Study On Thickness Of Condensate Film In Tube By Laser Interferometry

The process of vapor condensation in the tube involves a complex vapor-liquid two-phase flow,and the thickness of the vapor condensate film in the tube has a great influence on the condensation heat transfer characteristics.Due to the complicated working conditions of the condensed liquid film in the tube,the measurement of its thickness is difficult.Analysis of the reported research results,using laser interferometry to measure the thickness of the vapor condensate in the tube is a highly accurate and feasible method.Based on the principle of interferometry,combined with the CCD camera image acquisition system,this paper provides a non-contact,high-precision test method for measuring the thickness of condensate film in the tube.Based on the optical path geometry principle,the calculation method of the number of interference fringes and the thickness of the liquid film is obtained.The experimental method of obtaining the scattering angle of the coherent beam by using the spectrometer is designed,and the processing method of obtaining the angle data from the interference picture based on OriginPro software is designed.Finally,based on the above principle,the steam system and the test optical path system were built,and the measurement of the thickness of the condensed liquid film in the tube was completed.The work includes the following aspects.(1)The influence of liquid film thickness on the condensation process in the tube was analyzed.The published significance results of the liquid film thickness measurement method was discussed and several existing liquid film thickness measurement methods were introduced,and its advantages and disadvantages in the experimental process were explained.The current development and achieved advantages of laser interferometry are introduced.(2)Based on the optical path geometry principle,the calculation method of the number of interference fringes and the thickness of the condensed liquid film was established,and the corresponding calculation program was compiled.Based on the experimental principle,the optical path system and the steam system were built.The scattering angle measurement system and the interference fringe image acquisition system were designed.The acquisition of the interference image of the condensate film thickness is completed.(3)Using the ESPI software to collect the interference fringe image in real time,and use the OriginPro software to process the acquired interference fringes.Angle data of the two scattering positions of the light beam is obtained.(4)Interferometry experiments were carried out on glass tubes with different wall thicknesses.It was found that the thicker the wall,the more the number of stripes and the less clear the stripes.When the wall thickness is too large,since the light intensity of the coherent beam is too weak,the interference fringe of the thickness of the condensed liquid film isdifficult to discern.Finally,after the many tryings,a glass tube with a thickness of 3 mm was selected for the experiment,and a relatively clear interference image of the condensed liquid film thickness was obtained.(5)The experimental results show that the number of interference fringes has a linear relationship with the thickness of the liquid film.As the difference in scattering angle increases,the thickness of the liquid film decreases,and the thickness of the liquid film increases with the inner diameter of the tube.