压缩式热泵系统火用效率定义方法初探

对压缩式热泵系统(火用)效率的定义式进行了分析,指出了该定义式在实际应用过程中存在的一些不足.即当低温热源为环境时,此定义式合理,否则即使热泵系统内部可逆,系统火用效率仍不为1,文中对产生这一问题的原因进行了分析.以热泵系统的火用平衡方程为依据,参照火用效率定义方法及火用效率的基本特征,对压缩式热泵的系统(火用)效率进行了重新定义.通过对两个不违背火用效率定义特征的表达式的对比分析,确定了热泵系统合理的(火用)效率表达式.最后说明,在压缩式制冷系统中当高温热源不为环境时,(火用)效率定义也存在同样缺陷,改进方法与本文类似.

Preliminary Exploratory Study of a Method for Defining the Exergy Efficiency of a Compression-type Heat Pump System

After an analysis of the method for defining the exergy efficiency of a compression-type heat pump some deficiencies of such a definition during its practical use are pointed out. This means that in an environment of low-temperature heat source the definition under discussion has been found to be rational. Otherwise, even with an endo-reversible heat pump system the exergy efficiency of the system will still not be "unity". The cause which gives rise to such a problem is analyzed. By adopting the exergy balance equation or the heat pump system as a basis and referring to the basic characteristics of exergy efficiency and its definition method the exergy efficiency of a compression-type heat pump is defined once again. Through a contrast analysis of two expressions not contradictory to the exergy-efficiency definition characteristics determined is a rational expression of the exergy efficiency for the heat pump system. In conclusion, it is noted that in the absence of an environment of high-temperature heat source for a compression-type refrigeration system the same defect may emerge with regard to the definition of the exergy efficiency. In such a case a similar method for coping with the defect can be put into use.