Error analysis and liquid film thickness measurement in gas–liquid annular flow

The parameters measurement of liquid film in gas–liquid two-phase annular flow is of great significance for the study of heat and mass transfer and flow characteristics. The paper focuses on the thickness measurement and flow evolution analysis of the liquid film in downward gas–liquid two-phase annular flow. Compared with the traditional measurement methods, the method combined the laser-induced fluorescence (LIF) technique with the high-speed photography is developed to measure the liquid film thickness and analyze the flow distribution. Firstly, the geometric optical path model of the organic glass pipeline was established based on the Gauss optics to recognize the real and virtual film images and quantitatively estimate the measurement linearity. And then the digital image processing technology was developed to achieve non-intrusive measurement of liquid film thickness. Finally, the film thickness distribution in downward gas–liquid two-phase annular flow was further analyzed. The method can avoid the interference with the flow field. Meanwhile, the measurement results by experiment show that the film thickness manifests stochastic distribution, which corresponds to the features of randomness and small flow in the process of liquid film flow.