Study On Thermal Performance And Operating Regulation Of The Ejector Heat Exchanger

With the rapid development of urban construction,current central heating systems are confronting with the shortage of heat source for space heating and the lower heat transmission capacity of the existed primary heating network in northern China.The lower temperature return water of the primary heating network(PHN)could increase the heat transmission capacity of the PHN,and recover more low-grade waste heat efficiently.Therefore,sharply reducing the return water temperature of the PHN is an effective way to solve development bottlenecks of current central heating systems.The new ejector heat exchanger based on a ejector heat pump and a heat exchanger is proposed here,and it can reduce the return water temperature of the PHN greatly by cascade energy utilization principle.In this paper,optimum distribution and utilization of available energy,system configuration optimization,refrigerant screen and operation regulation strategy have been studied in order to improve operating efficiency of the ejector heat exchanger.The main contents and results are listed as follows:(1)The impacts of available energy distribution and utilization on performance of the ejector heat exchanger is studied,and capacity match between ejector refrigerator and heat exchanger is optimized.The ejector heat exchanger can greatly reduce the return water temperature of the PHN.(2)The mathematical model of the ejector heat exchanger is constructed.And the working fluid of the ejector heat exchanger is optimally selected according to operating parameters of both the primary heating network and the second heating network.(3)The energy distribution ratio has a great impact on the heat transfer performance of the ejector heat exchanger,and it mainly depends on capacity matching relationship between the ejector heat pump and the water-water heat exchanger in the ejector heat exchanger.(4)There are heat transfer process and the thermal power conversion process in the thermodynamic process.Thus the new evaluation methods combined exergetic analysis and the entransy analysis is suitable to evaluate the thermal process of the ejector heat exchanger.(5)Compared with injection fluid pressurization,mixed fluid pressurization is more efficient method to improve operating performance of the ejector heat exchanger.(6)The operation regulation strategy of the ejector heat exchanger is proposed in the paper,and water temperature regulation curves of the ejector heat exchanger are drawn.The ejector heat ejector can decrease the return water temperature of the PHN greatly by the energy cascade utilization,and its heat transfer performance breaks through the limit of the convention heat exchanger.The results would provide theoretical guidance for the operation regulation of the ejector heat exchanger,and also provide supports for the popularization of the large temperature difference central heating technology.