物理学报Issue(13)：1-8,8.DOI:10.7498/aps.64.134704
液滴撞击加热壁面传热实验研究∗
Exp erimental study of heat transfer from droplet impact on a heated surface
摘要
Abstract
Droplets impact on surfaces exist widely in industrial equipments, such as spraying cooling, ink jet printing, oil drops impact on walls in combustion chamber, brine droplets impact on heat transfer tubes in horizontal-tube falling film evaporators etc. In particular, for the droplets impinging on heated surfaces, the contact scale and the heat transfer flux affect the cooling of the hot surfaces greatly. In this work, evaporation processes of water and ethanol droplets impact on a heated surface are observed using a high-speed digital camera with a capacity of 106 frames per second. The corresponding evaporation parameters including the contact diameter, the droplet height, the contact angle, and heat flux are analyzed. The initial liquid temperature keeps constant at 20 ◦C, and the initial surface temperature varies in the range of 68—126 ◦C. Diameters of single water droplets and ethanol droplets are 2.07 and 1.64 mm, respectively. The impact Weber number of water droplets ranges from 2 to 44 while that of ethanol droplets ranges from 3 to 88. The present results show that due to the coupled effects of gravity, surface tension, fluid flow and evaporation processes, the height of water droplets reduces continuously while the contact diameter almost does not change during the most part of evaporation time. In the later stage of evaporation, the contact diameter, height and contact angle of water droplets oscillate, mainly because of droplet retraction. The critical contact angle for water droplets retraction is in the range of 4◦–8◦. The contact angle of ethanol droplets first reduces and then remains constant, while the contact diameter and the height decrease continuously. The droplet evaporation time depends on liquid properties and the surface temperature, and the Weber number effect is minor. The evaporation time decreases with the increase in the surface temperature. At the same time, with increasing surface temperature, the ratio between the sensible heat and the total heat increases, and this part of heat cannot be neglected from the total heat transfer calculation. Based on the present experimental conditions, the average heat flux for the water droplets ranges from 0.014 to 0.110 W·mm−2 in this work.关键词
液滴撞击/加热壁面/接触直径/热流密度Key words
droplet impact/heated surface/contact diameter/heat flux引用本文复制引用
沈胜强,张洁珊,梁刚涛..液滴撞击加热壁面传热实验研究∗[J].物理学报,2015,(13):1-8,8.基金项目
国家自然科学基金重点项目(批准号:51336001)资助的课题.* Project supported by the Key Program of the National Natural Science Foundation of China (Grant No.51336001) （批准号:51336001）
