混合蒸气冷凝过程中均匀温度面上液滴自发移动现象及特性
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摘要
在某些混合蒸气的冷凝过程中,传热面温度梯度导致冷凝液浓度及表面张力不平衡,从而驱动冷凝液滴产生自发移动现象。此现象产生的前提为传热面具有整体温度分布,即传热面从一侧表面的相对低温状态,随着表面位置变化逐渐过渡到另一侧的相对高温状态,而本论文在水-酒精混合蒸气的冷凝过程中,观测到在均匀温度传热面上也会发生冷凝液滴自发移动现象。通过对具有和不具有初速度的冷凝液滴在均匀传热面上的不同移动特性进行比较分析,确认了具有明显初速度的冷凝液滴在均匀温度领域产生自发移动现象,而无初速度液滴则产生无序运动(非自发移动)。从而验证了在均匀温度传热面,冷凝液滴自发移动的驱动力为液滴移动同时其周围形成的局部温度分布和局部表面张力不平衡的推测。
During the condensation of certain mixed vapors, the temperature gradient of the heat transfer surface causes an imbalance in the concentration of the condensate and the surface tension, thereby driving the condensed droplets to spontaneously move. The necessary condition for this kind of phenomenon is the evident bulk temperature gradient on the heat transfer surface. However, in this study, the spontaneous movement of condensate drop was initially observed on the heat transfer surface with uniform temperature distribution, during the condensation of water-ethanol binary vapor mixture. The comparison and analyzation were performed on the characteristics of drop movement between the condensate drops with and without evident initial velocity on uniform temperature surface. It was confirmed that the spontaneous movement occurred when the condensate drops have evident initial velocity, while the random movement occurred when the drops didn spontaneous movement). Finally, it was verified the inference that the driven force for the spontaneous movement of condensate drops on uniform temperature surface was, the local temperature distribution and the resulting local imbalance of surface tension around the drops.
During the condensation of certain mixed vapors, the temperature gradient of the heat transfer surface causes an imbalance in the concentration of the condensate and the surface tension, thereby driving the condensed droplets to spontaneously move. The necessary condition for this kind of phenomenon is the evident bulk temperature gradient on the heat transfer surface. However, in this study, the spontaneous movement of condensate drop was initially observed on the heat transfer surface with uniform temperature distribution, during the condensation of water-ethanol binary vapor mixture. The comparison and analyzation were performed on the characteristics of drop movement between the condensate drops with and without evident initial velocity on uniform temperature surface. It was confirmed that the spontaneous movement occurred when the condensate drops have evident initial velocity, while the random movement occurred when the drops didn spontaneous movement). Finally, it was verified the inference that the driven force for the spontaneous movement of condensate drops on uniform temperature surface was, the local temperature distribution and the resulting local imbalance of surface tension around the drops.
引文
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[15] Wang S X, Utaka Y. An experimental study on the effect of noncondensable gas for solutal Marangoni condensation heat transfer[J]. Experimental Heat Transfer, 2005, 18(2):61-79.
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[17] Li Y, Wang J S, Xia K, et al. Experimental study on time-series characteristics in Marangoni condensation for ethanol-water mixtures on a horizontal surface[J]. Experimental Thermal and Fluid Science, 2017, 83:141-156.
[18]陈娜娜,王进仕,李勇,等.水平表面水-酒精混合蒸气Marangoni瞬态凝结过程的凝结液形态[J].化工学报, 2016, 67(9):3574-3582.Chen N N, Wang J S, Li Y, et al. Characteristics of Marangoni dynamic condensation modes for water-ethanol mixture vapors on horizontal surface[J]. CIESC Journal, 2016, 67(9):3574-3582.
[19] Jiang R, Ma X H, Lan Z, et al. Visualization study of condensation of ethanol-water mixture in trapezoidal microchannels[J].International Journal of Heat and Mass Transfer, 2015, 90:339-349.
[20]姜睿,马学虎,兰忠,等.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.Jiang R, Ma X H, Lan Z, et al. Visualization study of flow patterns for ethanol-water mixtures condensation in microchannels[J].CIESC Journal, 2015, 66(11):4320-4326.
[21] Wang J S, Yan J J, Li Y. Correlation for Marangoni condensation heat transfer of water-ethanol mixture vapors[J]. Heat Transfer Engineering, 2015, 37(9):774-782.
[22] Chaudhury M K, Whitesides G M. How to make water run uphill[J]. Science, New Series, 1992, 256:1539-1541.
[23] Daniel S, Chaudhury M K, Chen J C. Fast drop movements resulting from the phase change on a gradient surface[J]. Science,2001, 291:633-636.
[24] Nagai K, Sumino Y, Yoshikawa K. Regular self-motion of a liquid droplet powered by the chemical Marangoni effect[J]. Colloids and Surfaces B:Biointerfaces, 2007, 56:197-200.
[25] Gao P, Yin Z, Hu W. Thermocapillary motion of droplets at large Marangoni numbers[J]. Advances in Space Research, 2008, 41:2101-2106.
[26]钟源,杜海存,张莹.单向温度梯度下异质液滴的热毛细迁移[J].过程工程报, 2018, 18(4):697-703.Zhong Y, Du H C, Zhang Y. Thermocapillary migration of heterogeneous droplets with unidirectional temperature gradient[J]. The Chinese Journal of Process Engineering, 2018, 18(4):697-703.
[27]孙涛,姜存华,沈达鹏.水平固体表面温度梯度下硅油液滴运动[J].微纳电子技术, 2017, 54(7):485-491.Sun T, Jiang C H, Shen D P. A silicone oil droplet motion under temperature gradient on horizontal solid surface[J].Micronanoelectronic Technology, 2017, 54(7):485-491.
[28] Savino R, Cecere A, Paola R D. Surface tension-driven flow in wickless heat pipes with self-rewetting fluids[J]. International Journal of Heat and Fluid Flow, 2009, 30:380-388.
[29]鲍允州,张莹.不同壁温驱动液滴Marangoni迁移的直接数值模拟[J].南昌大学学报, 2018, 40(2):163-169.Bao Y Z, Zhang Y. Direct numerical simulation of Marangoni migration of a droplet driven by different wall temperature[J].Journal of Nanchang University(Engineering&Technology),2018, 40(2):163-169.
[30] Utaka Y, Kamiyama T. Condensate drop movement in Marangoni condensation by applying bulk temperature gradient on heat transfer surface[J]. Heat Transfer-Asian Res., 2008, 37(7):387-397.
[31] Chen Z H, Utaka Y. Characteristics of condensate drop movement with application of bulk surface temperature gradient in Marangoni dropwise condensation[J]. International Journal of Heat and Mass Transfer, 2011, 54:5049-5059.
[2] Ford J D, Missen R W. On the conditions for stability of falling films subject to surface tension disturbances:the condensation of binary vapor[J]. Can. J. Chem. Eng., 1968, 48:309-312.
[3] Morrison J N A, Deans J. Augmentation of steam condensation heat transfer by addition of ammonia[J]. Int. J. Heat Mass Transfer, 1997, 40:765-772.
[4] Utaka Y, Kobayashi H. Effect of vapor velocity on condensation heat transfer for water-ethanol binary vapor mixture[C]//6th ASME-JSME Thermal Engineering Conference. 2003.
[5] Murase T, Wang H S, Rose J W. Marangoni condensation of steam-ethanol mixtures on a horizontal tube[J]. Int. J. Heat Mass Transfer, 2007, 50:3774-3779.
[6] Hu S H, Yan J J, Wang J S, et al. Effect of temperature gradient on Marangoni condensation heat transfer for ethanol-water mixtures[J]. International Journal of Multiphase Flow, 2007, 33:935-947.
[7] Wang J S, Yan J J, Hu S H, et al. Marangoni condensation heat transfer of water-ethanol mixtures on a vertical surface with temperature gradients[J]. International Journal of Heat and Mass Transfer, 2009, 52:2324-2334.
[8] Fujii T, Osa N, Koyama S. Free convective condensation of binary vapor mixtures on a smooth horizontal tube:condensing mode and heat transfer coefficient of condensate[C]//Proc. US Engineering Foundation Conference on Condensation and Condenser Design.St. Augustine, Florida:ASME, 1993:171-182.
[9] Utaka Y, Terachi N. Measurement of condensation characteristic curves for binary mixture of steam and ethanol vapor[J]. Heat Transfer-Japanese Res., 1995, 24:57-67.
[10] Utaka Y, Terachi N. Study on condensation heat transfer for steam ethanol vapor mixture(relation between condensation characteristic curve and modes of condensate)[J]. Trans. Jpn. Soc.Mech. Eng. Ser. B, 1995, 61(588):3059-3065.
[11] Hijikata K, Fukasuku Y, Nakabeppu O. Theoretical and experimental studies on pseudo-dropwise condensation of a binary vapor mixture[J]. Transactions of ASME, 1996, 118:140-147.
[12] Utaka Y, Kenmotsu T, Yokoyama S. A study on Marangoni condensation(measurement and observation for water and ethanol vapor mixture)[C]//Proc. 11th Int Heat Transfer Conf. 1998:397-402.
[13] Kim K J, Lefsaker A M, Razani A, et al. The effective use of heat transfer additives for steam condensation[J]. Applied Thermal Engineering, 2001, 21:1863-1874.
[14] Utaka Y, Wang S X. Characteristic curves and the promotion effect of ethanol addition on steam condensation heat transfer[J].Int. J. Heat Mass Transfer, 2004, 47:4507-4516.
[15] Wang S X, Utaka Y. An experimental study on the effect of noncondensable gas for solutal Marangoni condensation heat transfer[J]. Experimental Heat Transfer, 2005, 18(2):61-79.
[16]严俊杰,王进仕,胡申华,等.存在温度梯度的竖直壁面Marangoni凝结换热特性研究[J].西安交通大学学报, 2008, 42(1):46-52.Yan J J, Wang J S, Hu S H, et al. Marangoni condensation heat tgrraandsifeenrt s[cJ]h.a rJaocutrenriaslt icofsXoinanve rJtiiacoatlo nsgu rUfancivee rswiittyh,2t0e0m8p,e r4a2t(u1r)e:46-52.
[17] Li Y, Wang J S, Xia K, et al. Experimental study on time-series characteristics in Marangoni condensation for ethanol-water mixtures on a horizontal surface[J]. Experimental Thermal and Fluid Science, 2017, 83:141-156.
[18]陈娜娜,王进仕,李勇,等.水平表面水-酒精混合蒸气Marangoni瞬态凝结过程的凝结液形态[J].化工学报, 2016, 67(9):3574-3582.Chen N N, Wang J S, Li Y, et al. Characteristics of Marangoni dynamic condensation modes for water-ethanol mixture vapors on horizontal surface[J]. CIESC Journal, 2016, 67(9):3574-3582.
[19] Jiang R, Ma X H, Lan Z, et al. Visualization study of condensation of ethanol-water mixture in trapezoidal microchannels[J].International Journal of Heat and Mass Transfer, 2015, 90:339-349.
[20]姜睿,马学虎,兰忠,等.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.Jiang R, Ma X H, Lan Z, et al. Visualization study of flow patterns for ethanol-water mixtures condensation in microchannels[J].CIESC Journal, 2015, 66(11):4320-4326.
[21] Wang J S, Yan J J, Li Y. Correlation for Marangoni condensation heat transfer of water-ethanol mixture vapors[J]. Heat Transfer Engineering, 2015, 37(9):774-782.
[22] Chaudhury M K, Whitesides G M. How to make water run uphill[J]. Science, New Series, 1992, 256:1539-1541.
[23] Daniel S, Chaudhury M K, Chen J C. Fast drop movements resulting from the phase change on a gradient surface[J]. Science,2001, 291:633-636.
[24] Nagai K, Sumino Y, Yoshikawa K. Regular self-motion of a liquid droplet powered by the chemical Marangoni effect[J]. Colloids and Surfaces B:Biointerfaces, 2007, 56:197-200.
[25] Gao P, Yin Z, Hu W. Thermocapillary motion of droplets at large Marangoni numbers[J]. Advances in Space Research, 2008, 41:2101-2106.
[26]钟源,杜海存,张莹.单向温度梯度下异质液滴的热毛细迁移[J].过程工程报, 2018, 18(4):697-703.Zhong Y, Du H C, Zhang Y. Thermocapillary migration of heterogeneous droplets with unidirectional temperature gradient[J]. The Chinese Journal of Process Engineering, 2018, 18(4):697-703.
[27]孙涛,姜存华,沈达鹏.水平固体表面温度梯度下硅油液滴运动[J].微纳电子技术, 2017, 54(7):485-491.Sun T, Jiang C H, Shen D P. A silicone oil droplet motion under temperature gradient on horizontal solid surface[J].Micronanoelectronic Technology, 2017, 54(7):485-491.
[28] Savino R, Cecere A, Paola R D. Surface tension-driven flow in wickless heat pipes with self-rewetting fluids[J]. International Journal of Heat and Fluid Flow, 2009, 30:380-388.
[29]鲍允州,张莹.不同壁温驱动液滴Marangoni迁移的直接数值模拟[J].南昌大学学报, 2018, 40(2):163-169.Bao Y Z, Zhang Y. Direct numerical simulation of Marangoni migration of a droplet driven by different wall temperature[J].Journal of Nanchang University(Engineering&Technology),2018, 40(2):163-169.
[30] Utaka Y, Kamiyama T. Condensate drop movement in Marangoni condensation by applying bulk temperature gradient on heat transfer surface[J]. Heat Transfer-Asian Res., 2008, 37(7):387-397.
[31] Chen Z H, Utaka Y. Characteristics of condensate drop movement with application of bulk surface temperature gradient in Marangoni dropwise condensation[J]. International Journal of Heat and Mass Transfer, 2011, 54:5049-5059.