ディフューザ内剥離流域の熱伝達特性の実験的研究 : 第2報,二次元片開きディフューザの空気流実験
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概要
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In this 2nd report, the experiments are conducted through the two-dimensional unilater-ally diverging diffuser of the dimensions of the throat width b_0 = 0.10m, the distance between the paralell walls W = 0.15m and the length L = 1.04m, and the diverging angle θ varies from 0 to 20 degree. The range of the θ is different from the one in the 1st report experiments although the area ratio is settled nearly equal. The air driven by the fan, fully developed turbulent flow, inflows into the diffuser with Reynolds number Reo(DeoUo/v),defined at the throat, ranged from 5×10^4 to 15×10^4, and is exhausted through the outlet duct to the laboratory. The three types of flow regimes, Region- I, -II and -III on the diverging wall are determined mainly by means of flow visualization method using tuft and dry ice mist tracer. The local heat transfer rate on the heated diverging wall is measured under the uniform heat flux condition. According to the velocity profile measurments, it is clarified that the velocity boundary surface, on which u^^- is always zero, lies steadily between the separated flow on the diverging wall and the diffuser main flow. Contrary to the velocity profile performance at u^^- = 0 position, it is proved that there is no appreciable boundary of the temperature distribution,because the most of the temperature difference between the heating surface and the main flow is given only at the very near to the heated diverging wall. Therefore, even though of double deck structure of the stream, the over-all heat transfer could be managed only by heat exchange between the separated flow and the diverging heated wall. Heat transfer characteristics are afresh proved to be expressed by the following formula h=εh_T h_T is the basic heat transfer coefficient defined by the fully developed turbulent duct flow in the imaginary straight duct at the diffuser section. Coefficient ε, independent to Reynolds number, is greater than unit in the separated flow region but approximately unit in the unseparated one. The ε is shown, from the present data, strikingly to depend upon area ratio AR, and so could be provided as follow. ε=f(AR) However compairing with the 1st report results, ε is presumed still more to be a function of pressure recovery coefficient Cp and diverging angle θ. ε=f(AR,Cp,θ) It is therefore resulted that ε would be regarded as being closely connected to diffuser performance.The investigation on these functions would be a further problem in the future.
- 独立行政法人 海上技術安全研究所の論文
- 1985-05-30
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