Friday, June 22, 2012

Absorption Chiller in HVAC system

Absorption chiller  occupies vital position in an HVAC system.Absorption chiller is an equipment which uses a heat source, a refrigerant and an absorbent for producing chilled or hot water. In the types of chillers,along with vapor compression water chiller or electric chiller ,absorption cooling system is also used in many applications.Absorption chillers produce chilled water under vacuum conditions for the purpose of air-conditioning and technology process.

Basic components of Vapor absorption chillers

Absorption chillers in its simplest form (single stage) consist of following main parts:

Steam absorption chiller
  • Generator
  • Condenser
  • Evaporator
  • Absorber
  • Heat exchanger
  • Refrigerant Pump
  • Solution pump

Working Principle of Absorption Chiller

1. Function of Generator in absorption chiller

In generator of absorption chillers weak solution is heated by operating steam (steam absorption chillers),hot water or flue gases in indirect fired absorption chillers.While direct fired absorption chillers are Natural gas, Diesel or Kerosene Oil Operated.After heating in generator solution is concentrated and high temperature refrigerant vapors are produced.After generator process in a chiller high temperature and pressure refrigerant vapors travel to condenser. A strong solution enters absorber through heat exchanger in exchanging heat with weak solution .

2. Function of Condenser  in absorption chiller

water chiller
vapor absorption cycle
Refrigerant vapor from generator is condensed in condenser by cooling water.Condensation is constant pressure process where refrigerant (water) gives off its heat to cooling water .In this way refrigerant heat is carried to atmosphere.In water cooled chillers , cooling water recycles after exchanging heat with air in cooling towers of same HVACsystem.

3. Function of Evaporator in absorption chiller

Refrigerant from condenser flows to evaporator .In this compartment of absorption chiller,refrigerant gets vaporized by taking heat from chilled water.Refrigerant from evaporator refrigerant pan is pumped over the evaporator tubes with the help of refrigerant pump.Flow of refrigerant over evaporator tubes evaporates the refrigerant thus producing refrigeration effect, and evaporates to form vapor by absorbing heat of chilled water flowing through tubes.In this way,evaporation takes place at constant pressure process where refrigerant gets latent heat from chiller water.Chiller absorption takes place here in absorber.Chilled water is cooled and return to the system of customer.

4. Function of Absorber in absorption chiller

simplified diagram of  absorption chiller works
Produced refrigerant vapor enters absorber, and absorbed by strong solution in the absorber.In this way,strong solution is diluted by absorbing refrigerant vapor in absorber . Heat generated is carried to atmosphere by cooling water.

5. Function of HVAC Solution Pump in absorption chiller

This weak solution is transferred by solution pump to generator for concentration.Pumps are components in absorption cooling systems which require electric energy for its operation.Weak solution from the absorber is pumped into the generator through heat exchanger. This process is continued, and refrigeration effect is repeated.

Must Read : Absorption Chillers vs Electric (Compression) chillers

Try here HVAC quiz related to absorption chillers or vapor compression cycle.
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