制冷空调系统水平管降膜蒸发研究

在制冷剂面临严峻的环境保护控制要求的背景下，研究表明，降膜蒸发由于其较低的制冷剂充注量在制冷空调行业具有重大的应用潜力。本文主要从降膜蒸发管外液膜的流动模式和强化传热2个方面，对水平管降膜蒸发的国内外研究现状进行研究分析。分析表明，管外液膜存在滴状流、射（柱状）流和片状流等模式，而且强化传热须区分高低热流密度情况。为了进一步探究降膜蒸发的机制，从换热和可视化的角度开展强化管外降膜蒸发的特性实验研究。

Research on falling film evaporation on horizontal tubes of refrigeration and air-conditioning system

On the background of controlling refrigerants for their serious environmental problem,researches indicate that falling film evaporation has a great application potential because of its low refrigerants charge in refrigeration and air-conditioning industry. Analy- zes the research status at home and abroad about falling film evaporation on horizontal tubes from two aspects： flow mode and enhanced heat transfer of the liquid membrane out of the tubes. As analysis shows that the liquid membrane out of the tubes exist some kind of modes such as droplet flow, shoot （columnar） flow, flake flow and so on, and enhanced heat transfer must distinguish between high heat flux and low heat flux. In order to further exploring the mechanism of falling film evaporation, takes the experimental studies about characteristics of enhanced falling film evaporation out of the tubes from the angles of heat transfer and visualization.