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International Heat Transfer Conference 16

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

BUBBLE DYNAMICS AND HEAT TRANSFER IN A WETTABILITY PATTERNED FLOW BOILING MICROCHANNEL

Hongzhao Wang
The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon Hong Kong SAR, China

Huihe Qiu
Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong

DOI: 10.1615/IHTC16.bae.024287
pages 1045-1052


KEY WORDS: Boiling and evaporation, Thermodynamics, Wettability Patterned Surface, Flow Boiling

Abstract

Flow boiling heat transfer in microspaces is of significant interest for thermal management applications, where the latent heat of phase change offers an efficient method to dissipate large heat fluxes in a compact device, such as a heat spreader or a heat pipe. However, a significant challenge for the implementation of microscale phase change heat spreaders is associated with micro/nano flow instabilities due to insufficient micro/nano bubble removal, leading to local liquid dry-out that severely limits the heat removal efficiency. Furthermore, for the various heat transfer mechanisms involved, it is difficult to predict the location of nucleation sites at which the onset of nucleate boiling (ONB) occurs. In this paper, we study the bubble dynamics and heat transfer in a flow boiling microchannel with a wettability patterned channel surface and compare it with a homogeneous hydrophilic channel surface. The bubble nucleation site and coalescence are studied experimentally. The effects of wettability patterned surfaces on bubble nucleation and contact line dynamics in a microchannel will be investigated utilizing high speed visualization techniques. Effects of mass flux on flow boiling in a wettability patterned microchannel are studied. Wettability patterned surfaces are manufactured on glass/silicon wafers. It is found that the heat transfer coefficient can be significantly enhanced by wettability patterns in comparison to a hydrophilic surface. The surface temperature with wettability patterned surfaces is lower than hydrophilic surfaces. The detailed experimental setup and results are presented in the paper.

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