Experiment Research On Characteristics Of Heat And Mass Transfer Through Porous Media Plate

Proton exchange membrane fuel cell(PEMFC)is a kind of highly efficient,non-polluting and new-developed power sources.It has many advantages,such as high energy density,fast starting and wide fuel source.The water content of proton exchange membrane has great effects on proton conduction ability and the mechanical strength of membrane,which may produce side effects to fuel cell performance.So it is necessary to carry out appropriate water management for the fuel cells.The reaction water inside the battery alone cannot be used for reaching a water balance at any working condition,so an effective way is to use an external humidifier to humidify inlet gas of cathode.In this paper,a kind of PEMFC external humidifier which uses porous media carbon plate as a core technology was studied.The influence factors of heat and moisture transfer characteristics of porous media carbon plate were studied experimentally.In this paper,an experiment system for measuring heat and mass transfer through porous media plate was designed.This system was composed of two gas circuits.The calculation of heating and humidifying device parameters in this experiment system was carried out,that can ensure the smooth running of experiment system.In addition,water balance of the whole experiment system was investigated,and the errors were evaluated.In this paper,the influence of flow parameters on characteristics of heat and mass transfer through porous media plate was studied.When using the same porous media plate,the gas flow rate,temperature and humidity of humidifying gas were researched respectively.Results show that the increase of gas flow was conducive to temperature increasing of humidifying gas,which has a promoting effect on moisture transfer,but it can lead to decrease of water recovery rate.The improvement of relative humidity of humidifying air was beneficial to promote the temperature of humidified gas,improve the amount of moisture transmission,but which can lead the reduction of water recovery ratio.The increasing of humidifying gas temperature obviously promoted the increasing of the humidified gas temperature,the amount of moisture transmission and water recovery ratio.So the inlet temperature of humidifying gas could improve the heat and mass transfer performance of humidifier.In addition,the influence of physical parameters of porous media plate on heat and mass transfer characteristics were also studied.The different types of porous media plate were used.Experimental study under different fluid parameters was carried out respectively.Results showed that: with the increasing of inlet relative humidity of humidifying gas,the difference of heat and mass transfer performance became more obvious when the ribbed surface was in the high and cold temperature side.When the ribbed surface was on humidifying side,heat and mass transmission was promoted.In addition,the increasing of porosity of porous media plate obviously promoted the capacity of moisture transmission.