Optimization And Design Of Flow Field Structure In Proton Exchange Membrane Electrolyzer

Proton exchange membrane electrolyzer(PEM)is a kind of hydrogen production device using liquid water as reactant.Especially in the current crisis of energy shortage,people pay more and more attention to hydrogen production by PEM.The flow field design of the internal bipolar plate is particularly important for the performance and service life of the electrolyzer.Therefore,by changing the internal flow field structure,the performance and output of the electrolyzer can be improved,and finally an optimization purpose can be achieved.Nowadays,the optimization and design of flow field mostly rely on simulation.When the calculation of large size,multi-channel and complex flow field shape,the calculation time is often long and the model is not easy to converge.Therefore,a simplified reaction flow model is designed in this paper.Through the establishment of parallel flow field of several different size channels,the effects of the width of horizontal channel and vertical channel on the pressure,velocity,gas mole fraction and cell performance are studied.It is found that widening the vertical channel has a greater impact on the performance of the electrolyzer.Reducing the width of the vertical channel or widening the width of the horizontal channel at the inlet and outlet at the same time can improve the performance of the electrolyzer,make the reaction more uniform and enhance the gas fluidity.At the same time,at low current density(0～0.5A/cm~2),the effect of widened channel width on cell performance is small,while at high current density(1～1.5A/cm~2),the effect of widened channel width on cell performance is large.Then,on the basis of the parallel flow field,the local optimization is carried out,and the low velocity region of the parallel flow field is replaced by the serpentine channel structure,and a new flow field structure is obtained.Compared with the flow field structure before optimization,it is found that the flow field structure after optimization can effectively improve the performance of electrolyzer,alleviate the problem of local uneven flow velocity in parallel flow field,and the gas is more evenly distributed in the depth direction of channel,which is more suitable for the practical application of electrolyzer.The traditional gas channel flow field has good mechanical strength and heat exchange performance,which can effectively reduce the interface resistance loss by fully contacting with the diffusion layer surface.However,due to the poor gas fluidity and working performance,people need to further study.Therefore,this paper will focus on the effect of the structure of the non channel flow field on the electrolyzer.The foam metal has good physical and electrochemical properties,and is very suitable for application in the flow field structure of the electrolytic cell.The influence of the structural parameters of the non channel flow field on the electrolyzer was studied by establishing the gas phase model of the electrobath with foam metal structure and changing the sectional shape,thickness and porosity of the flow field.Finally,a two-dimensional gas-liquid two-phase reaction flow model is established to study the influence of contact angle and porosity of porous materials on the performance of electrolyzer.It is found that the smaller the thickness of titanium felt is,the larger the contact angle and porosity are,which is more conducive to the transportation of reactants and the improvement of electrolytic performance.By comparing different cross-section shapes,the flow field structure of circular cross-section is more suitable for electrolyzer.