Numerical investigation of gas transport through micro/nano-scale porous media at slip flow regime için kapak resmi
Numerical investigation of gas transport through micro/nano-scale porous media at slip flow regime
Sabet, Safa, author.
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xii, 90 leaves: charts;+ 1 computer laser optical disc.
Gas flow in micro/nano-scale porous systems is observed in many applications and technologies. Gas dynamics at such small scales differ from conventional fluid dynamics estimations due to rarefaction effects. In the literature, the Knudsen number (Kn) for the characterization of rarefaction effects on permeability is calculated based on a characteristic flow height estimated from the pore size, while the geometric parameters such as pore shape and pore-throat ratios are mostly ignored. Therefore, an accurate characterization of rarefaction effects could not be ascertained. For the first time in literature, a general characterization of gas transport through systems at different porosity and pore throat size values and at different rarefaction levels was obtained using a modified Kn definition. The characteristic height required for an accurate Kn of a porous system is defined using the "equivalent diameter" calculated from the corresponding permeabilities. Pore-level calculations were performed in a wide range of systems while the observed permeability variation by porous parameters was successfully described by an extended volume-averaged model developed as a combination of the Darcy, Kozeny- Carman, and Klinkenberg models. The characterization systematic and volume-averaged model was applied for various cases of (i) two-dimensional porous, (ii) two-dimensional multi- porous, and (iii) three-dimensional complex porous system. For all these systems, the permeability values could be estimated in terms of the geometric parameters of the porous structures and rarefaction levels. In addition, the rarefaction effects on heat convection in metal foams were studied through Darcy to Forchheimer flow regimes using the Kelvin Cell structure. A 60% increase in permeability and a substantial decrease in inertial effects developed due to rarefaction, while Nusselt numbers were found mostly related to Reynolds number. Further, the influence of variation in gas thermophysical properties coupled with rarefaction as a function of increasing gas temperature for high heat flux applications was described. A 40% decrease in hydraulic conductivity for a temperature increase from 300K to 400K is observed, independent from the Kn number. Keywords: Apparent gas permeability; Rarefaction; Pore connectivity effects; Velocity slip; Equivalent Knudsen number.
Yazar Ek Girişi:
Tek Biçim Eser Adı:
Thesis (Doctoral)--İzmir Institute of Technology: Mechanical Engineering.

İzmir Institute of Technology: Mechanical Engineering--Thesis (Doctoral).
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Durumu/İade Tarihi
Tez T002410 TA418.9.P6 S115 2021

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