Sierpinski亲/疏水分形图案表面气泡分布及强化换热研究
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摘要
针对芯片散热表面热流具有典型的中心高四周低的非均匀分布特征,设计制备了具有三阶Sierpinski地毯曲线分形特点的亲疏水交错润湿铜表面,并通过实验观测了气泡在典型的亲/疏水分形表面的动力学特性。结果表明,气泡会首先在预设的高阶疏水点处成核、生长,并呈现典型的分形特征,实现了初始气泡成核位置的可控分布;之后,相互邻近的疏水点上的气泡开始克服能垒而发生合并,同时伴随着高阶疏水区域的气泡向中央低阶区域的定向移动、合并过程,最终在中心一阶疏水区域形成大气泡。相比于光滑及疏水点阵表面,Sierpinski亲/疏水交错润湿表面不仅能够有效降低液体起始沸腾温度,提高沸腾换热的临界热流密度,而且可以规划气泡的成核点及移动、合并方向,进而实现气泡空间分布与加热壁面热流密度分布的协同一致。因此,具有Sierpinski分形特性的亲/疏水交错润湿表面进一步提高了沸腾换热性能。
The heat dissipation of chip, which releases much more heat from its center than from the marginal area, shows a typical non-uniform distribution feature. Based on this, a non-uniform wetting copper surface with fractal features of three-order Sierpinski carpet was designed, and then the dynamic behaviors of the bubble on the surface with typical hydrophobic/hydrophilic fractal pattern were observed experimentally. The results showed that small bubbles would first nucleate and grow at the preset high-order hydrophobic points, and their distribution presented typical fractal feature, which indicates that the controllable distribution of the initial bubble nucleation sites is achieved. Subsequently, the neighboring bubbles at the hydrophobic points began to merge with each other after overcoming the energy barrier. Directional migration of small bubbles from the high-order hydrophobic region to central low-order region could also be observed simultaneously. A large bubble was finally formed in the central first-order hydrophobic region after bubbles coalescence. Compared with smooth and hydrophobic point array surfaces, the fractal non-uniform wetting surface can reduce the onset boiling temperature effectively, and increase the critical heat flux density of boiling heat transfer. More importantly, the nucleation sites of the bubbles and their moving and merging processes on the fractal pattern surface can be designed and planned in advance, so the distribution of the bubbles can keep consistent with the heat flux on heating surface. Therefore, this non-uniform wetting surface with Sierpinski fractal pattern can further improve the boiling heat transfer performance.
The heat dissipation of chip, which releases much more heat from its center than from the marginal area, shows a typical non-uniform distribution feature. Based on this, a non-uniform wetting copper surface with fractal features of three-order Sierpinski carpet was designed, and then the dynamic behaviors of the bubble on the surface with typical hydrophobic/hydrophilic fractal pattern were observed experimentally. The results showed that small bubbles would first nucleate and grow at the preset high-order hydrophobic points, and their distribution presented typical fractal feature, which indicates that the controllable distribution of the initial bubble nucleation sites is achieved. Subsequently, the neighboring bubbles at the hydrophobic points began to merge with each other after overcoming the energy barrier. Directional migration of small bubbles from the high-order hydrophobic region to central low-order region could also be observed simultaneously. A large bubble was finally formed in the central first-order hydrophobic region after bubbles coalescence. Compared with smooth and hydrophobic point array surfaces, the fractal non-uniform wetting surface can reduce the onset boiling temperature effectively, and increase the critical heat flux density of boiling heat transfer. More importantly, the nucleation sites of the bubbles and their moving and merging processes on the fractal pattern surface can be designed and planned in advance, so the distribution of the bubbles can keep consistent with the heat flux on heating surface. Therefore, this non-uniform wetting surface with Sierpinski fractal pattern can further improve the boiling heat transfer performance.
引文
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[10]HAI T P,CANEY N,MARTY P,et al.Surface wettability control by nanocoating:the effects on pool boiling heat transfer and nucleation mechanism[J].International Journal of Heat&Mass Transfer,2009,52(23):5459-5471.
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[12]SUROTO B J.Effects of hydrophobic-spot periphery and subcooling on nucleate pool boiling from a mixedwettability surface[J].Journal of Thermal Science and Technology,2013,8(1):294-308.
[13]JO H J,KIM S H,PARK H S,et al.Critical heat flux and nucleate boiling on several heterogeneous wetting surfaces:controlled hydrophobic patterns on a hydrophilic substrate[J].International Journal of Multiphase Flow,2014,62(2):101-109.
[14]JO H J,AHN H S,KANG S H,et al.A study of nucleate boiling heat transfer on hydrophilic,hydrophobic and heterogeneous wetting surfaces[J].International Journal of Heat&Mass Transfer,2011,54(25):5643-5652.
[15]MORI S,UTAKA Y.Critical heat flux enhancement by surface modification in a saturated pool boiling:a review[J].International Journal of Heat&Mass Transfer,2017,108:2534-2557.
[16]LEE J S.Critical heat flux enhancement of pool boiling with adaptive fraction control of patterned wettability[J].International Journal of Heat&Mass Transfer,2016,96:504-512.
[17]JO H J,PARK H S,KIM M H.Single bubble dynamics on hydrophobic-hydrophilic mixed surfaces[J].International Journal of Heat&Mass Transfer,2016,93:554-565.
[18]SUBRAMANIAN R S,NADJOUA M A,MCLAUGHLIN J B.Motion of a drop on a solid surface due to a wettability gradient[J].Langmuir,2005,21(25):1184.
[19]SATEESH G,DAS S K,BALAKRISHNAN A R.Analysis of pool boiling heat transfer:effect of bubbles sliding on the heating surface[J].International Journal of Heat&Mass Transfer,2005,48(8):1543-1553.
[20]HSU C C,CHEN P H.Surface wettability effects on critical heat flux of boiling heat transfer using nanoparticle coatings[J].International Journal of Heat&Mass Transfer,2012,55(13/14):3713-3719.
[21]BETZ A R,JENKINS J,KIM C J,et al.Boiling heat transfer on superhydrophilic,superhydrophobic,and superbiphilic surfaces[J].International Journal of Heat&Mass Transfer,2012,57(2):733-741.
[2]魏进家,张永海.柱状微结构表面强化沸腾换热研究综述[J].化工学报,2016,67(1):97-108.WEI Jinjia,ZHANG Yonghai.Review of research on surface-enhanced boiling heat transfer of columnar microstructures[J].Journal of Chemical Industry and Engineering,2016,67(1):97-108.
[3]KONG X,ZHANG Y,WEI J,et al.Experimental study of pool boiling heat transfer on novel bistructured surfaces based on micro-pin-finned structure[J].Experimental Thermal and Fluid Science,2018,91:9-19.
[4]高明,郑平,全晓军.电场作用下单个沸腾气泡动态特性研究[J].工程热物理学报,2014,35(7):1387-1390.GAO Ming,ZHENG Ping,QUAN Xiaojun.Study on dynamic characteristics of single boiling bubbles under electric field[J].Journal of Engineering Thermophysics,2014,35(7):1387-1390.
[5]AHN H S,KIM M H.A review on critical heat flux enhancement with nanofluids and surface modification[J].Journal of Heat Transfer,2012,134(2):155-172.
[6]DONG E K,DONG I Y,DONG W J,et al.Review of boiling heat transfer enhancement on micro/nano structured surfaces[J].Experimental Thermal&Fluid Science,2015,66:173-196.
[7]郑晓欢,纪献兵.超亲/疏水性表面池沸腾传热研究[J].化工进展,2016,35(12):3793-3798.ZHENG Xiaohuan,JI Xianbing.Super-/hydrophobic surface pool boiling heat transfer research[J].Chemical Progress,2016,35(12):3793-3798.
[8]徐鹏飞,李强,宣益民.超亲水多孔表面制备及其池沸腾换热研究[J].工程热物理学报,2014,35(8):1606-1609.XU Pengfei,LI Qiang,XUAN Yimin.Preparation of super-hydrophilic porous surface and its pool boiling heat transfer[J].Journal of Engineering Thermophysics,2014,35(8):1606-1609.
[9]KIM S J,BANG I C,BUONGIORNO J,et al.Surface wettability change during pool boiling of nanofluids and its effect on critical heat flux[J].International Journal of Heat&Mass Transfer,2007,50(19):4105-4116.
[10]HAI T P,CANEY N,MARTY P,et al.Surface wettability control by nanocoating:the effects on pool boiling heat transfer and nucleation mechanism[J].International Journal of Heat&Mass Transfer,2009,52(23):5459-5471.
[11]BETZ A R,XU J,QIU H,et al.Do surfaces with mixed hydrophilic and hydrophobic areas enhance pool boiling?[J].Applied Physics Letters,2010,97(14):103115.
[12]SUROTO B J.Effects of hydrophobic-spot periphery and subcooling on nucleate pool boiling from a mixedwettability surface[J].Journal of Thermal Science and Technology,2013,8(1):294-308.
[13]JO H J,KIM S H,PARK H S,et al.Critical heat flux and nucleate boiling on several heterogeneous wetting surfaces:controlled hydrophobic patterns on a hydrophilic substrate[J].International Journal of Multiphase Flow,2014,62(2):101-109.
[14]JO H J,AHN H S,KANG S H,et al.A study of nucleate boiling heat transfer on hydrophilic,hydrophobic and heterogeneous wetting surfaces[J].International Journal of Heat&Mass Transfer,2011,54(25):5643-5652.
[15]MORI S,UTAKA Y.Critical heat flux enhancement by surface modification in a saturated pool boiling:a review[J].International Journal of Heat&Mass Transfer,2017,108:2534-2557.
[16]LEE J S.Critical heat flux enhancement of pool boiling with adaptive fraction control of patterned wettability[J].International Journal of Heat&Mass Transfer,2016,96:504-512.
[17]JO H J,PARK H S,KIM M H.Single bubble dynamics on hydrophobic-hydrophilic mixed surfaces[J].International Journal of Heat&Mass Transfer,2016,93:554-565.
[18]SUBRAMANIAN R S,NADJOUA M A,MCLAUGHLIN J B.Motion of a drop on a solid surface due to a wettability gradient[J].Langmuir,2005,21(25):1184.
[19]SATEESH G,DAS S K,BALAKRISHNAN A R.Analysis of pool boiling heat transfer:effect of bubbles sliding on the heating surface[J].International Journal of Heat&Mass Transfer,2005,48(8):1543-1553.
[20]HSU C C,CHEN P H.Surface wettability effects on critical heat flux of boiling heat transfer using nanoparticle coatings[J].International Journal of Heat&Mass Transfer,2012,55(13/14):3713-3719.
[21]BETZ A R,JENKINS J,KIM C J,et al.Boiling heat transfer on superhydrophilic,superhydrophobic,and superbiphilic surfaces[J].International Journal of Heat&Mass Transfer,2012,57(2):733-741.