scholarly journals A simple modelling of mass diffusion effects on condensation with noncondensable gases for the CATHARE Code

1995 ◽  
Author(s):  
P Coste ◽  
D Bestion
Keyword(s):  
Mass Diffusion ◽  
Noncondensable Gases ◽  
Diffusion Effects

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]

scholarly journals Heat Transfer and Mass Diffusion in Nanofluids over a Moving Permeable Convective Surface

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Muhammad Qasim ◽  
Ilyas Khan ◽  
Sharidan Shafie
Keyword(s):  
Heat Transfer ◽  
Differential Equations ◽  
Previous Analysis ◽  
Mass Diffusion ◽  
Nonlinear Ordinary Differential Equations ◽  
Constant Mass ◽  
Convective Boundary ◽  
Shooting Technique ◽  
Diffusion Effects ◽  
Solution Velocity

Heat transfer and mass diffusion in nanofluid over a permeable moving surface are investigated. The surface exhibits convective boundary conditions and constant mass diffusion. Effects of Brownian motion and thermophoresis are considered. The resulting partial differential equations are reduced into coupled nonlinear ordinary differential equations using suitable transformations. Shooting technique is implemented for the numerical solution. Velocity, temperature, and concentration profiles are analyzed for different key parameters entering into the problem. Performed comparative study shows an excellent agreement with the previous analysis.

Advanced Modeling of Multicomponent Vaporization/Condensation Phenomena for a Reactor Safety Analysis Code SIMMER-III

2002 ◽  
Author(s):  
Koji Morita ◽  
Tatsuya Matsumoto ◽  
Ryo Akasaka ◽  
Kenji Fukuda ◽  
Tohru Suzuki ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Phase Transition ◽  
Reactor Core ◽  
Safety Analysis ◽  
Mass Diffusion ◽  
Short Time Scale ◽  
Reactor Safety ◽  
Noncondensable Gases ◽  
Diffusion Limited ◽  
Multicomponent Flows

It is believed that the numerical simulation of thermal-hydraulic phenomena of multiphase, multicomponent flows in a reactor core is essential to investigate core disruptive accidents (CDAs) of liquid-metal fast reactors. A new multicomponent vaporization/condensation (V/C) model was developed to provide a generalized model for a fast reactor safety analysis code SIMMER-III, which analyzes relatively short-time-scale phenomena relevant to accident sequences of CDAs. The model characterizes the V/C process associated with phase transition through heat-transfer and mass-diffusion limited models to follow the time evolution of the rector core under CDA conditions. The heat-transfer limited model describes the nonequilibrium phase-transition processes occurring at interfaces, while the mass-diffusion limited model is employed to represent effects of noncondensable gases and multicomponent mixture on V/C processes. Verification of the model and method employed in the multicomponent V/C model of SIMMER-III was performed successfully by analyzing two series of condensation experiments.

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.

Burgers fluid flow in perspective of Buongiorno’s model with improved heat and mass flux theory for stretching cylinder

2020 ◽  
Vol 92 (3) ◽  
pp. 31101
Author(s):  
Zahoor Iqbal ◽  
Masood Khan ◽  
Awais Ahmed
Keyword(s):  
Diffusion Process ◽  
Mathematical Formulation ◽  
Thermal Relaxation ◽  
Mass Diffusion ◽  
Stretching Cylinder ◽  
Discussion Section ◽  
Buongiorno’S Model ◽  
Homotopy Analysis ◽  
Burgers Fluid ◽  
Diffusion Phenomena

In this study, an effort is made to model the thermal conduction and mass diffusion phenomena in perspective of Buongiorno’s model and Cattaneo-Christov theory for 2D flow of magnetized Burgers nanofluid due to stretching cylinder. Moreover, the impacts of Joule heating and heat source are also included to investigate the heat flow mechanism. Additionally, mass diffusion process in flow of nanofluid is examined by employing the influence of chemical reaction. Mathematical modelling of momentum, heat and mass diffusion equations is carried out in mathematical formulation section of the manuscript. Homotopy analysis method (HAM) in Wolfram Mathematica is utilized to analyze the effects of physical dimensionless constants on flow, temperature and solutal distributions of Burgers nanofluid. Graphical results are depicted and physically justified in results and discussion section. At the end of the manuscript the section of closing remarks is also included to highlight the main findings of this study. It is revealed that an escalation in thermal relaxation time constant leads to ascend the temperature curves of nanofluid. Additionally, depreciation is assessed in mass diffusion process due to escalating amount of thermophoretic force constant.

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