A refrigeration cycle describes the changes that take place to a refrigerant in absorbing heat and subsequently radiating it as it is circulated around a refrigerator.

Work is applied to cool a living space or storage volume by pumping heat from a lower temperature heat source into a higher temperature heat sink. Heat naturally flows in the opposite direction. Insulation is used as means to reduce the work and energy required to achieve and maintain a lower temperature in the cooled space.

The most common types of refrigeration systems use a cycle based on a phase change heat pump although absorption heat pumps are used in a large minority of applications. It is possible to build a refrigeration system which does not contain a refrigerant, and therefore do not operate a refrigeration cycle — the most common form being thermoelectric cooling used in some portable coolers.