The Mixing rules of Modified Huron and Viddal, (MHV1), Wong and Sandler, (W-S), and a new mixing rule based on a combination of W-S and MHV1 using neural networks, called combined mixing rule (CMR) have been revised and extended to applications involving mixtures with non-condensable gases over broader ranges of temperature and pressure. The paper presents the use of Modified UNIFAC (Lyngby) with the equation of state Soave-Redlich-Kwong (SRK) for the prediction of solubility of gases in different mixtures of alkanes and alcohols.
Field equations for the steady flow of power-law dilatant fluids normal to an array of long circular cylinders have been solved numerically using the finite difference method. The cylinder-cylinder interactions have been simulated using the two widely used concentric cylindrical cell models, namely, the Free surface and Zero vorticity cell models. Extensive theoretical results on the individual components of flow resistance arising from pressure and shear forces are presented for a range of physical and kinematic conditions. Furthermore, information on the variation of vorticity and power-law viscosity is also presented to provide some physical insights into the nature of the flow field. The results presented herein encompass the following ranges of physical and kinematic conditions: ε = 0.5 and 0.9; Re = 0.1, 1 and 10 and 1 ≤ n ≤ 1.8. An excellent match between theory and experiments for Newtonian fluids demonstrates the utility of this simple approach to the modeling of momentum transfer in fibrous beds and tubular heat exchangers. However, no suitable experimental results are available for dilatant fluids in these systems.
Nonlinear oscillations of molten silicon drops in an electromagnetic levitator under microgravity are numerically investigated. The electromagnetic field and the magnetic pressure on the drop surface are calculated by the surface integral method assuming that the skin depth is much smaller than the drop radius. The Galerkin finite element method in combination with the Lagrangian technique is used to analyze the moderate-amplitude axisymmetric oscillations of the silicon drops on which the magnetic pressure acts. The effect of the electric current ratio of the heating coils to the levitation coils on the frequency of the oscillations is evaluated for molten silicon drops released from either an initially prolate spheroid configuration or four-lobed spherical harmonic configuration. The numerical results show that, in the former case, the frequency decreases with the current ratio. Also, for the latter, the dynamics of the second mode becomes dominant as the current ratio increases, because the inward magnetic pressure from the heating coil increases.
Experiments on mixing performance have been carried out by reciprocating a disk in a cylindrical vessel. The force acting on the disk was measured by a force transducer installed between the impeller shafts, and the disk position was detected by a photo interrupter. With increasing reciprocating Reynolds number, the dimensionless maximum force acting on the disk decreases in inverse proportion to the Reynolds number in laminar creeping flow and becomes almost constant in turbulent flow. The Lissajous figure of force and disk position during reciprocation is deformed from an ellipsoid to an inclined parallelogram as the flow changes from laminar to turbulent. The average power is obtained by integrating the product of force and disk velocity during one cycle. The power number can be correlated with the reciprocating Reynolds number in a similar way to correlating the maximum force. The mixing process was visualized by using the decolorizing reaction, based on which the flow behavior could be divided into three patterns; laminar creeping flow without vortex generation, laminar flow with generation of a vortex which dissipates within a half cycle of reciprocation, and turbulent flow with vortexes. The mixing process is extremely slow in laminar creeping flow. It is promoted by stretching and folding of fluid lumps in the flow with vortex generation. The dimensionless mixing time was investigated in terms of the power input per unit volume of liquid. In turbulent flow, the mixing time is considerably smaller than that required for ordinary rotating mixing.
Free molecular flow through a long conduit with an orifice-restricted exit was analyzed theoretically using a local Maxwellian distribution function. The theoretically derived transmission probabilities for the conduit with the ratio of length to tube diameter greater than 15, and the cross-sectional area ratio of tube and orifice openings greater than 70 agrees well with those computed using a Monte Carlo method.
We developed an apparatus to measure the thermal diffusivity of a nonlinear optical (NLO) polymer thin film where the measurement was based on the photoacoustic method. The validity of the measured data was verified by comparison with published ones for Ti and Pt metallic foils. The thermal diffusivity of a polymer thin film, polymethyl methacrylate (PMMA) with Disperse Red 1 (DR1) chromophore side group, is independent of the thickness and the percentage of the chromophore, and is almost constant at 6 × 10–8 m2/s. The thermal diffusivity of the electrically poled NLO polymer thin film is independent of the intensity of the applied electric field.
This paper reviews the results of two sets of compression-permeability cell (C-P cell) experiments, with cationic polyelectrolyte flocculated kaolin slurry as the common testing material. The two cells have different geometry and sidewalls construction materials. The sidewall friction could affect the percentage axial stress drop and the measured porosity across the cake, and also the specific resistance to filtration of the cake.
In this study, we investigated about the effect of the unsteady diffusion on the reaction rate of an immobilized catalyst in a batch type reaction system. Analyzing the diffusion and reaction under the unsteady state, we showed that true kinetic information can be obtained at the limiting condition of β → 0, where β is the volume ratio of the solid to liquid. For the definite value of β, we can derive an equation that expresses the relation between the apparent rate constant and β. This knowledge is valuable for studying immobilized catalyst kinetics.
The effect of nozzle geometry on maximum bubble penetration depth in a vertical liquid jet aeration system is investigated in relation to jet surface disturbance and air entrainment rate. The penetration depth decreases with increasing dimensionless nozzle length up to 15, but is constant with the dimensionless nozzle length above 15 for nozzles of contraction angle below 90°. The penetration depth is independent of the nozzle length for nozzles of contraction angle 90°. The effects of other parameters such as jet length and jet velocity on the bubble penetration depth were also evaluated, and an empirical correlation is presented for predicting the maximum depth of bubble penetration induced by a vertical liquid jet as a function of the operational conditions and nozzle geometry.
We quantitatively estimate the segregation indices in a continuous-flow stirred reactor (CSTR) on the basis of a unique parallel competing reaction scheme proposed by Villermaux and co-workers. Although the feed stream flow rate is much less than the circulation rate in the tank, the feed stream still markedly affects the micromixing efficiency.
NTO (3-nitro-1, 2, 4-triazole-5-one) crystals were obtained from NTO/H2O solution by a cooling method with ultrasound irradiation. The morphology and the size distribution of NTO crystals are found to be a strong function of ultrasound frequency and sonication time. The shape of NTO crystals with a 47 kHz sonicator is cubic or tetragonal. On the other hand, the shape of NTO crystals with a 28 kHz sonicator appears to be orthorhombic. The metastable zone width of the NTO/H2O system is observed to decrease under ultrasound irradiation. Ultrasound effect on the metastable zone width becomes dominant dramatically when the cooling rate is smaller than 0.5°C/min. In particular, at cooling rates smaller than 0.1°C/min, the limit of the metastable zone widths with ultrasound is about 2°C, independent of the saturation temperature.
In this study, a new methodology for surface modification of food fibers is proposed via a dry particle coating technology. Basically, in the dry particle coating processing, a mechano-chemical reaction between hydrophilic OH groups of food fiber and silanol groups—Si(OH)—on the surface of hydrophilic silica is used. As a result of this reaction, dehydration (H + OH → H2O) is expected, leading to suppression of the hygroscopic properties of food fibers for the purposes of better handling and enhancement of the preservative property. For the dry particle coating, a horizontal particle composite equipment with an ellipse shaped rotor was used. The surface of the food fiber was coated with a very fine hydrophilic silica (SiO2) and a mechano-chemical reaction was activated by a high shear stress and an impaction force in the equipment. The coated powders were prepared under various operating parameters of vessel rotational speed and operation time. The surface properties of the coated powders were evaluated by angle of repose (flowability), specific surface area, particle size, and a scanning electron microscopy (SEM) observation. The hygroscopic property was analyzed using a water adsorption method in a temperature and humidity controlled chamber. Interaction between OH and silanol groups was analyzed by a Fourier Transform Infrared Spectroscopy (FT-IR) method. As a result, the optimum operating conditions for preventing hygroscopic property of food fiber can be determined and the mechanism of the mechano-chemical reaction can be elucidated.
Voidage distribution along radial and axial directions in a cold flow semicircular fluidized bed 500 mm in diameter and 8000 mm in height was measured with a PC-4 optic fiber probe. The radial voidage profile is divided into jet and emulsion phase regions. The radial voidage profile in the jet region has an elliptic contour, but the voidage in the emulsion phase region is found to be equal to that under minimum fluidizating conditions. An empirical correlation for predicting the jet region voidage is proposed. The time series of pressure fluctuation are analyzed by deterministic chaos theory and power spectrum density function, and effects of jet gas velocity and static bed height on the correlation dimension and on major frequency are investigated. It is found that the major frequency (jet collapse frequency) increases with jet gas velocity. The results show that the correlation dimension increases with jet gas velocity. For a given jet gas velocity, the higher the static bed height, the greater the correlation dimension.
The effect of distributor type and geometry on the expansion of particles has been studied in a fluidized bed of 300 mm diameter and 800 mm deep. Four distributors were examined; three perforated plates, each perforated by holes of 0.8 mm in diameter but different hole densities at 6 mm, 9 mm and 12 mm pitch, and a porous plastic Vyon distributor 17 mm thick were examined. Particles of different materials in sizes were fluidized. 37 tubular inserts were held vertically as arrays in the bed. All experimental data for four distributors were correlated within experimental error by the equation:
Where U, Umf, U0 are the gas velocity, velocity at minimum fluidization and real or apparent terminal velocity, while e is the bed porosity and emf is the porosity at the condition of minimum fluidization. P is the hole pitch of perforated plate distributor in millimeters.
A fast-scanning X-ray CT system, designed for measuring dynamic events in multiphase fluids, was used to obtain the transient 2-dimensional cross sectional gas-phase distribution in a fluidized bed. The captured data was sent to a PC for image reconstruction, and the density distributions across the column cross section were visualized. Using image processing techniques, a pseudo 3-dimensional image of bubbles was obtained. The spatial and time resolutions of the system were sufficient for the measurement of ascending bubble behavior in a fluidized bed with fine particles. Bubble shape, interfacial area, and bubble holdup over the cross section can be measured by this system.
Shear viscosity of ceramic injection molding mixtures is predicted using the viscosity equation presented by Poslinski et al. (1988) for concentrated suspensions. The model was modified by taking into account the effects of the temperature and particles agglomeration on the viscosity. Alumina (Al2O3) and zirconia (ZrO2) powders were used for this study. The mean diameters of these powders are 0.5 and 0.43 μm, respectively. Low density polyethylene was used as a primary binder, and the powder was kneaded with the binder at a high solid concentration. The shear viscosity of the mixture was measured at various temperatures using a dynamic viscometry method with a cone and plate viscometer. The shear viscosity model presented in this study predicted well the viscosity data for non-agglomerated (Al2O3) and agglomerated systems (ZrO2) of the molding mixtures.
Based on analysis of wavelet transform, we studied how to extract the frequency band and multi-scale qualitative features of process measurement signals and proved that the extracted features could describe the process operating region stably and completely. Combining the pattern inductive algorithm, a new method of process operating region recognition based on wavelet transform is proposed. The theoretical analysis and real application results have verified that the proposed method is feasible and effective.
The utility of an immobilized enzyme, gluco-amylase on cellulose support, for the hydrolysis of potato starch, has been studied in a fixed bed biochemical reactor to evaluate the influence of flow parameters on conversion. The effect of parameters like pellet size, packed bed height and substrate concentration, has been studied. Maximum conversions are obtained for pellet size of 0.57 cm, packed bed height of 70 cm, and substrate concentration of 10 mg/ml. The kinetic behavior of heterogeneous enzyme, has been studied, with the aid of an appropriate mathematical model, which takes into account, simultaneous mass transfer and reaction kinetics. Based on the experimental observations and the mathematical model, intrinsic kinetic parameters are determined by decoupling diffusion effects. This knowledge is used in the design of an immobilized enzyme reactor.
The simple technique of extracting oxygen radicals anion (O–) from an anode of yttria stabilized zirconia (YSZ) by applying a low electric field has been reported (Torimoto et al., 1997, 2000). The reports suggest that the importance of a microstructure device could realize a highly energy-efficient production of O– at a low electric field, because the energy efficiency of O– production is defined to divide energy used for dissociation of oxygen molecule by input power (ε = const./V). Research on a microstructure device on a YSZ anode has been carried out. The new anode layer consists of a gold/SiO2/gold sandwich on a YSZ substrate having a regular array of open micron-sized pores. The typical film thicknesses of the sandwich are 1 micron, 5 micron and 1 micron from the top gold layer. Moreover, a major fraction of negatively charged species passing through the holes in the top electrode are collected by a relatively distant external electrode. By applying a few volts to the sandwich structure, oxygen radical anions were observed using a quadrupole mass spectrometer. It is, therefore, considered that the microstructure device on the YSZ anode will be a highly energy efficient device for producing O–.