| Project/Area Number |
08650265
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Thermal engineering
|
|---|
| Research Institution | KYUSHU UNIVERSITY |
|---|
Principal Investigator |
HONDA Hiroshi KYUSHU UNIVERSITY Institute of Advanced Material Study, Professor, 機能物質科学研究所, 教授 (00038580)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
YAMASHIRO Hikaru KYUSHU UNIVERSITY Institute of Advanced Material Study, Research Associate, 機能物質科学研究所, 助手 (70239995)
|
|---|
| Project Period (FY) |
1996 – 1997
|
| Project Status |
Completed (Fiscal Year 1997)
|
| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1997: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1996: ¥1,600,000 (Direct Cost: ¥1,600,000)
|
|---|
| Keywords | Rapid Quenching / Thin Horizontal Wire / Cooling Enhancement / UItrasonic Vibration / Linear Stability Analysis / Vapor film / Minimum-Heat-Flux Points / 急速冷却 / 過冷膜沸騰 / 蒸気膜の安定性 / 伝熱促進 |
|---|
| Research Abstract |
Development of a rapid quenching technique is very important for the production of high performance materials such as amorphous and nano-crystalline alloys. Experiments were conducted to enhance the cooling speed during the quenching process by use of ultrasonic vibration. A thin horizontal platinum wire heated to a high temperature was forced to fall at a constant speed into a coolant bath in which an ultrasonic vibrator was immersed. Water and ethanol were used as test liquids. The effects of the sound pressure and the frequency of ultrasonic vibration on the transient cooling characteristics were studied. The minimum-heat-flux point (MHF point) of film boiling shifted toward a higher wall temperature with increasing sound pressure, and the heat flux after the MHF point was enhanced by more than 200 %. The effect was more significant for water. A theoretical study was conducted to clarify the mechanism of the collapse of vapor film on the cooled body. A linear stability analysis of vapor film in forced convection film boiling on a horizontal cylinder was presented that considered the effects of liquid inertia, vapor viscosily and compressibility, and heat transfer. Unlike the previously proposed theories, this theory could explain the experimental result that the wall superheat at the MHF point increased with increasing liquid subcooling. Experiments were also conducted to clarify the transientheat transfer characteristics during the quenching of a horizontal platinum wire under a natural convection condition. The generated vapor formed beads-like bubbles on the wire that were spaced at a nearly constant distance. A linear stability theory of the vapor film was also developed for this case.
|
