5,105 research outputs found

    Accuracy of bubble velocity measurement with a four-point optical fibre probe

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    For the operation of high void fraction bubbly flows in bubble\ud columns, insight in primary parameters such as bubble size,\ud shape and velocity as well as gas volume fraction is essential.\ud At high gas volume fractions the flow system becomes\ud opaque, ruling out non-intrusive optical techniques. As an\ud alternative optical fibre probes can be used, which have the\ud advantage of low cost, simplicity of setup and easy\ud interpretation of the results.\ud By using four-point optical fibre probe, properties of bubbles\ud can be studied, such as bubble velocity, bubble size, etc.\ud However, the effect of bubble wobbling behaviour and\ud physical properties of liquids on the accuracy of the velocity\ud measurements has not been investigated in detail.\ud In the present study, the performance of a four-point optical\ud fibre probe was evaluated for five different liquids. The probe\ud performance and causes of inaccuracies are discuss

    Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy Characterization of Adhesive Produced From Polystyrene Waste

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    In this study, the optimized adhesive formulated from polystyrene waste was characterized for Fourier transform infrared (FTIR) spectra, Scanning Electron Microscopy (SEM) / Energy Dispersive X-ray (EDX) spectroscopy, solubility, density and water absorption for identification of existing functional group(s), morphology, elemental compositions, etc. The results revealed that polystyrene, unsaturated hydrocarbon has been degraded to form a new product containing aromatic compounds. SEM morphology showed well mixed blended adhesive with silver-like appearance due to additives and EDX revealed 12 existing elemental compositions with their corresponding percentage atomic weights as follows; carbon 93.14 %, hafnium 1.44 %, vanadium 1.66 %, chromium 1.40 %, bromine 0.47 %, palladium 0.26 %, copper 0.43 %, nickel 0.31 %, cobalt 0.29 %, potassium 0.38 %, iron 0.15 % and manganese 0.08 %. The produced polystyrene adhesive was sparsely soluble in water after 30 minutes; it has a density of 1041 kg/m3 and does not absorb moisture. Because of these results, the adhesive from polystyrene waste could serve as green adhesive, since there are no threats of toxic substance emission from the spectral analysis since most of the elements are used as a supplement in pharmaceuticals and catalyst in process industries

    Determination of molecular diffusivities in liquids

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    A porous plate, initially at a uniform solute concentration is immersed in a well-stirred pure solvent bath of known volume. It is desired to find the molecular diffusivity of the solute-solvent system by observing the change of the solute concentration in the solvent bath with time. In this study, concentration-time data were curve-fitted by non-linear, least squares techniques to the various mathematical solutions describing molecular diffusion in the porous frit. This technique is used to determine the diffusion coefficient and predict the value of other parameters existing in the different mathematical diffusion models. The results from the different models are critically compared. The following solute-solvent systems were studied in this work: ethylene glycol in ethylene glycol; ethylene glycol in diethylene glycol; ethylene glycol in propylene glycol; cyclohexanol in ethylene glycol; cyclohexanol in diethylene glycol; and cyclohexanol in propylene glycol at 25, 30, 40 and 50°C. The experimental diffusivities determined in this study were then compared with the vales from the proposed prediction equations of Wilke-Chang, Gainer and Metzner, and Mitchell--Abstract, Page ii

    Performance of diethylene glycol based particle counters in the sub 3 nm size range [Discussion paper]

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    When studying new particle formation, the uncertainty in determining the "true" nucleation rate is considerably reduced when using Condensation Particle Counters (CPCs) capable of measuring concentrations of aerosol particles at sizes close to or even at the critical cluster size (1–2 nm). Recently CPCs, able to reliably detect particles below 2 nm in size and even close to 1 nm became available. The corrections needed to calculate nucleation rates are substantially reduced compared to scaling the observed formation rate to the nucleation rate at the critical cluster size. However, this improved instrumentation requires a careful characterization of their cut-off size and the shape of the detection efficiency curve because relatively small shifts in the cut-off size can translate into larger relative errors when measuring particles close to the cut-off size. Here we describe the development of two continuous flow CPCs using diethylene glycol (DEG) as the working fluid. The design is based on two TSI 3776 counters. Several sets of measurements to characterize their performance at different temperature settings were carried out. Furthermore two mixing-type Particle Size Magnifiers (PSM) A09 from Airmodus were characterized in parallel. One PSM was operated at the highest mixing ratio (1 L min−1 saturator flow), and the other was operated in a scanning mode, where the mixing ratios are changed periodically, resulting in a range of cut-off sizes. Different test aerosols were generated using a nano-Differential Mobility Analyzer (nano-DMA) or a high resolution DMA, to obtain detection efficiency curves for all four CPCs. One calibration setup included a high resolution mass spectrometer (APi-TOF) for the determination of the chemical composition of the generated clusters. The lowest cut-off sizes were achieved with negatively charged ammonium sulphate clusters, resulting in cut-offs of 1.4 nm for the laminar flow CPCs and 1.2 and 1.1 nm for the PSMs. A comparison of one of the laminar-flow CPCs and one of the PSMs measuring ambient and laboratory air showed good agreement between the instruments

    Cellulase immobilization on superparamagnetic nanoparticles for reuse in cellulosic biomass conversion

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    Current cellulosic biomass hydrolysis is based on the one-time use of cellulases. Cellulases immobilized on magnetic nanocarriers offer the advantages of magnetic separation and repeated use for continuous hydrolysis. Most immobilization methods focus on only one type of cellulase. Here, we report co-immobilization of two types of cellulases, ÎČ-glucosidase A (BglA) and cellobiohydrolase D (CelD), on sub-20 nm superparamagnetic nanoparticles. The nanoparticles demonstrated 100% immobilization efficiency for both BglA and CelD. The total enzyme activities of immobilized BglA and CelD were up to 67.1% and 41.5% of that of the free cellulases, respectively. The immobilized BglA and CelD each retained about 85% and 43% of the initial immobilized enzyme activities after being recycled 3 and 10 times, respectively. The effects of pH and temperature on the immobilized cellulases were also investigated. Co-immobilization of BglA and CelD on MNPs is a promising strategy to promote synergistic action of cellulases while lowering enzyme consumption