Showing papers in "Chemical Engineering Communications in 1982"
TL;DR: In this article, the authors discuss the role of statics in high-viscosity IMMISCIBLE FLUID systems and the application of mixers as disphers.
Abstract: (1982). DISPERSION PHENOMENA IN HIGH VISCOSITY IMMISCIBLE FLUID SYSTEMS AND APPLICATION OF STATIC MIXERS AS DISPERSION DEVICES IN SUCH SYSTEMS. Chemical Engineering Communications: Vol. 14, No. 3-6, pp. 225-277.
1,358 citations
196 citations
TL;DR: In this article, a 0.305 m diameter batch bubble column was used to study the fractional gas holdups in highly viscous glycerine and CMC solutions and showed that the gas holdup has a square root dependence on the diameter of the column.
Abstract: Gas holdup structures in highly viscous glycerine and CMC solutions are studied in a 0.305 m diameter batch bubble column. The fractional gas holdups are determined using the dynamic gas disengagement method. Empirical correlations for the gas holdup based on data covering wide ranges of viscosities in Newtonian and pseudoplastic non-Newtonian solutions are presented. For highly viscous pseudoplastic solutions in small diameter columns, the gas holdup has a square root dependence on the diameter of the column. The absence of small bubbles is suggested to be a reason for the very low volumetric mass transfer coefficients in highly viscous solutions, reported in the literature.
86 citations
TL;DR: In this paper, the effect of both molecular weight and chemical structure on the critical temperature was investigated using data from the comprehensive compilation of critical constants of Kudchadker et al. (1968).
Abstract: The present investigation is concerned with the effect of both molecular weight and chemical structure on the critical temperature. Using data from the comprehensive compilation of critical constants of Kudchadker et al. (1968), a simple relationship could be developed between the critical temperature and chemical structure. This relationship does not require experimental data such as the normal boiling point. It was found that the critical temperature (Tc) is given by an expression containing m and the sum of delta-i, where m is the total number of atoms in the molecule and delta-i is a number whose value is obtained from a table of additive atomic, group, and structural constants.
70 citations
TL;DR: In this article, the authors measured liquid-side mass transfer coefficients for absorption of CO2 and O2 into falling water films on the outside of a stainless steel pipe 2.72 cm OD and 183 cm absorption length.
Abstract: Experiments are conducted for gas absorption in a long wetted-wall column. Liquid-side mass transfer coefficients are measured for absorption of CO2 and O2 into falling water films on the outside of a stainless steel pipe 2.72 cm OD and 183 cm absorption length. The liquid film Reynolds number ranges from 129 to 10500 which encompasses the wavy-laminar, wavy-transition and turbulent flow regimes. The experimental data are correlated by a dimensionless equation of the form kt = (ktD) (v2/g) 1/3 = a-Rep-Sc1/2. The correlation is well supported by a viscosity-damped turbulence model at the gas-liquid interface which tends to confirm that viscosity is probably the major mechanism causing eddy damping and not surface tension as proposed by Levich and Davies. The form of the above correlation also represents previous experimental work at different temperatures and for different gases quite well.
70 citations
TL;DR: In this article, a systematic procedure for synthesizing chemical complexes in which toxicology aspects are incorporated in addition to the economic considerations based on previous, work by Grossmann et al.
Abstract: A systematic procedure is presented for synthesizing chemical complexes in which toxicology aspects are incorporated in addition to the economic considerations Based on previous, work by Grossmann ...
63 citations
TL;DR: In this article, the authors present a multiscale analysis of the effect of efficient transport in periODic HETEROGENEOUS MEDIA using a variety of tools.
Abstract: (1982). MULTI-SCALE ANALYSIS OF EFFECTIVE TRANSPORT IN PERIODIC HETEROGENEOUS MEDIA. Chemical Engineering Communications: Vol. 15, No. 1-4, pp. 83-91.
61 citations
TL;DR: The effect of reversible chemical reaction upon the diffusion of carbon dioxide in thin liquid film membranes is reviewed in this paper, with particular emphasis on the hydration reaction of CO2 and catalysis thereof.
Abstract: The effect of reversible chemical reaction upon the diffusion of carbon dioxide in thin liquid film membranes is reviewed. Particular emphasis is placed upon the hydration reaction of CO2 and catalysis thereof. Theoretical analysis is developed for equilibrium, near-equilibrium and near-diffusion regimes. The important effects of weak acid buffers, proteins and amines upon CO2 transport are also discussed, as well as the significance of diffusion potentials, particularly in the case of protein systems. Results of experimental investigations of facilitated CO2 transport are reviewed, as well as general aspects of CO2 transport in biological systems and absorbers.
59 citations
57 citations
TL;DR: In this article, an incident light interference microscopic technique has been employed to determine the drainage time, velocity of thinning and critical thickness of thin liquid films associated with foam systems using this technique.
Abstract: An incident light interference microscopic technique has been employed to determine the drainage time, velocity of thinning and critical thickness of thin liquid films associated with foam systems. Using this technique, we have investigated the drainage and stability behavior of aqueous foam films of various sizes containing both single component and mixed surfactant systems. The surface tension, surface viscosity and elasticity for the surfactant solutions were also measured. The experimental results for the drainage time are compared with the theoretical predictions.
55 citations
TL;DR: The present work proposes a simple method for exploiting features of maximally simple networks, those that have as well as the number of “matches” between streams.
Abstract: An important problem in the design of chemical processes is that of bringing process streams from their temperatures of availability to the temperatures at which they are needed without undue cost. An important strategy for reducing the cost of doing this is heat recovery: Using the heat available from streams to be cooled to service streams to be heated. In the absence of nonthermodynamic constraints, it is not difficult to assess the amount of heal recovery possible; and methods have been proposed (Linnhoff and Flower, 1978) that allow full heat recovery to be systematically obtained. The networks to which these methods lead are, however, more complex than necessary. Typically, therefore, those methods have been augmented with techniques for the evolutionary development of the initial network in order to simplify its structure, usually by minimizing the number of “matches” between streams. The present work proposes a simple method for exploiting features of maximally simple networks (those that have as ...
TL;DR: In this paper, the Fourier series can be used in order to obtain the inverse transform of the subsidiary equation of the given differential equation, and the analysis of transient heat transfer problem of two-dimensional and one-dimensional straight fins is considered to testify the merit of this method.
Abstract: For transient heat transfer problem with uniform initial temperature, the Laplace transformation method is considerably powerful. However, it is very difficult and complicated to solve the inverse transform of the subsidiary equation of the given differential equation. The technique of Fourier series can be used in order to obtain the inverse transform. The analysis of transient heat transfer problem of two-dimensional and one-dimensional straight fins is considered here to testify the merit of this method.
TL;DR: Bubble size distributions in a bubble column of 200 mm diameter were measured by means of a photoelectric probe in this paper, where the gas-liquid dispersion was generated by distributing air with a porous plate into aqueous solutions of electrolytes and of organic compounds.
Abstract: Bubble size distributions in a bubble column of 200 mm diameter were measured by means of a photoelectric probe. The gas-liquid dispersion was generated by distributing air with a porous plate into aqueous solutions of electrolytes and of organic compounds (alcohols, glycols, ketones, carboxylic acids, saccharose, carboxymethyl-cellulose, detergents). For all these solutes there exists a rather narrow concentration range in which the change from quick coalescence in pure water to coalescence suppression takes place. Though rough relationships between concentrations for coalescence suppression and molecular properties can be found (ionic strength for electrolytes, number of carbon atoms in a homologous series of organic compounds), exact equations based on a theory of coalescence cannot be given. The bubble size distributions obtained in the experiments have also been used to show the impact of coalescence phenomena on gas-liquid mass transfer. For this purpose, surface areas were calculated from measured ...
TL;DR: In this article, four models, two based on laminar shear and three based on turbulent flow, are proposed to describe drop dispersion in non-coalescing systems.
Abstract: Four models, two based on laminar shear and two based on turbulent flow, are proposed to describe drop dispersion in non-coalescing systems. The models predict the largest surviving drop size dmax as a function of geometry, speed and physical property variables. Laboratory data including suspension polymerization runs support the boundary layer laminar shear model for drops larger than approximately 200 microns. Smaller drops support a turbulence model. The boundary layer shear model was confirmed in scale-up suspension polymerization runs aimed at producing 1000 micron maximum bead sizes. Five approximately geometrically similar polymerizers were used, varying in size from 7.5 to 15000 liters.
TL;DR: In this article, the efficiency of a motionless mixer for mixing two Newtonian liquids has been investigated by using a decolourization method, and it appears that there is the worse performance of the mixer about the Reynolds number of 50.
Abstract: Pressure drop and homogenization efficiency of a motionless mixer of helical type have been studied experimentally. For evaluation of the drag coefficient the equation has been proposed which is valid within the range of Reynolds number from 10−2 to 104 The efficiency of the motionless mixer for mixing of two Newtonian liquids has been investigated by using a decolourization method. For the operating conditions studied in this work it appears that there is the worse performance of the mixer about the Reynolds number of 50. No influence of volume flow rate ratios (from 1 to 10) upon the performance of the mixer has been observed. A higher number of mixing elements must be applied for homogemzation of liquids with viscosity ratios above 100 as compared with that for viscosity ratio 1.
TL;DR: A new approach to the SYNTHESIS of MULTICOMPONENT SEPARATION SCHEMES is presented in this paper, where a new approach is taken to the problem of multiconnection separation.
Abstract: (1982). A NEW APPROACH TO THE SYNTHESIS OF MULTICOMPONENT SEPARATION SCHEMES. Chemical Engineering Communications: Vol. 17, No. 1-6, pp. 273-284.
TL;DR: In this article, the effect of dilute addition of polymer on the ribbing instability in coating flows was studied and a qualitative model which treated the growth of a disturbance as an extensional fl...
Abstract: Data are presented which show the effect of dilute addition of polymer on the ribbing instability in coating flows. A qualitative model which treats the growth of a disturbance as an extensional fl...
TL;DR: In this article, an explicit solution of the Maxwell-Stefan equations, which describe mass transfer in multi-componcnt gas mixtures, for a film model is developed as a generalisation of a method by Burghardt and Krupiczka for diffusion through a mixture of stagnant gases.
Abstract: An explicit approximate solution of the Maxwell-Stefan equations, which describe mass transfer in multi-componcnt gas mixtures, for a film model is developed as a generalisation of a method by Burghardt and Krupiczka for diffusion through a mixture of stagnant gases. The consistent approach to explicit approximations described here also leads to the earlier general method of Krishna. Numerical examples demonstrate the superiority of the new approximation in problems involving mass transfer at high rates.
TL;DR: In this paper, the effects of pyridine poisoning and coking on catalyst deactivation and kinetics were also determined, and the results were best correlated with a Langmuir-Hinshel-wood equation of the form where r is the rate, kT the rate constant, p are partial pressures, K's are adsorption constants, and subscripts T, H, S, respectively.
Abstract: The kinetics of benzothiophene hydrodesulphurizaiion (HDS) and hexene hydrogenation over a sulfided CoMo/Al2O3 catalyst were studied in a stirred flow microbalance reactor at atmospheric pressure. The effects of pyridine poisoning and coking on catalyst deactivation and kinetics were also determined. Benzothiophene HDS kinetics on the lined-out catalyst were best correlated with a Langmuir-Hinshel-wood equation of the form where r is the rate, kT the rate constant, p are partial pressures, K's are adsorption constants, and subscripts T, H and S stand for benzothiophene. H2 and H2S, respectively. This rate equation was the same for pyridine poisoned or coked catalyst, KT being lower, but KT and Ks being the same within experimental error. The rate of hexene hydrogenation was first order in hexene and hydrogen, and inhibited by hexene and hydrogen; but an explicit best equation could not be obtained. Pyridine deactivation of HDS was more selective than coke. At least two HDS sites exist, one being ...
TL;DR: In this paper, a numerical study of the turbulent two-dimensional air flow in a square enclosure where the vertical walls are held at different constant temperatures and horizontal walls have linear temperature distributions is performed.
Abstract: A numerical study is performed of the turbulent two-dimensional air flow in a square enclosure where the vertical walls are held at different constant temperatures and horizontal walls have linear temperature distributions. The equations solved are for continuity, mean momentum and mean thermal energy. The turbulent shear stresses and heat fluxes in these equations are prescribed using a three-dimensional turbulence model involving the solution of two extra differential equations for k, the turbulent kinetic energy, and ∊, its rate of dissipation. Buoyancy effects on the turbulence structure are also accounted for. Results have been obtained in the range of Grashof numbers of 107–108. Moreover, various model constants were tested and a sensitivity study was carried out in order to determine the effect of these constants on the results. A comparison with experimental data is given: the agreement is good.
TL;DR: In this article, the authors present diffusion-reaction equations for a sheared lamina within which the competitive reaction occurs and compare the results with measured product distributions with the results obtained within the last five years.
Abstract: Micromixing (mixing at the molecular scale) may be characterized by following fast, competitive, consecutive reactions having the following stoichiometry: A + B → R (1) R + B → S (2) provided that reaction mechanism and kinetics are known. This paper includes many results obtained within the last five years, in particular (a) diffusion-reaction equations for a sheared lamina within which (1) and (2) occur, and (b) comparisons of this and other diffusion-reaction models with measured product distributions.
TL;DR: In this paper, a study is made of this type of equipment with four turbines; either six or four flat-blade disc turbines were used, and experimental pulse-response curves were compared with the theoretical curves corresponding to two one-parameter models (i.e., a cascade of ideal stages with backmixing and one-dimensional diffusion model) and to perfect mixing.
Abstract: Little attention has so far been devoted to characterizing fluid-dynamic behaviour of multiple-impeller mixers which are often implicitly modelled as perfectly stirred tanks. In the present paper a study is made of this type of equipment—stirred with four turbines; either six- or four-flat-blade disc turbines were used. Mean local concentration inside the mixers was measured and experimental pulse-response curves were compared with the theoretical curves corresponding to two one-parameter models (i.e., a cascade of ideal stages with backmixing and one-dimensional diffusion model) and to perfect mixing. The results of both analyses show that both the one-parameter models considered represent the actual fluid-dynamic behaviour quite satisfactorily and the model of perfect mixing can be considered only as a first approach for macromixing modelling purposes. Extensive investigation was then carried out in order to determine the dependence of the characteristic parameter of the stagewise model on operating con...
TL;DR: In this article, the Second Law of Thermodynamics has a direct bearing on the aging process in biological systems and basic aging related phenomena are discussed from the point of view of an entropy rate balance, and known effects of body temperature, metabolic rate and food consumption rate on lifespan are considered.
Abstract: The Second Law of Thermodynamics (which is often referred to as “times arrow” because it dictates the direction of increasing chronological time), should have a direct bearing on the aging process in biological systems. Basic aging related phenomena are discussed from the point of view of an entropy rate balance, and the known effects of body temperature, metabolic rate and food consumption rate on lifespan are considered. The problems of quantifying the rate of internal entropy production of complex systems is investigated using the fundamentals of non-equilibrium thermodynamics. Entropy rate balance data over the lifespan of the annual fish Nothobranchius guentheri are used to illustrate basic aging phenomena.
TL;DR: In this article, an experimental technique is presented which will help resolve the nature of bulk motions occurring in turbulent flow, based upon photogrammetric analysis of stereoscopic motion pictures of the flow containing small neutrally buoyant tracer particles.
Abstract: An experimental technique is presented which will help resolve the nature of bulk motions occurring in turbulent flow. The technique is based upon photogrammetric analysis of stereoscopic motion pictures of the flow Held containing small neutrally buoyant tracer particles. The resulting data essentially consist of discrete sets of three-dimensional particle paths which characterize the bulk motions. The data obtained from the particle paths can also provide such information as point velocity measurements, velocity profiles and estimates of fluid accelerations. Furthermore the technique provides this information at a number of locations simultaneously and with time. In this work, the technique has been specifically applied to the study of flow phenomena occurring in an agitated tank.
TL;DR: In this paper, the dynamic effects of the motion of single bubbles entrained in a liquid are investigated in a vertical cylindrical pipe filled with quiescent water, and the pressure at the pipe wall was found to be as high as the dynamic bubble pressure for translational bubble motion, and an order of magnitude larger for oscillatory bubble motion following bubble formation.
Abstract: The dynamic effects of the motion of single bubbles entrained in a liquid are investigated. Extensive original experimental results are presented on the pressures associated with the motion of large, isolated spherical cap air bubbles rising both freely and through constricting orifices in a vertical cylindrical pipe filled with quiescent water. The pressures, measured at the pipe wall, were found to be as high as the dynamic bubble pressure for translational bubble motion, and an order of magnitude larger for oscillatory bubble motion following bubble formation.
TL;DR: In this paper, a generalized theory of Taylor dispersion is extended to include coupling effects, and an example of such direct coupling effects arises in problems pertaining to the gravitational settling and concomitant "sedimentation dispersion" of asymmetric Brownian particles.
Abstract: A previous generalized theory of Taylor dispersion phenomena is here extended so as to include “coupling” phenomena. Such direct coupling arises from the fact that—in certain circumstances—global transport processes may be driven by local gradients, and conversely. An obvious example of such direct coupling effects arises in problems pertaining to the gravitational settling and concomitant “sedimentation dispersion” of asymmetric Brownian particles lacking a center of symmetry. In the presence of such asymmetry the parlicle's translational and rotational motions are inseparably coupled to one another. This specific problem will be ueated in a companion paper as an example of the general coupling theory developed herein.
TL;DR: In this article, a mathematical model was developed for a counter-current reactor to investigate its performance in acid catalyzed cellulose hydrolysis, and the results indicated that use of this reactor would be advantageous particularly in obtaining high product yield.
Abstract: A mathematical model was developed for a counter-current reactor to investigate its performance in acid catalyzed cellulose hydrolysis. The results indicated that use of this reactor would be advantageous particularly in obtaining high product yield. The predicted yield of above 70% under normal reaction conditions was substantially higher than those achievable from plug flow (28%) or percolation reactor (54percnt;).
TL;DR: In this article, a mass transfer from FREELY-SUSPENDED PARTICLES in Stirred Tanks is described. But this is not the case in this paper.
Abstract: (1982). MASS TRANSFER FROM FREELY-SUSPENDED PARTICLES IN STIRRED TANKS† Chemical Engineering Communications: Vol. 14, No. 1-2, pp. 91-98.
TL;DR: In this article, a batch delignification of southern yellow pine using aqueous solutions of ethanol and 1-butanol has been studied at a temperature of 175°C. The extent of delignization, hemicellulose hydrolysis of the pulp, and monosaccharide appearance in solution are reported.
Abstract: Batch delignification of southern yellow pine using aqueous solutions of ethanol and 1-butanol have been studied at a temperature of 175°C. The extent of delignification, hemicellulose hydrolysis of the pulp, and monosaccharide appearance in solution are reported. From these data the relationship of bulk delignification, hemicellulose behavior and solvent selectivity can be used to better explain pulp yield from alcohol: water treatment processes,