The reaction kinetics of carbon reduction of silica were investigated using thermodynamic concepts and by fitting to relevant models the experimental data obtained for this reduction using a thermogravimetric unit in the temperature range of 1566 to 1933 K. The results show that the only way to produce SiC in this reduction is the reaction of Si, SiO, or SiO2 at the surface or by diffusion of SiO inside the carbon particles while CO and CO2 have no direct effect on the process. The controlling step of this reduction at temperatures lower than 1750 K is the chemical gas–solid or solid–solid reaction at the surface of the carbon particles, while at higher temperatures, the rate of SiO diffusing inside the carbon particles controls the rate of this reduction.
A fully three-dimensional computational fluid dynamic model is used to analyze the mechanism of flow and heat transfer in a vortex tube. Vortex tube is a simple circular tube with interesting function and several industrial applications and contains one or more inlets and two outlets. It is used as a spot cooling device in industry. The past numerical investigations of vortex tube have been performed with the two-dimensional axisymmetric assumption but in the present work this problem is studied fully three-dimensional without making that assumption. Using this model, appropriate numerical results are presented to clarify physical understanding of the flow and energy separation inside the vortex tube. It is observed that there are considerable differences between the results of the two aforementioned models, and that the results of fully three-dimensional model are more accurate and agree better with available experimental data. Moreover, the parameters affecting the cooling efficiency of the vortex tube are discussed.
A robust modified weakly compressible smoothed particle hydrodynamics (WCSPH) method based on a predictive corrective scheme is introduced to model the fluid flows engaged with stationary and moving boundary. In this paper, this model is explained and practically verified in three distinct laminar incompressible flow cases; the first case involves the lid driven cavity flow for two Reynolds numbers 400 and 1000. The second case is a flow generated by a moving block in the initially stationary fluid. The third case is flow around the stationary and transversely oscillating circular cylinder confined in a channel. These results in comparison with the standard benchmarks also confirm the good accuracy of the present solution algorithm.
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