箭型排布的矩形微槽平板上液膜流动特性

光滑平板降膜受表面张力和接触角的影响易收缩成溪流，导致传热表面出现干斑，为解决这一问题，提出箭型排布的矩形微槽平板。通过可靠的computational fluid dynamics（CFD）计算模拟两相流理论，建立三维非稳态平板降膜数学模型，研究了箭型排布的矩形微槽平板上的液膜流动特性，并探究了微槽宽度、深度及箭型夹角对液膜在平板上铺展效果的影响。结果表明：箭型排布的矩形微槽可有效增大液膜在平板横向的铺展面积，使液膜润湿面积增大，减少平板表面干斑；在120°箭型结构下，矩形微槽最优参数为宽0.5 mm，深0.3 mm，此时可将比湿面积由光板表面的62%~89%提高到84%~94%；低雷诺数时，120°箭型结构对液膜横向铺展引导效果显著，雷诺数增大时，90°箭型结构引导效果更好。

Characteristics of liquid film flow on plates with an arrow-shaped arrangement of rectangular groove

As a result of the effects of surface tension and contact angle, the liquid film which on a general smooth flat plate tends to form a stream, with dry spots on a heat transfer surface. A set of plates having an arrow-shaped arrangement of rectangular grooves has been proposed in order to solve this problem. By means of reliable computational fluid dynamics (CFD) simulations and two-phase flow theory, a mathematical model of a three-dimensional unsteady falling film on a flat plate has been established. The characteristics of liquid film flow on the plates with an arrow-shaped arrangement of rectangular groove were studied by CFD simulation, and the influence of the micro groove width and depth, and the arrow angle on the film spreading on the plate were investigated. Our study found that the arrow-shaped arrangement of rectangular grooves effectively guides the film spreading on the plate transverse section, so that the liquid film wetting area increases, reducing the surface dry spots. Within the scope of the study, the optimal parameters were found to be a rectangular micro groove width of 0.5 mm and a depth of 0.3 mm; under these conditions, the wetting area increased from 62% to 89% on the smooth surface and from 84% to 94% on the surface within the groove. The 120° arrow structure has a significant effect on the horizontal spreading of the liquid film at low Re number, and the guidance effect of the 90° arrow structure improves with increasing Re number.