Research On Porous Media Humidifier Of Fuel Cell

PEMFC (Polymer Electrolyte Membrane Fuel Cell) is highly efficient, nonpolluting power source. Exhaust of PEMFC is mixed gas of steam, nitrogen, oxygenand so on, without any pollution. Compared with other power sources, PEMFC have ahigher energy conversion efficiency. Therefore, the fuel cell vehicles are beenconsidered to be new energy vehicles with extensive competitiveness. Protonconduction rate is an important parameter which affects the performance of the protonexchange membrane Fuel Cell. And proton exchange membrane water contentdetermines proton conduction rate. If reaction gas without humidification can causedehydration of proton exchange membrane, causing ohmic loss increases and damagethe proton exchange membrane. And humidifying excessive can also caused thedeterioration of the performance of fuel cell due to flooding and other reasons.Therefore, research on fuel cell humidifier and humidification method, has been a hotresearch at home and abroad.In this paper, a kind of fuel cell humidifier which used porous media plate wasstudied. The porous media plate was used to directly transfer the moisture which wasfrom the high temperature and high humidity exhaust of fuel cell to air so that it canbe humidified. Through this way, the humidification efficiency and stability ofhumidifier can be improved, thus the stability of the fuel cell operation can also beimproved. But during the process of humidifying, the humidifying mechanism and theinfluence of various parameters on the humidifying were not clear, therefore, throughthe establishment of theoretical model, simulation analysis, experiment and research,we can study the moisture transfer through porous media plate.The theoretical model we built based on the capillary pressure of porous media.It took the saturation of porous media and the moisture content of fluid as variables,and the theoretical analysis was done for the whole process. Based on the theoreticalanalysis, the simulated calculation was taken. Porosity, permeability, thermalconductivity, the temperature of the fluid in the runner, moisture content, theinfluence of the flow velocity on moisture and heat through porous media plate wasanalyzed. Results of the research showed that the porosity and permeability of porous media had a little impact on distribution of saturation in porous media, so the impacton the moisture movement is not obvious. Improvement of the coefficient of thermalconductivity of porous media plate can also improve the moisture transfer throughporous media plate, which was especially apparent in the condition of low coefficientof thermal conductivity and high gas velocity.The experimental study was also carried out, the research showed that porousmedia can greatly transfer the moisture. Appropriately choice of porous media platecan meet the requirements of fuel cell for moisture content, and reduction of the flowvelocity and improvement of inlet humidity ratio can significantly improve moisturetransfer through porous media plate.