热源自调节有机朗肯循环发电系统热力性能分析

Analysis of the Thermodynamic Performance of a Heatsource Self-regulated ORC (Organic Rankine Cycle) Power Generation System

为提高基本ORC(有机朗肯循环)系统换热器内冷热流体换热温差匹配程度,提升系统热力性能,提出一种ORC-R(热源自调节有机朗肯循环发电)系统,基于热力学第一定律和第二定律,建立了系统的数学模型并编制计算机程序进行分析,研究表明:当热源与有机工质换热温差不匹配时,采用热源自调节方式可有效提升基本ORC系统热力性能;热源自调节系数不同,ORC-R系统热力性能提升程度不同,存在随热源温度不同而有所变化的极限调节值;同时,ORC-R系统较基本ORC系统达到性能最优值时的蒸发温度降低,ORC-R系统净输出功、火用效率随热源自调节系数增加呈现先增加后减小的变化规律,可找到热源自调节系数的最佳值使ORC-R系统热力性能达到最优;热源温度Tg=373、383、393和403 K时,ORC-R系统净输出功Wnet较基本ORC系统分别增加35.52%、42.75%、51.15%和57.63%;ORC-R系统火用效率ηex分别为基本ORC系统的0.879 9倍、1.174 9倍、1.485 8倍和1.807 8倍。

To enhance the extent of the matching between the heat exchange temperature differences of the cold and hot fluids inside a heat exchanger in a basic ORC system and improve the thermal performance of the system,proposed was a heat source self-regulated ORC power generation system. On the basis of the first and second law of the thermodynamics,a mathematical model for the system was established and an analysis was performed by preparing a computer program. It has been found that when the heat source is not matching with the heat exchange temperature differences of the organic working media,to adopt the heat source self-regulation mode can effectively improve the thermal performance of the basic ORC system. When the self-regulation coefficient of the heat source differs,the extent to improve the said thermal performance of the heat source self-regulated ORC system will also vary and there will be a regulation limit value changing with the heat source temperature. At the same time,the vaporization temperature of the heat source self-regulated ORC system will decrease when compared with that of the basic ORC system to obtain the optimal performance. The net output power and the exergy efficiency of the heat source self-regulated ORC system will assume a variation law of first increase and then decrease with an increase of the self-regulation coefficient of the heat source. An optimum value of the self-regulation coefficient of the heat source can be found to optimize the thermal performance of the heat source self-regulated ORC system. When the heat source temperature Tg= 373,383,393 and 403 K,the net output power Wnetof the heat source self-regulated ORC-R system will increase by 35. 52%,42. 75%,51. 15% and 57. 63% respectively when compared with that of the basic ORC system and its exergy efficiency ηexwill be 0. 8799,1. 1749,1. 4858 and 1. 8078 folds of that of the basic ORC system respectively.