Abstract
The present work describes the mass transfer process between a moving fluid and a slightly soluble cylinder, with the axis perpendicular to flow direction, buried in a packed bed of small inert particles, with uniform voidage. Fluid flow in the packed bed around the cylinder was assumed to follow Darcy’s law and, at each point, dispersion of solute was assumed to be determined by radial and axial dispersion coefficients, in the cross-stream and streamwise directions, respectively. Numerical solutions of the differential equation describing solute mass conservation were undertaken to obtain the concentration field near the soluble surface and the mass transfer flux was integrated to give the Sherwood number as a function of the relevant parameters. Mathematical expressions are proposed that describes accurately the dependence found numerically between the value of the Sherwood number and the values of Peclet number, Schmidt number and the ratio between the diameter of cylinder and the diameter of inerts.
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Abbreviations
- A :
-
dimensionless parameter (defined in Eq. 8a)
- B :
-
dimensionless parameter (defined in Eq. 8b)
- c :
-
solute concentration
- c 0 :
-
bulk concentration of solute
- c*:
-
equilibrium concentration of solute
- C :
-
dimensionless solute concentration
- d :
-
diameter of inert particles
- d c :
-
diameter of soluble cylinder
- D L :
-
longitudinal (axial) dispersion coefficient
- D m :
-
molecular diffusion coefficient
- D′m :
-
effective molecular diffusion coefficient (=D m/τ)
- D T :
-
transverse (radial) dispersion coefficient
- K :
-
permeability in Darcy’s law
- k :
-
mass transfer coefficient
- L :
-
length of soluble cylinder
- n :
-
mass transfer rate
- P :
-
pressure
- Pe L (∞):
-
asymptotic value of Pe L when Re p → ∞
- Pe T (∞):
-
asymptotic value of Pe T when Re p → ∞
- R :
-
radius of soluble cylinder
- ℜ:
-
dimensionless spherical radial co-ordinate
- r :
-
spherical radial coordinate (distance to the centre of the soluble cylinder)
- u :
-
absolute value of interstitial velocity
- U :
-
interstitial velocity (vector)
- u 0 :
-
absolute value of interstitial velocity far way from cylinder
- u r , u θ :
-
components of fluid interstitial velocity
- ɛ:
-
bed voidage
- Φ:
-
dimensionless potential function
- ϕ:
-
potential function
- η:
-
enhancement factor due to convective dispersion
- μ:
-
dynamic viscosity
- θ:
-
spherical angular coordinate
- ρ:
-
density
- τ:
-
tortuosity
- Ψ:
-
dimensionless stream function
- ψ:
-
stream function
- Pe′:
-
Peclet number based on diameter of soluble cylinder (=u 0 d c/D′m)
- Pe′p :
-
Peclet number based on diameter of inert particles (=u 0 d/D′m)
- Re p :
-
Reynolds number (=ρ u 0 d/μ)
- Sc :
-
Schmidt number (=μ /ρ D m)
- Sh′:
-
Sherwood number (=kd c/D′m)
- Sh′md :
-
Sherwood number when D T≅ D L ≅ D′m (i.e. Pe′p< 0.2)
- i, j :
-
grid node indices (see Fig. 2)
- n :
-
iteration number
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Delgado, J.M.P.Q. Mass transfer and dispersion around an active cylinder in cross flow and buried in a packed bed. Heat Mass Transfer 42, 1119–1128 (2006). https://doi.org/10.1007/s00231-005-0076-4
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DOI: https://doi.org/10.1007/s00231-005-0076-4