*This system is an improvement on the vapour compression system which requires a compressor to compress large volume of vapour.
*The large compressors require large power to operate them. This system reduces the volume of the vapour before it is condensed by absorbing greater amount of the vapour in the liquid called as absorbent.
*The reduced volume or bulk of the system would require small power to operate it.
*This system has a least number of moving parts.
*They are quite in operation and are used both in commercial as well as in domestic installation.
*In recent years, they have been used extensively in recreation vehicles, camper-trailers and boats as portable units due to their operation from a small gas cylinder.
*It is a heat operated unit which uses a refrigerant that is alternately absorbed and liberated by the absorbent.
*The simple vapour absorption system is shown in fig. in which an absorber, pump, a generator and expansion valve replace the compressor of a vapour compression system.
Numerous combinations of fluids are used in this system, but the combination of ammonia and water is most commonly used in the absorption refrigerators. The solution used is called as aqua ammonia
