The Choice Of Refrigerants

• ozone - friendly environment,
• low boiling point,
• low consumption per unit of power,
• evaporation pressure below atmospheric pressure,
• high heat of vaporization,
• nonflammable and not explosive,
• supply of industrial nontoxic,
• nonreactive and nondepletive with lubricating oil of the compressor,
• nonacidic in the case of a mixture with water or air,
• chemically resistant,
• suitable thermophysical properties (e.g., thermal conductivity, viscosity),
• commercially available
• easily detectable in the case of a leak, and
• low cost.

When you select a refrigerant, saturation properties of the refrigerant must be taken into account. Heat transfer at a reasonable rate, the difference of temperatures from 5 to 10 C should be maintained between the refrigerant and the environment with which it exchanges heat. If refrigerated space will be maintained at the level of 0 C, for example, the temperature of the refrigerant should remain at about -10 C, while it absorbs heat in evaporator. Low pressure in the refrigeration cycle occurs in the evaporator, and this pressure should not be higher than the atmospheric pressure to prevent any leakage of air cooling system. Therefore, the refrigerant must have the saturation pressure of 1 ATM or above -10 C in this case. Ammonia and R-134a are two such substances. Also, the temperature (and, thus, the pressure in the refrigerant side of the capacitor depends on the environment in which heat is rejected. Below the temperature of the condenser (thus higher COP) can be saved if the refrigerant is cooled below the temperature of the medium, such as liquid water (Cengel and boles, 2008)...