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Nucleate Boiling Heat Transfer on Plain and Microporous Surfaces in Subcooled Water OPEN ACCESS

[+] Author and Article Information
Seongchul Juna, Jinsub Kima

Multi-Scale Heat Transfer Lab, Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080, USA

Hwan Yeol Kimb

Severe Accident & PHWR Safety Division, Korea Atomic Energy Research Institute (KAERI), Daejeon, Korea

Seung M. Youa

Multi-Scale Heat Transfer Lab, Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080, USA
you@utdallas.edu

J. Heat Transfer 139(8), 080903 (Jun 05, 2017) Paper No: HT-17-1161; doi: 10.1115/1.4036877 History: Received March 20, 2017; Revised May 03, 2017

Abstract

The growth of hovering bubbles on Copper, High-Temperature Thermally-Conductive Microporous Coating (Cu-HTCMC) and plain surface were compared at 1,000 kW/m2 in nucleate boiling with different subcoolings. Images obtained by a high speed camera operating at 2,000 frames per second were used. The Cu-HTCMC was created by sintering copper powders with the average particle size of 67 μm and ∼300 μm thickness, which showed the optimized nucleate boiling and critical heat flux enhancement. The hovering bubble size became smaller as subcooling increased for both Cu-HTCMC and plain surface due to condensation by surrounding subcooled water. At 30 K subcooling, big hovering bubbles disappeared on both surfaces. Small bubbles were shown on plain surface and mists were shown on Cu-HTCMC surface. The hovering bubble sizes were close and the growth times were comparable for both surfaces in saturated and 10 K subcooling cases. However, the bubbles on Cu-HTCMC surface were smaller than those of plain surface at 20 K and 30 K subcoolings. This is believed to be due to the microporous structures shown in the SEM image (top left figure). The heat transfer coefficients of Cu-HTCMC were ∼300 kW/m2K for various subcoolings, about 6 times higher than those of plain surface (top right figure). The figure indicates slightly increasing trend of the heat transfer coefficient with subcooling. This is believed to be the result of the disappearance of relatively big size bubbles in Cu-HTCMC case.

Copyright (c) 2017 by ASME
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