Effect of boundary wettability on natural convection heat transfer in a rectangular enclosure
Date Issued
2012
Date
2012
Author(s)
Huang, Yi-Shiang
Abstract
This study aims to investigate the effect of boundary wettability on natural convection heat transfer in a rectangular enclosure. Different levels of boundary wettability are established by utilizing sol-gel method which is one of the surface modification methods to create the hydrophilic and hydrophobic surface for bottom surface of Rayleigh-Bénard convection. The contact angles of copper plates via the surface modification method are about 10 and 160 degree which can be treated as hydrophilic and hydrophobic surfaces, respectively, and the contact angles of copper plates without surface modification is about 93 degree in this study. To tell the difference in heat transfer, Nusselt number is the dimensionless parameter which is discussed in this study. Aspect ratio of testing condition is 0.5~2, the corresponding Rayleigh number is 10^5~10^7.
The experimental results of plain copper surface in this study are quite match to the experimental results and analysis in previous studies by other researchers. There is no difference between the hydrophilic surfaces and the plain surfaces in Nusselt number. However, compare with the plain plates, the Nusselt number of hydrophobic surfaces is less than 16%. This thesis also observed the relation between temperature and bubble growth in the different levels of boundary wettability.
Subjects
natural convection
wettability
Nusselt number
Type
thesis
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