20 TRG-TRC003-EN
notes
period three
Refrigeration Cycle
At higher pressures, refrigerant boils and condenses at higher temperatures.
This can be explained by examining the properties of water.
At atmospheric pressure (14.7 psia [0.10 MPa]), water boils and evaporates at
212°F [100°C]. When pressure is increased, however, water does not boil until it
reaches a much higher temperature. At a higher pressure there is a greater
force pushing against the water molecules, keeping them together in a liquid
phase.
Recall that, at a given pressure, the temperature at which a liquid will boil into a
vapor is the same temperature at which the vapor will condense back into a
liquid.
This curve illustrates the pressures and corresponding temperatures at which
R-22 boils and condenses. At a pressure of 85 psia [0.59 MPa], the liquid R-22
will boil at 41.2°F [5.1°C]. As an example, assume that a compressor is used to
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