Do surfaces with mixed hydrophilic and hydrophobic areas enhance pool boiling

By A. Betz, Jie Xu, H. Qiu, Daniel Attinger. 2010

449 citations recorded by the source corpus.

We demonstrate that smooth and flat surfaces combining hydrophilic and hydrophobic patterns improve pool boiling performance. Compared to a hydrophilic surface with 7° wetting angle, the measured critical heat flux and heat transfer coefficients of the enhanced surfaces are, up to respectively, 65% and 100% higher. Different networks combining hydrophilic and hydrophobic regions are characterized. While all tested networks enhance the heat transfer coefficient, large enhancements of critical heat flux are typically found for hydrophilic networks featuring hydrophobic islands. Hydrophilic networks indeed are shown to prevent the formation of an insulating vapor layer. © 2010 American Institute of Physics. doi:10.1063/1.3485057 Boiling is an efficient process to transfer large amounts of heat at a prescribed temperature because of the large latent heat of vaporization. The term flow boiling describes the boiling of liquids forced to move along hot surfaces, while in pool boiling, the topic handled in this paper, the liquid is stagnant and in contact with a hot solid surface. 1 Besides the common experience of boiling water in an electric kettle, pool boiling has applications in metallurgy, high performance heat exchangers, and immersion cooling of electronics. Pool boiling performance is measured with two parameters, the heat transfer coefficient HTC and the critical heat flux CHF. The CHF is measured by increasing the surface temperature until a transition from high HTC to very low HTC occurs. This signifies the formation of a vapor film insulating the liquid from the heated surface, a phenomenon called dry out. Several characteristics determine the performance of a boiling surface. Nucleation sites in appropriate number and dimensions need to be provided such as cavities, rough areas, or hydrophobic islands. 2 As of today, the performance of boiling surfaces has been increased by using wicking structures to prevent dry out, 3 by increasing the surface area with fins or fluidized bed, 3‐6 and by enhancing the wettability of the surface. 5‐10 The latter strategy is justified by experiments of Wang and Dhir, 11 showing that the CHF was

Subfields: Aerospace Engineering, Biomedical Engineering, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/7c30c52ddeb67d051eede1576cf98ae71983d8d5

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Citations in the corpus

Boiling heat transfer on superhydrophilic, superhydrophobic, and superbiphilic surfaces (2012, methodology): “surface roughening, etching of c avities [20, 27, 28], or microporous coatings [29, 30].”
Enhanced pool-boiling heat transfer on laser-made hydrophobic/superhydrophilic polydimethylsiloxane-silica patterned surfaces. (2015, background): “[13] found that hydrophobic spots on a hydrophilic surface improved both the CHF and HTC over a plain hydrophilic surface by 65% and 100%, respectively.”
Review of pool boiling enhancement by surface modification (2019, background): “[434] produced hydrophobic and hydrophilic patterns with maximum height of 100 nm on oxidized silicon wafers, with surface roughness maintained below 5 nm.”