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Internal Circulation (internal + circulation)

Distribution by Scientific Domains
Chemistry50%

Selected Abstracts

Axial liquid mixing in high-pressure bubble columns

AICHE JOURNAL, Issue 8 2003
G. Q. Yang
Axial dispersion coefficients of the liquid phase in bubble columns at high pressure are investigated using the thermal dispersion technique. Water and hydrocarbon liquids are used as the liquid phase. The system pressure varies up to 10.3 MPa and the superficial gas velocity varies up to 0.4 cm/s, which covers both the homogeneous bubbling and churn-turbulent flow regimes. Experimental results show that flow regime, system pressure, liquid properties, liquid-phase motion, and column size are the main factors affecting liquid mixing. The axial dispersion coefficient of the liquid phase increases with an increase in gas velocity and decreases with increasing pressure. The effects of gas velocity and pressure on liquid mixing can be explained based on the combined mechanism of global liquid internal circulation and local turbulent fluctuations. The axial liquid dispersion coefficient also increases with increasing liquid velocity due to enhanced liquid-phase turbulence. The scale-up effect on liquid mixing reduces as the pressure increases. [source]

Density currents in shear flows: Effects of rigid lid and cold-pool internal circulation, and application to squall line dynamics

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 579 2002
Ming Xue
Abstract Idealized density current models that contain a rigid lid, developed in previous studies, are evaluated. It is shown, through numerical experiments, that a realistic stable layer placed at the level of the rigid lid acts very much like a rigid lid, in confining the environmental flow to the levels below and in controlling the behaviour of density currents that propagate in the flow. When this stable layer is replaced by a neutrally stable layer, the behaviour of the density current is very different. These results support the hypothesis that in the atmosphere, the tropopause or a tropospheric inversion layer acts much like a rigid lid in the idealized density current models, and the solutions of these models are applicable to organized quasi-two-dimensional convective systems such as squall lines in the atmosphere. The effects of cold-pool internal circulations on density current behaviour are also examined. When a single circulation is present initially inside the cold pool, the direction of circulation that gives rise to a smaller shear across the density interface leads to a smoother interface and a much more steady density current head. Large-amplitude eddies develop along the interface when the direction of circulation is reversed. When two layers of shear are initially present inside the cold pool, the flow pattern inside the cold pool tends to be dominated by the circulation of the lower layer. In this case, the behaviour of the density interface and density current head depends on more than just the initial cross-interface shear. The overall flow pattern in the density current, in which the cold-pool circulation contains rearward flows at the ground level, bears a close similarity to that found in mature squall line systems, as shown by comparisons with a simulated squall line. When the cold pool in a squall line is defined in terms of the equivalent potential temperature, the solutions of idealized density currents in sheared flows become more readily applicable to squall lines. Copyright © 2002 Royal Meteorological Society. [source]

Barium Sulfate Crystallization Kinetics in the Used Quenching Salts Treatment Process

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2004
A. Matynia
Abstract The research results and kinetic studies on the barium ions precipitation process by means of crystalline ammonium sulfate addition are presented. The influence of: barium, sodium, potassium and calcium chlorides concentration in the feeding solution and also the process temperature on barium sulfate mass crystallization kinetics are investigated. Experiments were carried out in the MSMPR crystallizer with internal circulation of suspension. The barium sulfate nucleation and crystal growth rates were estimated from crystal size distribution taking into account a size dependent growth (SDG). Research results may be utilized in the used quenching salts processing technology. [source]

Density currents in shear flows: Effects of rigid lid and cold-pool internal circulation, and application to squall line dynamics

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 579 2002
Ming Xue
Abstract Idealized density current models that contain a rigid lid, developed in previous studies, are evaluated. It is shown, through numerical experiments, that a realistic stable layer placed at the level of the rigid lid acts very much like a rigid lid, in confining the environmental flow to the levels below and in controlling the behaviour of density currents that propagate in the flow. When this stable layer is replaced by a neutrally stable layer, the behaviour of the density current is very different. These results support the hypothesis that in the atmosphere, the tropopause or a tropospheric inversion layer acts much like a rigid lid in the idealized density current models, and the solutions of these models are applicable to organized quasi-two-dimensional convective systems such as squall lines in the atmosphere. The effects of cold-pool internal circulations on density current behaviour are also examined. When a single circulation is present initially inside the cold pool, the direction of circulation that gives rise to a smaller shear across the density interface leads to a smoother interface and a much more steady density current head. Large-amplitude eddies develop along the interface when the direction of circulation is reversed. When two layers of shear are initially present inside the cold pool, the flow pattern inside the cold pool tends to be dominated by the circulation of the lower layer. In this case, the behaviour of the density interface and density current head depends on more than just the initial cross-interface shear. The overall flow pattern in the density current, in which the cold-pool circulation contains rearward flows at the ground level, bears a close similarity to that found in mature squall line systems, as shown by comparisons with a simulated squall line. When the cold pool in a squall line is defined in terms of the equivalent potential temperature, the solutions of idealized density currents in sheared flows become more readily applicable to squall lines. Copyright © 2002 Royal Meteorological Society. [source]