设计搭建了可以对气流速度精确控制下的液滴进行实时光学观测的闭环风管，利用风管给液滴施加剪切流，通过顶视和侧视高速CCD相机采集液滴的形貌信息，实验研究10~30 μL的液滴在受0~10 m/s风速下的蒸发动力学特性与传质规律。研究发现，剪切流作用下的液滴蒸发经历3个阶段，且气流能显著提升液滴蒸发速率。对10 μL的小液滴，在2 m/s风速下，其蒸发速率相比于无风情况下提高168%，但在高风速下，增大风速不能显著提升液滴的蒸发速率。气流对液滴形貌的影响主要与Weber数、表征风力和黏附力之比的无量纲数k'相关，液滴体积越大，其形貌受风速影响越显著，通过动力学分析定量化推导了前后接触角差值与风速的关系。研究了剪切流对于气液界面传质的影响，得到无量纲Reynolds数与Sherwood数的关系，推导了风速与蒸发速率的理论关系式，与实验结果一致性较好。
李子龙
,
秦军
,
陶跃群
,
何乃峰
,
刘秋生
,
朱志强
. 剪切流作用下附壁钉扎液滴的蒸发动力学研究[J]. 中国科学院大学学报, 2025
, 42(3)
: 403
-411
.
DOI: 10.7523/j.ucas.2023.053
A closed loop wind tunnel that allows for high-quality optical observation was designed. Droplets were subjected to shear flow in the wind tunnel and the CCD cameras mounted horizontally and vertically were used to acquire the shape information to experimentally investigate the droplet evaporation. It is found that the droplet will experience three stages under the shear flow and airflow could enhance the evaporation rate significantly. For the droplet of 10 μL, the evaporation rate is 168% higher in 2 m/s wind speed than that without wind. However, increasing the wind speed can not improve the evaporation rate when the wind speed is high. The effect of airflow on the shape of droplet is mainly dependent on the Weber number and the dimensionless number k', which characterizes the ratio of wind force and adhesion force. The effect of shear flow on mass transfer at the gas-liquid interface was investigated, and the relationship between the dimensionless Reynolds number and the Sherwood numbers was determined. It was determined that the theoretical relationship between wind speed and evaporation rate is consistent with experimental data.
[1] Kandlikar S G, Steinke M E. Contact angles and interface behavior during rapid evaporation of liquid on a heated surface[J]. International Journal of Heat and Mass Transfer, 2002, 45(18): 3771-3780. DOI:10.1016/S0017-9310(02)00090-X.
[2] Preston D J, Mafra D L, Miljkovic N, et al. Scalable graphene coatings for enhanced condensation heat transfer[J].Nano Letters, 2015, 15(5): 2902-2909. DOI:10.1021/nl504628s.
[3] Singh M, Haverinen H M, Dhagat P, et al. Inkjet printing-process and its applications[J]. Advanced Materials, 2010, 22(6): 673-685. DOI:10.1002/adma.200901141.
[4] Lim T, Han S, Chung J, et al. Experimental study on spreading and evaporation of inkjet printed pico-liter droplet on a heated substrate[J]. International Journal of Heat and Mass Transfer, 2009,52(1/2):431-441. DOI:10.1016/j.ijheatmasstransfer.2008.05.028.
[5] Sartre V, Zaghdoudi M C, Lallemand M. Effect of interfacial phenomena on evaporative heat transfer in micro heat pipes[J]. International Journal of Thermal Sciences, 2000, 39(4): 498-504. DOI:10.1016/S1290-0729(00)00205-2.
[6] Langmuir I. The evaporation of small spheres[J]. Physical Review, 1918, 12(5): 368-370. DOI:10.1103/PhysRev.12.368.
[7] Cachile M, Bénichou O, Cazabat A M. Evaporating droplets of completely wetting liquids[J]. Langmuir, 2002, 18(21): 7985-7990. DOI:10.1021/la020231e.
[8] Hu H, Larson R G. Evaporation of a sessile droplet on a substrate[J]. The Journal of Physical Chemistry B, 2002, 106(6): 1334-1344. DOI:10.1021/jp0118322.
[9] Popescu M N, Oshanin G, Dietrich S, et al. Precursor films in wetting phenomena[J]. Journal of Physics: Condensed Matter, 2012, 24(24): 243102. DOI:10.1088/0953-8984/24/24/243102.
[10] Stauber J M, Wilson S K, Duffy B R, et al. Evaporation of droplets on strongly hydrophobic substrates[J]. Langmuir: the ACS Journal of Surfaces and Colloids, 2015, 31(12): 3653-3660. DOI:10.1021/acs.langmuir.5b00286.
[11] Picknett R G, Bexon R. The evaporation of sessile or pendant drops in still air[J]. Journal of Colloid and Interface Science, 1977, 61(2): 336-350. DOI:10.1016/0021-9797(77)90396-4.
[12] Bourges-Monnier C, Shanahan M E R. Influence of evaporation on contact angle[J]. Langmuir, 1995, 11(7): 2820-2829. DOI:10.1021/la00007a076.
[13] Wilson S K, D’Ambrosio H M. Evaporation of sessile droplets[J]. Annual Review of Fluid Mechanics, 2023, 55: 481-509. DOI: 10.1146/annurev-fluid-031822-013213.
[14] Khandekar S, Muralidhar K. Dropwise condensation on inclined textured surfaces[M/OL]. New York, NY: Springer New York, 2014.(2013-09-06)[2023-02-08]. https://link.springer.com/10.1007/978-1-4614-8447-9. DOI:10.1007/978-1-4614-8447-9.
[15] 任东伟, 阳倦成, 倪明玖. 水平磁场作用下金属液滴撞击电解质液池表面的实验研究[J]. 中国科学院大学学报, 2021, 38(4): 442-449. DOI: 10.7523/j.issn.2095-6134.2021.04.002.
[16] 董泉润, 阳倦成, 倪明玖. 水平磁场作用下液态金属自由射流破碎特性的实验研究[J]. 中国科学院大学学报, 2022, 39(5): 577-585. DOI: 10.7523/j.ucas.2022.029.
[17] Bin L, Bennacer R, Bouvet A. Evaporation of methanol droplet on the Teflon surface under different air velocities[J]. Applied Thermal Engineering, 2011, 31(17-18): 3792-3798. DOI:10.1016/j.applthermaleng.2011.07.018.
[18] Buffone C. Evaporating sessile drops subject to crosswind[J]. International Journal of Thermal Sciences, 2019, 144: 1-10. DOI:10.1016/j.ijthermalsci.2019.05.018.
[19] Doursat C, Lecoq L, Laguerre O, et al. Droplet evaporation on a solid surface exposed to forced convection: experiments, simulation and dimensional analysis[J]. International Journal of Heat and Mass Transfer, 2017, 113: 1234-1245. DOI:10.1016/j.ijheatmasstransfer.2017.05.110.
[20] Milne A J B, Amirfazli A. Drop shedding by shear flow for hydrophilic to superhydrophobic surfaces[J]. Langmuir, 2009, 25(24): 14155-14164. DOI:10.1021/la901737y.
[21] Madani S, Amirfazli A. Oil drop shedding from solid substrates by a shearing liquid[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014, 441: 796-806. DOI:10.1016/j.colsurfa.2013.04.058.
[22] White E B, Schmucker J A. A runback criterion for water drops in a turbulent accelerated boundary layer[J]. Journal of Fluids Engineering, 2008, 130(6): 1. DOI: 10.1115/1.2917429.
[23] Parekh S, Farid M M, Selman J R, et al. Solar desalination with a humidification-dehumidification technique： a comprehensive technical review[J]. Desalination, 2004, 160(2): 167-186. DOI:10.1016/S0011-9164(04)90007-0.
[24] Ahlers M, Buck-Emden A, Bart H J. Is dropwise condensation feasible? A review on surface modifications for continuous dropwise condensation and a profitability analysis[J]. Journal of Advanced Research, 2019, 16: 1-13. DOI:10.1016/j.jare.2018.11.004.
[25] Beér J M. High efficiency electric power generation: the environmental role[J]. Progress in Energy and Combustion Science, 2007, 33(2): 107-134. DOI:10.1016/j.pecs.2006.08.002.
[26] Eral H B, ’t Mannetje D J C M, Oh J M. Contact angle hysteresis: a review of fundamentals and applications[J]. Colloid and Polymer Science, 2013, 291(2): 247-260. DOI:10.1007/s00396-012-2796-6.
[27] Antonini C, Carmona F J, Pierce E, et al. General methodology for evaluating the adhesion force of drops and bubbles on solid surfaces[J]. Langmuir, 2009, 25(11): 6143-6154. DOI:10.1021/la804099z.
[28] Acarlar M S, Smith C R. A study of hairpin vortices in a laminar boundary layer. Part 1. Hairpin vortices generated by a hemisphere protuberance[J]. Journal of Fluid Mechanics, 1987, 175(1): 1. DOI:10.1017/s0022112087000272.
