Vapour absorption refrigeration system: Definition, Diagram, Construction, Working [with Pdf]

What is vapour absorption refrigeration system?

1) Vapour absorption refrigeration system is one of the types of refrigeration systems.

2) As compared to the Vapour compression system, In the vapour absorption system compressor is Replaced by Generator, Absorber & Pump.

3) In this System, Ammonia (NH3) is used as Refrigerant & Water + Ammonia is used as Absorbent.

Vapour absorption refrigeration system diagram:

Vapour absorption refrigeration system diagram


It consists Of Condenser, Generator, Absorber, Expansion Valve, Pressure Reducing Valve & Pump.

A) ABSORBER:- From Evaporator, Vapour NH3 Enters into Absorber. An absorber is Already filled with Absorbent (water+NH3). Absorbent Absorbs the  NH3 Vapours and Strong NH3 Solution is Forms. During Absorption of NH3, Heat is Generated.

If Temperature Inside the Absorber Increases, Water will lose Absorbing Capacity so a Strong NH3 Solution will Not Form. 

Hence Cooling is Available at Absorber.

B) Pump:- It is Used to Suck the Strong NH3 Solution From Absorber & Deliver to Generator.

C) Generator:- It is Used to Heat the NH3 Solution with the help of heating Coils. From Pump, Strong NH3 Enters into the Generator. This NH3 Heated by Generator, Hence High-Pressure NH3 Vapours are Form.

From Generator High-Pressure NH3 Vapours Goes to Condenser & Remaining Weak Solution From Generator Returns to Absorber through Pressure Reducing Valve ( PRV ) . 

If this Weak Solution Goes to Condenser, It may damage the system.

D) Pressure reducing valve ( PRV ):- It is Used to Reduce Pressure of Weak NH3 Solution. It is located Between the Generator & Absorber.

E) Condenser:- From Evaporator, NH3 Vapours Enter into the Condenser. Condensation Is Heat Removal Process. Hence in Condenser heat is Remove From NH3 Vapours with the help of a Cooling Medium. After Condenser, High-Pressure Liquid NH3 Goes to Expansion Valve.

F) Expansion valve:- Expansion Valve is located between the condenser & evaporator. After the condenser, high-pressure liquid NH3 Enters into Expansion Valve. Expansion Valve Converts the High-Pressure Liquid NH3 to Low-Pressure Vapour NH3 by Expansion. After Expansion Valve, Liquid NH3 Goes to Evaporator.

G) Evaporator:- After Expansion Valve, Low-Pressure NH3 Vapours Enters into the Evaporator. Evaporator Absorbs the Heat from Enclosed Room ( to be Cooled ) with the help of NH3.

After Evaporator, Vapour NH3 Goes to Absorber.

Vapour absorption refrigeration system working: 

1) When Vapour NH3 from Evaporator Enters into the Absorber, It gets Absorbed by Absorbent ( water + NH3 ) and Strong NH3 Solution Forms. 

2) The Strong NH3 Solution From Absorber Suck by Pump & Deliver to Generator. 

3) When Strong NH3 Solution enters into Generator, Generator heat the NH3 Solution with the help of Heating Coils. 

4) From Generator High-Pressure Vapour NH3 Forms which is Flows through Condenser. The Weak Solution Remains in Generator is Returns to Absorber through Pressure Reducing Valve.

5) When High-Pressure Vapour NH3 enters into Condenser, Condenser Removes the heat from Vapour NH3 with the help of Cooling Medium. 

6) After Condenser, High-Pressure Liquid NH3 Enters into the Expansion Valve, where it Expands and Converted into Low-Pressure Vapour NH3.

7) After Expansion Valve, Vapour NH3 Enters into the Evaporator, Where It Absorbs heat from Enclosed Room ( to be Cooled ).

8) After Evaporator, Vapour NH3 again enters into the Absorber.

 Hence In this way Cycle Continues and provides Cooling to Enclosed Room.


  1. What is Vapour absorption refrigeration?

    Vapour Absorption Refrigeration System is one of the types of Refrigeration systems.

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