The Binary System CaO–Nb2O5

The binary system CaO-Nb₂O₅ has been shown to include three compounds: CaO·Nb₂O₅, which melts congruently at 1560°C; 2CaO·Nb₂O₅, which melts congruently at 1576°C; and 3CaO·-Nb₂O₅, which melts incongruently at 1560°C. Three eutectic compositions occur at 6% CaO (1362°C), 23% CaO (1492°C), and 34% CaO (1535°C). These results were obtained by the cone-fusion technique. The compound 3CaO-Nb₂O₅ has been shown to exist in two forms: type I, face-centered cubic with a = 7.978 A, having a superlattice with a = 23.934 A, and type II, orthorhombic (pseudotetragonal, distorted cubic) with a = 11.51 A, b = 11.10 A, c = 15.98 A, having a pseudocell with a = 5.754 A, b = 5.551 A, and c = 7.990 A. The conditions controlling the formation of these two forms were not determinable from the experiments conducted.     

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The problem of imposing an in-line velocity perturbation on a uniform flow about a fixed cylinder is studied numerically. A finite volume method using SIMPLEC algorithm is applied on an O-type body-fitted co-located grid. The effect of frequency, amplitude, and shape of the velocity perturbation on the lift and drag coefficients and the Nusselt and Strouhal numbers were studied for the case of Reynolds number equal to 1000. It is noticed that lock-on is present and have a pronounced effect on the average Nusselt number, increasing it by 8.3 percent relative to the uniform flow value, though with a lower effect on drag and lift coefficients. In addition, it is concluded that a sinusoidal perturbation with a dimensionless frequency equal to 0.15 and dimensionless velocity perturbation equal to 0.2 is a better choice to enhance the heat transfer rate.