Diffusion Layer Modeling for Condensation With Multicomponent Noncondensable Gases

2000 ◽  
Vol 122 (4) ◽  
pp. 716-720 ◽  
Author(s):  
P. F. Peterson
Keyword(s):  
Boundary Layer ◽  
Diffusion Layer ◽  
Diffusion Coefficients ◽  
Mass Diffusion ◽  
Potential Importance ◽  
Layer Model ◽  
Simple Method ◽  
Simple Diffusion ◽  
Noncondensable Gas ◽  
Noncondensable Gases

Many condensation problems involving noncondensable gases have multiple noncondensable species, for example, air (with nitrogen, oxygen, and other gases); and other problems where light gases like hydrogen may mix with heavier gases like nitrogen. Particularly when the binary mass diffusion coefficients of the noncondensable species are substantially different, the noncondensable species tend to segregate in the condensation boundary layer. This paper presents a fundamental analysis of the mass transport with multiple noncondensable species, identifying a simple method to calculate an effective mass diffusion coefficient that can be used with the simple diffusion layer model. The results are illustrated with quantitative examples to demonstrate the potential importance of multicomponent noncondensable gas effects. [S0022-1481(00)01104-X]

A Generalized Diffusion Layer Model for Condensation of Vapor With Noncondensable Gases

2006 ◽  
Vol 129 (8) ◽  
pp. 988-994 ◽  
Author(s):  
Y. Liao ◽  
K. Vierow
Keyword(s):  
Diffusion Layer ◽  
Mass Diffusion ◽  
Layer Model ◽  
Generalized Model ◽  
Experimental Database ◽  
Molecular Weights ◽  
Noncondensable Gases ◽  
Molar Basis ◽  
The One ◽  
Mass Basis

The diffusion layer model for condensation heat transfer of vapor with noncondensable gases was originally derived on a molar basis and developed from an approximate formulation of mass diffusion, by neglecting the effect of variable vapor–gas mixture molecular weights across the diffusion layer on mass diffusion. This is valid for gases having a molecular weight close to that of the vapor or for low vapor mass transfer rates, but it may cause serious error if a large gradient in the gas concentration exists across the diffusion layer. The analysis herein shows that, from the kinetic theory of gases, Fick’s law of diffusion is more appropriately expressed on a mass basis than on a molar basis. Then a generalized diffusion layer model is derived on a mass basis with an exact formulation of mass diffusion. The generalized model considers the effect of variable mixture molecular weights across the diffusion layer on mass diffusion and fog formation effects on sensible heat. The new model outperforms the one developed by Peterson when comparing with a wide-ranging experimental database. Under certain limiting conditions, the generalized model reduces to the one developed by Peterson.

Application of a boundary-layer model to flow over an eolian dune

1985 ◽  
Vol 90 (D6) ◽  
pp. 10631-10640 ◽  
Author(s):  
John L. Walmsley ◽  
Alan D. Howard
Keyword(s):  
Boundary Layer ◽  
Layer Model ◽  
Boundary Layer Model
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