bluuebunny/crossref_metadata_2025_split huggingface dataset:
Étude des isothermes d'Adsorption de surfactants ioniques et non ionique sur des fibres de laine carbonisée
Authors: Perineau Francis , Molinier Jacques , Gaset Antoine 
Published: March 2009

AbstractThe adsorption isotherms of the three main types of surfactant have been plotted against various pH's and temperatures. It has thus been possible to propose new ways of insuring adsorption and determining the importance of the ionic links and hydrophobic interactions involved in the various‐medium conditions considered. The presentations by Lauginuir and Freundlich have permitted to develop the adsorption equations corresponding to each case. Finally, the isotherm plotting in a series of low concentrations has permitted to predict the maximum volume of an effluent purified per kilogram of substrate, in the case of the concentrations frequently found in the waste waters.
A method for reducing the deposition of small particles from turbulent fluid by creating a thermal gradient at the surface
Authors: El‐Shobokshy M. S. 
Published: March 2009

AbstractThe present paper suggests the use of thermophoretic phenomena to decrease the rate of particle deposition onto pipe walls from a turbulent flow. When a tube is externally heated; the particles will be subjected to thermal force within the laminar sublayer in a direction away from the surface preventing or reducing their deposition. A theory proposed by EI‐Shobokshy and Ismail (1980) has been used for estimating the deposition velocity. The thermal velocity component was calculated and the effective velocity of particles approaching the wall surface computed. The results present the relationship between particle penetration and particle size at different values of pipe wall temperature and Re. The experimental results showed a good agreement with theoretical results for particle sizes 6 ‐10 μm diameter, Re = 6000 – 8000 and pipe wall temperatures 50 – 150°C.
Modelling radiation interception by strongly clumped vegetation — a combined monte‐carlo and analytical model
Authors: Whitfield D. W. A. 
Published: March 2009

AbstractThe study of solar radiation penetration into plant stands is important to studies of energy balance and photosynthesis. A large literature deals with horizontally uniform canopies of random leaf placement, in which a simple model based on Poisson statistics accounts for the probability, P(z), of ray penetration without interception to depth x: P(z) = exp [‐k(η)A(z)/cosη] where η is the ray origin zenith angle, k depends upon the distribution of leaf orientations and A(z) is leaf area per unit ground area to depth z. When leaf location is either clumped or regular other statistical models are applied. These, unlike the above model, require the empirical determination of parameters by fitting to interception data. More extreme clumping, into isolated plants or hedgerows, has been handled by calculating ray path lengths through the stand within an envelope defining the plant shape and applying the above model for uniform random leaf arrangement along these parts of the paths. For regular arrangements of uniform sized plants this is a matter of straightforward but lengthy calculation. The problem considered here, of randomly placed plants of non‐uniform size, cannot be treated by the same method. To determine within‐plant pathlengths, the intersection points of randomly chosen rays with the outlines of plants were first computed, then the above model was applied along each within‐plant path and the results of many rays from each direction were averaged. There are no parameters to be empirically fitted. Results are presented for cylindrical, conical and spherical plant outlines.
Laminar falling film flow and heat transfer characteristics on horizontal tubes
Authors: Rogers J. T. 
Published: March 2009

AbstractKnowledge of falling film flow and heat transfer characteristics on horizontal tubes is required in the assessment of certain CANDU reactor accident sequences for those CANDU reactors which use moderator dump as one of the shut‐down mechanisms. In these reactors, subsequent cooling of the calandria tubes is provided by falling films produced by sprays. This paper describes an analysis of falling film flow and heat transfer characteristics on horizontal tubes using integral methods. The application of the results to an assessment of the stability of the films on the calandria tubes following a loss‐of‐coolant accident with impaired emergency coolant injection flow is discussed.
Development of a monitoring system for Ash deposits on boiler tube surfaces
Authors: Chambers A. K. , Wynnyckyj J. R. , Rhodes E. 
Published: March 2009

AbstractThe etfect of ash deposits on the output of heat flux meters installed on the water wall tubes in pulverized coal fired utility boilers is studied. The objective is to use commercially available heat flux meters as the sensing devices for detecting and monitoring the growth of ash deposits. Reliable performance is shown and an attractive method is described for processing the heat flux meter output into a signal related to the ash deposit only and independent of variation of boiler load and firing conditions in the combustion chamber. Patents are pending for this Monitoring System.
Prediction of error estimates for thermocouple attached to a surface using differential inequalities
Authors: Martin W. W. , Lyn D. A. 
Published: March 2009

AbstractAn analysis is proposed to estimate the measurement error when determining the temperature of a surface with an attached thermocouple. The sensing element is assumed to be a point in a domain that is a circular segment of an infinitely long cylinder. The temperature distribution in the segment which models the medium used to attach the thermocouple is found approximately by using an embedding technique and the method of weighted residuals. The construction of bounds on the unknown exact solution is outlined and results are presented for Biot numbers up to 10.
Heat transfer to wires and cylinders in high‐temperature surroundings
Authors: Sayegh N. N. , Gauvin W. H. 
Published: March 2009

AbstractThis paper presents an extension to the case of wires and thin cylinders of a theoretical analysis previously reported by the authors to account for the effects of large temperature differences and large variations of the fluid property on the heat transfer process to a sphere exposed to a gas at very high temperatures.Two concepts were used in this theoretical derivation: (i) the use of a limiting Nusselt number at Re = 0, as derived from the energy equation, and (ii) the use of a reference film temperature for the evaluation of the Reynolds number different from that used for the Nusselt number. The predictions of this analysis are shown to be in excellent agreement with published experimental data in the Re range 0.01 to 40, when the ratio of the wire to the free stream temperature exceeds 0.4. This range of operating conditions is frequently encountered in industrial plasma processing and in certain high‐temperature chemical engineering operations.Measurements in argon and chlorine plasma tailflames with temperature differences exceeding 2000 K are described.
The effect of fin conductance on laminar heat transfer characteristics of internally finned tubes
Authors: Soliman H. M. 
Published: March 2009

AbstractAn analytical solution for the temperature distribution and Nusselt number during fully developed laminar flow in internally finned tubes is obtained taking into consideration the realistic situation of fins with finite thermal conductivities. Axially uniform heat flux and circumferentially uniform temperature are assumed at the outer surface of the tube. For any tube geometry, it was found that the heat transfer characteristics are influenced by a single parameter K, which is directly related to the angle subtended by the fin, and the thermal conductivities of the fluid and the fin material. Nusselt numbers corresponding to different values of K are presented for a range of tube geometries
Coherent particle oscillation in fluidized beds
Authors: Broadhurst T. E. , Becker H. A. 
Published: March 2009

AbstractVery shallow gas‐fluidized beds, typically under 0.1 column diameters in settled depth, exhibit coherent particle oscillations, also manifested by regular pulsations in bed height. This phenomenon has been studied experimentally and correlations have been developed for the oscillation frequency and the maximum bed height. The results give qualified support for the theories of Hiby and Verloop and Heertjes, but needs for improvement in the theoretical approaches and for more experiments are also evident. In particular the effects of column diameter, distributor resistance, and plenum volume need systematic study in order to answer questions raised by our work, a theoretical suggestion by Davidson, and results of Baird and Klein for an adjacent operating regime.
Production of anhydrous 1,4‐dioxane from ethylene oxide in the presence of amberlyst 15
Authors: Yamanis John , Garland Ronald W. 
Published: March 2009

AbstractThe fast and exothermic reaction of ethylene oxide with the sulfonic acid groups of Amberlyst 15 (H+), suspended in an inert solvent, leads to the formation of polymeric ester species whose length aproaches a limiting value.The ester chains decompose to form cyclic ethers and this decomposition can be made selective for 1,4‐dioxane in a two‐step process by first esterifying the resin and then depolymerizing the esters. The resin can be used repeatedly with substantial capacity loss, but this loss can be removed by regeneration.1,4‐Dioxnne formatios from the esters was fousd to be described by the phenomenological model.

with an apparent activation energy of 25.8 kcal/mol.
Surface and interfacial tension measurement by drainage methods
Authors: Baird M. H. I. , Nirdosh I. 
Published: March 2009

AbstractThe drainage of a liquid from a narrow vertical tube which is open at the bottom but closed at the top is prevented when the capillary forces exceed the gravitational forces acting on the liquid meniscus. The critical tube diameter for prevention of drainage is a function of surface or interfacial tension, and this effect forms the basis of three techniques for measuring surface or interfacial tension. Results are given for various liquid/air and liquid/liquid systems in (a) a tapered tube, (b) a rotating uniform tube and (c) a tilted uniform tube. Methods (a) and (b) appear capable of measuring surface or interfacial tension within about ± 1%.
A modified general dominant eigenvalue method for convergence acceleration of cyclic systems
Authors: Soliman M. A. 
Published: March 2009

AbstractIn this paper, a new derivation is presented for the General Dominant Eigenvalue Method (GDEM) for Convergence Acceleration of cyclic systems described by a set of non‐linear algebraic equations. Through the derivation a modification which improves the convergence of the GDEM is suggested. Two examples are used to show the kind of improvement, one might expect using the modified version.
Mechanical degradation of semi‐dilute polymer solutions in laminar flows
Authors: Ghoniem S. , Chauveteau G. , Moan M. , Wolff C. 
Published: March 2009

AbstractMechanical degradation of a semi‐dilute solution of non‐hydrolyzed polyacrylamide was studied under laminar flow conditions through fine capillary systems. Using a multi‐pass device and capillary tubes of the same diameter and of various lengths we have shown that mechanical degradation (i) occurs at a critical value of the wall shear rate, chosen as a reference deformation rate, which is slightly higher than that of the appearance of high pressure losses in the entrance region of the capillary tube; (ii) is independent of the capillary tube length; (iii) increases with the number of passes N up to a maximum value for a limiting number of passes Nlim which is a decreasing function of deformation rates but does not depend on capillary length.The amount of degradation is expressed in terms of loss of viscous dissipation in shear and transient elongational flow. This last point is determined by studying the total end pressure loss through the capillary tube as a function of the pass number. The high pressure loss is related to viscous dissipation on macromolecules stretched by rapid converging flow. A comparison between a fresh and a fully degraded solution indicates that the degradation affects shear viscosity much less than viscous dissipation in rapid converging flow which is related to the properties of extended macromolecules. Both experimental results and theoretical interpretation suggest that, in our capillary system, the mechanical degradation occurs in the entrance region of the capillary where macromolecules are stretched and consequently submitted to extensional forces which can overcome the C–C bonds strength.
Theoretical studies on the gravity drainage of heavy oil during in‐situ steam heating
Authors: Butler R. M. , Mcnab G. S. , Lo H. Y. 
Published: March 2009

AbstractOne concept for the in‐situ production of oil from the tar sands involves the continuous injection of steam into a growing steam‐saturated volume or steam chamber. Steam flow to the boundary of the chamber, condenses and gives up its heat to the surrounding oil sands. The condensate and heated oil flow by gravity to a production well located at the bottom of a chamber and are removed continuously. The well may consist of a horizontal slotted pipe. This paper describes the theory of operation of such a process and an equation is derived which predicts the rate of drainage.
Local compositions and local surface area fractions: A theoretical discussion
Authors: Panayiotou C. , Vera J. H. 
Published: March 2009

AbstractThe basic constraint for any valid expression for local composition, derived by McDermott and Ashton, is shown to be equivalent to the conservation equation used in Flemr's analysis. A similar constraint for local surface fractions is derived. The applicability of quasi‐chemical expressions for local composition or local surface area fractions is extended to different existing (random) models of solutions. Chao's and Kehiaian's treatments appear as special cases. The statistical thermodynamic derivation of UNIQUAC is discussed in the framework of the generalized treatment. A method for solving the quasi‐chemical equations for quaternary systems is described.
Batch cultivation of kluyveromyces fragilis in cheese whey
Authors: Beausejour Denis , Leduy Anh , Ramalho Rubens S. 
Published: March 2009

AbstractKluyveromyces fragilis was cultivated batchwise in an open pond rectangular bioreactor at 30°C, 2vvm of aeration, under non‐sterile conditions and uncontrolled pH. The culture medium contained 7% cheese whey powder, 0.25% KH2PO4, 0.5% (NH4)2SO4 and was adjusted to an initial pH of 4.0 with phosphoric acid. The lactose was almost completely consumed after 16 h and COD reduction attained 80% after 64 h. The maximum suspended solids concentration obtained was 11.7 g/L. The cheese whey which had initially low protein and high lactose contents was converted by this system into a high protein and low lactose carbohydrate product.
Mathematical modelling of rotary cement kilns by the zone method
Authors: Guruz H. K. , Bac N. 
Published: March 2009

AbstractA steady state mathematical model of rotary cement kilns based on the fundamental principles of the physical and chemical processes within the kiln was developed. The zone method of analysis was utilized together with the Monte Carlo method to simulate the radiative interchange within the kiln. Steady state energy balances including the chemical reaction terms for each zone were solved simultaneously to give temperature distributions in gas and solid charge, and composition distribution in solid charge. Predictions of the mathematical model were compared with dry process and wet process rotary cement kiln data.
Penetration model of gas absorption into slurry accompanied by an instantaneous irreversible chemical reaction
Authors: Uchida S. , Miyachi M. , Ariga O. 
Published: March 2009

AbstractRecently, the problem of absorption of gases into nonhomogeneous solvents has drawn more attention than ever as it found in various fields such as flue gas scrubbing, hydroprocessing, coal conversion and medicine. Since the first treatment of this problem by Ramachandran and Sharma(1), several models based on the film concept have been proposed(2‐7). There is, however, no penetration theory for the evaluation of the rate of the absorption of a gas into a slurry containing suspended solid particles. In this paper, a penetration model is presented for the absorption of gas A into a slurry containing solid B with an instantaneous irreversible chemical reaction.
Void fraction and pressure drop in two phase stratified flow
Authors: Kadambi V. 
Published: March 2009

AbstractA procedure for computing the void‐fraction and pressure drop in two‐phase stratified flow over the whole range of flows from turbulent‐turbulent to laminar‐laminar, has been put forth. The results are in excellent agreement with those of previous investigators in flow situations where data are available. Simple curve fits of the theoretical results have been developed to compute the required quantities, as functions of the Lockhart ‐ Martinelli parameters.
Intraparticle effects in char combustion. III transient studies
Authors: Srinivas B. , Amundson Neal R. 
Published: March 2009

AbstractUnsteady state mass and energy balance equations along with a probabilistic model to predict the surface area evolution, constitute the model developed to study the dynamics of single particle char combustion. The transients and the ignition‐extinction phenomenon are analyzed with the aid of the pseudo‐steady state structure of the problem. There exists a critical particle size, ambient temperature, ambient oxygen concentration and boundary layer thickness above which the particle ignites. There is an optimum particle size for which the burning time is a minimum. Experimentally observed extinction phenomenon of artificially ignited particles is predicted by the model. Also, it is found that the extinction radius decreases with increase in ambient O2 concentration, which is in qualitative agreement with the experimental results. The model is compared with the simple shrinking core model.
Finite element solution of low peclet number fluid flow in a round pipe with the cauchy boundary condition
Authors: Lee S. L. , Hwang G. J. 
Published: March 2009

AbstractThis paper presents a finite element solution to the problem of low Peclet number fluid flow in the thermal entrance region of a round pipe. The velocity is assumed to be laminar and fully developed throughout the pipe and the fluid temperature is kept uniform atX = —∞. The pipe wall is adiabatic at X ≤ 0 and cooled convectively at X ≥ 0.The solutions include temperature distributions and Nusselt numbers for the parameters, Bi = 0.04, 0.4, 4, 20 and Pe = 1, 3, 5, 10, 20, 30, which are in excellent agreement with the existing analytic solution except in the region near the singular point Δ A temperature discrepancy in the analytic solution at this point is physically impossible. The finite element method overcomes this mathematical difficulty and shows a greater value in the Nusselt number due to a higher wall temperature at X ≥ 0.
Preparation of high porosity catalysts
Authors: Ternan M. , Packwood R. H. , Buchanan R. M. , Parsons B. I. 
Published: March 2009

AbstractPorous alumina catalyst supports have been prepared with pore volumes exceeding 1.0 mL/g, with most pores having diameters of the order of 3 μm and with surface areas exceeding 150 m2/g. They were obtained from dilute alumina gels having large concentrations of acid and very large concentrations of fluid. Attempts were made to dry the gel without collapsing the pore structure between the alumina particles. The catalysts were characterized by gravimetrical BET surface area, mercury porosimetry, X‐ray diffraction and scanning electron microscopy. Catalyst supports having these geometric properties should eliminate mass transfer restrictions during hydrocracking of petroleum residua, heavy oils and bitumen derived from oil sand deposits.
The effect of chromium exchange level on the cracking and dehydrocyclization of n‐Heptane on CrHNaY zeolite catalysts. Kinetic and spectroscopic study
Authors: Agudo A.L. , Asensio A. , Corma A. 
Published: March 2009

AbstractThe influence of the degree of chromium ion exchange on Y zeolites on the catalytic activity for cracking and dehydrocyclization of n‐heptane has been studied at 673, 723 and 748 K and atmospheric pressure in a continuous flow system. The kinetic rate constants and activation energy in absence of decay for the cracking of n‐heptane on the catalysts have been obtained. Measurements of the surface acidity of these catalysts by I.R. spectroscopy of adsorbed pyridine and by titration with n‐butylamine has been carried out. A good correlation between the activity cracking of n‐heptane and the concentration of stronger acid sites (pKa ≤ + 1.5) on the chromium‐exchanged Y zeolites has been found.
Modeling of flow nonuniformities in fissured porous media
Authors: Lyczkowski Robert W. 
Published: March 2009

AbstractA review is performed to trace how fissured porous media arise in nature. It is found that packed beds resemble fissured porous media. The range of multiple flow time‐scales inherent in such media becomes larger as the particle size range becomes broader, resulting in flow nonuniformities. The status of experimental measurements of voidage and flow nonuniformities is assessed. Some of the difficulties associated with modeling of the multiple flow time‐scales are discussed, and a tentative model is proposed.
Use of gold tracer in the study of atmospheric oxidation of sulfur dioxide
Authors: Rowe Richard D. , Mohtadi Matt F. , Havlena Jan J. , Exall Douglas I. , Benjamin Stephen F. 
Published: March 2009

AbstractA technique using gold particles as a conserved tracer has been developed in an effort to determine experimentally the oxidation of sulfur dioxide in sour gas plant plumes. A helicopter was used for plume sampling at distances up to 4 km downwind of the stack. The concentration of sulfur dioxide gas in the plume sample was determined by the West‐Gaeke method. Neutron activation analysis was used to determine the concentration of gold particles in the plume sample. Since gold particles do not react chemically with plume gases, any decrease in their concentration along the plume path was due to turbulent dispersion. This parameter allowed an accurate estimation to be made of the decrease in the sulfur dioxide concentration within the plume sample that had occured due to physical dilution alone. Any further decrease in concentration could therefore be attributed to loss by chemical reaction. The experimental results indicated that, within the range studied, there is no measurable oxidation of sulfur dioxide in sour gas plant plumes.