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Transport in Porous Media

, Volume 25, Issue 3, pp 335–350 | Cite as

Effects of serial and parallel pore nonuniformities: Results from two models of the porous structure

  • Lars Nilsson
  • Stig Stenström
Article

Abstract

The effects of parallel-type and serial-type pore nonuniformities on the effective diffusivity and the permeability of a porous material were evaluated, constant porosity and constant specific surface area being assumed. Two structural models were considered. In the first model, the porous structure was described as a bundle of cylindrical capillaries penetrating the whole thickness of the material and in the other it was described instead as a collection of randomly distributed obstacles hindering transport. Both models predicted that parallel-type pore nonuniformities produce an increase in permeability compared with uniform structures having the same porosity and specific surface area. Both models also predicted that the increase in permeability due to parallel-type pore nonuniformities would be larger than the increase in effective diffusivity. Regarding serial-type pore nonuniformities, both models predicted a decrease in permeability and that this decrease would be greater than the decrease in effective diffusivity. The predicted changes in effective diffusivity due to nonuniformities of the sample differed for the two structural models.

Key words

Cauchy-Schwarz-Bunjakovskij inequality computational fluid dynamics effective diffusivity permeability pore-size distribution specific surface area 

Notation

A

a, m2

C

Concentration, mol/m3

D

Diffusivity, m2/s

J

Molar diffusion flux, mol/m2/s

K

Permeability, m2

L

Material thickness, m

n

Number based pore size distribution

N

Molar diffusion flow, mol/s

P

Pressure, Pa

Q

Volumetric flow rate, m3/s

R

Pore radius, m

v

Flow velocity, m/s

V

Volumetric pore size distribution, m3 pores

φ

Volume fraction of solid

τ

Tortuosity

μ

Viscosity, Pas

Subscripts

av

Average

e

Effective

g

Gas-phase

max

Maximum pore radius

min

Minimum pore radius

ref

Structures without nonuniformities

s

Pore surface

surf

Material surface opposing the macroscopic transport direction

z

In the z-direction

Superscripts

α

Quantity given per volume of solid material, /m3 solid

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Copyright information

© Kluwer Academic Publishers 1996

Authors and Affiliations

  • Lars Nilsson
    • 1
  • Stig Stenström
    • 1
  1. 1.Department of Chemical Engineering IUniversity of LundLundSweden

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