具有透气性侧面的微小流道内气液两相流动的研究

项目名称： 具有透气性侧面的微小流道内气液两相流动的研究

项目编号： No.50876076

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 金属学与金属工艺

项目作者： 王世学

作者单位： 天津大学

项目金额： 45万元

中文摘要： 以质子交换膜燃料电池阴极气体通道内的传热传质问题为应用背景，研究了一个侧面由透气性多孔材料构成的毫米尺寸的方形通道内，液态水通过透气性侧面渗入到气体通道并最终由通道出口排除过程中各种因素对该类传质问题的影响。首先，通过电极表面的可视化实验研究了燃料电池各种运行条件下电极表面液态水的生成及排除规律，发现大化学当量比或低加湿条件下几乎没有液态水，其它条件下其多在通道出口附近出现聚集。其次，基于上述燃料电池的运行实验结果，通过理论分析研究了含水条件下多孔介质气体扩散特性的变化，指出含水饱和度对相对扩散系数的影响是严重非线性的（2.5次方以上）。第三，研究了多孔材料特性对液态水进入通道的影响，指出除孔径和孔隙率外，材料导热系数也明显影响液态水在多孔壁面上的蒸发和排除。第四，从理论和实验两方面研究了单一液滴在微小流道内生成及排除现象，发生壁面的表面特性（亲水性和疏水性）对液滴的脱离和排除没有明显影响，液滴脱离高度随雷诺数增大呈指数衰减。最后，模拟燃料电池内化学反应生成水的产生过程，研究了液态水沿流动方向逐渐渗入时通道内气液两相流动的流型，给出了流型对气液流量的依存关系及其对通道压降的影响。

中文关键词： 微小通道；气液两相流；多孔材料；扩散特性；燃料电池

英文摘要： According to the mass and heat transfer during the cathode channel of proton exchange membrane fuel cell, in a mm-order square channel whose wide wall materials were permeable and porous, various potentiality, which affected the mass transport during the procedure of liquid water passing through the permeable side walls and reaching and ending up with exiting the flow channel, were experimentally studied. (1) The rule of how liquid water developing and disappearing on the MEA surface were studied through the visualization experiments of MEA surface. The results indicated that: at high stoichiometric ratio or low humidification ratio of reactant there is little liquid water, and at other conditions the liquid water was developed and assembled near the exit of flow channel. (2) According to the above fuel cell experimental result data, a theoretical analysis of gas diffusion characteristics, when the porous media is under liquid water condition, was developed. The analysis results show that: water saturation developed with the relative diffusivity at a badly nonlinear pace (over the power of 2.5). (3)How the porous materials characteristics influenced the liquid water being transferred into the channel was studied, and the results show that: besides pore size and porosity, thermal conductivity coefficient also had major influence on the water evaporation and exclusion on the porous wall. (4)The development and exclusion of single droplet during a tiny flow channel was studied in theory and experiment dividedly. The results showed that the wall surface characteristics (hydrophilic and hydrophobic) made little difference on divorce and exclusion of droplets. The divorce height of droplets was badly decayed with the increasing of Reynolds number. (5)The production process of water which was the chemical reaction product in fuel cell was simulated. The flow pattern for two-phase flow of gas and liquid when the liquid water gradually permeated into channels along flowing direction was also studied. The results also indicated the relationship between the flow pattern and gas and liquid flux, and the influence of flow pattern on the pressure drop in the channel.

英文关键词： mini-channel;gas liquid two-phase flow;porous material;diffusion character;fuel cell