Visualization study of flow patterns for ethanol-water mixtures condensation in microchannels

doi:10.11949/j.issn.0438-1157.20150399

Abstract

Abstract:

A visualization experiment was carried out to investigate the condensation flow patterns of the ethanol-water vapor mixtures in an array of microchannels under a wide range of concentration (2%—60%). The microchannel was a trapezoidal silicon one with a hydraulic diameter of 165.87 mm and a length of 50 mm. The visualization study indicated that the ethanol concentration remarkably influenced the flow regimes. Along the flow direction, annular, annular-streak, annular-streak-droplet, annular-churn, injection, droplet-injection and bubble flow patterns were observed in the vapor mixtures condensation of different inlet ethanol concentration (60%, 31%, 20%, 6%, 4%, 2%). Due to the Marangoni effect, the film of the annular flow was more fluctuant comparing with the pure steam condensation. With the decreasing of the ethanol concentration, the injection flow pattern became more regular and the droplet would appear in the injection flow area. The two-phase flow pattern maps of different inlet ethanol concentrations were also developed to describe the experiment. A correlation based on the critical quality correlation was proposed to indicate the transition of the two-phase flow patterns.

Key words: microchannels, condensation, two-phase flow, binary steam, Marangoni effect

摘要：

利用高速摄像系统对梯形硅基微通道进行乙醇水混合蒸气冷凝流型可视化实验。梯形微通道结构为梯形,水力学直径165.87 mm,通道长度50 mm。实验中混合蒸气乙醇质量分数范围为2%～60%。实验发现入口蒸气乙醇浓度对通道内流型有重要影响。沿着冷凝方向,发现环状流、环状条纹流、翻滚流、喷射流/喷射滴状流及气泡流。不同蒸气入口乙醇质量分数有不同的流型分布,低乙醇浓度的蒸气冷凝环状条纹流及喷射流区域出现伪滴状凝结形式,高乙醇浓度的蒸气冷凝出现翻滚流流型。实验以蒸气质量通量及蒸气干度为坐标对不同入口浓度蒸气冷凝建立了两相流型图,并对喷射流发生干度建立了流型转变预测式。

关键词: 微通道, 凝结, 两相流, 混合蒸气, Marangoni效应

CLC Number:

O359⁺.1

JIANG Rui, MA Xuehu, LAN Zhong, BAI Tao, BAI Yuxiao. Visualization study of flow patterns for ethanol-water mixtures condensation in microchannels[J]. CIESC Journal, 2015, 66(11): 4320-4326.

姜睿, 马学虎, 兰忠, 白涛, 白玉潇. 梯形微通道内乙醇水混合蒸气冷凝流型可视化实验[J]. 化工学报, 2015, 66(11): 4320-4326.

References 22

[1]	Quan X J, Chen P, Wu H Y. Transition from annular flow to plug/slug flow in condensation of steam in microchannels [J]. Int. J. Heat Mass Transfer, 2008, 51(3): 707-716.
[2]	Chen Y P, Chen P. Condensation of steam in silicon microchannels [J]. International Communications in Heat and Mass Transfer, 2005, 32(1): 175-183.
[3]	Wu H Y, Yu M M, Cheng P, Wu X Y. Injection flow during steam condensation in silicon microchannels [J]. Journal of Micromechanics and Microengineering, 2007, 17(8): 1618-1627.
[4]	Wu H Y, Cheng P. Condensation flow patterns in silicon microchannels [J]. International Journal of Heat and Mass Transfer, 2005, 48(11): 2186-2197.
[5]	Wu J F, Shi M H, Chen Y P, Li X. Visualization study of steam condensation in wide rectangular silicon microchannels [J]. International Journal of Thermal Sciences, 2010, 49(6): 922-930.
[6]	Chen Y P, Wu R, Shi M H, Wu J F, Peterson G P. Visualization study of steam condensation in triangular microchannels [J]. Int. J. Heat Mass Transfer, 2009, 52(21): 5122-5129.
[7]	Ma X H, Fan X G, Lan Z, Hao T T. Flow patterns and transition characteristics for steam condensation in silicon microchannels [J]. Journal of Micromechanics and Microengineering, 2011, 21(7): 075009.
[8]	Fang C, Steinbrenner J E, Wang F M, Kenneth E G. Impact of wall hydrophobicity on condensation flow and heat transfer in silicon microchannels [J]. Journal of Micromechanics and Microengineering, 2010, 20(4): 045018.
[9]	Chen Y P, Shen C Q, Shi M H, Peterson G P. Visualization study of flow condensation in hydrophobic microchannels [J]. AIChE Journal, 2014, 60(3): 1182-1192.
[10]	Enright R, Miljkovic N, Alvarado J, Kwang K, Rose J. Dropwise condensation on micro-and nanostructured surfaces [J]. Nanoscale and Microscale Thermophysical Engineering, 2014, 18: 223-250.
[11]	Hu Shenhua(胡申华), Yan Junjie(严俊杰), Wang Jinshi(王进仕). Affecting factors of Marangoni condensation mode [J]. CIESC Journal(化工学报), 2011, 62(11): 3053-3059.
[12]	Utaka Y, Wang S. Characteristic curves and the promotion effect of ethanol addition on steam condensation heat transfer [J]. Int. J. Heat Mass Transfer, 2004, 47: 4507-4516.
[13]	Utaka Y, Kamiyama T. Condensate drop movement in Marangoni condensation by applying bulk temperature gradient on heat transfer surface [J]. Heat Transfer-Asian Research, 2008, 37(7): 387-397.
[14]	Utaka Y, Nishikawa T. Measurement of condensate film thickness for solutal Marangoni condensation applying laser extinction method [J]. Journal of Enhanced Heat Transfer, 2003, 10(2): 119-130.
[15]	Wang J S, Yan J J, Hu S H, Liu J P. Marangoni condensation heat transfer of water-ethanol mixtures on a vertical surface with temperature gradients [J]. Int. J. Heat Mass Transfer, 2009, 52(9): 2324-2334.
[16]	Yan J J, Wang J S, Yang Y S, Hu S H, Liu J P. Research on Marangoni condensation modes for water-ethanol mixture vapors [J]. Microgravity Science and Technology, 2009, 21(1): 77-85.
[17]	Deans J, Martin P J, Norris S. The condensation of steam containing low concentrations of trimethylamine [J]. International Journal of Heat and Mass Transfer, 2013, 61: 381-388.
[18]	Ma X H, Lan Z, Xu W, Wang M Z, Wang S F. Effect of surface free energy difference on steam-ethanol mixture condensation heat transfer [J]. Int. J. Heat Mass Transfer, 2012, 55: 531-537.
[19]	Lin P H, Fu B R, Pan C. Critical heat flux on flow boiling of methanol-water mixtures in a diverging microchannel with artificial cavities [J]. International Journal of Heat and Mass Transfer, 2011, 54(15): 3156-3166.
[20]	Fu B R, Tsou M S, Pan C. Boiling heat transfer and critical heat flux of ethanol-water mixtures flowing through a diverging microchannel with artificial cavities [J]. International Journal of Heat and Mass Transfer, 2012, 55(5/6): 1807-1814.
[21]	Fu B R, Lin P H, Tsou M S, et al. Flow pattern maps and transition criteria for flow boiling of binary mixtures in a diverging microchannel [J]. International Journal of Heat and Mass Transfer, 2012, 55(5): 1754-1763.
[22]	Poling B E, Prausnitz J M, John Paul O C, Reid R C. The Properties of Gases and Liquids [M]. New York: McGraw-Hill, 2001.