Abstract We report evaporation characteristics due to higher heating from above from surfaces having an array of line sources. The line sources are created by vertically stacked rectangular plates in a box with water. Two different types of plates were used. In one case line source or film thickness was 66 µm and open area ratio was 4%, and in the second case film thickness was 28 µm and 20% was the open area ratio. Even at the 4% open area ratio the evaporation rate was ∼85% compared to a bare water surface, at the same heat flux. Lateral conduction of heat from the impervious hotter regions to the line sources and the 2-D nature of diffusion near these tiny line sources enhances the evaporative flux, owing to increase in the concentration gradient of water vapour, explains the high evaporation rate, observed in the present work. This system bridges the gap between the understanding of evaporation from bare water surfaces (1-D vapour diffusion) and leaf surfaces (3-D vapour diffusion). Evaporation rates for the fully saturated conditions are in good agreement with the theoretical predictions of Suzuki and Maeda (1968) and Schlunder (1988). The computed surface temperatures and its width-wise variation match well with the experimental values. We also propose a simple film model for the unsaturated condition of the porous medium and show that the temperature distribution obtained using this model is in reasonably good agreement with the measured values.

中文翻译：

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低孔隙度表面线水源蒸发的实验和数值研究

摘要我们报告了由于具有一系列线源的表面从上方加热更高而导致的蒸发特性。线源由垂直堆叠在装有水的盒子中的矩形板创建。使用了两种不同类型的板。在一种情况下，线源或薄膜厚度为 66 µm，开口面积比为 4%，在第二种情况下，薄膜厚度为 28 µm，开口面积比为 20%。即使在 4% 的开放面积比下，在相同的热通量下，与裸水表面相比，蒸发率也为 85%。热量从不可渗透的较热区域到线源的横向传导以及这些微小线源附近的二维扩散性质增强了蒸发通量，这是由于水蒸气浓度梯度的增加，解释了高蒸发率，在现在的工作。该系统弥补了对裸水表面蒸发（1-D 蒸汽扩散）和叶表面（3-D 蒸汽扩散）的理解之间的差距。完全饱和条件下的蒸发率与 Suzuki 和 Maeda (1968) 以及 Schlunder (1988) 的理论预测非常一致。计算出的表面温度及其横向变化与实验值非常吻合。我们还为多孔介质的不饱和条件提出了一个简单的薄膜模型，并表明使用该模型获得的温度分布与测量值非常吻合。完全饱和条件下的蒸发率与 Suzuki 和 Maeda (1968) 以及 Schlunder (1988) 的理论预测非常一致。计算出的表面温度及其横向变化与实验值非常吻合。我们还为多孔介质的不饱和条件提出了一个简单的薄膜模型，并表明使用该模型获得的温度分布与测量值非常吻合。完全饱和条件下的蒸发率与 Suzuki 和 Maeda (1968) 以及 Schlunder (1988) 的理论预测非常一致。计算出的表面温度及其横向变化与实验值非常吻合。我们还为多孔介质的不饱和条件提出了一个简单的薄膜模型，并表明使用该模型获得的温度分布与测量值非常吻合。