The Optimization Design And Experimental Study Of Fuel Cell Flow Field

Fuel cell is a new type of sustainable,green and environmentally friendly clean energy equipment,which generates electricity through hydrogen energy.Proton Exchange Membrane Fuel Cell(PEMFC)is the most widely used type of fuel cell technology.Due to its high efficiency,no pollution,wide application and strong reliability,automotive,shipping,aerospace and other fields have adopted this technology to produce electric energy or kinetic energy.Bipolar plate is a core component of the fuel cell.Its main functions are supporting membrane electrode,providing hydrogen,oxygen and coolant fluid channel,separating hydrogen and oxygen,electronic collection and heat conduction.Its design of flow field will directly influence the heat and mass transfer effect in the flow field,which also has obvious influences of the performance and life of the fuel cell.The parallel flow field is the most widely used in PEMFC.However,when it runs with high current density,the current density will not evenly distribution,and the large temperature difference in the flow field will lead to excessive local temperature and uneven distribution of oxygen concentration,which affect the performance of the fuel cell.Therefore,based on the traditional parallel flow field and metal foam flow field,a new type of additional outlet flow field was proposed to enhance the heat and mass transfer ability of PEMFC,and the influence of the new type of additional outlet flow field on the performance of PEMFC was verified through experimental research.In terms of the problems of the uneven mass transfer and uneven temperature of the traditional parallel flow field in PEMFC.And the problem when the traditional parallel flow field under high current density,it is prone to flooding.This paper proposes a new type of parallel flow field with additional outlet,which using the numerical calculation to simulation analyze the cathode oxygen concentration distribution,the current density distribution,temperature distribution,flow of liquid water activity,membrane water saturation and fluid velocity in the flow characteristics of the additional outlet parallel flow field.And it compared with traditional parallel flow field through the data.Results show that the additional outlet can effectively improve the heat and mass transfer problem of PEMFC,the mechanism of strengthening mass transfer is the setting of additional outlet will reduce the pressure in the vicinity of the additional outlet and increase the flow of differential pressure.Meanwhile,the fuel gas in the flow velocity is increased accordingly,which enhancing the diffusion rate of gases inside the flow field.In addition,by comparing and analyzing the digital simulation results of the additional outlet at different locations,it is concluded that when the additional outlet is setting at the "midpoint" of the corresponding side of the gas flow direction,the fuel cell’s performance can be improved by up to 13%.Besides,for the parallel flow fields with different activation areas,the additional outlet can improve the batteries’ performance,and the optimal location is also in the "midpoint" of the corresponding side of the gas flow direction.Secondly,because the fuel gas in the metal foam flow field is spreading by diffusion,it results in uneven distribution of oxygen concentration in the cathode and low mass transfer efficiency.In order to strengthen the mass transfer characteristics in the metal foam flow field,a new type of additional outlet metal foam flow field was proposed in this paper,which established a numerical model of fuel cell.According to the optimal setting of additional outlet in the parallel flow field above,additional outlet was set in the area with lower oxygen concentration distribution in the metal foam flow field.Through digital simulation,the effects of additional outlet on the output performance,oxygen distribution,current density distribution,pressure distribution and temperature distribution of metal foam flow field fuel cell were studied and analyzed.The results show that compared with the metal foam flow field,the area with high oxygen concentration in the new foam flow field at the additional outlet diffuses significantly towards the additional outlet,and the oxygen concentration distribution is more uniform,which strengthens the mass transfer ability of the fuel cell.And the temperature distribution is more uniform,too.Under the voltage of 0.4V,the current density of metal foam flow field with additional outlet is10.3% higher than that of traditional metal foam flow field.Finally,the batteries’ performance of the parallel flow field at the additional outlet under different working conditions was studied by experimental test method.Besides,this essay compared it with the traditional parallel flow field.Under different working conditions,compared with the traditional parallel flow field,the performance of the fuel cell with additional outlet is improved by more than 7%.