Die Annäherung der Temperaturabhängigkeit der Transportkoeffizienten von Gasen durch einen Potenzansatz

Abstract

Nach den von Hirschfelder angegebenen Formeln wurden die Selbstdiffusionskoeffizienten, die Zähigkeit und die Wärmeleitfähigkeit einiger Gase und die binären Diffusionskoeffizienten von Gaspaaren zwischen 0 °C und 1000 °C berechnet und durch einen Potenzansatz approximiert. Die hierbei erhaltenen Parameter werden angegeben und die auftretenden Fehler diskutiert.

Roles of Surface/Volume Diffusion in the Growth Kinetics of Elementary Spiral Steps on Ice Basal Faces Grown from Water Vapor

“…In contrast, in the case of volume diffusion, diffusion of water vapor molecules is much faster than that of water admolecules on a basal face, although surface diffusion coefficient of water admolecules is still not determined experimentally. From the volume diffusion coefficient ( D V = 2.22 × 10 –5 m 2 /s) and mean free path (66 nm) , of water vapor molecules in nitrogen gas at atmospheric pressure, speed of a water vapor molecule is estimated to be 336 m/s. This value is much faster than V step shown in Figure .…”

“…From the viewpoint of the volume diffusion of water vapor molecules to a crystal surface, the normal growth rate V basal of a basal face is proportional to the net flux of vapor into the surface. Hence, V basal can be expressed as follows: , V basal = D̃ V ( ∂ P H 2 O ∂ n ) surf = D̃ V P H 2 O ∞ − P H 2 O surf δ D̃ normalV = normalΩ k normalB T sample D normalV Here, D̃ V is the parameter defined by eq , ( ∂P H 2 O / ∂n ) surf is the normal derivative of the water vapor distribution at a position on the surface, Ω is the volume occupied by one water molecule in an ice crystal (3.25 × 10 –29 m 3 ), k B is the Boltzmann constant (1.381 × 10 –23 J/K), T sample is the absolute temperature of the sample ice crystals (264.8 K), and D V is the volume diffusion coefficient (2.22 × 10 –5 m 2 /s) of water vapor molecules at 0.1 MPa and at 273.2 K. The thickness δ of a volume diffusion layer (unknown) is defined by the distance between the crystal surface and the point at which the tangent line of P H 2 O at a surface and the extrapolate line of P H 2 O ∞ are intersected (Figure A): ( ∂ P <...…”

“…Here, D ̃V is the parameter defined by eq 2, (∂P H 2 O /∂n) surf is the normal derivative of the water vapor distribution at a position on the surface, Ω is the volume occupied by one water molecule in an ice crystal (3.25 × 10 −29 m 3 ), 48 k B is the Boltzmann constant (1.381 × 10 −23 J/K), T sample is the absolute temperature of the sample ice crystals (264.8 K), and D V is the volume diffusion coefficient (2.22 × 10 −5 m 2 /s) 39 of water vapor molecules at 0.1 MPa and at 273.2 K. The thickness δ of a volume diffusion layer (unknown) is defined by the distance between the crystal surface and the point at which the tangent line of P H 2 O at a surface and the extrapolate line of…”