Influence Of Variable Channel Cross Sections By Baffle Plates On The Mass Transport And Performance Of PEMFC

With the growing of greenhouse effect and the depletion of fossil fuels,more and more researchers have focused on the proton exchange membrane fuel cells?PEMFCs?due to its high efficiency and zero pollution.The fuel cell performance is influenced by the distribution of reactant gas in the fuel cell and the efficiency of mass transport process,especially in the situation of high current density.Based on a 3D fuel cell model working in a steady state,the research have made various channel cross sections by the baffle plate and update the transport mechanism to the nonlinear law of permeability in porous electrode.The research have studied the effect of various cross sections on the mass transport and fuel cell performance which can be listed as follow:To find the design of optimized baffle plate,we insert baffle plates in cathode channel to investigate the effect of blockage ratio and number of baffle plates.The results show that larger blockage ratio of baffle plate can enhance the convective intensity but also cause larger pressure drop.The optimal design of blockage ratio should be 0.8 considering the pumping power.The high convective flow regions increase with the number of baffle plates while too many baffle plates will weaken the convective intensity in the middle region.So,there should be an optimal number for the setting of baffle plates.And the flow resistance can be decreased with the sloping baffle plate.The numerical results show that the velocity component along the channel will influence the size of convective area while the velocity component in vertical direction will influence the intensity of convection.Finally,a design of trapezoid baffle plate is proposed according to the paper researches and previous numerical works.And front sloping angle have been confirmed with the rule of sloping baffle plate.In addition,the back flow is avoided with the trailing edge inclination.What's more,the nonlinear law of permeability is applied in porous electrode according to the application rule of Dacy's law.And the number of trapezoid baffle plate have been optimized considering the pumping power.A stable cross flow phenomenon can be obtained by staggering the trapezoid baffle plates in the adjacent channels due to the stabilized pressure drop.The O₂ concentration is enhanced in the rib region which can make better use of active area.And the cross flow can also help remove the extra liquid water and improve the water management.Experimental study is also carried out.The results found that the staggered baffle plates design performs best with mass flow rate of 0.5/0.5 SLPM.The maximum enhancement with staggered baffle plates in power density can reach about 9.37%with the stoichiometric ratio of 1.5/1.5 compared with the conventional parallel channels.