1998 Fiscal Year Final Research Report Summary
Study on Mechanism to Avoid Cooling-Instability for Thermo-Mechanical Control Process
| Project/Area Number |
09650254
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Thermal engineering
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| Research Institution | Kogakuin University |
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Principal Investigator |
MIYASHITA Tohru Kogakuin University, Faculty of Engineering, Lecturer, 工学部, 講師 (00100371)
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| Co-Investigator(Kenkyū-buntansha) |
OHTAKE Hiroyasu Kogakuin University, Faculty of Engineering, Lecturer, 工学部, 講師 (40255609)
KOIZUMI Yasuo Kogakuin University, Faculty of Engineering, Professor, 工学部, 教授 (20215156)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Mechanical Engineering / Thermal Engineering / Boiling / Heat Transfer / Collapse of Vapor-Film in Film Boiling / Minimum-Heat-Flux Temperature / Thermodynamic Limit of Superheat / Contact Angle |
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| Research Abstract |
The technology of Thermo-Mechanical Control Process (TMCP) is advanced to produce steel with high quality and low cost on saving energy. The aim of the study is examined the mechanism to avoid cooling-instability for TMCP caused it to add oxide, focusing on thermal engineering, i.e., boiling heat-transfer.
First, Propagative collapse of a vapor film in film boiling was investigated experimentally with a horizontal platinum-wire for subcooled water at atmospheric pressure. The propagation velocity of collapse front and the surface temperature at the collapse were measured by changing the temperature of the local low-temperature-spot at both edges of the test wire. The experimental results showed that the propagation velocity decreased and the surface temperature at the collapse increased with decreasing the local temperature. The propagation velocities of the collapse of the vapor film were represented well by the heat-conduction model. This fact supports that the temperature of the rewetting front is lower than the thermodynamic limit of superheat when the vapor film of the film boiling collapses.
Second, the behavior of wetting on pool film-boiling, focusing on observations of a collapse of a vapor-film and a contact angle was investigated experimentally. The experiments, used a platinum wire with 2 mm diameter, were performed for saturated water at atmospheric pressure. In the experiments, a liquid jet from a nozzle was supplied on the superheated surface in the stable film-boiling, then the behavior of liquid-solid contact was observed. The experimental results showed that the propagative collapse of the vapor film occurred when the wall superheat was below 334 K for the top-jet case. The temperature was related to the thermodynamic limit of superheat, according to the heat conduction model. The angles between the liquid-vapor interfacial line and the heated wall were close to the dynamic advancing contact-angles in room temperature.
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