bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prandtl number effect on combined free and forced laminar convection in the thermal entrance region of a horizontal tube
Authors: Chou F. C. , Hwang G. J. 
Published: March 2009

AbstractThis note presents the Prandtl number effect on combined free and forced laminar convection in the thermal entrance region of a horizontal tube by a numerical vorticity‐velocity method. The tube wall is heated with a uniform wall heat flux. Vorticity‐velocity governing equations in cylindrical coordinates and an evaluation of boundary vorticity on the tube wall are presented along with a numerical method of solution. Local Nusselt number variations are shown for Pr = 100 and 10 and compared with the existing data for Pr → ∞. It is observed that the large Prandtl number assumption is valid for Pr = 10 within a difference of 4% at Ra = 1 × 105. The numerical results are compared against the available experimental data with good agreement.
Flow and heat transfer characteristics of structural viscosity fluids
Authors: Gaidos R. E. , Darby R. , Wickern G. 
Published: March 2009

AbstractLaminar friction loss and heat transfer characteristics for a non‐Newtonian fluid described by a general viscosity function of the structural type have been computed for tube and slit geometries. The model includes most other models for fluids without a yield stress as special cases. The Graetz problem for constant wall temperature and temperature independent properties has been solved, including viscous dissipation, for the transverse and axial temperature distribution. Both momentum and energy transport characteristics are shown to be strongly dependent upon a dimensionless fluid time constant, which characterizes the transition from Newtonian to non‐Newtonian shear thinning behavior. A direct and exact analogy between the momentum and energy transport mechanisms is demonstrated for hydrodynamically and thermally fully developed flow, provided the heat transfer rate is represented by a suitably defined Nusselt number.
Solids circulation in a spout‐fluid bed with draft tibe
Authors: Berruti Franco , Muir James R. , Behie Leo A. 
Published: March 2009

AbstractA 20 cm diameter semi‐cylindrical spout‐fluid bed with a draft tube has been used to study the effects of operating and geometric parameters on the solids circulation rates at ambient temperature. A new technique has been developed for measuring the solids fluxes with great accuracy. Solids circulation rate data have been found to be strongly influenced by both geometry and relative magnitude of spouting and auxiliary gas flowrates, as they in turn affect the flow of the gas‐solid mixture inside the draft tube. The solids circulation rate was greatly enhanced when an auxiliary flow aerated the annular region and such enhancement has been found to be linearly dependent on the auxiliary flow contribution to the total gas flow and on the distance between the base of the draft tube and the inlet nozzle.
Enhancement of SO2 sorption on lime by structure modifiers
Authors: Shadman F. , Dombek P. E. 
Published: March 2009

AbstractThe presence of certain inert compounds in lime can improve the rate and the final limiting conversion significantly during the lime SO2 reaction. This physical effect is primarily due to modification of porosity. In particular, the enhancement appears to he due to increase in macro‐porosity and macro‐pore diffusivity; this in turn increases the sulfation rate and decreases pore plugging. In certain lime application processes, these compounds (structure modifiers) can be added to lime as beneficial additives to promote the reaction. Experimental data on the effect of kaolin, silica and bauxite as structure modifiers are presented. A theoretical model is developed which explains the observed effects both qualitatively and quantitatively.
Gas holdup in a bubble column with immikible liquid mixtures
Authors: Bandyopadhyay N. , Ray P. , Dutta B. K. 
Published: March 2009

AbstractExperimental measurement of gas holdup was carried out in a medium‐size gas‐liquid‐liquid bubble column with a multiple nozzle sparger plate using air, water and organic liquids. It was found that the fractional holdup depends on gas velocity, liquid properties, phase inversion in the liquid mixture as well as spreading coefficient of the organic liquid. In the presence of a liquid with a negative spreading coefficient the holdup is a minimum at the phase inversion point. but the reverse is true for a liquid with a positive coefficient of spreading. Observed bubble characteristics have been discussed. Correlations for gas holdup have been developed for different ranges of liquid composition.
Comparison of indices for the scaling and corrosion tendency of water
Authors: Müller‐Steinhagen H. M. , Branch C. A. 
Published: March 2009

AbstractThree commonly used fouling indices to characterize the scaling and corrosion tendencies of water, namely the Saturation Index, the Langelier Saturation Index and the Ryznar Stability Index, have been compared and checked for consistency. While the first two indices give similar results, major deviations between the predictions of saturation and stability indices were found.
An agitated bubble column for use in potash flotation
Authors: Karolat W. H. , Hill G. A. 
Published: March 2009

AbstractA novel, agitated bubble column was designed, constructed and operated for the purpose of potash flotation. This report describes the apparatus and presents some typical results regarding bubble size distribution, gas hold‐up and flotation efficiency.It was found that the column produced mean bubble diameters and overall gas hold‐ups that could be predicted by empirical correlations presented earlier in the literature for aerated, agitated tanks. The column also achieved both a high percentage recovery ( > 90%) and a high product purity (97%).
Gas absorption rates in a stirred cell with plane interface in the presence of fine particles
Authors: Quicker G. , Alper E. , Deckwer W.‐D. 
Published: March 2009

AbstractThe rates of absorption of carbon dioxide into water and into 0.5 mol/L equimolar carbonate buffer solutions (containing varying amounts of arsenite) were measured in a stirred cell with plane interface in the presence of fine solids (activated carbon, kieselguhr and alumina). Experiments show that the absorption rate increases significantly when the activated carbon loading increases up to about 0.2 g/L and thereafter remains constant. No significant effects were observed for other solids. The results could be explained in terms of a “shuttle” mechanism where particles adsorb gas near the interface which is then followed by desorption (or reactions) in the bulk.At very high loadings (above 10 vol.%), the absorption rate decreased for all particles and this could be explained by the blockage of the interface and/or by the sharp increase in the suspension viscosity.
Toxicity of organic solvents to fatty acid forming bacteria
Authors: Hayward Gordon , Lau Isaac 
Published: March 2009

AbstractThe inhibition of fatty acid formation in the anaerobic digestion of synthetic swine manure by several solvents has been studied. The solvents tested were commonly used for the recovery of acetic acid from dilute aqueous solutions. Negligible inhibition was observed with kerosene and tri‐octyl phosphine oxide. The latter compound was added as a carrier to increase the solubility of fatty acids in the organic phase. The most toxic solvent tested was di‐isopropyl ether with Aliquat 336 added as a carrier. The use of published oralLD50values for rats was found to provide a qualitative estimate of the bacterial inhibition by a solvent when divided by the water solubility of the solvent.
Hydrodynamics of erosion of heat exchanger tubes in fluidized bed combustors
Authors: Bouillard J. X. , Lyczkowski R. W. , Folga S. , Gidaspow D. , Berry G. F. 
Published: March 2009

AbstractThe hydrodynamics of fluidization for two thin “two‐dimensional” fluidized beds, one containing a centrally located rectangular obstacle and the other containing three square tubes roughly approximating a portion of a fluidized bed combustor (FBC), was solved using the FLUFIX/MOD2 computer program. The monolayer energy dissipation erosion model extended to include solids viscous stress was compared with the Finnie erosion model. The material properties of the eroding surface are introduced through the hardness for both erosion models. Hydrodynamic and erosion convergence studies were performed for the first bed. Computed erosion rates from the monolayer energy dissipation erosion model compare more favorably for both beds with available erosion data than those from the Finnie erosion model.
Vertical pneumatic conveying of particle plugs
Authors: Konrad K. , Totah T. S. 
Published: March 2009

AbstractDense‐phase pneumatic conveying of solids offers many advantages over dilute‐phase conveying. The lower air velocities, and, consequently, lower particle velocities, result in lower pipe wear and lower particle attrition. This paper describes an experimental program that has been undertaken to study the flow pattern of cohesionless solids in vertical transport and to measure the parameters influencing the pressure drop required to move a single plug of solids. Highspeed photographic techniques have been used to observe the flow pattern of polyethylene particles (diameter ≏ 3 mm) in the vertical riser section of a circulating unit constructed from pipes with an internal diameter of 50.8 mm. The flow pattern resembles that of square‐nosed slugging in a fluidized bed. The solids move up as “plugs” of bulk solids that occupy the entire cross‐section of the pipe. Particles are seen to “rain” down from the back of one plug and then to be collected by the front of the next plug. Collecting these particles causes a stress on the plug front which is transmitted by powder mechanics forces axially through the plug and radially to the wall. The pressure drop required to move a single plug of cohesionless solids through the transport pipeline was measured as a function of the plug length, particle properties, pipe diameter, and the frontal stress. The results of these experiments are compared with a theoretical model.
Heat transfer in a liquid‐liquid spray column
Authors: Lin F. , Ford J. D. 
Published: March 2009

AbstractA theoretical and experimental study of direct contact heat transfer in a kerosene‐water spray column has been carried out. A mathematical model for the process with a drop size distribution is proposed, and the associated computer program for the numerical solution developed. Correlations for the overall area heat transfer and axial dispersion coefficients for the column were obtained.Applying the mathematical model with experimentally obtained parameters, temperature profiles of both phases could be predicted. Comparisons with previous work in the literature support the present study. From the results, operation with uniform drop size in a short column is recommended.
Experimental studies of heat transfer to horizontal tubes in a pilot‐scale fluidized‐bed combustor
Authors: Bardakci Tevfik , Molayem Benjamin 
Published: March 2009

AbstractExperimental data are obtained for the overall heat transfer coefficient between immersed horizontal tube bundles and an atmospheric fluidized bed combuster burning high‐sulfur coal. Limestone (1000 μm size) is used as the bed material. Tests are conducted with coal and limestone addition at overall average bed temperatures ranging from 1028 to 1116 K, and fluidizing velocities ranging from 2.08 to 3.14 m/s. The overall heat transfer coefficients of the horizontal tube sections increase as the height from the distributor plate increases, except for the top tubes located in the splash zone. The average overall heat transfer coefficients of all horizontal tube sections increases as the fluidization velocity and overall bed temperature increase.
Hydrodynamically induced gel breakdown in pipes
Authors: Viswanathan T. , Khilar Kartic C. 
Published: March 2009

AbstractA new model is reported to describe the dynamics of hydrodynamically induced breakdown of oil gel in pipes. Hitherto, the reported models (Davenport and Somper, 1971; Govier and Fogarasi, 1972; Rao et al. 1985a) cannot predict some observed inherent features of the breakdown process relating to its rates. The present model can predict these desiderata as well as delineate the effects of microscopic parameters such as size and shape of wax crystallites on the dynamics of breakdown. The model is based on a concept that energy imparted to the gelled structures is consumed in the breakdown process. Predictions of this model on breakdown time agree reasonably well with measurements. Important considerations relating to the amount of pressure head required for different diameters of pipe as well as for different dimensions of crystallites are analysed using this model.
A study of ionic transfer in electrodialysis process with laminar flow
Authors: Huang Ting‐Chia , Wang Jun‐Hsien 
Published: March 2009

AbstractThe concentration profile in a laminar flow of the diluent of a parallel‐plate electrodialysis stack is derived by assuming operation at the limiting current density. The Nusselt mass transfer number is found to depend on the Reynolds number, the Schmidt number and the dimensionless hydraulic equivalent diameter according to (Nu)theo. = 3.7 · (Re · Sc · de/L)1/3. An empirical correlation of the Reynolds number, the Schmidt number, and the shape factor of the electrodialysis cell, with the ionic mass transfer rate in ion exchange membrane electrodialysis is obtained by measuring the limiting current densities at various conditions. The resulting empirical mass‐transfer correlation, (Nu)exp. = 3.91 · Re0.333 · Sc0.328 · (de/L)0.352, holds for sodium acetate as dialysate at concentrations ranging from 0.0106 to 0.0508 kmol/m3, viscosities ranging from 0.608 to 0.926 mPa · s, temperatures ranging from 15 to 55°C, axial velocities ranging from 0.341 to 4.55 cm/s, and for cell thicknesses of 0.32 and 0.94 cm, and is found to be in agreement with the equation obtained from theory. The effects of concentration, flow rate and temperature on the limiting current density are also studied. The relationship between the thicknesses of the diffusion layer and the Reynolds number has been analyzed.
Modelling of catalytic naphtha reformers
Authors: Bommannan D. , Srivastava R. D. , Saraf D. N. 
Published: March 2009

AbstractA simple kinetic model has been used to simulate catalytic naphtha reformers. The model idealises naphtha to three constituents, namely, paraffins, naphthenes and aromatics, with average properties assigned to each class. Out of the many reactions the mixture can undergo, four major reactions have been considered for which the kinetic parameters have been estimated using plant production data. The reactor model is validated against two different sets of plant data. The agreement between predicted results and observations is generally good. A sensitivity analysis of operating parameters on reactor performance revealed that, while temperature affects the aromatics production significantly, the effect of pressure is negligible.
Olefin conversion over zeolite H‐ZSM‐5
Authors: Norval G. W. , Phillips M. J. , Virk K. S. , Simons R. V. 
Published: March 2009

AbstractThe conversion of propene, 1‐butene and 2‐methylpropene over zeolite H‐ZSM‐5 has been studied in the temperature range 663–773 K. While propene and 1‐butene yield similar products, that from 2‐methylpropene contains less aromatics, but a greater fraction of xylenes. The time on stream behaviour of the aromatics from this latter olefin demonstrates that the difference in product yield and selectivity is due to pore mouth blockage resulting from the formation of iso‐butyl cations on the external zeolite surface.
Liquid solidification in low peclet number pipe flows
Authors: Lee S. L. , Hwang G. J. 
Published: March 2009

AbstractThe combined effects of axial conduction and solidification on heat transfer and pressure drop in pipe flows are investigated by the use of a modified Galerkin finite element method. To allow for the upstream heat conduction, the domain of study is extended from X = ‐∞ to X = ‐∞ as has been done in previous analyses. As a preliminary study on the effect of axial conduction, the present investigation assumes a superheat ratio that is sufficiently large (To > Tf or Tw ≈ Tf) such that solidification begins at a location near X = 0. For numerical convenience, the infinite domain ‐∞ ≤ X ≤ ∞ is transformed onto a finite domain ‐1 ≤ z ≤ 1. The energy equation for the liquid‐phase is then solved by a modified Galerkin finite element method. For better numerical stability, a procedure is proposed for controlling the numerical error that might propagate from the singular point (X, R) = (O, Ro). The profile of the solid‐liquid interface, the heat transfer rate and the pressure drop are presented for various values of Peclet number, Pe = 1, 3, 5, 10 and 30, and for the modified superheat ratio, c = 0.1, 0.5, 5.0, and ∞.
Novel pilot plant technique for sizing gas absorbers with chemical reactions
Authors: Tontiwachwuthikul Paitoon , Meisen Axel , Lim C. J. 
Published: March 2009

AbstractA new procedure, called the Novel Pilot Plant Technique (NPPT), for designing gas absorbers with chemical reactions is proposed. The technique is based on the premise that full‐scale absorption columns can be sized by making a minimum number of tests using small‐scale pilot plants. Two special features of the technique are that (i) detailed design parameters (such as mass transfer coefficients, reaction kinetics, physical properties) need not be known and (ii) complex calculations are avoided. The validity of the technique is demonstrated for the CO2‐NaOH system, for which the absorber height can be calculated accurately from first principles.
Studies of the fischer‐tropsch synthesis on a colbalt catalyst. III. mechanistic formulation of the kinetics of selectivity for higher hydrocarbon formation
Authors: Sarup B. , Wojciechowski B. W. 
Published: March 2009

AbstractMechanistic models are derived to quantify selectivity in the Fischer‐Tropsch synthesis. The models are fitted to experimental selectivity data obtained on a cobalt catalyst and are found to give a satisfactory fit. Results show that branching reactions can be explained by assuming a rate limiting 1‐2 hydrogen shift. For small molecules the 1‐2 shift takes place on one site, whereas larger molecules need an adjacent sit for the shift to take place. The “break” arises from the sum of two Anderson‐Schulz‐Flory distributions arising on two different locations.
On chemical equilibrium of pseudo‐one‐element systems: Application to oligomerization
Authors: Norval G. W. , Phillips M. J. , Missen R. W. , Smith W. R. 
Published: March 2009

AbstractFor a chemical system involving reacting species (such as oligomers) whose molecular formulae are of the form [(E1)a1 (E2)a2 … (EM)aM]n, where E is an element, both the equilibrium distribution and sensitivity analysis can be computed as for a one‐element system. The resulting simplification means that the former requires the solution of a single polynomial equation, and the latter allows explicit calculation of the relevant sensitivity coefficients. The treatment is illustrated for the catalytic oligomerization of olefins.
Blood, guts and chemical engineering
Authors: Sefton Michael V. 
Published: March 2009

AbstractBasic chemical engineering sciences have been used to address selected medical problems. The natural anticoagulant, heparin, has been immobilized to a polyvinyl alcohol (PVA) coating on polyethylene or polyurethane, to prepare a blood compatible material. Modelling of the relationship between the rate of heparin leakage from the coating and the blood heparin concentration at the blood material interface supported the conclusion that the observed inhibition of clot formation induced by the material was due to the activity of the covalently immobilized heparin. The relationship between flow resistance and tube diameter was used to devise an ex vivo system for demonstrating this activity: 1 mm ID heparin‐PVA coated tubing was tested in a parallel flow circuit with a 3 mm ID silicone tubing so as to control the blood flow through the 1 mm test tubing. In another area of chemical engineering activity in biomedical sciences, live mammalian cells have been microencapsulated in a polymer membrane to prevent the host's antibodies, that are outside the capsule, from causing the immune destruction of the to‐be‐transplanted cells (e.g., pancreatic islets for the treatment of diabetes). These works illustrate the use of chemical engineering in nontraditional ways, consistent with what some consider the new “paradigm” for our profession.
Heat transfer in turbulent forced convection between parallel‐plates
Authors: özisik M. N. , Cotta R. M. , Kim W. S. 
Published: March 2009

AbstractThe thermal entry region heat transfer due to turbulent forced convection of a Newtonian fluid inside a parallel‐plate duct maintained at constant uniform temperature is solved analytically and the local Nusselt numbers are determined with a high degree of accuracy up to the region very close to the inlet. The calculated local Nusselt numbers are compared with those obtained from a recently proposed empirical correlation.
Solubility of H2S, CO2 and their mixtures in an AMP solution
Authors: Teng T. T. , Mather A. E. 
Published: March 2009

AbstractThe solubility of H2S, CO2 and their mixtures in a 3.43 molar solution of 2‐amino‐2‐methyl‐1‐propanol (AMP) has been determined at 50°C at partial pressures between 4 and 5650 kPa. A mathematical model has been used to correlate the data for the individual gases in the solvent. The parameters obtained have been used to predict the partial pressures in the four‐component system. In general the predicted values are in good agreement with the experimental data.
Flow regimes and mass transfer in counter‐current bubble columns
Authors: Uchida S. , Tsuyutani S. , Seno T. 
Published: March 2009

AbstractCounter current bubble columns have the feature that specific gas‐liquid interfacial area and gas holdup are larger than those for standard and cocurrent bubble columns. In this study, three different flow regimes, churn‐turbulent flow, bubble flow and bubble down‐flow, have been observed in a counter‐current bubble column and correlations of gas holdup and volumetric liquid‐phase mass transfer coefficient have been proposed as functions of operating variables such as the superficial velocities of gas and liquid, the gas‐liquid slip velocity and the liquid properties.
Mass transfer in electrochemical reactors employing gas evolving mercury pool cathodes
Authors: Sedahmed G. H. , Ahmed A. M. 
Published: March 2009

AbstractThe effect of H2 evolution on the mass transfer coefficient of the cathodic reduction of potassium ferricyanide at a mercury cathode was studied with the aim of (i) comparing the mass transfer behaviour of a Hg cathode with that of solid electrodes under gas evolving conditions, and (ii) testing the effect of surface active agents on the mass transfer behaviour of a H2‐evolving Hg cathode. For a given H2 discharge rate the mass transfer coefficient at a mercury cathode was much higher than the value at a solid cathode. The mass transfer coefficient at the H2‐evolving Hg cathode was found to decrease in the presence of Triton X‐100 surfactant by an amount ranging from 62.6% to 86.2% depending on H2 discharge rate and surfactant concentration. A simple mathematical model was formulated to explain the results. The presence of surfactant was found to increase the cell voltage.