Research On Performance Of Direct-fired Ejector Air Source Heat Pump

With the increasing emphasis on environmental protection and the adjustment of energy structure,natural gas,as an efficient and clean energy,has also been increasingly promoted and applied in China.At the same time,more and more attention has been paid to the technology of efficient utilization of natural gas.Compared with electric heat pumps,gas heat pumps are directly driven by gas,which leads to less energy conversion process and higher efficiency,which makes they have also been increasingly popularized.Therefore,gas heat pumps have also been increasingly popularized in recent years.However,for the traditional gas heat pump,although it is directly driven by gas,the lower efficiency of the direct combustion compressor makes the overall efficiency of the system still further improved.This paper replaces the traditional compression heat pump cycle with a ejector heat pump cycle,and adds a flue gas waste heat recovery system to deeply recover the heat in the flue gas,which enhances the system's utilization rate of gas heat.The specific study is as follows(1)A design method of high-efficiency ejector is proposed: in order to improve the efficiency of the ejector heat pump cycle,the difference between the actual gas and the ideal gas is considered,and according to the law of the rate of change of the constant momentum,the structural line of the mixing-diffusion section of the injector is optimized.Therefore,a design method of high-efficiency injector structure is proposed.(2)The mathematical model of the direct-fired injection air source heat pump is established: the operation process,thermal and heat transfer characteristics of the directfired injection air source heat pump system are analyzed.According to the conservation of energy,conservation of mass,heat transfer equations,and thermodynamic state equations,a complete mathematical model of the system is established,and the equation independence and degrees of freedom are analyzed.The requirements of the design parameter combination of the system are clarified and the solution algorithm is given.(3)Performance optimization and evaluation analysis of direct-fired ejector air source heat pump: Through the selection and research of working fluid,R141 b was determined as the working fluid of the system;By studying the influence of key node parameters such as evaporating temperature,condensing temperature and boiling temperature on the performance of ejector heat pump system,the design method and design process of direct-fired ejector air source heat pump system are given.And evaluation indexes such as system unit area heating capacity,gas heat utilization rate,and system comprehensive heating coefficient are proposed to evaluate the system.(4)Research on the operating characteristics of the direct-fired ejector air source heat pump: The operation simulation model of the system is constructed,and the numerical method of iterative solution is given;The effects of air parameters and circulating water return parameters on flue gas outlet temperature,water supply temperature and total heating capacity were studied.The results indicate that the air parameter is the most important factor affecting the system.