Showing papers in "Canadian Journal of Chemical Engineering in 1968"

The effect of particle size distribution on packing density

Abstract: The packing density of a multi-particle system is found to increase if the particle size distribution is extended. Results are reported for Gaussian and log-normal size distributions using dense random packing of two sands with particle sizes of front <0.07 to 8.0 mm. Packing density is shown to be a function only of size distribution represented by a dimensionless standard deviation, and of particle shape. It is independent of particle size. Packing densities of binary mixtures of continuously distributed systems are found to depend upon the composition of the mixture, the mean-size ratio of the components of the binary, and upon the packing density of the individual components. Maxima occur at compositions of 55 to 75% larger component, and increasing mean-size ratios result in greater packing densities. The “increase in packing density” factor is a useful function for comparing, and setting limits to, packing densities of binary mixtures. The results should allow improved prediction and control of packing densities of many commonly encountered particle systems.

Diffusion in binary liquid mixtures at infinite dilution

Abstract: A correlation is presented for the mutual diffusion coefficient in a binary liquid system at infinite dilution. It has several advantages over previous correlations, and is recommended for diffusion in organic solvents. Some special cases where empirical correlations should be used with caution are discussed briefly. On presente une correlation relative au coefficient de diffusion mutuelle dans le cas d'un systeme binaire liquide a dilution infinie; elle a plusieurs avantages sur les precedentes et on la recommande lorsqu'il s'agit de la diffusion dans des solvants organiques. On discute brievement certains cas speciaux ou il faut utiliser avec precaution des correlations empiriques.

A theoretical treatment of catalyst decay

Abstract: A theoretical treatment of the decay of activity in aging catalysts is presented. In this treatment it is assumed that catalyst activity is a function of time-on-stream only and on the basis of this assumption the behavior of static bed catalytic reactors is studied. From these considerations it is deduced that there are three distinguishable types of behavior in decaying catalysts. These types are described in terms of their characteristic behavior and it is shown how the performance of certain rapidly decaying catalysts can be optimized in plant operation. On presente une discussion theorique de la diminution d'activite des catbalyseurs qui vieillissent; on suppose que l'activite du catalyseur n'est fonction que de la periode de duree du procede et, en se basant sur cette hypothese, on etudie le comportement des rAeacteurs catalytiques a lit statique. On deduit de ces considerations qu'il existe trois genres differents de comportement chez les catalyseurs qui vieillissent et on les decrit d'apres leur comportement caracteristique et respectif. On indique egalement comment on peut obtenir, dans le fonctionnement d'une usine, un rendement maximum avec certains catalyseurs dons l'activite decroit rapidement.

The ratio of terminal velocity to minimum fluidising velocity for spherical particles

Abstract: The analogy between the states of a particle falling at its terminal velocity in a fluid and that of a particle in a bed, at incipient fluidization by the same fluid, suggests the possibility of a correlating minimum fluidizing and terminal velocities and of predicting the minimum fluidizing velocity. A semi-theoretical curve has been obtained, relating (Ret/Remf) to Fn = gpF (rHS – rHF) d3/μ2 and it has been compared with new experimental data collected for this purpose in the range 103

Heats of mixing for binary systems: n-Alkanes + n-Alcohols and n-Alcohols

Abstract: The heats of mixingof 23 binary systems are reported at 20, 25 and 30°C. Of these systems, 14 binaries are mixtures of n-alcohols + n-alkanes and the remaining 9 systems are mixtures of n-alcohols. The applicability of an extension of the principle of congruence to the data was investigated. Lee chaleurs de demlange pour 23 systemes binaires noat presentees pour des temperatures de 20, 25 et 30°C. Dc ces sysemes, 14 binaires sont des melanges de n-alcools + n- alkanes et les 9 autres systsmes sont des melanges de n-alcools. Une evaluation d'une extension du principle de congruence a etc faite pour ees systemes.

On the conditions for stability of falling films subject to surface tension disturbances; the condensation of binary vapors

Abstract: Examination of available experimental information, including that on condensation of binary vapors, indicates that the Marangoni effect provides a consistent interpretation of falling film behavior, when surface tension disturbances are important. Criteria provided by the Marangoni effect are: d/db 0 for stability, where is surface tension and b film thickness, and d/db > 0 for instability; the latter is evidently a necessary but not sufficient condition. Methods are given for evaluating the sign of d/db in terms of the product of two factors, one characteristic of the system and one of the operation. L'examen des renseignements experimentaux disponibles (y compris ceux qui ont trait a la condensation des vapeurs binaires) indique que l'effet de Marangoni fournit une interpretation logique du comportement d'une pellicule qui tombe, lorsque les perturbations dans la tension superficielle sont importantes. Les criteres fournis par l'effet de Marangoni sont respectivement d/db 0 et d/db > 0, dans le cas de stabilite et d'instabilite ( designant la tension superficielle et b l'epaisseur de la pelli-cule); la seconde relation est evidemment une condition necessaire, mais insuffisante. On indique des methodes pour evaluer le signe de d/db d'apres le produit de deux facteurs, a savoir un qui caracterise le systeme et un autre l'operation.

Improved gas'liquid contacting in co‐current flow

Abstract: A new method of increasing interfacial area for gas-liquid contacting in co-current flow using screen packings has been evaluated in a 51/2-in. I. D. column using CO2 chemisortpion in sodium hydroxide solution and CO2 physical desorption from water. The study investigated the effect of gas velocity (0.3-2.7-ft/sec.), liquid velocity (0.018-0.1-ft/sec), and of column height (0.67-7.8-ft.) on the interfacial area, a, and the physical desorption liquid phase mass transfer coefficient, KL. The two types of screen packing tested produced interfacial areas of 2 to 4 times that generated in an unpacked column. KL showed no effect of gas velocity but increased with liquid velocity, a and KL decreased with increasing column height. Generally, photographic evaluation gave unrealistically high values of a. On a evalue une nouvelle methode pour augmenter la surface interfaciale de contact entre gaz et liquides dans un ecoulement concurrent; on a utilise a cette fin des garnitures poreuses dans une colonne (dont le diametre interieur etait de 51/2 pouces) ainsi qu'une chemisorption de CO2 dans une solution d'hydroxyde de sodium et une desorption physique de CO2 a partir de l'eau. On a etudie l'effet de la velocite du gaz (0.3-2.7 pieds a la sec), de la velocite du liquide (0.018-0.1 pied a la sec.) et de la hauteur de la colonne (0.67-7.8 pieds) sur la surface interfaciale a et le coefficient KL de transfert de masse de la phase liquide par desorption physique. Les deux sortes de garnitures poreuses dont on a fait l'essai ont produit des surfaces interfaciales 2 a 4 fois plus grandes que celles qu'on obtient dans une colonne nongarnie. Le coefficient KL n'a pas paru influence par la velocite du gaz, mais il s'est accrǔ avec la velocite du liquide. Les valeurs a et KL ont diminue et sens inverse de la hauteur de la colonne. En general, l'evaluation photographique a donne des valeurs elevees pour a qui ne correspondaient pas a la realite.

Flow of suspensions in pipelines(Part 2: Two Mechanisms of Particle Suspension)

Abstract: The distributions of suspended 24-28, 40-50, and 80-100 mesh sand particles and of 100-150 mesh nickel particles were measured by a gamma-ray absorption technique in a horizontal channel with a 0.972 x 3.976 in. cross section at mean mixture flow velocities of 4.24-12.61 ft/sec and at average dimensionless transport concentrations of 0.024-0.28; from these data, the eddy diffusivities were calculated. Turbulent suspension of the particles appeared to occur at low particle concentrations, at small particle diameters (less than 0.2 mm), and at particle settling velocity/flow friction velocity ratios of less than 0.2:1; outside these limits the concentration profiles deviated significantly from those usually associated with turbulent suspensions, which could be due to particle interactions. The eddy diffusivity in the equation governing the concentration profiles was found to be of the same order of magnitude as the eddy diffusivities for momentum and mass in single-phase fluids. High solid concentrations were found to increase the suspending capacity of the fluid, rather than to "damp" the turbulence. The results of this study can be extended to predict the solids concentration distributions in circular pipes.

Holdup and flooding in air liquid mixing

Abstract: The amount of flowing air held up, or retained, under the surface of water and corn syrup solutions was measured in cylindrical tanks of different sizes using turbine type mixing impellers. Holdup is frequently used as an index of the effectiveness of gas-liquid contacting in adsorption or stripping operations; it can be correlated with air flow rate and power input as follows h = a(PT/V)bFc where h is the holdup of air in ft. per ft. of ungassed liquid, a, b, and c, are constants, (PT/V) is the total power supplied by the impeller and air per unit volume, and F is the superficial velocity of the air. Values of a and b vary with tank size. The effect of liquid viscosity is pronounced but not amenable to simple correlations with the constants. Limits of operation to prevent flooding are defined as functions of impeller power and air flow. On a mesure, dans des reservoirs cylindriques de differentes dimensions et en utilisant des palettes a malaxage du genre turbine, la quantite d'air d'ecoulement qui etait retenue sous la surface de l'eau et de solutions de sirop de mais. On emploie frequemment la dite retention comma critere de l'efficacite du contact entre un gaz et un liquide dans des operations d'adsorption ou d'extraction; on peut etablir une correlation entre elle et la vitesse du debit de l'air et l'energie introduite en utilisant l'equation suivante h = a(PT/V)bFc ou h est la retention de l'air en pieds par pied de liquide depourvu de gaz; a, b, et c sont des constantes; (PT/V) est l'energie totale fournie par les palettes et l'air par unite de volume du liquide, et F est la velocite superficielle de l'air. Les valeurs de a et b varient avec les dimensions du reservoir. L'effet de la viscosite du liquide est prononce, mais ne se prěte pas a des correlations simples avec les constantes. On definit les limites d'operation pour empěcher l'injection en fonction de l'energie des palettese et de l'ecoulement de l'air.

Extractive distillation employing a dissolved salt as separating agent

Abstract: A process of extractive distillation, employing a dissolved salt rather than a liquid solvent as separating agent, was studied on a pilot plant scale. Aqueous ethanol was fractionated in a 12-tray, bubble cap column with potassium acetate present in the liquid phase. Even relatively small concentrations of salt eliminated the azeotrope. An overhead product completely free of separating agent was obtained directly from the column. A technique is described for metering salt at a steady rate, and for achieving rapid solution of the salt in the reflux stream. On a etudie dans une usine-pilote un precede de distillation extractive, en utilisant un sel dissous plutǒt qu'un solvant liquide comme agent de separation. On a fractionne l'alcool ethylique aqueux dans une colonne de douze plateaux et munie d'une calotte de barbottage en presence d'acetate de potassium dans la phase liquide. Des concentrations du sel, měme relativement faibles, ont elimine l'azeotrope. On a obtenu directement de la colonne un produit de těte de distillation qui ne contenait pas d'agent de separation. On decrit un procede pour mesurer le sel a une vitesse constante et pour le dissoudre rapidement dans le courant de reflux.

Power‐law fluids flow through multiparticle system

Abstract: A study on the flow of power-law fluids through a multi-particle system including both fixed bed and fluidized bed is presented. Equations for the pressure drop, the minimum fluidization velocity, and the bed expansion are obtained by extending the Blake-Kozeny's equation for the pressure drop through packed beds to power-law fluids. Bed expansion equations are also obtained by extending the Richard-son-Zaki's theory for the drag force in a multiparticle suspension to power-law fluids. These equations are compared with experimental data. On presente une etude de l'ecoulement des fluides d'entrainement dans un systeme a particules multiples forme a la fois de lits fixes et fluidises. On obtient des equations qui ont trait a la chute de pression a la velocite minimum de fluidisation et a l'expansion des lits, en etendant a des fluides d'entrainement l'equation de Blake-Kozeny relative a la chute de pression dans des lits garnis. On obtient egalement des equations pour l'expansion des lits en etendant a des fluides d'entrainement la theorie de Richardson-Zaki relativement a la force de trainee dans une suspension de particules multiples. On compare les dites equations avec des donnees experimentales.

Particle retardation in vertically oscillating fluids

Abstract: An analytic expression has been deduced for the ultimate velocity of a free particle in a vertically oscillating fluid by evaluating asymptotic forms of Floquet's solution to the Mathieu equation arising from the nonlinear Langevin equation describing the particle-fluid interactions. Using general Mathieu theory it has been rigorously demonstrated that directional particle motion in a gravitational field can be retarded by sinusoidal fluid oscillations when the particle-fluid drag law is of square form. The earlier Rayleigh-Ritz approximation (Houghton 1966) for the retarded particle velocity is shown to be in good agreement with the results of Mathieu theory, as summarized in graphical form. On a deduit une expression analytique, dans le cas de la velocite finale d'une particule libre et placee dans un fluide qui oscille verticalement; on l'a fait en evaluant des formes asymptotiques de la solution de Floquet a l'equation de Mathieu provenant de l'equation non-lineaire de Langevin, ou l'on decrit les reactions mutuelles entre la particule et le fluide. En utilisant la theorie generale de Mathieu, on a rigoureusement demontre qu'il est possible de retarder le mouvement dirige d'une particule dans un champ de gravitation, au moyen d'oscillations sinusoidales de fluide, lorsque la loi de traǐnee de la particule et du fluide s'exprime sous forme carree. On montre que l'approximation precedence de Rayleigh et Ritz (reference: Houghton, 1966), dans le cas de la velocite retardee des particules, concorde bien avec les resultats de la theorie de Mathieu, exprimes sommairement sous forme de graphique.

Velocity profiles and pumping capacities for turbine type impellers

Abstract: Velocity and angle profiles emanated by turbine type impellers were measured in both air and water using a hot wire anemometer probe and two and three dimensional pitot tubes. Pumping capacities were then calculated from the velocity data. The effect of the rotational speed and the dimensions of the turbine was investigated. On a mesure dans l'air et l'eau les profils de velocite et d'angle produits par une turbine a ailettes, en utilisant une sonde d'anemometre a fil chaud ainsi que des tubes de Pitot a deux ou trois dimensions. On a ensuite calcule les capacites de pom page a partir des resultats de velocite obtenus. On a egalement etudie l'effet de la vitesse rotative et des dimensions de la turbine.

Application of thermodynamics to the athabasca tar sands

Abstract: Significant changes in the interfacial areas often accompany transformations in highly dispersed systems containing oil, water, solid and gas phases. When such changes in area are considered, interfacial tension expressions diametrically opposed to the conventional criteria for oil spreading or de-wetting may result. Further modifications in the energetics criteria are obtained when the electrical contributions to the free energy of the system (resulting from the adsorption of ionic surfactants) are included.

Liquid hold-up and minimum fluidization velocity in a turbulent contactor

Abstract: Transient-response experiments have been performed in conjunction with bed expansion measurements to determine liquid hold-ups and minimum fluidization velocities in a 12-in. turbulent-bed gas-liquid contactor. The amount of liquid hold-up was found to be independent of gas velocity, but dependent upon both liquid rate and packing diameter in the same manner as reported for conventional fixed-bed absorbers. The data on minimum fluidization velocity, Gmf, which was interpreted in the present study as the maximum gas mass velocity at which the bed maintained its static height, showed a considerable variation with packing diameter, dp and liquid flow rate, L. A correlation of Gmf with dp and L was presented.

Dynamic response of a double effect evaporator

Abstract: The open loop dynamic response of a laboratory scale double effect evaporator has been adequately described by a simple mathematical model based on the unsteady state material and energy balances associated with the various elements of the system. Excellent agreement has been achieved between the experimentally determined response of the evaporator to large disturbances in steam rate and feed rate and the predicted response based on the digital computer solution of the non linear model.

Calculating complex chemical equilibria by an improved reaction‐adjustment method

Abstract: Improvements in calculating complex chemical equilibria have been obtained (1) by incorporating a convergence-forcer into the Cruise-Villars method (a reaction-adjustment method), and (2) by using a linear programming scheme to obtain an initial estimate of the equilibrium composition. Calculations on 50 problems show that the improved method is faster than the RAND method similarly modified (one that does not use stoichiometric equations). On a ameliore le calcul des equilibres chimiques complexes (1) en incorporant un dispositif a convergence forcee dans la methode de Cruise-Villars (un procede de reaction et de reglage) et (2) en utilisant un systeme de programmation lineaire pour obtenir une evaluation initiate de la composition de l'equilibre. Les calculs dans 50 cas demontrent que la methode amelioree est plus rapide que celle de Rand modifiee d'une maniere semblable (laquelle n'utilise pas d'equation stoechiomterique ).

The kinetics of oxidation of sodium sulphite

Abstract: The kinetics of the reaction of oxygen with sodium sulphite in aqueous solution without and with a catalyst of cobaltous sulphate have been studied by a flow thermal method The rate of reaction of oxygen and sodium sulphite was found to be first-order with respect to oxygen and variable order with respect to sulphite, and the promoting effect of cobaltous catalyst was proportional to its concentration A reaction mechanism has been proposed and a rate expression derived which is in good agreement with the experimental data On a etudie, au moyen d'un procede a base d'ecoulement thermique, la cinetique de la reaction entre ioxygene et le sulfite de sodium dans une solution aqueuse, en presence ou en iabsence de sulfate de cobalt comme catalyseur On a trouve que la vitesse de reaction entre l'oxygene et le sulfite de sodium etalt de premier ordre par rapport a ioxygene et d'ordre variable par rapport au sulfite, et que ieffet accelerateur du catalyseur etalt proportionnel a sa concentration On a propose un mecanisme de reaction et etabli une expression pour la vitesse qui concordent bien avec les resultats experimentaux

Qualitative and quantitative observations on the tubular reactor

Abstract: The tubular reactor in the steady state is considered for a single chemical reaction. It is shown that almost all of the qualitative features of the temperature and concentration profiles may be deduced from the equations themselves without solving them. Extensive numerical calculations are also presented both for the finite and semi-infinite reactor. Comparisons are made with the lumped constant system. It is shown that the solution for the semi-infinite reactor is always unique and serves as a bounding solution for all finite reactors with the same parameters. On considere. l'emploi d'un reacteur tubulaire dans un regime permanent dans le cas d'une reaction chimique simple. On montre qu'on peut deduire des iquations memes, sans les resoudre, tous les detaila qualitatifs qui ont trait aux profib de temperature et de concentration. On presente egalement des calculs d'envergure dana le cas des reacteurs finis et semi-infinis. On fait des comparaisons avec le systeme dee constantes en bloc. On montre quc la solution, dans le cas d'un reactenr semi-infini, est toujours unique et e'applique a tous ks reacteurs finis qui possedent lee memes parameres.

Laminar flow in regular polygonal shaped ducts with circular centered cores

Abstract: The method of least-squares fitting of harmonic functions to known boundary conditions has been employed to obtain closed-form solutions for laminar flow of an incompressible fluid through the constant area annulus between a regular polygonal duct and a centered circular core. The product of Fanning friction factor and Reynolds number has been determined for the entire range between the extreme case of no core and the other extreme case where the core touches the outerwalls. For the latter case, it is shown that when the number of sides of the polygon approaches infinity, f.Re approaches a minimum value of 6.22. The analysis of this case is further extended to corner angles less than 60°, the minimum imposed by an equilateral triangular duct. On a adapte la methode des moindres carres de fonctions harmoniques a des conditions-limites connues pour obtenir des solutions de genre ferme dans le cas de l'ecoulement laminaire d'un fluide incompressible par un anneau a surface constante, entre un conduit en forme de polygone regulier et un noyau circulaire et centre. On a determine le produit facteur de friction de Fanning et du nombre de Reynolds sur une echelle complete comprise entre deux extrěmes, a savoir l'absence de noyau et le contact du noyau avec les parois exterieures; on a demontre dans ce dernier cas que, lorsque le nombre des cǒtes du polygone approche l'infini, f. Re approche une valeur minimum de 6.22. On a etendu l'analyse de ce cas a des angles de coin inferieurs a 60°, qui est le minimum requis pour un conduit en forme de triangle equilateral.

Heats of mixing for ternary systems: n‐Alkanes + Two n‐Alcohols

Abstract: Heats of mixing for 21 ternary systems of one n-alkane + two n-alcohols are reported at 25°C. Evaluation of four equations permitting the prediction of heats of mixing of ternary systems from binary data is made. Scatchard's modified equation for systems containing a polar component was found to be the most accurate. Les chaleurs de melange pour 21 systemes ternairer composes de n-alkane + deux n-aleools sont presentees a 25°C. Une evaluation de quatre equations permettent de predire les chaleurs de melange des systemes ternaires a partir des donneea pour lee systemea binaires a etc faite. L'gquation modifiee de Scatchard pour dee aystemes contenant un eompose polaire permet de predire les meilleures valeura.

The effect of surface active agents on sorption isotherms of a model food system

Abstract: The extent of the capillary condensation phenomenon in the sorption of water by a model food system was studied. The system, composed of microcrystalline cellulose, a hydrocarbon oil, and water, was treated with non-ionic surface active agents at various concentrations. Desorption and adsorption isotherms were made for triplicate control and treated systems at 37°c., using a desiccator method. During desorption, the surfactants increased the water equilibrium vapor pressure of the model system for all moisture contents, but with adsorption, this effect was observed only up to 50 to 60% RH. The magnitude of the hysteresis loop was diminished in all cases. These over-all effects were due mainly to a lowering of the liquid surface tension of the water in the pores of the model. Capillarity was analyzed by the Kelvin Equation and existed down to 20% RH, which is close to the monolayer value for most models. In addition, data from low surfactant concentrations indicated that capillarity may extend even below the monolayer. The diminished hysteresis found in our experiments supports the “ink-bottle” theory of hysteresis. On a etudie l'amplitude du phenomene de la condensation capillaire lors de l'adsorption d'eau par un systememodele d'alimentation. Le dit systeme etait forme de cellulose microcristalline, d'une huile hydrocarbonee et d'eau; on l'a traite avec des agents tension-actifs du genre non-ionique a differentes concentrations. On a prepare des isothermes de desorption et d'adsorption pour le triple systeme de contrǒle et lea systemes traites a 37°c, en utilisant nne methode de dessiccation. Durant la desorption, les agents tensio-actifs ont augmente la preasion de vapeur d'eau d'equilibre du systeme-modele et ce pour toutes les teneurs d'humidite; toutefois, dans le cas d'adsorption, on n'a observe cet effet que pour des teneurs d'humidite relative atteignant 50 a 60%. L'importance de la boucle d'hysterese a diminue dans tous les cas. Les dits resultats etaient dus a un abaissement de la tension de surface liquide de l'eau dans les pores du modele. On a analyse la capillarite au moyen de l'equation Kelvin et trouve qu'elle existait jusqu'a un degre d'humidite relative de 20%, ce qui se rapprochait de la valeur pour couche simple dans le cas de la plupart des modeles. En outre, les resultats provenant de concentrations faibles d'agents sensio-actifs, ont indique que la capillarite pouvait s'etendre měme au-dessous de la couche simple. l'hysterese moindre qu'on a trouvee dans les experiences a confirme la theorie de “bouteilie d'encre” de l'hysterese.

Chlorine exchange resins

Abstract: : High polymers which contain a labile chlorine atom have been prepared. The active group in these polymers is the >NH or -NH2 group, which takes up chlorine from a chlorine-rich environment, and in the chlorinated form gives up chlorine to an environment deficient in chlorine, for example which exhibits a chlorine demand. The resins, which may be natural or synthetic, act as an agent for chlorine transfer to or from a medium. The results of a preliminary investigation of the utility of various polyamides and amino resins are given. Mass transfer rate studies of chlorine uptake by a urea-melamine-formaldehyde resin and of chlorine liberation from a chlorinated resin of the same type, the effect of pH on these rates, and the practical maximum chlorine capacities are presented. The stability of chlorinated resins is described. (Author)

Effect of various parameters on the level of mixing in continuous flow systems

Abstract: Variations of the level of mixing in a flow system have been investigated as a function of the following parameters: diameter, shape and speed of the agitator, feed rate and position of the feed inlet. At agitator speeds inferior to a critical value, a minimum level of mixing is observed which depends on the position of the feed inlet. At speeds superior to the critical value, the level of mixing increases linearly with agitator speed, at a given feed rate, until conditions of perfect mixing are reached. The critical agitator speed and the position of each straight line depend on the agitator size. A modified Reynolds number makes possible a more general correlation. At a given agitator speed, superior to the critical value, the level of mixing decreases as the feed rate increases, due to the smaller amount of energy imparted by the agitator per unit mass of feed. The effect of agitator shape on the level of mixing is rather pronounced as it affects the flow patterns inside the reservoir. On a etudie les variations du niveau d'agitation dans un systeme continu en fonction des parametres suivants: diametre, forme et vitesse de l'agitateur, debit d'alimentation et point d'entree de l'alimentation. Aux vitesses de l'agitateur inferieures a une valeur limite, on observe un niveau minimum d'agitation qui est fonction du point d'entree de l'alimentation. Aux vitesses superieures a la valeur limite, le niveau d'agitation croǐt lineairement avec la vitesse de l'agitateur, a un debit donne, jusqu'a ce que l'agitation soit parfaite. La grosseur de l'agitateur determine la vitesse limite de l'agitateur de měme que la position des droites obtenues. Un nombre de Reynolds modifie permet d'obtenir une correlation plus generate. A une vitesse de l'agitateur superieure a la valeur limite, le niveau d'agitation decroǐt avec un debit croissant en raison de la plus petite quantite d'energie fournie par l'agitateur par unite de masse de l'alimentation. On note une influence assez marquee de la forme de l'agitateur sur le niveau d'agitation par suite des effets differents sur le mode de circulation interne.

A steady'state capillary cell method for measuring gas-liquid diffusion coefficients

Abstract: A simple method for measuring diffusion coefficients of gases in liquids using capillary cells has been shown to give accurate results for the diffusivities of carbon dioxide in water, methane in carbon tetrachloride, and carbon dioxide in ethanol when compared with reported values. Diffusivities were also measured at 30°C. for ethane in n-hexane and ethane in n-heptane, and at 40°C. for ethane in n-heptane. The steady-state capillary cell technique appears to be capable of giving reliable diffusivities for a large number of gas-liquid systems. On a trouve qu'une methode simple, servant a mesurer les coefficients de diffusion des gaz dans des liquides et utilisant dee cellules capillaires, donnait des resultats preeis lorsqu'il s'agissait dcs diffusivites de l'anhydride carbonique dans l'eau, du methane dans le tdtrachlorure de carbone et de l'anhydride carbonique dans l'alcool ethylique, et qu'on comparait les dits resultats avee des valeurs deja rapportees. On a aussi mesure les diffusivites a 30°C., dans le cas de I'ethane dans I'hexane normal et dans l'hextane normal, et a 40°C. pour 1′ethane dans I'heptane normal. La methode a base de cellules capillairee et a regime permanent semble capable de fournir des valeurs fiables sur la diffusivite dana lc cas d'un grand nombre de systemes gae-liquide.

Filtration of non‐Newtonian fluids

Abstract: Equations of motion characterizing the flow of incompressible, time-independent non-Newtonian fluids, exhibiting the anomalous surface effect, through compressible porous media are developed. Approximations are made to arrive at workable filtration equations for slurries of non-Newtonian (power-law) fluids. The constant-pressure and constant-rate filtration relationships developed are verified experimentally using slurries of calcium carbonate in water and dilute CMC solutions. The anomalous surface effect is found to exist in the filtration of the non-Newtonian fluids. The specific cake resistance in the case of the non-Newtonian sludge and the ratio of the effective slip velocity to the pore velocity are found to be functions of both the CMC concentration and the pressure drop across the filter bed. On a mis au point des equations de mouvement caracterisant l'ecoulement des fluides non-newtoniens incompressibles et independents du temps, lesquels font voir l'effet d'une surface anormale dans des milieux poreux et compressibles. On a eu recours a des approximations pour mettre au point des equations assez satisfaisantes pour la filtration de suspensions epaisses de fluides non-newtoniens (loi d'energie). On a evalue experimentalement la correlation entre la filtration a pression constante et celle a vitesse constante, au moyen de coulis de carbonate de calcium dans l'eau et de solutions diluees de carboxymethyl-cellulose. On a trouve que l'effet de surface anormale existait dans la filtration de fluides non-newtoniens. On a aussi constate que la resistance specifique du cake de filtration, dans le cas d'un coulis non-newtonien et le rapport entre la velocite effective de glissement et la velocite des pores etaient fonctions a la fois de la concentration de la carboxymethylcellulose et de la chute de pression dans le lit filtrant.

Distribution of lengths in the breakage of fibres or linear polymers

Abstract: The distribution of fiber or polymer lengths during breakage is considered. It is shown that under certain conditions the distribution of lengths is given by a self-preserving form which is independent of the initial distribution and is not explicitly dependent on time. Some self-preserving distributions are calculated. The theory is compared with an experiment on the breakage of glass fibres caused by milling. On etudie la repartition des longueurs des fibres et des polymeres lors de leur rupture. On demontre que, dans certaines conditions, la repartition des longueurs apparait sous une forme automatiquement stable, laquelle est independante de la repartition initiale et ne varie pas explicitement avec le temps. On calcule certaines repartitions automatiquement stables et compare la theorie avec une experience sur le bris des fibres de verre par broyage.

An experimental investigation of heat transfer to water in film flow Part I – non‐boiling runs with and without induced swirl

Abstract: Local heat transfer coefficients have been measured in the range of Reynolds Numbers 3,000-20,000 for non-boiling heat transfer to water flowing down the inside of a copper tube. The tube was 0.948-in. Inside diameter and 8-ft long, heated in 15 sections 6-in. long, by electrical resistance heaters wound on the outside of the tube. Thermocouples measured the wall temperature at the midpoint of each section. Coefficients obtained for downward, non-swirling, full tube flow were correlated by the Dittus Boelter equation, with a correction for heat flux. An experimental correlation was obtained for the improved coefficients resulting from the use of a swirl generator in full tube flow. Non-swirling falling film data were correlated by an equation: hLA = 3.9 ReLA0.05 It is to be noted that the exponent on ReLS is higher than the value of 0.1-0.33 found by previous workers. The effect of swirl on falling film heat transfer was complex; increased coefficients were noted at ReL below 10,000 but much reduced coefficients were obtained at RL above 15,000 in the lower parts of the tube. On a mesure des coefficients de transfert local de la chaleur, sur une ehelle de nombree de Reynolds de 3,000 a 20,000, dans le cas d'une transmission de chaleur (a une tempdrature qui n'est pas celle de l'ebullition) a de I'eau qui s'eoule vers le bas i I'interieur d'un tube de cuine. On a chauffd le dit tube, qui eveit un dinmetre intdrieur de 0.948 pouces et une longueur de 8 pieds, dans 15 sections de 6 pouces de longueur nu moyen de rechauffeurs electriques 1 resistance entourant l'extdrieur du tube. On a mesurd, nu moyen de thermo-couples, la temperature des parois nu point moyen de chaque section. On a etabli, au moyen de I'equation de Dittus Boelter, une correletion entre lee coefficients qu'on a obtenus pour 1′ecoulement non-tourbillonnant vers le bas, sur toute l'etendue du tube en effectuant une correction pour le flux de la chaleur. On a obtenu une corrdlation experimentale pour les coefficients ameliores qui resultent de l'emploi dhn generateur de toarbillion dans I'ecoulement sur toute I'etendue du tube. On a dtabli une correlation entre les resultats de la pellicule qui tombe sans tourbillon, nu moyen de l'equation saivante: hLA = 3.9 ReLA0.05 11 faut noter que l'exposant de ReLa a une valeur plus grande que celle de 0.1-0.33 qu'ont deja trouvee d'autres travailleure scientifiques. L'effet du tourbillon sur le trans- fert de la chaleur de la pellicule qui tombe s'est avere complexe; on a note des Coefficients PIUS considirablea lorsque la valeur de ReL etait inferienre i 10.000, mais on a obtenu des coefficients bien moindres lorsque sa valeur exc6dait 15,000 dans lee partiea infdrieures du tube.