Detached Eddy Simulation on the Turbulent Flow in a Stirred Tank

A detached eddy simulation (DES), a large-eddy simulation (LES), and a k-ε-based Reynolds averaged Navier-Stokes (RANS) calculation on the single phase turbulent flow in a fully baffled stirred tank, agitated by a Rushton turbine is presented. The DES used here is based on the Spalart-Allmaras turbulence model solved on a grid containing about a million control volumes. The standard k-ε and LES were considered here for comparison purposes. Predictions of the impeller-angle-resolved and time-averaged turbulent flow have been evaluated and compared with data from laser doppler anemometry measurements. The effects of the turbulence model on the predictions of the mean velocity components and the turbulent kinetic energy are most pronounced in the (highly anisotropic) trailing vortex core region, with specifically DES performing well. The LES—that was performed on the same grid as the DES—appears to lack resolution in the boundary layers on the surface of the impeller. The findings suggest that DES provides a more accurate prediction of the features of the turbulent flows in a stirred tank compared with RANS-based models and at the same time alleviates resolution requirements of LES close to walls

EXTRACTION AND MICROENCAPSULATION OF POLYPHENOLS FROM ORTHOSIPHON STAMINEUS LEAVES

This paper presents an extraction and microencapsulation study of polyphenols obtained from Orthosiphon stamineus leaves. Extraction using aqueous solvent enabled a simultaneous extraction of both hydrophilic and lipophilic phenolic compounds. Higher solid concentration leads to higher solution viscosity, bigger particle size, lower moisture content and a less dented surface, which may improve particle flowability. The results suggest that eupatorin and rosmarinic acid are more susceptible to thermal degradation than sinensetin during spray drying. The formulation of 1:9 whey protein to maltodextrin ratio was also found to be more effective, with 86.7% total flavonoids retention compared to other formulations, viz, 1:1 and 9:1. This paper presents an extraction and microencapsulation study of polyphenols obtained from Orthosiphon stamineus leaves. Extraction using aqueous solvent enabled a simultaneous extraction of both hydrophilic and lipophilic phenolic compounds. Higher solid concentration leads to higher solution viscosity, bigger particle size, lower moisture content and a less dented surface, which may improve particle flowability. The results suggest that eupatorin and rosmarinic acid are more susceptible to thermal degradation than sinensetin during spray drying. The formulation of 1:9 whey protein to maltodextrin ratio was also found to be more effective, with 86.7% total flavonoids retention compared to other formulations, viz, 1:1 and 9:1

Enhancement of Biodiesel Yield from High FFA Malaysian Rubber Seed Oil with Sodium Methoxide Treated Limestone

This paper presents the potential of high free fatty acid (FFA) Malaysian rubber seed oil (MRSO) as feedstock for biodiesel production. Precalcinated limestone known as clinker was activated using either methanol or sodium methoxide and transesterification was performed under reflux at constant stirring. Mineral composition of the catalyst was analysed using x-ray fluorescence (XRF) with in build x-ray diffraction (XRD) indicates about 66% of CaO content. The rubber seed oil was obtained using both microwave and soxhlet extraction using hexane as solvent. FFA content and fatty acid methyl ester content were determined using gas chromatography mass spectrometry (GC-MS). The methanol activated limestone based catalyst derived from cement clinker showed an efficient conversion (up to 96.7%) of high FFA rubber seed oil to biodiesel, and the biodiesel yield was 75%. The yield of biodiesel improved significantly (up to 88%) when sodium methoxide loaded clinker was used. The results suggest that the sodium methoxide activated catalyst employed in this work was less likely to be negatively affected by moisture and free fatty acids as compared to the methanol activated catalyst. The biodiesel produced in this work is within the limits of specification described by ASTM D6751

Synthesis and characterization of nano-hydroxyapatite/graphene oxide composite materials for medical implant coating applications

In this present work, nano-hydroxyapatite/Graphene Oxide were synthesized, and the composite were prepared in different ratios. The structural and morphological changes of synthesized nano hydroxyapatite, graphene oxide and reduced graphene oxide was investigated. Fourier Transform Infrared Spectrometer (FTIR) was used to investigate the chemical structural composition of the synthesized nano hydroxyapatite and its composite, which confirms that presence of presence of reduced graphene oxide, graphene oxide in the prepared composite. Field emission scanning electron microscopy (FE-SEM) analysis was employed to examine the surface morphology of the composite materials which confirms the presence graphene flakes and nanosized hydroxyapatite on the surface

Ultrasonic Assisted Extraction Polyphenols andD Antioxidant from Nigella Sativa Seed

This paper presents an ultrasonic assisted extraction study of essential oil from Nigella sativa seeds. It was found that the extraction of phenolic, flavonoid and antioxidant favours pure solvent, i.e. ethanol and methanol. Extraction of phenoilc, flavonoid and antioxidant, increases with increasing temperature until 50°C but reduced thereafter. Increasing the sonication power from 112 W to 224 W improved extraction of phenolic, flavonoid and antioxidant markedly, although a further increase to 277 W is not an improvement. A lower sonication frequency (35 kHz) yielded higher polyphenols and antioxidant content as opposed to the higher frequency (53 kHz). The highest total phenolic content (0.66 mg GAE/g sample), total flavonoid content (1.84 µg QE/g sample) and antioxidant activities (63.15%) using ethanol at sonication power of 224 W, extraction time of 30 minutes and temperature of 50°C

Data for: A Mass Spectrometry and Principle Component Analysis on the Effect of Auxiliary Energy to the Terpenes Extraction from Andrographis Paniculata

Data for maceration, ultrasonic assisted extraction and microwave assisted extraction of terpene from Andrigraphis paniculata