Civil Engineering Reference
In-Depth Information
a
b
Fig. 12.2
Diagrams of vapor-compression refrigeration cycle: (a) Temperature-entropy diagram,
(b) pressure-enthalpy diagram
A temperature-entropy or a pressure-enthalpy diagram can be used to represent
the cycle. Both are shown in Fig.
12.2a, b
.
The four phases of the cycle are described below.
12.2.1 Vaporization (Process from 4 to 1
0
or 1)
When the refrigerant, as a two-phase liquid-vapor mixture, passes through the
evaporator, it absorbs heat from the cold space (cold region) and changes into
saturated vapor at point 1
0
. This happens at constant pressure and temperature.
Evaporator temperature must be lower than cold space temperature (cold-region
