论文部分内容阅读
The falling thin film flow has advantages such as the short contacting time between the processed fluid and heated surface,high heat flux,minimal pressure drop,minimal static head and small process fluid hold up.A numerical study of the falling film flow of water on the internal face of a vertical tube was investigated [1-3].Among the previous studies,a large portion of the investigations focused on co-current flow in vertical flow ducts.Only limited investigations have been performed for downward flow [4].In this study,a flow of air enters the vertical tube at constant velocity in the upwards direction while water film flows along the wall surface under the influence of gravity.Three models were proposed and the profiles of liquid phase volume fraction,the velocity and the turbulent kinetic energy were presented.With the liquid velocity fixed the appropriate gas operating rang was determined.The variation of liquid film thickness along the flow direction and the time variations of liquid film thickness were discussed as well.The distribution of liquid film velocity was analyzed.A comparison between the results obtained for studied water in the same conditions was made.