bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of helical impellers by circulation times
Authors: Guérin P. , Carreau P. J. , Patterson W. I. , Paris J. 
Published: March 2009

AbstractMeasurements of the circulation time during batch mixing of Newtonian and non‐Newtonian fluids were used to analyse and compare the performance of six different helical‐ribbon impellers and a screw impeller inside a draft coil. The distribution of circulation times obtained from two hundred repeated measurements is shown to depend markedly on the impeller geometry. Mixing time data with the helical‐ribbon impellers are correlated with the mean value and the reduced standard deviation of the circulation times. Effective (rapid) mixing corresponds to a large circulation capacity and a wide distribution of the circulation times. The mixing mechanism of Newtonian fluids with the helical‐ribbon impellers is qualitatively described by the Voncken model.The helical impellers' circulation capacities are not affected by the shear‐thinning properties of non‐Newtonian fluids. However, in highly shear‐thinning fluids, the presence of important stagnant zones is responsible for much longer mixing times which consequently do not correlate with the circulation parameters.The relative efficiencies of the different impellers in Newtonian fluids are compared using a criterion based on the the total energy required to achieve a certain degree of mixing. The wide blade impeller is the most efficient of the helical‐ribbon impellers but is considerably less efficient than the screw impeller in a draft coil.
Forced convection heat transfer to a power‐law fluid in arbitrary cross‐section ducts
Authors: Lawal Adeniyi , Mujumdar Arun S. 
Published: March 2009

AbstractA numerical method is developed to predict the three‐dimensional forced convection laminar incompressible flow of a power law fluid in arbitrary cross‐section straight ducts. The continuity equation and boundary layer forms of the energy and momentum equations in rectangular coordinates are transformed into new orthogonal coordinates with boundaries coinciding with the coordinate surfaces. The resulting equations are solved using the finite difference technique.The numerical scheme is capable of handling different hydrodynamic and thermal entry boundary conditions but results are only presented for uniform inlet velocity and temperature profiles and isothermal wall.To demonstrate the wider applicability of the method local heat transfer coefficients and pressure drop in square, trapezoidal and regular pentagonal ducts are computed as functions of pertinent thermal and hydrodynamic parameters.
The continuous flash pyrolysis of biomass
Authors: Scott Donald S. , Piskorz Jan 
Published: March 2009

AbstractA continuous atmospheric pressure flash pyrolysis process for the production of organic liquids from cellulosic biomass has been demonstrated at a scale of 1–3 kg/hr of dry feed. Organic liquid yields as high as 65–70% of the dry feed can be obtained from hardwood waste material, and 45–50% from wheat straw. The fluidized sand bed pyrolysis reactor operates on a unique principle so that char does not accumulate in the bed and treatment of the sand is not necessary. The product gas, about 15% of the yield, has a medium heating value. The liquid product is an acidic fluid, which pours easily and appears to be stable. A preliminary economic analysis suggests that if the pyrolysis oil can be used directly as a fuel, its production cost from wood waste is probably competitive with conventional fuel oil at the present time.
Prediction of flow pattern for the co‐current flow of gas and non‐newtonian liquid in horizontal pipes
Authors: Chhabra R. P. , Richardson J. F. 
Published: March 2009

AbstractPrevious work on delineating flow patterns for the horizontal two‐phase flow of gas and Newtonian liquid is briefly described. One of the flow pattern maps has been slightly adjusted to take account of the evidence from more recent studies. It is shown that physical properties of the system have relatively little influence on flow regime. It is then established that this map is also applicable when the liquid shows shear‐thinning non‐Newtonian properties.
Transfert de l'oxygène dans l'eau à température et pression élevées étude cinétique en réacteur agité par la méthode au sulfite
Authors: Foussard Jean‐Noel , Debellefontaine Hubert , Besombes‐Vailhe Jean 
Published: March 2009

AbstractThis paper examines the rate of absorption of molecular oxygen in an aqueous solution of sodium sulphite as a function of temperature over the range of 20–240°C. First, we determined the effect of the various parameters (oxygen partial pressure, sulphite and catalyst concentration, agitation) on the enhancement factor,E.It was observed that an Arrhenius' type relationship could describe the dependence of the physical absorption rate on temperature. According to the degree of agitation, two values for the activation energy: 22.8 and 12.7 kJ · mol−1are obtained. Our results validate the various models formerly proposed only for the range 10–40°C, but show that they cannot be extrapolated above 50°C. The results also show that a simple test at ambient temperature can be used to predict the oxygen transfer capability of a reactor at temperatures up to 240°C.
An experimental investigation of minimum fluidization velocity at elevated temperatures and pressures
Authors: Nakamura Masaaki , Hamada Yoichi , Toyama Shigeki , Fouda A. E. , Capes C. E. 
Published: March 2009

AbstractMinimum fluidization data at elevated temperatures and pressures are relatively scarce in the literature. This study was undertaken to provide some new data under these conditions. Minimum fluidization velocities at temperatures up to 800°K and pressures up to 5 MPa were measured for uniformly‐sized glass beads with diameters between 0.2 mm and 4 mm in beds ranging in diameter from 30 mm to 50 mm. The experimental results are compared with a number of empirical correlations from the literature to determine the validity of the correlations under these elevated temperature and pressure conditions.
Correlations for bubble characteristics in fluidized beds
Authors: Viswanathan K. 
Published: March 2009

AbstractFor fluidized bed reactors the available equations for superficial bubble velocity (UB), bubble fraction (δ), and absolute bubble rise velocity (ub) do not include bed diameter as a variable. Based on the gross solid circulation model new expressions are derived for UB, δ, and ub which explicitly account for bed diameter. Existing data are compared to predicted values from these correlations.
Dynamic simulation of a multicomponent distillation column with asymmetric dynamics
Authors: Stathaki Anna , Mellichamp Duncan A. , Seborg Dale E. 
Published: March 2009

AbstractThe dynamic behavior of an existing industrial distillation column with eight components and twenty trays has been investigated. The column exhibits “asymmetric dynamics”, since the time required to move from one steady state to another can vary significantly depending on the direction of the change. The column also exhibits highly nonlinear behavior and very long response times for intermediate ranges of step disturbances. These long response times are associated with the migration of key components through the column.
Shear‐Thinning effects on dip coating
Authors: Tanguy P. , Choplin L. , Fortin M. 
Published: March 2009

AbstractThe dip coating operation with shear‐thinning fluids is simulated by the Augmented Lagrangian Method coupled to a finite element discretization. Numerical predictions of coating thickness and meniscus shape compared with experimental data exhibit a very poor agreement. The discrepancy of results is explained by the inadequacy of shear‐thinning rheological models to describe the dynamics of the coating process in a non‐purely viscometric situation and also by the presence of a weak level of elasticity in the fluids used.
Modelling and adaptive control of fed‐batch penicillin fermentation
Authors: Montague G. A. , Morris A. J. , Wright A. R. , Aynsley M. , Ward A. 
Published: March 2009

AbstractThis paper describes a study to investigate the application of state estimation and parameter adaptive control in fed‐batch fermentation for penicillin production. A model of the penicillin fermentation process is outlined and shown to be capable of matching industrial data. The penicillin mould biomass is controlled to a reference trajectory by applying self‐tuning control to an estimate of biomass, obtained from measurements of carbon dioxide production rate and fermenter volume and by using the fermentation model with an extended Kalman filter. The manipulated variable, sugar feed to the fermenter, is calculated by an adaptive algorithm. Simulation results compare the performance of self‐tuning control with that obtained using digital Proportional plus Integral control.
The metabolism of lidocaine in the liver: Steady‐state and dynamic modelling
Authors: Saville B. A. , Gray M. R. , Tam Y. K. 
Published: March 2009

AbstractThe elimination of the drug lidocaine by the liver was modelled as a chemical reactor system, using data from in‐vitro tests of liver metabolism. A network of reactions, based on the known metabolic pathways, was used to account for the observed concentrations of drug and reaction products in steady state. The rates of reaction were substantially higher than in a liver homogenate, and some pathways showed considerable variation between individual livers. The steady‐state behavior of the liver was consistent with a well‐mixed reactor. The dynamic behavior could only be represented by including the additional mechanisms of enzyme deactivation and binding of drug to liver tissues.
Mixed‐culture microbial protein from waste sulfite pulping liquor II: Its production on pilot‐plant scale and use in animal feed
Authors: Lo S. N. , Moreau J. R. 
Published: March 2009

AbstractThis paper describes a pilot plant system set up to produce a mixed‐culture biomass having a very high content of protein (43%), for use in animal feed. Waste liquor from sulfite pulping was used as substrate. Conversion of carbohydrates in the said liquor to biomass was carried out in a 1200‐liter, nonaseptic, aerated, continuous flow tank fermentor. Fermentation conducted at pH = 6.5 gave rise to better settling of microorganisms than at the other pH's studied. The air input was a very important factor affecting fermentor productivity. Under the operating conditions used, the results for carbohydrate conversion, BOD5 reduction, biomass yield coefficient, and productivity were respectively, 90%, 85%, 0.53 kg/kg, and 3.67 kg/(m3d). With respect to the whole production system, operating and/or control problems were identified and useful technical data were collected in view of an eventual industrial implantation.The final product consisted of about the same varieties of microorganisms (yeasts, bacteria and microfungi) obtained in our previous work, Its nutritive qualities were not affected by the scale‐up of fermentor, i.e., from the previous 400 liters to the present 1200 liters. Animal feeding experiments were conducted using 240 chickens fed 4 diets. At least 50% of the soybean protein in commercial diet could be replaced with the biomass protein, without creating a significant effect on growth performance, on the health status of animals examined ante‐mortem and post‐mortem, and on the organoleptic quality of chicken meat.
Prandtl number effect on combined free and forced laminar convection in the thermal entrance region of a horizontal rectangular channel
Authors: Chou F. C. , Hwang G. J. 
Published: March 2009

AbstractA numerical method employing an axial‐direction vorticity function and three velocity components is applied to study the Prandtl number effect on the combined free and forced laminar convection in the thermal entrance region of a horizontal square channel. The channel wall is heated with a uniform heat flux. Local Nusselt number variations are shown for Rayleigh numbers Ra = 104, 3 × 104, 6 × 104 and 105 with the Prandtl number as a parameter. It may be concluded that the large Prandtl number assumption is valid for Pr = 10 when Ra≤104 but for a larger Prandtl number when the Rayleigh number is higher.
High alcohol synthesis from CO and H2 on ruthenium catalysts
Authors: Chen Yu‐Wen 
Published: March 2009

AbstractA Ru/MoO2 catalyst was found to be active for the synthesis gas conversion to straight chain primary alcohols. Potassium carbonate was effective for enhancing high alcohol formation. The carbon number distribution of the alcoholic products followed the Anderson‐Schulz‐Flory distribution which gave chain growth probabilities of 0.27–0.35. In addition, the Ru/MoO2 catalysts are significantly more sulfur resistant than a Ru/Al2O3 catalyst. The higher sulfur resistance of these catalysts is mainly due to their higher sulfur adsorption capacities.
Measurement of particle movement in a spouted bed using a new microprocessor based technique
Authors: Waldie B. , Wilkinson D. 
Published: March 2009

AbstractA new experimental technique for measuring particle cycle times, times of occurrence of particles at different levels, and particle velocities in the spout of a spouted bed is described. A magnetized marker particle and search coil or coils are employed together with a microprocessor system for ease of data collection and processing. The magnetic particles have the same diameter, density and similar surface texture to bed particles to ensure proper representation.Data is presented on distributions of cycle time and particle velocity and implied particle mass circulation rates at different levels in a spouted bed. Comparisons are made with photographic and laser–doppler anemometry techniques.
A mathematical model for the dehydrogenation of methylcyclohexane in a packed bed reactor
Authors: Touzani A. , Klvana D. , BÉLanger G. 
Published: March 2009

AbstractA model for the dehydrogenation of methylcyclohexane in a tubular reactor over an industrial catalyst Pt‐Sn/Al2O3 has been established. This model takes into account the axial dispersion at the inlet of the catalytic bed reactor as well as the heat transfer at the wall of the reactor. The heat transfer at the wall is satisfactorily represented by using a heat transfer coefficient correlation for which the parameters are obtained by fitting to the experimental data. The model provides a good representation of the radial and axial temperature profiles in the packed bed and can be also used to calculate the conversion.
Permanent jet formation in beds of particulate solids
Authors: Grace J. R. , Lim C. J. 
Published: March 2009

AbstractThe simple criterion proposed by Chandnani and Epstein (1984, 1986) for stable spouting, dor/dp ≤ 25.4, is shown to give a good separation between gas‐solid systems which form permanent jets and those that bubble, for a wide range of experimental data reported in the literature. The criterion is suggested as a necessary but not sufficient condition for permanent jet formation in fluidized, spout‐fluid and spouted beds.
Axial mixing and scaleup of reciprocating plate columns
Authors: Karr A. E. , Ramanujam S. , Lo T. C. , Baird M. H. I. 
Published: March 2009

AbstractAxial mixing measurements in single phase (water) flow have been taken in open‐type reciprocating plate columns of diameters 25.4 and 508 mm. In the case of the smaller column, two‐phase axial mixing was measured, both in the dispersed phase (water dispersed in n‐heptane) and the continuous phase (with n‐heptane dispersed in water). Pulse injection of a tracer solution of ammonium chloride and methanol in water was used.Under single phase conditions, the axial dispersion coefficients were found to go through a minimum as the agitation level was increased from zero. The coefficients were nearly an order of magnitude higher in the 508 mm column than in the 25,4 mm column. In two phase flow in the 25,4 mm column, the continuous phase axial dispersion coefficients also went through a minimum as agitation was increased. The dispersed phase axial dispersion coefficients decreased monotonically as agitation was increased from zero. The results of this work and previous data are used in modelling the scale‐up of reciprocating plate columns by means of Pratt's simplified technique. The existing empirical scale‐up equation is consistent with an assumption that continuous phase mixing increased with column diameter but dispersed phase mixing remains unchanged.
Study of a novel uniflow cyclone design
Authors: Sumner R. J. , Briens C. L. , Bergougnou M. A. 
Published: March 2009

AbstractA 5 cm diameter scale‐down model of a new uniflow cyclone for the ultra‐rapid fluidized (URF) reactor with a gas residence time under 20 milliseconds has been tested at high solids loading (5/1 wt. solids/wt. gas) under cold modeling conditions. The body length, gas exit diameter and amount of gas withdrawn with the existing solids (gas underflow) were varied to obtain high separation efficiency (over 99.9%). Silica sand of 55 and 105 micrometer Sauter mean diameter was used. Grade efficiency curves were determined for several specific configurations to get a deeper understanding of the mechanisms influencing the separation.
Solids mixing kinetics and segregation in a vibrostabilized fluid bed
Authors: Beeckmans J. M. , Chu J. C. H. 
Published: March 2009

AbstractThe vibration‐induced reduction in internal mobility of a fluidized bed, which was reported in a recent paper (Beeckmans and MacWilliam, 1986), has been confirmed using a larger bed. It has now been found that above a particular fluidization velocity internal mobility is not affected by vibrations. Distributor grid geometry was found to have a small effect on the fluidizing gas velocity at which bubbles are first observed at the surface of the bed, but it had an insignificant effect on solids mixing rates. The extent of segregation at steady state was reduced by vibrations with both flotsam and jetsam tracer particles.
A mixing model for diagnosing reacting tracers and tracing reactants in chemical and biochemical processes
Authors: Tanner Robert D. , Debelak Kenneth A. , Rohani Sohrab , Dunn Irving J. , Bourne John R. 
Published: March 2009

AbstractIt has previously been shown (Tanner et al., 1985) that biochemical and chemical reaction processes of the Type A → B → C can lead not only to kinetic hysteresis between the rate of formation of C and the concentration of species B in batch processes, but also hysteresis between those variables in a closed, imperfectly mixed (two zone) batch reactor. Furthermore, crossplotting the intermediate reactant, B, in one region of the poorly mixed reactor against B from the other major region leads to a clockwise hysteresis curve which is defined by both its area and the coordinate phase angle. This paper shows that the earlier analysis (Tanner et al., 1985) can be extended to the more general system A → B, where A in one region of the vessel is crossplotted against A measured in the other region. With an initial concentration of A* in one zone equal to its highest concentration, the inscribed area double‐valued crossplot of A, uniquely defines the system in terms of the inter‐vessel flowrate to reaction rate constant ratio, D/k.
Experimental investigation of cocurrent two‐phase flow in a vertical rectangular channel
Authors: Moujaes S. , Dougall R. S. 
Published: March 2009

AbstractNew time averaged data of two‐phase flow in bubbly and slug regimes are presented. A modified dual spherical tipped optical fiber probe is used to measure local void fractions, gas velocity and bubble sizes. Hot film anemometry was used to measure the local mean liquid velocity axially. The void fraction, gas and liquid velocities values were presented as averages over the long and short dimensions respectively. Also core values of these variables are presented along the smaller dimension of 12.7 mm, near the plane of symmetry of the longer dimension, to show the most general trend of the different bubbly and slug flow runs. Bubble sizes obtained experimentally were compared with predictive models applied to circular geometries and were found to have a reasonable agreement. It was also interesting to find that local void fractions measured using hot film anemometers were comparable to those found by optical fiber probes.Frequencies of interfacial passage of bubbles and slugs are presented which show rather flat profiles across the channel. It is hoped that these data can be further used in predictive two‐phase two‐fluid models in the future. Lastly of interest is the fact that slip values near the boundaries were shown to be less than 1.0 for some cases in bubbly flow similar to those observed in circular geometries.
Motion of a two‐phase bubble through a quiescent liquid
Authors: Wanchoo R. K. , Raina G. K. 
Published: March 2009

AbstractThe motion of a two‐phase bubble in immiscible liquids is associated with the development of three‐phase heat exchangers applicable for heat transfer at low driving forces.An analytical expression for the instantaneous velocity of a two‐phase bubble moving through a quiescent, less viscous, immiscible liquid has been developed. This expression predicts, very well, the available experimental data over the whole operational range of temperature and initial drop diameter.
Formation and growth mechanism of porous, amorphous, and fine particles prepared by chemical vapor deposition. Titania from titanium tetraisopropoxide
Authors: Kirkbir Fikret , Komiyama Hiroshi 
Published: March 2009

AbstractThe formation and growth mechanism of porous, amorphous, and fine particles were investigated. TiO2 particles were produced in a tubular flow reactor by a chemical vapor deposition technique using titanium tetraisopropoxide as a starting material at low temperatures (573‐973 K) and atmospheric pressure. Prepared particles were of submicron size and had large surface area (as large as 270 × 103 m2/kg). According to the proposed mechanism, reactions begin on the reactor wall and then the primary particles form in the gas phase by chemical reactions. The primary particles collide, coalesce with each other and grow. However, significant experimental deviations from the Brownian collision and coalescence theory imply that other processes, such as the surface reactions on the particle, play an important role in the growth, in addition to coalescence. Intraparticle reactions decreased the surface area by filling the pores.
On the determination of kinetic parameters for the regeneration of cracking catalyst
Authors: Morley K. , De Lasa H. I. 
Published: March 2009

AbstractIn the study of the regeneration of cracking catalyst, two approaches may be taken when determining the kinetic rate constant for the coke combustion reaction. A global coke burning rate equation may be considered, based on the observed oxygen concentration and carbon dioxide to carbon monoxide molar product ratio. This reaction may also be represented by an intrinsic coke burning equation which is a function of the oxygen concentration and the carbon dioxide to carbon monoxide molar ratio at the reaction site, combined with a carbon monoxide postcombustion equation. It is proposed in this paper that the rate constant for intrinsic coke burning, kc, is essentially equal to the global coke burning rate constant, kc, and that its value is independent of the rate equation chosen for the carbon monoxide post‐combustion reaction.
Prediction of mass diffusivity of CO2 into bitumen
Authors: Mehrotra Anil K. , Garg Anju , Svrcek William Y. 
Published: March 2009

AbstractThe infinite dilution and mutual diffusion coefficients for the CO2/bitumen system were predicted using existing correlations. Out of seven semi‐empirical correlations tested, the Umesi‐Danner correlation was found to be best suited for the prediction of gas‐liquid infinite dilution diffusion coefficient. For the mutual diffusion coefficient, Teja's method based on the generalized corresponding states principle was successfully used. The predictions are compared with the limited CO2/bitumen diffusivity data available in the literature.