气液叉流下受热液膜的热质传递特性

采用VOF两相流模型研究了气液叉流条件下受热液膜热质传递特性,在模型中添加了表面张力源项和气液相间传质源项.为了验证所建立模型的可靠性,采用非接触式红外热成像测温方法,进行了相应的气液叉流试验.对叉流条件下受热液膜热质传递过程进行了试验和模拟计算,结果显示无量纲壁面温度计算结果与试验结果吻合很好.应用所建立的模型,模拟计算并分析了表面张力、固液接触角、液膜流量等因素对液膜流动侧形和热质传递性能的影响,结果表明：在其他参数保持不变的情况下,表面张力从0.014 N／m增大到0.072 N／m的过程中,液膜覆盖面积由82.7％减小到73.2％;固液接触角从30°增大到60°的过程中,液膜覆盖面积由80.6％减小到69.4％;液膜流量越小,液膜厚度越小,越有利于液膜的蒸发;相反,较高的液膜流量会使液膜厚度增大,阻碍了液膜蒸发,从而使外掠过液膜的单位体积空气含湿量减小.

Heat and mass transfer of heated falling film under gas liquid cross flow condition

Based on volume of fluid(VOF) method, heat and mass transfer of heated falling film under gas liquid cross flow condition was investigated. Surface tension and species transport were taken into account. In order to verify reliability of the model, the experiment was performed by non contact infrared thermal imaging technology under gas liquid cross flow condition. Heat and mass transfer of heated falling film under gas liquid cross flow condition was investigated experimentally and theoretically The results show that the simulated dimensionless wall temperature is in good agreement with the  experimental data. Based on the model, the influence of surface tension coefficient, solid liquid contact angle and liquid film flow rate on heat transfer of liquid film was simulated. It is found that, remaining constant of other parameters, liquid film interfacial area decreases from 82.7％ to 73.2％ in corresponding with surface tension coefficient increases from 0.014 N／m to 0.072 N／m, and the liquid film interfacial area decreases from 80.6％ to 69.4％ in corresponding with solid liquid contact angle increases from 30°to 60°. Low liquid film flow rat e makes thin liquid film and is beneficial to evaporation of liquid film. On the contrary, large liquid film flow rate makes thick liquidfilm and lower humidity ratio per unit volume and is harmful to the evaporation of liquid film.