Absorption Refrigerator

Diagram of an Absorption Refrigerator A diagram of a common absorption style refrigeration system.

The absorption refrigerator is a common alternative to the industry dominant compression refrigerator. Unlike their compressor-based cousins, absorption refrigerators have no moving parts and require only a heat source to operate. They’re most practical in areas with limited or unavailable electrical resources. Many recreational vehicles use this style of refrigerator, utilizing the combustion engine as the heat source. Absorption refrigerators also offer a quieter, more "green" solution for refrigeration.

The primary trait that they do share with compression refrigerators is the use of refrigerant to carry heat away from the refrigerated area. The only differences being the type of refrigerant used and how it is condensed back into its liquid state.

Here’s how it works:

The liquid refrigerant (often ammonia) is sent into a compartment filled with hydrogen gas. The refrigerant reacts to the hydrogen by evaporating, absorbing any surrounding heat that it can, and causing the refrigeration effect. The refrigerant gas is directed into another compartment where it’s mixed in with water. This mixture is passed through the heat source, which boils the refrigerant out from the water. Once separated from the water, the refrigerant is cooled and is sent back into the hydrogen gas to continue the cycle.

This process was developed by Blatzar von Platen and Carl Munters, who first incorporated the 3-fluid configuration. It was also the first of its kind to be put into commercial production. Years later, Albert Einstein would come up with an alternate design, known simply as the "Einstein's Refrigerator".