The basic working principle of a freezer is evaporation. When a liquid evaporates it causes the surrounding area to cool. A vapor compression cycle is used in most freezers. In this cycle, a circulating refrigerant enters a compressor as low-pressure vapor at or slightly above the temperature of the freezer interior. The vapor is compressed a-nd exits the compressor as high-pressure superheated vapor. The superheated vapor travels under pressure through coils or tubes that make up the condenser; the coils or tubes are passively cooled by exposure to air in the room. The condenser cools the vapor, which liquefies. As the refrigerant leaves the condenser, it is still under pressure but is now only slightly above room temperature. This liquid refrigerant is forced through a metering or throttling device, also known as an expansion valve (essentially a pin-hole sized constriction in the tubing) to an area of much lower pressure. The sudden decrease in pressure results in explosive-like flash evaporation of a portion (typically about half) of the liquid. The latent heat absorbed by this flash evaporation is drawn mostly from adjacent still-liquid refrigerant, a phenomenon known as auto-refrigeration. This cold a-nd partially vaporized refrigerant continues through the coils or tubes of the evaporator unit. A fan blows air from the freezer compartment ("box air") across these coils or tubes a-nd the refrigerant completely vaporizes, drawing further latent heat from the box air. This cooled air is returned to the freezer compartment, a-nd so keeps the box air cold.

Vapor compression refrigeration is one of the many refrigeration cycles. It is widely used in domestic a-nd commercial freezers, large scale warehouses for chilled or frozen storage of foods a-nd meats, refrigerated trucks a-nd railroad cars, a-nd a host of other commercial a-nd industrial services. For example, ice cream production.