Study On The Flow And Rupture Of Liquid Film In Corrugated-plate Dryer

Corrugated-plate dryer is a kind of equipment, which has the advantages of high separation efficiency,large throughput. But there is a max-inlet-velocity limit to improve the overall performance of the dryer because of the re-entrainment occurred when that was working in high inlet velocity. Liquid film broken by the shear flow at the bending angle of a corrugated-plate may generate fine droplets, which is one of the many factors that cause the re-entrainment phenomenon. But the research on this aspects is still insufficient in the domestic. Therefore,it is of great significance to study improvement of performance of corrugated-plate dryer.Free falling liquid film was firstly studied by Planar Laser Induced Fluorescence (PLIF)method in this thesis. The relation between the thickness of liquid film and the Reynolds number as well as the fluctuation characteristics of liquid film surface were analyzed mainly. It was found that the relation between the liquid film thickness and Reynolds number was in line with the Nusselt theory,where the liquid film Reynolds number was in the range of 600 ?3000. But it turns out that the fluctuation of liquid film surface is not found by the power spectrum density estimation.Renormalization k-? turbulence model in the commercial CFD software Fluent was used to simulate air flow in the experimental set,which is a 2-D single channel of the corrugated-plate dryer. The air backflow existing in the downstream of the bending angle was verified by liquid staining method. And the simulation results indicated that the air velocity around the bending Angle was over three times than the inlet velocity.On the basis of the above research,it was put forward a theoretical model to predict the rupture of the liquid film on a curved wall. The model was applied in the corrugated-plate dryer,it was found out that the theoretical changing trend of the critical velocity to the thickness of liquid film was consistent with the experimental results, and the prediction for the rupture of the larger thickness of liquid film was better. There was a coefficient of structure in the theoretical formula by further analysis, and it was concluded that the highest critical inlet velocity can be obtained when the bending angle equals the optimal value.