Research On Heat And Mass Transfer Of PEMFC

Proton Exchange Membrane Fuel Cell(PEMFC)is an efficient energy conversion system that directly converts the chemical energy stored in the fuel into electrical energy.Proton exchange membrane fuel cells are not limited by the thermal efficiency of the Carot cycle,have high energy conversion efficiency and high energy density,and are expected to be widely used in mobile devices such as automobiles.Moreover,fuel cells have the advantages of clean,high efficiency,low noise,etc,and are considered to be an important source of power in the future.In recent years,as people’s awareness of environmental protection has increased,more and more research institutions and companies have conducted more and more in-depth research on proton exchange membrane fuel cells.As the proton exchange membrane fuel cell is a low-temperature fuel cell,the working temperature is generally lower than 100℃.During its working process,it is easy to produce a large amount of water and a complicated phase change process,especially under the condition of high current density,the heat production and production The amount of water is greatly increased,a large amount of energy is dissipated in the form of heat energy,and the production of liquid water can easily block the porous medium gas diffusion layer and the porous medium catalytic layer,which reduces the contact area between the reactant gas and the catalytic surface,and aggravates the concentration difference of the fuel cell.The phase change heat generated by the complex phase change process also affects the thermal management strategy of the fuel cell.Fuel cells often need to work under medium and high current densities.Therefore,the hydrothermal management of fuel cells,especially the research on hydrothermal management under medium and high current densities,has always been a hotspot and difficulty in fuel cell research.In order to further optimize the water and heat management of PEMFC and improve the performance of the fuel cell,a multi-dimensional,non-isothermal,numerical model containing phase change processes was established.The main research contents are as follows:By studying the gas transport process of the proton exchange membrane fuel cell,the flow field structure is optimized,and the mass transfer process of the reaction gas is strengthened to improve the performance of the cell and increase the power density output.The influence of different flow channel geometrical dimensions on the mass transfer performance of fuel cells is compared,and the advantages and disadvantages of the mixed flow field and the multi-channel serpentine flow field are analyzed,and the two flow channels are compared in dealing with the uneven distribution of the reaction gas.The performance and the performance of removing liquid water.By using the level set method to track the movement process of the gas-liquid interface,analyze the production,rupture,and transmission process of liquid water in the flow channel,and analyze the influence of the affinity and hydrophobicity of the porous media diffusion layer material on the change of the liquid water morphology,and The optimization effect of the gravity-assisted drainage scheme on the performance of liquid water removal is verified.Summarized several effective solutions to improve the removal effect of liquid water.Through the establishment of a two-phase,non-isothermal simulation model,the gas-liquid two-phase flow process and the gas-liquid phase transition process in the porous media layer are analyzed,and the influence of the flow velocity on the change of the liquid water content is analyzed.The results show that the appropriate increase The gas flow rate at the inlet of the flow channel not only facilitates the discharge of liquid water accumulated in the flow channel,but also facilitates the discharge of liquid water in the porous medium layer.The finally established two-phase,non-isothermal,three-dimensional simulation model of the full battery including the cooling channel is based on the amount of liquid water produced through actual tests in the literature,avoiding the fact that pure mathematics,physical formulas and empirical formulas are difficult to accurately reflect the actual operation of the battery The disadvantages of the conditions,considering the influence of liquid water on the porosity and permeability of porous media,analyzed the influence of liquid water on the concentration polarization of the battery,and analyzed the influence of the cooling water flow on the heat dissipation of the fuel cell.