固体粒子と流体の密度が等しい円管内固液混相流の流動と熱伝達 [in Japanese] Flow and Heat Transfer in Two-Phase Flow of Neutrally Buoyant Particles and Liquid [in Japanese]
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固体粒子と管の直径比が大きい固液混相流の圧力損失, 熱伝達および管内の粒子数密度分布について実験的に調べた.固体粒子としては流体と密度が等しい球状粒子を用いた.まず, 流動状態を可視化して管内の粒子分布を調べた結果, レイノルズ数が小さく, 粒子の体積流量率が小さいときに, いわゆるpinch効果が確認された.レイノルズ数の増加とともにpinch効果は崩れ, 管内の粒子分布は管断面全域に及ぶ.さらにpinch効果が起こる条件では, 粒子の平衡体置はレイノルズ数の増加とともに管壁に近付き, 粒子と管の直径比の増加とともに管軸に近付くことがわかった.混相流とそれと同流量の単相流の摩擦係数の比はレイノルズ数の増加とともに緩やかに増加し, あるレイノルズ数を超えると急激に増加する.また摩擦係数の比は粒子体積流量率の増加とともに増加し, 粒子と管の直径比の増加とともに減少する。混相流と単相流の熱伝達係数の比も摩擦係数と同様の傾向を示す.
The pressure drop and heat transfer of solid-liquid two-phase flow, in which the ratio of diameter of solid particles to that of a pipe is large, were investigated experimentally. The solid particles used were spherical particles whose density is close to that of the liquid. Measurements were made on friction factor, heat transfer coefficient on the pipe wall, and on number density of particle distribution in thepipe. The result of visualization of flow indicates that the particles stay at an equilibrium position forsmaller Reynolds numbers and smaller concentration of particles. The equilibrium position of particles approaches closer to the pipe wall for larger flow rates, and closer to the pipe axis for smaller pipe diameters. The ratio of the friction factor of two-phase flow to that of Poiseuille flow increases gradually with increasing Reynolds number in the region of low Reynolds number, and increases steeply in the region of high Reynolds number. The ratio of friction factors increases with increasing fraction of the volumetric flow rate of the particles, and decreases with increasing ratio of diameter of the particles to that of the pipe. The ratio of heat transfer coefficient of two-phase flow to that of Poiseuille flow has same tendency as the friction factor.
- Chemical engineering
Chemical engineering 24(6), 958-965, 1998-11-20
The Society of Chemical Engineers, Japan