Development of Numerical Experimental Model for Heat Transfer in High Quality Region of Flow Boiling in Tube Evaporator with Twisted Tape-Insert
| Project/Area Number |
10650216
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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 | KYUSHU UNIVERSITY |
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Principal Investigator |
YOSHIDA Keisuke Kyushu Univ., Grad. Sch. of Eng., Associate Professor, 大学院・工学研究科, 助教授 (60191582)
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| Co-Investigator(Kenkyū-buntansha) |
TAKATA Yasuyuki Kyushu Univ., Grad. Sch. of Eng. Associate Professor, 大学院・工学研究科, 助教授 (70171444)
MORI Hideo Kyushu Univ., Grad. Sch. of Eng. Associate Professor, 大学院・工学研究科, 助教授 (70150505)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 1999: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1998: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Keywords | Twisted Tape-Insert / Heat Transfer Enhancement / Flow Boiling / Tube Evaporator / High Quality Region / Post-Dryout Region / Droplets / Numerical Simulation / 管内沸騰 / 高クオリティ域熱伝達 / ポストドライアウト / 液滴熱伝達 / 電熱促進 |
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| Research Abstract |
This research aimed to develop a numerical experimental mode which can simulates behavior of droplets in the post-dryout region of flow boiling in tube evaporator, in order to find the way to the heat transfer enhancement in this region effectively by twisted tape-insert, which contributes to reducing the tube length required. The research was performed by experimental studies on heat transfer and critical heat flux(CHF)of the flow boiling, and by numerical analysis using computer.
In the experiments data for refrigerant HFC134a were obtained for the horizontal flow conditions (mass flux 100-600 kg/mィイD12ィエD1s). The following results were clarified : (1)The heat transfer characteristics and the relation between CHF and the critical quality for a smooth tube(O. D. 7mm, I. D. 6.34mm)showed the similar tendencies to the results which had been obtained previously for the different flow conditions and refrigerants by the investigators. (2)Magnitude of the heat transfer enhancement by the twi
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sted tape inserted into the smooth tube in the post-dryout region agreed qualitatively with the experimental results which had been obtained for refrigerant CHF113 by the head investigator.
In the numerical analysis a simulation of behavior of a single droplet in vapor flow which collides with heated wall was carried out by the modified VOF method which is taking account of phase change at the vapor-liquid interface. The results showed that the calculation could simulate behavior of the droplet until it collided with the wall, and the definition of temperature of the cell which included the interface affected the complexity of calculation beyond the investigators' expectation. However the most relevant condition at which the droplet departs form the wall has not been found.
In addition, a simple method using Thermo-Paint(temperature sensing paint), which changes its color with temperature, was proposed to measure the surface temperature profile outside the tube, and was confirmed its usefulness by another experiment. Less
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Report
(3 results)
Research Products
(15 results)
