Design And Thermal Management Analysis Of Variable Diameter Flow Channel For PEM Fuel Cell Based On Enhanced Mass Transfer

Proton exchange membrane fuel cell（PEMFC）has the advantages of high energy conversion efficiency,clean and environmental protection,and rapid start-up at room temperature.It is a very promising new energy device.As one of the core components of PEMFC,the bipolar plate has been It is the focus of engineering research,and reasonable bipolar plate flow channel design can make PEMFC exert better performance.In this thesis,based on the principle of gas-enhanced mass transfer and pressure difference between adjacent flow channels,the flow channel structure design of the straight channel battery model and the serpentine flow channel battery model is carried out respectively.Using the CFD simulation method to study the improvement of the optimized flow channel structure on the performance of the battery in all aspects.For the thermal management of the battery,two wave-shaped cooling channels are designed to study the influence of the wave-shaped structure on the heat dissipation performance of the battery.The main research contents are as follows:Firstly,the mathematical model of PEMFC is established based on the hydrodynamic control equation,electrochemical equation of PEMFC and water transport equation in membrane electrode.Secondly,based on the enhanced mass transfer method of the flow channel,the single-channel PEMFC inlet flow channel is treated with bosses,and the influence of the number of bosses in the flow channel（N）and the boss height（H）on the output performance of the battery is analyzed.The results show that the addition of bosses in the flow channel can effectively improve the performance of the battery.More bosses and higher boss heights can effectively improve the diffusion of the reactant gas in the flow channel to the membrane electrode.The target PEMFC operates at a voltage of 0.5V.The best performance can be obtained.When the number of bosses is N=20and the height of the bosses is H=0.6mm,the power density of the fuel cell is0.416W/cm²,which is 31.2%higher than that of the conventional one-channel PEMFC.Then,taking a 70mm×70mm PEMFC as the research object,based on the principle of pressure difference between adjacent runners,a new type of serpentine"variable diameter+boss"runner structure was proposed,and the CFD simulation method was used to study the effect of structural improvement on the battery.impact on output performance.The results show that the variable diameter throttling treatment of the serpentine flow channel can effectively increase the current density of the battery,strengthen the mass transfer and diffusion of reactive gases such as hydrogen and oxygen,and can effectively discharge the flow channel and the membrane electrode.of water.The fuel cell achieves the best performance when the operating voltage is 0.4V.The power density of the new channel PEMFC can reach0.506W/cm²,which is 108.2%higher than that of the conventional serpentine channel PEMFC.The maximum H₂concentration of the anode catalyst layer was increased by5.5%,the maximum O₂concentration of the cathode catalyst layer was increased by2.5%,and the maximum water content of the cathode flow channel was reduced by8.6%.Finally,in order to analyze the heat dissipation of the PEMFC,the corresponding cooling water channels are designed based on the battery model in Chapter 4,and the influence of the cooling water flow rate and the number of channels on the heat dissipation performance of the battery is studied.The results show that faster cooling water flow rate and more flow channels can make the battery achieve better heat dissipation.In order to achieve a larger heat dissipation area,two new wave-shaped cooling channels are designed.The results show that the wave-shaped channel can make PEMFC achieve better heat dissipation uniformity,and the maximum temperature on the film is 6.5K lower than that of the straight channel PEMFC.