Vapour absorption refrigeration system

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Vapour absorption refrigeration system


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Vapour absorption refrigeration system :

Vapour absorption refrigeration system PRESENTED BY: Vikram Vijayant Rana Regd.No . 0901221063




INTRODUCTION The vapour absorption refrigeration system is one of the method of producing refrigerating effect. Uses heat energy instead of mechanical energy as in vapour compression system. In the vapour absorption system the compressor is replaced by an absorber,a pump,a generator,and a pressure reducing valve. These componet in vapour absorption system perform the same function as that of a compressor in vapour compression system.


REFRIGERATION The term ‘ refrigeration’may be defined as the process of removing heat from a substance under controlled condition. In other words the refrigeration means a continued extraction of heat from a body whose temperature is already below the temperature of its surrounding. UNITS OF REFRIGERATION- The practical unit of refrigertion is expressed in terms of “ tonne of refrigeration. REFRIGERANT- Refrigerant is a heat carrying medium in the refrigeration system,which absorb heat from the low temp system and discard heat so absorb to a higher temperature system. In the vapour absorption refrigeration system we use ammonia as the refrigernt .



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In this system the low pressure amonia vapour leaving the evaporator enters the absorber where it is absorbed by the cold water in the absorber. The water has ability to absorb very large quantities of of ammonia vapour and the solution thus is formed,is known as aqua-ammonia. The absorption of ammonia vapour in water lowers the pressure in the absorber which in turns draws more ammonia vapour from the evaporator and thus rises the the temperature of solution. Some form of cooling arrengement ( usually water cooling)is employed in the absorber to remove the heat of the solution evolved here. This is necessary in order to increase the absorbing capacity of water because higher temperature water absorbs less ammonia vapour .

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The strong solution thus formed in the absober is pumped to the generator by the liquid pump. The strong solution of ammonia in the generator is heated by some external source such as gas or steam. During the heating process the ammonia vapour isdriven off the solution at high pressure leaving behind the hot weak ammonia in the generator. This weak ammonia solution flows back to the absorber at low pressure after passing through the pressure reducing valve. The high pressure ammonia vapour from the generator is condensed in the condenser to ahigh pressure liquid ammonia which passedto the expansion valve trough the receiver to the evaporator.


PRACTICAL VAPOUR ABSORPTION SYSTM Itmainly consists of three parts ANALYSER RECTIFIER HEAT EXCHANGER ANALYSER-When ammonia is vapourised in the generator some water is also vapourised,and flow into the condenser along with ammonia . if these unwanted particle are not removed before entering into the condenser,they will enter into the expansion valve where they freeze and choke the pipe line,so in order to remove the unwanted particle flowing in the condeser the analyser is used.

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RECTIFIER- In case the water vapour are not completely removed in the analyaer,a closed type of vapour cooler called rectifier is also known as dehydrator is used,it may be of water cooled. HEAT EXCHANGER-The heat exchanger provided between the pump and the generator which is use to cool the weak hot solution returnig from the generator to absorber.

Domestic electrolux(ammonia hydrogen) refrigerator:

Domestic electrolux (ammonia hydrogen) refrigerator

Basic componet of domestic refrigerator:

Basic componet of domestic refrigerator 1-Generator 2-Separator 3-Analyser 4-Rectifier 5-Main condenser 6-Helping condenser 7-Liquid heat exchanger 8-Absorber A-High temperature evaporator B-low temperature evaporator 9-Hydrogen-Reservoir

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This type of refrigerator is also called a three fluid absorption system. It is called three fluid absorption system because it uses 3 fluids such as ammonia,hydrogen and water. Here in this refrigeration system the movable part that is the pump is not used,there fore it produces less noise and less wear and tear property. In the generator ,the ammonia vapour is formed due to heating of strong ammonia solution. This formed ammonia vapour is passed through separator,analyser,rectifier to remove the water particles and water vapour is carried out by ammonia.

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The dehydrated ammonia vapour is passed to the main- condenser,where 90% vapour is condensed here and the remaining 10% is further condensed in the helping-condenser. This condensed high pressure ammonia liquid is passed to the evaporator of section A and B and it is evaporated in the presence of hydrogen atmoshpere . The mixture of ammonia vapour and hydrogen is passed to the absorver through the gas heat exchanger,the hot hydrogen coming from absorver is cooled by cold mixture of hydrogen and ammonia coming from evaporator.

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The weak liquid absorb ammonia vapour in the absorber liberating the hydrogen free and become strong solution. During the absorption,the heat liberated is given to the hydrogen and hydrogen become hot. This hot hydrogen is cooled in the gas heat exchanger. The strong solution from the absorber is passed to the generator through liquid heat exchanger, where the strong solution is heated and weak solution is cooled.

Comparision between absorption system and compression system:

Comparision between absorption system and compression system ABSORPTION SYSTEM- 1-Use low grade energy like heat there fore ,may be worked on exhaust system from I.C engine etc. 2-Moving part are only in the pump,which is small element of the system,Hence the operation is smooth. 3-The system can work on lower evaporator pressure also without affecting the cop. 4-No effect of reducing the load on performance. COMPRESSION SYSTEM- 1-Use high grade energy mechanical work. 2-Moving parts are in the compressor there fore more wear,tear and noise is produced. 3-The cop decreases considerably with decrease in evaporator pressure. 4-Performance is adversely affected at partial load.


COP OF AN IDEAL VAPOUR ABSORPTON REFRIGERATION SYSTEM- C.O.P=Heat absorbed in evaporator/(work done by pump+heat supplied in generator) According to first law of thermodynamics Qc= Qg+Qe Qc=The heat is discharged to the atmoshpere or cooling water from the condenser and absorber. Qg =heat is given to the refrigerant in the generator. Qe =heat is absorbed by the refigerant in the evaporator. Tg =temperature at which heat( Qg ) is given to the generator. Tc =Temperature at which heat (Qc) is discharged to atmoshpere Te=Temperature at which heat ( Qe ) is absorved in the evaporator.

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C.O.P= Qe / Qg = Qe / Qe [ Tc -Te]Te*[TG]/[ Tg-Tc ] = [Te]/[ Tc -Te]*[ Tg-Tc ]/ Tg


advantage As there is no moving part in the entire system,the operation is essentially quite and subjected to a very little wear. The load variations does not effect the performance of a vapour absorption system. Absorption system may be designed to use any readily available source of thermal energy such as process steam ,hot exhaust from furnaces and solar energy,there fore they can be used in places where electric power is hard to obtain or is very expensive. Here pump is used for pumping refrigerant absorbant solution,which consume less power. Maintance cost is low as because of absence of moving part.


disadvantages Set up is too large as it consists of three more equipment those are absorber,generator ,and pump. Initial cost is high. Corrosive in nature. Low working pressure. Due to low working pressure the cop of vapour refrigeraton is low,it is about 1.1 High heat rejection system is required,as heat is being rejected from condenser,analyser,rectifier and absorber.


application This system is used in domestic. It is also used in power plant.


conclusion From the above discussion we conclude that vapour absorption refrigeration system is one of the important refrigeration system which can work in the absence of electric current. And during the operation it produces less noise,because due to the absence of moving part,so it is more preferable than the compression refrigeration system.



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