Study On Laser Interferometric Measurement Of Condensation Film Thickness

With the large-scale application of steam turbine generator sets in my country,in order to break through the limitation of water scarcity in my country's rich and low water areas,air condensers have been widely used.Condensation heat transfer in the tube in the condenser is a complicated gas-liquid two-phase flow process.The thickness of the condensed liquid film is used as the main thermal resistance in the condensation heat transfer process.The thickness of the condensed liquid film and its distribution are accurately measured.Heat plays an extremely important role.However,the environment in which the thickness of the liquid film is located is more complicated,and the requirements for the measurement method are relatively high.After reading the relevant literature,this article uses laser interferometry to measure the thickness of the condensed liquid film in the vertical tube.This paper uses CCD camera,image acquisition card,ESPI software and screen recording software to form the interference fringe acquisition system;through the helium-neon laser light source,beam lifter,mirror,attenuator and spectrometer to build the optical path system;using electric heating jacket,A three-necked flask,thermocouple and rubber tube construct a steam generation and transmission system;Free Video to JPG Converter software and Origin Pro software are used to post-process the pictures to obtain the key data for thickness calculation.The specific research content and conclusions of the thesis are as follows:(1)Derive the calculation formula for the thickness of the glass tube based on the principle of laser interference,and write the mathematic program for calculating the thickness of the glass tube;(2)Conduct wall thickness experiments on glass light pipes,and the maximum error of the experimental results is within 5%,which verifies the accuracy of the method;by adjusting the height of the beam lifter and CCD camera,the thickness of the glass tube is measured along the axial direction.Circumstances,the maximum error of the measurement results is within 6.5%,which verifies the feasibility of the method;(3)Experiments on glass light pipes have obtained the relationship between wall thickness and included angle.When the included angle is less than 27.5°,the error is within5%;when the included angle is 33.12°,the error reaches 9.34%.Provide reference for follow-up experiments;(4)Using pure water as the steam generating medium,the axial liquid film thickness experiment was carried out on glass tubes of different diameters under different voltages.The change curve of the thickness of the liquid film along the axial direction under the same pipe diameter and different heating power is obtained.With the increase of heating power,the thickness of the liquid film first becomes thicker and then becomes thinner;and when the heating power is the same but the pipe diameter is different The thickness changes along the axial direction,and the thickness of the liquid film becomes thicker as the pipe diameter increases;(5)Using tap water as the steam generating medium,test the glass pipes with different pipe diameters under the same voltage.Obtained the change rule of the liquid film thickness along the axial direction when the pipe diameter is the same and the steam generating medium is different.The thickness of the liquid film corresponding to pure water is thicker than that of tap water.