Surface wettability effects on critical heat flux of boiling heat transfer using nanoparticle coatings

• Main Authors: Chin-Chi Hsu, 許進吉
• Other Authors: 陳炳煇
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/52720694857988320636

博士 === 國立臺灣大學 === 機械工程學研究所 === 100 === This thesis investigates the effects of various isotropic and interlaced wettability of surface on pool boiling heat transfer. Nano-silica particle coatings were used to vary the wettability of the copper surface from superhydrophilic to superhydrophobic by modifying surface topography and chemistry. Experimental results show that critical heat flux values are higher in the hydrophilic region. Conversely, critical heat flux values are lower in the hydrophobic region. The experimental critical heat flux data of the modified surface do not fit the classical models. Therefore, this study proposes a simple model to build the nexus between the surface wettability and the growth of bubbles on the heating surface. The experimental results revealed that, when the wettability of a surface is uniform, the critical heat flux increases with the more wettable surface; however, when the wettability of a surface is modified interlacedly, regardless of whether the modified region becomes more hydrophilic or hydrophobic, the critical heat flux is consistently higher than that of the isotropic wettability surface. In addition, this study also observed that CHF was higher when the contact angle difference between the plain surface and the modified region was smaller.