bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic modeling of ph electrodes
Authors: Hershkovitch Hugo Z. , Mcavoy Thomas J. , Liapis Athanasios I. 
Published: March 2009

AbstractA mathematical model for the dynamic behavior of the pH glass electrode is presented. The model results from a description of ionic transport in an assumed stagnant boundary layer around the electrode surface. Documented information regarding the characteristics and operation of the glass electrode and the mechanism of pH measurements is combined with dynamic mass balances in an attempt to describe its transient response. New experimental results are presented which indicate both the validity of the model and that double layer effects are also contributors to the dynamic response. One of the interesting features of the model is that it predicts that if an electrode is subjected to a step change from a solution of a strong acid at a given pH to another solution of the same acid at the same pH but containing a salt of that acid, a transient response will result. This effect has been observed experimentally and is due to the differences in the diffusivities of the various ionic species present in the solutions.
Drop size distribution for spray by full cone nozzle
Authors: Sada Eizo , Takahashi Katsuroku , Morikawa Kazuhiko , Ito Shigeru 
Published: March 2009

AbstractExperiments were carried out to measure the drop size distribution in the spray produced by a full cone nozzle. At the center of the spray the distribution has one peak that can be expressed as a logarithmic normal distribution function. However, the distribution at other part of the spray has two peaks. Here it can be expressed as the sum of two distribution functions. At the vertical distance of 50 cm from the nozzle and the radial distance of 20 cm from the center of the spray, the geometric mean diameters of the first and the second peak are 61 and 235 μm, respectively, for an injection pressure of 294 KPa. For the same condition, the logarithmic standard deviations of the first and the second peak are 2.08 and 2.40, respectively. At the same position in the spray the geometric mean diameter varies in proportion to —0.2 power of injection pressure and the logarithmic standard deviation does not depend on injection pressure.
A mathematical model for concentric horizontal capsule transport
Authors: Van Den Kroonenberg H. H. 
Published: March 2009

AbstractFor designing capsule pipeline systems the designer needs preferably simple mathematical models, to make quick calculations of the main characteristics of the system. For this purpose an easy to handle mathematical model for horizontal concentric capsule flow is proposed. In this model separate friction coefficients for the moving capsule wall and the pipe wall are introduced. These friction coefficients can be taken from the Moody chart. In the model only relatively long capsules are considered so that end effects can be neglected. The model gives expressions for the capsule velocity and the pressure difference across the capsule. Test results are in good agreement with the proposed model.
Conditions needed for satisfactory measurement of mass transfer coefficients, internal diffusivity and adsorption rate constants
Authors: Gangwal Santosh K. , Hudgins Robert R. , Silveston Peter L. 
Published: March 2009

AbstractConditions are developed for the accurate measurement of mass transfer coefficients, internal diffusivity and adsorption rate constants using pulse gas chromatography within the limits of the approximation of the Kubin‐Kucera model for adsorption in a packed bed. Physisorption rates are shown to be many orders of magnitude higher than those measurable. Thus, pulse chromatography cannot be used to determine physisorption rate constants. Mass transfer coefficients at low Reynolds Numbers are shown to be measurable under severely restricted conditions.
Characterization and methanation activity of supported nickel catalysts
Authors: Bhatia S. , Bakhshi N. N. , Mathews J. F. 
Published: March 2009

AbstractThe methanation of carbon monoxide was studied over various supported nickel catalysts in a fixed bed reactor in the temperature range of 250 to 400°C. The hydrogen to carbon monoxide ratio was kept higher than stoichiometric in order to avoid carbon formation. The catalyst particles had an average diameter of 80 pm and nickel contents ranging from 5 to 42 wt %. The performance of laboratory prepared catalysts was compared with commercial ones. The catalysts were characterized by BET surface area, pore volume and carbon monoxide chemisorption. Specific activities for the methanation reaction were obtained and were found to vary with nickel concentration and with crystallite size. There exists a crystallite size range in which the maximum activity was observed. Metal support interactions may also contribute to the vdation in specific activity. The activation energy was found to vary from 58.2 MJ/kmol to 119.4 MJ/kmol. It appears that the methanation reaction over Ni/aIumina catalysts is a structure sensitive reaction. A compensation effect was observed for this reaction.
Volume reaction model for pyrolysis of a single solid particle accompanied by a complex reaction
Authors: Fan Liang‐Shih , Fan L. T. , Tojo K. , Walawender W. P. 
Published: March 2009

AbstractA fairly general model is proposed for the pyrolysis of a single solid particle accompanied by consecutive reactions. The model not only takes into consideration the transient heat transfer, mass transfer, and chemical reaction simultaneously but also the functional dependencies of various parameters on the variation of the solids concentration and temperature in the particle. The effects of the heat of reaction, Thiele modulus, and rate of reaction on the solids reactant conversion, concentration profiles and temperature profiles are analyzed and graphically presented.
Intermittent two phase flow in horizontal pipes: Predictive models
Authors: Nicholson M. K. , Aziz K. , Gregory G. A. 
Published: March 2009

AbstractA semi‐mechanistic model for two phase gas‐liquid slug flow proposed recently by Dukler and Hubbard has been modified and extended to apply to the entire intermittent flow regime. Flow predictions of the model proposed in this paper are compared with detailed experimental data recently obtained for an air‐oil system.The model requires the use of empirical correlations for the slug velocity and the in situ liquid volume fraction in the slug.In addition, either the slug frequencies or length corresponding to the given design conditions must be known. However, calculated values of average pressure gradient and in situ liquid volume fraction are relatively insensitive to these latter parameters, and in fact, good results are obtained assuming a constant slug length.The paper includes a discussion of the limitations of the proposed model and the expected direction of further study required to extend its mechanistic aspects.
Bubble formation in flowing liquid
Authors: Sada Eizo , Yasunishi Akira , Katoh Shigeo , Nishioka Masashi 
Published: March 2009

AbstractInitial bubbles in flowing liquid from a nozzle were observed from two mutually perpendicular directions. Two nozzles of 0.086 cm and 0.305 cm in diameter were used. The gas flow rate and the superficial liquid velocity ranged from 0.33 cm3/s to 36.2 cm3/s and from 0 cm/s to 154.9 cm/s, respectively.The bubble size formed in flowing liquid decreased with decreasing gas flow rate and with increasing superficial liquid velocity. Three types of bubble formation, i.e. single bubbles, coalescent bubbles and gas jets, were observed depending upon the gas rate and the liquid velocity. Two empirical equations of the bubble sizes are given.
Batch sedimentation of red mud suspensions in an inclined tube
Authors: Sarmiento G. , Uhlherr P. H. T. 
Published: March 2009

AbstractThe batch settling behaviour of lightly flocculated red mud in inclined tubes has been investigated experimentally. A simple model is proposed which describes the behaviour observed for this suspension better than models at present available from the literature. The new model is based on the Nakamura‐Kuroda equation into which a correction factor is introduced. For red mud, this factor is found to be a simple function of the angle of inclination and to be independent of solids concentration. This is in contrast to the various correction factors that have been proposed by other authors who have found strong and complex dependence on both solids concentration and angle of inclination. Thus, in the case of the suspension studied, the model represents considerable simplification of the description of inclined settling behaviour. The observed regimes of behaviour in inclined tubes are also discussed in the light of mechanisms observed in vertical settling for the same suspension.
Review of some useful rheological equations
Authors: Carreau P. J. , De Kee D. 
Published: March 2009

AbstractA variety of constitutive equations have been proposed in recent years to describe the behaviour of polymer solutions and melts. Rather complete reviews of most of the differential and integral equations proposed prior to 1967 have been given by Spriggs, Huppler and Bird(1) and by Bogue and Doughty(2,3). Since then, numerous efforts have been directed towards the development of equations capable of predicting adequately nonlinear and transient properties of polymer solutions and melts.Considerable information can be found in the recently published works by Bird et al.(4,5).Some of the more successful models are presented here in an uniform notation. The models are evaluated in terms of their ability to simultaneously describe some or most of the rheological functions such as the non‐Newtonian viscosity, the normal stress difference functions, the components of the complex viscosity, stress growth and stress relaxation.
A preliminary study of interfacial areas in vertical cocurrent, two‐phase upflow
Authors: Watson Alex P. , Cormack Donald E. , Charles Michael E. 
Published: March 2009

AbstractPseudo‐first order chemical absorption was used as the basis for determining the effective interfacial area available for mass transfer in gas‐liquid, cocurrent, upward pipe flow. The study, which was performed in a 2.54 cm I.D. tube, encompassed the slug and froth flow regimes.The interfacial area displayed a strong dependence upon the coordinates of the flow regime map proposed by Oshinowo and Charles(16). In addition, the systematic variation of surface area could be rationalized on the basis of flow regime geometry. Unfortunately the data could not be used to assess previous surface area models due to the unresolved diameter dependence of these models.Observations are also made concerning the apparently significant effect of chemical composition on interfacial surface area, and concerning the inadequacy of the popular methods used for estimating frictional pressure drop in vertical two‐phase flows.
The coalescence of n‐hexane droplets in aqueous solutions of n‐alcohols
Authors: Sagert Norman H. , Quinn Michael J. 
Published: March 2009

AbstractCoalescence times, measured by high speed cinematography, are reported for n‐hexane droplets formed and grown on adjacent nozzles in equilibrated aqueous solutions of ethanol, n‐butanol, n‐hexanol, n‐octanol, n‐decanol and n‐dodecanol. The drops remained attached to the nozzles throughout the coalescence process. Coalescence times increased when alcohols were added to the system. Very similar results were obtained for the alcohols n‐hexanol to n‐dodecanol. When these alcohols, which are much more soluble in n‐hexane than in water, were present, the observed coalescence times could be accounted for best by considering diffusion processes occurring in the n‐hexane. For ethanol and n‐butanol, which are more soluble in water, diffusion processes occurring in the water had to be considered as well.
Kinetics of sorption in bi‐porous molecular sieves — Part I. Mathematical models for systems with rectangular equilibrium isotherm
Authors: Lee Lap‐Keung , Ruthven D. M. 
Published: March 2009

AbstractThe coupled diffusion equations describing transport in a bi‐porous adsorbent (micropore‐macropore) have been solved in order to obtain the theoretical uptake curves for such a system when the adsorption equilibrium isotherm is rectangular. Solutions are presented for both the step change boundary condition generally encountered in adsorption from the gas phase and for the more complex case which is encountered in studies of adsorption from the liquid phase, when the composition of the ambient fluid changes significantly during the course of an experiment. The theoretical uptake curves are compared with the corresponding curves for a linear system.
Direct hydrogenation of hybrid poplar wood to liquid and gaseous fuels
Authors: Boocock D. G. B. , Mackay D. , Mcpherson M. , Nadeau S. , Thurier R. 
Published: March 2009

AbstractFast growing hybrid poplar suspended in water has been treated with hydrogen at temperatures of around 350°C and pressures of about 10 MPa (100 atm) in the presence of Raney‐nickel. Complete conversion of the wood to oil and gas has been achieved. The oils, which appear to derive predominantly from the lignin, contain about 10 percent oxygen and have heating values of up to 40.8 MJ/kg (17,550 BTU/Ib). The gas, which is mostly methane, appears to derive from the celluloses and contains no carbon monoxide. Treatment of purified cellulose yields only gases and water soluble organics.
Kinetics of the dehydrogenation of ethanol to acetaldehyde on unsupported catalysts
Authors: Peloso A. , Moresi M. , Mustachi C. , Soracco B. 
Published: March 2009

AbstractA kinetic study of the dehydrogenation of ethanol to acetaldehyde on an unsupported catalyst of base composition CuO – Cr2O3 was carried out in an isothermal reactor fed with ethanol 95% vol. in the temperature range 225–285°C with space velocities 1.5–7.5 LHSV at atmospheric pressure.The mechanism which was found suitable to describe the reaction was that of surface adsorption on dual sites.Taking into account interphase and intraphase diffusion, the observed conversions of ethanol were reconstructed with a standard error below 10%, thus confirming the validity of the physical assumptions.
Transport effects in the manufacture of reaction‐bonded silicon nitride
Authors: Hughes G. S. , Mcgreavy C. , Merkin J. H. 
Published: March 2009

AbstractThe transient behaviour of the exothermic, irreversible, silicon‐nitrogen reaction is analysed, using mixed type boundary conditions to represent external resistances. The mathematical model incorporates a sharp cut‐off reaction into the moving reaction zone, in the heat mass transfer field, and the resulting system of equations is solved numerically using an explicit finite difference scheme. Effects of varying the Thiele modulus, Prater temperature and Biot number are examined, together with the different geometrical effects. The results are graphically presented and interpreted.
The gravity clarifier as a stratified flow phenomenon
Authors: Cordoba‐Molina J. F. , Hudgins R. R. , Silveston P. L. 
Published: March 2009

AbstractA problem that has plagued the designers of gravity clarifiers is that of obtaining a uniform and stable flow field necessary for efficient sedimentation.Clarifier operation is a fluid problem which, up to now, has been viewed in terms of homogeneous fluid concepts. In this paper we show that by treating clarifier flow as stratified (i.e. a fluid with variable density), it is possible to obtain a uniform and stable flow field. If this flow condition can be realized in full‐scale units, it should provide significant increases in removal performance or clarifier capacity at a constant removal.
On the efficiency of a centrifugal fan wet scrubber
Authors: Nguyen X. T. 
Published: March 2009

AbstractAn inertial theoretical model is proposed to predict the capture of aerosol particles by accelerating liquid droplets in a centrifugal fan scrubber. The results are in good agreement with literature experimental data for micron and large submicron size particles. The theory tends to underestimate the scrubber performance for submicron size particles of less than 0.3 μm in diameter. The discrepancy may be due to the lack of a reliable expression predicting the diffusion deposition of aerosol particles on an isolated liquid droplet. The effects of variables such as fan speed, sizes of liquid droplets and particles, gas and liquid flow rates predicted by the theory are discussed and agree with literature observation.
Mixing in water elutriators
Authors: Biddulph Michael W. 
Published: March 2009

AbstractThis paper describes the results of an experimental and theoretical study of a water elutriator. An eddy mixing model is proposed and a photographic study of the behaviour of glass and plastic spheres in an operating elutriator appears to confirm the model. Values of the eddy diffusion coefficient are presented for a range of conditions. The correlation of the eddy diffusion values is encouraging, and the results will be useful in the design and evaluation of commercial elutriators separating solid species.
Stabilité de V2O5supporte sur SiO2, comme photocatalyseur de l'oxydation du cyclohexane
Authors: Nguyen D. L. , Roberge P. C. , Kaliaguine S. 
Published: March 2009

AbstractThe activity of Vanadium pentoxide supported on silicagel for the photocatalytic oxidation of cyclohexane has been studied. It was found that this catalyst presents a stable activity after an or decrease depending on the surface concentration of VOshrd initial unsteady state period during which the activity might increase or decrease depending on the surface concentration of V2O5. An interpretation is proposed for the two phenomena affecting the activity during the unsteady state period.
Simulation and design of distillation units for treatment of sulfite pulping condensates to recover methanol and furfural: Part II: Applicability of multiple‐effect distillation using live steam
Authors: Aly G. , Zacchi G. 
Published: March 2009

AbstractA distillation unit has been designed for a capacity of 73 t/h of condensate and for at least 90% recovery of the contaminating organics. This unit consists of three columns: a primary stripper to remove volatile organics and two upgrading columns to purify the methanol and furfural byproducts.Three different energy‐saving alternatives for satisfying the energy requirements have been studied: utilisation of secondary steam from the evaporation plant, and application of the principle of multi‐effect distillation in one‐stripper and in two‐stripper configurations.Investment cost needed in all alternatives amounts to 5.5–6.0 MCr (millions of Swedish Crowns) while operating cost varies between 0.8–3.1 MCr. The first design alternative has a payoff period of 2.3 years while the two multi‐effect distillation alternatives have a payoff period of about 3 years.
Foam fractionation of spent sulphite liquor: Part II: Separation of toxic components
Authors: Berk Dimitrios , Behie Leo A. , Zajic James E. 
Published: March 2009

AbstractFoam fractionation was used as a unit operation for the reduction of toxicity in spent sulphite liquor. Toxicity was measured quantitatively using a Daphnia magna bioassay. The optimum pH for the operation was 10 and no toxicity removal was possible at pH values less than 8. The maximum decrease in the toxicant concentration was 40%. The collapsed foam was very toxic to D. magna indicating that toxicants were concentrated in the foam which contained 20% of the original liquid charged to the column. A relationship between surfactant and toxicant concentration was shown to exist.
Behavior of tar sand bitumen with paraffinic solvents and its application to separations for athabasca tar sands
Authors: Funk Edward W. 
Published: March 2009

AbstractA study was made of the dissolution of tar sand bitumen using low‐molecular‐weight paraffinic solvents at essentially ambient temperatures. The experimental data were obtained using the spinning disc technique, liquid‐fluidized beds, and direct particle‐size analysis of the insolubles. The results are consistent with a mechanism where the paraffins leach the soluble oil from the bitumen and leave behind a porous network of insoluble asphaltenes. This phenomenon of oil diffusing through an asphaltene layer was modeled using Fick's law for unsteady‐state diffusion. An understanding of the mechanism of bitumen extraction with paraffins and also the effect of fluid mechanics in the tar sand system have been applied to obtain a novel separation of deasphalted oil and asphaltenes from Athabasca tar sands. This new separation technique has the potential of simplifying downstream processing for the bitumen and also of avoiding environmental problems associated with the present tar sand extraction technology.
A numerical technique for the estimation of critical constants and of Lennard‐Jones (12–6) parameters. Application to tetramethyl and tetraethyl compounds
Authors: Rummens Frans H. A. , Rajan S. 
Published: March 2009

AbstractA numerical technique is given which allows the estimation of critical constants from vapor pressures at any two temperatures and the liquid density at any temperature. It is shown that such a technique can also be used to test the accuracy of vapor pressure data. This method is applied to the compounds X(CH3)4 and X(CH2CH3)4, where X=C, Si, Ge, Sn and Pb. For these same molecules estimates are given for their σ and ϵ/k Lennard‐Jones (12–6) parameters, based on the calculated critical constants.
Transferring information from one experiment to another
Authors: Hoffman Terrence W. , Reilly Park M. 
Published: March 2009

AbstractThis paper presents a rational method (based on Bayes' Theorem) for transferring information on parameter values from one experiment to another, in situations where the mathematical models for the two experiments share some parameters in common. The uncertainty in the estimates of the parameters, which reflects the experimental error in the initial experiment, is properly transferred as well.The use of the method is demonstrated by applying it to a fairly complicated system, typical in chemical reaction engineering, in which the kinetic parameters in a model for the hydrogenolysis of butane reaction were estimated using data obtained from a bench‐scale, integral packed‐bed reactor. These parameter estimates were then transferred to a model for a fluidized bed reactor in which the same chemical reaction occurred. Using the fluidized bed data they were updated and two additional parameters in the fluidized bed model were also estimated. This procedure allows a more realistic estimate of the uncertainty in all parameter values in the model for the fluidized bed reactor.
Characteristics of a hydro‐filter pressure drop, liquid hold‐up and liquid overflow rate
Authors: Uchida S. , Sumiyama M. , Kageyama S. 
Published: March 2009

AbstractAn experimental study of the effect of operating conditions on the characteristics of a hydro‐filter (Marble bed scrubber) has been performed. There are stable operating regions of a hydro‐filter with respect to the gas flow rate, the packed bed height and the height of an overflow pipe above the bed.The total pressure is mainly composed of the pressure drops in two sections, the packed section and the bubble section. The pressure drop in the packed section can be estimated from the correlation for a cocurrent gas‐liquid upward flow packed bed given by Turpin ad Huntington.