| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 107 === This research focused on condensation heat transfer of copper cylinder inside a closed chamber. The dimension of cylinder is 25mm in diameter and 50mm in length. Besides, the modification method is printing carbon nanotube (CNT) onto the copper surface with different printing area ratio: 0%, 30%, 50%, 70%, and 100% as one of controlling factors. The other one is the subcooling degree, which is the temperature difference between condensation wall and steam.
After measurement, the wettability of CNT printed area is hydrophilic, while the one of plain surface is hydrophobic. However, the experimental results showed that within lower interval of subcooling degrees, which is 0 to 7.5∘, the heat transfer coefficient and heat flux of the 30% and the 50% types are higher than the plain one. Accompanying the experimental images, hydrophilic surface has benefit to droplet movement and nucleation. On the other hands, the 30%, the 50%, and the 70% types worsen the heat transfer as the subcooling degree is >7.5∘ because the wetting transition induced the flooding upon the surface. From this research, even with hydrophilic patterns, the heat transfer performance could be enhanced during some subcooling degrees.
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