Alkaline earth metal oxides on γ-Al2O3 supported Co catalyst and their application to mercaptan oxidation

γ-Al₂O₃-supported alkaline earth metal oxide samples with different MgO, CaO, SrO and BaO loadings have been prepared by impregnating γ-Al₂O₃ with alkaline earth metal nitrate solutions and then calcining at 773 K and 1,023 K. The resultant samples have been characterized by XRD, EDS coupled with SEM, CO₂-TPD and BET. After preparation of the γ-Al₂O₃-supported alkaline earth metal oxide samples and impregnation with the liquid catalyst LCPs30, supplied by Axens, the catalytic performance of these catalysts was evaluated in the mercaptan oxidation reaction. Results showed that magnesium base oxide is formed at 773 K and base oxides of calcium, barium and strontium are formed at 1,023 K. Catalysts with higher mole ratios have higher conversions and the basicity increases with increasing base oxide loading in the samples. Furthermore, the conversion of mercaptans increases with increasing atomic number of the alkaline earth metal, excluding MgO, which has the highest conversion compared to the other base oxides.     

Assessment of mean and fluctuating velocity and temperature of CuO/water nanofluid in a horizontal channel: Large eddy simulation

Abstract

A comprehensive investigation applying the large eddy simulation approach to turbulent forced convection of CuO/water nanofluid flowing through a horizontal channel is carried out. Dealing with the sub-grid scale stress tensor and heat flux vector, the wall-adopting local eddy-viscosity model is employed. The periodic boundary condition is imposed to the streamwise and spanwise directions, while the no-slip and constant heat flux are applied to the walls. The results indicate that adding nanoparticles into the base fluid increases the dimensionless mean velocity and fluctuations of velocity and temperature. This increment is more evident for turbulent Reynolds stress and turbulent heat flux in the streamwise direction than the other directions. Therefore, higher energy is transferred between nanofluid layers which results in a higher amount of heat transfer than the pure water. It is also observed that the nanoparticles enhance the turbulence energy at all frequencies, and the decay in the fluctuations occurs at the higher wavenumbers.     

An Optical Imaging Technique Using Deep Illumination in the Angular Domain

This paper describes a novel optical imaging method, deep illumination angular domain imaging (ADI), for detecting micron-scale objects within highly scattering media. The new optical imaging is a much simpler and less expensive solution as compared to other available optical imaging techniques. In principle, deep illumination ADI uses collimation detection capabilities of small acceptance angle devices to extract photons emitted from the scattered light created by a laser source, aimed deep beneath the turbid medium surface. The laser source forms an illumination ball within the medium that emits scattered light in all directions and illuminates objects near the surface from behind. Consequently, when photons from this illumination ball pass an object and reach the angular filter, light that is not subsequently scattered passes through to a camera detector, whereas scattered photons are rejected by the filter. Image results obtained are recorded for different phantom locations, phantom sizes, and medium scattering levels. Our images clearly display sub-204 m phantoms when placed 3 mm deep within a test scattering medium with total effective attenuation coefficient (mu'_eff) up to 5.8^-1 cm or 2.5 mm deep in chicken tissue tests. Preliminary digital image processing shows the image contrast enhancement and the definition improvement.     

Analysis of Particle Dispersion and Entropy Generation in Turbulent Mixed Convection of CuO-Water Nanofluid

In the present study, turbulent mixed convection of CuO-water nanofluid is investigated in a vertical duct. In order to simulate the nanofluid flow, the fluid phase is considered as continuous whilst the discrete particles are dispersed through it. The dispersion of CuO nanoparticles at different Reynolds numbers is studied to predict the effective mechanisms concerning nanoparticles dispersion. Results show that in the turbulent fully developed region of the duct, the effect of thermophoresis is more important than Brownian motion and the dispersion of particles is higher in the duct core region. However, in the entrance region, the particles are dispersed almost uniformly. Also, increasing the nanoparticles volume fraction augments the root mean square of turbulent velocity fluctuations and this enhances the convective heat transfer as compared with the laminar flow. Moreover, increasing the nanoparticle volume fraction decreases the thermal entropy generation and increases the frictional entropy generation and due to the dominance of thermal entropy generation, the total entropy generation therefore reduces.