12 TRG-TRC003-EN
notes
period two
Refrigerants

Change of Phase

This question is best answered by examining the effects of heat transfer on
water. Consider 1 lb of 60°F water. By adding or subtracting 1 Btu of heat
energy, the water temperature is raised or lowered by 1°F.
Similarly, by adding or subtracting 1 kcal (4.2 kJ) of heat energy to a 1 kg
container of 15°C water, the water temperature is raised or lowered by 1°C.
Therefore, adding 152 Btu to 1 lb of 60°F water raises its temperature to 212°F.
Although this is the boiling temperature of water at atmospheric pressure,
adding 1 more Btu will not cause all of the water to evaporate.
Similarly, adding 85 kcal (356 kJ) to 1 kg of 15°C water raises its temperature to
100°C. Although this is the boiling temperature of water at atmospheric
pressure, adding 1 more kcal (4.2 kJ) will not cause all of the water to
evaporate.
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