Numerical Simulation And Optimization Design Of PEMFC Cooling Flow Field

Proton exchange membrane fuel cells(PEMFCs)have the characteristics of fast startup,low operating temperature,and high power density.They are widely used in transportation,portable applications and other fields.PEMFC can convert chemical energy into electrical energy while releasing a lot of heat.In order to keep the PEMFC running properly and avoid local overheating of components,the excess heat generated by the PEMFC must be effectively removed.The main cooling method of high-power PEMFC is to add a cooling flow field in the bipolar plate,and the excess heat generated by the PEMFC is taken away by the circulation of coolant.A reasonable cooling flow field structure can improve the PEMFC life and power generation efficiency.In this thesis,numerical simulation is used to study the influence of the PEMFC cooling flow field structure on the cooling effect and power generation performance of the fuel cell.First,in order to improve the problems of large internal temperature difference and inlet and outlet pressure drop of traditional cooling flow fields,several improved cooling flow fields are proposed in this thesis,and the fluid flow and heat transfer characteristics of different cooling flow fields are compared and studied.At the same time,the maximum surface temperature,temperature uniformity,pressure drop,and current density are used as evaluation criteria to discuss the influence of different cooling flow field structures on the cooling effect and power generation performance of the PEMFC.The numerical results show that improving the cooling flow field structure and increasing the Reynolds number can effectively enhance the cooling effect and power generation performance of the PEMFC.Among all the cooling flow fields studied,the serpentine modified flow field performed the best.Under the operating conditions of Reynolds number of 1000 and voltage of 0.6V,the temperature uniformity index is 30% lower than that of the traditional parallel cooling flow field,and the current density is 5.4% higher than that of the traditional parallel cooling flow field.Secondly,the structural parameters of the serpentine modified cooling flow field are discussed.Taking temperature uniformity,pressure drop,net output power,etc.as the evaluation criteria,the influence of the width,depth and number of the transverse channels of the improved cooling flow field on the cooling effect and power generation performance of the PEMFC is discussed.The results show that with the increase of the lateral channel width,the temperature uniformity and power density of the PEMFC will decrease,and the parasitic power caused by the pressure drop will also decrease.When the channel depth increases,the temperature uniformity and power density of the PEMFC increase,and the parasitic power caused by the pressure drop in the flow field decreases.As the number of lateral channels increases,the temperature uniformity and power density decrease,and the parasitic power caused by the pressure drop decreases gradually.Considering the power density and parasitic power of the PEMFC,the serpentine modified cooling flow field has the best performance when the width of the transverse channel is 0.5mm,the depth is 1mm,and the number is 2.Compared with the traditional parallel cooling flow field,its power density is increased by 5.1%.Finally,in order to further strengthen the convective heat transfer capability of the cooling flow field,this thesis filled the serpentine modified cooling flow field with porous metal foam materials to study the influence of the filled cooling flow field on the PEMFC cooling effect and power generation performance.At the same time,the effects of Reynolds number,porosity,metal material,and coolant type on the cooling effect and power generation performance of different metal foam-filled cooling flow field fuel cell are discussed.Numerical research results show that the cooling flow field filled with metal foam can effectively enhance the PEMFC cooling effect and power generation performance,but at the same time the pressure drop is increased.The serpentine modified filled cooling flow field fuel cell has the highest power density,which is 3.5% higher than the unfilled serpentine modified cooling flow field and 7.5%higher than the traditional parallel cooling flow field.