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Regime Map (regime + map)

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Chemistry100%

Selected Abstracts

Rewetting effects and droplet motion on partially wetted powder surfaces

AICHE JOURNAL, Issue 6 2009
Karen P. Hapgood
Abstract In high shear mixer granulation, the powder is agitated in a vessel while liquid is sprayed onto the powder. Formation of "nuclei" can be predicted using a nucleation regime map. However, this approach assumes that only dry powder enters the spray zone. Industrial granulation processes commonly add 20,50 wt % fluid, and the partially wetted powder recirculates many times through the spray zone. The effect of partially wetted powder re-entering the spray zone is not currently known. To investigate, droplets were added to a powder bed at controlled separation distances and time intervals. A strong correlation between drop penetration time and droplet motion on the powder bed surface was observed. For fast penetrating systems, nucleation was only slightly affected by the presence of the previous droplet. However, systems with long penetration times showed lateral droplet motion due to Laplace pressure differences. Implications for the nucleation regime map are discussed. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Fluid flow in an impacting symmetrical tee junction II: two-phase air/water flow

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009
A. P. Doherty
Abstract A universal flow regime map was presented for two-phase flow in a horizontal pipe. Data were given on two-phase gas/liquid flow in a symmetrical impacting tee junction. The flow regimes in the inlet arm of the tee were those expected for a straight pipe. This was not so for the outlet arm where, in most cases, flow regimes occurred earlier than expected. At low liquid outlet flows the stratified regime was reinforced into higher gas flows than expected. The liquid hold-up exhibited variations over the tee junction. The pressure drop in the inlet arm agreed with similar data for the straight pipe, but in the tee outlets was below that expected for the straight pipe. The tee junction pressure drop showed some parallels to the corresponding single-phase flow data but the le/d dimensionless values for the junction pressure drop showed a wide variation, in contrast to the single-phase junction data. A model was presented based on the Lockhard,Martinelli theory that enabled the tee pressure drop to be predicted. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Two-phase bifurcated dividing pipe flow

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2009
A. Murphy
Abstract Data are reported on the pressure drop of co-current air,water two-phase flow through 0.0454 m i.d. bifurcations with included angles of 60°, 90°, 120° and 180°. The pressure changes on account of the angles at the junctions depended on the superficial phase velocities and the angle of bifurcation. For the 60° lowest angle of bifurcation the pressure drop was insensitive to flow rates if the superficial liquid velocity was in the lower range at and below 0.1 m s,1. For higher liquid flows the pressure loss increased dramatically, particularly in the annular-type regimes. When the angle at the junction was increased, negative values of pressure loss, i.e. an increase in pressure was recorded across the bifurcation in the gas velocity region under 10 m s,1 and liquid rates at and above 0.1 m s,1 in the slug and blow-through slug regimes. The effect coincided with liquid separation from the inner inlet pipe wall of the junction and its subsequent reformation on the downstream walls. A second less dramatic increase in junction pressure drop occurred at the lowest liquid flow rate of 0.05 m s,1 for the tee (180° bifurcation) that was due both to the smooth transition of liquid through the junction and the damping of surface waves in stratified-type flow. A flow regime map was presented for the tee junction. The inlet flow showed agreement with the map but the flow regimes found in the outlet arms of the junction tended to form earlier than expected being triggered by the pressure disturbances in the passage through the bifurcation. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Liquid-Liquid Stratified Flow through Horizontal Conduits

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 8 2005
T. Sunder Raj
Abstract The stratified configuration is one of the basic and most important distributions during two phase flow through horizontal pipes. A number of studies have been carried out to understand gas-liquid stratified flows. However, not much is known regarding the simultaneous flow of two immiscible liquids. There is no guarantee that the information available for gas-liquid cases can be extended to liquid-liquid flows. Therefore, the present work attempts a detailed investigation of liquid-liquid stratified flow through horizontal conduits. Gas-liquid flow exhibits either smooth or wavy stratified orientations, while liquid-liquid flow exhibits other distinct stratified patterns like three layer flow, oil dispersed in water, and water flow, etc. Due to this, regime maps and transition equations available for predicting the regimes in gas-liquid flow cannot be extended for liquid-liquid cases by merely substituting phase physical properties in the equations. Further efforts have been made to estimate the in-situ liquid holdup from experiments and theory. The analysis considers the pronounced effect of surface tension, and attempts to modify the Taitel-Dukler model to account for the curved interface observed in these cases. The curved interface model of Brauner has been validated with experimental data from the present work and those reported in literature. It gives a better prediction of liquid holdup in oil-water flows and reduces to the Taitel-Dukler model for air-water systems. [source]