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TRG-TRC011-EN 9
period one
Absorption Refrigeration Cycle
notes
The operating conditions used in this section of the clinic are approximate,
subject to variation with changing load and cooling-water temperature
conditions.
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 water
(the refrigerant) boils and condenses.
At atmospheric pressure (14.7 psia [101.3 kPa]), water boils and evaporates at
212°F [100 °C]. When the pressure is decreased, water boils at a lower
temperature. At the lower pressure, there is less force pushing against the
water molecules, allowing them to separate easier.
Just like in the vapor-compression refrigeration cycle, this change in pressure
allows the evaporator temperature to be low enough for the refrigerant to
absorb heat from the water being cooled. Likewise, it allows the condenser
temperature to be high enough for the refrigerant to reject heat to water at
normally available temperatures. Inside of the evaporator, the pressure is very
low, 0.15 psia [1.034 kPa] in this example, so that the refrigerant boils at 45ºF
[7.2ºC]. In the condenser, however, the pressure is much higher (1.5 psia
[10.34 kPa]) so that the refrigerant condenses at 115ºF [46.1ºC].
1.5
1.5
psia
psia
[10.34
[10.34
kPa
kPa
]
]
0.15
0.15
psia
psia
[1.034
[1.034
kPa
kPa
]
]
temperature
temperature
pressure
pressure
45°F
45°F
[7.2°C]
[7.2°C]
115°F
115°F
[46.1°C]
[46.1°C]
Figure 11