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32 TRG-TRC011-EN
notes
period two
Absorption Chiller Types
An alternate method is to use the evaporator as a condenser in the heating
mode. In this example chiller, by switching the cooling/heating changeover
valve the chiller switches to heating mode, and hot water can be delivered using
the same piping system that was used to supply chilled water in the cooling
mode. The cooling tower and refrigerant pumps can typically be shut off.
In the direct-fired high-temperature generator, heat that is generated by the
combustion process causes the refrigerant to boil and separate from the
absorbent solution. As the refrigerant boils away, the absorbent solution
becomes concentrated and returns to the absorber.
The refrigerant vapor produced by the high-temperature generator flows into
the evaporator. Heat is transferred from the hot refrigerant vapor to the water
flowing inside the evaporator tubes, causing the refrigerant to condense on the
tube bundle and fall into the evaporator pan. This condensed liquid refrigerant
then overflows into the absorber section where it is absorbed by the lithium
bromide solution.
The resulting dilute absorbent solution is preheated as it is pumped through the
low- and high-temperature heat exchangers, eventually returning to the high-
temperature generator to repeat the cycle.
The advantage of this design is that no additional bundle is required for heating
mode. This chiller, however, can only operate in cooling mode or heating
mode—no simultaneous operation is possible.
hot
hot
water
water
high-temperature
high-temperature
generator
generator
refrigerant
refrigerant
vapor
vapor
evaporator
evaporator
absorber
absorber
changeover
changeover
valve
valve
Figure 37