condensers typically have copper coils in which refrigerant flows in. But this isn't always the complete story; this kind is subcategorized into subsets: herbal convection and compelled convection.
Q4) What do you mean by natural convention?
A4)
Natural Convection
In this kind of condenser, air involves touch with heat coils, soaking up the warmth of refrigerant in the coils, therefore the temper
Natural Convection
In this kind of condenser, air involves touch with heat coils, soaking up the warmth of refrigerant in the coils, therefore the temperature of air increases. As the nice and cozy air is lighter, it is going up and the bloodless air replaces and once more the bloodless air comes to the touch heat coils to reject the warmth. This herbal cycle maintains till the refrigerant loses its warmth. Since the glide charge of air is small and the radiation warmth switch is likewise now no longer very high, the blended warmth switch coefficient in those condensers is small.
As a result, an especially massive condensing floor is needed to reject a given quantity of warmth. Hence those styles of condensers are used for small capability refrigeration structures like family fridges and freezers.
Forced Convection
One of the alternative styles of condensers is compelled-convection. A fan or a blower does play the maximum essential position in casting off warmth from the refrigerant in the coils. The fan blows the air into the finned coils. A critical tip needs to be referred to right here and its miles that the fins of compelled convection condenser are positioned tightly subsequent to every other; so, if the dirt and dust fill the mild area among the fins, the air flowing and warmth rejection faces huge trouble.
Forced convection kind condensers are usually utilized in window air conditioners, water coolers, and packaged air con plants.
Water-cooled condenser
As it is able to be guessed, this kind of condenser makes use of water as fluid to eliminate warmth from the refrigerant. It is apparent that water-cooled condensers are used in which we've got an ok deliver of water. This kind, itself has 3 one-of-a-kind kinds: See All Water-Cooled Condenser for Sale
Q5) What is double tube?
A5)
Double Tube
Double tube condensers have a tube of water inner a massive refrigerant tube. The water absorbs maximum of the refrigerant warmth, however because the refrigerant tube is in touch with the herbal move of air, a part of the cooling system is on herbal convection. Although double-tube condensers usually had been used with inside the past, the massive wide variety of gaskets and flanges utilized in those warmth exchangers ends in protection problems.
Shell and Coil Condensers
In a shell-and-coil condenser, a welded shell consists of a coil of finned water tubing. In this kind of water-cooled condenser, the new refrigerant flows with inside the shell even as the cooling water circulates in the coils and condenses the refrigerant. It is normally maximum compact and occasional in fee.
Shell and Tube Condensers
One of the styles of condensers plays the system of rejecting warmth with the aid of using having a cylindrical shell including water tubes. In a shell and tube condenser, water is pumped thru the pipes even as refrigerant flows with inside the shell.
Installations of fins in pipes permits higher warmth switch. The shell-and-tube condensers are normally low in fee and smooth to maintain. The maximum not unusual place kind of shell and tube condensers is the horizontal shell kind. However, vertical shell and tube condensers are typically used with ammonia in massive capability structures in order that cleansing of the tubes is viable from the pinnacle even as the plant is running.
Q6) Explain quality and quantity of cooling water required
A6)
Cooling towers are a crucial thing of refrigeration systems. They are not unusual place in industries together with oil & gas, chemical processing, electricity plants, datacenters.
Water is the maximum not unusual place cooling medium utilized in cooling processes, because of its availability and excessive warmness capacity. These makes use of require massive quantities of water and frequently gift ability for water saving.
This financial savings bring about decrease water and sewer payments and reduced remedy costs. In the commercial marketplace there may be discovered 3 kinds of cooling towers: open circuit, closed circuit and as soon as thru machine.
Cooling towers may be air-cooled or water-cooled. Water-cooled cooling towers are extra not unusual place, because the cooling electricity of water is more potent than air.
Hybrid cooling towers have become increasingly more appealing for Datacenter cooling in critical Europe.
During low temperature months, air is used for cooling, whilst in excessive temperature months, water is used. The water intake is composed at the manager of the makeup water, the blow down water and the evaporated water quantities. These 3 waters decide the cycles of awareness that may be reached with inside the cooling tower.
Make – up = Blowdown + Evaporation loss
The mass stability of a cooling tower machine may be written because the following:
This equation doesn’t take account of the method leaks, the wind age and flow that are simply kinds of out of control blow down. Moreover, the cycles of awareness is a ratio of the awareness in suspended solids among the blow down water and the makeup water.
Cycles = 
Water cooling is a technique of warmth elimination from additives and commercial equipment. Evaporative cooling the use of water is regularly extra green than air cooling. Water is less expensive and non-toxic; however, it may include impurities and reason corrosion.
Water cooling is typically used for cooling vehicle inner combustion engines and strength stations.
Water coolers utilizing convective warmness switch are used internal excessive-quit non-public computer systems to decrease the temperature of CPUs.
Other makes use of consist of the cooling of lubricant oil in pumps; for cooling functions in warmness exchangers; for cooling homes in HVAC and in chillers.
Water is less expensive, non-toxic, and to be had over maximum of the earth's surface. Liquid cooling gives better thermal conductivity than air cooling.
Water has surprisingly excessive particular warmness capability amongst typically to be had drinks at room temperature and atmospheric stress permitting green warmness switch over distance with low fees of mass switch.
- Cooling water can be recycled thru a recirculating machine or utilized in an unmarried by skip once-thru cooling (OTC) machine.
- Water's excessive enthalpy of vaporization lets in the choice of green evaporative cooling to get rid of waste warmness in cooling towers or cooling ponds.
- Recirculating structures can be open in the event that they depend upon evaporative cooling or closed if warmness elimination is performed in warmness exchangers with negligible evaporative loss.
- A warmness exchanger or condenser can also additionally separate non-touch cooling water from a fluid being cooled, or touch cooling water can also additionally without delay impinge on gadgets like noticed blades in which segment distinction lets in clean separation.
Environmental guidelines emphasize the decreased concentrations of waste merchandise in non-touch cooling water
Q7) Write a short note on calculations for surface condenser
A7)
In a surface condenser vapor is brought into contact with a solid surface which is cooled to a temperature below the saturation temperature of the vapor at its prevailing partial pressure. The surface is usually in the form of a "nest" or "bundle" of metal tubes, the coolant flowing inside the tubes and the vapor condensing on the outer or "shell-side."
The Overall Heat Transfer Coefficient, U (based on the condensing surface area), may be expressed in terms of local coefficients, a, via the sum of thermal resistances:
From through vapor condensate tube wall fouling coolant
1/U = 1/αU + 1/αf + 
+ F +
Where D0, Di are the tube outer and inner diameters and λw is the thermal conductivity of the tube material.
Heat alternate in unmarried section flows is commonly impeded with the aid of using the presence of insulating boundary layers.
On condensation, however, the huge discount in quantity because the vapor turns to condensate consequences in an influx of vapor toward the floor; the warmth switch is impeded handiest with the aid of using a skinny movie of condensate at the floor.
As a result, the condensation warmth switch coefficient is commonly better than that at the liquid coolant aspect, the latter turning into the controlling process.
The thermal resistance, F, of fouling at the coolant aspect is consequently a vital consideration. Condensing warmth switch prices are normally orders of importance better than the prices for a fuel line at the shell aspect, so condensers do now no longer typically require prolonged floor tubing. In a few packages spirally grooved tubing has been used to useful resource drainage of the condensate movie and to growth inner warmth switch with the aid of using tabulating the coolant flow.
If no wetting may be maintained (e.g., with the aid of using surfactants), drop wise condensation occurs, lowering the regions of condensate movie and ensuing in a warmth switch coefficient a few 4 instances that of film wise condensation.
More importantly frictional strain losses because the vapor passes among the intently pitched tubes lowers the partial strain—and subsequently saturation temperature—lowering the warmth alternate using temperature difference. (See additionally Condensation and Condensers.)
The important goal in floor condenser layout is to offer identical get right of entry to of vapor to all of the floor. Early tries to offer standard warmth switch coefficients for the layout of steam condensers took no account of the exact format of the tube nest, e.g., HEI (1978).
Modern exercise is to version the proposed nest on pc to calculate thermal overall performance and to make sure that any non-condensable gases gift are extracted on the factor of lowest strain, e.g.,
Rhodes and Marshland (1993). Poorly designed nests can also additionally go through immoderate frictional strain losses and comprise areas in which the tubes are protected with the aid of using no condensable gases.
Q8) Explain Dalton’s law of partial pressure
A8)
Dalton’s regulation of partial pressures is a fuel line regulation which states that the entire strain exerted through a combination of gases is identical to the sum of the partial pressures exerted through every man or woman fuel line with inside the combination. For example, the entire strain exerted through a combination of gases A and B is identical to the sum of the man or woman partial pressures exerted through fuel line A and fuel line B (as illustrated below).
Dalton’s Law Formula
Dalton’s law of partial pressures can be mathematically expressed as follows:
Ptotal = ∑ni=1pi∑i=1npi (or) Ptotal = P1 + P2 + P3 + …. + Pn
Where,
- Ptotal is the total pressure exerted by the mixture of gases
- P1, P2,…, Pn are the partial pressures of the gases 1, 2,…, ‘n’ in the mixture of ‘n’ gases
Expressing Partial Pressures in Terms of Mole Fraction
The mole fraction of a specific gas in a mixture of gases is equal to the ratio of the partial pressure of that gas to the total pressure exerted by the gaseous mixture. This mole fraction can also be used to calculate the total number of moles of a constituent gas when the total number of moles in the mixture is known. Furthermore, the volume occupied by a specific gas in a mixture can also be calculated with this mole fraction with the help of the equation provided below.
Xi=Pi /Ptotal = Vi / Vtotal = n1 / ntotal
Where Xi is the mole fraction of a gas ‘i’ in a mixture of ‘n’ gases, ‘n’ denotes the number of moles, ‘P’ denotes pressure, and ‘V’ denotes volume.
Q9) A mixture of hydrogen gas and oxygen gas exerts a total pressure of 1.5 atm on the walls of its container. If the partial pressure of hydrogen is 1 atm, find the mole fraction of oxygen in the mixture.
A9)
Given, Phydrogen = 1 atm, Ptotal = 1.5 atm
Applying Dalton’s law formula, Ptotal = Phydrogen + Poxygen
Therefore, Poxygen = 0.5 atm
Now, the mole fraction of oxygen, Xoxygen = (Poxygen/Ptotal) = 0.5/1.5 = 0.33
Therefore, the mole fraction of oxygen in the mixture is 0.33
Q10) At a temperature of 300K, 30 liters of gas A kept under pressure of 1 atm and 15 liters of gas B kept under pressure of 2 atm is transferred into an empty 10L container. Calculate the total pressure inside the container and the partial pressures of gas A and gas B (Assume that A and B are ideal gases).
A10)
From the ideal gas equation, PV = nRT
Number of moles of gas A = (30L*1atm)/ (0.08206 atm.L.mol-1.K-1 * 300K) = 1.22 mol
Number of moles of gas B = (15*2atm)/ (0.08206 atm.L.mol-1.K-1 * 300K) = 1.22 mol
Total number of moles in the gaseous mixture = 2.44 mol
Total pressure inside the 10L container = Ptot = nRT/V
Ptot = (2.44mol*0.08206 atm.L.mol-1.K-1*300K)/10L = 6.006 atm
Therefore, the total pressure inside the 10 litre container is 6.006 atm
Mole fraction of gas A = mole fraction of gas B = (1.22 mol/2.44 mol) = 0.5
Therefore, partial pressure of gas A = Therefore, partial pressure of gas B = 0.5*6.006 = 3.003 atm
Thus, the partial pressures of gases A and B in the 10L container are both equal to 3.003 atm.
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Q11) Explain sources of air leakages and air removal
A11)
SOURCES OF AIR LEAKAGE IN CONDENSER:
Following are the manner thru which air is found in a condenser,
(i) Leakage thru packing glands and really small holes with inside the shell.
(ii) Leakage thru joints and vents from atmospheric alleviation valves and different accessories.
(iii) Dissolved gases or air in boiler feed water, which in the long run enters the condenser with exhaust steam.
EFFECT OF LEAKAGE AIR ON CONDENSER PERFORMANCE:
The presence of air with inside the condenser has the subsequent consequences on condenser operation Back stress (or exhaust stress) with inside the steam engine or turbine will increase and therefore work done reduces.
Thermal performance of the strength plant reduces.
For the equal absolute stress (partial pre. Of steam + partial pre. Of air), the partial stress of steam decreases with air infiltration. Saturation temperature decreases; latent heat (enthalpy of evaporation) will increase. So, condenser calls for large amount of cooling water. Air being a bad conductor of warmth, its presence with inside the condenser influences fee of warmth transfer.
Thus to fulfil the requirement, floor vicinity of tubes is to be increased. The Size of condenser will increase. Rate of steam condensation is reduced.
AIR PUMP:
Presence of air in condenser has awful consequences at the condenser operation. Air have to be absolutely extracted out the use of extraction pumps.
The pump can be of dry kind which eliminates best air, or moist kind which eliminates air, condensate and non-condensable gases.
Fig indicates the operating of Edward's reciprocating moist kind air pump (or air extractor). It has no suction valve as it's far there with inside the regular pumps. It is hooked up to the condenser.
When the piston is on the pinnacle of the barrel, the condensate and air from the condenser are accumulated with inside the conical part of the barrel.
On the downward stroke of the piston, partial vacuum is created above the piston on account that transport valve is saved closed. When the piston uncovers the ports at some stage in its similarly downward movement, the air and water vapor entrapped with inside the conical portion, rush into the barrel area above the piston thru those ports.
During go back journey (upward movement) of the piston, the above aggregate is compressed and stress rises. When stress exceeds the atmospheric stress, the transport valve opens.
The aggregate of air and water vapor escapes out to the recent well, over a weir. The weir continues enough head of water above the transport valve to save you air leakage into the pump barrel. The water sealed alleviation valve operates while the stress with inside the barrel exceeds atmospheric stress.
Q12) What is Condenser Vacuum?
A12)
The vacuum available with inside the condenser relies upon on tightness of valve joints, quantity of air infiltration and temperature of steam after condensation.
Vacuum will now no longer be uniform throughout. It is least on the air pump section, excessive in.
The frame of the condenser and nonetheless better at exhaust valve. The diploma of vacuum measured via way of means of the vacuum gauge established on condenser may be expressed with inside the following ways.
(i) By extra of atmospheric stress over the found vacuum: For instance 650 mm vacuum manner, atmospheric stress is 650 mm of Hg above the condenser stress.
(ii) By the share vacuum: It is the ratio of found vacuum to atmospheric stress. For instance, if the gauge reads 650 mm Hg, with the barometer analyzing of 750 mm Hg, the share vacuum 650/750 x 100 = 86.67%.
(iii) By absolutely the stress: It is the distinction among barometric analyzing and vacuum gauge analyzing.
The characteristic of condensers in steam electricity flora is to hold a low temperature. This is important to attain the most thermal performance from a given plant.
The lowest temperature attained relies upon the temperature of the circulating water which condenses the steam. When the steam expands to a stress under the atmospheric stress, it can't be exhausted into ecosystem and consequently it exhausts in a vessel that is at a decrease stress than that of the exhaust steam.
The exhaust steam is condensed with inside the vessel that is called condenser. The temperature of condensed steam, normally called condensate, leaving the condenser is better than that of the circulating water at inlet and the condensate is eliminated from the condenser with the aid of an extraction pump which discharges the condensate to the hot-properly from in which the boiler feed pump feeds it to the
Thus floor condensers offer each a low exhaust stress and restoration of the condensate, while jet condensers offer handiest the low exhaust stress; there can be greater intimate warmth trade among cooling water and the steam with a realistic drawback because of blending of the cooling water the condensate, which drawback is obviated in floor condensers.
With jet condensers, exhaust steam mixes with cooling water, so this cooling water ought to be sparkling and loose from dangerous impurities if the condensate is to be re-used for feeding into boiler.
Salt water may be used; accordingly all marine steam installations are geared up with floor condensers.
In big steam turbine installations jet condensers are impractical due to the fact there may be lack of condensate, the excessive electricity intake of jet condenser pumps and the primary price of needful air pumps.
Therefore, for contemporary-day steam electricity plant floor condensers are used. However, with reciprocating steam engines and slight length turbine units, the jet condensers are used particularly in which a considerable deliver of desirable water is available.
Q13) What are air ejectors?
A13)
A vacuum ejector, or actually ejector is a kind of vacuum pump, which produces vacuum via the Venturi effect.
In an ejector, a running fluid (liquid or gaseous) flows via a jet nozzle right into a tube that first narrows after which expands in cross-sectional area.
The fluid leaving the jet is flowing at an excessive pace which because of Bernoulli's precept consequences in it having low strain, therefore producing a vacuum.
The outer tube then narrows right into a blending phase wherein the excessive pace running fluid mixes with the fluid this is drawn in with the aid of using the vacuum, supplying sufficient pace for it to be ejected, the tube then usually expands with the intention to lower the speed of the ejected stream, permitting the strain to easily boom to the outside strain.
The electricity of the vacuum produced relies upon on the speed and form of the fluid jet and the form of the constriction and combining sections, however if a liquid is used because the running fluid the electricity of the vacuum produced is constrained with the aid of using the vapor strain of the liquid (for water, 3.2 kPa or forty six psi or 32 mbar at 25 °C or 77 °F).
If now no longer thinking about the supply of the running fluid, vacuum ejectors may be considerably greater compact than a self-powered vacuum pump of the equal capacity.
The reasonably-priced and easy water aspirator is typically utilized in chemistry and biology laboratories and includes a tee becoming connected to a faucet and has a hose barb at one side.
The waft of water passes via the instantly part of the tee, which has restrict on the intersection, wherein the hose barb is connected. The vacuum hose ought to be linked to this barb.
However, they're water-intensive, and relying on what the vacuum is getting used for (e.g. Solvent removal), they are able to violate environmental safety legal guidelines together with the RCRA with the aid of using blending doubtlessly dangerous chemical compounds into the water stream, then flushing them down a drain that frequently leads immediately to the municipal sewer.
Their use has reduced extremely as small electric powered vacuum pumps are a ways greater effective, environmentally safe, and feature emerge as greater affordable, however the unrivaled simplicity and reliability of this tool have induced it to stay famous for small labs or as a backup.
Another, a good deal large model of this tool is utilized in maritime operations as a tool to dewater (drain) regions in a deliver which have been flooded in emergency conditions.
Typically called an educator in those packages, that is desired over electric pumps because of their simplicity, compact length, and substantially mitigated threat of explosion with inside the occasion that flammable drinks and/or vapors are gift.
Additionally, in contrast to many mechanical pumps, they also can by skip particles because the educator has no transferring elements that may be fouled.
This makes an educator specifically beneficial in conditions wherein becoming a particles strainer to the suction port will gift greater problems than it resolves.
Sizes, waft ratings, and packages vary, along with educators which might be completely installed (usually utilized in very big areas, together with a deliver's major engine room), or transportable fashions that may be reduced into areas with the aid of using a rope and provided and tired via firefighting hoses.
Most are provided via a deliver's firefighting major, and transportable fashions also can be provided with the aid of using an emergency pump, supplied it may deliver enough waft to perform the educator.
Let’s discover how an Ejector works. Firstly, it's far really well worth noting that Ejectors also are called Educators, Surface Jet Pumps, and Velocity Spools.
Q14) Write a working of air ejectors
A14)
- Based upon Bernoulli’s Principle, as the speed of a fluid increases, its strain decreases, and vice versa.
- This is regularly known as the suction chamber of the Ejector.
- Where the strain on this area is decrease than the strain of the suction fluid linked to the Ejector side-inlet or ‘suction branch’, it will likely be entrained/sucked into the frame of the Ejector.
- The fluid streams then tour via the diffuser phase of the Ejector, in which pace is reduced due to the diverging geometry and strain is regained.
- Importantly, the low strain suction circulation stories a strain increase/compression, even as the cause circulation sees a lower in strain, as a number of its power has been used to ‘do work’ at the suction circulation.
- The resultant discharge strain is consequently someplace among the cause and suction pressures.
- Ejectors are pipeline established gadgets and may be synthetic in nearly any fabric to match the manner conditions.
- They have three connections; Motive, Suction and Discharge.
Q15) What are cooling towers?
A15)
A cooling tower is a warmness rejection tool that rejects waste warmness to the ecosystem thru the cooling of a coolant move, generally a water move to a decrease temperature.
Cooling towers may also both use the evaporation of water to take away method warmness and funky the operating fluid to close to the wet-bulb air temperature or, with inside the case of closed circuit cooling towers or dry cooling towers, depend entirely on air to chill the operating fluid to close to the dry-bulb air temperature the use of Common programs encompass cooling the circulating water utilized in oil refineries, petrochemical and different chemical flowers, thermal electricity stations, nuclear electricity stations and HVAC structures for cooling homes.
The category is primarily based totally at the form of air induction into the tower: the primary styles of cooling towers are herbal draft and triggered draft cooling towers.
Cooling towers range in length from small roof-pinnacle gadgets to very huge hyperboloid systems (as with inside the adjoining image) that may be as much as 2 hundred meters (660 ft) tall and one hundred meters (330 ft) in diameter, or square systems that may be over forty meters (a hundred thirty ft) tall and eighty meters (260 ft) long.
Hyperboloid cooling towers are regularly related to nuclear electricity flowers, even though they're extensively utilized in a few coal-fired flowers and to a point in a few huge chemical and different business flowers.
Although those huge towers are very prominent, the good sized majority of cooling towers are a good deal smaller, inclusive of many gadgets established on or close to homes to discharge warmness from air conditioning.
This reduces the returned pressure, which in flip reduces the steam consumption, and as a consequence the gasoline consumption, at the same time as on the identical time growing electricity and recycling boiler-water.
However the condensers require an adequate deliver of cooling water, without which they're impractical. While water utilization isn't always an trouble with marine engines, it paperwork a substantial difficulty for plenty land-primarily based totally structures.
By the flip of the twentieth century, numerous evaporative strategies of recycling cooling water have been in use in regions missing a longtime water deliver, in addition to in city places in which municipal water mains might not be of enough deliver; dependable in instances of demand; or in any other case ok to fulfill cooling needs. In regions with to be had land, the structures took the shape of cooling ponds; in regions with confined land, including in cities, they took the shape of cooling towers.
These early towers have been placed both at the rooftops of homes or as free-status systems, provided with air with the aid of using fanatics or counting on herbal airflow.
At the pinnacle is a fixed of dispensing troughs, to which the water from the condenser have to be pumped; from those it trickles down over "mats" fabricated from wood slats or woven cord screens, which fill the gap with inside the tower.
Unit - 6
Steam condensers
Q1) What is steam condenser?
A1)
Steam condensers
A steam condenser is a closed vessel-kind warmth exchanger implemented to transform low-stress exhaust steam from the turbine to water.
A steam condenser is a mechanical tool hired to condense exhaust steam of the turbine into the water. It conducts this procedure with the assist of cooling water that circulates interior it from the cooling tower. The stress inside a steam condenser is held under the atmospheric stress to decorate efficiency. It is generally used to decrease the backpressure of the exhaust on the turbine quit.
Functions of the Steam Condenser
The reason of the usage of a steam condenser is: supporting maintain the stress low (under atmospheric stress) on the steam turbine quit to get most feasible strength and decrease the unique steam intake of an electricity plant.
Offering natural feed water to and from the new nicely.
The water is once more pumped to the boiler the usage of a boiler feed pump. Elevating the warmth switch fee with the aid of using casting off different non-condensable gases from the exiting steam.
Q2) Explain various Steam Condenser Parts
A2)
Steam Condenser Parts
The additives required to perform a steam condenser are as follows.
Condenser
It is used to condense the steam.
The steam with low stress offers its warmth to the coolant (right here water from the cooling tower), and it converts into the water thru the condensation procedure.
Condensate Extraction Pump
A Condensate Extraction Pump (CEP) is a pump mounted among the condenser and the new nicely to switch the condensate from the condenser to the new nicely. Hot Well It is a pit among the condenser and the boiler. It takes the condensate with the aid of using condensate pump from the condenser. The feed water is carried from the new nicely to the boiler.
Boiler Feed Pump
It is a pump positioned among the new nicely and boiler to supply the feed water from the new nicely to the boiler. This is achieved with the aid of using growing the condensate stress above boiler stress.
Air Extraction Pump
It is a pump applied to extract or take away the air from the steam condenser. Cooling Tower It is a tower containing bloodless water, and this water is furnished to flow into within the condenser to chill the steam. Cooling Water Pump It is a pump mounted among the condenser and the cooling tower. It circulates the coolant inside the condenser.
Q3) Write a short note on principle of steam condenser.
A3)
Steam Condenser Working Principle
In this section, we are able to supply a simple description of the way a steam condenser works. A glide of cooling water is constantly circulating from the condenser interior a steam condenser to the cooling tower and the cooling tower to the condenser.
When low-stress exhaust steam leaves the turbine and passes thru the condenser, it loses the warmth and condenses into water. The circulating cooling water plays the extraction of the warmth from the steam.
Two forms of gadgets are mounted at the condenser: the condensate extraction pump and the air extraction pump.
Therefore, whilst the steam condenses into water, it re-circulates once more to the steam generator with the assist of a condensate extraction pump. Using the air extraction pump, a vacuum (the stress under the atmospheric stress) is created within the condenser in order that cooling water can flow into effortlessly and additionally the condensate glide may be stabilized.
Due to the low stress within the condenser, the air enters the gadget in order that the condenser is packed with a combination of water, air, and steam.
Types & Classification of condensers
Three Main and Different Types of Condensers.
- Air-cooled condenser
- Natural Convection
- Forced Convection
- Water-cooled condenser
- Double Tube Shell and Coil Condenser
- Shell and Tube Condenser
Evaporative Condenser
Condensers primarily based totally at the condensing medium used to eliminate the warmth from the system, consist of 3 one-of-a-kind kinds. None of those 3 one-of-a-kind styles of condensers has mainly no blessings over the alternative. Depending at the situation, everyone have to be used appropriately. We are going to tricky at the features of those 3 condenser kinds with inside the following.
Air-cooled Condenser
Condensers of this kind use air because the outside fluid to reject the warmth from the system. Air-cooled condensers typically have copper coils in which refrigerant flows in. But this isn't always the complete story; this kind is subcategorized into subsets: herbal convection and compelled convection.
Q4) What do you mean by natural convention?
A4)
Natural Convection
In this kind of condenser, air involves touch with heat coils, soaking up the warmth of refrigerant in the coils, therefore the temper
Natural Convection
In this kind of condenser, air involves touch with heat coils, soaking up the warmth of refrigerant in the coils, therefore the temperature of air increases. As the nice and cozy air is lighter, it is going up and the bloodless air replaces and once more the bloodless air comes to the touch heat coils to reject the warmth. This herbal cycle maintains till the refrigerant loses its warmth. Since the glide charge of air is small and the radiation warmth switch is likewise now no longer very high, the blended warmth switch coefficient in those condensers is small.
As a result, an especially massive condensing floor is needed to reject a given quantity of warmth. Hence those styles of condensers are used for small capability refrigeration structures like family fridges and freezers.
Forced Convection
One of the alternative styles of condensers is compelled-convection. A fan or a blower does play the maximum essential position in casting off warmth from the refrigerant in the coils. The fan blows the air into the finned coils. A critical tip needs to be referred to right here and its miles that the fins of compelled convection condenser are positioned tightly subsequent to every other; so, if the dirt and dust fill the mild area among the fins, the air flowing and warmth rejection faces huge trouble.
Forced convection kind condensers are usually utilized in window air conditioners, water coolers, and packaged air con plants.
Water-cooled condenser
As it is able to be guessed, this kind of condenser makes use of water as fluid to eliminate warmth from the refrigerant. It is apparent that water-cooled condensers are used in which we've got an ok deliver of water. This kind, itself has 3 one-of-a-kind kinds: See All Water-Cooled Condenser for Sale
Q5) What is double tube?
A5)
Double Tube
Double tube condensers have a tube of water inner a massive refrigerant tube. The water absorbs maximum of the refrigerant warmth, however because the refrigerant tube is in touch with the herbal move of air, a part of the cooling system is on herbal convection. Although double-tube condensers usually had been used with inside the past, the massive wide variety of gaskets and flanges utilized in those warmth exchangers ends in protection problems.
Shell and Coil Condensers
In a shell-and-coil condenser, a welded shell consists of a coil of finned water tubing. In this kind of water-cooled condenser, the new refrigerant flows with inside the shell even as the cooling water circulates in the coils and condenses the refrigerant. It is normally maximum compact and occasional in fee.
Shell and Tube Condensers
One of the styles of condensers plays the system of rejecting warmth with the aid of using having a cylindrical shell including water tubes. In a shell and tube condenser, water is pumped thru the pipes even as refrigerant flows with inside the shell.
Installations of fins in pipes permits higher warmth switch. The shell-and-tube condensers are normally low in fee and smooth to maintain. The maximum not unusual place kind of shell and tube condensers is the horizontal shell kind. However, vertical shell and tube condensers are typically used with ammonia in massive capability structures in order that cleansing of the tubes is viable from the pinnacle even as the plant is running.
Q6) Explain quality and quantity of cooling water required
A6)
Cooling towers are a crucial thing of refrigeration systems. They are not unusual place in industries together with oil & gas, chemical processing, electricity plants, datacenters.
Water is the maximum not unusual place cooling medium utilized in cooling processes, because of its availability and excessive warmness capacity. These makes use of require massive quantities of water and frequently gift ability for water saving.
This financial savings bring about decrease water and sewer payments and reduced remedy costs. In the commercial marketplace there may be discovered 3 kinds of cooling towers: open circuit, closed circuit and as soon as thru machine.
Cooling towers may be air-cooled or water-cooled. Water-cooled cooling towers are extra not unusual place, because the cooling electricity of water is more potent than air.
Hybrid cooling towers have become increasingly more appealing for Datacenter cooling in critical Europe.
During low temperature months, air is used for cooling, whilst in excessive temperature months, water is used. The water intake is composed at the manager of the makeup water, the blow down water and the evaporated water quantities. These 3 waters decide the cycles of awareness that may be reached with inside the cooling tower.
Make – up = Blowdown + Evaporation loss
The mass stability of a cooling tower machine may be written because the following:
This equation doesn’t take account of the method leaks, the wind age and flow that are simply kinds of out of control blow down. Moreover, the cycles of awareness is a ratio of the awareness in suspended solids among the blow down water and the makeup water.
Cycles = 
Water cooling is a technique of warmth elimination from additives and commercial equipment. Evaporative cooling the use of water is regularly extra green than air cooling. Water is less expensive and non-toxic; however, it may include impurities and reason corrosion.
Water cooling is typically used for cooling vehicle inner combustion engines and strength stations.
Water coolers utilizing convective warmness switch are used internal excessive-quit non-public computer systems to decrease the temperature of CPUs.
Other makes use of consist of the cooling of lubricant oil in pumps; for cooling functions in warmness exchangers; for cooling homes in HVAC and in chillers.
Water is less expensive, non-toxic, and to be had over maximum of the earth's surface. Liquid cooling gives better thermal conductivity than air cooling.
Water has surprisingly excessive particular warmness capability amongst typically to be had drinks at room temperature and atmospheric stress permitting green warmness switch over distance with low fees of mass switch.
- Cooling water can be recycled thru a recirculating machine or utilized in an unmarried by skip once-thru cooling (OTC) machine.
- Water's excessive enthalpy of vaporization lets in the choice of green evaporative cooling to get rid of waste warmness in cooling towers or cooling ponds.
- Recirculating structures can be open in the event that they depend upon evaporative cooling or closed if warmness elimination is performed in warmness exchangers with negligible evaporative loss.
- A warmness exchanger or condenser can also additionally separate non-touch cooling water from a fluid being cooled, or touch cooling water can also additionally without delay impinge on gadgets like noticed blades in which segment distinction lets in clean separation.
Environmental guidelines emphasize the decreased concentrations of waste merchandise in non-touch cooling water
Q7) Write a short note on calculations for surface condenser
A7)
In a surface condenser vapor is brought into contact with a solid surface which is cooled to a temperature below the saturation temperature of the vapor at its prevailing partial pressure. The surface is usually in the form of a "nest" or "bundle" of metal tubes, the coolant flowing inside the tubes and the vapor condensing on the outer or "shell-side."
The Overall Heat Transfer Coefficient, U (based on the condensing surface area), may be expressed in terms of local coefficients, a, via the sum of thermal resistances:
From through vapor condensate tube wall fouling coolant
1/U = 1/αU + 1/αf + 
+ F +
Where D0, Di are the tube outer and inner diameters and λw is the thermal conductivity of the tube material.
Heat alternate in unmarried section flows is commonly impeded with the aid of using the presence of insulating boundary layers.
On condensation, however, the huge discount in quantity because the vapor turns to condensate consequences in an influx of vapor toward the floor; the warmth switch is impeded handiest with the aid of using a skinny movie of condensate at the floor.
As a result, the condensation warmth switch coefficient is commonly better than that at the liquid coolant aspect, the latter turning into the controlling process.
The thermal resistance, F, of fouling at the coolant aspect is consequently a vital consideration. Condensing warmth switch prices are normally orders of importance better than the prices for a fuel line at the shell aspect, so condensers do now no longer typically require prolonged floor tubing. In a few packages spirally grooved tubing has been used to useful resource drainage of the condensate movie and to growth inner warmth switch with the aid of using tabulating the coolant flow.
If no wetting may be maintained (e.g., with the aid of using surfactants), drop wise condensation occurs, lowering the regions of condensate movie and ensuing in a warmth switch coefficient a few 4 instances that of film wise condensation.
More importantly frictional strain losses because the vapor passes among the intently pitched tubes lowers the partial strain—and subsequently saturation temperature—lowering the warmth alternate using temperature difference. (See additionally Condensation and Condensers.)
The important goal in floor condenser layout is to offer identical get right of entry to of vapor to all of the floor. Early tries to offer standard warmth switch coefficients for the layout of steam condensers took no account of the exact format of the tube nest, e.g., HEI (1978).
Modern exercise is to version the proposed nest on pc to calculate thermal overall performance and to make sure that any non-condensable gases gift are extracted on the factor of lowest strain, e.g.,
Rhodes and Marshland (1993). Poorly designed nests can also additionally go through immoderate frictional strain losses and comprise areas in which the tubes are protected with the aid of using no condensable gases.
Q8) Explain Dalton’s law of partial pressure
A8)
Dalton’s regulation of partial pressures is a fuel line regulation which states that the entire strain exerted through a combination of gases is identical to the sum of the partial pressures exerted through every man or woman fuel line with inside the combination. For example, the entire strain exerted through a combination of gases A and B is identical to the sum of the man or woman partial pressures exerted through fuel line A and fuel line B (as illustrated below).
Dalton’s Law Formula
Dalton’s law of partial pressures can be mathematically expressed as follows:
Ptotal = ∑ni=1pi∑i=1npi (or) Ptotal = P1 + P2 + P3 + …. + Pn
Where,
- Ptotal is the total pressure exerted by the mixture of gases
- P1, P2,…, Pn are the partial pressures of the gases 1, 2,…, ‘n’ in the mixture of ‘n’ gases
Expressing Partial Pressures in Terms of Mole Fraction
The mole fraction of a specific gas in a mixture of gases is equal to the ratio of the partial pressure of that gas to the total pressure exerted by the gaseous mixture. This mole fraction can also be used to calculate the total number of moles of a constituent gas when the total number of moles in the mixture is known. Furthermore, the volume occupied by a specific gas in a mixture can also be calculated with this mole fraction with the help of the equation provided below.
Xi=Pi /Ptotal = Vi / Vtotal = n1 / ntotal
Where Xi is the mole fraction of a gas ‘i’ in a mixture of ‘n’ gases, ‘n’ denotes the number of moles, ‘P’ denotes pressure, and ‘V’ denotes volume.
Q9) A mixture of hydrogen gas and oxygen gas exerts a total pressure of 1.5 atm on the walls of its container. If the partial pressure of hydrogen is 1 atm, find the mole fraction of oxygen in the mixture.
A9)
Given, Phydrogen = 1 atm, Ptotal = 1.5 atm
Applying Dalton’s law formula, Ptotal = Phydrogen + Poxygen
Therefore, Poxygen = 0.5 atm
Now, the mole fraction of oxygen, Xoxygen = (Poxygen/Ptotal) = 0.5/1.5 = 0.33
Therefore, the mole fraction of oxygen in the mixture is 0.33
Q10) At a temperature of 300K, 30 liters of gas A kept under pressure of 1 atm and 15 liters of gas B kept under pressure of 2 atm is transferred into an empty 10L container. Calculate the total pressure inside the container and the partial pressures of gas A and gas B (Assume that A and B are ideal gases).
A10)
From the ideal gas equation, PV = nRT
Number of moles of gas A = (30L*1atm)/ (0.08206 atm.L.mol-1.K-1 * 300K) = 1.22 mol
Number of moles of gas B = (15*2atm)/ (0.08206 atm.L.mol-1.K-1 * 300K) = 1.22 mol
Total number of moles in the gaseous mixture = 2.44 mol
Total pressure inside the 10L container = Ptot = nRT/V
Ptot = (2.44mol*0.08206 atm.L.mol-1.K-1*300K)/10L = 6.006 atm
Therefore, the total pressure inside the 10 litre container is 6.006 atm
Mole fraction of gas A = mole fraction of gas B = (1.22 mol/2.44 mol) = 0.5
Therefore, partial pressure of gas A = Therefore, partial pressure of gas B = 0.5*6.006 = 3.003 atm
Thus, the partial pressures of gases A and B in the 10L container are both equal to 3.003 atm.
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Q11) Explain sources of air leakages and air removal
A11)
SOURCES OF AIR LEAKAGE IN CONDENSER:
Following are the manner thru which air is found in a condenser,
(i) Leakage thru packing glands and really small holes with inside the shell.
(ii) Leakage thru joints and vents from atmospheric alleviation valves and different accessories.
(iii) Dissolved gases or air in boiler feed water, which in the long run enters the condenser with exhaust steam.
EFFECT OF LEAKAGE AIR ON CONDENSER PERFORMANCE:
The presence of air with inside the condenser has the subsequent consequences on condenser operation Back stress (or exhaust stress) with inside the steam engine or turbine will increase and therefore work done reduces.
Thermal performance of the strength plant reduces.
For the equal absolute stress (partial pre. Of steam + partial pre. Of air), the partial stress of steam decreases with air infiltration. Saturation temperature decreases; latent heat (enthalpy of evaporation) will increase. So, condenser calls for large amount of cooling water. Air being a bad conductor of warmth, its presence with inside the condenser influences fee of warmth transfer.
Thus to fulfil the requirement, floor vicinity of tubes is to be increased. The Size of condenser will increase. Rate of steam condensation is reduced.
AIR PUMP:
Presence of air in condenser has awful consequences at the condenser operation. Air have to be absolutely extracted out the use of extraction pumps.
The pump can be of dry kind which eliminates best air, or moist kind which eliminates air, condensate and non-condensable gases.
Fig indicates the operating of Edward's reciprocating moist kind air pump (or air extractor). It has no suction valve as it's far there with inside the regular pumps. It is hooked up to the condenser.
When the piston is on the pinnacle of the barrel, the condensate and air from the condenser are accumulated with inside the conical part of the barrel.
On the downward stroke of the piston, partial vacuum is created above the piston on account that transport valve is saved closed. When the piston uncovers the ports at some stage in its similarly downward movement, the air and water vapor entrapped with inside the conical portion, rush into the barrel area above the piston thru those ports.
During go back journey (upward movement) of the piston, the above aggregate is compressed and stress rises. When stress exceeds the atmospheric stress, the transport valve opens.
The aggregate of air and water vapor escapes out to the recent well, over a weir. The weir continues enough head of water above the transport valve to save you air leakage into the pump barrel. The water sealed alleviation valve operates while the stress with inside the barrel exceeds atmospheric stress.
Q12) What is Condenser Vacuum?
A12)
The vacuum available with inside the condenser relies upon on tightness of valve joints, quantity of air infiltration and temperature of steam after condensation.
Vacuum will now no longer be uniform throughout. It is least on the air pump section, excessive in.
The frame of the condenser and nonetheless better at exhaust valve. The diploma of vacuum measured via way of means of the vacuum gauge established on condenser may be expressed with inside the following ways.
(i) By extra of atmospheric stress over the found vacuum: For instance 650 mm vacuum manner, atmospheric stress is 650 mm of Hg above the condenser stress.
(ii) By the share vacuum: It is the ratio of found vacuum to atmospheric stress. For instance, if the gauge reads 650 mm Hg, with the barometer analyzing of 750 mm Hg, the share vacuum 650/750 x 100 = 86.67%.
(iii) By absolutely the stress: It is the distinction among barometric analyzing and vacuum gauge analyzing.
The characteristic of condensers in steam electricity flora is to hold a low temperature. This is important to attain the most thermal performance from a given plant.
The lowest temperature attained relies upon the temperature of the circulating water which condenses the steam. When the steam expands to a stress under the atmospheric stress, it can't be exhausted into ecosystem and consequently it exhausts in a vessel that is at a decrease stress than that of the exhaust steam.
The exhaust steam is condensed with inside the vessel that is called condenser. The temperature of condensed steam, normally called condensate, leaving the condenser is better than that of the circulating water at inlet and the condensate is eliminated from the condenser with the aid of an extraction pump which discharges the condensate to the hot-properly from in which the boiler feed pump feeds it to the
Thus floor condensers offer each a low exhaust stress and restoration of the condensate, while jet condensers offer handiest the low exhaust stress; there can be greater intimate warmth trade among cooling water and the steam with a realistic drawback because of blending of the cooling water the condensate, which drawback is obviated in floor condensers.
With jet condensers, exhaust steam mixes with cooling water, so this cooling water ought to be sparkling and loose from dangerous impurities if the condensate is to be re-used for feeding into boiler.
Salt water may be used; accordingly all marine steam installations are geared up with floor condensers.
In big steam turbine installations jet condensers are impractical due to the fact there may be lack of condensate, the excessive electricity intake of jet condenser pumps and the primary price of needful air pumps.
Therefore, for contemporary-day steam electricity plant floor condensers are used. However, with reciprocating steam engines and slight length turbine units, the jet condensers are used particularly in which a considerable deliver of desirable water is available.
Q13) What are air ejectors?
A13)
A vacuum ejector, or actually ejector is a kind of vacuum pump, which produces vacuum via the Venturi effect.
In an ejector, a running fluid (liquid or gaseous) flows via a jet nozzle right into a tube that first narrows after which expands in cross-sectional area.
The fluid leaving the jet is flowing at an excessive pace which because of Bernoulli's precept consequences in it having low strain, therefore producing a vacuum.
The outer tube then narrows right into a blending phase wherein the excessive pace running fluid mixes with the fluid this is drawn in with the aid of using the vacuum, supplying sufficient pace for it to be ejected, the tube then usually expands with the intention to lower the speed of the ejected stream, permitting the strain to easily boom to the outside strain.
The electricity of the vacuum produced relies upon on the speed and form of the fluid jet and the form of the constriction and combining sections, however if a liquid is used because the running fluid the electricity of the vacuum produced is constrained with the aid of using the vapor strain of the liquid (for water, 3.2 kPa or forty six psi or 32 mbar at 25 °C or 77 °F).
If now no longer thinking about the supply of the running fluid, vacuum ejectors may be considerably greater compact than a self-powered vacuum pump of the equal capacity.
The reasonably-priced and easy water aspirator is typically utilized in chemistry and biology laboratories and includes a tee becoming connected to a faucet and has a hose barb at one side.
The waft of water passes via the instantly part of the tee, which has restrict on the intersection, wherein the hose barb is connected. The vacuum hose ought to be linked to this barb.
However, they're water-intensive, and relying on what the vacuum is getting used for (e.g. Solvent removal), they are able to violate environmental safety legal guidelines together with the RCRA with the aid of using blending doubtlessly dangerous chemical compounds into the water stream, then flushing them down a drain that frequently leads immediately to the municipal sewer.
Their use has reduced extremely as small electric powered vacuum pumps are a ways greater effective, environmentally safe, and feature emerge as greater affordable, however the unrivaled simplicity and reliability of this tool have induced it to stay famous for small labs or as a backup.
Another, a good deal large model of this tool is utilized in maritime operations as a tool to dewater (drain) regions in a deliver which have been flooded in emergency conditions.
Typically called an educator in those packages, that is desired over electric pumps because of their simplicity, compact length, and substantially mitigated threat of explosion with inside the occasion that flammable drinks and/or vapors are gift.
Additionally, in contrast to many mechanical pumps, they also can by skip particles because the educator has no transferring elements that may be fouled.
This makes an educator specifically beneficial in conditions wherein becoming a particles strainer to the suction port will gift greater problems than it resolves.
Sizes, waft ratings, and packages vary, along with educators which might be completely installed (usually utilized in very big areas, together with a deliver's major engine room), or transportable fashions that may be reduced into areas with the aid of using a rope and provided and tired via firefighting hoses.
Most are provided via a deliver's firefighting major, and transportable fashions also can be provided with the aid of using an emergency pump, supplied it may deliver enough waft to perform the educator.
Let’s discover how an Ejector works. Firstly, it's far really well worth noting that Ejectors also are called Educators, Surface Jet Pumps, and Velocity Spools.
Q14) Write a working of air ejectors
A14)
- Based upon Bernoulli’s Principle, as the speed of a fluid increases, its strain decreases, and vice versa.
- This is regularly known as the suction chamber of the Ejector.
- Where the strain on this area is decrease than the strain of the suction fluid linked to the Ejector side-inlet or ‘suction branch’, it will likely be entrained/sucked into the frame of the Ejector.
- The fluid streams then tour via the diffuser phase of the Ejector, in which pace is reduced due to the diverging geometry and strain is regained.
- Importantly, the low strain suction circulation stories a strain increase/compression, even as the cause circulation sees a lower in strain, as a number of its power has been used to ‘do work’ at the suction circulation.
- The resultant discharge strain is consequently someplace among the cause and suction pressures.
- Ejectors are pipeline established gadgets and may be synthetic in nearly any fabric to match the manner conditions.
- They have three connections; Motive, Suction and Discharge.
Q15) What are cooling towers?
A15)
A cooling tower is a warmness rejection tool that rejects waste warmness to the ecosystem thru the cooling of a coolant move, generally a water move to a decrease temperature.
Cooling towers may also both use the evaporation of water to take away method warmness and funky the operating fluid to close to the wet-bulb air temperature or, with inside the case of closed circuit cooling towers or dry cooling towers, depend entirely on air to chill the operating fluid to close to the dry-bulb air temperature the use of Common programs encompass cooling the circulating water utilized in oil refineries, petrochemical and different chemical flowers, thermal electricity stations, nuclear electricity stations and HVAC structures for cooling homes.
The category is primarily based totally at the form of air induction into the tower: the primary styles of cooling towers are herbal draft and triggered draft cooling towers.
Cooling towers range in length from small roof-pinnacle gadgets to very huge hyperboloid systems (as with inside the adjoining image) that may be as much as 2 hundred meters (660 ft) tall and one hundred meters (330 ft) in diameter, or square systems that may be over forty meters (a hundred thirty ft) tall and eighty meters (260 ft) long.
Hyperboloid cooling towers are regularly related to nuclear electricity flowers, even though they're extensively utilized in a few coal-fired flowers and to a point in a few huge chemical and different business flowers.
Although those huge towers are very prominent, the good sized majority of cooling towers are a good deal smaller, inclusive of many gadgets established on or close to homes to discharge warmness from air conditioning.
This reduces the returned pressure, which in flip reduces the steam consumption, and as a consequence the gasoline consumption, at the same time as on the identical time growing electricity and recycling boiler-water.
However the condensers require an adequate deliver of cooling water, without which they're impractical. While water utilization isn't always an trouble with marine engines, it paperwork a substantial difficulty for plenty land-primarily based totally structures.
By the flip of the twentieth century, numerous evaporative strategies of recycling cooling water have been in use in regions missing a longtime water deliver, in addition to in city places in which municipal water mains might not be of enough deliver; dependable in instances of demand; or in any other case ok to fulfill cooling needs. In regions with to be had land, the structures took the shape of cooling ponds; in regions with confined land, including in cities, they took the shape of cooling towers.
These early towers have been placed both at the rooftops of homes or as free-status systems, provided with air with the aid of using fanatics or counting on herbal airflow.
At the pinnacle is a fixed of dispensing troughs, to which the water from the condenser have to be pumped; from those it trickles down over "mats" fabricated from wood slats or woven cord screens, which fill the gap with inside the tower.
