Page 248 - gas transport in porous media

CHAPTER 14

EXPERIMENTAL DETERMINATION OF TRANSPORT
PARAMETERS

OLGA ŠOLCOVÁ AND PETR SCHNEIDER
Institute of Chemical Process Fundamentals, Czech Academy of Science, Rozvojová 135, 165 02 Praha
6, Czech Republic

Any prediction or simulation of gas transport in porous solids is based on mass
balances. The balance equations incorporate inevitably constitutive equations, which
relate the intensity of mass flux to mass flux driving forces. Constitutive equations
comprise information of three kinds:
1. Properties of components of the gas mixture: bulk diffusion coefficients of all pairs
of components of the gas mixture, component viscosities and their mean speeds.
Such properties are, usually, readily available.
2. The physical laws, which describe the gas transport, with idealized units of
the porous medium. Usually, cylindrical capillaries are utilized because of the
availability and simplicity of the laws.
3. Characteristics of the porous medium. Since the diverse complicated nature of the
porous medium is usually unknown it must be modeled. Modeling of the porous
structure is based on units from paragraph 2 and accounts for pore-size distribu-
tion and other factors not apprehended by pore units. Today two basic models are
available for description of combined (diffusion and permeation) transport of mul-
ticomponent gas mixtures: the Mean Transport-Pore Model (MTPM) (Fott et al.,
1983; Schneider and Gelbin, 1984) and the Dusty Gas Model (DGM) (Jackson,
1977; Mason and Malinauskas, 1983).
Mean Transport-Pore Model (MTPM) assumes that the decisive part of the gas
transport takes place in transport-pores that are visualized as cylindrical capillaries
with radii distributed around the mean value r (first model parameter). The width of
this distribution is characterized by the mean value of the squared transport-pore radii,
2
r (second model parameter). The third model parameter is the ratio of porosity, ε t ,
(Schneider, 1978; Novák et al., 1988).
and tortuosity of transport-pores, q t , ψ = ε t/q t

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C. Ho and S. Webb (eds.), Gas Transport in Porous Media, 245–272.
© 2006 Springer.