Simulation Of Water Transfer In Proton Exchange Membrane

Fuel cell is considered as the preferred clean and efficient power generation technology in the 21st century due to it have high power generation efficiency,non-pollution,can work continuously for a long time,and is noiseless.Proton exchange membrane fuel cell(PEMFC)has become the fuel cell with the fastest development,is the most widely used and the most promising.PEMFC is a new generation of energy power system with energy revolution significance,highly regarded by the governments and enterprises.Proton exchange membrane is the key technical material of PEMFC.It is not only a compact selective permeation membrane,but also the base of electrolyte(transfer protons)and electrode active materials(catalysts).It is the heart of the whole cell.The higher the water content is,the better the Ionic conductivity is in the membrane.The transmission and distribution of the internal water have a great impact on proton conduction,dissolution and diffusion of oxygen in the membrane,which will directly affect the performance of PEMFC.Therefore,keep the water content in the membrane balance is important to the performance of PEMFC.Due to proton exchange membrane is very thin,about only dozens of micron,it is very diffcult to mensurate the water content in the membrane,espetially research by the way of experiment directly.So it can only research by the way of simulation currently.Therefore,the paper adopted the method of modeling and simulation to carry on the theoretical study on the distribution of the water concentration in proton exchange membrane.It narrated model of water delivery mechanism in the proton exchange membrane and the influence factors of water delivery in the membrane.It used Springer's membrane diffusion model based on appropriate improvement to establish a new mathematical model.and used software to establish three-dimensional model to carry out simulation.Then it calculated the water concentration distribution in the proton exchange membrane according to the definition formula of concentration gradient and the analog results which is the water concentration gradient and the water concentration distribution on the anode/cathode of membrane.The results indicated that the directon of concentration gradient on the same surface of membrane is not homogeneous.At the inlet,concentration gradient value close to the anode side of membrane is greater;At the outlet,concentration gradient value close to the cathode side of membrane is greater.The general trends of water concentration on the surface of cathode and anode are the same.They all show the trend of parabola increasing along the flow direction.But the values of water concentration on the cathode are significantly higher than the anode side.The change rate of water concentration in the membrane along the flow direction is the minimum at the inlet,second in the middle position,maximum at the outlet.From the anode to the cathode of membrane,water concentration at the inlet is increased gradually;Although there is a short downward trend near the 1/2 thickness of membrane at the outlet,the water concentration is always the greatest.Water concentration close to the anode side in the middle position is the lowest throughout the whole membrane along the thickness direction,which is much lower than the inlet.It is more prone to generate water shortage here.