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TRG-TRC011-EN 7
period one
Absorption Refrigeration Cycle
notes
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.
▲
◆ High affinity for water
(refrigerant)
◆ In solution, higher
boiling point than water
◆ Nontoxic
Figure 8