A refrigeration system is a mechanical process or arrangement that is responsible for lowering the temperature between two points. For this process to take place, the thermodynamic properties of matter are involved, which are responsible for transferring thermal energy or heat between two points.

The main difference between a system and a refrigeration circuit is the complexity of the circuit, as systems are only a simple arrangement of the circuit, in which other variables such as mass balance, energy, heat transfer, etc. become more important.
There are two basic configurations of a refrigeration system depending on the method of refrigerant injection or its construction.
Compression refrigeration
It is based on the operation of the mechanical energy of the circuit through the compression of a refrigerant fluid. When it condenses, this fluid gives off latent heat at a lower temperature than that which was absorbed when the refrigerant itself evaporated. The compression of the refrigerant fluid in the compressor is responsible for maintaining the cycle which, after passing through the evaporator, the expansion valve and the condenser, is subsequently repeated, passing through different pressures and therefore different temperature conditions.
Absorption refrigeration
Its operation is the same as in compression refrigeration, since it involves producing cold through the transfer of heat by means of changes in the state of certain refrigerant fluids. In this case, it is not the compressor that is the key aspect but the properties of the refrigerant fluid, which is able to absorb the properties of another substance in the vapour phase…
Examples of such substances are lithium bromide, ammonia or water in vapour phase, although this method is usually only used when there is a cheap or waste heat source, because it is an economical method, but not very efficient, since, depending on the fluid used, it cannot cool to temperatures below the freezing point of water, for example.