| In recent years，with worsening of worldwide energy shortage, waste of resourcesand environmental issues, many countries in the world are studying and developing therelevant technical theory and regulatory policies to alleviate and deal with this issue.Organic Rankine Cycle based on low-grade heat utilization is an effective measure toreduce energy fuel consumption and energy conservation, ORC become a hot researchand core subjects of scholars, research institutions, institutions of higher learning fromvarious countries. Using CCHP, CCP, CHP cycle is an effective way to improve theefficiency of the ORC system based on low-grade heat utilization. The working fluid ofORC system is usually a low boiling organic compounds which have a certain influenceon the environment. These organic working fluids have more or less the potential valueof GWP, ODP which have influence on the environment, and in the production andtransportation process, the working fluid also may cause some environmental pollution.When ORC system is running, the leak of working fluid will exacerbate global warmingand Ozone depleting. Currently, the evaluation of ORC system in concentrated on theefficiency of thermodynamic cycle and thermal economic performance, although someliterature consider the environmental performance during choose the working fluids,don`t quantitative analyze the environmental impact of the working fluid, and theevaluation index does not take into account the thermal economic and environmentalimpact. Based on the analysis of the basic performance of the ORC system, the paperestablished a CCHP system with the transcritical ORC system, the exergy parameter isused to quantify the environment influence of the working fluids, a comprehensiveevaluation index is studied to evaluate to the ORC system.In this paper, the analysis and research from the following aspects：(1) The basic performance of the subcritical and transcritical ORC system isanalyzed, the contribution of ORC system with low-grade heat to save energy andresources and reduce greenhouse gas emissions of conventional thermal power plants isanalyzed.(2) There was environmental influence of work fluid of ORC system and existingstudies are not to quantitative analyze of the environmental influence of work fluid ofORC system. The ORC system with shell-and-tube heat exchanger is established, andthe model of liquid-filled and leak of ORC system is analyzed. Environmental impact is quantified by exergy, the exergy cost of environment influence of the subcritical andtranscritical ORC system is studied.(3) The comprehensive evaluation index considered the environmental influenceand thermal economic performance is defined and the relationship of comprehensiveexergy efficiency integrated environmental influence is derived. The rationality ofcomprehensive exergy efficiency integrated environmental influence is explainedthrough theoretical analysis and case study. The influence of exergy cost ofenvironmental influence to exergy efficiency ORC system is compared and analyzed.(4) A model of combined cooling, heating and power(CCHP) system withtranscritical ORC system, based on which influences of following factors on the systemperformance is analyzed, such as the inlet pressure and temperature ofhigh/low-expander. The environmental influence of transcritical ORC system isanalyzed by examples. |
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