Experimental Study on Hydrodynamic Behavior of Falling Film over Vertical Tube

Falling film configurations play an important role in characterizing the heat transfer due to changes in hydrodynamic behavior.The purpose of this study is to establish a novel film distributor to investigate the hydrodynamic behavior of the falling film on the vertical tube.The falling film thickness and flow patterns on the vertical tube were analyzed at a feed water temperature of 30℃ for film Re ranged from 53 to 4544 and the heat fluxes ranged from 1.33 to 49.45 kW/m2.The correlation between the average falling film thickness and the film Re was fitted;the maximum deviation between the experimental data and the predicted values was 7.58%.Additionally,the film thickness changed sharply when the heat flux increased to a certain value.With the further increase of the heat flux,dry patches appeared on the surface of the experimental tube.There was Marangoni effect on vertical tube and the falling film thickness and flow patterns were significantly affected by heating.The interval value of the critical heat flux with film Re was obtained.Compared with the porous film distributor reported in the literature,the critical heat flux of the new film distributor increased by 3.72%-56.95%.