Absorption chillers collect waste heat from other processes and equipment to drive thermodynamic processes that allows water to be chilled and distributed for HVAC needs. Absorption chillers do not use mechanical compressors, instead making use of the absorption refrigeration cycle. They range in size from 20 to 1,500 tons.
According to C1S, absorption refrigeration cycles differs from vapor-compression refrigeration cycles in that the compressor is replaced by an absorber, pump and generator, while the condenser, expansion device, and evaporator are the same.
Learn more about how absorption chillers work here!
How Do Absorption Chillers Operate?
In an absorption chiller, the generator uses a high-temperature energy source, typically steam or hot water, which then flows through the tubes and boils off the refrigerant into vapor. The vapor moves to the condenser and the concentrated solution returns to the absorber. In the absorber, refrigerant vapor is absorbed by the solution and condenses into a vapor, releasing the heat it acquired in the evaporator.There are three types of absorption chillers, which are all slightly different to one another:
1. Single-Effect Absorption Chillers
In a single-effect chiller, the chilled water is cooled down once by a refrigerant from a double tray in the evaporator. The vaporized refrigerant is then absorbed into a concentrated solution, which comes from the Generator. The solution is then diluted as it absorbs the evaporated refrigerant while the heat is being absorbed into the cooling water. The diluted solution in the absorber then flows to the generator through a heat exchanger.
The hot water heats up the diluted solution and the refrigerant becomes vaporized, which then condenses and returns to the refrigerant circuit. The diluted absorbent can then be regenerated and recycled.
2. Double-Effect Absorption Chillers
A double-effect absorption chiller has the same basic components as single-effect, but also includes an additional generator, heat exchanger and pump.
Within this kind of chiller there are two cycles: a main cycle, and an auxiliary cycle. The The chilled water is cooled down twice by the refrigerant from a double tray in the evaporator and the vaporized refrigerant is absorbed into concentrated solution which is coming from the 2nd generator.
The quantity of vapor that can be absorbed is increased by the double tray system. The concentrated solution becomes a diluted solution and the heat is absorbed into the cooling water. The diluted solution in the absorber then flows to the 1st generator through a low temperature heat exchanger and a high temperature heat exchanger. The hot water then heats up the diluted solution and the refrigerant is vaporized. The absorbent solution becomes an intermediate solution in the 1st generator and it flows to 2nd generator through the high temperature heat exchanger.
The intermediate solution in the 2nd generator is then heated by the hot water and more refrigerant is vaporized in the 2nd generator. The vapor is absorbed into the solution in the auxiliary absorber, becoming aux. diluted solution. The aux. diluted solution gets delivered to aux. generator through aux. heat exchanger, and the solution is heated by hot water coming from 1st generator and becomes aux. concentrated solution. The aux. concentrated solution is delivered to aux. absorber through aux. heat exchanger. The refrigerant vapours which are generated in the 1st generator and aux. generator are condensed in the condenser and then flow into evaporator. The heat in the condenser is absorbed by cooling water.
3. Direct-Fired Absorption Chillers
Direct-fired absorption chillers are most similar to single-effect absorption chillers. The main difference is that instead of using hot water to regenerate the absorption solution, the solution gets heated directly by the gas flame to regenerate the solution and the refrigerant.
