1988 Fiscal Year Final Research Report Summary
Research on the Enhancement of Heat/Mass Transfer due to Periodical Impingement of Eddies
| Project/Area Number |
62550699
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
化学工学
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| Research Institution | Kobe University |
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Principal Investigator |
KATAOKA Kunio Kobe University, Faculty of Engineering (Professor), 工学部, 教授 (20031081)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Large-scale Turbulent Eddy / Impinging Jet Heat Transfer / Heat Transfer Enhancement / Surface Renewal Model / Coherent Turbulent Structure / 淀み線伝熱係数 |
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| Research Abstract |
The objective of this project is to elucidate the mechanism for enhancement of the heat/mass transfer in impinging flows and to obtain a physical model useful for the development of heat transfer augmentation technology. The effect of large-scale turbulent eddies on heat transfer enhancement was experimentally studied in both axisymmetric and two-dimensional jets.
It has been found that the heat/mass transfer in impinging jets is unsteady in nature and that the mechanism for enhancement is controlled by the surface renewal effect of large-scale turbulent eddies impinging quasi-periodically on heat transfer surfaces. It has been found that not only the arrival velocity and its turbulence intensity (velocity scale) but also the characteristic frequency (time scale) are predominant parameters. The characteristic frequency for surface renewal effect was determined by a statistical analysis with conditional sampling applied to time-traces of arrival velocity.
Based on these results, the second-phase investigation was also made on the enhancement effect of cylindrical obstacles inserted into approaching jet streams. It has been found that it is possible at short nozzle-to-plate distances to enhance the jet impingement heat transfer and to control its distribution by making use of the wake flows behind cylinders which produce effectively large-scale turbulent eddies.
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