Why do refrigerants have a high latent heat of vaporization?
Refrigerants do not have as high a latent heat of vaporization as water (for any ratio of pressure/critical pressure). Water would be a perfect fluid for use as a refrigerant if it didn't freeze at zero Celsius (but if it had any lower a melting point we might not have even evolved on Earth). So, water and steam are good for use in building a power plant, but not good for use in building a refrigerator. Refrigerants do perhaps have high latent heats of vaporization compared to most alcohols. High latent heat of vaporization is an asset for refrigerants, because most of the heat absorption and heat rejection in the vapor-compression refrigeration cycle occurs as a phase change. Hence why the heat absorption and heat rejection heat exchangers are called the evaporator and the condenser respectively. The phase changes chosen happen at different pressures, so it is important to realize that multiple values of heat of vaporization come in to play, since heat of vaporization varies with pressure.
