μDMFC流场板润湿特性对气液输运的影响

摘要

Miniaturization of μDMFC flow channel increases the flow resistance of fluid in the channel.It is easy to make CO2 bubbles block channel.It not only affects the transporting of methanol solution,but also hinders the mass transfer of methanol to the catalyst layer,and decreases electrochemical reaction efficiency.Therefore,it is necessary to improve the transporting properties of gas-liquid in tμDMFC anode channel.The effects of double flow field plate trench sidewall surface wetting properties on gas-liquid two-phase distribution were studied based on the VOF method,and gas-liquid two-phase flow of μDMFC anode channel was simulated by using CFD software FLUENT.It is shown that gas-liquid two-phase in single flow field plate channel renders segmented flow phenomena,and gas-liquid two-phase in double flow field plate channel presents stratified flow phenomena;containing gas rate in double flow field plate is lower than that in the single layer flow field plate channel and pressure drop characteristics of the former is better than the latter.At the same time,the upper layer of the two-layer flow field plate trench sidewalls is hydrophobic,and the lower is hydrophilic,not only good for gas and liquid transportation,but also conducive to the methanol mass transfer.It provides a kind of effective method to enhance the performance of μDMFC.%μDMFC流场沟道的微型化增加了流体在沟道中的流动阻力,容易使CO2气泡堵塞沟道,不仅影响甲醇溶液的输运,而且还会阻碍甲醇向催化层传质,降低电化学反应效率,因此需要改善μDMFC阳极沟道的气液输运特性.基于VOF方法,采用计算流体力学软件FLUENT对μDMFC阳极沟道内的气液两相流进行数值模拟,研究双层流场板沟道侧壁面润湿特性对气液两相分布的影响.结果表明:单层流场板沟道内气液两相呈现分段流动现象,而双层流场板沟道内的气液两相呈现分层流动现象;双层流场板沟道内的含气率明显低于单层流场板沟道,并且压降特性前者优于后者;同时双层流场板沟道侧壁上层为疏水性,下层为亲水性时,不仅有利于气液输运,还有利于甲醇传质,为提升上DMFC的性能提供了一种有效的方法.