Secondary Refrigerants
Secondary refrigerants play a role in carrying heat from an object or space, is cooled by the refrigerant or evaporator cooling system. During this process, the secondary refrigerant has no phase change. In the past, the most common secondary refrigerants were brines that are water-salt (e.g., sodium chloride, calcium chloride) solutions, and even today they are still used, despite their corrosive effect. In addition, non-freezing liquids, solutions and ethylene glycol, propylene glycol, or calcium chloride is widely used as a secondary refrigerants. These fluids, propylene glycol has a unique feature safe when in contact with food products. Ten years ago dichloromethane (CH2Cl2), trichloroethylene (C2HCl3), alcoholic solutions, and acetone were also used in some special applications. The following functions are considered as main criteria in choosing the right secondary refrigerant (Dincer, 2003).
- satisfactory thermophysical properties,
- stability,
- noncorrosiveness,
- nontoxicity,
- low cost, and
- usability.
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