Natural Convection from a Heated Elliptic Cylinder with a Different Axis Ratio in a Square Enclosure

A detailed study about the free convection over a heated elliptic cylinder, placed at the center of a square cavity having cooled walls, is performed. Simulations are carried out for three Rayleigh numbers (10⁴, 10⁵, and 10⁶) and two cavity aspect ratios (CR = 2.5 and 5.0) for different axis ratio (AR). The effect of AR on fluid flow and heat transfer characteristics for varying Rayleigh number and cavity aspect ratio are analyzed. The influence of AR is phenomenal at higher Ra and lower CR. At higher Ra, thermal plumes are observed above the cylinder for different ARs. Bicellular vortices are formed at low Ra by changing CR. The surface-averaged Nusselt number (Nu _avg ) increases with increasing AR and Ra. The value of Nu _avg increases with decreasing CR, and a correlation for Nu _avg in terms of AR is obtained for each CR.     

Aldimines — Effective Corrosion Inhibitors for Mild Steel in Hydrochloric Acid Solution

New and effective aldimine types of corrosion inhibitors namely, N-methylidene octylamine (MOA), N-ethylidene octylamine (EOA) and N-propylidene octylamine (POA) have been synthesized. Their inhibition efficiency was investigated for the corrosion of mild steel in 1 M HCl solution by various corrosion monitoring techniques. A preliminary screening of the inhibition efficiency of the inhibitors was carried out by weight loss and gasometric studies. They were found to behave as good inhibitors in 1 M HCl solution. Potentiodynamic polarization measurements show that aldimines are mixed type inhibitors. The extent of the decrease in the hydrogen permeation current through the mild steel surface was studied by the hydrogen permeation technique and it was found that the decrease was in the order POA > EOA > MOA. Double layer capacitance and charge transfer resistance values were derived from Nyquist plots obtained from AC impedance studies. The adsorption of these compounds on mild steel from 1 M HCl solution obeys the Temkin adsorption isotherm.     

DSC study on the melting properties of palm oil, sunflower oil, and palm kernel olein blends before and after chemical interesterification

Changes in DSC melting properties of palm oil (PO), sunflower oil (SFO), palm kernel olein (PKOo), and their belends in various ratios were studied by using a combination of blending, and chemical interesterification (CIE) techniques and determining total melting (ΔH _f ) and partial melting (ΔH _i°C ) enthalpies. Blending and CIE significantly modified the DSC melting properties of the PO/SFO/PKOo blends. PO and blends containing substantial amounts of PO and PKOo experienced an increase in their DSC ΔH _f and ΔH _i°C following CIE. The DSC ΔH _f and ΔH _i°C of PKOo, blends of PO/SFO at 1∶1 and 1∶3 ratios, and all blends of PKOo/SFO significantly decreased after CIE. The DSC ΔH _f and ΔH _i°C of SFO changed little following CIE. Randomization of FA distribution within and among TAG molecules of PO and PKOo led to modification in TAG composition of the PO/PKOo blends and improved miscibility between the two fats and consequently diminished the eutectic interaction that occurred between PO and PKOo.     

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Technical news feature Palm carotenoids, tocopherols and tocotrienols     

DIRECT SYNTHESIS OF RU-NI NANOPARTICLES WITH CORE-AND-SHELL STRUCTURE

Nanoparticles of Ru-Ni with a core-and-shell structure were synthesized as potential catalysts for fuel cells and other applications in a single-step spray-pyrolysis process at 700°–800°C. The majority of the core consists of ruthenium, while the shell is predominately composed of nickel. Bimetallic nanoparticles with a core-and-shell structure are being considered as new and promising catalysts with enhanced catalytic activity, better stability, and higher resistance to contaminants for fuel cells and other applications. An aqueous precursor containing ruthenium chloride and nickel chloride was nebulized by an ultrasonic atomizer to generate an aerosol. Droplets were subsequently decomposed to form uniformly distributed Ru-Ni bimetallic nanoparticles, then deposited on a substrate. Atomic fractions and melting temperatures are expected to play a crucial role in the formation of core-and-shell structures.     

Nano-size LiAlO2 ceramic filler incorporated porous PVDF-co-HFP electrolyte for lithium-ion battery applications

The optimized composition of PVdF-co-HFP-LiAlO₂ based micro-porous nano-composite polymer electrolyte membranes (MPNCPEMs) was prepared with a preferential polymer dissolution process. Nitrogen adsorption isotherms and SEM micrographs showed that the enhanced ionic conductivity of polymer electrolyte was due to increase in pore-size, surface area and pore density, results an increase in the electrolyte uptake. The ac-impedance spectroscopy showed that the room temperature ionic conductivity of PVdF-co-HFP-LiAlO₂ based polymer electrolyte membranes increased with the removal of PVA content and attained the maximum ionic conductivity of 8.12 × 10⁻³ S cm⁻¹. The prepared MPNCPEM of high ionic conductivity was subjected into LSV study. Finally, the electrode/electrolyte interfacial resistance was evaluated by monitoring the impedance response at different time intervals.     

Effect of chemical interesterification on triacylglycerol and solid fat contents of palm stearin,sunflower oil and palm kernel olein blends

Palm stearin (POs) with an iodine value of 41.4, sunflower oil (SFO) and palm kernel olein (PKOo) were blended in various ratios according to a three‐component mixture design and subjected to chemical interesterification (CIE). Triacylglycerol (TAG) and solid fat content (SFC) profiles of the chemically interesterified (CIEed) blends were analyzed and compared with those of the corresponding non‐CIEed blends. Upon CIE, extensive rearrangement of fatty acids (FA) among TAG was evident. The concentrations of several TAG were increased, some decreased and several new TAG might also have been formed. The changes in the TAG profiles were reflected in the SFC profiles of the blends. The SFC of the CIEed blends, except the binary blends of POs/PKOo which experienced an increase in SFC following CIE, revealed that they were softer than their respective starting blends. Randomization of FA distribution within and among TAG molecules of POs and PKOo led to a modification in TAG composition of the POs/PKOo blends and improved miscibility between the two fats, and consequently diminished the eutectic interaction that occurred between POs and PKOo.