In ancient Greece, slaves were used to transport snow from the mountains, which were stored in straw and used in the hot summer months. The Egyptians placed pots made of porous material, filled with water outside their homes at night. The cold desert wind cooled the water by evaporating the moisture.
Currently, we have the means to produce refrigeration in any season, but it was from 1923 onwards that refrigeration took its greatest impulse with the advent of the mechanical unit, ranging from the manufacture of ice cream to the preservation of milk and perishable products.
Refrigeration can be produced in several ways, but the simplest way would be to keep in contact two substances, one hot and one cold. The heat flowing from the hottest to the coldest will provide, at a given moment, a thermal equilibrium, that is, it will equal the temperature of both substances. This is what happens when we put a glass of hot milk to cool in a container with cold water. The milk gives heat to the water, which in turn will heat up until both reach the same temperature level.
It should also be noted that refrigeration is not a process of adding cold, as is commonly thought, but rather of removing heat. The domestic refrigerator does not add cold to the interior of the cabinet, but removes the heat from the food stored in it.
