How it works (direct fired units)
The double effect (direct fired) absorption chiller-heater uses water as the refrigerant and lithium
bromide (LiBr) as the absorbent. It is the strong affinity that these two substances have for one
another that makes the chiller-heater cycle work. The vapor pressure of the lithium bromide
solution is lower than the vapor pressure of the refrigerant. The vapor pressure of the LiBr solution
is directly related to the amount of refrigerant (water) present in the solution with the LiBr salt and
the solution temperature. The entire absorption process occurs in almost a complete vacuum.
Figure 3: YHAU-CGN/H-CXR(M) chiller-heater cycle diagram-cooling
Evaporator
Liquid refrigerant enters the evaporator and is distributed over the top of the tube bundle. As the
refrigerant droplets cover the outside surface of the tubes, the heat from the returning chilled
water passing through the tubes causes the refrigerant to flash from a liquid to a vapor. The
temperature at which this happens depends on the evaporator shell pressure which is dictated
by the absorber section of the chiller-heater. The refrigerant vapor passes through the mist
eliminators and into the absorber section of the chiller-heater. As the liquid refrigerant passes
down through the bundle of evaporator tubes, more and more of the refrigerant vaporizes. The
refrigerant remaining in a liquid state at the bottom drains into the refrigerant tank and is pumped
back up the top of the tube bundle where the process is repeated.
15
Model YHAU-CGN/H-CXR(M)Double Effect Direct Fired Small Absorption Chiller-Heater
