Various Processes of Vapor Absorption Cycle
The various processes of the vapor absorption cycle are similar to the one in vapor compression cycle, only the method of compression of the refrigerant is different. In vapor absorption system ammonia is used as the refrigerant, which has very high affinity to dissolve in water. Here are various processes of vapor absorption cycle:
1) Compression or absorption of the refrigerant: In vapor absorption system there is no traditional compressor, instead there is absorber. The absorber consists of water, called as absorbent, in which the refrigerant, ammonia, dissolves. This mixture of water and ammonia is then pumped and heated thus increase in temperature and pressure of the ammonia occurs. Ammonia leaves the absorber at high pressure and high temperature. Some work has to be provided to the pump and heating is carried out by the steam. The amount of electricity required by the pump is much lesser than that required by the compressor hence there is lots of saving of electricity, however, the additional source of heat in the form of steam has to be provided.
2) Condensation : The refrigerant at pressure and temperature then enters condenser where it is cooled by water and its temperature and pressure reduces.
3) Expansion : Thereafter the expansion of refrigerant occurs in throttling valve due to which the temperature and pressure of the ammonia refrigerant reduces drastically and suddenly.
4) Evaporation : Finally the refrigerant enters the evaporator where it produces the cooling effect. It leaves the evaporator in vapor state and then enters absorber, where it is absorbed by absorbent, water and compressed by the pump. This process repeats again and cycle continues.
There are different types absorbents like water and lithium bromide that can be used with refrigerant ammonia. These systems are called water absorption system or lithium bromide absorption system.
Must read: Simple Vapor Absorption Refrigeration System