Velocity transport

Here again an equation is estabUshed (2) to describe the trajectory of a particle under the combined effect of the Hquid transport velocity acting in the x-direction and the centrifugal settling velocity in thejy-direction. Equation 13 determines the minimum particle size which originates from a position on the outer radius, and the midpoint of the space, between two adjacent disks, and just reaches the upper disk at the inner radius, r. Particles of this size initially located above the midpoint of space a are all collected on the underside of the upper disk those particles initially located below the midpoint escape capture. This condition defines the throughput, for which a 50% recovery of the entering particles is achieved. That is,... 

Linear transport velocity of the material is almost proportional to the product of frequency and stroke for these conveyors. However, the transport velocity and the depth that can be obtained with a specific material is dependent on the handling characteristics of that material. Manufacturers have accumulated data banks relating material characteristics to attainable conveying velocities for their proprietary conveyor designs. 

The most important transition velocity, often regarded as the minimum transport or conveying velocity for settling slurries, is V 9- The Durand equation (Durand, Minnesota Int. Hydraulics Conf., Proc., 89, Int. Assoc, for Hydraulic Research [1953] Durand and Condohos, Proc. Colloq. On the Hyd. Tran.spoti of Solids in Pipes, Not. Cool Boord [UK], Paper IV, 39-35 [1952]) gives the minimum transport velocity as... 

Typical minimum transport velocities are given in Table 12.13 and capture velocities for various applications in Table 12.12. 

Estimation of Transportation Velocity of Solid Particles in Pipe Flow at Various Inclination Angles 1335... 

Transport velocity The air velocity required in an extract duct conveying dust to ensure that the particulate matter remains in suspension and does not settle. 

It can be shown that for a reservoir in steady state. To is equal to t, i.e. the turnover time is equal to the average residence time spent in the reservoir by individual particles (Eriksson, 1971 Bolin and Rodhe, 1973). This may seem to be a trivial result but it is actually of great significance. For example, if tq can be estimated from budget considerations by comparing fluxes and burdens in Equation (1) and if the average transport velocity (V) within the reservoir is known, the average distance (L = Vxr) over which the transport takes place in the reservoir can be estimated. 

Time scales of transport can also be applied to situations when no well-defined reservoirs can be defined. If the dominant transport process is advection by mean flow or sedimentation by gravity, the time scale characterizing the transport between two places is simply tadv = L/V where L is the distance and V the transport velocity. Given a t)q)ical wind speed of 20 m/s in the mid-latitude tropospheric westerlies, the time of transport around the globe would be about 2 weeks. 

Whatever the type of ventilation, air flow must be adequate to prevent particulate matter settling in the ducting typical transport velocities are given in Table 11.10. 

Material, operation or industry Minimum transport velocity (m/s) (ft/min) ... 

Equation (A9) accounts for the change in the amount of daughter within the solid while Equation (A 10) accounts for that in the fluid. The transfer of the nuclide from the solid to the fluid phase is governed by the first term on the right side of both equations. Note that in this formulation, as given in Spiegelman and Elliott (1993), the time of melt transport is accounted for and depends on the physically based transport velocity. Like Equation (A8), both equations can be solved simultaneously by numerical integration or more sophisticated numerical method. 

---