The refrigerant that is typically used in an absorption chiller is distilled water and the absorbent is lithium bromide. These two fluids, the refrigerant
An introduction to the absorption refrigeration cycle

Absorption cycle versus vapour-compression cycle

There are two fundamental differences between the absorption refrigeration cycle and the vapour-compression refrigeration cycle with which we are more familiar. The first difference is that the compressor is replaced by an absorber, a pump and a generator. The second is that, in addition to the refrigerant, the absorption refrigeration cycle uses a secondary fluid, called the absorbent. The condenser, expansion device, and evaporator sections, however, are the same.

Refrigerant solutions and the absorbent, are mixed inside the chiller in various concentrations. The term dilute solution refers to a mixture that has a relatively high refrigerant content and low absorbent content. A concentrated solution has a relatively low refrigerant content and high absorbent content. An intermediate solution is a mixture of dilute and concentrated solutions.

The absorption refrigeration cycle

The four basic components of the absorption refrigeration cycle are the generator and condenser on the high-pressure side, and the evaporator and absorber on the low-pressure side. The pressure on the high-pressure side of the system is approximately ten times greater than that on the low-pressure side.

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Starting on the high-pressure side of the cycle, the purpose of the generator is to deliver the refrigerant vapour to the rest of the system. It accomplishes this by separating the water (refrigerant) from the lithium bromide-and-water solution.

In the generator, a high-temperature energy source, typically steam or hot water, flows through tubes that are immersed in a dilute solution of refrigerant and