Abstract

The paper presents the results of a study of heat transfer in a falling film of freon R21 on a single-row bundle of horizontal tubes made of aluminum alloys with outer diameters of 10 mm and modified oxide porous coatings. The oxide coatings were deposited by micro-arc oxidation (MAO) in phosphate, acid, and silicate-alkaline electrolytes. The surface modification of the MAO coatings consisted in the deposition of copper particles in a solution of copper sulphate. The heat transfer coefficients for the modified MAO coatings were compared with the results for the surface of tubes with base MAO coatings in electrolytes of similar compositions, as well as for a smooth metal tube without coating for Reynolds numbers of the falling film varying from 600 to 1500. Additional surface treatment of the porous ceramic coatings by the deposition of copper particles has led to a significant decrease in the heat transfer coefficients in the falling film compared with the base MAO coatings. The highest enhancement of the heat transfer relative to the case of the smooth tube (of up to 80%) was obtained on the modified MAO coating deposited in the phosphate electrolyte.

中文翻译：

---

具有改性 MAO 涂层的水平管阵列上氟利昂 R21 下降液膜的传热

摘要

本文介绍了外径为 10 毫米的铝合金和改性氧化物多孔涂层制成的单排水平管束上氟利昂 R21 降膜传热研究的结果。氧化物涂层是通过微弧氧化（MAO）在磷酸盐、酸性和硅酸盐碱性电解质中沉积的。MAO 涂层的表面改性包括在硫酸铜溶液中沉积铜颗粒。将改性 MAO 涂层的传热系数与具有类似成分的电解质中具有基础 MAO 涂层的管表面的结果以及没有涂层的光滑金属管的结果进行比较，降膜的雷诺数从 600 到 500 不等。 1500。通过沉积铜颗粒对多孔陶瓷涂层进行额外的表面处理，与基础 MAO 涂层相比，降膜中的传热系数显着降低。相对于光滑管的情况，传热的最高增强（高达 80%）是在磷酸盐电解质中沉积的改性 MAO 涂层上获得的。