Abstract
This paper deals with an availability analysis of heat pumps. For a fundamental heat pump cycle, flows of exergy are derived and are drawn on a temperature-entropy chart. The expansion process of heat pump cycle is irreversible throttling process, and thus the irreversible loss is generated in comparison with the reversible isentropic expansion. Other irreversible losses are generated in the compression process and the heat exchangers. The effect of irreversibility in compression process and heat exchangers on the coefficient of performance is qualitatively estimated. The energy conservation law will force the coefficients of performance of air-conditioners to higher levels. From a viewpoint of human comfort, excessively high coefficient of performance makes residents uncomfortable due to high humidity in cooling mode and low temperature draft in heating mode. The harmony between energy conservation and human comfort is important for a development of air-conditioners.
