Extensive results elucidating the effect of severe blockage on drag coefficient and Nusselt number for a heated sphere sedimenting in Bingham plastic fluids on the axis of a long cylindrical tube over wide ranges of blockage ratio (0.5≤λ≤0.95), Reynolds number (1≤Re≤100), Prandtl number (5≤Pr≤100) and Bingham number (0.01≤Bn≤100) are reported in this study. Both drag coefficient and Nusselt number are enhanced with the increasing values of λ and Bn due to the sharpening of the velocity and temperature gradients on the surface of the sphere and the backflow of the fluid displaced by the falling sphere along with the diminishing yielded regions. The influence of velocity distribution in the tube also gradually weakens with the increasing λ and Bn. However, the constant heat flux condition prescribed on the surface of the sphere is more effective in promoting heat transfer than the case of an isothermal sphere. The regions of fluid-yielding expand with the increasing Reynolds number which is countered by the increasing Bingham number. The present numerical results have been consolidated via simple correlating expressions with acceptable levels of accuracy.
A unique oscillatory phenomenon was observed in a horizontal cylindrical vessel. In our previous study, we confirmed that this oscillation was caused by a bubble flow from an aeration tube located at the bottom of the vessel. Herein, to extend this research, we examined the effect of the diameter of the vessel on the oscillation induced by the bubble flow. Novel scaled-up vessels with a diameter of D=0.20 and 0.29 m were prepared. First, the occurrences of oscillation in the scaled-up vessels regardless of the scale of the vessel were confirmed. The liquid motion in the vessel was visualized to understand the mechanism of bubble-induced oscillation. The visualization showed that the upward bubble flow induced the circulating flow and the development of circulating flow caused the oscillation. The upward bubble flow oscillated and was pushed alternately by the circulating flow as if there was a spring on both sides. Second, an oscillation sensor was newly developed to automatically detect the oscillation; it could accurately measure the oscillation frequency. Using the oscillation sensor, the oscillation frequency was measured in each scale of vessel. Changes in geometry, aeration system, and height of liquid surface did not affect the oscillation frequency. It was determined to one given the diameter of the vessel. Thus, a correlation equation was proposed as a function of the diameter of the vessel. The frequency of bubble-induced oscillation was finally derived as The circumference of circulating flow, πD/4, was used as the characteristic length in the equation. The oscillation frequency estimated by the correlation equation provides good agreement with experimental results.
Extraction behavior of rhodium (III) with a liquid surfactant membrane (LSM) containing an ionic liquid, 1-octyl-3-methylimidazolium hexafluorophosphate ([Omim][PF6]), as a carrier from hydrochloric acid solutions has been investigated. At the optimum conditions, rhodium was selectively extracted over tin by using LSMs in which [Omim][PF6] acted as the mobile carrier. The effects of important operational parameters on the recovery of rhodium were examined with three different stripping reagents for LSMs. It was found that the use of 2-amino-2- hydroxymethyl-1,3-propanediol (Tris) as a stripping reagent in LSMs was the key for the effective extraction of rhodium.
The adsorbed amounts of seven anticancer compounds on hydroxyapatite (HAp) were compared: fluorouracil (5-FU), cyclophosphamide (CPA), mercaptopurine (6-MP), cytarabine (Ara-C), azacytidine (5-AC), mitoxantrone (MXT), and doxorubicin (DOX). The adsorbed amounts of 5-FU, CPA, 6-MP, Ara-C and 5-AC were very small at several mg/g-HAp. On the contrary, those of MXT and DOX were much larger of 44 and 64 mg/g-HAp, respectively. These larger amounts may be ascribed to higher acidity of MXT and DOX: hydroxyl groups attached to aromatic ring may lead to the higher H+-donating ability than the other five compounds, promoting adsorption on HAp with basic character. The desorption rate of DOX in 100 mM phosphate buffered solution (PBS) was more than two times that of MXT, indicating the weaker binding strength of DOX to the surface of HAp. The larger amount and the higher desorption rate of DOX were due to its steric structure and self-association through π–π stacking of the aromatic rings, hydrogen bond or dipole effect of hydroxyl groups of the molecules.