不凝性气体对竖直平板对流冷凝的影响  

Effect of non-condensable gas on convective condensation on a short vertical plate

作　　者：刘泉[1] 杨渐志[1] 顾海林[1] 钱万益 刘明侯[1] 

机构地区：[1]中国科学技术大学热科学和能源工程系,安徽合肥230027

出　　处：《中国科学技术大学学报》2015年第5期397-403,共7页JUSTC

基　　金：国家自然科学基金(11372302;11172296)资助

摘　　要：数值研究了不凝空气质量分数、液膜、空气-蒸气流速等对竖直平板冷凝过程的影响.气液两相流采用流体体积(VOF)法模拟,水蒸气在不凝空气中的输运过程采用组分输运方法模拟.基于气体分子动力学基本理论推导出相变模型,对纯蒸气冷凝过程数值计算并与理论解比较,确定模型系数.数值结果表明,少量不凝空气对蒸气对流冷凝的影响并不十分明显;随着不凝空气质量分数的增加,冷凝换热明显下降;含少量不凝空气的蒸气对流冷凝在忽略液膜影响时壁面换热系数约升高8%;水蒸气-空气混合气体流速升高对对流冷凝换热系数的提升低于纯对流换热.The effect of mass fraction of non‐condensable air ,liquid film and velocity of air‐vapor mixture on the convective condensation on a short vertical plate was investigated numerically .The volume of fluid （VOF） was applied to model the two‐phase flow of liquid film and gases mixture .The species transport between water vapor and air was calculated by the conservation equation for species .A modified phase change model ,derived from basic equations related to the kinetic gas theory ,was proposed and verified by two different cases .It was found that a small amount of non‐condensable gas shows no significant effect on the convective condensation of water vapor . However , the heat transfer coefficient of convective condensation shrinks obviously as air concentration increases .And the heat transfer coefficient is about 8%higher than that of not ignoring liquid film . The heat transfer coefficient of convective condensation improves by increasing inlet velocity of the gas mixture to a lower extent than pure water vapor convection .

关 键 词：不凝性气体 对流冷凝 数值模拟 

分 类 号：TK124[动力工程及工程热物理—工程热物理]