Simulation Of Wall Properties' Effects On Multiphase Flow In T-junction Micro-channel

With the concept of microfluidic chip and micro-heat pipe proposed.Research of micro-channel multiphase flow arise more and more researchers' attention.How to enhance the efficiency of heat and mass transfer in micro-channel has become an urgent problem.In this article,the influence of wall's properties on the efficiency of heat and mass transfer in smooth micro-channel has been studied.Besides,the influence of blocks' distance,relative surface roughness,blocks' shape and blocks' surface wettability on the efficiency of heat and mass transfer in the T-junction micro-channel has been studied.The specific results as follows:Firstly,under particular conditions,by setting a block in the channel,the efficiency ofheat and mass transfer in the T-junction micro-channel has been enhanced.Small volume with high-frequency droplets has been produced in the T-junction with a rectangular block.In this condition,when keep the walls' heat quantity as constant,The wall's average Nusselt number has been increased.When keeping the flux of continuous as constant,the characteristic diameter and frequency of droplets decreases with the flux of disperse decreases.Secondly,the influence of block's wettability on the droplets' motor process has been studied.Results show that keeping channel wall's contact angle ?w=140° as constant,bubbles can be controlled to move on the upper wall or on the lower wall effectively by changing the value of ?b:when ?w??b,bubbles move on the lower wall;when ?w>?b and ?b's value is around 110°,bubbles move on the upper wall;when ?b's value decreases further,there exists bubble's coalescence in the micro-channel,in this case,bubble's volume is the largest and bubble's frequency is the smallest.Besides,the flow ratio Q has an important impact on the bubble's generation,when ?b=110?,Q?30,there also exists bubble's coalescence in the micro-channel.Finally,the flow and heat transfer process in a rough T micro-channel with a trapezoidal block is studied.The results show that the droplets' diameter and velocity decrease with the increase of roughness spacing ratio,and increase with the wall's relative roughness.When keeping the wall's heat flux as a certain value,the average Nu number of the micro-channel wall decreases with the increase of roughness element spacing ratio,and increases with the relative roughness of the wall.When studying the influence of blocks'shape on the efficiency of the mass and heat transfer.Micro-channel with rectangle block is the optimal choice.At last,it is found that when the wettability of the rough surface is stronger,the mass loss of the dispersed phase droplets will occur when passing through the micro-channel.