Page 371 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Mixing of Liquids 339

Qg = gpm DT = Diameter of single pitch blade turbine, under tur-
u' = viscosity, cp bulent conditions, in.
Dcor = Impeller diameter for turbulent regime, corrected
For a laminar static mixer: for viscosity effect, in.
D, = Diffusivity, sq ft/sec
d = Tube outside diameter, ft
(5-88) d' = Pipe inside diameter, ft
d. = Tube diameter, O.D., ft
For 6P (total), multiply (6PL) (no. modules) F = Force (fluid) on turbine, perpendicular to shaft,
ML/t 2
Fr = Froude number
For turbulent Dow: NRe > 2000 f = function of _
gc = Acceleration of gravity, 32.2 ft/ (sec) (sec)
6P O for open pipe, and f = Re vs f chart (Fluid Flow, Chapter g = Gravitational conversional factor, 32.2 lb mass-
2) for pipe ft/ (lb force) (sec) (sec)
H = Total potential head during flow, ft of liquid
6P = 0.0135 [(f)(L)(Sg)(Qgf /D'5] (5-89) HP = Motor, horsepower
1
0
HP = Impeller horsepower used by the system, ft lbs/sec,
or HP
(5-90) h = Film coefficient of heat transfer, kettle liquid to
jacket wall or to coil, Btu/ (hr) (sq ft) (°F)
6P = open pipe pressure drop IC = Clearance of impeller off tank bottom, in., Figure
6P, = static mixer pressure drop in turbulent flow, psi 5-34, equal to impeller (turbine) diameter, or IC =
D; sometimes IC = % D is suggested
K = Absorption coefficient
For fluid velocities > 2.5 fps, and when lower volume
fraction to be mixed is greater than 25% of total flow, use K 1 = Proportionality constant, a function of the impeller
shape, = 0.4 for three blade propeller in waler,
a dual turbulent module, i.e., AP, would be 2x for one Equation 5-1
module. K 2 = Correlating factor for viscous flow power, Table 5-1
The static mixer is also useful for direct contact heat K3 = Mixing factors, turbulent flow power, Table 5-1
transfer between fluids, two phase contacting, and other k = Viscosity correction factor for turbulent flow (static
mixer)
useful applications such as mass transfer. or, k = Thermal conductivity of heat transfer fluid (liquid),
For final design details and selection of mixer ele- BlT/ (hr) (ft (°F /ft)
2)
ments, refer directly to the manufacturers, as each design k' = Proportionality constant depending upon system,
is different and may not perform like a competitor's. for blending
kw = Thermal conductivity heat transfer wall, Btu/ (hr)
(sq ft) (°F /ft)
Nomenclature k1 = Liquid film mass transfer coefficient (lb moles) (cu
fl) I (sec) (sq ft) (lb mole)
A = Heat transfer area, referenced to inside, i, or out- L = Static mixer length, in., or length of pipe in ft
side, o, sq ft I,, = Thickness of heat transfer wall, ft
1•
An = Area of outside coil or heat transfer barrier, sq ft/ft M* = Mass flow rate, lb/hr
1\ = Area of inside surface for heat transfer, such as m = Function of fluid properties, such as µ, k and cp
coils, flat surfaces, or other barrier, sq fl/ft N, = Shaft speed of rotation, revolutions per second
Aavg = Average of inside and outside tube surface area, Ne = Newton number, depends on design
sq fl/ft Nr = Force number, consistent units, dimensionless =
2
a = Constant in Froude number exponent equation F/(PN D 4)
a = Constant in power number equation, Figure 5-13 N = Nm = Impeller speed of rotation, rpm
B = Number of vertical wall baffles P 0 =NP= Power number, dimensionless
b = Constant in power number equation, Figure 5-13 Np, = Prandl number (heat transfer)
b = Constant in Froude number exponent equation N 0 = Flow number
b = Distance baffle off flat vessel bottom, Figure 5-34 NR; = Reynolds number, dimensionless
ba = Baffle clearance off tank bottom, Figure 5-34 Nu = Nusselt number, (heat transfer)
bw = Baffle width, in., see Figure 5-34. N3 = Correlating factor for turbulent flow power
c, cP = Specific heat Btu/(lb) (°F) Nwc = 'Weber number
cp = Viscosity, ceruipoise n = Exponent in scale-up equation, describing
cl = Distance baffles off wall, Figure 5-34 type/degree of mixing required, Figure 5-32, or
CF = Correction factor for Reynolds number for viscosity number of samples in statistics
effects or, n = Number of impellers
D; = Impeller diameter, in. nb = Number of tube baffles (vertical)
D = Impeller diameter, ft or L, Figure 5-34 P = Power input to impeller, ft-lb/sec (see Equation 5-19)
D' = inside diameter of pipe, in. or if in a ratio can be as horsepower
0 = Diameter of jet from propeller mixer al origin, ft P1,p = P'= Power, horsepower used by impeller mixing system
0