摘要
引入沟流级别的概念解释过渡状冷凝形态的形成特征,并在此基础上,将过渡状冷凝传热表示为通过滴状区与沟流区上的传热之和,建立了反映界面效应影响的过渡状冷凝传热模型.设计了人工形成沟流形态的冷凝表面,其实验结果与模型计算结果吻合;模型计算也与实际自然形成沟流冷凝形态的传热过程吻合.模型对滴状区的传热计算,以液滴分布时间序列构象模型为基础,并将滴状区最大液滴与沟流级别相关联,得到与界面效应相关的滴状区传热模型;沟流区传热计算,以在一定厚度液膜上的冷凝传热模型为基础,并根据沟流形态模型,求出液膜厚度与沟流区所占面积分率.模型描述了过渡状冷凝形态形成特征以及过渡状冷凝传热系数随表面自由能差渐进变化的规律.
The concept of rivulet degree was introduced to elucidate the evolution characteristics of transition condensation on a condensing surface, such that the heat flux through the surface could be expressed as the summation of the flux values through the dropwise region and rivulet regions respectively. For the heat flux in the dropwise region, droplets with the maximum diameter were correlated with the rivulet degree, on the basis of a time conformation model of droplet size distribution, to establish the heat transfer model in the dropwise region related to surface effect. In the rivulet region, the liquid film thickness and the area fraction covered by the rivulet region would be calculated by using the model of condensation heat transfer through a liquid film with certain thickness. The heat flux through the whole surface was the weighted mean of the values of the two regions mentioned above. The present model also explained the gradual change of heat transfer coefficient of transition condensation with surface free energy difference. The experiments of transition condensation heat transfer were conducted for a specially designed surface. The present model predictions agreed well with the experimental data and those reported in the literature. It could be useful in modeling the transition of condensation pattern from dropwise to filmwise, and establishing a unified model for the whole process of condensation heat transfer.
出处
《化工学报》
EI
CAS
CSCD
北大核心
2006年第11期2536-2542,共7页
CIESC Journal
基金
国家自然科学基金项目(50376005
59906002).~~
关键词
过渡状冷凝
沟流
液固界面效应
表面自由能差
transition condensation
rivulet
interracial interaction
surface free energy difference
