Research On Two-phase Flow Interfacial Parameters In Narrow Rectangular Channels Under Steady And Pulsating Condition

This paper deals with the experimental research on the interfacial parameters like void fraction,bubble density,interfacial area concentration and Sauter mean diameter in the horizontal narrow rectangular channel under steady and pulsation conditions.The experiment was carried out in the pulsation platform and the purified water and nitrogen was adopted as working fluid.The test section was one narrow rectangular channel with the width of 40 millimeter and the height of 4 millimeter.The control of water mass flow rate was done by frequency converter and sine wave generation software.A HD camera was used to capture the two-phase flow condition inside the channel and a set of Matlab code was compiled to post process the images to obtain a large number of experimental interfacial parameters.The experimental results in steady conditions show that the radial distribution of void fraction can be categorized into two groups,namely off-center peak type and core peak type.The main characteristics of core peak type in narrow rectangular channels is as similar as those in round channels while off-center peak type represents small variations around the channel core and reach the maximum between the center line and the wall.This is probably due to the wall force inside the rectangular channels.The IAC predictions from five classic models perform poorly when comparing with the experimental IAC results,which can be explained by their limited application only in round channels with large diameters.Based on the experimental IAC,the formula that fitted specified narrow rectangular channel was proposed.The experimental results in pulsation conditions show that pulsation has an influence on both mean and transient characteristics of two-phase interfacial parameters.When discussing with the mean characteristics of those interfacial parameters,time-averaged values of these parameters in the pulsation condition can be either larger or smaller than those of steady conditions.This is closely related to the bubble size in the rectangular channel.The impact of pulsation on the transient characteristics of those interfacial parameters is quite complicated since different pulsation variables have different influences.The pulsation period(from 10 second to 20 second)has no influence.At relatively small pulsation amplitudes,void fraction,IAC and Sauter mean diameter all change gently with the transient water flow rate;at relatively large pulsation amplitudes,void fraction,IAC and Sauter mean diameter all have two valley values.The variations of water flow rates result in different phase lags between water flow rate and specified interfacial parameters.