Page 329 - Applied Process Design for Chemical and Petrochemical Plants Volume I

300 Applied Process Design for Chemical and Petrochemical Plants

Figure 5-11. Pumping number is the basis for design procedures involving blending and motion. By permission, Hicks, R. W., et. a/., Chem.
Eng., Apr. 26, 1976, p. 104 [28].

Di = impeller diameter, in. Representative CF values from [ 281 are:
p’ = fluid viscosity, centipoise
p = fluid viscosity, lb/sec ft
p = fluid density, lb/cu ft NRe CF. in.
Sg = fluid specific gravity, (not density) 700 1 .o
N, = power no. 400 0.98
200 0.95
The Froude number is [33]: 100 0.91
70 0.89
60 0.88
DN
N,, = - (5 - 9) 50 0.87
g

g = gravitational constant, 32-ft/sec-sec In general, below a Reynolds number of 50, all
impellers give viscous flow mixing; between 50 and 1,000
the pattern is in the transition range; and from NRe above
Estimated turbine impeller diameter [ 281 : 1000 the action is turbulent.

DT = 394 [ (Hp)/(n S, Nm3] (5-10) For NRc S 10, the liquid motion moves with the
impeller, and off from the impeller, the fluid is stagnant
[34]. The Froude number accounts for the force ofgravi-
Calculate Reynolds number, NRe, from Equation 5-8,
then correct for viscosity effects. ty when it has a part in determining the motion of the
fluid. The Froude numbers must be equal in scale-up sit-
uations for the new design to have similar flow when grav-
(5-11) ity controls the motion [16].
Dcor’ = DT CF