Absorption Refrigeration Cycle

Absorption cycles are similar to vapor compression cycle systems, but rely on the chemical affinity of an absorbent for the refrigerant to produce the cooling effect. The cycle is best understood by examining the functions of four major components: absorber, generator, condenser, and evaporator. The system is illustrated in Figure 38-1 and described as follows:

In the absorber, low-pressure refrigerant vapor is condensed and absorbed by the warm, concentrated absorbent solution. Absorption (mixing) is made possible because of the affinity between absorbent and refrigerant molecules. The heat of condensation and heat of absorption are removed from the absorber tube bundle by cooling water to an external heat rejection system. After the refrigerant vapor and the strong solution combine, the solution has a lower concentration and is referred to as a weak solution. Its pressure is then elevated as it is pumped into the generator.

In the generator, heat is introduced and the refrigerant and absorbent are separated (refrigerant is regenerated) by a boiling process. Hot concentrated solution is cooled by a heat exchanger using incoming weak solution as it leaves the generator and is throttled back to the absorber.

High-temperature/high-pressure refrigerant vapor flows to the condenser where it condenses to liquid as heat is rejected. Except in certain small capacity systems, water-cooled condensers are used. Warm liquid refrigerant is then expanded through an orifice and enters the evaporator where it vaporizes at

Heat, Input

(Weak Solution)

Solution Pump

Cooling 1 Tower 4 Water (Inlet)

Generator

Condenser

Generator

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