Method for obtaining the Knudsen diffusion coefficient

Hibi, Yoshihiko

doi:10.1016/j.mex.2018.08.005

Cited by 2 publications

(1 citation statement)

References 11 publications

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“…It is important to note that the revised diffusion coefficient in the near-field region is different from the Knudsen diffusion coefficient used in porous materials. This is because the analysis presented in this study is not based on the elastic collision assumption, which assumes all the collisions between molecules and solid interfaces are elastic, used to derive the Knudsen diffusion coefficient [16][17][18]. The effectiveness of the modified Fick's law in the equilibrium state is validated by comparing the partial pressure distributions of binary mixtures predicted by the Direct Simulation Monte Carlo (DSMC) method [19] and modified Fick's law.…”

Section: Introductionmentioning

confidence: 99%

Transport phenomena in the near-field region of Stefen flow

Xiong,

Cao

2023

Phys. Scr.

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Stefan flow is a transport phenomenon concerning the movement of one component of a multi-component mixture that is induced by the production or removal of the component at an interface. Fick’s law is often used to describe the transport phenomena in many physical and chemical processes. However, when the system scales down to the order of molecular mean free path, the influence of interface that is not considered in Fick’s law, cannot be neglected. To predict the transport phenomena in the near-field region, the Herz-Knudsen (HK) relation is often adopted, in which the near-field region controlled by the HK relation was assumed as a zero-thickness layer. Our theoretical analysis has shown that this assumption is less physically realistic. In this study, we derive the thickness of the near-field region through the analysis of the theoretical binary diffusion coefficient and corresponding mass flux. Based on the analysis, we propose a modified Fick’s law to describe the far-field and near-field regions separately. The validity of this modified Fick’s law and its difference from Fick’s law coupled with the HK relation are demonstrated by comparing the partial pressure distributions of binary mixtures, predicted by the two versions of Fick’s law and the Direct Simulation Monte Carlo (DSMC) method, due to the deposition of one component on a cold surface. The comparison results show that the modified Fick’s law outperforms the Fick’s law coupled with the HK relation in accuracy at high deposition coefficients for H2O/N2 mixture and in stability within the range of this study. Moreover, the situations when the modified Fick’s law is required are discussed. This study provides a more molecular-level insight into the transport phenomena in the near-field region of Stefen flow.

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Section: Introductionmentioning

confidence: 99%

Transport phenomena in the near-field region of Stefen flow

Xiong,

Cao

2023

Phys. Scr.

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Kinetic fitting of methane adsorption rate and its influencing factors

Yu¹

2023

IJE

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In order to reveal the mechanism of the influence of coal matrix pores on methane adsorption rate, based on the high-pressure methane isothermal adsorption experiment of coal samples with different pore structures, the desorption law of methane in coal and its internal relationship with pore structure were studied by analyzing the change of methane adsorption amount at a single pressure point over time. Bangham kinetic model was used to fit the adsorption process, and constants representing the adsorption rate were obtained. The following understandings were obtained: (1) With the decrease of particle size, the adsorption equilibrium time is shorter, small particle size samples often have more complex pore structure, which makes the adsorption reaction between gas-solid interface more active, but the particle size itself cannot increase or reduce the size of the accumulated adsorption amount at the equilibrium, it only changes the length of time required to reach the adsorption equilibrium. (2) With the increase of the mesh number, the adsorption rate also increases, but the higher the coal rank, the greater the adsorption rate growth rate.

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Method for obtaining the Knudsen diffusion coefficient

Abstract: Graphical abstract

Cited by 2 publications

References 11 publications

Transport phenomena in the near-field region of Stefen flow

Transport phenomena in the near-field region of Stefen flow

Kinetic fitting of methane adsorption rate and its influencing factors

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