微通道冷凝研究的进展与展望

微通道中的冷凝在微热管及微型燃料电池等器件中有着广泛的应用。本文综述了当前国内外微通道冷凝研究的现状，展望了该领域的未来研究方向。大量研究表明，控制微通道中冷凝与两相流动的主要作用力不是重力或浮力，而是表面张力。最新实验结果发现，随着通道直径的减小，微通道中主要的冷凝流型是间断的喷射流/弹状流/泡状流，而不是传统大直径通道中出现的由重力作用而导致的分层环状流。因此，未考虑表面张力的大尺度冷凝模型已不能完整描述微通道内的流动冷凝过程。对于间断流型，基于实验数据的半理论模型或经验关联式可能更为实用有效。润湿性和表面粗糙度等通道表面特性在微通道流动冷凝中有着重要的影响，这些因素的优化将会强化微通道中的冷凝换热。

Review of condensation in microchannels

Condensation in microchannels has been widely used in a variety of advanced micro thermal devices,such as micro heat pipe and micro fuel cell.Presented here is a review of investigations of condensation in microchannels.The future progress is also presented.Extensive research indicates that surface tension,rather than body or buoyancy forces,is the dominant force that governs the condensation and two-phase flow in microchannels.Recent experimental results show that with the decrease in channel diameter,the dominant condensing flow pattern is intermittent injection/slug/bubble flow,as opposed to stratified annular flow,which are typically found in larger one-g channel flows.As a result,existing condensation models without considering surface tension can not be used to accurately represent or predict the actual physical mechanisms that occur in these condensing flows in microchannels.This,therefore necessitates the use of semi-theoretical models or correlations based upon experimental data.Since wettability and surface roughness play an important role in the condensing flow in microchannels,an optimization of these effects may provide a mechanism by which very high condensation heat fluxes can be achieved.