Energy Efficiency Reference/Refrigeration/Technology Primer/Systems

Energy is absorbed as a liquid evaporates. This property is used in a vapor-compression refrigeration system to cool a given area, for example. High-pressure liquid enters an area to be cooled As the pressure is reduced, liquid refrigerant evaporates as it absorbs energy from its surroundings. Outside the cooled area, the refrigerant gas is compressed and rejects heat to its surroundings, condensing back to a liquid. Vapor-compression refrigeration is the most common type of refrigeration system in small to medium sized industry.

This guide addresses vapor-compression technology; types of refrigeration systems, including absorption, will not be cover. A vapor compression refrigeration system will be configured in one of the following ways.

 Single Stage (simple cycle)  The refrigerant passes in a single loop between the cooling application and the outside. Such systems cannot efficiently drop refrigerant temperatures lower than -15 degrees F. Equipment contained in the simple system is also common to more complicated systems. The following is a diagram of a simple refrigeration cycle.

 Multi-Stage  Multi-stage systems use multiple compressors in combination to achieve lower suction pressure and temperatures than possible with single-stage systems. To achieve lower suction pressure, multi-stage systems have two or more compressors.