2002 Fiscal Year Final Research Report Summary
Development of Heat Transfer Surface using Superhydrophilic Photocatalyst
| Project/Area Number |
12555059
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Thermal engineering
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| Research Institution | Kyushu University |
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Principal Investigator |
TAKATA Yasuyuki Kyushu University, Faculty of Engineering, Associate Professor, 大学院・工学研究院, 助教授 (70171444)
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| Co-Investigator(Kenkyū-buntansha) |
SHIMOHIGOSHI Mitsuhide TOTO, R&D Center, Chief Researcher, 基礎研究所・イドロテクト研究部, 研究主査(研究職)
WATANABE Toshiya The University of Tokyo, Research Center for Science and Technology, Professor, 先端科学技術研究センター, 教授
YOSHIDA Keisuke Kyushu University, Faculty of Engineering, Associate Professor, 大学院・工学研究院, 助教授 (60191582)
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| Project Period (FY) |
2000 – 2002
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| Keywords | Titanium dioxide / Superhydrophilic / Phase change / Contact angle / Boiling and evaporation / UV / Sputtering |
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| Research Abstract |
The purpose of this research project is to develop an enhanced heat transfer surface making use of photo-induced superhydrophilicity of titanium dioxide. This heat transfer surface is expected to have excellent characteristics in liquid-vapor phase change heat transfer process because of extremely high wettability.
We have examined the heat transfer characteristics of TiO_2-coated surfaces by the following experiments;
(1) falling film evaporation around the horizontal cylinder
(2) pool boiling: effect of wettability on critical heat flux (CHF) and minimum heat flux (MHF)
(3) evaporation of water drop on hot surface irradiated by plasma
(4) change in contact angle of plasma-re formed aluminum surface
High wettability of surface enhances heat transfer in above all experiments. In experiment of water drop evaporation, the lifetime of water drop on hot surface decreases as the contact angle of the surface decreases. This indicates that the heat transfer can be enhanced significantly in spray cooling process. In addition, the wetting limit temperature and the Leidenfrost temperature increase by about 20K compared with the normal surface.
The plasma-reformed surfaces have a surface structure of fractal configuration. It initially gives the nature of spreading wetting, but the contact angle gradually increases with time and finally reaches more than 150°, a super-water-repellent state. When the surface is irradiated by plasma at a certain contact angle, the surface returns to spreading wetting state. This phenomenon is unusual and the mechanism has not yet been clear.
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