デイフューザ内剥離流域の熱伝達特性の実験的研究 : 第1報 二次元片開きデイフューザの水流実験
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概要
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The purposes of the present investigation are to accumulate the basic data on heat transfer characteristics of the separated flow region in diffusers and also to analize them from the standpoints of conveniences for industrial use. In this 1st report, the experiments are conducted through water flow using a twodimensional unilaterally diverging rectangular diffuser with the dimensions of the throat section 0.04m×0.06m, of the diffuser length 0.90 m and with the variable diverging angle θ from 0 to 10 degree. Reynoldsnumber Reo, defined at the throat, varies from 3×10^4 to 15×10^4. The properinitial point of separation Xi and separation point Xs on the diverging wall are determined independently to the Reo forθ= 6° and θ= 8° respectively, by means of flow visualization method of observing the patterns of hydrogen bubble streak lines. Then the following three types of flow regimes are simultaneously confirmed as a steady flow condition from the throat to the exit successively on the diverging wall. Region- I Region of unseparated flow Region- II Region of intermittent separated flow Region-Ill Region of fully developed separated flow The local heat transfer rates are measured through the heat flux meter method in order to limit the error of local heat flux losses. As the results, the diffuser performances are rather successuful in spite of the apparent separation flow occurrence. Meanwhile the heat transfer rates do not so much decrease in the Region-II and Region-III comparing with the reduction of mean flow velocity caused by expanded channel. Then it is proved that the local Nusselt number of the whole, separated andunseparated, region shoud be directly proportional to the 0.8 power of Reynolds number under constant Prandtl number as like as a correlation of heat transfer for the ordinary fully developed turbulent duct flow. In this connexion, the more practical correlation of heat transfer in the diffuser is proposed as follow h=εh_T where h is the local heat transfer coefficient regardless of flow regimes and h_T is the one formally calculated by the well-known prediction for turbulent duct flow. The present experimental data show that the coefficient ε is unit in the Region- I, on the other hand in the separated flow regions ε is undoubtedly greater than unit. Therefore ε is regarded as the one of the particular parameters representing the heat transfer characteristics of diffuser flow with separation. And h in separated flow regions could be easily predicted if the ε would be given by a generallized form.
- 独立行政法人 海上技術安全研究所の論文
- 1984-05-31
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