Experimental Study of Pool Boiling on Heaters with Nanomodified Surfaces under Saturation

Abstract

A technology has been developed for the synthesis of arrays of oriented microropes and cocoon-like microstructures consisting of silicon oxide nanowires on a copper substrate with barrier layers of silicon dioxide, molybdenum, and tungsten. In experiments, a copper surface coated with a tungsten layer showed the best stability and technological applicability. Experiments were performed to study pool boiling heat transfer on copper heaters with nanomodified surfaces under saturation conditions. A comparison of the data on heat transfer enhancement on smooth and nanomodified hydrophilic and hydrophobic copper surfaces was made. Relatively high heat transfer coefficients were observed on copper surfaces with a tungsten barrier layer initially coated with microropes and micrococoons. The experiments showed that microropes from nanowires were not resistant to boiling; micrococoons from nanowires were more stable. Superhydrophobic surfaces were produced by hot-wire chemical vapor deposition (HWCVD) of fluoropolymer coatings on micrococoons. In the boiling experiments, the greatest heat transfer enhancement was obtained on such surfaces. The fluoropolymer coating was shown to lose its continuity. As a result, a random biphilic coating was formed and intense bubble boiling occurred in local hydrophobic areas of the fluoropolymer, resulting in heat transfer enhancement.