Analytical Modeling Of Proton Exchange Membrane Fuel Cell And Parameter Sensitivity Analysis

It is of paramount importance to understand the internal reaction and transport mechanisms of proton exchange membrane fuel cell(PEMFC)in order to improve its performance and duration.A 1D(one-dimensional)non-isothermal and two-phase flow model is built analytically at first.It not only considers the water saturation jump,but also puts forward a novel method to solve the water phase changes and couples the liquid and vapor transport together with a proposed coupling factor.A stringent model validation procedure is used to show good agreement between the simulated results and the experimental data.Based on this 1D model,the effects on cell performance,water and temperature profile inside the fuel cell are studied under conditions of different current density,contact angle of microporous layer(MPL)and operating conditions.Good operating schemes of fuel cell are proposed,and the results indicate that larger contact angle of MPL facilitates liquid water to transport from cathode to anode through back diffusion process,relieving the dehydration of anode to some extent.However,excessive increase of MPL contact angle may worsen the flooding of cathode on the other hand.The best operating temperature is around 80~?C,and the best inlet pressure is about 2atm.The cell performance can be improved by increasing the cathodic stoichiometry with just enough anodic stoichiometry.With fully humidified anode and low-humidified cathode,the performance and lifetime of fuel cell will be comparatively improved.In the present study,the reliability of traditional model validation method is discussed,and it is revealed that the uncertain parameters may deteriorate model reliability and credibility,thus demonstrating the necessity to conduct sensitivity analysis.A multi-parametric sensitivity analysis method(MPSA)i.e.the elementary effect(EE)method based on Monte Carlo experiments is implemented to comprehensively analyze the total 22 uncertain parameters,which are finally classified into highly sensitive ones,rather sensitive ones and insensitive ones.The derived sensitivity indexes explain the monotonicity and robustness of the effects of each parameter on fuel cell performance.Besides,whether the effect of each parameter is positive or negative is also discussed.Furthermore,the two-sample Kolmogorov–Smirnov(KS)test is applied to verify the stability difference between different model cases.It is concluded that the robustness of fuel cell may be different even with the same cell performance,and hence the effects of varying operating conditions should be taken into account in validation work.A quasi-2D model is built based on the 1D model,considering the reactant concentration distribution along the channel as well as the effect of outside heat convection.The present study compares characteristics of reaction gas concentration,relative humidity and temperature distributions inside the fuel cell under co-flow and counter-flow modes,and the current density distribution along the channel is also illustrated under different cathodic stoichiometry.The results show that the fuel cell presents more uniform current density,relative humidity and temperature distributions for co-flow mode compared to counter-flow mode,and the current density distribution of co-flow mode is correlated to Wa number.