The Choice of Refrigerant

As shown in Sec. 5.2, the efficiency of a Carnot heat engine is independent of the working medium of the engine. Similarly, the coefficient of perfomianee of a Carnot refrigerator is 

Temperature C K Saturation pressure MPa Liquid density kg Specific volume of vapor kg- Enthalpy kJ kg- Entropy kJ kg- K  

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Now consider the main factors affecting the choice of refrigerant for compression refrigeration. 

The application of activated carbons in adsorption heat pumps and refrigerators is discussed in Chapter 10. Such arrangements offer the potential for increased efficiency because they utilize a primary fuel source for heat, rather than use electricity, which must first be generated and transmitted to a device to provide mechanical energy. The basic adsorption cycle is analyzed and reviewed, and the choice of refrigerant-adsorbent pairs discussed. Potential improvements in cost effectiveness are detailed, including the use of improved adsorbent carbons, advanced cycles, and improved heat transfer in the granular adsorbent carbon beds. 

Section 9.1.7.1 on chlorine liquefaction briefly describes the typical mechanical refrigeration cycle. Several different types of compressor appear in water chillers. They include reciprocating, screw, and centrifugal machines. The best choice depends very much on the suitability of a manufacturer s package details. The choice of refrigerant is not constrained by reactivity, as in the case of chlorine compression. 

The East Ohio plant used water, ammonia, ethylene, and methane. The Chicago District Pipeline plant was to have used water, propane, ethylene, methane, and nitrogen. A major consideration in the choice of refrigerants, aside from that of efficiency, is ease of replacement should a charge be lost. At some foreign locations it would be advisable to use refrigerants which could be derived from the charge stock itself. 

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