Design And Optimization Of Wave Flow Field In Proton Exchange Membrane Fuel Cell

A proton exchange membrane fuel cell(PEMFC)is a device that generates electricity through an electrochemical reaction of clean fuel.Because of its advantages such as wide use,high efficiency,high reliability and no pollution,it is widely used in civil and military facilities such as automobiles,ships and portable equipment.As the core component of a fuel cell,the bipolar plate is responsible for tasks such as fluid distribution,cooling and heat dissipation.The flow field design directly affects the heat and mass transfer performance of the cell,and has an important impact on the fuel cell power generation efficiency.When conventional flow fields are operated at high current densities,problems such as poor mass transfer and flooding inside the catalytic layer often cause cell output performance to drop dramatically.Therefore,this paper proposes a novel gas flow field and cooling flow channel based on the conventional flow field to enhance the heat and mass transfer capacity of PEMFC.Firstly,in this paper,a novel wave parallel flow field is proposed a fuel cell mathematical model is established using CFD method.The effects of the novel flow field wave length(s)and amplitude(a)size on the fuel cell output performance,oxygen distribution,current density distribution,liquid water distribution,flow-field pressure drop and net output power are analyzed and the novel flow field wave length and amplitude size are optimized.The results show that smaller wave length and larger amplitude can effectively improve the PEMFC mass transfer and water flooding.The enhanced mass transfer mechanism is because in the low-oxygen area,the gas velocity inside the flow field is significantly higher than the other designs to accelerate the oxygen diffusion rate.Furthermore,at 0.6 V voltage,the fuel cell performance is optimal when wave length and amplitude are designed to be 4 mm and 0.8 mm,respectively.The net output power of wave parallel flow field can be increased by up to 34.75% compared to conventional flow field.Secondly,in order to enhance the mass transfer performance of the fuel cell,a three-dimensional wave flow channel model is proposed.The effects of wave length(?)and minimum height(h)on fuel cell output performance,oxygen distribution,current density distribution and liquid water distribution in the 3D flow channel structure are investigated,and the novel flow channel wave length and minimum height dimensions are optimized.The results show that the 3D structured wave flow channel is able to introduce convective mass in the direction of the vertical cell plane compared to the conventional straight flow channel,which promotes the oxygen and current density uniform distribution in the catalytic layer and enhances the cell water removal capacity.Moreover,the fuel cell performance is optimal when the of the novel channel wave length and minimum height are 2 mm and 0.45 mm,respectively.At 0.4 V voltage,the current density of PEMFC with 3D channel structure is 23.8% higher than that of PEMFC with conventional straight flow channel.Finally,a novel wave cooling flow channel structure based on field synergy theory is proposed.The angle between the cooling water velocity gradient and the temperature gradient as the synergistic angle(?).The effect of the synergistic angle on the temperature distribution,maximum temperature,temperature uniformity index(IUT)and pressure drop in the flow channel within the membrane electrode is analyzed,and the field synergistic angle of the cooling flow channel is optimized.The calculation results show that the wave cooling channel has the best heat transfer performance with a 30° synergistic angle and maximum temperature uniformity index increase of 53% compared to conventional cooling channel.