水平上向き加熱平板上に生じる自然対流の流動と伝熱(プラントル数の影響)(熱工学, 内燃機関, 動力など)

概要

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Natural convective flows over upward-facing horizontal plates were investigated experimentally. The main concerns were focused on the effects of Prandtl numbers on the flow and heat transfer characteristics, in particular, of the laminar and transitional regions. Air and ethylene glycol were utilized as the test fluid and the test plates were heated with uniform heat flux. The flow and temperature fields over the plates were visualized with smoke and liquid crystal sheet to investigate the turbulent transition process. The result showed that three-dimensional separation of main flow becomes a trigger to turbulent transition and that the onset of the separation is described with the modified Rayleigh numbers as (3-4) × 10^6 for both air and ethylene glycol. The local heat transfer coefficients of the plates were also measured and the results were compared with previous results for water. The comparison showed that the coefficients become higher with the Prandtl numbers. Based on these results, empirical heat transfer correlations that account for the Prandtl number effect were proposed.
社団法人日本機械学会の論文
2002-05-25