| The polymer electrolyte in PEMFC requires a suitable supply of water to maintain proton conductivity.Excessively high water content leads to electrode flooding and pore blocking in the GDL while low content results in low proton conductivity.It is difficulty to maintain PEMFC performance when it is lack of water, so the humidification is essential for PEMFC.In this task,porous carbon plates are selected as key material in PEMFC humidifier.This porous carbon is low density,thermal conductivity and under certain pressure the fluid can through it.When the cell is running,high-temperature circulating water gets across the pores of carbon plate to infiltrate into reaction gas side.The infiltration water absorbs the heat from the recycled of water-side for evaporation,and the gas also absorb heat for reaction gas heating.This humidifier is high efficiency,small size,light weight,no force support,and the water amount is easy to control.The humidifier effectively use of exhaust heat of the PEMFC.This paper can be summarized as water seepage characteristics of porous carbon plate and the design,production,performance testing of the humidifier.Study found that:(1)The effective porosity and pore size work together on the seepage,more effective porosity and high aperture result in greater volume of water seepage.The penetration rate of 6.8%effective porosity of carbon plate is 1.5md;(2)As the pressure increased,water infiltrates faster.Under the pressure of 30kpa,the infiltration rate of 6.8%effective porosity of carbon plate is 0.56 g/cm~2·min.When the water seepage is great,the ambient temperature(fuel cell operating temperature range)little effect on water seepage,because the seepage rate is much faster than the rate of evaporation;(3)At the pressure of10kpa,when no gas passes the porous carbon plate humidifiers,the water in the flow can not be discharged,and the infiltration capacity is low.The infiltration rate is15g/min.Once the gas has passed,the air brings the water out of the humidifiers,and the infiltration capacity increases to50g/min. When the air flow increase,the liquid water on the carbon plate's surface has been blown off,but the absence of a large number of heat sources,the water film on carbon plate's surface can not be evaporated,the volume of water seepage does not increase. When the gas temperature gets high,the heat gas contained is too small compared to the latent heat,so it also can not make liquid water evaporation,seepage is also difficult to increase;(4)With circulating water temperature increases,there is larger temperature differentia on both sides of the panels,a large number of heat transfers to another side. The liquid water evaporation speeds up,and the water film on the carbon surface easy to evaporate,seepage capacity grows faster,and at the pressure of 7kpa,the infiltration rate is 44g/min.When the temperature is further increased,the gas into the humidifiers will soon reach saturation,so the evaporation can not continue.The volume of water seepage is no longer increase.Then the temperature difference between import and export of recycled water is no longer continued to increase. According to the above conclusions,we can predict that with the air flow increasing the water amount will increase,while recycled water temperature difference will become large.(5)At the pressure of 35kpa,the infiltration rate is about 400g/min.This humidifier can meet the demand for 10KW fuel cells.
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