[1]​A refrigeration unit, or "refrigeration machine", is a thermal machine designed to take heat energy from a specific area and evacuate it to another. For its operation, according to the second principle of thermodynamics,[1]​ it is necessary to apply external work, which is why the refrigerator, regardless of its operating principle, will consume energy.

In accordance with the energy requirements, a range of possibilities and configurations in refrigeration equipment are defined depending on temperature, power, air flow "Flow (fluid)"), type of installation, control volume and other variables.

From a scientific point of view, all refrigeration equipment is and is called "refrigerators" or "refrigeration machines", absolutely equivalent expressions. Commercially, classifications are made to differentiate them.

From a commercial point of view, the most common device is the domestic refrigerator (refrigerator) or refrigerator, in which the machinery (generally compression, but there are also absorption ones, running on butane gas or kerosene) manages to extract heat from a closed cabinet, transferring it to the kitchen environment, with a higher thermal level (temperature).

In order to circulate the refrigerant fluid and optimize its heat absorption, a compressor "Compressor (machine)") is used.

The minimum elements are:

Elements usually attached:

Other elements not always present are:

Another fundamental element in these devices is the heat dissipation device to the outside, which can range from a simple exchanger with a fan to a cooling tower.

They are used to lower the temperature of habitable environments. It can be done with: