Thermodiffusion in a Binary Fluid Mixture Subject to External Vibrations: Effect of Variable Physical Properties

2011 ◽  
Author(s):  
A. Parsa ◽  
M. Z. Saghir
Keyword(s):  
Physical Properties ◽  
Diffusion Coefficients ◽  
Thermal Gradient ◽  
Microgravity Environment ◽  
Fluid Mixture ◽  
Binary Fluid ◽  
Numerical Studies ◽  
External Forces ◽  
And Diffusion ◽  
Different Levels

A microgravity environment is essential for studying the phenomenon of thermodiffusion in order to suppress the microscopic flows in the mixture. It is, however, noted that the residual micro accelerations (g-jitters) in the space laboratories is produced by several sources such as crew activities, mechanical systems, thrusters firing, spacecraft docking, etc. Such external forces lead to significant flows which can induce convection that may affect the accuracy of the experiment. Consequently, an appropriate interpretation of the space experimental results relies on theoretical and numerical studies of the g-jitter effect on the temperature and the concentration fields. In this paper, we have modeled the thermodiffusion experiment subjected to different levels of vibration when the steady gravity is assumed zero. A rectangular cavity that is subjected to a thermal gradient is filled with a binary mixture (water and isopropanol) and put under the influence of different levels of vibrations. The thermal gradient is applied perpendicular to the vibration. All physical properties including density, mass diffusion and thermodiffusion coefficients are assumed variable as function of temperature and concentration using PC-SAFT equation of state. It is found that using variable physical properties including density and diffusion coefficients make the results more realistic in comparison with the constant model especially in cases with higher Rayleigh vibrations.

scholarly journals Influence of Vibration on Diffusion in Liquid Mixtures On-Board the International Space Station

2021 ◽  
Author(s):  
Aram Parsa
Keyword(s):  
Heat Transfer ◽  
Numerical Analysis ◽  
Physical Properties ◽  
International Space Station ◽  
Diffusion Coefficients ◽  
Space Station ◽  
Flow Patterns ◽  
Transport Processes ◽  
International Space ◽  
Different Levels

Experiments on-board the International Space Station experience a convective flow due to the oscillatory g-jitters induced by several sources such as crew activities, mechanical systems, thrusters firing, spacecraft docking, etc. Although g-jitter seems to have a major impact on diffusion-related experiments in Space, very few experimental studies have addressed this topic. This study examined the effect of oscillatory g-jitters on transport processes (fluid flow, heat transfer and mass transfer). Cubic rigid cells filled with water and isopropanol at different concentrations were subjected to thermal gradients and forced vibrations. The cells were exposed to different levels of vibration in terms of frequency and amplitude, which were applied perpendicular to the temperature gradient. The full transient Navier Stokes equations coupled with the mass and heat transfer formulas were solved numerically using the control volume technique. The physical properties of the fluid mixture such as the density were determined using two different models. The effect of different levels of vibration on the flow was analysed and the results were compared in a benchmark study with other scientific groups. The effect of the diffusion coefficients variation and other physical properties on the temperature and concentration distribution was compared to those results obtained with constant diffusion coefficients. Results show that use of variable physical properties in the modelling produces different flow patterns and component concentration. By examining different flow patterns, it was found that the effect of using variable coefficients is much more significant in the cases with high Rayleigh vibration that result in strong flow when compared with numerical analysis using constant variables. The numerical analysis was also performed for the actual experiment on board the International Space Station. The same trend was seen for both the numerical and experimental results. However, the separation of components was higher in the experiment in comparison with the numerical analysis. This was discussed in detail for various scenarios in terms of the applied frequency and amplitude. Recommendations are made according to the findings from this study for the improvement of accuracy in the numerical and experimental analyses of future diffusion experiments in Space.

scholarly journals Influence of Vibration on Diffusion in Liquid Mixtures On-Board the International Space Station

2021 ◽  
Author(s):  
Aram Parsa
Keyword(s):  
Heat Transfer ◽  
Numerical Analysis ◽  
Physical Properties ◽  
International Space Station ◽  
Diffusion Coefficients ◽  
Space Station ◽  
Flow Patterns ◽  
Transport Processes ◽  
International Space ◽  
Different Levels

Experiments on-board the International Space Station experience a convective flow due to the oscillatory g-jitters induced by several sources such as crew activities, mechanical systems, thrusters firing, spacecraft docking, etc. Although g-jitter seems to have a major impact on diffusion-related experiments in Space, very few experimental studies have addressed this topic. This study examined the effect of oscillatory g-jitters on transport processes (fluid flow, heat transfer and mass transfer). Cubic rigid cells filled with water and isopropanol at different concentrations were subjected to thermal gradients and forced vibrations. The cells were exposed to different levels of vibration in terms of frequency and amplitude, which were applied perpendicular to the temperature gradient. The full transient Navier Stokes equations coupled with the mass and heat transfer formulas were solved numerically using the control volume technique. The physical properties of the fluid mixture such as the density were determined using two different models. The effect of different levels of vibration on the flow was analysed and the results were compared in a benchmark study with other scientific groups. The effect of the diffusion coefficients variation and other physical properties on the temperature and concentration distribution was compared to those results obtained with constant diffusion coefficients. Results show that use of variable physical properties in the modelling produces different flow patterns and component concentration. By examining different flow patterns, it was found that the effect of using variable coefficients is much more significant in the cases with high Rayleigh vibration that result in strong flow when compared with numerical analysis using constant variables. The numerical analysis was also performed for the actual experiment on board the International Space Station. The same trend was seen for both the numerical and experimental results. However, the separation of components was higher in the experiment in comparison with the numerical analysis. This was discussed in detail for various scenarios in terms of the applied frequency and amplitude. Recommendations are made according to the findings from this study for the improvement of accuracy in the numerical and experimental analyses of future diffusion experiments in Space.

On some physical properties of six aspen clones

Holzforschung ◽  
2005 ◽  
Vol 59 (1) ◽  
pp. 54-58 ◽  
Author(s):  
Stavros Avramidis ◽  
Shawn D. Mansfield
Keyword(s):  
Physical Properties ◽  
Diffusion Coefficients ◽  
Water Sorption ◽  
Sorption Site ◽  
Site Distribution ◽  
Heat Of Wetting ◽  
Specific Permeability ◽  
Desorption Isotherms ◽  
And Diffusion ◽  
Sorption Characteristics

Abstract Basic physical properties including density, permeability, water sorption characteristics and diffusion coefficients in desorption were measured with specimens taken from for six aspen clone trees harvested in northeastern British Columbia. Results showed that there are significant differences among the clones in their specific permeability and somewhat in the heat of wetting, but very little was found among density, diffusion coefficients and desorption isotherms. These results indicate that the porous structure could be variable among clones whereas the sorption site distribution and availability might not.

Investigations into and optimisation of the performance of sewage detention tanks during storm rainfall events

1999 ◽  
Vol 39 (2) ◽  
pp. 43-52 ◽  
Author(s):  
R. Kowalski ◽  
J. Reuber ◽  
Jürgen Köngeter
Keyword(s):  
Flow Field ◽  
Pollutant Transport ◽  
Cleaning Efficiency ◽  
Rainfall Events ◽  
Transient Phenomena ◽  
Numerical Studies ◽  
Hydraulic Load ◽  
Storm Rainfall ◽  
Different Levels ◽  
Sewage Systems

Combined Sewage Detention Tanks (CSDT) are components of combined sewage systems commonly used in Germany. A lack of knowledge of the processes occurring within these structures causes the engineer to apply conceptual approaches in the simulation of pollutant transport. The investigations presented were implemented in an integrated systematic way. Extensive analytical, experimental and numerical studies of steady and transient phenomena taking place in CSDTs were carried out simulating different levels of hydraulic load. The study of the flow field and the simulation of sedimentation and erosion under realistic conditions resulted in proposals for modification and optimisation of the function of CSDTs. A simple way of predicting the cleaning efficiency is presented.

Critical consolute point in hard-sphere binary mixtures: Effect of the value of the eighth and higher virial coefficients on its location

2010 ◽  
Vol 75 (3) ◽  
pp. 359-369 ◽  
Author(s):  
Mariano López De Haro ◽  
Anatol Malijevský ◽  
Stanislav Labík
Keyword(s):  
Equation Of State ◽  
Binary Mixtures ◽  
Hard Sphere ◽  
Hard Spheres ◽  
Virial Coefficients ◽  
Fluid Mixture ◽  
Binary Fluid ◽  
Virial Series ◽  
Consolute Point ◽  
Critical Constants

Various truncations for the virial series of a binary fluid mixture of additive hard spheres are used to analyze the location of the critical consolute point of this system for different size asymmetries. The effect of uncertainties in the values of the eighth virial coefficients on the resulting critical constants is assessed. It is also shown that a replacement of the exact virial coefficients in lieu of the corresponding coefficients in the virial expansion of the analytical Boublík–Mansoori–Carnahan–Starling–Leland equation of state, which still leads to an analytical equation of state, may lead to a critical consolute point in the system.

PREDICTION OF THE TRANSPORT PROPERTIES OF SF6 WITH O2, CO2, CF4, N2 AND CH4 MIXTURES AT LOW DENSITY BY THE INVERSION METHOD (PART II)

2004 ◽  
Vol 03 (01) ◽  
pp. 69-90 ◽  
Author(s):  
BEHZAD HAGHIGHI ◽  
ALIREZA HASSANI DJAVANMARDI ◽  
MOHAMAD MEHDI PAPARI ◽  
MOHSEN NAJAFI
Keyword(s):  
Potential Energy ◽  
Diffusion Coefficients ◽  
Potential Energy Function ◽  
Model Potential ◽  
Inversion Method ◽  
Low Density ◽  
Initial Model ◽  
Lennard Jones ◽  
Inversion Procedure ◽  
And Diffusion

Viscosity and diffusion coefficients for five equimolar binary gas mixtures of SF 6 with O 2, CO 2, CF 4, N 2 and CH 4 gases are determined from the extended principle of corresponding states of viscosity by the inversion technique. The Lennard–Jones 12-6 (LJ 12-6) potential energy function is used as the initial model potential required by the technique. The obtained interaction potential energies from the inversion procedure reproduce viscosity within 1% and diffusion coefficients within 5%.

scholarly journals Boundary behavior and product-form stationary distributions of jump diffusions in the orthant with state-dependent reflections

2008 ◽  
Vol 40 (02) ◽  
pp. 529-547
Author(s):  
Francisco J. Piera ◽  
Ravi R. Mazumdar ◽  
Fabrice M. Guillemin
Keyword(s):  
Random Fields ◽  
Diffusion Coefficients ◽  
Boundary Behavior ◽  
Stationary Regime ◽  
Product Form ◽  
Local Times ◽  
Nonnegative Orthant ◽  
State Dependent ◽  
The Times ◽  
And Diffusion

In this paper we consider reflected diffusions with positive and negative jumps, constrained to lie in the nonnegative orthant of ℝ n . We allow for the drift and diffusion coefficients, as well as for the directions of reflection, to be random fields over time and space. We provide a boundary behavior characterization, generalizing known results in the nonrandom coefficients and constant directions of the reflection case. In particular, the regulator processes are related to semimartingale local times at the boundaries, and they are shown not to charge the times the process expends at the intersection of boundary faces. Using the boundary results, we extend the conditions for product-form distributions in the stationary regime to the case when the drift and diffusion coefficients, as well as the directions of reflection, are random fields over space.

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