Trane TRG-TRC003-EN User Manual

TRG-TRC003-EN

notes

period four

Pressure–Enthalpy Chart

The distance between the edges of the envelope indicates the quantity of heat
required to transform saturated liquid into saturated vapor at a given pressure.
This is called the heat of vaporization.

For example, B represents the enthalpy of saturated liquid water at 14.7 psia
[0.10 MPa] and C represents the enthalpy of saturated water vapor at the same
pressure. The difference in enthalpy between B and C—970 Btu/lb
[2256.3 kJ/kg]—is the heat of vaporization for water at this pressure.

The P-

h chart can be used to analyze the vapor-compression refrigeration cycle

and determine the conditions of the refrigerant at any point in the cycle. The
chart in this example is for R-22.

Because the refrigeration cycle is a continuous process, defining the cycle can
start at any point. This example begins in the lower left-hand portion of the P-

chart, where the refrigerant enters the evaporator.

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