Enhancement of Film Condensation Using a Porous Coating: A Theoretical and Experimental Investigation

研究了在固体不透水表面上使用高导电性和渗透性的多孔涂层来强化膜冷凝过程中的换热。一个初步的简单的薄膜冷凝模型将被扩展，以开发一个更复杂的模型来预测冷凝速度。将报告水平和倾斜平板和管子的传热率。先进的模型将包括液/汽界面上的匹配条件，这些条件将考虑蒸汽阻力、强迫对流和相对渗透率的影响。理论研究的主要结果将是证明气膜厚度、速度和温度分布以及局部换热系数与多孔基质参数的关系，并将这些结果与(I)Nusselt的经典分析和(Ii)其他强化气膜冷凝的先进方法(例如，整体式或凹槽翅片表面)进行比较。研究的实验部分将侧重于从多孔涂层表面获取薄膜冷凝换热数据，并在广泛的实验条件下对冷凝过程进行摄影观察。通过将氟里昂-113冷凝在倾斜的多孔涂层平板上，可以获得传热系数的测量结果。实验结果验证了理论膜冷凝模型，该模型预测了相当大的换热系数。

An investigation of the enhancement of heat transfer in film condensation with the use of a highly conductive and permeable porous coating on a solid impermeable surface is to be made. A preliminary simple film condensation model will be expanded to develop a more complex model for predicting the condensation rate. Heat transfer rates for horizontal and inclined plates and tubes will be reported. The advanced model will incorporate matching conditions at the liquid/vapor interface which will account for the effects of vapor drag, forced convection and relative permeability. The main results of the theoretical research will be to document the dependence of the film thickness, velocity and temperature distributions, and local heat transfer coefficient on the porous matrix parameters and to compare these results to (i) the classical analysis of Nusselt and (ii) other advanced methods of enhanced film condensation (e.g., integral or fluted fin surfaces). The experimental part of the investigation will focus on the acquisition of film condensation heat transfer data from a porous coated surface and on photographic observations of the condensation process over a wide range of experimental conditions. Measurements of the heat transfer coefficient will be obtained by condensing Freon-113 on an inclined porous coated plate. Verification of the theoretical film condensation model, which predicts a considerable heat transfer coefficient, is anticipated by the experimental results.