Topic
Knudsen number
About: Knudsen number is a research topic. Over the lifetime, 5052 publications have been published within this topic receiving 104278 citations.
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TL;DR: In this article, the effect of pore poisoning, resulting in a m pore blockage, was analyzed using 2-D network models of connecting arms for a multiple pore length scale coating layer.
Abstract: m coatings is analyzed using 2-D network models of connecting arms anderified experi- mentally for a multiple pore length scale coating layer. The network model includes ( effects ofariation in the lattice randomness Voronoi tessellation in the form of Delau- )( ) nay lattice triangulation , pore coordination number, pore size Knudsen effect , and : pore-size distribution on the predicted D. The effect of pore poisoning, resulting in a m pore blockage, is analyzed. Correlations for the porosity and pore-blockage dependency : () of D , as well as relationships for the pore size low-dimensionality and multiple m pore length scale effects, are also discussed. An experiment performed on a catalytic () conerter washcoat segment represented by three pore length scales placed on an oth- erwise impermeable wall of an electrochemical sensor shows a good agreement with the : predicted D based on a multiple pore length scale medium with parallel diffusion m paths.
131 citations
TL;DR: In this article, the dynamical attractors associated with anisotropic hydrodynamics (aHydro) and the DNMR equations for a $0+1\mathrm{d}$ conformal system using kinetic theory in the relaxation time approximation were determined.
Abstract: We determine the dynamical attractors associated with anisotropic hydrodynamics (aHydro) and the DNMR equations for a $0+1\mathrm{d}$ conformal system using kinetic theory in the relaxation time approximation. We compare our results to the nonequilibrium attractor obtained from the exact solution of the $0+1\mathrm{d}$ conformal Boltzmann equation, the Navier-Stokes theory, and the second-order Mueller-Israel-Stewart theory. We demonstrate that the aHydro attractor equation resums an infinite number of terms in the inverse Reynolds number. The resulting resummed aHydro attractor possesses a positive longitudinal-to-transverse pressure ratio and is virtually indistinguishable from the exact attractor. This suggests that an optimized hydrodynamic treatment of kinetic theory involves a resummation not only in gradients (Knudsen number) but also in the inverse Reynolds number. We also demonstrate that the DNMR result provides a better approximation of the exact kinetic theory attractor than the Mueller-Israel-Stewart theory. Finally, we introduce a new method for obtaining approximate aHydro equations which relies solely on an expansion in the inverse Reynolds number. We then carry this expansion out to the third order, and compare these third-order results to the exact kinetic theory solution.
130 citations
TL;DR: In this article, an integral-moment method of solution for arbitrary values of the Knudsen number is employed to solve the problem of the drag and thermal polarization of a spherical particle in a low-speed flow of a rarefied gas.
Abstract: Kinetic theory for the drag and thermal polarization of a spherical particle in a low-speed flow of a rarefied gas is presented. The problem is solved on the basis of the linearized kinetic equation (Shakhov 1974) with the correct Prandtl number, , for monatomic gas. The integral-moment method of solution for arbitrary values of the Knudsen number is employed. The possibility of arbitrary energy, and tangential and normal momentum accommodation of gas molecules on the particle surface is taken into account in the boundary condition. The particle–gas heat conductivity ratio Λ is assumed to be arbitrary.Numerical results for the isothermal drag, radiometric force affecting a non-uniformly heated particle in a rarefied gas, and temperature drop between the ends of the particle diameter owing to its thermal polarization in a gas flow have been obtained. The analytical expressions approximating the numerical calculations for the whole range of Knudsen numbers are given. The results obtained are compared to the available theoretical and experimental data.
129 citations
TL;DR: In this article, the evaporation of InP under Knudsen and Langmuir conditions was investigated mass-spectrometrically using a modulated molecular beam technique combined with phase-sensitive detection and signal averaging to separate evaporating species from background species in the vacuum system.
Abstract: The evaporation of InP under Knudsen and Langmuir conditions has been investigated mass-spectrometrically using a modulated molecular beam technique combined with phase-sensitive detection and signal averaging to separate evaporating species from background species in the vacuum system. P2 was found to be the dominant species over InP under Knudsen conditions but significant evaporation fluxes of In and P4 were also detected. The P4 flux was attributed to P2+P2 association on the oven walls. A congruent evaporation point under these conditions was predicted at 629±5 K. Under Langmuir evaporation conditions the only evaporating species detected were In and P2. Up to 638±5 K the (100) surface evaporated congruently but above this temperature there was a disproportionate loss of P2 from the surface. The equilibrium vapour pressures of In, P2 and P4 over InP and of In over pure In are presented and enthalpies for the reactions InP(s)->In(s)+½P2 (g); 2P2 (g)->P4(g); In (s)-> In (g) calculated.
129 citations
TL;DR: In this article, the authors present a derivation of the governing equations for multi-component convective-diffusive flow in capillaries and porous solids starting from a well-defined model and clear assumptions.
129 citations