Refrigeration principles and methods can be explained as below;
- Cooling by using the latent fusion heat of solid materials
- Cooling by using the latent gasification liquid materials
- Cooling by using sublimation latent fusion heat
- Cooling by using coolant mixtures
- Cooling by using mechanical methods
There are three methods applied for Refrigeration Systems
Refrigeration by Physical Methods
Liquids absorbs heat from the environment during vaporization, the temperature of heat absorbed environment decreases resulting by heat absorption from the environment. Temperature reduction occurred related to heat loss is called as refrigeration. The most important physical refrigeration method used in industry is absorption refrigeration. Silica gel and water is used as cooler in refrigeration system. Silica gel, humectants or absorber silica sodium is composed by the interaction of material acid. This compound can be washed and dried later. Silica gel placed as small granules into the refrigeration system, absorbs the ammonia. Ammonia is resolved in water easily in very low temperatures. When this solution heated at 65 ºC, it is vaporized and decomposed of water. Function of water is to decompose of ammonia in refrigeration system. System is composed of Absorption device, condenser and evaporator.
Refrigeration by Chemical Methods
Despite being in normal temperature, lower temperatures can be obtained when some chemical materials which are mixed in definite ratios to each other. For example; refrigeration is obtained at the time of mixture of snow or ice with table salt.
When % 65 snows or ice, % 35 salts (NaCl) is mixed, initial temperature is 0 ºC; mixture temperature is 20 ºC.
%60 snow or ice, % 40 initial temperature of salt 0 ºC, mixture temperature is 30 ºC.
Refrigeration by Mechanical Methods
The process of Refrigeration by Mechanical Methods is based upon the increase of pressure and temperature of coolant. This refrigeration method works based on the principal of Thermodynamics -second rule of inverted Carnot Cycle.