Absorption Operation Cycle

Figure 17-8 is a schematic diagram of an absorption cold generator. Note that the evaporator, absorber, concentrator, and condenser are enclosed in a single casing. The heat exchanger is located externally below the main shell.

• Evaporator. The evaporator pump circulates the refrigerant (water) from the refrigerant pump into the spray trees. To utilize the maximum surface for evaporation, the refrigerant is sprayed over the evaporator tubes. As the spray contacts the relatively warm surface of the tubes carrying the water to be chilled, a vapor is created. In this manner heat is extracted from the tube surface, chilling the fluid in the tubes. The vapor created in this process passes through eliminators to the absorber.

• Absorber. The lithium-bromide solution (under proper conditions) keeps the pressure in the absorber section low enough to pull the refrigerant vapor from the high-pressure evaporator. As the vapor flows into the absorber, it mixes with the absorbent solution being sprayed over the tube bundle.

• Heat exchanger. The heat exchanger is used only asan economizer. The cool diluted solution from theconcentrator pump is heated by the hotter concentratedsolution moving from the concentrator to theabsorber steam or hot water (heating medium) is conserved. The heat transfer in the heat exchanger brings the temperature of the diluted solution closer to the boiling point. It also brings the concentrated solution temperature closer to the absorber temperature.

• Concentrator. Steam or high-temperature water entering the concentrator is controlled to boil off the same quantity of refrigerant picked up by the absorber. The refrigerant vapor is given up by boiling the solution in the concentrator. The vapor passes through eliminators to the tube surface of the condenser.

• Condenser. The refrigerant vapor from the concentrator is condensed on the tube surface of the condenser and falls into the pan below the tube bundle.

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