| The utilization of medium and low temperature heat energy helps to reduce primary energy consumption, and mitigate climate change and air pollution problems. In this paper, a combined cooling heat and power-organic Rankine cycle(CCHP-ORC) system installed with heat pump was studied, which is efficient in the use of medium and low temperature heat energy. This paper not only contains the system parameters affect analysis and the working fluids optimized selection of the system using pure working fluids previous proposed, also presented a new and more efficient system using zeotropic mixtures, and this system has also been studied.Before all, a system model under a idealized operating condition was built. The heat source of the model is 95? geothermal water, and it's flow is 40t/h. The system heat the transport liquid to 45? in the outdoor temperature of minus 5?, and refrigerate the transport liquid to 0? in the outdoor temperature of 35?. By using the model, the parameters of the system and the power generation efficiency, coefficient of performance(COP), exergy efficiency, economic thermal efficiency and refrigeration efficiency can be calculated according to the needs of research.In the part of the pure working fluids system, the effect of high temperature evaporation superheat was analyzed. The results show that, the change trends of a parameter affected by the superheat degree have no different between CHP and CCHP modes, also have no different between dry or wet working fluids. The results of optimized selection in 12 kinds of working fluids show that the net output power and the power generation efficiency of R245 ca and R141 b is higher; the coefficient of performance, economic thermal efficiency and refrigeration efficiency of R717 is superior to others; R141 b and R717 have best exergy efficiency.In the part of the mixtures system presented by this paper, the rationality of two possible forms of system was analyzed firstly. The form of that the liquid working fluid flow through the working fluid pump into the high temperature evaporator, and the gaseous working fluid flow into the low temperature of condenser are considered more reasonable. And then, the performance indicators of pure working fluids and mixtures system in CHP or CCHP modes and different ejector coefficients were calculated respectively. The systems using mixture R245fa/R134a(75:25 wt %) or pure working fluids R245 fa or R134 a. Comparison results show that the coefficient of performance mixtures system is higher than pure working fluid system in CHP and CCHP modes. In addition, because the mixtures system can output cooling, heat and power simultaneously, it is more flexible than pure fluid system on energy outputting. Another conclusion was got: The ejector coefficient is an important regulation parameter of both mixture and pure working fluid system. The adjustable limit of the ejector coefficient is determined by the system power generation capability. A system having high power generation efficiency has a larger maximum of ejector coefficient.With the ejector coefficient and the evaporation temperature as variables, the parameters and performance indicators of the mixture system were calculated. The conclusions were drawn from analysis: Most of the performance indicators have a mainly influence parameter; the system has a higher coefficient of performance under the CCHP mode; the efficiencies cannot represent the actual energy output capacity, and there are limitations to evaluate the system from the performance indicators merely.Finally, some conclusions obtained from the optimized selection of mixtures. One of the conclusions is that the mixture systems can select a kind of mixture, which has high power output and cooling-heat output performance. And it can be inferred that a mixture of dry and wet working fluids is more suitable for the system. The system has higher energy output if there more wet working fluid and less dry working fluid in the mixture. |
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