bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of mass transfer on solid‐catalyzed reactions: The dehydrogenation of cyclohexane to benzene
Authors: Barnett L. G. , Weaver R. E. C. , Gilkeson M. M. 
Published: June 2004

AbstractThe reaction of gaseous components at a solid catalytic surface has long been a subject of prime engineering interest. Generally speaking one expects the reaction velocity constant to follow the Arrhenius exponential temperature dependence. However as the reaction temperature increases, the intrinsic reactivity of the surface will increase and mass transfer begins to limit the rate of the reaction. In the case of a porous solid catalyst, where most of the active surface is on the catalyst pellet interior, the rate‐limiting process will frequently be internal diffusion, and in such a case the milder effect that temperature has on the diffusion process is the one observed in the gross kinetics, rather than the exponential Arrhenius dependence.The study reported here has examined the kinetics of the dehydrogenation of cyclohexane to benzene over a platinum‐on‐alumina pelleted catalyst. This is a notorious problem system, and in seeking to describe the observed rate data the authors provided a stern test for an analytical model treating the coordinate diffusion and reaction mechanisms. In particular the parameter of particle size was studied over a temperature range of from 640° to 910°F. For these runs reactor pressure was held constant at essentially 200 lb./sq. in. gauge (14.7 atm.), und the feed was maintained at 20 mole % cyclohexane, 80 mole % hydrogen.
Boundary‐layer behavior on continuous solid surfaces: II. The boundary layer on a continuous flat surface
Authors: Sakiadis B. C. 
Published: June 2004

AbstractThe laminar boundary‐layer behavior on a moving continuous flat surface is investigated by two methods. One method involves the numerical solution of the boundary‐layer equations. The other is an integral method, based on an assumed velocity profile that satisfies the appropriate boundary conditions. Good agreement is obtained between the results of these two methods of solution. The turbulent boundary‐layer behavior on a moving continuous flat surface is investigated by the integral method only. Equations for the boundary‐layer thickness, displacement thickness, momentum thickness, and skin friction are presented for both laminar and turbulent boundary layers. Comparison is made with the boundary‐layer behavior over a flat plate of finite length.
The effect of vibration on natural convective mass transfer
Authors: Lemlich Robert , Levy Martin R. 
Published: June 2004

AbstractSmall horizontal cylinders subliming to room air were vibrated in a vertical direction at 20 to 118 cycles/sec. Increases of up to 660% in the coefficient of mass transfer were thus obtained. The coefficient increased with both frequency and amplitude, the latter having the more pronounced effect. Results are correlated in terms of the stretched vibrational Reynolds number introduced in an earlier study and compared with the analogous case of natural convective heat transfer.
Effective thermal conductivity in packed beds
Authors: Gopalarathnam C. D. , Hoelscher H. E. , Laddha G. S. 
Published: June 2004

AbstractValues of the effective thermal conductivity Ke for liquids in packed beds have been obtained from heat transfer studies in such beds. The method applied by Yagi and Kunii for gases is darified, their model is extended and is then applied to liquids. Experimental data for three different packings, glass, steel, and aluminum, with spheres of DP/DT ratio from 0.07 to 0.33 have been correlated. A brief comparison of the results from this analysis with previously published results from similar studies is presented.
Optimization of process performance
Authors: Lapidus Leon , Shapiro Eugene , Shapiro Saul , Stillman R. E. 
Published: June 2004

AbstractThe growing availability of fast, large memory digital computers has made it practical to consider the physical implementation of control system designs incorporating appropriate strategies for automatic process optimization. The control system is taken to consist of the process to be optimized together with the interconnected digital computer. The control strategy is realized in the program of the digital computer. In the present paper a number of such programs or algorithms are discussed for carrying out a search of the possible settings of the process input (independent) variables in such a way as to locate an extremal of the possible values of a chosen objective function. The magnitude of these variables is determined from measurements taken of the dependent variables in the process. It is shown that for the particular process used as an example it is desirable to alter the search strategy as the optimization proceeds in order to locate the extremal in a minimum amount of time. The emphasis at the beginning of the search is on speed in moving towards the optimum and at the end on accuracy.Further, a computational technique is described whereby the dynamic response of the process to the various search steps (or settings) is under time‐optimal control. This procedure is important for the fast execution of the search programs and consequent rapid location of the extremal of the chosen objective function.
Solid‐liquid phase behavior of binary solutions at elevated pressures
Authors: Winnick Jack , Powers J. E. 
Published: June 2004

AbstractThe formation of a solid phase as the result of isothermally increasing pressure on a binary solution is analyzed from a thermodynamic point of view. Exact thermodynamic equations are presented for the case in which there are no more than one liquid and one solid phase in equilibrium for the entire range of compositions. Approximate relations incorporating the additional assumption of ideality in both solid and liquid phases are also presented. Experimental data for the system ethylene bromide‐ethylene chloride are reported and compared with predicted values. Incomplete data for the system benzene‐n‐heptane are also reported.
Relationship between pellet size and performance of catalysts
Authors: Beek John 
Published: June 2004

AbstractThe effect of mass transfer resistance in reducing the effectiveness of porous catalysts has been known since the publication of Thiele's classical paper in 1939. The variation in temperature caused by resistance to heat transfer may bring about equally significant changes in effectiveness in some cases. An extension of Thiele's treatment to take exact account of heat transfer resistance leads to a set of nonlinear differential equations that can only be solved numerically.This paper presents an approximate treatment of the simulataneous effects of resistances to mass and heat transfer. With the limitations imposed by linearizing the equations the formulas derived give the activity and selectivity for any combination of reactions. The use of the results is illustrated by three examples. It is shown that the principal effects are associated with the variation of concentration within the pellet of catalyst and with the difference in temperature between the surface of the pellet and the bulk fluid.
Isothermal growth of hydrogen bubbles during electrolysis
Authors: Westerheide D. E. , Westwater J. W. 
Published: June 2004

AbstractThe investigation was concerned with measuring growth rates of bubbles in an isothermal medium where growth is controlled by mass diffusion. The conditions were met by generating hydrogen bubbles at a platinum cathode during the electrolysis of water. Growth data were obtained by motion picture photography at 800 to 2,400 frames/sec. taken through a microscope to produce an enlargement of 30X on the film.Growth took place in 0.1 normal and 1.0 normal sulfuric acid in water at 77°F. Current densities between 0.1 and 0.2 amp./sq. cm. were used. The observed diameters were all less than 0.006 in., and the growth times were less than 2 sec. Beside growth phenomena interesting features recorded included the coalescence of bubbles, the jumping of bubbles off the solid and then back again, and the slip of the bubble contact at the solid surface.Some bubbles grew with their radii proportional to the square root of time as predicted theoretically by Scriven. For these bubbles the calculated supersaturation of hydrogen in the solution was found to be from eight to twenty‐four times the concentration at saturation.
A study of entrainment, perforated plate column—air‐water system
Authors: Bain Jesse L. , Van Winkle Matthew 
Published: June 2004

AbstractA correlation has been developed interrelating entrainment as a function of plate spacing, weir height, hole size, liquid rate, and gas rate with a section of a 30‐in. diameter column and the air‐water system. The correlation is empirical, but approximately 90% of the over 900 points of data fall within ± 25% of the correlation. Hole diameters of 1/16 to 1/4 in., weir heights from 0 to 2 in., plate spacing from 12 to 24 in., gas rates from 770 to 1,700 lb./hr./sq. ft., and liquid rates from 2,800 to 12,000 lb./hr./ft. of weir length were studied as variable. Entrainment was found to increase with gas rate, decrease with weir height, increase with hole size, decrease with plate spacing, and could increase or decrease because of interaction effects as the liquid rate increases.
A study of iterative optimization
Authors: Rudd Dale F. , Aris Rutherford , Amundson Neal R. 
Published: June 2004

AbstractA process is considered in which the inputs to the system are stationary random ergodic functions. From the spectral densitities of the inputs and cross‐spectral densities of inputs and outputs a local linearized model of the process is obtained through the transfer function. There results then a maximum problem involving an objective function and constraints imposed by the model and the physical and arbitrary restraining conditions. Two special cases are solved in detail in which the maximum problem reduces to a linear programing problem. Other methods are needed for the general problem.
Application of the Kihara potential to high pressure phase equilibria
Authors: Prausnitz J. M. , Keeler R. N. 
Published: June 2004

AbstractThis paper is concerned with the virial equation of state as applied to vapor mixtures at moderate densities. The required virial coefficients for small molecules can usually be estimated from generalized corresponding states correlations, but these correlations are not sufficient for mixtures which contain one very heavy and one very light component. It is shown that for such mixtures the necessary virial coefficients can be calculated by statistical thermodynamics with a potential function proposed by Kihara. This type of calculation is especially useful at low temperatures where virial coefficients have not been measured because of large experimental difficulties. Application of the Kihara potential is demonstrated with the computation of K values for heavy components for several mixtures at advanced pressures; good agreement with experimental results is obtained.The virial equation may in some cases be used to test data for thermodynamic consistency, and for illustration it is shown that recently reported K data for propane in compressed hydrogen are thermodynamically inconsistent and too large by about two orders of magnitude.
Saturated liquid densities for binary hydrocarbon systems
Authors: Phillips Edward M. , Thodos George 
Published: June 2004

AbstractThe extension of the rules proposed by Cailletet and Mathias for the sum of the saturated vapor and liquid densities and by Guggenheim for the difference of these densities enabled the development of a method for the prediction of liquid densities for binary hydrocarbon systems at saturated conditions. The theorem by corresponding states indicated that unique relationships should exist between the reduced temperature and the sum and difference of the reduced saturated liquid density and the reduced saturated vapor density.Density data reported by Kay for the systemsn‐butane—n‐heptane, ethane—n‐butane, ethane—n‐heptane, and ethane—cyclohexane were used to determine the exponents and the coefficients of the resulting equations. The exponents were found to be functions of two temperature parameters, which take into account both the components and composition of the mixture, while their coefficients have been found to depend only on their exponents.It has been previously shown that critical temperatures of binary hydrocarbon systems can be predicted with the two temperature parameters. In this study it has been found that these two parameters can also be applied to determine the critical densities for these binary hydrocarbon systems. Using these critical properties one can directly obtain the saturated liquid densities of binary systems from the two reduced‐density relationship.The method developed in this work reproduces the saturated liquid densities of the four systems within 4.8%. In addition saturated densities have been calculated for the ethylene—n‐heptane system and checked the experimental values within 3.2%.Because saturated vapor densities are small compared with the saturated liquid densities for conditions removed from the critical point, the sum and difference of the liquid and vapor densities are approximately the same. Thus this method cannot be used with any reliability to determine the densities of saturated vapors.At present this method can be applied only to hydrocarbon mixtures whose atmospheric dew point does not exceed twice its atmospheric boiling point.
Mass transfer in the flow of gases through fluidized beds
Authors: Riccetti Richard E. , Thodos George 
Published: June 2004

AbstractMass transfer studies were conducted for the flow of air through fluidized beds. These studies were concerned with the sublimation of p‐dichlorobenzene spherical particles, approximately 0.04 to 0.08 in. in diameter, and with the evaporation of nitrobenzene and water from alumina spheres. 0.1168 in. in diameter.Void volumes for these fluidized beds were calculated from pressure‐drop measurements. The results of this investigation were used to establish mass transfer factors which were in agreement with values obtained for fixed beds for corresponding modified Reynolds numbers, DpG/μ(1‐ε).
The laminar nonisothermal flow of non‐Newtonian fluids
Authors: Hanks Richard W. , Christiansen Ernest B. 
Published: June 2004

AbstractThe equations which describe the process of simultaneous heat and momentum transport are solved to obtain the pressure loss‐flow rate relation for the laminar flow of pseudoplastic liquids through a smooth heated pipe. The rheology of the liquids is characterized by a temperature‐reduced form of the empirical Ostwald‐deWaele or power law equation.Two solutions to the basic equations are presented, a numerical integration of the heat conduction differential equation and an approximate solution based upon a simplified model of the temperature profile.Experimental data obtained with eighteen different pseudoplastic solutions and the limited data available from the literature are compared with theoretical predictions and are correlated over a 5,000‐fold range of friction factors and pseudoplastic Reynolds numbers with a standard deviation of 7.9%.
Swirling flow in cylinders
Authors: Nissan Alfred H. , Bresan V. P. 
Published: June 2004

AbstractThe presence of vortex motion in a vertical cylinder in which water is passed upward can result in three types of velocity profiles: net upward motion at all points in the tube, an ascending outer annulus and a descending central core, and outer annulus and central core ascending and an intermediate annulus descending.All three types of velocity profiles are functions of three factors: the tangential velocity, the manner of decay of the tangential velocity, and the wall pressure drop. A fourth factor, boundarylayer growth, is proposed to explain the third type of profile. Experimental work was carried out to prove the mechanisms proposed for the first two types of profiles. Photographic observations were taken showing the existence of the third type.
Kinetics of reduction of ferrous oxide with hydrogen in a fluidized bed at steady state
Authors: Feinman Jerome , Drexler Thomas D. 
Published: June 2004

AbstractThe kinetics of the reduction of ferrous oxide with hydrogen in a steady state fluidized bed have been correlated with a rate equation based on a reaction controlled at the oxide‐metal interface and on a differential material balance which assumes that a close approach to piston flow prevails. The correlation gives an enthalpy of activation of 29,500 b.t.u./lb. mole for the reaction, which is in good agreement with McKewan's reported value of 27,500 b.t.u./lb. mole. The relationships developed are used to predict the effect of the important independent variables on the over‐all kinetics of the system.
Heat transfer from acoustically resonating gas flames in a cylindrical burner
Authors: Zartman W. N. , Churchill S. W. 
Published: June 2004

AbstractHeat transfer from premixed propane‐air flames to the cooled wall of a 5‐in. I.D. ramjet type of burner was studied with and without flame‐generated, sonic oscillations. Frequency and amplitude measurements revealed that both transverse and longitudinal waves were resonant. The heat flux to the wall was increased significantly by the oscillations, but the gas temperature profile was changed very little. The local heat transfer coefficient was found to be a linear function of the sound pressure amplitude and independent of the mode and frequency of the resonant oscillations.
The viscosity of nonpolar gases at normal pressures
Authors: Stiel Leonard I. , Thodos George 
Published: June 2004

AbstractExperimental viscosity data available in the literature for fifty‐two nonpolar gases have been utilized in conjunction with a dimensional analysis approach to relate the viscosity at atmospheric pressure to temperature. The substances investigated are both simple and complex and include the inert and diatomic gases, carbon dioxide, carbon disulfide, carbon tetrachloride, and the hydrocarbons up ton‐nonane, including normal and isoparaffins, olefins, acetylenes, naphthenes, and aromatics. The dependence of the product μ*ξ on reduced temperature was found to be the same for all of these substances, except helium and hydrogen.Both theoretical considerations and dimensional analysis indicate that the viscosity product of a gas might depend on the compressibility factor at the critical point. However the results of this study show that for these nonpolar substances this viscosity product at normal pressure is independent ofzcand depends only on temperature.The only information required for the calculation of viscosity with the relationships developed in this study is the molecular weight, critical temperature, and critical pressure of the substance. Values calculated with these relationships have been compared with 785 experimental points from all reliable sources of experimental data and produced an average deviation of 1.77%. Comparisons have also been made with the values calculated with the Licht‐Stechert and Bromley‐Wilke equations.
The measurement of rapid surface temperature fluctuations during nucleate boiling of water
Authors: Moore Franklin D. , Mesler Russell B. 
Published: June 2004

AbstractThe surface temperature during nucleate boiling was measured with a special thermocouple so designed as to measure the temperature of a small area and to have an extremely rapid response time. The surface temperature was found to drop occasionally 20° to 30°F. in about 2 msec. during the boiling of water. This indicates a rapid extraction of heat during a short time interval. The significance of this observation is that it provides an important new clue to an understanding of nucleate boiling. A hypothesis is advanced to explain these observations.
The effect of organic substances on the transfer of oxygen from air bubbles in water
Authors: Eckenfelder W. Wesley , Barnhart Edwin L. 
Published: June 2004

AbstractThe liquid film coefficient is related to bubble diameter and velocity in pure water and to the physical properties of the liquid. The addition to water of organic substances which influence the surface tension and viscosity will decrease the size of the air bubble released from a diffuser and reduce the transfer of oxygen into the solution. The maximum reduction in oxygen transfer occurs in the region of maximum surface tension change. The effect of the addition of several organic substances on the oxygen transfer characteristics are shown.
Energy balances in solar distillers
Authors: Lof G. O. G. , Eibling J. A. , Bloemer J. W. 
Published: June 2004

AbstractThere has been considerable doubt as to the manner in which the productivity of solar stills is affected by many of the designs and operating variables. To assist in designing solar stills of improved performance, theoretical equations are derived to describe the complete energy and mass transfer relationships involved in the operation of the basin type of solar still. These are supplemented with data from field operation of a 2,500‐sq. ft. still. With these relationships and the aid of a digital computer, the effects of variations of design parameters on the performance of solar stills is predicted. Distiller productivity is correlated with atmospheric temperature, wind velocity, solar radiation, absorptivity and slope of transparent cover, and other variables. Curves showing the magnitude of the effects of design changes on cover temperature, brine temperature, and productivity are presented.
A thermodynamic correlation of gas solubilities
Authors: Prausnitz J. M. , Shair F. H. 
Published: June 2004

AbstractLow‐pressure solubility data have been correlated for eleven gases in nine solvents over a wide temperature range by considering the dissolution process in two steps. First the gas is condensed isothermally to a hypothetical liquid at 1 atm. pressure, and then this hypothetical liquid is dissolved in the solvent. The free energy of the first step depends only on the properties of the solute, which in the case of nonpolar gases can be adequately described by the theorem of corresponding states. The second step depends on the properties of both solute and solvent and, in the case of nonpolar systems, can be described by the theory of regular solutions. The correlation depends on three solute parameters: the solubility parameter, the molar volume, and the fugacity of the hypothetical liquid; the last of these has been plotted as a generalized function for the reduced temperature range of 0.7 to 3.2. A separate plot is given for hydrogen. These parameters may be used to make good estimates of low‐pressure gas solubilities (or K values) in nonpolar solvents over a wide range of temperature.A semiempirical method for correlating the solubilities of gases in polar solvents is also described and illustrated for several cases.Since the correlation presented in this paper covers a wide temperature range, it is possible to make estimates of the heats of solution of gases in liquids. These may be useful in enthalpyblance calculations as required in certain phase‐separation operations.
Temperature gradients in turbulent gas streams: Effect of viscous dissipation on evaluation of total conductivity
Authors: Venezian Emilio , Sage B. H. 
Published: June 2004

AbstractValues of the total conductivity in a turbulently flowing air stream were originally reported without regard to the effects of viscous dissipation upon the results. By utilizing measurements of the shear taken at the time of the original study, the reported values of total conductivity were corrected for the effect of viscous dissipation. The effect of such dissipation upon the values of total conductivity is the greatest under conditions involving small temperature gradients and high Reynolds numbers.