CH-K Series: 20, 40, 50, 60, 80, 100 Cooling with Standard Heating Capacities

 How They Work

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Yazaki gas fired DOUBLE-EFFECT chiller-heaters, with cooling capacities of 30 to 100 tons of refrigeration, are designed for commercial applications where chilled and hot water are used in a central air conditioning system. The condenser is water cooled and, during the cooling operation, heat is rejected through a cooling tower.

The Yazaki absorption chiller-heater uses a solution of lithium bromide and water, under a vacuum, as the working fluid. Water is the refrigerant and lithium bromide is the absorbent. The double-effect absorption cycle has two generators - one directly heated by a gas burner and the other heated by hot refrigerant vapor. Refrigerant, liberated by heat from the solution, produces a refrigerating effect in the evaporator when cooling water is circulated through the condenser and absorber.

High-temperature generator
The gas burner heats a dilute lithium bromide solution in the high-temperature generator and the boiling process drives the refrigerant vapor and droplets of semiconcentrated solution to the separator. The semiconcentrated solution is precooled through the heat exchanger before flowing to the low-temperature generator.

Low-temperature generator
Hot refrigerant vapor from the separator heats the semiconcentrated solution in the low-temperature generator. Refrigerant vapor, liberated from this solution, flows to the condenser while concentrated solution is precooled through the heat exchanger before flowing to the absorber.

Condenser
In the condenser, refrigerant vapor is condensed on the surface of the cooling coil and latent heat removed by the cooling water is rejected to a cooling tower, river or well. Refrigerant liquid accumulates in the condenser and then passes through an orifice into the evaporator.

Evaporator
Pressure in the evaporator is substantially lower than the pressure in the condenser due to the influence of the absorber. As the refrigerant liquid flows into the evaporator it boils on the surface of the chilled/hot water coil. Heat, equivalent to the latent heat of the refrigerant, is removed from the recirculating water which is chilled to 44.6°F. The refrigerant vapor flows to the absorber.

Absorber
A low pressure in the absorber is maintained by the affinity of the concentrated lithium bromide solution from the separator with the refrigerant vapor formed in the evaporator. The refrigerant vapor is absorbed by the concentrated lithium bromide solution as it flows across the surface of the absorber coil. Heat of condensation and dilution are removed by the cooling water. The dilute lithium bromide solution is preheated through the heat exchanger before returning to the generator.

Heating Cycle:

High-temperature generator
The solution boils in the high-temperature generator and vapor with concentrated lithium bromide solution is lifted to the separator in a manner identical to the cooling cycle.

Evaporator
Hot refrigerant vapor and droplets of concentrated solution flow through an open changeover valve into the evaporator/absorber. Some refrigerant vapor flows via the low-temperature generator and condenser before reaching the evaporator. Since the pressures in the evaporator and condenser are similar, hot refrigerant vapor condenses on the surface of the chilled/hot water coil. Heat, equivalent to the latent heat of the refrigerant is transferred to the recirculating water which is heated to 131°F.

Absorber
Liquid refrigerant mixes with concentrated lithium bromide solution to form a dilute solution and returns to the generator where the cycle is repeated.