Trane TRG-TRC011-EN manual High affinity for water refrigerant

period one

Absorption Refrigeration Cycle

notes

▲

◆High affinity for water (refrigerant)

◆In solution, higher boiling point than water

◆Nontoxic

Figure 8

Additionally, the absorption refrigerant cycle uses a second fluid called an absorbent solution. The absorbent solution is confined to the absorber and generator sections of the cycle, and is used to carry the refrigerant from the low-pressure side (evaporator) to the high-pressure side (condenser) of the chiller. For this purpose, the absorbent should have a strong affinity (attraction) for the refrigerant and, when in solution with the refrigerant, a boiling point that is substantially higher than that of the refrigerant.

The absorbent commonly used with water (the refrigerant) is lithium bromide. Lithium bromide, a nontoxic salt, has a high affinity for water. Also, when in solution with water, the boiling point of lithium bromide is substantially higher than that of water. This makes it easy to separate the refrigerant from the absorbent at low pressures. A certain quantity of absorbent solution, therefore, is pumped from the absorber to the generator in order to transport the refrigerant.

Another common refrigerant–absorbent pair is ammonia as the refrigerant and water as the absorbent. These fluids are more common in small residential applications. There are other refrigerant–absorbent combinations; this clinic, however, will focus on water as the refrigerant and lithium bromide as the absorbent.

TRG-TRC011-EN 7