Experimental Study On The Flow And Heat Transfer Of Falling Liquid Film On Inclined Plate

Falling liquid film is widely used in production and life.Research on falling liquid film is still ongoing.Among them,liquid flow,liquid film fluctuation,liquid film thickness and liquid film heat transfer still require further research.In this paper,the experimental study on the flow and heat transfer characteristics of the falling liquid film on the inclined plate is carried out,aiming to further study the characteristics of the liquid film and provide a theoretical basis for the application of the falling liquid film in seawater desalination.In this paper,the flow of the falling liquid film on the inclined copper plate was studied by image method.The liquid film flow state was observed by charge coupled device,and the effects of Reynolds number and liquid film falling angle on the liquid film flow state were analyzed.By using MATLAB to process the captured image,the fluctuation of the liquid film is analyzed.The results show that on the surface of the falling liquid film,the shape of the corrugation is random,the wavelength decreases along the flow direction,and the wavelength decreases with the increase of the falling angle of the liquid film.By measuring the thickness of the liquid film on the inclined copper plate with a white light confocal displacement sensor,the variation of film thickness was summarized,and the effects of the Reynolds number and the falling angle of the liquid film on the fluctuation amplitude and average film thickness of the liquid film were analyzed.The results show that the film thickness at any point on the inclined copper plate changes with time,and the film thickness decreases gradually along the flow direction;the fluctuation amplitude of the falling liquid film increases with the increase of the Reynolds number and the falling angle of the liquid film,and the average film thickness increases with the increase of the Reynolds number and decreases with the increase of the falling angle of the liquid film.The experimental study on the heat transfer characteristics of the liquid film falling on the inclined wall is carried out.The distribution law of the local heat transfer coefficient of the liquid film along the flow direction is summarized.The effects of heat flux,liquid film initial temperature,working fluid salinity and liquid film thickness on local heat transfer coefficient and average heat transfer coefficient were analyzed.It is found that the local heat transfer coefficient of the liquid film on the inclined plate decreases with the increase of the liquid film flow distance.The heat flux has no effect on the local heat transfer coefficient.The local heat transfer coefficient increases as the initial temperature of the liquid film increases.The local heat transfer coefficient of seawater is less than that of pure water.When the falling angle of the liquid film decreases,the thickness of the liquid film increases,the fluctuation slows down,and the local heat transfer coefficient of the liquid film decreases.The effects of heat flux density,liquid film initial temperature,working fluid salinity,and liquid film thickness on the average heat transfer coefficient are the same as those on the local heat transfer coefficient.