壁面性质对蛇形微通道流动特性的影响
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摘要
采用CLSVOF方法,以空气和水为介质,对不同壁面性质的矩形截面蛇形微通道内气液两相流动进行模拟研究。验证模型的合理性后,改变粗糙度及雷诺数Re,讨论其对泊肃叶数Po和努塞尔数Nu的影响并分析其影响机制;改变壁面接触角及粗糙度,探讨其对微通道内流体流动的综合影响;由于蛇形微通道特有的回转弯道,针对几种具有不同壁面性质的通道组合情况对流体流动特性进行研究。计算结果表明,壁面粗糙度的增加对Po的影响高于Nu,且可强化传热;壁面粗糙度对亲水壁面与疏水壁面的影响效果相反;当直微通道为亲水性光滑壁面、回转弯道为疏水性粗糙壁面时,其传热效果更好。
With air and water as medium,a numerical analysis of gas-liquid two-phase flow and heat transfer characteristics in serpentine micro-channel was made using the CLSVOF(coupled level set and volume of fluid)method multiphase model.After verifying the rationality of the model with the experiment,by changing the relative roughness and Re,the influences of them on Po and Nu were discussed,and the influence mechanism was analyzed.In means of changing the contact angle and relative roughness of the wall,the combined effect of them on fluid flow in micro-channel was discussed.Flow characteristics for several kinds of channel combinations with different wall surfaces were studied because of the unique curve part of serpentine micro-channel.The calculation results show that the increase of relative roughness has greater influence on Po than Nu,and can enhance heat transfer.The effects of relative roughness on hydrophilic wall and hydrophobic wall are opposite.When the straight part is hydrophilic smooth wall and the curve part is hydrophobic rough surface,the heat transfer is better.
With air and water as medium,a numerical analysis of gas-liquid two-phase flow and heat transfer characteristics in serpentine micro-channel was made using the CLSVOF(coupled level set and volume of fluid)method multiphase model.After verifying the rationality of the model with the experiment,by changing the relative roughness and Re,the influences of them on Po and Nu were discussed,and the influence mechanism was analyzed.In means of changing the contact angle and relative roughness of the wall,the combined effect of them on fluid flow in micro-channel was discussed.Flow characteristics for several kinds of channel combinations with different wall surfaces were studied because of the unique curve part of serpentine micro-channel.The calculation results show that the increase of relative roughness has greater influence on Po than Nu,and can enhance heat transfer.The effects of relative roughness on hydrophilic wall and hydrophobic wall are opposite.When the straight part is hydrophilic smooth wall and the curve part is hydrophobic rough surface,the heat transfer is better.
引文
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[3]曲新兴,张佑杰,贾海军,等.板状燃料组件窄缝流道流速分布实验研究[J].原子能科学技术,2003,37(6):519-522.QU Xinxing,ZHANG Youjie,JIA Haijun,et al.Experimental research on velocity distribution in narrow slots of plane type reactor fuel[J].Atomic Energy Science and Technology,2003,37(6):519-522(in Chinese).
[4]MOODY L F,PRINCETON N J.Friction factors for pipe flow[J].Transactions of the ASME,1944,11:671-684.
[5]WU P Y,LITTLE W A.Measurement of the heat transfer characteristics of gas flow in fine channel heat exchangers used for microminiature refrigerators[J].Cryogenics,1984,24(5):415-420.
[6]MALA G M,LI D.Flow characteristics of water in mirotubes[J].Heat Mass Transfer,1992,20(7):142-148.
[7]ZHU X Y,ZHU L,CHEN H J,et al.Fabrication of multi-scale micro-lens arrays on hydrophobic surfaces using a drop-on-demand droplet generator[J].Optics and Laser Technology,2015,66(9):156-165.
[8]MA M,HILL R M.Superhydrophobic surfaces[J].Current Opinion in Colloid and Interface Science,2006,11(6):193-202.
[9]WU Y,GAO S.Developent of free adjustable function generator for drop-on-demand droplets generation[C]∥Advanced Future Computer Control System.Herdelberg,Berlin:Springer,2012.
[10]CHEN W C,WU T J,WU W J,et al.Fabrication of inkjet-printed SU-8photoresist microlens using hydrophilic confinement[J].Micromech Microeng,2013,23(6):65-78.
[11]KIM J Y,PFEIFFER K,VOIGT A,et al.Directly fabricated multi-scale microlens arrays on a hydrophobic flat surface by a simple ink-jet printing technique[J].Journal of Materials Chemistry,2012,22(7):353-358.
[12]BRACKBILL J U,KOTHE D B,ZEMACH C.A continuum method for modeling surface tension[J].Computer Physics,1992,100(6):335-354.
[13]PELEVIC N,van der MEER T H.Heat transfer and pressure drop in microchannels with random roughness[J].International Journal of Thermal Sciences,2016,99(6):125-135.
[14]WENZEL R N.Resistance of solid surface to wetting by water[J].Industrial&Engineering Chemistry,1936,28(3):988.
[15]CASSIE A B D.Contact angles[J].Discussions of the Faraday Society,1948,3:11-16.
[16]胡广,胡刚义.粗糙度对微通道流动特性的影响研究[J].船舶电子工程,2015,35(8):57-60.HU Guang,HU Gangyi.Effects of roughness on gaseous flow characteristics in microchannels[J].Ship Electronic Engineering,2015,35(8):57-60(in Chinese).
[17]SONG M,KIM H Y,KIM K.Effects of hydrophilic/hydrophobic properties of gas flow channels on liquid water transport in a serpentine polymer electrolyte membrane fuel cell[J].International Journal of Hydrogen Energy,2014,39(8):19 714-19 721.
[18]CROCE G,AGARO P D.Numerical analysis of roughness effects on microtubes heat transfer[J].Super Lattices Microdt,2004,35(3):601-616.