An Absorption Chiller is a machine uses a heat source to generate chilled water rather than electrical source that is used in vapor compression cycle.
It’s an attractive idea to produce chilled water with heat.
As the same in vapor compression cycle, absorption cycle achieve removing heat using the evaporation of a refrigerant at low pressure and the ejection of heat using the condensation the refrigerant at high pressure.
The major difference between a vapor compression system and an absorption chiller is that a vapor compression system using a compressor to make the pressure difference required to circulate the refrigerant while the absorption chiller using heat.
The absorption chiller is very attractive because using energy in the form of heat, such as solar or waste heat, makes it using a little work input and saving in money. Also it can works with industrial waste heat streams.
Comparison Between Absorption Refrigeration Cycle and Vapor Compression Cycle:
The vapor compression cycle basically consists of an evaporator, condenser, throttling valve, and a compressor. Figure below illustrates the components and flow arrangement for it.
In the shown cycle, refrigerant in the form of a cool mixture of liquid and vapor centers the evaporator at low pressure (4). Then using relatively warm air or water, the liquid refrigerant will boil. The resulted vapor (1) is pumped by the compressor, which raises refrigerant vapor pressure and temperature.
This hot refrigerant vapor at high pressure (2) enters the condenser, where heat is released to a lower temperature ambient air or water, and the refrigerant vapor turns into a liquid, then passes to the expansion device (3), where the pressure of the refrigerant is reduced to the pressure of the evaporator, and a little amount of the refrigerant boils, cooling the staying liquid refrigerant to the wanted evaporator temperature. Then mixture of the cool liquid and vapor refrigerant (4) passes to the evaporator and repeats the cycle.
The absorption cycle is similar to the vapor compression cycle in many components, but it uses a different compression method and different refrigerants unlike the vapor compression cycle.The absorption cycle replaces the compressor with a generator, an absorber, and pump.