It is the act of lowering the temperature of certain bodies, whether they are tubers, vegetables and meats, liquids or articles. Cold slows the growth of bacteria and freezing stops them completely, hence the cold is used to preserve food for a certain time. In the beginning, the villagers made different vases into which they introduced the food, then they buried them under a few meters and, with the low temperatures that are found below the floors, the sustenance was kept fresh for more days, in addition to the use of ice in the regions where it snowed.
There are different liquids and gases that allow the transmission of heat from one body to another, using methods such as evaporation and condensation or the exchange of sensible heat; the most used are: water, ammonia, glycol, R-11, R-22, R-23, R-24, R-134a, R-502, R-407c, R-410a, R-507, R-517. They can be classified according to their chemical composition (inorganic and organic), the level of safety they represent (ranging from grade 1 to grade 3 and each represents a level of toxicity and flammability), by their working pressure (low, medium, high, very high) and by the function they have (primary and secondary).
There are different techniques, in addition to refrigerant gases and chemical fluids, to cool bodies, such as the use of water and air as evaporants that are dispersed abroad, as well as the magnetocaloric effect, still under investigation and without commercial application. which tests the cooling procedure with the magnetocaloric effect.
Refrigeration is applied in different places and for various purposes, in homes it is applied to stabilize the temperature of the environment to make it pleasant, in medicines so that they decompose in the mouth when ingested, in industrial processes to reduce the temperature of the machines and have a correct development, as well as cryogenesis, cooling at low temperatures, for scientific research.
