Investigation of surface wetting with different structures and intensification of heat transfer during condensation on a tube

Аuthors

Kuzma-Kichta Y. A.¹, Ivanov N. S.^1*, Alyautdinova М. М.²

1. National Research University “Moscow Power Engineering Institute”, 14, Krasnokazarmennaya str., Moscow, 111250 Russia
2. National Research University «Moscow Power Engineering Institute», Krasnokazarmennaya str., 17, bldg. 1G, Moscow, 111250, Russia

*e-mail: ivanovniks@mpei.ru

Abstract

This study presents an experimental investigation of the influence of surface modifications of a cop-per substrate (100×100×3 mm) on wettability and heat transfer characteristics during condensation. Three types of surfaces were examined: a technically smooth copper plate with a natural oxide layer, a surface with micro-depressions approximately 80 μm in diameter formed by abrasive deformation, and a combined coating consisting of these depressions and a layer of carbon nanoparticles (50–100 nm) stabilized by a polymer binder. Measurements were taken at 100 points with a 10 mm step to ob-tain statistically significant contact angle distributions. The contact angle distributions for the investi-gated surfaces were obtained. For the technically smooth surface, the contact angle ranged from 60° to 70°, which is consistent with reported values for oxidized copper. The introduction of 80 μm de-pressions shifts the distribution, increasing the contact angles to a range of 90–110°. Application of the combined coating based on nanoparticles and a polymer binder further enhances hydrophobicity, shifting the distribution and yielding contact angles between 148° and 155°. Based on the obtained contact angle distribution data, an estimation of the average heat transfer coefficient was performed. It is shown that the results of this estimation are consistent with the experimental data on heat transfer during condensation on a hydrophobic-coated tube, according to which the heat transfer coefficient increases by a factor of two. The study establishes a correlation between surface microstructure, con-tact angle distribution statistics, and condensation heat transfer intensity, providing a basis for the ra-tional design of enhanced heat transfer surfaces.

Keywords:

wetting, contact angle, hydrophobic coatings, micro- and nanostructures, surface depressions

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