Effect of wettability of a porous stainless steel on thermally induced liquid-vapor interface behavior

• Published in: Surface topography metrology and properties 2017-12, Vol.5 (4), p.44006
• Main Authors: Oka, C, Odagiri, K, Nagano, H
• Format: Article
• Language: English
• Subjects: liquid-vapor interface behavior; microscale observation; porous stainless steel; wettability improvement
• ISSN: 2051-672X; 2051-672X
• DOI: 10.1088/2051-672X/aa9499

Control of thermally induced liquid-vapor interface behavior at the contact surface of porous media is crucial for development of two-phase heat transfer devices such as loop heat pipes. The behavior experiences three modes with increase of heat flux, and the middle mode possesses the highest heat transfer performance. In this paper, the effect of improving wettability of the porous media is demonstrated experimentally and numerically for the first time, in particular with regard to the effect on a domain of the middle mode. Ethanol wettability of a porous stainless steel was improved via a facile method, which was a simple acid treatment. As a result, the domain of the middle mode was extended as a consequence of the wettability improvement. The mode transfers from the middle to the last one when the pressure drop in the liquid supply exceeds the capillary pressure of liquid bridges formed between the heating plate and the porous medium. Hence, the extension of the domain suggested that the capillary pressure was increased by the wettability improvement. This was verified via numerical calculation. The calculated capillary pressure was increased by 7% after improving wettability, which resulted in the extension of the domain of the middle mode.