热功转换循环规律的另一半:逆循环的定理、定律和核心物理量  

The other half of the principle of heat-work conversion cycles:The theorem,principle and core physical quantity of reversed cycles

作　　者：过增元[1] 赵甜[1] 薛提微 Zengyuan Guo;Tian Zhao;Tiwei Xue(Key Laboratory for Thermal Science and Power Engineering of Ministry of Education. Department of Engineering Mechanics, Tsinghua University,Beijing 100084, China)

机构地区：[1]清华大学工程力学系热科学与动力工程教育部重点实验室,北京100084

出　　处：《科学通报》2019年第5期600-610,共11页Chinese Science Bulletin

基　　金：国家自然科学基金创新研究群体项目(51621062)资助

摘　　要：在回顾卡诺定理、热力学第二定律(正循环等价定律)以及核心物理量熵时,发现它们主要讨论的都是热量通过可逆循环转换为功量的规律.即使对于热泵或制冷逆循环,仍然应用正循环的概念和分析方法讨论它们的性能.然后以逆卡诺循环为例,分析和证明了两温限下逆卡诺循环的性能系数不是最大而是最小.随之提出了一个新的逆循环,它是由两个等压和两个等容过程组成,可称之为逆压容(p-V)循环.在净功量给定和两温限条件下,逆压容(p-V)循环的性能系数远大于逆卡诺循环的性能系数.此结果表明,逆循环中功量是有品位的,压力就是功量的品位.最后建立了逆循环的等价定律和逆循环等式,并引入了功熵的概念.基于逆循环的原理、定理、定律、核心物理量和循环性能等,可望形成热功转换循环规律的另一半.Engineering thermodynamics mainly focuses on the principles and methods for the heat-work conversion and to improve heat-work conversion efficiency. In current literatures, discussions are mainly focused on the heat-work cycles, which converts heat to work. Besides, the core physical quantity of heat-work cycles is entropy, which presents the heat-work conversion ability of the system. As for reversed cycles, the discussions are not quite detailed, and most of them applied the theory for heat-work cycles directly on reversed cycles. However, it’s well known that heat cannot be fully converted to work in a reversible thermodynamic cycle, which leads an efficiency less than 1. For reversed cycles, the heat output from the cycle can be much more than the net work the cycle costs, which derives a coefficient of performance(COP) more than 1. This phenomenon implies the principles of heat-work conversion in ordinary heat-work cycles and reversed cycles are somehow different, and some problems are naturally drawn as follows:(1) Is the COP of the reversed Carnot cycle the maximum possible COP for all reversed cycles within two temperature limits?(2) Heat can be judged from its quality, i.e. its temperature, and does the mechanical work have its quality? To answer these questions, this work analyzed and discussed the theorem, principle, and core physical quantity of reversed thermodynamic cycles. First, the principle for ordinary thermodynamic cycles are briefly reviewed, including the Carnot theorem and its proof, and the derivation of the concept of entropy from the Clausius’ original approach. Second, current conclusions of reversed cycles are reviewed and the air compression refrigeration cycle is taken as an example. The analysis comparing two cycles within given temperature limits presented that for given two temperature limits, the COP of the reversed Carnot cycle is the minimum possible COP, which is different from current conclusions. The quality of volumetric work is then discussed, and a new reversed cycle

关 键 词：逆循环 熵 性能系数 逆卡诺循环 

分 类 号：O414.1[理学—理论物理]