Describe briefly absorption cycle?

Dear Samar,

Absorption cycle is practical in some devices such as 'Absorption Chillers' or refrigerators, which involves Evaporator, Condenser, Generator, and absorbent pump circuit. In Generator, steam or hot water from a boiler, or from a heat recovery unit is used to boil a solution of refrigerant/absorbent (most systems using water/lithium bromide for chilling and ammonia/water for refrigeration as the working solutions) for separating refrigerant from absorbent. The absorption chiller then captures the refrigerant vapor from the boiling process, and uses the energy in this fluid to chill water after condensing-evaporating-absorbing steps. In Evaporator, the absorbent is mixed with refrigerant and the mixture will be pumped to Generator again.

Note: Above mentioned description is more practical than theoretical (thermo dynamical) for better understanding :)

1-(chemical+water) enter a (vacuum device) and exit that device to an evaporator heat ex-changer(the same way the Freon enter the evaporator heat ex-changer in normal chillers).

2- like in  the evaporator heat ex-changer in normal chillers , in absorption chiller there are water out pipe to the system(supply) at (6 c) and return pipe from the AHU and FCU system at (12 c)

3-the (chemical+water) exit the heat ex-changer as vapor(the same way the Freon exit the evaporator in normal chillers).

4-the vapor (water+chemical)is treated by( a boiler and chemical solution and pumping and condensing) to reenter the (vacuum device) as liquid ....then repeat the cycle again.

Dear Samar,

An absorption refrigeratorr that uses a heat source (e.g.,  energy, a fossil-fueled flame, waste heat from factories) which provides the energy needed to drive the cooling process.

Absorption refrigerators are often used for food storage in recreational vehicles. The principle can also be used to air-condition buildings using the waste heat from a gas turbine or water heater. This use is very efficient, since the gas turbine then produces electricity, hot water, and air-conditioning (called cogeneration/trigeneration).

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  electricity savings, 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.