2018 Fiscal Year Final Research Report
Elucidation of heat transfer mechanism of pulsating flow in a pipe by quantitative infrared high-speed imaging
| Project/Area Number |
16K06142
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Thermal engineering
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| Research Institution | 防衛大学校(総合教育学群、人文社会科学群、応用科学群、電気情報学群及びシステム工学群) |
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Principal Investigator |
Nakamura Hajime 防衛大学校(総合教育学群、人文社会科学群、応用科学群、電気情報学群及びシステム工学群), システム工学群, 教授 (80531996)
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| Co-Investigator(Kenkyū-buntansha) |
山田 俊輔 防衛大学校(総合教育学群、人文社会科学群、応用科学群、電気情報学群及びシステム工学群), システム工学群, 准教授 (90516220)
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| Research Collaborator |
SHIIBARA Naoki
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| Project Period (FY) |
2016-10-21 – 2019-03-31
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| Keywords | 強制対流 / 伝熱促進 / 脈動流 / 非定常測定 / 赤外線カメラ |
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| Outline of Final Research Achievements |
The heat transfer fluctuation when the pipe flow was accelerated and decelerated was measured quantitatively by infrared high-speed imaging. As a result, it was possible to clearly visualize the laminarization and turbulence phenomena with flow acceleration, and the formation of mottled heat transfer promoting structure and its diffusion phenomena with flow deceleration. Also, by simultaneously measuring the flow fluctuation, it was clarified that the heat transfer fluctuation is delayed with respect to the flow fluctuation, and this delay can be modeled by a combination of the time lag Δt and first-order time constant τ for flow acceleration and deceleration respectively. Furthermore, it was shown that Δt is likely to be formulated by a non-dimensional form using wall friction velocity and kinematic viscosity, and τ is likely to be formulated by a non-dimensional form using wall friction velocity and pipe radius.
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| Free Research Field |
熱工学
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| Academic Significance and Societal Importance of the Research Achievements |
これまで，管内乱流に脈動を与えた場合，どのような条件でどの程度の伝熱が促進（あるいは抑制）されるかについて統一的な見解が得られていなかった．本研究により，流れの加速時・減速時の熱伝達変動を定式化できる見込みが示されたため，任意の管径および流速（レイノルズ数）において，最も伝熱促進（あるいは抑制）される脈動条件（脈動振幅，脈動周期，デューティ比）とその時の伝熱促進率を予測できる可能性が示された．これにより，管内流を用いて熱交換するエネルギー変換機器や，管内流により熱輸送する機器において，流れに脈動を与えた時の熱交換・熱輸送効率向上を予測できる可能性が示された．
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