Limited Enhancement of Subatmospheric Boiling on Treated Structured Surfaces With Biphilic Pattern
- 8 September 2021
- journal article
- research article
- Published by ASME International in Journal of Heat Transfer
- Vol. 143 (10)
- https://doi.org/10.1115/1.4051056
Abstract
Boiling heat transfer suffers deteriorations under subatmospheric conditions, which can be attributed to a shortage of viable nucleation sites at declining pressures. In this work, the possibility of enhancing low-pressure saturated boiling of water using a combination of wettability patterning and structural modifications was experimentally explored. The copper test surface, comprised of an array of circular "dimples" (0.3 mm in depth, 0.5 mm in diameter, and 3.0 mm in pitch), was spray-coated by PTFE (polytetrafluoroethylene) coatings so as to form a matching biphilic pattern with the surface cavities. The resulting dimpled biphilic surface showed appreciable heat transfer enhancement-with a maximum 60% increase of the average heat transfer coefficient of nucleate boiling compared with a flat biphilic surface-down to about 9.5 kPa. Further lowering the pressure to 7.8 kPa, however, was found to lead to diminished performance gains. The visualization study of the bubble departure dynamics revealed signs of additional vapor trapping of the hydrophobic-coated cavities, which can induce uninterrupted bubble regeneration with zero waiting time and explain the qualified enhancement of subatmospheric boiling. Thanks to a potential secondary pinning of contact line inside the hydrophobic cavities, incomplete bubble detachment could prevail at somewhat lower pressures than was otherwise possible without the dimple structure, leaving behind significantly more vapor residues. However, the vapor trapping capacity was found to decrease with pressure, which provided clues with regard to the reduced efficacy of the surface at even lower pressures.Keywords
Funding Information
- Japan Society for the Promotion of Science (20K04312)
This publication has 48 references indexed in Scilit:
- A study of nucleate boiling heat transfer on hydrophilic, hydrophobic and heterogeneous wetting surfacesInternational Journal of Heat and Mass Transfer, 2011
- Pool Boiling Heat Transfer and Bubble Dynamics Over Plain and Enhanced MicrochannelsJournal of Heat Transfer, 2011
- Numerical Simulation of Dynamics and Heat Transfer Associated With a Single Bubble in Subcooled Boiling and in the Presence of NoncondensablesJournal of Heat Transfer, 2011
- Numerical Simulations of the Dynamics and Heat Transfer Associated With a Single Bubble in Subcooled Pool BoilingJournal of Heat Transfer, 2010
- Experimental evaluation of constants for the Rohsenow pool boiling correlationInternational Journal of Heat and Mass Transfer, 1999
- Effect of Surface Wettability on Active Nucleation Site Density During Pool Boiling of Water on a Vertical SurfaceJournal of Heat Transfer, 1993
- Experimental Observations of the Microlayer in Vapor Bubble Growth on a Heated SolidJournal of Heat Transfer, 1983
- A New Correlation of Pool-Boiling Data Including the Effect of Heating Surface CharacteristicsJournal of Heat Transfer, 1969
- Photographic Study of Nucleate Pool Boiling on a Horizontal SurfaceJournal of Heat Transfer, 1965
- On the Size Range of Active Nucleation Cavities on a Heating SurfaceJournal of Heat Transfer, 1962