442 Heterogenous flow of settling slurries
Heterogenous flow conditions exist when most of the particles are supported by the fluid and the contact load between settled solids on the pipe wall is negligible. The particles are suspended only when the average velocity is high. At high fluid velocities the particles can be distributed more or less uniformly across the pipe cross-section and the slurry behaves as a homogenous fluid. Between the condition of fully stratified flow that was described in the previous section and homogeneous...
431 Flow regime boundaries
The boundaries of the flow regimes are defined in a self-consistent manner by noting that any two regimes are contiguous at their common boundary and therefore each of the two correlation equations must be satisfied simultaneously. For example, the boundary between the sliding bed regime Regime 0 and the saltation regime Regime 1 must lie along the solution locus of the equation 1213 c0'7389 w7717 cQ-0'4054 Fr-1096 107'1 C1'018 f 046 CQ-0'4213 Fr-1'354 4'21 Fr _ S _ 1 4679 C1'083 W'064 CO0'0616...
263 Derating of pumps when handling slurries
The simple theory for the pump characteristic curve that is described in the previous section shows that the head developed by a centrifugal pump, measured as head of the fluid being pumped, is independent of the fluid density. This is convenient in practice because the same characteristic curve can be used for fluids of different densities. However, when the pump must transport a slurry, the presence of the solid particles has a significant effect on the performance of the pump. The...
514 Shearthinning fluids with Newtonian limit
Some shear-thinning fluids exhibit Newtonian behavior at high strain rates. The rheological properties of these fluids can be modeled using provided that n lt 1 which shows that the fluid exhibits Newtonian behavior at very high strain rates. This is commonly referred to as the Sisko model. Typical data measured using slurries of fine Ti02 are shown in Figure 5.3. The shear stress calculated using equation 5.10 is shown as a series of solid Figure 5.3 Measured shear stress-rate of strain...
321 Settling velocity of an isolated spherical particle
When the particle is spherical, the geometrical terms in equation 3.10 can be written in terms of the particle diameter and the drag coefficient of a spherical particle at terminal settling velocity is given by The particle Reynolds number at terminal settling velocity is given by It is not possible to solve equation 3.11 directly because Cd is a iunction oi both and the particle size dp through the relationship shown in Figure 3.2 or that given by either oi the Abraham or Turton-Levenspiel...
Re3 D3
The velocity, V, is related to the flow rate and the pipe diameter by and substituting this in equation 2.24 Q can be calculated without requiring the pipe diameter or the average velocity to be known. The use of Q for practical problem solving is described in the following illustrative example. Calculate the diameter of a smooth pipe that would transport 0.01178 m3 s of water under a pressure gradient of 180.0 Pa m see Figure 2.8 . Figure 2.8 Data input screen to calculate friction factor for...
32 Terminal settling velocity
If a particle falls under gravity through a viscous fluid it will accelerate for a short while but as the particle moves faster the drag force exerted by the fluid increases until the drag force is just equal to the net gravitational force less the buoyancy that arises from the immersion of the particle in the fluid. When these forces are in balance the particle does not accelerate any further and it continues to fall at a constant velocity. This condition is known as terminal settling. The...