Trane TRG-TRC011-EN manual Conditions

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.

115°F
[46.1°C]
temperature
45°F
[7.2°C]	0.15 psia		1.5 psia
	[1.034 kPa]		[10.34 kPa]
		pressure	Figure 11

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].

TRG-TRC011-EN 9