Study On The Heat Transfer Characteristics Of Vehicular Auxiliary Heat Exchanger

Fuel cell would produce a lot of heat in the operation process,in order to ensure the safe operation of fuel cell train,the main heat exchanger must take away the heat in time,due to the limitation of the roof space,the main heat exchanger is equipped with a high power fan to to ensure the heat transfer of the main heat exchanger,which not only increases the supply burden of fuel cell,but also make the train running noise over standard.To alleviate this problem,the auxiliary cooling system is added to take part of the heat to reduce the equipment or operating power of the main heat exchanger fan.For the limitation of the roof space,on the one hand the auxiliary cooling fan can't be installed,so that the auxiliary heat exchanger can only rely on the train to cause relative movement between the air to achieve convection heat transfer,on the other hand the auxiliary heat exchanger can only be arranged along the length of the train,the air can only enter along the side of the heat exchanger and achieve heat exchange with the heat exchanger along the length direction for the frontal area is very small,which make the air flow distance is long.The structural design,heat transfer conditions and calculation method of heat transfer performance of the auxiliary heat exchanger are different from those of the traditional heat exchanger,so the auxiliary heat exchanger needs to be studied exclusively.Firstly,according to the application conditions and the heat dissipation mode of the aluminum integral heat exchanger with parallel flow and plain fin is used as the structure of the vehicle heat exchanger.Next,according to the structure of vehicle heat exchanger,the dynamic calculation method based on overset mesh methodology and static calculation method are studied,the results show that the static calculation method can't be used directly to calculate the heat exchanger under the condition that the inlet wind speed is equal to the vehicle speed.The heat transfer performance of the heat exchanger under various design parameters is obtained by the calculation and analysis of the heat transfer performance of different parameters vehicle heat exchangers that determined by orthogonal experiment.After obtaining the economic index of the vehicle heat exchanger in each condition,it is analyzed by range analysis method and variance analysis method to determine the influence of each parameter on economic index,and the optimization direction of the vehicle heat exchanger is pointed out based on the analysis results.Then,the Nu number correlation with structural parameters of the heat exchanger is obtained by analyzing the results of convective heat transfer coefficients obtained by dynamic method with dimensional analysis and multiple linear regression analysis,and the correlation applies to the heat transfer calculation under this application conditions and heat dissipation mode.Finally,the feasibility of static calculation is analyzed by comparing the results of static and dynamic calculation,and the correlation between the equivalent inlet velocity and the vehicle speed is obtained by studying the static equivalent calculation method,The research methods and the research results obtained in this paper provide a reference for the research and engineering design of the heat exchanger which achieve heat exchange by the relative movement between the air and has a small frontal area.