Time effect on wetting transition of smart surface and prediction of the wetting transition for critical heat flux in pool boiling

• Published in: International journal of heat and mass transfer Vol. 114; pp. 735 - 742
• Main Authors: Kim, Jin Man, Kim, TaeJoo, Yu, Dong In, Kim, Moo Hwan, Moriyama, Kiyofumi, Park, Hyun Sun
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-11-2017; Elsevier BV
• Subjects: Contact angle; Correlation; Critical heat flux; Effects; Exponential functions; Heat flux; Heat transfer; Heat treatment; Hydrophobic surfaces; Pool boiling; Temperature; Time effect; TiO2; Titanium oxides; Wettability; Wetting; Wettability; Critical heat flux; Time effect; Pool boiling; TiO2
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2017.06.114

•A wetting transition of TiO2-coated surface (TCS) was used for CHF enhancement.•The variation of receding contact angle was investigated through heat treatment.•An empirical correlation for receding contact angles includes temperature and time.•The CHFs on TCS were predicted using the empirical correlation.
A smart surface that is a TiO2-coated surface (TCS) is a hydrophobic surface initially, but becomes a hydrophilic surface when heated. Therefore, such a surface can be used to enhance both boiling heat transfer (BHT) and critical heat flux (CHF) in pool boiling. In the present study, the time effect of the wetting transition of TCS was focused on. The CHF on TCS was enhanced more when the holding time of the heat flux in high-temperature regime was increased. By observing changes in contact angles on TCS through heat treatment in air, it was found that the wetting transition was affected not only by the temperature, but also by the time. Thus, a variation of the receding contact angle was correlated in the form of an exponential function. The suggested empirical correlation includes temperature and time, and it describes the transition of the receding contact angle. The correlation was also used to predict the CHF on TCS in pool boiling. As a result, CHFs on TCS could be explained using the correlation.