Effect Of Operating Parameters On Mass Transfer In The PEMFC

In the 21 st century,Proton Exchange Membrane Fuel Cell(PEMFC)has become one of the most promising new energy vehicle power because of its advantages,such as high power density,quick start,quick response between different loads,low operating temperature,being clean and zero pollution,etc.However,the uneven distribution of mass transfer of PEM fuel cell affects the overall performance of fuel cell.As the core component of PEM fuel cell,the proton exchange membrane needs to be sufficiently wetted with water to ensure its good proton conductivity and to avoid the problem of dried membrane.In the cathode side,excessive water will lead to water flooding,which seriously affect the distribution of the reaction gas.Therefore,the mass transfer problem in PEM fuel cell has received extensive attention and research from scholars at home and abroad.It is necessary not only to ensure that the proton exchange membrane has good proton conductivity,but also to control the water content in each part of the cell.This paper attempts to study the influence of operating parameters of PEM fuel cell on the reaction gas distribution and water distribution,so as to provide help to improve the performance of fuel cell.In this paper,the literature related to mass transfer research of PEM fuel cell was firstly reviewed and the current research status and problems were understood.Secondly,a geometric model of the single straight channel of PEM fuel cell was established based on the theories of electrochemistry,mass transfer and fluid mechanics and other related theories.The validity of the model was verified by comparing the experimental and the simulated polarization curve.A single straight channel of PEM fuel cell was taken as the research object.The influences of operating parameters,such as voltage,inlet flow rate and humidity,on the reaction gas distribution and water distribution in each component of PEM fuel cell were studied as follows:(1)The 8 groups of different voltages were divided into two groups respectively,high voltage and low voltage,to analyze their influence on the reaction gas distribution in various parts of the cathode and anode sides.Meanwhile,the water content,volume ratio of water and its distribution in the cathode under high and low voltage were studied as well.The results showed that the reaction gas distribution in each part of the model was more uniform and less affected by the voltage when the voltage was between 1.1V and 0.8V.The voltage had a great influence on the distribution of reaction gas in various parts,especially on the distribution of reaction gas in the porous electrode if the voltage was between 0.7V and 0.4V.The water content in cathode reached the maximum at 0.4V.(2)After determining the range of maximum voltage parameters affecting mass transfer,the inlet flow rate of the reaction gas was changed to study its influence on the distribution of the reaction gas in various parts.At the same time,it was compared and analyzed for different inlet flow rates that the influence of the change of the inlet flow rate on the water content,volume ratio of water and its distribution in the cathode.The results showed that increasing the inlet flow rate of the reaction gas was beneficial to the uniform distribution of the reaction gas in each part of fuel cell,and it was also beneficial to reducing the water content in each part of the cathode.(3)After the optimum inlet flow rates,the humidity of the gas reaction was taken into consideration to investigate its effect on reaction gas distribution in each part of the fuel cell.According to different humidity parameters,the influence of water distribution was studied in cathode.The results showed that the change of reaction gas humidity was beneficial to uniform distribution of reaction gas.At the same time,changing the reaction gas humidity was also beneficial to the reduction of the volume ratio of water in each parts of the cathode.Therefore,the determination of the best reaction gas humidity can alleviate the cathode water flooding to a certain extent.In conclusion,it has been proved that the selection of operating parameters plays a very important role in the performance improvement of PEM fuel cells.