Axial liquid velocity

When the radial distances from the rotational axis of a centrifuge to the liquid surface and the bowl wall are /q and respectively, the axial liquid velocity u (m s" ) is given by... 

Dimensionless component of axial liquid velocity, wIV oo Component of true axial liquid velocity, m/s Average linear velocity of the gas phase, m/s Average linear velocity of the liquid phase, m/s Coordinate... 

In a pioneering investigation, Serizawa [127, 128] measured the lateral void distribution as well as the turbulent axial liquid velocity fluctuations for bubbly air/water up-flows in a vertical pipe of diameter 60 (mm) inner diameter. They used electrical resistivity probes to measure the local void fraction, the bubble impaction rate, the bubble velocity and its spectrum. Turbulence quantities, such as the liquid phase mean velocity, and the axial turbulent fluctuations were measured using a hotfilm anemometer. A supplementary... 

Bove et al [15] specified an outlet pressure boundary instead, and the axial liquid velocity components were determined in accordance with a global mass balance. This approach is strictly only valid when the changes in liquid density due to interfacial mass transfer or temperature changes are negligible, as the local changes are not known a priori. 

In the case of slurry flow in a rotary drum, turbulent suspension of the solids can occur due to the axial liquid velocity coupled with the radial liquid velocity due to the drum rotation and mixing action created by the drum internals. Typically, the peripheral drum velocity is much higher than the slurry axial velocity, and, consequently, the drum rotational speed becomes very important for solids turbulent suspension and, hence, transport. 

Figure 23 Pressure effects on the profiles of (a) axial liquid velocity (b) Reynolds axial normal stress in a bubble column (Pc = 5.08 cm, nitrogen water). (From Lee et al., 2001.)...

The final formula for the axial liquid velocity is written as... 

Clearly, there is a need for complete mapping of liquid and gas velocities and turbulence intensities in bubble columns. Until recently only data of Hills (1974) reported liquid time averaged velocities and radial gas holdup profiles taken under identical operating conditions. Yao et al. (1990) present in addition to such data also gas velocity and turbulence intensity profiles. Some data on radial holdup distribution and axial liquid velocity in industrial size columns were presented by Kojima et al. (1980) and Koideetal. (1979). 

Along most of the column, except in the vicinity of the distributor and at the free liquid surface, liquid recirculation can be described by a single axial liquid velocity profile. The inversion point is around 0.7 of the dimensionless column radius. 

Modeling of Bubble Column Reactors Axial liquid velocity... 

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