Fabrication of Hydrophobic Coated Tubes for Boiling Heat Transfer Enhancement

摘要

The hot wire chemical vapor deposition method was applied for fabrication of hydrophobic fluoropolymer coatings on the surface of tubular heaters. The effect of hydrophobic surfaces (with static contact angle of 125°) on the local and integral heat transfer characteristics was studied during boiling of saturated water at atmospheric pressure, including high speed visualization. The heat transfer enhancement by 30% was observed in the range of low heat fluxes during boiling on the hydrophobic coated tubes. It was shown that the value of the bubble departure diameter and the nucleation site density significantly increased, and the bubble separation frequency was significantly reduced in comparison with the data obtained on the uncoated tube. The analysis of the operational characteristics of the synthesized coatings was carried out.