Electric field effect on wetting and capillary flow characteristics in vertical microgrooves

doi:10.11949/0438-1157.20220427

Abstract

Abstract:

Vertical microgroove capillary structures are widely used in heat transfer devices such as gravity heat pipes, evaporator and other heat transfer devices. The capillary rise in microgrooves attracts increasing attentions since it affects capillary limit significantly, which is easy to be reached due to the structure, gravity and other factors, and has a great influence on the heat transfer performance of the heat pipes. Thus, to improve the capillary limit of the vertical microgrooves, electric field, as one of the active enhanced technology, is introduced to the experiment system. The influence of the electric field on the wetting and capillary flow characteristics of the liquid in the vertical microgroove is studied experimentally and a mathematical model is established to understand the wetting and flow mechanisms of liquid in the vertical microgrooves under the action of electric field. The results show that the electric field can improve the wetting height of the liquid in the vertical microgrooves. When the electric field is 5.0 kV, the wetting height enhancement ratio can reach 30.0% compared with no electric field. Besides, the liquid wetting and capillary flow in the microgrooves under electric field are segmented: at the beginning of the capillary wetting flow, the square of the wetting height is linearly related to time, that is, h-t^1/2, and at the long-term of the wetting flow, the wetting height is linearly related to the 1/3 power of time, that is, h-t^1/3. Besides, the relationship between the wetting velocity and the wetting height first follows v-1/h, then is governed by v-1/h². Moreover, the wetting velocity decreases with time.

Key words: microchannels, flow, mathematical modeling, electric field, wetting height, wetting velocity

摘要：

竖直微槽群毛细结构广泛应用在重力热管、蒸发器等散热设备内，但受重力等因素影响易达到毛细极限。引入电场的主动强化方式来提高竖直微槽的毛细极限，并通过实验和建立数学模型研究电场对竖直微槽内液体润湿及毛细流动特性的影响。结果表明，电场可以提高竖直微槽内液体润湿高度，当电场为5.0 kV时与无电场时相比，润湿高度强化比可达到30.0%。同时，电场作用下流体在微槽道内的毛细润湿流动呈分段效应：润湿流动初期，润湿高度与时间的1/2次方呈线性关系，即h-t^1/2，润湿速率与润湿高度的倒数呈线性关系，即v-1/h；润湿流动中后期，润湿高度与时间的1/3次方呈线性关系，即h-t^1/3，润湿速率与润湿高度平方的倒数呈线性关系，即v-1/h²，且润湿速率随时间呈下降趋势。

关键词: 微通道, 流动, 数学模型, 电场, 润湿高度, 润湿速率

CLC Number:

TQ 021.1

Yifang DONG, Yingying YU, Xuegong HU, Gang PEI. Electric field effect on wetting and capillary flow characteristics in vertical microgrooves[J]. CIESC Journal, 2022, 73(7): 2952-2961.

董宜放, 于樱迎, 胡学功, 裴刚. 电场对竖直微槽润湿及毛细流动特性影响[J]. 化工学报, 2022, 73(7): 2952-2961.

Figures/Tables 13

Fig.1 Microgrooves testing unit

Fig.2 Cross section of microgrooves

Fig.3 Electric field arrangement

Table 1 Physical properties

变量	数值
液体密度 $ρ l$ /(kg/m³)	997
液体表面张力 $σ l$ /(N/m)	0.072
液体动力黏度 $μ l$ /(Pa·s)	8.9×10^-4
液体介电常数 $ε l$ /(C²/(N·m²))	78.4 $ε 0$
蒸汽介电常数 $ε v$ /(C²/(N·m²))	$ε 0$ ，8.854×10^-12
电导率 $σ e$ /(S/cm)	<1×10^-6

Table 1 Physical properties

变量	数值
液体密度 $ρ l$ /(kg/m³)	997
液体表面张力 $σ l$ /(N/m)	0.072
液体动力黏度 $μ l$ /(Pa·s)	8.9×10^-4
液体介电常数 $ε l$ /(C²/(N·m²))	78.4 $ε 0$
蒸汽介电常数 $ε v$ /(C²/(N·m²))	$ε 0$ ，8.854×10^-12
电导率 $σ e$ /(S/cm)	<1×10^-6

Fig.4 Image processing of the wetting height

Fig.5 Wetting height variation with time under 4.0 kV

Fig.6 Wetting height variation with time under different electric field

Fig.7 h2-t curve at the beginning of the capillary flow with or without electric field

Fig.8 Distribution of maximum wetting height along with x direction under different electric fields

Fig.9 Comparison of EHD enhanced ratio of maximum wetting height under different electric fields

Fig.10 Wetting velocity variation with time (a) and wetting height (b) under different electric fields

Fig.11 v-1/h curve for the beginning and long-term period under different electric fields

Fig.12 Comparison of EHD enhanced ratio of wetting velocity under different electric fields

References 44

1	Deng D X, Tang Y, Zeng J, et al. Characterization of capillary rise dynamics in parallel micro V-grooves[J]. International Journal of Heat and Mass Transfer, 2014, 77: 311-320.
2	Wang H, Pan Z H, Garimella S V. Numerical investigation of heat and mass transfer from an evaporating meniscus in a heated open groove[J]. International Journal of Heat and Mass Transfer, 2011, 54(13/14): 3015-3023.
3	Ghajar M, Darabi J. Evaporative heat transfer analysis of a micro loop heat pipe with rectangular grooves[J]. International Journal of Thermal Sciences, 2014, 79: 51-59.
4	胡学功, 颜晓虹, 赵耀华. 微槽群蒸发器在电子芯片冷却方面的应用[J]. 化工学报, 2005, 56(3): 412-416.
	Hu X G, Yan X H, Zhao Y H. Application of micro capillary groove evaporator to electronic chip cooling[J]. Journal of Chemical Industry and Engineering (China), 2005, 56(3): 412-416.
5	王涛, 胡学功, 唐大伟. 微通道-微槽群中间换热器特性实验研究[J]. 强激光与粒子束, 2007, 19(4): 581-584.
	Wang T, Hu X G, Tang D W. Experimental study on characteristics of an microchannels-microgrooves middle heat exchanger[J]. High Power Laser and Particle Beams, 2007, 19(4): 581-584.
6	Catton I, Stroes G R. A semi-analytical model to predict the capillary limit of heated inclined triangular capillary grooves[J]. Journal of Heat Transfer, 2002, 124(1): 162-168.
7	Suman B, De S, DasGupta S. A model of the capillary limit of a micro heat pipe and prediction of the dry-out length[J]. International Journal of Heat and Fluid Flow, 2005, 26(3): 495-505.
8	郭朝红, 胡学功, 唐大伟. 竖直矩形微槽轴向流动理论模型[J]. 工程热物理学报, 2010, 31(10): 1709-1712.
	Guo C H, Hu X G, Tang D W. An axial flow model for vertical rectangular microgrooves[J]. Journal of Engineering Thermophysics, 2010, 31(10): 1709-1712.
9	Nie X L, Hu X G, Tang D W. Modeling study on axial wetting length of meniscus in vertical rectangular microgrooves[J]. Applied Thermal Engineering, 2013, 52(2): 615-622.
10	Anand S, De S, Dasgupta S. Experimental and theoretical study of axial dryout point for evaporation from V-shaped microgrooves[J]. International Journal of Heat and Mass Transfer, 2002, 45(7): 1535-1543.
11	Rye R R, Yost F G, O'Toole E J. Capillary flow in irregular surface grooves[J]. Langmuir, 1998, 14(14): 3937-3943.
12	Ponomarenko A, Quéré D, Clanet C. A universal law for capillary rise in corners[J]. Journal of Fluid Mechanics, 2011, 666: 146-154.
13	Yu D, Hu X G, Guo C H, et al. Investigation on meniscus shape and flow characteristics in open rectangular microgrooves heat sinks with micro-PIV[J]. Applied Thermal Engineering, 2013, 61(2): 716-727.
14	Suman B, Hoda N. Effect of variations in thermophysical properties and design parameters on the performance of a V-shaped micro grooved heat pipe[J]. International Journal of Heat and Mass Transfer, 2005, 48(10): 2090-2101.
15	胡学功, 唐大伟. 竖直毛细微槽群热沉中蒸发液体的干涸特性[J]. 化工学报, 2007, 58(3): 575-580.
	Hu X G, Tang D W. Dryout characteristics of evaporating liquid in vertical capillary microgrooves heat sink[J]. Journal of Chemical Industry and Engineering (China), 2007, 58(3): 575-580.
16	胡学功, 白莉, 王照亮, 等. 竖直矩形毛细微槽群轴向干涸高度的理论分析[J]. 中国石油大学学报(自然科学版), 2007, 31(3): 119-123.
	Hu X G, Bai L, Wang Z L, et al. Theoretical analysis of axial dryout point height in vertical rectangular capillary microgrooves[J]. Journal of China University of Petroleum (Edition of Natural Science), 2007, 31(3): 119-123.
17	Chen Y P, Zhang C B, Shi M H, et al. Study on flow and heat transfer characteristics of heat pipe with axial “Ω”-shaped microgrooves[J]. International Journal of Heat and Mass Transfer, 2009, 52(3/4): 636-643.
18	Sheu T S, Ding P P, Lo I M, et al. Effect of surface characteristics on capillary flow in triangular microgrooves[J]. Experimental Thermal and Fluid Science, 2000, 22(1/2): 103-110.
19	Zhou W B, Hu X G, He Y, et al. Study on axial wetting length and evaporating heat transfer in rectangular microgrooves with superhydrophilic nano-textured surfaces for two-phase heat transfer devices[J]. Energy Conversion and Management, 2019, 200: 112098.
20	Saad I, Maalej S, Zaghdoudi M C. Numerical study of the electrohydrodynamic effects on the two-phase flow within an axially grooved flat miniature heat pipe[J]. International Journal of Heat and Mass Transfer, 2017, 107: 244-263.
21	Yu Z Q, Hallinani K, Bhagat W, et al. Electrohydrodynamically augmented micro heat pipes[J]. Journal of Thermophysics and Heat Transfer, 2002, 16(2): 180-186.
22	Lackowski M, Krupa A, Butrymowicz D. Dielectrophoresis flow control in microchannels[J]. Journal of Electrostatics, 2013, 71(5): 921-925.
23	常楚鑫, 徐黎婷, 殷嘉伦, 等. 浸没状态下的低压电润湿行为研究[J]. 化工学报, 2022, 73(4): 1673-1682.
	Chang C X, Xu L T, Yin J L, et al. Study on low voltage electrowetting behavior under immersion state[J]. CIESC Journal, 2022, 73(4): 1673-1682.
24	Basu M, Joshi V P, Das S, et al. Analysis of augmented droplet transport during electrowetting over triangular coplanar electrode array[J]. Journal of Electrostatics, 2021, 109: 103541.
25	谭杰, 陈贵军, 姜东岳. 基于介电润湿的可控液滴撞击数值研究[J]. 工程热物理学报, 2021, 42(11): 2869-2872.
	Tan J, Chen G J, Jiang D Y. Numerical study of controllable droplet impact based on electrowetting-on-dielectric[J]. Journal of Engineering Thermophysics, 2021, 42(11): 2869-2872.
26	刘镇, 许雄文, 刘金平, 等. 液滴在圆形电场中润湿性变化研究[J]. 化学工程, 2021, 49(12): 49-53.
	Liu Z, Xu X W, Liu J P, et al. Change of wettability of droplet in circular electric field[J]. Chemical Engineering (China), 2021, 49(12): 49-53.
27	陈晓杰, 苏宇. 不同润滑液的电润湿性能研究[J]. 润滑与密封, 2021, 46(2): 50-55, 64.
	Chen X J, Su Y. Electrowetting performance research of different lubricants[J]. Lubrication Engineering, 2021, 46(2): 50-55, 64.
28	Fan M Y, Zhou R, Jiang H W, et al. Effect of liquid conductivity on optical and electric performances of the electrowetting display system with a thick dielectric layer[J]. Results in Physics, 2020, 16: 102904.
29	Ahmad I, Pathak M, Khan M K. Electrowetting induced microdroplet oscillation over interdigitated electrodes for hotspot cooling applications[J]. Experimental Thermal and Fluid Science, 2021, 125: 110372.
30	Chakraborty M, Ghosh A, Dasgupta S. Enhanced microcooling by electrically induced droplet oscillation[J]. RSC Advances, 2014, 4: 1074-1082.
31	Wikramanayake E D, Bahadur V. Electrowetting-based enhancement of droplet growth dynamics and heat transfer during humid air condensation[J]. International Journal of Heat and Mass Transfer, 2019, 140: 260-268.
32	Izadi R, Merdasi A, Moosavi A. Heat transfer of power-law fluids under electrowetting actuation in structured microchannels[J]. International Communications in Heat and Mass Transfer, 2022, 130: 105803.
33	Suman B. A steady state model and maximum heat transport capacity of an electrohydrodynamically augmented micro-grooved heat pipe[J]. International Journal of Heat and Mass Transfer, 2006, 49(21/22): 3957-3967.
34	Saad I, Maalej S, Zaghdoudi M C. Modeling of the EHD effects on hydrodynamics and heat transfer within a flat miniature heat pipe including axial capillary grooves[J]. Journal of Electrostatics, 2017, 85: 61-78.
35	Chang F L, Hung Y M. Dielectric liquid pumping flow in optimally operated micro heat pipes[J]. International Journal of Heat and Mass Transfer, 2017, 108: 257-270.
36	郭磊, 刁彦华, 赵耀华, 等. 电场强化微槽道结构毛细芯蒸发器的传热特性[J]. 化工学报, 2014, 65(S1): 144-151.
	Guo L, Diao Y H, Zhao Y H, et al. Heat transfer characteristics of evaporator with rectangular microgrooves under electric field[J]. CIESC Journal, 2014, 65(S1): 144-151.
37	于樱迎, 唐瑾晨, 胡学功. 电场作用下矩形微槽群润湿特性数值分析[J]. 化工学报, 2018, 69(10): 4216-4223.
	Yu Y Y, Tang J C, Hu X G. Theoretical analysis of wetting characteristics in rectangular microgrooves under electric field[J]. CIESC Journal, 2018, 69(10): 4216-4223.
38	Yu Y Y, Hu X G, Tang J C, et al. Experimental study on EHD effects on wetting characteristics of liquid in open rectangular microgrooves[J]. Applied Thermal Engineering, 2019, 162: 114178.
39	于樱迎, 唐瑾晨, 胡学功. 电场对竖直矩形微槽群润湿及表面温度的影响[J]. 化工进展, 2020, 39(1): 26-33.
	Yu Y Y, Tang J C, Hu X G. Electric field effects on wettability and temperature distribution of open rectangular microgrooves[J]. Chemical Industry and Engineering Progress, 2020, 39(1): 26-33.
40	Fang X Z, Hu X G, Yu D, et al. Experimental study of the heat transfer characteristic in vertical rectangular capillary microgrooves heat sink under an electric field[C]//Proceedings of ASME 2013 11th International Conference on Nanochannels, Microchannels, and Minichannels. Sapporo, Japan, 2013.
41	Rye R R, Mann J A, Yost F G. The flow of liquids in surface grooves[J]. Langmuir, 1996, 12(2): 555-565.
42	Stratton J A. Electromagnetic Theory[M]. New York: McGraw-Hill Book Company, Inc., 1941.
43	Luo H, Gu G, Shang W, et al. The water droplet with huge charge density excited by triboelectric nanogenerator for water sterilization[J]. Nanotechnology, 2021, 32(41): 415404.
44	Gao M, Quan X J, Cheng P. An experimental investigation on EHD effects in the thin-film region of an evaporating meniscus[J]. International Communications in Heat and Mass Transfer, 2014, 56: 159-164.

[1]	Shaohua ZHOU, Feilong ZHAN, Guoliang DING, Hao ZHANG, Yanpo SHAO, Yantao LIU, Zheming GAO. Experimental study of flow noise in short tube throttle valve and noise reduction measures [J]. CIESC Journal, 2023, 74(S1): 113-121.
[2]	Yifei ZHANG, Fangchen LIU, Shuangxing ZHANG, Wenjing DU. Performance analysis of printed circuit heat exchanger for supercritical carbon dioxide [J]. CIESC Journal, 2023, 74(S1): 183-190.
[3]	He JIANG, Junfei YUAN, Lin WANG, Guyu XING. Experimental study on the effect of flow sharing cavity structure on phase change flow characteristics in microchannels [J]. CIESC Journal, 2023, 74(S1): 235-244.
[4]	Chao HU, Yuming DONG, Wei ZHANG, Hongling ZHANG, Peng ZHOU, Hongbin XU. Preparation of high-concentration positive electrolyte of vanadium redox flow battery by activating vanadium pentoxide with highly concentrated sulfuric acid [J]. CIESC Journal, 2023, 74(S1): 338-345.
[5]	Mingkun XIAO, Guang YANG, Yonghua HUANG, Jingyi WU. Numerical study on bubble dynamics of liquid oxygen at a submerged orifice [J]. CIESC Journal, 2023, 74(S1): 87-95.
[6]	Ruitao SONG, Pai WANG, Yunpeng WANG, Minxia LI, Chaobin DANG, Zhenguo CHEN, Huan TONG, Jiaqi ZHOU. Numerical simulation of flow boiling heat transfer in pipe arrays of carbon dioxide direct evaporation ice field [J]. CIESC Journal, 2023, 74(S1): 96-103.
[7]	Kaijie WEN, Li GUO, Zhaojie XIA, Jianhua CHEN. A rapid simulation method of gas-solid flow by coupling CFD and deep learning [J]. CIESC Journal, 2023, 74(9): 3775-3785.
[8]	Yubing WANG, Jie LI, Hongbo ZHAN, Guangya ZHU, Dalin ZHANG. Experimental study on flow boiling heat transfer of R134a in mini channel with diamond pin fin array [J]. CIESC Journal, 2023, 74(9): 3797-3806.
[9]	Jiaqi YUAN, Zheng LIU, Rui HUANG, Lefu ZHANG, Denghui HE. Investigation on energy conversion characteristics of vortex pump under bubble inflow [J]. CIESC Journal, 2023, 74(9): 3807-3820.
[10]	Yaxin ZHAO, Xueqin ZHANG, Rongzhu WANG, Guo SUN, Shanjing YAO, Dongqiang LIN. Removal of monoclonal antibody aggregates with ion exchange chromatography by flow-through mode [J]. CIESC Journal, 2023, 74(9): 3879-3887.
[11]	Song HE, Qiaomai LIU, Guangshuo XIE, Simin WANG, Juan XIAO. Two-phase flow simulation and surrogate-assisted optimization of gas film drag reduction in high-concentration coal-water slurry pipeline [J]. CIESC Journal, 2023, 74(9): 3766-3774.
[12]	Lei XING, Chunyu MIAO, Minghu JIANG, Lixin ZHAO, Xinya LI. Optimal design and performance analysis of downhole micro gas-liquid hydrocyclone [J]. CIESC Journal, 2023, 74(8): 3394-3406.
[13]	Yan GAO, Peng WU, Chao SHANG, Zejun HU, Xiaodong CHEN. Preparation of magnetic agarose microspheres based on a two-fluid nozzle and their protein adsorption properties [J]. CIESC Journal, 2023, 74(8): 3457-3471.
[14]	Yue YANG, Dan ZHANG, Jugan ZHENG, Maoping TU, Qingzhong YANG. Experimental study on flash and mixing evaporation of aqueous NaCl solution [J]. CIESC Journal, 2023, 74(8): 3279-3291.
[15]	Guoze CHEN, Dong WEI, Qian GUO, Zhiping XIANG. Optimal power point optimization method for aluminum-air batteries under load tracking condition [J]. CIESC Journal, 2023, 74(8): 3533-3542.