bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intraparticle effects in char combustion II. Steady state analysis
Authors: Srinivas B. , Amundson Neal R. 
Published: March 2009

AbstractBased on the results of an earlier paper, a model is developed to include the homogeneous reaction in the external boundary layer. It is assumed, consistent with those results, that there is no homogeneous reaction within the particle. A feasibility region is constructed using limiting cases along the lines described there. Under some conditions, the model predicted up to five steady states for a given set of ambient conditions. For large particles, a flame develops in the boundary layer and the main product is CO2. Under such conditions, the reaction locus coincides with the double film model. While for small particles, no flame develops and the major product is CO. The solution is sensitive to the type of radiative interaction which obtains. The combustion rate increases with increase in particle temperature until a certain point, then decreases with further increase in temperature, and eventually turns back and increases again. Such behavior has been observed in some rate measurement experiments.
Vapor‐liquid equilibrium data for the methanol‐water‐sulphuric acid system at 101.3 kPa
Authors: Pinder K. L. 
Published: March 2009

AbstractAtmospheric pressure vapor‐liquid equilibrium measurements were made on water‐methanol solutions with varying concentrations of sulfuric acid. Because of the reaction between methanol and sulfuric acid during the measurements, the maximum acid concentration useable was 20 weight percent. The mole fraction of methanol in the water‐methanol mixture was varied from 0.1 to 0.9.The data were analysed as a “special binary” with the sulfuric acid as a non‐volatile component. An excellent fit to the data was given by the full equation by Jacques for binaries with a non‐volatile salt added.
Control of a distillation column using self‐tuning regulators
Authors: Dahlqvist S. A. 
Published: March 2009

AbstractSelf‐tuning regulators were applied to the multivariable control of a pilot distillation unit. Both the top and the bottom product compositions were simultaneously controlled. The multivariable interactions were compensated for by different strategies. It was shown that a proper choice of the control variables made it possible to use a regulator with a smaller number of parameters. The evaluation of the results shows that the self‐tuning regulator is a valuable tool in multivariable control of distillation columns.
An experimental study of the effects of surface characteristics and material thermal properties on dropwise condensation
Authors: Abdelmessih A. H. , Rotenberg Y. , Neumann A. W. 
Published: March 2009

AbstractIn this investigation, a study of the dropwise mode of condensation of water vapour at near atmospheric pressure was undertaken. Three vertically oriented condenser surfaces of different materials, copper, brass and stainless steel, were carefully prepared and heat transfer data were obtained over a long period of time as the surfaces continued to deteriorate.The condensation heat transfer coefficient was found to decrease with increasing surface deterioration. It is also evident that further work is needed before a general model can be developed to predict heat transfer in dropwise condensation. However the effect of surface characteristics and material thermal properties on strong dropwise condensation at small vapour to surface temperature differences is evident from the present results.
Measuring and modelling forest evapotranspiration
Authors: Spittlehouse D. L. , Black T. A. 
Published: March 2009

AbstractMicrometeorological methods of measuring and modelling forest evapotranspiration are reviewed and evaluated. Measurement methods include eddy correlation, aerodynamic, Bowen ratio/energy balance and stomatal diffusion resistance techniques. Modelling approaches discussed include a model relating evapotranspiration rate to the root zone water content and the net radiation flux, the Penman equation, and vapour diffusion models requiring stomatal resistance characteristics of the stand. Measured and modelled estimates of evapotranspiration from a Douglas‐fir stand are compared.
Heat flow between large terrestrial animals and the cold environment
Authors: Christopherson R. J. , Young B. A. 
Published: March 2009

AbstractEstimates of the rates of heat loss and resistances to heat loss from large animals in cold environments have been made from steady state measurements of metabolic rate using indirect respiration calorimetry and measurements of deep body and surface and air temperatures. These estimates can be used to predict an animal's lower critical temperature (ambient temperature below which an animal has to increase its rate of heat production to prevent hypothermia) and the increased heat flow during cold stress. Data from experiments at the University of Alberta have been summarized together with data from the research literature. Resistances to body heat loss expressed as insulation values are influenced by animal size, amount of subcutaneous fat, hair coat thickness, air movement and moisture conditions. Increasing the level of food intake and cold acclimation increase the resting metabolic rate and lower the lower critical temperature of animals.
Development and testing of a method of estimating sensible heat flux from natural surfaces using remotely sensed surface temperatures
Authors: Leckie D. G. , Black T. A. , Murtha P. A. 
Published: March 2009

AbstractRemote sensing techniques for the determination of the sensible heat flux component of the energy balance of natural surfaces have applications to several fields of study. Research into the use of a night‐time cooling model for remote sensing thermal inertia mapping which has applications to soil moisture measurement and geologic interpretation prompted the following study. The theoretical framework is presented for a method of determining sensible heat flux in a stable boundary layer from input parameters of radiometrically determined surface temperature, surface roughness, and the air temperature and wind speed at one height above the surface. Corrections for stability and the surface sublayer are included. The method is tested over a vegetated and a non‐vegetated surface using ground based data. Given accurate input parameters, the method gives excellent results for the non‐vegetated surface, but unreliable results for the vegetated surface.
Transient heat transfer and fluid mechanics of a recirculating pressurized water loop during blowdown and cold water injection
Authors: Barclay F. W. , Nieman R. E. , Hasinoff M. P. 
Published: March 2009

AbstractMathematical models, in the form of computer codes, are used to evaluate the performance of process and safety systems of CANDU nuclear reactors during normal operation and postulated accident conditions. To validate the models, predictions are made of the transient heat transfer and fluid mechanics processes in pressurized water loops following simulated pipe ruptures. These loops have the essential geometric and physical characteristics of a CANDU reactor primary heat transport system. Comparisons with data from loops of different scales over the conditions of interest (blowdown and cold water injection) are used to illustrate that the models predict the trends in the experiments adequately when the assumptions inherent in the model (e. g. equal steam and water velocities) are valid. To improve accuracy in cases where these assumptions do not apply, a more sophisticated representation of two‐phase flow is required.
Wall shear stress and mass transfer in vertical two‐component flow
Authors: Surgenor B. , Banerjee S. 
Published: March 2009

AbstractMass transfer rates in vertical gas‐liquid flow were measured by an electrochemical technique. The flow regimes studied were slug, churn and annular. Average mass transfer coefficients in gas‐liquid flow could be correlated by expressions similar to those for single phase flow. Fluctuations in local mass transfer coefficient could be used to indicate flow regimes. Average wall shear stress determined from the average mass transfer coefficients agreed with values calculated from measurements of pressure drop, void fraction and flow rate, provided flow reversals did not occur. The results indicate that the electrochemical technique could be used to measure wall shear stress in accelerating gas‐liquid flows, such as critical flow.
Heat transfer from cylinders in unsteady flow
Authors: Base T. E. , Patel J. M. , Valaitis G. C. 
Published: March 2009

AbstractThe paper is concerned with the experimental determination of the forced convective heat transfer from heated cylinders when the approaching flow has low frequency oscillations in the magnitude of the free stream velocity. Initial tests showed that at very low reduced frequency values, based on the cylinder diameter and the mean flow speed, up to values of .01, a reduction in the Nusselt Number value of up to 12% below the Nusselt Number for uniform approaching turbulent flow was recorded. For reduced frequency values above .03, an increase in the Nusselt Number to the original value when the flow was steady was measured.
Hydrotransport of solids in horizontal pipes: Effects of solids concentration and particle size on the deposit velocity
Authors: Parzonka W. , Kenchington J. M. , Charles M. E. 
Published: March 2009

AbstractCorrelations previously proposed in the literature for the deposit velocity in the flow of settling slurries in horizontal tubes generally predict increasing values with increasing solids concentration. However, the present comprehensive investigation which has drawn on data from a broad geographical base, confirms that the deposit velocity shows a maximum with respect to concentration and decreases above about 15% by volume solids. It is also shown that the presence of fine particles (<75 μm) is particularly significant in determining the degree of the reduction in the deposit velocity for the higher concentrations. This reduction would appear to be due primarily to a significant increase in the drag coefficient for particles settling in a fine particle suspension, i.e. heavy medium. The data are summarized in graphs for a variety of materials including sand, gravel, iron ore and coal.
Bubble pumping in cocurrent gas‐liquid flow and its effect upon conversion in continuous fermentation
Authors: Wick Emil 
Published: March 2009

AbstractBubble pumping was demonstrated in cocurrent, gas‐liquid flow through experimental vessels which had been used to carry out continuous alcohol fermentation. The pumping rates, measured with a video‐tape technique during cocurrent upward flow, were used to compare these vessels as gas‐lift pumps to some actual air lift pumps. The effect of bubble pumping upon the conversion achieved in these vessels is shown and the significance of this for vessel design is discussed.
Capsule hoist system for vertical transport of coal and other mineral solids
Authors: Hwang L. Y. , Wood D. J. , Kao D. T. 
Published: March 2009

AbstractA capsule hoist system for the vertical transport of solids in pipelines is studied. For this system a cylindrical capsule loaded with cargo is inserted into the lower end of a vertical liquid filled tube. The capsule which is of lower average density than the liquid is lifted due to natural buoyant forces. A theoretical analysis of capsule speed and system transport efficiency is carried out.The predicted results are in good agreement with a substantial number of experimental results. Of particular interest was the effect of the ratios of capsule diameter to tube diameter, capsule diameter to capsule length and average capsule density to liquid density.The principal goal of the study is to determine design factors which will maximize the rate of hoisting cargo for a particular system. It was concluded that the best ratios for capsule diameter to tube diameter and capsule density to liquid density are both approximately 2/3. It was further concluded that capsule length and the shape of the capsule nose has little influence on the efficiency of this transport system.
Treatment of complex silver arsenide concentrate in nitric acid system
Authors: Kunda Wasyl 
Published: March 2009

AbstractA complex silver arsenide‐sulphide concentrate containing bismuth, cobalt, nickel, copper, zinc, lead and iron as major constituents, was leached in nitric acid. The leach solution, which contained 95% to 99% of the Ag, Bi, Co, Ni, Cu, As and Fe present in the ore, was further processed to separate the metals into the following fractions: (1) silver chloride, (2) bismuth oxychloride and/or hydroxide, (3) arsenic‐iron precipitate and (4) Ni‐Co‐Cu‐Zn sulphide.Silver was precipitated from solution with sodium chloride. Bismuth oxychloride‐hydroxide and arsenic‐iron were precipitated by controlled ammonia addition and cobalt‐nickel‐copper‐zinc sulphides were precipitated with ammonium sulphide.Silver chloride was further processed to a high purity silver powder by heat treatment with sodium carbonate.The parameters controlling each processing step are discussed.
Measurement of binary diffusion coefficient of gases and organic vapours by chromatography
Authors: Pathak B. K. , Singh V. N. , Singh P. C. 
Published: March 2009

AbstractThe binary diffusion of organic vapours such as benzene, nitrobenzene, aniline, n‐hexane, acetone, ethyl alcohol and toluene in H2, Ar and N2 at different temperatures and the diffusion coefficients of the gas pairs; Ar‐O2, Ar‐N2, Ar‐SO2, N2‐NH3, N2‐O2, N2‐CO2 & N2‐SO2 at 25°C have been studied using a gas chromatograph (GCHF‐18). Good agreement was found between observed and theoretically calculated values of diffusion coefficients.
Surface shear viscosity of straight chain (c15 to c20) fatty acids
Authors: Moo‐Young M. , Fulford G. D. , Deysarkar Asoke K. 
Published: March 2009

AbstractExperiments were carried out to measure surface shear viscosities of a series of straight chain fatty acids from C15 to C20. The experimental results indicated that members of the series with even‐numbered C‐atoms were essentially surface‐Newtonian in behaviour with viscosity increasing with increasing chain length. However, members of the series with odd‐numbered C‐atoms were surface pseudoplastic and the degree of pseudo‐plasticity decreased with increase in chain length. The experimental results also indicated that aging of surface‐active solutions increases their surface shear viscosities.
Implementation and demonstration of a quasi‐steady‐state controller for yeast fermentation
Authors: Kalogerakis N. , Boyle T. J. 
Published: March 2009

AbstractEarlier work has presented the need for, and the structure of, a control system to force fed batch fermentations to a quasi‐steady‐state (QSS) rapidly. Necessary modifications to this controller to permit it to be implemented on a computer‐coupled laboratory fermentor are presented. These include use of manual sampling to obtain reliable cell concentration data and the use of stream blending to achieve the desired control actions. The implementation is via a DDC loop structure which achieves proportional feedback control, calibrated decoupling of response models, and non‐linear time‐varying actuator constraints. The experimental run presented shows the desired rapid response of cell concentration with evidence of no interaction between cell and substrate, even though the manipulated variables are saturated throughout much of the transient.
A flexible solution method for generalized equilibrium stage columns
Authors: Li M. C. , Frost R. J. 
Published: March 2009

AbstractThis paper presents a flexible solution method for the process design and simulation of generalized equilibrium stage absorption or distillation columns for solving a wide range of multistage, multicomponent separation problems in the petroleum or petrochemical industries. Although the model was developed to increase the control flexibility of product components in a solution, it was found that it also increases the efficiency of convergence at the expense of greater core usage. The mathematical model includes overall material balances, component material balances, energy balances, summation equations and specification equations. These nonlinear equations are solved simultaneously via the matrix partitioning technique together with the popular Newton‐Raphson iterative algorithm. The method is applicable for both absorption and distillation columns with multiple feeds and sidedraws. This model will offer more flexible choices of the column specifications such as tray temperature, overhead product rate, reflux ratio, boilup ratio, tray vapor/liquid flow and product purity/recovery. The composition dependent equilibrium and enthalpy correlations such as Chao‐Seader, Grayson‐Streed, and Soave‐Redlich‐Kwong are incorporated into the mathematical model. Most problems can be easily converged with less than ten iterations.
Electromagnetic sensing of slurry concentration
Authors: Peters J. , Shook C. A. 
Published: March 2009

AbstractFluctuations in the output voltage from a conventional magnetic flux flowmeter have been shown to depend upon mean velocity and slurry concentration. Since reliable values of mean velocity can be obtained from time‐average voltages, the fluctuations could be used to sense slurry concentrationThe relationship between the fluctuations and slurry concentration depends on particle and fluid properties so that calibration would be required. However with further progress in understanding of vertical slurry flows, the relationship may be predictable.
Effect of geometrical arrangement and interdrop forces on coalescence time
Authors: Vohra D. K. , Hartland S. 
Published: March 2009

AbstractAccording to the Reynolds' equation the time taken for a thin film to reach a critical thickness at which rupture occurs is a function of the film area and applied force. It follows that the coalescence time of a liquid drop is greatly affected by its geometrical configuration. If the drop is unconstrained the coalescence time increases when a vertical force is applied to the drop, but if the drop is constrained by the presence of surrounding drops its coalescence time decreases as the applied force increases. This explains why the rate of coalescence at the disengaging interface of a close‐packed dispersion increases with the dispersion height. The coalescence time for a planar film is usually less than for the spherical film formed between a drop and its homophase which explains why near‐horizontal surfaces inserted into close‐packed dispersion increase the rate of coalescence. The coalescence time of a drop in a close‐packed dispersion decreases as it approaches the disengaging interface. This means that the volume rate of coalescence at the interface may equal the disperse phase throughout without the necessity for interdrop coalescence. When the applied pressure is much greater than the van der Waals pressure, as in a close‐packed dispersion, the critical film thickness is itself a function of the film area and applied force, but this has little effect on the above conclusions. When the applied pressure is much less than the van der Waals pressure, as in a loose‐packed dispersion, the critical film thickness is only a function of the film area and the affect of the applied force on the coalescence time is then increased.
Computer generated time & distance values of nutrient constituents with applications to timed‐release capsules
Authors: Forgacs C. , O'Brien R. N. 
Published: March 2009

AbstractThe diffusion equation for infinite cylindrical sources has been solved for the boundary conditions appropriate to timed‐release fertilizer pellets. The solution was tested against experimental results of the distortion of the image of a grind illuminated by laser light and recorded on video tape. The optical theory was examined for validity using Fermat's Principle. A computer program was developed to predict concentration as a function of time and distance with sufficient flexibility to allow for multiple sources and any other variation which can be accounted for by change of diffusion coefficient.
The kinetics of dissolved oxygen reaction in aqueous sodium dithionite solutions
Authors: Kawagoe Mikio , Robinson Campbell W. 
Published: March 2009

AbstractThe kinetics of the reaction between dissolved oxygen and sodium dithionite in alkaline aqueous solution was investigated in a stirred cell. For dithionite concentrations below 0.08 kmol/m3 and sodium hydroxide concentrations from 0.044 to 0.27 kmol/m3, the results show the reaction to be first order in dithionite and zero order in oxygen. The Arrhenius activation energy was determined to be 76.2 MJ/kmol in the temperature range 15 to 34°C. Addition of other electrolytes (sodium sulphate or potassium chloride) had no effect on the kinetics.
Thermodynamic availability analysis of fractional distillation with vapour compression
Authors: Mostafa Hamdi A. 
Published: March 2009

AbstractThermodynamic analysis based on the concept of availability or energy arising from the second law of thermodynamics is a useful tool for process development and design. The exergy is especially useful for analysing processes containing different forms and qualities of energy. In these cases the analysis based on the first law could not give meaningful results.The work attempts to show in what circumstances the compression of the overhead vapour from a distillation column and the use of condensing vapours to reboil the bottoms is preferred to the conventional scheme. To achieve this goal, the thermodynamic energy coefficient of performance of the system is calculated as a function of system properties, column pressure, degree of separation, compression ratio and number of plates. The results of calculations indicate the effect of each variable on the thermodynamic performance of distillation with vapour compression and point out directions for process improvement.
Methanation of carbon monoxide catalyzed by nickel/zeolite y and nickel/ η‐alumina; effect of reduction time
Authors: Bhatia S. , Bakhshi N. N. , Mathews J. F. 
Published: March 2009

AbstractThe catalytic behavior of three nickel catalysts, viz. nickel supported on η‐alumina and nickel supported on zeolite Y (prepared by impregnation and ion exchange methods) were investigated for the methanation reaction. All the catalysts were reduced in flowing hydrogen at 723 K for times varying from 6 h to 24 h. The catalytic activities of these catalysts were determined using a differential flow reactor. The catalysts were characterized using the techniques of hydrogen chemisorption and x‐ray diffraction.Nickel metal areas were found to increase with reduction time for all catalysts. X‐ray diffraction studies showed that crystallite size varied with reduction time in the case of Ni/zeolite Y catalyst (both impregnated and ion exchanged). Turnover numbers were found to vary with crystallite size and the maximum values of the turnover number were obtained for the catalysts having crystallite sizes of 14‐16 nm. There appears to be strong evidence that reduction time can have an effect on catalytic activity; possibly by its effect on crystallite size.The effect of support on catalytic activity was more complicated as there appeared to be an interaction with reduction time. However, nickel/η‐alumina appeared to be a more active catalyst than nickel/zeolite Y.
Annular bed reactor‐methanation of carbon dioxide
Authors: Davis Mark , Fairweather Graeme , Yamanis John 
Published: March 2009

AbstractCatalytic methanation of carbon dioxide has been studied in a new type of annular bed reactor. In this new design, the central core is packed with large inert spheres; the catalyst occupies the annular space between the inert spheres and the wall. A first‐generation model, representing insothermal operation of the annular bed, prepicts improved conversion for the packed compared to the unpacked‐core reactor.