Effect of Aspect Ratio on Mixed Convection Heat Transfer from the Heated Bottom Wall in Horizontal Rectangular Channel

  • Miura Kazuya
    Department of Chemistry and Chemical Engineering, Yamagata University
  • Tokanai Hideki
    Department of Chemistry and Chemical Engineering, Yamagata University

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  • 底面加熱水平矩形流路内の複合対流熱伝達におよぼす流路断面縦横比の影響
  • テイメン カネツ スイヘイ クケイ リュウロ ナイ ノ フクゴウ タイリュウ ネツ デンタツ ニ オヨボス リュウロ ダンメン ジュウオウヒ ノ エイキョウ

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<p>To clarify the phenomenon of orthogonal mixed convection heat transfer to water in a horizontal rectangular channel, experimental and numerical investigations were performed for channels of different cross-sectional aspect ratios heated from the bottom wall. First, heat transfer for pure forced convection was measured to obtain the basis of mixed convection heat transfer coefficients by using upper-wall heated channels, which can eliminate the buoyancy flow. A correlation equation was then proposed for pure forced convection heat transfer coefficients obtained from both experimental measurements and numerical solutions. Mixed-convection heat transfer was next measured under various conditions of Reynolds number and Grashof number. As a result, heat transfer was enhanced in all measured regions of Reynolds number. In particular, it was found that aspect ratio and Grashof number had little effect on heat transfer coefficients in the region of extremely low Reynolds number. When the Reynolds number increased, the heat transfer coefficients decreased with the decrease in aspect ratio. This tendency became more prominent as the Grashof number decreased. In the turbulent region, the heat transfer coefficients asymptotically approached those of pure forced convection under the given conditions of aspect ratio or Grashof number. The above results were qualitatively explained by the variations in temperature distributions and flow patterns of the cross-sectional channel obtained from the numerical analysis.</p>



    KAGAKU KOGAKU RONBUNSHU 47 (5), 132-139, 2021-09-20

    The Society of Chemical Engineers, Japan


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