Experimental Research And Application Analysis Of Separated Heat Pipe Heat Exchanger

With the advancement of science and technology and economic development in China,more and more clean rooms are used in various fields such as electronics,medicine,food,chemicals,animal experiments,etc.Among them,scientific research institutes and pharmaceutical industry have a great demand for animal laboratory facilities,so the number of laboratory animal room is increasing year by year.Due to the function of the laboratory animal room,it is necessary to set up a clean air conditioning system with fresh air,so the energy consumption of air conditioning is large.Based on the above background,through the use of separate heat pipes in the air conditioning system of the laboratory animal room,the exhaust energy can be recovered and the energy consumption of the fresh air can be reduced,while the cross-contamination of the new and exhaust air can be avoided.In this paper,the separated heat pipe heat exchanger used for heat recovery is analyzed theoretically and experimentally,and its application in the air conditioning system of experimental animal room is analyzed.The main work and achievements are as follows:(1)This paper analyzes the heat transfer characteristics of the separated heat pipe,summarizes the design calculation method of the common heat pipe heat exchanger and analyzes its applicability to the separated heat pipe.The equivalent partition wall calculation method is used to theoretically design the separated heat pipe heat exchanger suitable for the air conditioning system of laboratory animals,which mainly includes the selection of heat pipe materials and working materials,structural design,heat transfer calculation and safety check.According to the two-phase flow theory,the lower limit of the filling rate is calculated,and the filling rate of R134 a in the separated heat pipe is determined.The two-phase flow pressure drop model is used to calculate the flow pressure drop in the tube,and the minimum height difference between the evaporation section and the condensation section when relying on gravity circulation was calculated based on the circulating power in the tube.(2)Two heat exchanger experimental systems with different structural parameters and different total heat exchange areas are built.The second experimental system is a separate heat pipe heat exchanger designed by the author.Each experimental system is designed with gravity type separated heat pipe experimental platform and dynamic type separated heat pipe experimental platform.At the same time,the design and selection of fluorine pump and liquid storage tank are carried out.The influencing factors of heat transfer performance,the start-up characteristics of the system,the temperature drop characteristics of the two heat transfer sections and the air pressure drop are studied through experiments.The performance of the system before and after adding pump is compared.The heat transfer performance of the system using R22 and R134 a as working fluid are analyzed.Experimental research find that : 1)The heat exchange rate of the separated heat pipe is approximately linear with the temperature difference of the air inlet.Within the test range,the inlet air temperature of the cold and hot ends has little effect on the heat exchange and heat recovery efficiency.2)For the separated heat pipe with insufficient natural circulation power,adding pump can obviously improve the isothermal property of the heat pipe and enhance the heat exchange effect.For the separated heat pipe heat exchanger with enough natural circulation power to overcome the flow resistance,the effect of adding pump is not significant.3)The error between the theoretical and experimental results is small.(3)The heat recovery efficiency is theoretically analyzed by using the equivalent wall type calculation model,and the relationship between heat recovery efficiency and heat exchange area is obtained.The heat exchange capacity and heat recovery efficiency of the separated heat pipe at different wind speeds are also calculated.It is found that the ideal total energy recovery effect can be obtained in the wind speed range of 2.5 ～ 3.0m/s.The application effect of the separated heat pipe in the laboratory animal room in different climate regions in China is analyzed.In Changchun,Beijing,Kunming and Chongqing,the net energy efficiency ratios are 16.8,11.6,6.5 and 5.3 respectively.In this paper,the research on the separation heat pipe heat exchanger is carried out from two aspects of experimental research and theoretical analysis,and its energy-saving effect is analyzed,which can provide reference for the design and application of the separated heat pipe.