Porosity changes

In compressible filter cakes, the porosity varies from a minimum next to the filter septum to a maximum at the cake surface. How could you include such a variation within the context of a simulation program Remember that as the porosity changes, the local fluid velocity will also change as a result of... 

The presence of a small amount of water vapor (up to pH20/pH2 = -0.03) in fuel reduces anode overpotential. For anode-supported cells, the use of pore formers is important to tailor the shrinkage during cofiring and to create adequate porosity for better performance. The difference in cell power output could differ by as much as 100% for cells as porosity changes from -30 to -50%. 

Equations (5.95), (5.96) and (5.97) are suitable for constant critical melting porosity. In a one dimensional steady state melting column as a result of decompression melting, the porosity may increase from the bottom to the top of the column. If melting porosities change as a function of the spatial position, the related differential equations need to be solved numerically. More details of various melt transport models by porous flow have been given by Spiegelman and Elliott (1993), Iwamori, (1994), and Lundstrom (2000). 

Figure 1.98a-e show the relationship between RF and RNIF for the five products. The Karl Fischer titration results can fluctuate up to 0.5% with day-to-day and operator variations. Therefore, a difference between RF and RNIR of <0.5% is accepted as good. The porosity change from 30 to 100 mg/mL was <0.5%. The cake dimensions... 

Figure 8.34. Hypothetical porosity-depth curves for various diagenetic situations. A. "Normal" burial curve of chalk sequences. B. A typical curve stemming from porosity changes brought about by dissolution and cementation processes during meteoric zone diagenesis. C. A scenario for late stage porosity development brought about by a dissolution event related to hydrocarbon maturation and destruction. D. Porosity preservation resulting from conditions of overpressuring. (After Choquette and James, 1987.)...

The secondary reactions result in a H2 production in the absence of gaseous diborane. The secondary reactions are induced by temperature. Although the primary and secondary reactions seem fairly compatible regarding the mechanism, their effect on porosity may differ significantly. Gillis-D Hamers investigated also the porosity changes induced by these secondary reactions. 

S. Kitahara, K. Tanaka, T. Sakata, and H. Muraishi, Porosity change of silica gels by the alkoxylation of their surfaces, / Colloid Interface Sci. 84 (1981), 519-525. 

AHSTRACT Modelling and computing of thermal biomass treatment processes involving thick layers requires that the gas permeability and hydraulic resistance of such layers be known. The paper presents the results of experimental research into the hydraulic resistance of the thick layer comprised of two biomass varieties sunflower husks and sawdust. The research was conducted within the range of Re alteration from 5-70, and layer porosity change 0.2-0.7,... 

Ramachandran, P. Smith, J. Effect of sintering and porosity changes on rates of gas-solid reactions. Chem. Eng. J. (Lausanne) 1977, 14, 137-146. 

However, whether or not the metal is incorporated into the support, including these salts in the synthetic gel causes substantial morphological and porosity changes in the resulting solids. 

In summary, we synthesized various types of silica by using a non-ionic surfactant as template in the presence of different platinum salts in the synthetic gel. The salts were found to induce substantial structural and porosity changes in the materials obtained. In fact, they promote the hydrolysis and condensation of the silicon precursor the degree of cross-linking... 

Gluyas, j. Coleman, M. (1992) Material flux and porosity changes during sediment diagenesis. Nature, 356, 52-54. 

Sanford, W. E., and Konikow, L. F 1989. Simulation of calcite dissolution and porosity changes in seawater mixing zones in coastal aquifers. Water Resources Res., v. 25, pp. 665-667. 

Coupling of Precipitation—Dissolution Reactions to Mass Diffusion via Porosity Changes... 

The methane migration during coal mining is caused by loss of the in-situ equilibrium between the coal skeleton stress and methane pressure. The interactions between coal deformation and methane migration have several aspects effective stress change in coal seams due to excavation and mining, porosity change and methane content increase,... 

Biot assumed that porosity (< i) was a fixed parameter recent work shows that for porous media, i i is a thermodynamic variable similar to pressure and temperature, and it must be treated as a dynamic variable (Spanos et al. 2003). For the temporal evolution a porous medium, the porosity change must be stipulated as follows ... 

Porosity change with time (porosity diffusion) is specified by the divergence of the velocities of the phases, multiplied by their densities (5 5f). 

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