Subject:- Refrigeration and Air Conditioning

Topic:- Design of air conditioning systems

Difficulty:- Low

Aqua-Ammonia absorption system:

This simple system consists of an absorber, a pump, a generator and a pressure reducing valve to replace the compressor of vapour compression system.

The other components similar to VCRS are condenser, receiver, expansion valve and evaporator. Ammonia is the refrigerant while water is used as absorbent.

The absorber absorbs the low pressure ammonia vapour coming from evaporator. The cold water in absorber has the ability to absorb very large quantities of ammonia vapour and the solution formed is called ‘aqua-ammonia’.

The absorption of vapour lowers the pressure in absorber, which in turn draws more ammonia vapour from evaporator.

The heat of solution evolved causes temperature of aqua-ammonia to increase and must be removed by a cooling arrangement in the absorber since at higher temperature water absorbs less ammonia vapour.

This strong solution formed is then pumped to generator which increases the pressure of solution up to 10 bar.

The solution is heated by some external source such as gas or steam in the generator.

During heating, the ammonia vapour is driven off the solution at high pressure leaving behind the hot weak solution in generator.

This weak solution flows back to absorber via pressure reducing valve and the high pressure vapour from generator is passed to condenser where it is condensed to high pressure liquid ammonia.

This liquid is passed to expansion valve through the receiver and then to evaporator, thus completing the cycle.