Working fluids optimization based on economy analysis and exergy efficiency for low-temperature organic Rankine cycle

doi:10.16085/j.issn.1000-6613.2016.02.005

Abstract

Abstract: A comprehensive evaluation criterion combined economic performance and exergy efficiency has been used for the working fluids optimization of organic Rankine cycle (ORC). The objective function of economic performance is defined as the ratio of the required heat exchanger area to the total output power,and the comprehensive evaluation function is the weighted sum of the objective function of economic performance and the exergy efficiency. In the calculation,the heat source of the ORC system is 95℃ geothermal water,and the heat inputs are identical. The working fluid used in the system is varied and the evaporating temperature or condensing temperature is changed in each calculation process. The objective function values and the exergy efficiency are calculated and then the comprehensive evaluation function values of them become available. The results show that from the point of view of economic performance,each system has an optimum evaporation temperature. The economic performance rises with the decrease of condensing temperature and the relation between them is quadratic. In the ranges of evaporating temperature and condensing temperature,R113 and R245ca present better economic performance than other work fluids while the exergy efficiency of R161 is highest. The comprehensive evaluation function shows that the R161 has the best working performance.

Key words: organic Rankine cycle, economic performance, exergy efficiency, objective function, organic work fluid, optimization

摘要： 采用一种结合了经济性能和(火用)效率的综合评价指标对有机朗肯循环(organic Rankine cycle,ORC)工质进行多目标优选。定义经济性目标函数为系统所需总换热面积和净输出功的比值,而综合评价函数为经济性目标函数和(火用)效率的加权和。在该计算模型中,以95℃地热水为ORC系统热源,输入相同的热量。分别计算采用十几种不同工质的ORC系统在所选蒸发温度和冷凝温度变化范围内的经济性目标函数和(火用)效率,继而得出两者的多目标综合评价函数。计算结果表明:从经济性的角度来看,系统存在最佳蒸发温度;系统经济性随冷凝温度的降低而提高,两者呈二次函数关系;所选的多种工质在该温度变化范围内相比较,R113、R245ca具有较好的经济性能,R161的(火用)效率较高,而综合评价函数的结果表明R161具有较优的性能。

关键词: 有机朗肯循环, 经济性能, ?效率, 目标函数, 有机工质, 优化

CLC Number:

TK12

LI Weiyi, GAO Jing, LI Zishen, ZHANG Haijia. Working fluids optimization based on economy analysis and exergy efficiency for low-temperature organic Rankine cycle[J]. Chemical Industry and Engineering Progree, 2016, 35(02): 369-375.

李惟毅, 高静, 李子申, 张海佳. 基于经济性和效率的有机朗肯循环工质优选[J]. 化工进展, 2016, 35(02): 369-375.

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