Ryotaro Izumi

Experimental studies of enhancement of forced-convection heat transfer by adding injection flow.

対流熱伝達の促進を図ることを目的として, 水平平板上に形成された層流境界層内にスリットから吹き出し流を付加し, 熱伝達率および壁面摩擦係数に及ぼす吹出しの効果を実験的に検討した.実験はレイノルズ数Re=u∞・l/ν=3.0×104～6.4×105, 吹出し比F=ρ0υ0/ρ∞u∞=0.005～0.1の範囲で測定した.この結果, 熱伝達率および摩擦係数はスリット後の全領域にわたって吹出し効果によって上昇し, 乱流への遷移を早める.また, 吹出し比の変化によって, これらの特性値も変化するため, 特性の制御が可能となり, 一定の熱伝達促進しかもたらさないタービュレンス・プロモータにくらべて有利である.ポンプ動力一定の条件下で伝熱面性能を評価するとき, スタントン数の最大増加比St/St0はF=0.1で1.39倍, F=0.05で1.29倍である.

Fluid flow and heat transfer in plate-fin and tube heat exchanger. Analysis of fluid flow around square cylinder situated between parallel plates.

プレートフィンチューブ形熱交換器の基本的な構造モデルを、プレートフィンとしての平行平板の間にチューブとしての正方形柱を垂直に設置した流路と考え、その流動および熱伝達を解明する。本報では、レイノルズ数Re=200の場合の流動の解析を行い、速度ベクトル、流跡線、等圧線、壁面におけるせん断応力の分布およびはく離線を明示し、また流れの非定常性について考察を加え、流路内の流動機構について詳細な検討を行う。

Characteristics of Turbulent Flow and Mass Transfer in Divergent Channels of Rectangular Section

The characteristics of turbulent flow and mass transfer in divergent channels of rectangular cross-section were experinlentally investigated and the typical effects of main flow and the secondary flow on mass transfer were discussed. Sherwood number Shx, could be suitably expressed by Reynolds number Rex, and acceleration parameter K. Sherwood numbers Shx, in the entrance region of mass concentration were proportional to Rex, 0.83 for every diver-gent angle in the present experiment. The velocity profiles in the upper region were recognized as a composite structure consisting of those for the inner and outer layers. but it was difficult to predict the velocity profiles in the lower region with the plane jet profile.

A STUDY ON OPPOSED GASEOUS JET FLAMES STABILIZED IN A UNIFORM AIRSTREAM : 4TH REPORT : EXTINCTION MECHANISM OF OPPOSED GASEOUS JET FLAMES

As a final stage of this study the extinction mechanism is treated qualitatively on the basis of preceeding results. It is found that the partial extinction in the frontal flame zone can be explained with the relation between the first Damkohler number and the maximum temperature on the axis, and that this mechanism is similar to that of laminar opposed diffusion flames. To deal with the overall extinction at the stability limit the excess-reaction variable is found analytically, which has a physical meaning of an overall and average reaction ability of the flame. With this variable and the first Damkohler number three stability curves with different nozzle pressure can be collapsed into a single curve, and the mechanism of extinction at each stability limit can be elucidated independently of the nozzle pressure. It is found that the kind of flame in the stable region depends only on the excess-reaction variable.