Page 20 - Separation process principles 2

xxiv Nomenclature

NLu Luikov number = l/NLe vapor pressure in a pore
N,, mininum number of stages for specified split adsorbate vapor pressure at test conditions I
NNu Nusselt number = dhlk = temperature gradi- partial pressure 1
ent at wall or interfacettemperature gradient partial pressure in equilibrium with liquid at its
across fluid (d = characteristic length) bulk concentration
Noc number of overall gas-phase transfer units material-balance parameters for Thomas algo-
defined in Table 6.7 rithm in Chapter 10
Nor. number of overall liquid-phase transfer units rate of heat transfer; volume of liquid; volu-
defined in Table 6.7 metric flow rate
rate of heat transfer from condenser
Npe Peclet number for heat transfer = NReNPr =
convective transport to molecular transfer volumetric liquid flow rate
Peclet number for mass transfer = = convec- volumetric flow rate of mother liquor
tive transport to molecular transfer
rate of heat transfer to reboiler
Np, Power number defined in (8-21) area parameter for functional group k in
Np, Prandtl number = momentum UNIFAC method
diffusivitytthermal diffusivity relative surface area of a molecule in
UNIQUAC and UNIFAC equations; heat flux;
NR number of redundant equations
loading or concentration of adsorbate on ad-
NR~ Reynolds number inertial force/ viscous force sorbent; feed condition in distillation defined
(d = characteristic length) as the ratio of increase in liquid molar flow
rate across feed stage to molar feed rate
NRX number of reactions
volume-average adsorbate loading defined for
Nsc Schmidt number momentum diffusivitytmass
a spherical particle by (15-103)
diffusivity
surface excess in liquid adsorption
Ns~ Sherwood number concentration gradient at
wall or interface/concentration gradient across liquid flow rate across a tray
fluid (d = characteristic length) universal gas constant:
Nst Stanton number for heat transfer = h/GCp 1.987 caYmol K or Btunbmol
8315 Jlkmol K or Pa m3/kmol K
Stanton number for mass transfer
82.06 atm cm3/mol K
NTU number of transfer units 0.7302 atm ft3nbmol R
10.73 psia ft3nbmol R;
NT total number of crystals per unit volume of
mother liquor; number of transfer units for heat molecule radius; amount or flow rate of raffinate;
transfer ratio of solvent to insoluble solids; reflux ratio;
drying-rate flux; inverted binary mass-transfer
N, number of equilibrium (theoretical) stages coefficients defined by (12-31) and (12-32)
Nv number of variables drying-rate per unit mass of bone-dry solid
Nwe Weber number defined by (8-37) drying-rate flux in the constant-rate period
number of moles drying-rate flux in the falling-rate period
volume parameter for functional group k in
n molar flow rate; moles; constant in Freundlich
equation; number of pores per cross-sectional UNIFAC method
area of membrane; number of crystals per unit liquid-phase withdrawal factor in (10-80)
size per unit volume minimum reflux ratio for specified split
n, number of crystals per unit volume of mother particle radius
liquor
vapor-rate withdrawal factor in (10-81)
no initial value for number of crystals per unit size relative number of segments per molecule in
per unit volume UNIQUAC and UNIFAC equations; radius;
ratio of permeate to feed pressure for a mem-
n+, n- valences of cation and anion, respectively
brane; distance in direction of diffusion; reac-
P pressure; power; electrical power
tion rate; fraction of a stream exiting a stage
P, P difference points that is removed as a sidestream; molar rate of
mass transfer per unit volume of packed bed
parachor; number of phases in Gibbs phase rule
radius at reaction interface 1
PC critical pressure
hydraulic radius = flow cross sectionlwetted
PM permeability perimeter
i
permeance pore radius 1
P, reduced pressure, PIP, radius at surface of particle 1
vapor pressure radius at tube wall I