A simplified description of multicomponent diffusion in porous media. I. Diagonalization of the matrix of effective diffusion coefficients

1978 ◽  
Vol 43 (1) ◽  
pp. 1-9
Author(s):  
Marta Černá ◽  
Jindřich Zahradník ◽  
Petr Schneider
Keyword(s):  
Porous Media ◽  
Diffusion Coefficients ◽  
Effective Diffusion ◽  
Multicomponent Diffusion ◽  
Effective Diffusion Coefficients ◽  
The Matrix ◽  
Diffusion In Porous Media

Diffusion of 65Zn in AZ91 and QE22 Alloys with Saffil Reinforcement-Influence of Interfaces Matrix/Saffil

2009 ◽  
Vol 289-292 ◽  
pp. 145-152
Author(s):  
Ivo Stloukal ◽  
Jiří Čermák
Keyword(s):  
Temperature Interval ◽  
Diffusion Coefficients ◽  
Volume Diffusion ◽  
Effective Diffusion ◽  
Measured Temperature ◽  
Elastic Stresses ◽  
Effective Diffusion Coefficients ◽  
Sectioning Method ◽  
The Matrix ◽  
Zinc Diffusion

Diffusion of 65Zn in two commercial Mg-based alloys AZ91 and QE22 with short Saffil fibers was studied. Experiments were carried out in the temperature interval 648 – 728 K by serial sectioning method. The effective diffusion coefficients Deff were compared with 65Zn diffusion coefficients Dv obtained with the same alloys without Saffil fibers. The evaluation of the influence of the interface between the matrix and the fibers upon Deff was done and the zinc diffusion coefficient Di in the interface boundary matrix/Saffil was estimated. Unlike the Arrhenius-like behavior of volume diffusion in both alloys, it was observed that the temperature dependence of both Deff and Di was significantly concave in the measured temperature interval. This behavior was attributed to relaxation of thermo-elastic stresses in the composite induced by a large difference between coefficients of thermal expansion (CTE) of Saffil fibers and metal matrix. The maximum values of Deff and Di, respectively, lie close to 693 K, where CTE has a minimum.

Effective Diffusion Coefficients and Thermal Stability of the Structure of Metallic Glass Fe48Co32P14B6

2020 ◽  
Vol 62 (12) ◽  
pp. 2258-2265 ◽  
Author(s):  
S. V. Vasiliev ◽  
V. I. Parfenii ◽  
E. A. Pershina ◽  
A. S. Aronin ◽  
O. V. Kovalenko ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Metallic Glass ◽  
Diffusion Coefficients ◽  
Effective Diffusion ◽  
Effective Diffusion Coefficients ◽  
Thermal Stability Of

scholarly journals Modeling and thermodynamic properties of ‘bacaba’ pulp drying

2019 ◽  
Vol 23 (9) ◽  
pp. 702-708 ◽  
Author(s):  
Maria F. de Morais ◽  
José R. O. dos Santos ◽  
Marisângela P. dos Santos ◽  
Dyego da C. Santos ◽  
Tiago N. da Costa ◽  
...  
Keyword(s):  
Activation Energy ◽  
Thermodynamic Properties ◽  
Diffusion Coefficients ◽  
Effective Diffusion ◽  
Thermal Conditions ◽  
Drying Process ◽  
Experimental Conditions ◽  
Effective Diffusion Coefficients ◽  
Drying Rates ◽  
Increasing Temperature

ABSTRACT This study aimed to dry ‘bacaba’ (Oenocarpus bacaba Mart.) pulp under different thermal conditions, fit different mathematical models to the dehydration curves, and calculate the diffusion coefficients, activation energy and thermodynamic properties of the process. ‘Bacaba’ fruits were meshed to obtain the pulp, which was dried at temperatures of 40, 50 and 60 °C and with thickness of 1.0 cm. Increase in drying temperature reduced the dehydration times, as well as the equilibrium moisture contents, and drying rates of 0.65, 1.04 and 1.25 kg kg min-1 were recorded at the beginning of the process for temperatures of 40, 50 and 60 °C, respectively. The Midilli’s equation was selected as the most appropriate to predict the drying phenomenon, showing the highest R2, lowest values of mean square deviation (MSD) and χ2 under most thermal conditions, and random distribution of residuals under all experimental conditions. The effective diffusion coefficients increased with increasing temperature, with magnitudes of the order of 10-9 m2 s-1, being satisfactorily described by the Arrhenius equation, which showed activation energy (Ea) of 37.01 kJ mol-1. The drying process was characterized as endergonic, in which enthalpy (ΔH) and entropy (ΔS) reduced with the increment of temperature, while Gibbs free energy (ΔG) was increased.

Measurement of effective diffusion coefficients in dairy powders by confocal microscopy and sorption kinetic profiles

2019 ◽  
Vol 20 ◽  
pp. 100108 ◽  
Author(s):  
Valentyn Maidannyk ◽  
Eva Lutjes ◽  
Sharon Montgomery ◽  
Noel McCarthy ◽  
Mark A.E. Auty
Keyword(s):  
Confocal Microscopy ◽  
Diffusion Coefficients ◽  
Effective Diffusion ◽  
Sorption Kinetic ◽  
Effective Diffusion Coefficients ◽  
Dairy Powders
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