廃熱利用高温ヒートポンプサイクルの基本性能に関する熱力学的考察

To reduce energy consumption utilizing heat recovery systems is increasingly important in industrial applications. The screening of refrigerants is discussed with a case study for high temperature heat pump cycles in this study. The overall coefficients of performance of four different cycle configurations to increase water temperature up to 160 °C using waste heat of 80 °C are thermodynamically compared for several selected refrigerants. This case study suggests that a multiple stage cycle drastically reduces throttling loss in expansion valve and exergy loss in condensers, and consequently achieves the highest overall coefficient of performance (COP) among the cases with a refrigerant having the critical temperature about the target outlet water temperature. Considering many practical benefits, also a cascade cycle that performs relatively high COP can become an expedient solution.