Evaluate And Optimize To Combined Heating And Power-Organic Rankine Cycle System With Low Grade Heat Source

Currently, the Combined Heating and Power (CHP) system which based onOrganic Rankine Cycle (ORC) is a rapid developing technology about thecomprehensive utilization of energy. The solar, geothermal, biomass and otherlow-grade heat resources driving small scale CHP-ORC system in living communitiesand commercial buildings provide the ideal heat and electricity for the consumers. It canrise the energy utilization efficiency and reduce the consumption of fossil fuels with theapplication of this novel system. In addition, the greenhouse gas emission is decreasing.Consequently, the CHP-ORC system has a greater advantage on the economic andenvironmentally friendly than traditional energy utilization systems.In this thesis, I focus on acknowledging and characterizing of small-scaleCHP-ORC working for buildings. Three CHP-ORC systems (back pressure, externalheat pump and built-in heat pump type CHP-ORC system) are optimized and evaluatedby using energy efficiency analysis method. The energy efficiency metrics of the threeCHP-ORC systems is calculated by the different vapor temperature.The selection metrics of the organic fluids of the ORC system and optimal fillingratios is analyzed. Several factors (for instance, work efficiency, safety andenvironmental conservation) are investigated to choose the organic fluids. Theexperiment and the simplified mathematical model are established for the optimal fillingratios of the ORC system. The optimal filling ratios of the ORC system is obtained aftercompared of experimental results and calculation results.According to the characteristics of the low-grade heat resource，a comprehensivesystem economic optimization function which includes two factors (APR and VPR) isproposed．APR means the ratio of total heat transfer area (the area of condenser plusthat of evaporator) and net power generated while VPR denotes the ratio of volume flowof working fluid in turbine and net power of the system. Taking plate heat exchanger forexample, the best pinch point in the exchanger, the degree of the superheat andevaporation are obtained base on the APR and VPR parameters.What’s more, the ORC system is evaluated and optimized by the hierarchyprocess-entropy method. The hierarchy process-entropy method is a comprehensiveevaluation method which can get a comprehensive evaluate for the ORC system.Initially, the optimized evaporation temperature of a simple ORC system is analyzed by the hierarchy Process-entropy method. Then, three CHP-ORC systems (back pressure,external heat pump and built-in heat pump type CHP-ORC system) is evaluated at thethree same power-heat ratios. The result shows the back pressure CHP-ORC systemperformance the best in the three type CHP-ORC system. Ultimately, seven organicfluids are evaluated by the hierarchy process-entropy method. The result demonstratesR600is the best organic fluid for the back pressure CHP-ORC system.