Tsutao Otake

Coalescence and breakup of bubbles in liquids

Abstract Coalescence and breakup in a swarm of bubbles were directly observed by using the high speed cinematography. It was designed so that three dimensional motion of bubbles could be continually followed. Influence of operating conditions and liquid properties on the frequencies of bubble passing, coalescence and breakup was examined. It was seen that there was the critical distance at which the leading bubble began to exert an noticeable influence on, the following one. The distance was about 3- to 4-fold diameter of the leading bubble. Coalescence was found to take place when more than about a half of the projected area of the following bubble was overlapped with that of the leading bubble at the critical distance. On the contrary, breakup occurred in the case of the overlapping less than about a half of the projected area of the following bubble. The increment of the following bubble velocity induced by the leading one was empirically correlated with the bubble distance and the angle between the straight line joining the centers of bubbles and the vertical axis. The Reynolds numbers had no appreciable effect on the velocity increment within the range examined.

FLUID AND PARTICLE MOTION IN TURBULENT DISPERSION--1. MEASUREMENT OF TURBULENCE OF LIQUID BY CONTINUAL PURSUIT OF TRACER PARTICLE MOTION

A method is proposed for measurement of turbulence quantities of fluid flow. The motion of a swarm of small tracer particles supplied to turbulent flow is continually followed by high-speed cine-photography, from which velocity correlations and energy spectra are evaluated. It is applicable to the heterogeneous fluid flow as well as to the homogeneous fluid flow, and the Eulerian and Lagrangian correlations are determinate simultaneously. Validity of the method is confirmed by the comparison of some turbulence quantities in the present study with those obtained otherwise.

Fluid and particle motion in turbulent dispersion—II: Influence of turbulence of liquid on the motion of suspended particles

Abstract A study is made of the relative motion of particles to fluid in a turbulent dispersion. An equation is derived to describe the motion of particles. Motions of both fluid and particles are recorded continually by motion picture method, followed by Fourier-analyses. Even neutral-buoyant particles are found to be able to respond to the motion of turbulent eddies of fluid larger in linear scale than the order of their diameters. When density difference is not admissible, some reduction in the turbulence component velocity appears apparently, as expected in the derivastion of the basic equation.

Fluid and particle motion in turbulent dispersion-III: Particle-liquid hydrodynamics and mass-transfer in turbulent dispersion

Abstract An attempt is made to make clear the correlation of particle-liquid hydrodynamics and mass-transfer mechanism in a turbulent dispersion where particles are freely-suspended in turbulent liquid. This is based on the fundamental information on the particle-liquid relative velocity, especially in the range of higher wave number of turbulence component velocity. It is finally found that relative motion of particle to liquid alone can explain the experimentally observed behavior of mass-transfer coefficient.

Optimal operation of a catalytic tubular reactor with fouling catalyst by coke deposition

Abstract The dehydrogenation of isopentane over chromia-alumina catalyst has been carried out at three isothermal levels. The catalyst fouling and the deposited coke profiles were observed in a catalytic tubular reactor. A kinetic model is proposed and the kinetic parameters have been estimated by non linear regression methods. For the dehydrogenation with catalyst fouling, the problem of finding the isothermal optimal control was formulated by a distributed maximum principle and a computational algorithm using a quasi-steady state assumption was presented. The dehydrogenation of isopentane was carried out experimentally at the evaluated isothermal optimal temperature. The observed conversion, yields and coke content profiles agreed with the evaluated ones fairly well, which suggests that the kinetic model may be useful for optimal controls.

Permeation of aromatic compounds in aqueous solutions through thin, dense cellulose acetate membranes

Abstract The partition and diffusion coefficients of aqueous solutions of aromatic compounds through a thin, dense cellulose acetate membrane were measured at 20°C. The water content and the thickness of the prepared membranes varied from 0.121 to 0.610 by volume fraction and from 17 to 88 μm, respectively. The aromatic solutes used were phenol, aniline, hydroquinone and p -chlorophenol. The solute concentration ranged between 9.0 x 10 -5 and 1.0 x 10 -3 mol/l. The partition coefficients had the following order: p -chlorophenol, phenol, aniline, hydroquinone; they were experimentally correlated with the water content of the swollen membranes. The dependence of the diffusion coefficients on the water content of the membrane was examined using as basis a pore model and a free volume model, respectively. The diffusion coefficients were adequately correlated with the water content of the membrane according to the relation given by the free volume model.

Separation of aromatic substances from aqueous solutions using a reverse osmosis technique with thin, dense cellulose acetate membranes

Abstract Investigations were made of the water flux rate and rejection characteristics of aromatic substances in aqueous solutions using a thin, dense cellulose acetate membrane in reverse osmosis experiments. The aromatic substances used were phenol, aniline, hydroquinone and p -chlorophenol. The permeate became more enriched in aromatic compounds as compared to the feed solution as the water content of the membrane increased. By considering both the effects of pressure on the chemical potential of a component and the contribution of viscous flow to the overall transport of that component in the hydrated membrane, a theoretical relationship was developed to predict the negative solute rejection of the membrane. Based on this proposed theory, the permeability coefficients of water and organic solute were estimated from experimental solute rejection data, including negative values. The permeability coefficients of components were in good agreement with previously established correlations in measurements of partition and diffusion coefficients.

Characteristics of Solids Flow through Feed Pipe in Stirred-Moving and Fluidized Beds

多段櫂形羽根による撹拌式移動層並びに流動いて, 供給管の粒子流速が空気流量, 羽根回転速度, 粒子層満などの操作条件に対して測定された。撹拌式移動層における実測結果は, 管口における粒子波面の周期的運動によって影響される粒子流動モデルを適用して整理された。撹拌式流動層において, 管口での上昇気泡によって惹起される粒子流速の変化を考慮して, 新しい流動モデルが提出された。このモチルに基づいて上昇気泡の頻度と径の関係が得られ, 粒子流速の実験値式操作条件が相関された。

Dynamico of a Mukiplate Gas-liquid Reactor

多段気液反応装置の動特性を検討するため, 総括反応速度および装置流動特性のプロセス変量依存性を同時に考慮して転達関数を求めた。実験的に求めた反応装置動特性と, 実験に伴う非線型性の効果を考慮して, この伝達関数から模擬した装置動特性とは, ほぼ一致する。また先に報告したこの種の装量に対する効果的な制御系の設計方法は, 本報告で求めた伝達関数により, その動特性を表わせる反応装置に対しても適用できる。

Kinetic Study of Gas-Liquid Reaction using Continuous Stirred Tank Reactor with Known Interfacial Area

定常吸収理論が適用できるように, 流通式自由表面撹拌槽を用いて, 酢酸第2水銀 (50%酢酸水溶液) によるエチレンの反応吸収実験を行なった。そして, 溶解ガスの液境膜内での反応量が無視される実験条件を明らかにし, この条件下のデータを用いて反応速度を解析した。さらに, 流通操作における正味総括反応速度と操作因子との関係を検討するため正味反応係数φを定義し, これを用いて実験データを整理した。