bluuebunny/crossref_metadata_2025 huggingface dataset:
Vapor‐liquid equilibrium, excess gibbs energy and excess enthalpy of 1, 3 dioxolane‐methylcyclohexane at t = 313.15 k
Authors: Castellari Carlo , Francesconi Romolo , Comelli Fabio
Published: March 2009

Data on vapor‐liquid equilibrium and enthalpy of mixing HE are, obtained for the mixture 1, 3 dioxolane‐methylcyclohexane at 313.15 K (40.0°C). Correlation of the data is given by using Redlich‐Kister expressions and the excess functions GE = RT(X1 In γ1 + X2 In γ2) and TSE = HE ‐ GE are thereby calculated. A comparison is made between this mixture and those formed by 1, 3 dioxolane with cyclohexanol and cyclohexanone.
Mass transfer characteristics in a gas‐liquid reciprocating plate column. I. Liquid phase volumetric mass transfer coefficient
Authors: Skala Dejan , Veljković Vlada
Published: March 2009

In a series of two papers the results of investigating the mass transfer characteristics of two gas‐liquid reciprocating plate columns of the Karr type by different methods are presented. The subject of the first part is a study of the liquid phase volumetric mass transfer coefficient, kLa, while the second part deals with the interfacial area.

The volumetric coefficient kLa was investigated using the sulphite method, the pure physical absorption of oxygen, and a dynamic method under culture conditions, the second of these three methods being the most favorable.

Very good agreement among these methods was found. Generally, kLa increased with increasing vibration intensity, superficial gas velocity, and the number of perforated plates. Liquid‐phase properties appeared to affect kLa only slightly. The coefficient kLa was correlated in terms of the maximum power consumption and the superficial gas velocity:
The plasma production of ultrafine silica particles
Authors: Gans I. , Gauvin W. H.
Published: March 2009

A process for producing ultrafine silica particles incorporating a plasma transferred‐arc reactor of novel design (Plas‐macan) was developed. The process consisted of vapourizing small particles of sand (99.5% SiO2) which subsequently dissociated into SiO gas and oxygen in the presence of an argon plasma. Quenching of this gaseous mixture reconstituted SiO2 in the form of an aerosol. Various reacting media (H2, steam or NH3) were tested to assist the dissociation and to enhance the properties of the particles produced. The quenching of the particles was effected with oxygen or steam. A feedrate of 1.3 kg/h SiO2 and a power of 30 kW for plasma generation were used throughout the work. Amorphous silica particles, average 0.07 μm in diameter, were produced.
The effects of ferrous iron, dissolved oxygen, and inert solids concentrations on the growth of thiobacillus ferrooxidans
Authors: Liu M. S. , Branion R. M. R. , Duncan D. W.
Published: March 2009

The effects of suspended, inert solids concentration, ferrous iron concentration and dissolved oxygen concentration on the kinetics of iron oxidation by Thiobucillus ferrooxidans are reported. It is shown that the maximum specific growth rate for this organism, oxidizing ferrous iron, is of the order of 0.1 h−1. Competitive inhibition by femc iron is demonstrated. The dissolved oxygen concentration below which the bacteria will not grow is 0.20 mg/L. The dissolved oxygen concentration below which O2 availability is limiting is around 0.29‐0.7 mg/L. 10.4 millimols of CO2 are fixed by the bacteria per mol of ferrous iron oxidized. 0.0185 mg of bacterial carbon are generated per mg of O2 consumed. Comparative mass transfer rates for O2 and CO2 are discussed. Oxidation rates decreased significantly in shake flasks as suspended solids concentrations rose above 0.5%, whereas in stirred tanks solids concentrations up to 15% had little effect on oxidation rate.
Optimal temperature policies for catalytic transport reactors under periodic operation
Authors: Sivakumar S. , Chidambaram M. , Shankar H. S.
Published: March 2009

The influence of inlet gas concentration cycling on the optimal temperature policy of catalytic transport reactors is studied theoretically. The model considered is based on plug flow of gas and catalyst particles with negligible interand intra‐particle diffusional resistances and concentration dependent deactivation kinetics. To utilise the concentration of the reactant and the activity of the deactivating catalyst fully a proper temperature sequence along the reactor is needed. Thus, a general optimal temperature policy using the continuous minimum principle is derived for the reactor under periodic operation. The model equations are solved analytically for gas concentration, activity and temperature profiles. Resonance behaviour (maximum in conversion with pulse width) is obtained using the optimal temperature policy for certain sets of parameters. The effects of activation energy groups, reaction and deactivation constant groups and inlet temperature on the optimal temperature policy under periodic operation are evaluated. In all cases an improvement in conversion with the optimal temperature policy under periodic operation over that with an isothermal policy under periodic operation is obtained. A suboptimal policy, comprising constant temperature over different reactor sections, which is useful for implementation purposes is also discussed.
The effects of catalyst surface heterogeneity on the fischer‐tropsch synthesis
Authors: Rice N. M. , Hsu C. C. , Wojciechowski B. W.
Published: March 2009

We find that the surface energetic heterogeneity of Fischer‐Tropsch catalysts is either not important kinetically or may be masked by the effect of increasing molecular size, so that the classical Anderson‐Schulz‐Flory distribution is routinely observed in product distributions. The anomalous yields of C1 and C2 observed in many cases may also be due to surface heterogeneity but can in practice be readily, and more conveniently, accounted for by assigning individual rate constants to their formation.

The “break” sometimes observed in ASF distributions cannot be explained by surface heterogeneity and is best explained by the presence of two distinct modes of product formation.
The entry length for slurries in horizontal pipeline flow
Authors: Colwell J.M. , Shook C.A.
Published: March 2009

The entry length for horizontal slurry pipeline flows has been determined experimentally using a pipeline of diameter 50 mm. Concentration and velocity distributions have been measured in the vertical direction at positions 6, 50 and 185 diameters downstream of the entrance.

The measurements show that the entry length is of the order of 50 pipe diameters for sand slurries. High particle settling velocities give somewhat shorter lengths than intermediate settling velocities. With lower density polystyrene particles for which dispersive effects are important, the entry length is significantly greater than 50 diameters. The velocity distributions show that the velocity profiles develop concurrently with the concentration profiles. For sand slurries, a two‐dimensional simulation gives a satisfactory representation of the developing concentration profiles.
Role of the contact points between particles on the reactivity of solids
Authors: Hao Yu‐Jun , Tanaka Tatsuo
Published: March 2009

Through the exact number of contact points between the two components of a solids system, the reactivity of the solids is expressed in terms of the molar ratio, the particle size ratio and the nature of the reacting system. The theory is confirmed by existing experimental data, revealing that the contact points play an important role for wide ranges of reactivity of solids.
Process design for offshore oil and gas production in cold ocean environment
Authors: Sen D. C.
Published: March 2009

Many considerations influence the design of offshore oil and gas processing facilities such as type of platform, weight and space limitations, environmental conditions, government regulations, drilling support, enhanced recovery, and logistics of supply and market factors. Some of these factors have major impacts on the design and make offshore facilities different from those on land.

This paper discusses some typical case scenarios with particular emphasis on processing crude oil in a cold ocean environment such as the Grand Banks off Newfoundland or Beaufort Sea. It describes certain basic requirements for the process design on offshore platforms. Every design is unique for its particular situation.
Prediction of the thermal conductivity of liquids and liquid mixtures including crude oil fractions
Authors: Teja Amyn S. , Tarlneu Gilliane
Published: March 2009

A new method based on the Effective Carbon Number is presented for the prediction of the thermal conductivity of liquids and liquid mixtures. The Effective Carbon Number for each substance of interest can be calculated from its thermal conductivity at a reduced temperature of 0.6. The thermal conductivities of isoalkanes, cycloalkanes, aro‐matics, alkanes, carboxylic acids, ketones, esters and aldehydes over a range of temperatures were predicted using this method and the results were compared with experimental values. The thermal conductivities of defined mixtures were also predicted using a quadratic mixing rule for the Effective Carbon Number. Lastly, the thermal conductivities of undefined mixtures such as crude oil fractions were calculated by treating each fraction as a single pseudocompo‐nent. In all cases studied, calculated results compared favorably with experimental values.
The effect of steam temperature on the economics of a cogeneration power plant
Authors: Ham R. W. , Douglas P. L. , Fulford G.
Published: March 2009

Using steady‐state simulation, we have evaluated the effect of boiler superheat and reheat temperatures on the economics of the utility section of a Bayer Alumina Plant. These economics were compared with those of a steam plant which purchased power.

Under this study's nominal economic conditions, producing steam and purchasing electricity was the cheaper option. A sensitivity analysis showed that the cogeneration plant became the better choice when the local cost of electricity rose above 10C/kWh. The plant economics improved monotonically with superheat temperature as did the thermo‐dynamic efficiency. However, for reheat, the plant economics did not improve monotonically with temperature even though the thermodynamic eficiency did; thus improvement in the thermodynamic efficiency does not always yield improved economics.
On the effect of particle size on heat transfer in vertical upflow of gas‐solids suspension
Authors: Sivakumar S. , Chidambaram M. , Shankar H. S.
Published: March 2009

The occurrence of a minimum in heat transfer coefficient with particle diameter in a vertical upflow transport column as reported by Jepson et al. (1963) is explained by the minimum in total surface area of solid particles per unit volume of column with particle diameter. The minimum in the external surface area of solids in the column is shown to be due to the counteracting effects of increasing solids holdup with particle diameter and decreasing specific surface area of solid particles with increasing particle diameter.
On the numerical solution of differential algebraic equations
Authors: Audry‐Sanchez Javier
Published: March 2009

A method is proposed to transform a system of differential algebraic equations (D.A.E.) to a system of ordinary differential equations (O.D.E.) which can be solved relatively easily by standard numerical techniques.

Two examples, including a model of an absorption tower, are given to illustrate the utility of the method. The example problems reveal that this easily implemented technique offers significant savings in CPU time compared to the numerical solution of the untransformed D.A.E.s particularly when the algebraic equations are nonlinear.

Furthermore, it appears to be faster and/or more reliable than other numerical schemes which have been recently developed for equations of this type.
Studies on the inhomogeneous nature of the silent discharge reactor: Part 2. kinetic simulation of a differential batch reactor
Authors: Khan A. A. , Howarth C. R.
Published: March 2009

The silent discharge reactor is characterised by a large number of randomly distributed discrete primary reaction zones (PRZ). These are transient in nature. Primary electron‐molecule collisions take place here with subsequent quenching of the atom‐molecule or free radical‐molecule processes. A model of a differential batch ozonizer has been proposed to study the influence of various forms of current pulse train, and the chemical activity of dielectric surface. The effect of multiple exposure of the reaction products to a series of electron avalanches has been evaluated. Finally the effects of temperature field and electron concentration within the electron avalanches have been studied.
Mixing and combustion in a shallow coal‐limestone fluidized bed combustor
Authors: Ho T. C. , Kirkpatrick M. , Hopper J. R.
Published: March 2009

A model based on the Monte Carlo approach was developed to simulate the mixing and combustion behavior of a shallow coal‐limestone fluidized bed combustor. The model involved the coupling of two sub‐models: a combustion sub‐model based on the two‐phase concept of fluidization and a mixing sub‐model based on our previously developed dynamic mixing model.

The combustion sub‐model considered both the volatile and char combustion. It assumed that the combustor consisted of three distinct phases, i.e., jet, bubble and emulsion, with combustion occurring only in the emulsion phase. The mixing sub‐model considered the upward or downward movement of a coal particle in the bed as being governed by certain probability laws; these laws were, in turn, affected by the bubbling hydrodynamics.

In all, the combustor simulation model took into consideration the effects of coal feed rate, coal size distribution, limestone size, air flow rate and combustor temperature on the combustor behavior. The simulation results included the dynamic response of coal concentration profile, coal size distribution, coal particle elutriation rate as well as the mixing status between the coal and limestone particles.
Sedimentation of polydisperse concentrated suspensions
Authors: Al‐Naafá Mohammed.A. , Selim M. Sami
Published: March 2009

Gravity sedimentation of bidisperse and tridiperse concentrated suspensions have been studied both theoretically and experimentally. Experimental data were collected from batch settling tests using fully‐characterized colored spherical particles. Ten sizes of particles with three different densities were used in the sedimentation experiments. Varying proportions of each size were used and total solids concentration ranged from 13% to 45% by volume. Previously published and newly collected data were compared with predictions from six available models. These models include those of Lockett and Al‐Habbooby (1973), Mirza and Richardson (1979), Masliyah (1979), Reed and Anderson (1980), Selim et al. (1983a, 1983b), and Patwardhan and Tien (1985). Based on the present study and a similar study by Law et al. (1987) on bidisperse suspensions of heavy (sinking) and light (buoyant) particles, it is found that the Selim et al. model represents the data more accurately as compared to the other models.
Axial dispersion characteristics of three (liquid‐liquid‐solid) phase fluidized beds
Authors: Kim Sang D. , Lee Myung J. , Han Joo H.
Published: March 2009

The effects of the continuous and dispersed phase velocity and particle size on the axial dispersion of the continuous phase have been determined in two (liquid‐liquid) and three (liquid‐liquid‐solid) phase fluidized beds. In a cocurrent liquid‐liquid flow system, the axial dispersion coefficient increases with both the dispersed and continuous phase velocities. In three phase fluidized beds, the coefficient increases with dispersed phase velocity but it decreases with the particle size. Also the coefficient exhibits a maximum value with an increase in the continuous phase velocity at the lower dispersed phase velocities, but it increases with the continuous phase velocity at higher dispersed phase velocities. The axial dispersion coefficients in terms of Peclet number have been correlated in terms of the ratio of fluid velocities and the ratio of the particle size to column diameter, based on the isotropic turbulence theory.
Cyclone collection efficiencies at very high temperatures
Authors: Patterson P. A. , Munz R. J.
Published: March 2009

Experimental results for gas‐solid separations in a 102 mm diameter conventional cyclone operated with air heated to temperatures between 300 K and 2 000 K, are presented. Overall and fractional collection efficiencies were measured for alumina and silica having particle sizes of 100% less than 44 μm and mass median diameters of 5.0 and 10.0 μm respectively. Inlet velocities ranged from three to 42 m/s and inlet dust loads were between 0.3 and 235 g/m3. The dust load had a strong influence on the collection efficiency and the loading effect was stronger at high temperatures.
Generic model control — A case study
Authors: Lee P. L. , Newell R. B. , Sullivan G. R.
Published: March 2009

This paper outlines the use of a process model directly in a control algorithm. The process considered, a forced circulation single‐stage evaporator, is a nonlinear interacting process. The control strategy employing a process model derived from fundamental mass and energy balances is shown to outperform single loop and predictive control strategies by a significant amount. The control structure is first presented in general form and then specifically applied to this process.
Dynamic and pseudodynamic modelling of transient and periodic CSTR operation
Authors: Klusacek K. , Hudgins R. R. , Silveston P. L.
Published: March 2009

Using the simple catalytic reaction A+B°C, catalytic surface dynamics can be modelled either by assuming finite rates of adsorption and desorption (termed the dynamic model) or by assuming adsorption equilibrium between the gas and the surface (the pseudodynamic model). In general, the responses of the two models are quite different, the pseudodynamic model being unable to predict rate overshoot for reactor start‐up. Both models appear able to describe rate enhancement and simple (i.e. single frequency) resonance for forced feed composition cycling. Reasons for preferring the dynamic model over its pseudodynamic counterpart are discussed.
A similarity relationship for the pressure drop in vortex chambers
Authors: Vatistas G. H. , Lam C. , Lin S.
Published: March 2009

The paper focuses on the pressure drop across stationary and rotating chambers. The non‐dimensional pressure drop has been found to depend solely on a single dimensionless parameter which involves only geometric quantities. The finding is supported by past and present experimental evidence. The similarity relationship for the pressure drop is shown to be true for both types of vortex chambers. Based on the derived relationship and the experimental data, an empirical formula capable of predicting the pressure drop over a wide range of design conditions has been obtained using the least squares method.
Reconciliation of mass flow rate measurements in a chemical extraction plant
Authors: Holly W. , Cook R. , Crowe C. M.
Published: March 2009

Since measurements of flow rates in a steady state chemical process are subject to errors, the laws of conservation and other constraints are violated. Total mass flow data from a chemical extraction plant are used to determine whether the process operated at steady state and to estimate the variances of the measurements. The data are then reconciled so as to minimize the weighted sum of squares of the adjustments and to test for gross error. Deletion of either of two particular flow rates is shown to remove all of the apparent gross errors in the data.
Mass transfer from discrete gas bubbles in a reciprocating plate column
Authors: Baird M. H. I. , Rohatgi A.
Published: March 2009

Measurements have been made of the uptake of oxygen in water from a series of discrete bubbles released into a 5 cm diameter reciprocating plate column. The rate of increase of dissolved oxygen in the water has provided data on the average mass transfer coefficients under the following conditions; (a) free rise in the absence of plates, (b) bubbles rising through a static plate assembly and (c) bubbles rising through moderately agitated plates (frequency up to 1.28 Hz). It was found that the mass transfer coefficients were higher under condition (b) than (a), and were further increased under condition (c). The results were compared with earlier data on mass transfer to agitated bubble dispersions.
Derivation of performance equations for solid‐solid screens
Authors: Gooding R. W. , Kerekes R. J.
Published: March 2009

Equations relating efficiency of separation to reject loss of desirable material have been derived for solid‐solid screens. The derivations were based on the relative passage of particles through individual screen plate apertures and the extent of mixing on the feed side of the screen plate. Two limiting cases of mixing were considered: plug flow and mixed flow along the screen plate. Both barrier and probability screening were included in the analysis. The physical significance of the terms in the equations and the implications of their derivation were described in relation to wood pulp screening.
Non‐newtonian two‐phase circulation in bubble columns
Authors: Clark Nigel N. , Flemmer Rory L. C. , Van Egmond Jan W.
Published: March 2009

Gas‐liquid and gas‐slurry bubble columns are widely used in the mineral and engineering industries, particularly for aeration (oxidation), synthesis of oil and flotation of mineral fines. Even though gas may be introduced into a bubble column evenly through a distributor plate over the whole column floor, undesirable circulation patterns generally develop in the column. This paper extends a force balance approach (originally used for turbulent systems) to predict circulation in non‐Newtonian gas‐liquid mixtures and demonstrates how the rheological properties will affect a single circulation pattern in a column.
Gas‐liquid mass transfer in three‐phase fluidized beds with viscous pseudoplastic liquids
Authors: Schumpe Adrian , Deckwer Wolf‐Dieter , Nigam Krishna D. P.
Published: March 2009

Liquid phase volumetric mass transfer coefficients for oxygen were determined in three‐phase fluidized beds of 8 mm glass spheres fluidized by a cocurrent flow of air and pseudoplastic polysaccharide solutions (carboxymethyl cellulose, xanthan). A semi‐theoretical relation for the effective shear rate was suggested. The mass transfer coefficients could be correlated, together with literature data for particle diameters of 3 mm and 5 mm in other liquids, using the terminal velocity as the particle‐specific property.
Turbulent mixing in coflowing plane jets
Authors: Grandmaison E. W. , Zettler N. L.
Published: March 2009

The scalar mixing field of a single plane jet and an array of three coflowing plane jets has been examined using marker nephelometry. Results are reported for the centreline behaviour of the mean and fluctuation concentration fields of the single jet and the triple jet array with Gi/Go = 1.39, 0.222 and 0.089, where Gi is the centre jet momentum and Go the momentum of both outer jets. Details of the flow scales including the half concentration width and integral scales are also reported for the single plane jet and the triple jet case with Gi/Go = 1.39 and 0.089. The centreline measurements were extended to the region where a tendency to axisymmetric behaviour was observed.
Condensation of vertical plate fins of variable cross section‐limiting solutions
Authors: Sarma P. K. , Chary S. P. , Rao V. Dharma
Published: March 2009

The purpose of the present theoretical analysis is to provide explicit solutions for the problem of condensation of vapours on the lateral surface of a long vertical plate fin of variable cross‐section. The formulation yields solutions to the Limiting cases so that the results can be employed in the design of the condenser section of a flat plate heat pipe in which the fin is considered to be an essential element in transporting heat liberated by the condensing vapours. It is observed that the local and average Nusselt numbers depend on fin parameter, fin profile index, Rayleigh number and degree of subcooling.
Modelling the kinetics of fast catalytic cracking reactions
Authors: Collyer R. , Larocca M. , De Lasa H.
Published: March 2009

Instantaneous kinetic constants and gasoline selectivities have been determined for catalytic cracking of n‐hexadecane. The pulse technique was used in order to model the sequential build‐up of coke which occurs on cracking catalyst within a riser transport‐line reactor. The total amount of hydrocarbon injected per unit weight of catalyst was between 0 and 10. The mathematical model used to analyze the data was based on the unsteady state mass balance of the microcatalytic reactor with the assumption of plug flow. Results suggest a fast deactivation process during the run with fresh catalyst, while regenerated catalyst showed a slower deactivation. The catalyst regenerated three times evidenced a low apparent activation energy when temperature was increased from 500°C to 550°C.
Viscosity of cold lake bitumen and its fractions
Authors: Mehrotra Anil K. , Eastick Robert R. , Svrcek William Y.
Published: March 2009

New data are presented for the effect of temperature on the viscosity of bitumen fractions, which were obtained by vacuum distillation of a large Cold Lake bitumen sample. The viscosity of these fractions differs by several orders of magnitude; from 4.3 mPaϵs for Cut 1 to 430 000 mPaϵs for Cut 4 at 30°C. Cut 5 is a glass‐like solid at room temperature with a softening temperature of about 100°C, and has a viscosity of 800 000 mPaϵs at 120°C. The effect of temperature on the viscosity of each bitumen fraction is modelled very well with a two‐parameter correlation that was shown to be valid generally for Alberta bitumens. The results of bitumen viscosity calculations, based on a simple liquid‐mixture viscosity formula, are presented and compared with the bitumen viscosity data.
Natural convection from a radiating fin to thermally stratified medium of air
Authors: Sarma P. K. , Subrahmanyam T. , Rao V. Dharma
Published: March 2009

Integral analysis is used to study laminar natural convection from a vertical radiating fin situated in ambient air thermally stratified according to a power law variation of temperature. The phenomenon is treated as a coupled problem in which all the possible modes of heat transfer are accounted for in the constitutive equations. For stable thermal stratification of the medium, the local Nusselt is found to be a function of the radiation parameter, fin parameter, temperature ratio, stratification parameter, the exponent of the power law ‘m’ and the conventional Gr.Pr product. An approximate design relationship between the various parameters is established by the method of regression.
A multiobjective approach to the structuring of an efficient system for producing petrochemicals from alternative raw materials
Authors: Sokić Milorad , Zdravković Sonja , Trifunović Zoran
Published: March 2009

Previously reported data on the effects of the utilization of coal‐based raw materials within the petrochemical industry indicated a conflict between the objectives of efficient utilization of raw materials and energy in structuring an optimum system. The nature of this conflict was examined more closely by comparing system performances which refer to separate considerations of the conflicting objectives. The multiobjective approach was applied in order to generate compromise system structures and to determine the region in which the preferred compromise solution is to be found.
Particle slip velocities in air jets under atmospheric pressure and soft vacuum conditions
Authors: Bronet Murray S. , Boulos Maher I.
Published: March 2009

Laser Doppler anemometry (LDA) is used for the measurement of gas and particle velocities in an air jet under atmospheric pressure and soft vacuum conditions. The slip velocity between the particles and the carrier gas at the exit of a particle injection probe is shown to depend on the geometry of the probe tip. With a standard probe tip, the particle velocity lagged behind the gas velocity at the exit of the probe. The addition of a section with a sudden expansion at the downstream end of the probe, results in the rapid drop of the gas velocity at the exit of the probe without a corresponding drop of the particle velocity. The results show that the proposed probe tip configuration can be effectively used to achieve a positive particle slip condition at the exit of the probe, with the particle velocity equal to or higher than that of the carrier gas.
Catalyst modification and process design considerations for the oxidation of low concentrations of hydrogen sulfide in natural gas
Authors: Chowdhury A. I. , Tollefson Eric L.
Published: March 2009

Low concentrations of hydrogen sulfide (H2S) in natural gas can be selectively oxidized over an activated carbon catalyst to elemental sulfur, water and a small fraction of sulfur dioxide (SO2). Efforts to improve catalyst performance and product sulfur quality have been made by a) modification of the catalyst composition b) removal of the heavy hydrocarbons from the feed and c) choice of reaction conditions. The use of a guard bed to absorb heavy hydrocarbons and operation at elevated pressures show positive results. A preliminary flow diagram incorporating these findings has been prepared for a small commercial unit capable of processing sour natural gas containing 1.0% H2S.
Dispersed phase holdup and bubble size distributions in gas–liquid cocurrent upflow and countercurrent flow in reciprocating plate column
Authors: Sundaresan A. , Varma Y. B. G.
Published: March 2009

Dispersed phase holdup and the bubble size distribution were measured in a reciprocating plate column under cocurrent upflow and countercurrent flow of gas and liquid phases. The response of the system to a variation in design and operating conditions was found similar to that for liquid–liquid contacting; the magnitude of response, however, differed significantly between them.

Taking into consideration the dominant forces encountered in gas–liquid dispersions, the experimental data are satis–factorily correlated in terms of Froude, Weber and Gallileo numbers.
Laminar mixed convection in the thermal entrance region of horizontal rectangular channels with uniform heat input axially and uniform wall temperature circumferentially
Authors: Chou Fu‐Chu
Published: March 2009

This paper presents a numerical study on laminar mixed convection in the thermal entrance region of horizontal rectangular channels with uniform heat input axially and uniform wall temperature circumferentially. A relatively novel numerical method of solution is developed to obtain the developing velocity and temperature fields. The values of Prandtl number are 0.7 and 7.2, corresponding to air and water, respectively. The values of Rayleigh number are 0, 104, 3 × 104 and 105. The channel aspect ratios considered are 0.2, 0.5, 1, 2 and 5. Variations in local friction factor ratios and local Nusselt numbers are presented. It is found that the circumferential boundary condition of uniform wall temperature significantly increases the value of local Nusselt number as compared to that found in earlier works under the boundary condition of uniform wall heat flux. But the boundary condition effect on the friction factor is shown to be comparatively minor. The asymptotic solutions at z → are compared to the existing numerical data with good agreement.
Influence of particle size and particle/fluid combination on particulate fouling in heat exchangers
Authors: Blöchl R. , Möller—Steinhagen H.
Published: March 2009

The influence of particle size on particulate fouling rates during convective sensible heat transfer to liquids has been investigated. Experiments have been carried out using aluminum oxide particles with nominal diameters ranging from 0.06 μm to 15 μm, suspended in an organic solvent for a wide range of concentrations. The observed influence of particle size on the asymptotic fouling resistance is compared with the predictions of the Watkinson–Epstein model. The results of this comparison suggest that, in addition to the changes of mass transfer coefficient with increasing particle size, reduced adhesion forces between particles and wall and increasing removal forces have to be considered as well. Additionally, the influence of different particle/fluid combinations was investigated. Experiments were performed with aluminum oxide particles suspended in isopropanol, isobutanol or water, and with kaolin particles suspended in water.
A study of liquid molar volumes for some pure halogenated hydrocarbons and their binary mixtures
Authors: Ström Krister H. U.
Published: March 2009

Liquid volume data have been measured at compressed liquid conditions for four pure refrigerants, CCl3 F, CCl2 F2, CHClF2 and C2 Cl2 F4, and three mixtures, CCl2 F2/CCl3 F, CCl2 F2/C2 Cl2 F4, and CHClF2/C2 Cl2 F4. A comparison of measured data and data reported in the literature with calculated data by three methods is presented. The three methods are the Thomson‐Brobst‐Hankinson correlation, and two equations of state according to Carnahan‐Starling‐de Santis and Lee‐Kesler‐Plöcker. In general the Thomson‐Brobst‐Hankinson correlation shows a smaller deviation from experimental data than the two equations of state examined.
Mass flow rate prediction of a thermosiphon solar air‐heater
Authors: Tamimi A.
Published: March 2009

A flat‐plate solar air‐heater was analyzed and tested. A model was proposed to predict air mass‐flow rate at any operating condition. The model showed good agreement with experimental data.
Selective formation of 2‐methyl‐2‐butene and 2‐methyl‐1‐butene: Operating conditions and kinetic analysis
Authors: Chiesa G. R. , Perez C. F. , Orio O. A. , Ardissone D.
Published: March 2009

The effect of linear gas velocity, catalyst particle size, reaction temperature, space time, etc. on the dehydration of amyl alcohols (from fusel oil) was studied, using as catalyst a pre‐treated bentonite. The analysis of the kinetic data, using Hougen‐Watson type models, gives as the best model one in which amyl alcohol is absorbed on two active sites, the reaction rate being determined by the surface reaction of absorbed species.
Gas entrainment rate and flow pattern of vertical plunging liquid jets
Authors: Kusabiraki Daisuke , Niki Hidefumi , Yamagiwa Kazuaki , Ohkawa Akira
Published: March 2009

For a vertical plunging liquid jet system using various liquids, the effects of the operating conditions including the nozzle length‐to‐diameter ratio on the gas entrainment rate Qg were evaluated experimentally. The differences in Qg were related to the changes in the jet shape before plunging and the velocity of the plunging liquid jet at the point where the gas sheath breaks up. Empirical relationships were also presented to predict the maximum depth Z of bubbles entrained by the diffusing jet. The changes of Z were further discussed in terms of the downward liquid velocity distribution in the submerged two‐phase region, which depends mainly on the size of entrained bubbles.
A kinetic study of pyrolysis in pitch impregnated electrodes
Authors: Kocaefe D. , Charette A. , Ferland J. , Couderc P. , Saint‐Romain J. L.
Published: March 2009

Carbon electrodes impregnated with three different pitches have been studied and compared. The electrode samples were heated up to 893 K in a thermogravimetric analyser at different heating rates. The weight loss was recorded with respect to time and temperature. A special technique and a calculation procedure have been developed to handle the pitch dripping from the electrode at low temperatures. A kinetic model assuming a first order reaction rate was used to interpret the data. This paper presents the experimental technique and the results of the study. The model predictions are compared with the data which shows a good agreement.
Long range predictive control of a polymerization reactor
Authors: Inglis M. P. , Cluett W. R. , Penlidis A.
Published: March 2009

This paper examines the application of generalized predictive control (GPC), one in the class of long‐range predictive algorithms, to the control of conversion of methyl methacrylate (MMA) monomer in a simulated CSTR, and to the control of temperature in a pilot plant batch polymer reactor. The control objective is regulation in the presence of (i) stochastic disturbances due to impurities (in the case of the CSTR), and (ii) pulse disturbances from the addition of cold solvent and initiator (in the case of the batch reactor). The role of the observer polynomial as a detuning parameter for trading off performance against variability in the control action is emphasized. Also, the role of data prefiltering, prior to model parameter estimation, is examined. A frequency domain interpretation of the least squares estimation algorithm is used to clarify the role of the filter.
Nonlinear predictive control using multi‐rate sampling
Authors: Bequette B. Wayne
Published: March 2009

A nonlinear predictive control (NLPC) strategy based on a nonlinear, lumped parameter model of the process is developed in this paper. A constrained optimization approach is used to estimate unmeasured state variables and load disturbances. Additional model/process mismatch is handled by using an additive output term which is equivalent to the Internal Model Control approach. Similar to linear predictive control methods, an optimal sequence of future control moves is determined in order to minimize an objective function based on a desired output trajectory, subject to manipulated variable constraints (absolute and velocity).

Deadtime is explicitly included in the model formulation, giving NLPC the same deadtime compensation feature of linear model‐predictive techniques. The multi‐rate sampling nature of most chemical processes is also used to improve estimates of process disturbances. Infrequent composition measurements in conjunction with frequent temperature measurements are used to improve the “inferential” control of the composition in a continuous flow stirred tank reactor (CSTR).
Hydrodynamics of a vibrating perforated plate extraction column
Authors: Rao N. V. Rama , Vijayan S. , Baird M. H. I.
Published: March 2009

Hydrodynamic behaviour of several liquid‐liquid systems has been measured in a 5 cm diameter extraction column agitated by finely perforated plates vibrating at frequencies (f) 10–100 Hz and amplitudes (a) 0.024–1.5 mm. The Sauter mean droplet diameter is generally in the range 0.1 to 1 mm. It has been correlated empirically with af2, system properties and operating conditions. Dispersed phase holdup, when plotted against the product af, showed minimum values corresponding to the transition from mixer‐settler to emulsion regime. Holdup was also found to be affected by mass transfer and its direction. Entrainment of fine droplets in the continuous phase occurs at high agitation levels, but can be reduced by the addition of coalescence plates at the base of the column. Energy dissipation rates greatly exceed predictions from the quasi‐steady‐state model.
Impingement heat transfer under a confined slot jet. Part II: Effects of surface motion and throughflow
Authors: Polat S. , Mujumdar A. S. , Douglas W. J. M.
Published: March 2009

Local and average heat transfer coefficients were measured for a confined turbulent slot jet impinging on a moving surface at which there may be throughflow. Profiles of the local convective coefficient at the impingement surface were obtained using a fast responding, highly sensitive porous heat flux sensor. The decrease in average heat transfer with surface motion is not negligible, ∼20%, at values of the surface motion parameter, Mvs, comparable to those used in industry. The enhancement of heat transfer by throughflow at a moving impingement surface is linearly additive and, when expressed as δSt, is proportional to only the throughflow parameter, Mus, with a proportionality constant of 0.17 which is independent of Re, Mvs or extent of the heat transfer surface.
Salting out crystallization of sodium sulfate
Authors: Mina‐Mankarios George , Pinder Kenneth L.
Published: March 2009

The growth and nucleation rates of sodium sulfate crystals salted out from their solution in a 38% w/w sulfuric acid solvent by the addition of an 80:20 w/w methanol:water solution, were determined from measurements of the steady‐state crystal size distribution (CSD) generated in a continuous mixed‐suspension, mixed‐product‐removal (MSMPR) salting out crystallizer. The effects of the supersaturation, the crystal suspension density and the temperature on these rates were investigated. The effect of the Cr+++ impurity was also briefly studied.

The growth rate kinetic order g was determined to be essentially unity. The nucleation rate kinetic order b was determined as 2.11. The corresponding kinetic rate constants KG and KB were fitted to an Arrhenius type temperature dependence to give.

KG = 43960 exp(‐24600/RT)

and

KB = 0.064 exp(70900/RT)

where R is in kJ/kmol · K. An increase in chromate impurity concentration caused an increase in the growth rate constant KG but had no significant effect on the nucleation kinetics.

The kinetiics of crystallization as determined for this system would indicate that a high temperature, high crystal suspension density and long residence time are conditions which are favorable for the production of large sodium sulfate crystals.
On the use of approximate velocity profiles for modeling multiphase reactors
Authors: Zimmerman William H. , Bukur Dragomir B.
Published: March 2009

The use of an approximate axial gas velocity profile in a two‐phase reactor model has been studied. The approximate velocity was assumed to vary linearly with conversion, which reduces the number of differential equations to be solved. The approximate model was studied in systems with one or two reactions. In most cases, the approximate and rigorous solutions were in good agreement. However, when mass transfer strongly influenced the velocity profile, errors in conversion became significant (∼ 15%). Reactions with no change in the number of moles are also subject to errors if the rigorous velocity profile is not accounted for.
Deactivation of cracking catalyst in short contact time reactors: Alternative models
Authors: Kraemer D. , De Lasa H. I. , Larocca M.
Published: March 2009

Several mathematical models have been used to describe the deactivation of cracking catalysts by coke. For the case of gas oil cracking under short contact times (less than 20 seconds) it was found, using data from two different experimental reactor units, that an exponential decay function or a power law function could equally represent the data. Both functions are forms of the general hyperbolic decay expression; however, the power law assumes the unrealistic limits of infinite catalyst activity at zero time‐on‐stream and requires two parameters to describe deactivation. This work shows that the simple first order decay function is an effective equation to be used in describing catalyst activity decay for short reaction times.
Nutrient and metabolite gradients in mammalian cell hollow fiber bioreactors
Authors: Piret J. M. , Devens D. A. , Cooney C. L.
Published: March 2009

This work has investigated high density CRL‐1606 hybridoma cell culture in the shell‐side of ultrafiltration hollow fiber bioreactors. Oxygen depletion was measured in the recycle stream, and has been identified as the critical, axial scale‐limiting factor in these reactors. The composition of the extracapillary space has been studied by rapidly freezing these reactors in liquid nitrogen to recover samples of the shell‐side environment. The accumulation of inhibitory metabolites should have only a marginal impact on growth and product formation of this hybridoma cell line. Oxygen depletion is expected to be the major limiting factor for both the axial and radial scale‐up of hollow fiber bioreactors.
Modelling of addition polymerization processes — Free radical, ionic, group transfer, and ziegler–natta kinetics
Authors: Ray W. Harmon
Published: March 2009

A brief review of addition polymerization processes is presented with a summary of the key characteristics classified by kinetic mechanism (free‐radical, anionic, cationic, group transfer, or Ziegler–Natta), phase behavior, and reactor type. A practical approach to modelling in the industrial R & D environment is discussed in terms of a CAD package for polymerization processes.
Hydrodynamics of disturbed flow and erosion–corrosion. Part II — Two‐phase flow study
Authors: Nešič S. , Postlethwaite J.
Published: March 2009

Erosion–Corrosion in turbulent, two‐phase liquid/particle flow with recirculation, after a sudden pipe expansion is studied by the application of a numerical flow model along with two different erosion models. The flow model, which is based on a two‐phase flow version of a standard two‐equation model of turbulence and a stochastic simulation of particle‐fluid turbulence interactions, is capable of successfully predicting local values of time averaged fluid velocities and turbulent fluctuations, as well as predicting particle dispersion and particle‐wall interaction. The erosion models used are that of Finnie (1960) and a modified version suggested by Bergevin (1984).

The agreement of the predicted and measured hydrodynamic parameters, for flow through a sudden expansion, was satisfactory. Predictions of erosion rates using Bergevin's modified model were in good agreement with the stainless steel erosion measurements for a 2% water/sand slurry flow. The erosion–corrosion model was successful in predicting the overall pattern and rates of metal loss for carbon steel.
Hydrodynamics and mass transfer in an upward venturi/bubble column combination
Authors: Huynh L. X. , Briens C. L. , Large J. F. , Catros A. , Bernard J. R. , Bergougnou M. A.
Published: March 2009

The hydrodynamics and mass transfer characteristics of a venturi/bubble column combination were studied at high liquid superficial velocities of up to 0.35 m/s. The gas hold‐up was increased by 50% to 150% and the overall volumetric mass transfer coefficient was tripled when the venturi was used as “gas distributor” instead of a porous distributor. A correlation of the overall volumetric mass transfer coefficient (KLa) with the gas hold‐up, valid for gas hold‐ups as high as 0.3, was proposed for the cylindrical bubble column section. The energy consumption per mole of oxygen transferred was lower than with most distributors and the oxygen transfer rate per unit of reactor volume was higher than in a bubble column with a porous distributor. The venturi/bubble column combination is a compact and efficient system which does not have the operating problems of systems which require internals.
An experimental study of motion of cylinders in newtonian fluids: Wall effects and drag coefficient
Authors: Unnikrishnan A. , Chhabra R. P.
Published: March 2009

The terminal velocity of several cylinders (of glass, perspex and stainless steel) falling with their axis parallel to the direction of motion has been measured in a series of Newtonian fluids embracing a 40‐fold variation in liquid viscosity. The measurements have been carried out in fall tubes of four different diameters to elucidate the importance of wall effects. The experimental results encompass the following ranges of conditions: cylinder to fall tube diameter ratio: 0.08 to 0.4; length to diameter ratio: 0.05 to 2 and Reynolds number varied from 0.2 to 180.

The wall effects are discussed in a manner analogous to those for spherical particles. Terminal velocity data are analysed using two approaches, namely, drag coefficient‐Reynolds number relationship and a dimensionless velocity ratio denoting the departure from the behaviour of an equivalent sphere. Predictive equations have been developed using both schemes.