Boiling Heat Transfer Enhancement on Biphilic Surfaces

Abstract

Flat surfaces with different patterns of hydrophobic spots were employed for experimental investigation of boiling heat transfer. In one case, hydrophobic spots were created on a smooth copper surface and on a surface coated with arrays of micrococoons from silicon oxide nanowires by vapor deposition of a fluoropolymer. In the second case, a hydrophobic coating was deposited on heater surfaces with cavity microstructures formed by laser ablation and chemisorption of fluorinated methoxysilane. Water under saturation conditions at atmospheric pressure was used as the working liquid. The temperature of the heating surface was varied from 100 to 125 °C, and the maximum value of the heat flux was 160 W/cm2. Boiling heat transfer on the test biphilic surfaces was significantly (up to 600%) higher than on non-biphilic surfaces. Surface texture, the shape of hydrophobic regions, and the method of their creation tested in this study did not show a significant effect on heat transfer. The boiling heat transfer rate was found to depend on the size of hydrophobic spots, the distance between them, and hence the number of spots. The highest heat transfer efficiency was detected for the surface with the largest number of hydrophobic spots. After long-term experiments (up to 3 years), the heat transfer coefficient on the obtained surfaces remained higher than on the smooth copper surface. Biphilic surfaces with arrays of cavities formed by laser ablation turned out to be the most stable during prolonged contact with boiling water.

Superbiphilic Laser‐Microengineered Surfaces with A Self‐Assembled Monolayer Coating for Exceptional Boiling Performance

“…Additionally, Chinnov et al. [ 48 ] have underscored the significance of the sustained and enduring boiling performance characteristics of manufactured biphilc coatings on boiling interfaces. This emphasis on longevity is a relatively infrequent aspect within the broader community of researchers in the field of boiling.…”

“…The nucleation of the bubbles takes place in the hydrophobic areas, while the hydrophilic areas serve to prevent coalescence of the bubbles and provide liquid supply through wicking toward hydrophobic areas. Additionally, Chinnov et al [48] have underscored the significance of the sustained and enduring boiling performance characteristics of manufactured biphilc coatings on boiling interfaces. This emphasis on longevity is a relatively infrequent aspect within the broader community of researchers in the field of boiling.…”

Boiling heat transfer on modified copper surfaces with inhomogeneous wettability

“…The number of hydrophobic spots is 506 and 69, respectively, similar to the previous case. The elemental composition of these coatings was analyzed by the EDS method [8]. Thus, it was confirmed that the composition of the spots corresponds to the fluoropolymer, and there is no fluoropolymer in the space between the spots.…”

Laser Treatment Technique for Boiling Heat Transfer Application

“…It was concluded that both kinds of microstructures enhanced boiling due to agitated movement caused by evaporation as well as the rewetting process at bubble detachment. Chinnov et al [6] experimentally analyzed water boiling on heaters with different patterns of hydrophobic spots made on the copper surface as well as the surface covered with a matrix of micrococoons made of silicon oxide nanowires. It was reported that biphillic heaters showed better performance that non-biphillic ones.…”