Mass Transfer In HT-PEMFC And Its Performance Test

With the gradual scarcity of traditional resources,the importance of new energy technology research and development is recognized worldwide.As a efficient-energy and pollution-free new energy generation device,proton exchange membrane(PEM)fuel cell has wide appeal.The working temperature of traditional proton exchange membrane fuel cell is 80?,which requires high purity of reaction gas and of which complicated water management.Compared with traditional proton exchange membrane fuel cell,high temperature proton exchange membrane(HT-PEM)fuel cell has a better prospect of application,overcoming the above two disadvantages besides retaining the advantages of traditional proton exchange membrane fuel cell.Currently,HT-PEM fuel cell still couldn't fulfil for widely utilization well in the aspects of cell performance,service life and cost.Through experiment and simulation,performance of HT-PEM fuel cell is studied and trends of performance under different running conditions is analyzed in the thesis,which have certain instruction significance to improving performance of HT-PEM fuel cell.On the basis of plenty of PEM fuel cell literature,development history,research status and application status of fuel cell were induced,working principle,structure composition and usage characters of PEM fuel cell were elaborated.Meanwhile,thermodynamics,dynamics and electrochemistry knowledge related with PEM fuel cell was elaborated in the thesis.Fuel cell test platform was built in the thesis,by which HT-PEM fuel cell voltage-current characteristic and AC impedance characteristics were tested.And influence of changes of HT-PEM fuel cell inlet temperature to cell performance with humidification was analyzed.Using equivalent circuit method,HT-PEM fuel cell AC impedance chart was analyzed,equivalent circuit and equivalent element of cell were found,and the influences of inlet temperature and humidity to equivalent element impedance were analyzed.The experimental results showed that HT-PEM fuel cell performance promotes when promoting inlet temperature without humidity,and promoting inlet temperature influences cell performance a little with humidity.Based on mass transfer,electrochemistry,fluid mechanics and solid mechanics,a three-dimensional,single-phase HT-PEM fuel cell mathematical model of mass transfer was established,coupling solid mechanics field,porous media reaction flow and secondary current distribution field.Using this model,delivering and distribution of oxygen,water and hydrogen,distribution of cell clamp stress,strain and porosity were simulated,influence of fitting prestress to stress,strain,porosity,material transfer,current density of diffusion layer carbon paper were analyzed.The results showed that with stress on flow apophyses enlarging,porosity of diffusion layer under flow apophyses reduces and diffusion of gas mass transfer got difficult.HT-PEM fuel cell performance reached the best at 2MPa prestress.Based on Mesoscopic dynamics theory,a mesoscopic mass transfer model of HT-PEM fuel cell cathodic diffusion layer was built by Materials Studio software.The interaction between the pearls in the model was described by the Martini force field.Changes of Diffusion coefficient of gas mass transfer in the model was analyzed in different model parameter condition.Results of simulation analysis showed that heating was beneficial for mass transferring because diffusion coefficient of components of gas in system enlarges when heating,and diffusion coefficient decline when water mass ratio enlarges because spreading of oxygen was hindered.