Vapor absorption refrigeration System

  • In this system, a pump, a generator, an absorber and a pressure reducing valve replace the compressor.
  • The vapor absorption system uses heat energy, instead of mechanical energy as in vapor compression systems.
  • It is of two types:

        1) Water ammonia vapor absorption cycle

        2) Water Lithium bromide vapor absorption cycle

Water ammonia vapor absorption cycle:

In this system,

  • Water is used as absorbent.
  • Ammonia is used as refrigerant.

Parts are required:

    1) Evaporator

    2) Expansion Valve

    3) Condenser

    4) Absorber

    5) Pump

    6) Vapor generator


  • The low pressure ammonia vapor refrigerant leaving the evaporator enters the absorber where it is absorbed by cold water in the absorber.
  • In absorber, cold water mixes with weak solution ammonia vapor refrigerant and forms strong solution.
  • This strong solution is pumped to the generator where external heat is applied.
  • During the heating process, strong solution is converted into weak solution means ammonia is driven off from the water and enters into the condenser while the water flows back to the absorber.
  • Condenser rejects heat and converts it into liquid form.
  • Then this liquid refrigerant flow into the evaporator, where it absorbs heat and converts into vapor refrigerant. Again this vapor refrigerant enters tot the absorber and the process continues.

Water Lithium bromide vapor absorption cycle:

  • In this system, water is used as refrigerant and lithium bromide is used as absorbent.
  • The low pressure vapor refrigerant leaving the evaporator enters the absorber.
  • In the absorber, the lithium bromide absorbs the water refrigerant, forming a solution of  water and lithium bromide.
  • This solution is pumped by the pump to the generator where it is heated.
  • After heating, strong solution converts into the weak solution means water refrigerant gets vaporized.
  • This vapor refrigerant enters to the condenser where it is cooled and lithium bromide flows back to the absorber where it further absorbs water coming from the evaporator.
  • Cooled refrigerant flows into the evaporator and it absorbs heat, converts into low temperature vapor refrigerant.
  • This low temperature vapor refrigerant flows into the absorber and the process continues.

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