6.IlO critical temperature of the fluid should be as high as possible, allowing a high external radiator temperature. Its freezing temperature should be well below 295°K, so that it does not solidify in the evaporator. Most important, the closed environment of the space colony makes the safety criteria imperative: the refrigerant cannot be flammable or toxic. The properties of various refrigerants are listed in references (6.I2) and (6.I6). This analysis investigates three possibilities; water, Refrigerant 11, and Refrigerant 12. VI.I.5: NUMBERS P. inputsunlight Pinputoperations Pinputlifestyle poutputhull + shield 2.79xl0 7 watts 2.0xl0 7 watts 3.6xl0 7 watts 8.6x~o 6 watts Current technology allows compressor efficiency = .85 and 6 steel rad 8 kg/m 2 15 kg/m 2 (see VI.8.2) (see VI.E) (see VI.E) (see VI.8.3) (see VI.G) (see VI .G) For simplicity of analysis, a single case is calculated for each suggested refrigerant. The evaporator temperature is taken as 280°K for all the refrigerants; the hull air enters the evaporator at 295°K. It is felt that the 15°K difference across the evaporator is the minimum acceptable to keep the size of the evaporator and the mass flow of the air reasonable.
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