Study On Parameter Measurement Method Of Gas-liquid Two-phase Slug Flow In Minichannels Based On Thermal Theories

As more micro devices emerged widely in the related industries, study on two-phase flow in small scale channels draws more attention. Slug flow, which exists over a large range of flow rates, is commonly encountered in minichannels. So the measurement of two-phase slug flow in minichannels is very important. In this thesis, thermal measurement method is applied to two-phase flow measurement in minichannels. A thermal measuring system is designed and constructed, and flow velocity and gas void fraction of gas-liquid two-phase slug flow are obtained using soft-sensing technique.The main work is listed as follows:(1) On the basis of thermal flowmeter for single-phase fluid, a thermal measuring system is designed and constructed for parameters measurement of two-phase flow in minichannels. The sensor, signal conditioning circuit and software have been developed, and the heat transfer of system is analyzed. The experiments of gas-liquid flow are carried out in 3 pipes with inner diameters of 3.34mm,1.26mm and 0.76mm respectively, and the obtained signals can reflect the characteristics of slug flow. Experiment results indicate that the system and thermal measurement method are feasible for two-phase flow measurement.(2) Cross-correlation method of two groups of temperature signals is introduced to detect the average flow velocity. The experiment results are consistent with the actual velocity.(3) Based on theory of Heat Transfer, BP neural network and LS-SVM are applied to construct the mathematical model respectively, and the gas void fraction of the two phase flow is estimated. Research results show that the two methods are effective.