Do surfaces with mixed hydrophilic and hydrophobic areas enhance pool boiling?

Abstract

We demonstrate that smooth and flat surfaces combining hydrophilic and hydrophobic patterns improve pool boiling performance. Compared to a hydrophilic surface with 7º 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.

Pool boiling with high heat flux enabled by a porous artery structure

“…In this latter case, a variety of methods have been proposed, such as the fabrication of nano-or micro-scale functional structures, [8][9][10][11][12] deposited nanoparticle layers, [13][14][15][16][17][18] atomic layer deposition, [19][20] micro/nano porous coatings [21][22][23][24][25] and hybrid wettability treatments. [26][27][28] Significant progress has been made in the area of CHF enhancement. In particular, the CHF of nucleate boiling for a 3 smooth surface was enhanced by a factor of three through the use of a modulated microporous coating applied directly onto the heated surface.…”

Wettability Effects on Heat Transfer

“…Recently, interesting phenomena related with superhydrophilic/ hydrophobic have been reported. For example, an enhancement of both the heat transfer and the critical heat flux using the hydrophobic and hydrophilic mixed surface was reported by Betz et al (2010). Various heat transfer applications related with these special surfaces are accelerated by new micro/nano structured surface fabrication techniques, because the surface wettability can be changed by only different material deposition (Phan et al, 2009b).…”

Biphilic nanoporous surfaces enabled exceptional drag reduction and capillary evaporation enhancement

“…19 To achieve superior fluid flow and heat transfer rate during nucleate boiling and evaporation, hybrid surfaces consisting of both hydrophilic and hydrophobic features are highly desirable because the composite surface wettability is superior to liquid spreading by generating favorable capillarity and maintaining low friction. 20,21 Although these composite surfaces with microscale hydrophilic and hydrophobic areas have been developed to enhance capillary flow 22,23 and boiling heat transfer, 22,24 they can neither impact the nanoscopic slip length nor effectively reduce the pinning forces governed by the contact line. 25 CNT-enabled hydrophobichydrophilic nanoporous surfaces have been shown to substantially enhance nucleate boiling in our previous study by tuning surface wettability at nanoscale.…”