温度极化对膜蒸馏过程的影响研究

采用直接接触式膜蒸馏，以纯水为料液，考察了材料及结构不同的5种微孔疏水膜的渗透性能．分析结果认为，膜的渗透系数和温度极化系数共同影响着膜通量的大小．实验还考察了料液温度和流率对膜通量及热效率的影响，利用膜及膜两侧边界层内传热传质理论对此进行了分析讨论．因温度极化系数随操作温度变化，可通过控制适宜操作温度获得大膜通量和高热效率．增大料液流率可强化传热，使温度极化减弱，膜通量增加．

Study on temperature polarization in membrane distillation

In this work water transport through five kinds of hydrophobic microporous membrane in direct contact membrane distillation of pure water and the effects of feed temperature and flow rate on the flux and evporation efficency were studied.The measured flux results show that membrane permeability is associated with both permeability coefficient and temperature polarization coefficient.The influence of operating conditions on mass transport rate and evaporation efficiency was discussed by applying traditional mass and heat transfer theories to membrane.The flux does not increase with the feed temperature as fast as the vapour pressure curve because temperature polarization coefficient changes as temperature.The larger flow rate enhances the heat transport and hence the flux increases.