R290蒸气珠状凝结传热微尺度特性的研究  

Investigations on Microscale Characteristics of R290 Vapor Dropwise Condensation Heat Transfer

作　　者：宁静红[1] 刘圣春[1] 叶庆银[2] 

机构地区：[1]天津商业大学天津市制冷技术重点实验室,天津300134 [2]天津商业大学制冷系,天津300134

出　　处：《流体机械》2013年第11期56-60,36,共6页Fluid Machinery

基　　金：国家自然科学基金项目(51006073)

摘　　要：通过对自然工质R290蒸气珠状凝结传热过程的微尺度特性分析得出,在一定的过冷度、液珠半径和分形维数下,液珠的导热热阻随接触角的增大而增大,促进层的热阻在接触角为90°时最小,气液界面的热阻随着接触角的增大而减小,单个液珠的总传热热阻随着接触角的增大呈现出先减小后增大的变化规律,即存在最佳接触角,在此最佳接触角下,单个液珠的总传热热阻最小,单个液珠的传热量最大,换热表面的热流密度最高。随着液珠半径的增大,最佳接触角减小。随着过冷度的增加和分形维数的增大,换热表面液珠成核中心密度增大,表面的热流密度增加。在一定的过冷度下,液珠半径增大,液珠分布密度减少,分形维数增大,液珠的分布密度增加。在一定的分形维数和过冷度下,随着液珠半径的减小,换热表面的热流密度增大。By analyzing the microscale characteristics of natural refrigerant R290 vapor dropwise condensation heat transfer,the following conclusions are obtained. At a certain subcooling degree,droplet radius and fractal dimension,the thermal resistance of single droplet conductivity increases with the increase of contact angle,the thermal resistance of promoting layer has the smallest value at the contact angle of 90°,the thermal resistance of vapor-liquid interface decreases with the increase of contact angle,the total thermal resistance of single droplet decreases first and then increases with the increase of contact angle,namely has proved the existence of the optimum contact angle,and at this optimum contact angle,the total thermal resistance of single droplet has a smallest value,the heat transfer capacity of single droplet and the heat flux of heat transfer surface have the largest value. Also,with the increase of droplet radius,the optimum contact angle decreases. Moreover,with the increase of subcooling degree and fractal dimension,the nucleation density of dropwise condensation increases on the heat transfer surface,so the heat flux enhances. At certain subcooling degree,with the increase of droplet radius,the distribution density of condensation droplet reduces,however,with the increase of fractal dimension,the distribution density of condensation droplet increases. At a certain fractal dimension and subcooling degree,with the reduceing of droplet radius,the heat flux of heat transfer surface increases.

关 键 词：自然工质R290 珠状凝结 分形维数 传热量 热流密度 

分 类 号：TH137[机械工程—机械制造及自动化] TB61[一般工业技术—制冷工程]