Vapour Absorption Refrigeration System

Introduction The vapour absorption refrigeration system is one of the oldest

methods of producing refrigerating effect The principle of vapour absorption was first discovered by Michael

Faraday in 1824 The first vapour absorption refrigeration machine was developed

by French Scientist, Ferdinard Carre, in 1860.  In this system ammonia is used as the refrigerant and water is

used as the absorbent. 

Comparison of VAR with VCR : The absorption system differs fundamentally from vapour

compression system only in the method of employed for compressing the refrigerant.

In the absorption system, the compressor is replaced by an absorber, generator and a pump.

The vapour absorption system uses heat energy, instead of mechanical energy as in vapour compression system, in order to change the conditions of the refrigerant for the operation of the refrigeration cycle.

The major drawback of the vapour compression refrigeration system is that it requires large volume of refrigerant vapour which requires large mechanical power for its operation.

Principle of Vapour Absorption System There is the peculiar property of some substances to have affinity

for another substances at some temperature and pressure conditions and less affinity at another conditions.

This idea for the working principle of a vapour absorption system was generated by Michael Faraday in 1824.

He knew that silver chloride (AgCl)m a white powder , had a property of absorbing large amount of ammonia gas at the normal temperature and pressure.

. Two chambers are combined with the help of a tube. The white powder was kept inside the first chamber to which

ammonia gas was supplied and sealed. The powder was heated up while other end was cooled using

circulating water. Liquid ammonia was obtained in the cool end of the apparatus. After

stopping heat, it was observed that, the liquid ammonia instead of sitting there, started boiling( bubbles produced) and vapour was reabsorbed by the white powder.

Upon touching the boiling end , it was astonished to find that the vessel was very cold.

He repeated the experiments and cooling was observed again.

This led to invention of the intermittent Vapour absorption system having solid as an absorber

Simple Vapour Absorption System

Practical Vapour AbsorptionSystem

Coefficient of Performance

Domestic Electrolux (Ammonia Hydrogen) Refrigerator The domestic absorption type refrigerator was invented by two

Swedish engineers, Carl Munters and Baltzer Von Planton, in 1925 This type of refrigerator is also called as “Three-Fluid Absorption

System“ The main purpose of this system is to eliminate the pump so that in

the absence of moving parts, the machine becomes noiseless. The three fluids used in this system are water, ammonia and

hydrogen. The system cannot be used for industrial purposes as the COP of

the system is very low.

Domestic Electrolux (Ammonia Hydrogen) Refrigerator

Advantages of VA Systems No moving part except pump which has a small motor, which is

comparatively smaller than compressor system results in Quiet operation and low maintenance.

The vapour absorption system uses heat energy to change the condition of the refrigerant from the evaporator where as vapour compression uses mechanical energy to change the condition of the refrigerant.

Can be built for huge working capacities. (even for above 1000 TR)

Can be operated at designed C.O.P’s or even at part loads by varying generator temperature.

Space and Auto. control requirements favour absorption system.

Disadvantages of VA Systems Efficiency is low Takes long time to produce cooling effect Kerosene/oil/gas flame gives bad smell. Due to the low working pressure, the COP of vapour

refrigeration is low (nearly 1.1). Initial cost of the equipment is high in case of Practical

Vapour Absorption system.

THANK YOU

BYG.Jaswanth