A Study Of The Heat Transfer Performance Of An Air-air Shell And Tube Heat Exchanger

In order to solve the problem of the deterioration of indoor air quality in the air conditioning system and timely reduce the content of pollutants in the indoor air,the method of introducing outdoor fresh air is often used to solve the problem.In this thesis,a kind of shell and tube type heat exchanger(heat recovery device)made of the heat and humidity exchange membrane tube bundle is proposed to obtain a higher heat transfer area and Heat transfer efficiency.In this study,the heat and humidity conditions refer to the house temperature and humidity standards in hot summer and cold winter areas,and the influencing factors of heat exchange efficiency,moisture exchange efficiency and resistance of heat exchanger are studied by using COMSOL software numerical simulation as the main method.The specific research contents are as follows:(1)Under ideal conditions,the hollow fiber membrane maintains a rigid structure during operation.They do not deform due to gravity and can be completely evenly distributed within the unit.However,considering the actual situation,the hollow fiber membrane will undergo certain deformation during the installation process,and the number of about tens of tube bundles in the unit cannot be strictly and evenly distributed.Therefore,the deformation model of the fiber membrane and the random distribution model of the tube bundle were established respectively to study the influence of the deformation and random distribution degree of the fiber membrane on the flow resistance and heat transfer efficiency.(2)In order to explore the heat and humidity exchange characteristics and resistance characteristics of the heat exchange model,the cross-section radius ratio,fluid velocity,temperature difference,runner length and other factors of the total heat exchanger model were studied,and their influences on heat and humidity exchange efficiency and runner resistance were studied.(3)Based on the heat transfer characteristics of heat and moisture exchange film and tube and shell heat exchanger,the structure design of the total heat exchanger is optimized and compared with the plate heat exchanger.Based on the heat transfer characteristics of heat and moisture exchange film and shell heat exchanger,two heat transfer models of cross flow and reverse flow were established.The flow and heat transfer characteristics of the two methods are studied,and a more efficient cross flow to counter flow length ratio is obtained for the design of heat exchangers.