| Project/Area Number |
04650178
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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 |
Thermal engineering
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| Research Institution | Yamanashi University |
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Principal Investigator |
ICHIMIYA Koichi Yamanashi University, Faculty of Engineering, Professor, 工学部, 教授 (30037923)
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| Co-Investigator(Kenkyū-buntansha) |
MIYAZAWA Toshiyoshi Yamanashi University, Facuty of Engineering, Research Associate, 工学部, 助手 (90020396)
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| Project Period (FY) |
1992 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1993: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1992: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | Thermal Engineering / Forced Convection / Impinging Jet / Heat Transfer Experiment / Inclined Nozzle / Liquid Crystal / 強制対流 |
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| Research Abstract |
Thermal energy should be saved to the next generation. Offset-type impinging jet is a representative method to improve and augment the local heat transfer or mass transfer. In practical applications, the attitude of the nozzle in comparatively narrow space with confined wall is an important factor including the compactness of the facility.
In 1992, the heat transfer characteristics of an oblique turbulent impinging jet were performed experimetaly by using air as a working fluid. The nozzle diameter was 30 mm and also the distance between the nozzle and the impingement surface 30 mm. The confined wall was set at the same level of the nozzle. The inclined angle was 45ﾟ, 60ﾟ and 90ﾟ. The impingement section was composed of an transparent acrylic plate, the thermosensitive liquid crystal sheet and the stainless steel foil whose thickness was 20 mu m. Three kinds of optical filters were mounted one after another in front of the lens of the CCD camera. The color image of thermosensitive liqui
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d crystal was converted into an electric signal. The size of one pixel was 0.5-1mm square. The relationship between color and temperature was calibrated to determine the accuary and resolution. The scatterd reflected light from the liquid crystal at a given temperature was divided into three components (Red, Green, Blue) of color by optical filters. The brightness of each component was obtained at each pixel as the image data. The temperature was estimated by the regression equation including the relative brightness. The local heat flux was compensated locally by using the detailed temperature distribution and solving the three-dimensional thermal conduction equation in the heated section. According to the results, the local Nusselt number showed the peak shift and the plateau. The effect of the local heat flux is remarkable at low Reynolds number and amounts to 6-17% of uniform flux.
In 1993, the flow characteristics of an oblique turbulent impinging jet were carried out by using a thermoanemometer. The velocity and turbulent intensity across the section were measured in unheated condition. The probe was set against the flow and parallel to the impingement surface. According to the results, the jet from the nozzle rolled down the sorrounding stationary fluid and impinged the flat surface. The rolling down of the flow and the amplification of turbulence near the impingement surface were performed at the minor flow region and promoted the local heat transfer. The gradient of these flow parameters (velocity and fluctuation intensity) seem to affect the local heat transfer enhancement as their absolute vaues do. The superior frequency in power spectrum of velocity fluctuation affecting heat transfer improvement was from 80 to 300 Hz and depended on Reynolds number.
These results will be applied in the practical facility as the basic data. Less
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