Research On Operation Performance Of Heat Pipe Terminal Coupled With Small Cooling/Heat Pump System

Energy conservation and environmental protection are essential issues of global concern in the 21 st century.As a big energy consumer,China’s building energy consumption accounts for about 30% of the total social energy consumption.Air source heat pump system has advantage on energy saving,environment protection,economic cost and thermal comfort.It has a wide range of application value,which is capable for building the corresponding unit to adapt to different places.Heat pipe is a heat transfer element using phase-change heat transfer.It has the advantage on stability,high efficiency,convenient installation and simple production process,which is widely used in electronic and electrical engineering,aerospace,construction,waste heat recovery,solar energy and other fields.In this study,combining the advantages of air source heat pump and heat pipe technology,the heat transfer system using heat pipe terminal coupled with heat pump is proposed as evaporator/condenser for summer cooling/winter heating.Applied the heat pipe refrigerant as intermediary medium,the heat pump refrigerant flowing inside the new system exchanges heat with the indoor environment through the heat transfer terminal.During the process,the heat pipe refrigerant absorb heat by evaporation and release heat by condense.In order to clarify the performance parameters of the system during operation and explore the direction of improvement and optimization,it is necessary to study and analyze the heat and mass transfer,power-heat conversion and other processes in the composite system.In this thesis,the mechanism of heat transfer terminal and the performance of the system are analyzed by combining theoretical analysis and experimental test.The details are as follows:Firstly,in the cooling condition,the heat transfer process of heat pipe terminal is theoretically calculated.Combined with the mathematical model,the heat transfer temperature difference of each heat transfer process in the cooling terminal heat transfer process was studied.The range and proportion of thermal resistance values of each part in the cooling process of heat pipe terminal driven by heat pump refrigerant flowing in evaporation bundles are analyzed.The charging quantity and flow resistance of refrigerant in the system are calculated and the advantages of replacing and reducing refrigerant by using heat pipe cooling terminal are studied.Secondly,according to the heating condition,the forced convection finned tube heat pipe heating terminal is designed.The heat transfer process and size design of condenser are carried out,and the heat transfer process of heat pipe is analyzed and calculated.The performance parameters such as heat exchange temperature difference,flow resistance and charge quantity are compared between heat pipe condenser coupling heat pump and conventional direct air cooling condenser.Finally,a test bench combined with a heat pipe forced convection terminal coupling with heat pump is set up.to compare the heating performance of the conventional direct heat transfer condenser and the heat pipe condenser coupling heat pump.The finned tube surface temperature distribution,inlet and outlet air temperature,system start-up characteristics and compressor suction and exhaust pressure of the two condensing systems are tested and compared.By sorting out and analyzing the experimental test data,the two condensing systems are compared.The performance advantages of heat pipe condenser during heating are analyzed,including system start-up characteristics,uniform surface temperature distribution,heating performance and COP,in-pipe heat pump refrigerant charge quantity and flow resistance,etc.