The Study Of Gas-liquid Two-phase Flow Characteristics In Small Circular Channel

Since the concept of MEMS/NEMS,micro chemical technology is widelyapplied in the field of chemical industry.At the same time,the fluid flow in microchannel gets more and more attention.With the miniaturization of the size,the effect ofthe surface tension and wall becomes more significant,the flow state of gas-liquidtwo-phase flow in small channel is very different from the conventionalchannel.Although many experiments for gas-liquid two-phase flow in smallchannels have been carried out,but the flow mechanism inside is still lack enoughunderstanding.This article studies the flow characteristics of gas-liquid two-phaseflow in small channels from the flow patterns,pressure drop and the differentialpressure fluctuation signals.In the two-phase flow test equipment,the4mm and3mm pipe gas-liquidtwo-phase flow invertical upward flow is studied experimentally,and obtainfour typical flow patterns of bubble flow,slug flow,churn flow and annular flowwith high-speed camera.According to the experimental data,draw the flow patternmap, analyze the influence of hydraulic diameter on flow pattern transition bycomparation,and compared the results with T.S.Zhao for2.886mm triangularsection of experimental results to analyze of the influence of cross-sectionshape on flow pattern transition.All kinds of the pressure drop datas are obtained by the experiment,andthe analysis results of experimental datas with the existing pressure drop calculationmodels are compared.Finally we found that the Lee&Mudawar model have betterforecasting results,but the homogeneous flow model don’t have,difficult to meet theneeds of Engineering.For the differential pressure fluctuation signals of the various flow patternsobtained by experiment,we do Hurst index analysis,complexity analysis and chaosform analysis.The results shows that:for gas-liquid two-phase flow in small channel,the H values of different flow regimes is not same, and all less than0.5,showing some degree of anti-persistent.Two complexity measure (approximateentropy and box dimension) is sensitive to the variation of flow type,and can explainthe flow mechanism of two-phase flow well.The chaotic attractor graphs can be usedfor characterizing the dynamic behavior of gas-liquid two-phase flow,and identifythe flow patterns accurately.