水平上向き加熱円板まわりに生じる自然対流の流動と伝熱(熱工学,内燃機関,動力など)

概要

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Natural convective flows induced over upward-facing, circular disks were investigated experimentally. The test disks were heated with uniform temperatures and their diameters were varied from 20 to 500mm. The test fluid was air and water at room temperature. The flow fields over heated disks were visualized with dye and smoke. The results showed that the ambient fluid enters the outer edge of the disk and, then, separates three-dimensionally from the surface at certain distance downstream the edge when the Rayleigh numbers exceed certain critical values. The separated flow is gradually distorted and a fully turbulent state is accomplished in the central portion of the disk. It was found that the onset and the pitches of the separation points could be predicted with the Rayleigh numbers. The overall Nusselt numbers of the disks were also measured in the wide range of Rayleigh numbers from 2×10^5 to 3×10^<10>. The numbers are almost identical between air and water. Based on these results, empirical equations for the overall Nusselt numbers were proposed.
社団法人日本機械学会の論文
2007-11-25