Refrigerants are classified according to their manner of absorption or extraction of heat from substances to be refrigerated. The classifications can be broken down into class 1, class 2, and class 3.
Class 1 refrigerants are used in the standard compression type of refrigeration systems. Class 2 refrigerants are used as immediate cooling agents between class 1 and the substance to be refrigerated. They do the same work for class 3. Class 3 refrigerants are used in the standard absorption type systems of refrigerating systems.
? Class 1: This class includes those refrigerants that cool by absorption or extraction of heat from the substances to be refrigerated by the absorption of their latent heats. Table 5-1 lists the characteristics of typical refrigerants.
? Class 2: The refrigerants in this class are those that cool substances by absorbing their sensible heats. They are air, calcium chloride brine, sodium chloride (salt) brine, alcohol, and similar nonfreezing solutions.
? Class 3: This group consists of solutions that contain absorbed vapors of liquefiable agents or refrigerating media. These solutions function through their ability to carry the liquefiable vapors. The vapors produce a cooling effect by the absorption of their latent heat. An example is aqua ammonia, which is a solution composed of distilled water and pure ammonia.
