bluuebunny/crossref_metadata_2025 huggingface dataset:
Local and average interphase heat transfer coefficients in a randomly packed bed of spheres
Authors: Gillespie Bernard M. , Crandall Edward D. , Carberry James J.
Published: June 2004

Local and average heat transfer coefficients have been measured for a sphere in a randomly packed bed. A steady state technique was employed in which internally heated spheres were placed in a bed 35 in. deep and 12 in. sq. Air passed through the bed in downflow, the range of Reynolds numbers being from 120 to 1,700 based on the sphere diameter and the superficial velocity.

Average heat transfer coefficients have been measured at twenty‐five positions permitting the assessment of the effect of position. An entrance region limited to the first two particle layers in the bed has been verified.

Distributions of the local heat transfer coefficient on the surface of a single sphere in the top layer and in the nineteenth layer of the bed have also been measured. These distributions indicate that a laminar boundary layer exists over portions of the sphere surface.
Response of a tubular heterogeneous catalytic reactor to a step increase in flow rate
Authors: Lehr Carl G. , Yurchak Sergei , Kabel Robert L.
Published: June 2004

The vapor phase dehydration of ethanol to diethyl ether, as catalyzed by ion exchange resin, has been studied experimentally and theoretically for the transient state period following a step increase in flow rate. A mathematical model is developed to account quantitatively for the effects of adsorption and surface reaction on the product distribution in the effluent of a tubular reactor. The solution of the model is in good agreement with the experimentally observed behavior.
Methods for solving the boundary layer equations for moving continuous flat surfaces with suction and injection
Authors: Fox V. G. , Erickson L. E. , Fan L. T.
Published: June 2004

Several methods that can be used to obtain solutions to the laminar boundary layer momentum, energy, and diffusion differential equations for moving continuous flat surfaces with suction and injection are presented. Results are obtained for a wide range of the injection parameter, f(0), at Prandtl and Schmidt numbers of 1, 10, and 100. Those methods which permit hand calculation of the properties of interest are compared using the numerical solutions of the boundary layer differential equations as the exact solutions. The new integral method of Hanson and Richardson which gives results for the momentum thickness that deviate less than 2.2% from the exact values is recommended for predicting values of the momentum boundary layer parameters. The Von Karman‐Pohlhausen method, which was modified to account for suction and injection, is most generally valid. This method gives acceptable values of the transfer coefficients for heat, mass and momentum transfer for most of the values considered.
Thermodynamic properties of binary mixtures of I‐hexyne and polar organic solvents
Authors: Harris H. G. , Prausnitz J. M.
Published: June 2004

Vapor‐liquid equilibrium data for polar solvent‐hydrocarbon mixtures are relatively plentiful for paraffins and aromatics; they are somewhat less plentiful for olefins. However, almost no data at all have been published for such mixtures wherein the hydrocarbon possesses a triple bond. This paper reports vapor‐pressure measurements of binary mixtures of 1‐hexyne with acetone, acetonitrile, dimethyl carbonate, nitroethane and dimethyl formamide in the temperature range 0 to 70°C. The results are compared with those for polar solvent‐hydrocarbon mixtures wherein the hydrocarbon is paraffinic, olefinic, or aromatic.
Form factors for deformed spheroids in stokes flow
Authors: O'Brien Vivian
Published: June 2004

Closed analytic Stokes flow solutions for general shapes are quite improbable, but semianalytic numerical procedures allow flow calculations for a variety of shapes. The change in drag with change in shape from a sphere, here expressed in terms of a form factor, is discussed and compared to empirical shape factors developed from sedimentation experiments.
Iterative techniques in optimization I. Dynamic programming and quasilinearization
Authors: Lee E. Stanley
Published: June 2004

The quasilinearization technique is used to overcome the dimensionality difficulties of dynamic programming. The approach is based on the fact that if the difference or differential equations are linear, their closed forms ofsolution can be obtained. This solution permits us to separate the effects due to the initial state from the effectsdue to the control variables. By using this separation combined with quasilinearization, the dimensionality of the functional equation of dynamic programming can be reduced to one in most cases. First, the optimization problem in cross‐current extraction with discontinuous objectionfunction is used to illustrate the technique. Then the technique is generalized to systems of difference and differential equations with fairly general objective functions.
An approximate solution for countercurrent heat exchangers
Authors: Tien Chi , Srinivasan Seshadri
Published: June 2004

An approximate solution is presented for the countercurrent parallel plate exchanger with laminar flow. With the use of the integral method, the problem is reduced to one of solving a pair of first‐order differential equations in a straightforward manner. Comparisons between the results of this work and those obtained from a more elaborate orthogonal expansion technique are found to be excellent.
Liquid film flow‐rates in two‐phase flow of steam and water at 1000 lb./sq. in. abs
Authors: Singh Kuldip , Pierre C. C. St. , Crago W. A. , Moeck E. O.
Published: June 2004

A knowledge of liquid‐film flow rates is important for design purposes when accurate predictions are required of the conditions under which dryout heat flux occurs in nuclear reactors and boilers. Liquid‐film flow rates were measured for a steam‐water mixture in cocurrent, upward annular flow in a tube at a pressure of 1,000 lb./sq.in.abs. Sinters located at the test section exit were used to extract the liquid film after the method of the Harwell group. Sinter lengths of 2, 1, and 1/2 in. were employed to investigate the effect of length on the extracted liquid flow rates. The test section was a stainless steel pipe of inside diameter 0.493 in., approximately 200 diam. in length. The total mass flux ranged from 0.2 to 0.7 × 106 lb.m/hr.sq.ft. and the quality varied from 0.3 to 0.92.

The experimental film flow rates were found to increase with decreasing quality. In the range of parameters investigated, the curves of film flow rate at constant quality vs. mass flux showed a maximum at a fixed value of steam velocity. At the same total mass flux and quality the film flow from the 1/2 in. sinter was lowest, suggesting that the crests of high amplitude roll waves overshot the sinter. Film flow rates were consistently higher than the theoretical predictions using Levy/s model. About one‐third of the measured flow rates were twice as high as predicted.
The estimation of parameters for a commonly used stochastic model
Authors: Sweet A. L. , Bogdanoff J. L.
Published: June 2004

A region into which particles arrive in a random manner, remain a random amount of time, and then leave is considered. This model is used in penetration theories of heat and mass transfer. From observations of the number of particles present at any time, it is desired to estimate arrival and exit statistics, residence time statistics, and average rates of transfer across the region. Assuming arrival is a Poisson process, equations governing the above statistics are derived. Some problems in spectral analysis arising from the use of nondifferentiable stochastic processes are solved. Estimators for important parameters are discussed, and it is shown that generally they are biased. A derivation linking the rate of transfer across the region with the rates of transfer of particles is obtained and compared with other such results.
The direct determination of the effect of pressure on enthalpy of a mixture of methane and propane
Authors: Mather A. E. , Powers J. E. , Katz D. L.
Published: June 2004

A new throttling flow calorimeter has been incorporated into the recycle facility of the Thermal Properties Laboratory. Energy is added to the expanding gas while it flows through a stainless steel capillary tubing from an insulated resistance wire located inside the entire length of the capillary. The calorimeter is designed to operate at pressures up to 2,000 lb./sq.in.abs. in the temperature range from −240 to +250°F.

Data on the isothermal effect of pressure on enthalpy for a mixture containing 5 mole % propane in methane are presented and compared with data from the literature.
Transport of toluene through fully swollen polyethylene
Authors: Coughlin Robert W. , Pollak Frank A.
Published: June 2004

Experiments have been carried out to measure the permeation of tritium‐labeled toluene through polyethylene films fully swollen with chlorobenzene, mesitylene, cumene, toluene, ethylbenzene, cyclohexane, tetrahydronaphthalene, and decahydronaphthalene. The results show characteristic Arrhenius temperature dependence over the range 25 to 40°C. The permeation of toluene through the films appears to be enhanced by increased solubility of the swelling agent (estimated from the work of others) in the film and there also appears to be a rough correlation between permeability of toluene and the boiling points and vapor pressures of the swelling agents. The range of permeabilities measured at 25°C. is 2.09 × 10−7 to 0.51 × 10−7 sq.cm./sec., the extremes of measured permeation activation energy, Ep, are 11.41 to 16.68 kcal./mole, and the pre‐exponential factor, Po, falls within the interval 36.59 to 1.29 × 105 sq.cm./sec. A very definite linear relationship or compensation effect is evident between Po and Ep. Except as mentioned above, none of these quantities appears to correlate uniformly with the following properties of swelling solvent: molecular weight, dipole moment, specific gravity, vapor pressure, boiling point, heat of vaporization, critical temperature, viscosity, surface tension, molar volume, molecular area or other molecular dimensions.
Effects of ultrasonic vibrations on heat transfer to liquids by natural convection and by boiling
Authors: Wong S. W. , Chon W. Y.
Published: June 2004

The effects of ultrasonic vibrations on heat transfer to water and methanol by natural convection and by boiling were measured at three ultrasonic energy levels with frequency ranging from 20.6 to 306 kcycles/sec., using electrically heated platinum wires of diameters 0.007 and 0.010 in. Up to an eight‐fold increase in heat transfer coefficient was obtained in natural convection, but the effects diminished with increased temperature difference and became negligible in the well‐developed nucleate boiling region. High‐speed photographs showed that the increase was due to the motion of cavitation bubbles on the wire surface. The heat transfer results were correlated by local cavitation activity values measured by a technique developed for this work.
Stable explicit difference approximations to parabolic partial differential equations
Authors: Liu Shean‐Lin
Published: June 2004

A finite‐difference method is developed for numerical solution of parabolic partial differential equations. This technique is explicit and stable. It is shown that the present method is more accurate and faster, in terms of computer time, than the Crank‐Nicholson method. A method of handling nonlinear problems is also presented. Two examples are given to illustrate the present technique. The first problem is a linear diffusion equation. The second problem deals with two simultaneous nonlinear parabolic partial differential equations with Neumann boundary conditions describing the steady state of a packed‐bed catalytic reactor with radial mixing.
Optimization of complex chemical plants by a gradient technique
Authors: Lee E. Stanley
Published: June 2004

The gradient technique and Lagrange multiplier are used to obtain the optimum of complex chemical plants. The advantage of this approach is its ability to handle nearly all types of complex stages in a natural way. This approach is used to solve a heterogeneous complex chemical process with recycle. It is shown that although there are many different iteration loops, the convergence rate is fast even with rough starting values and only 0.3 minute is needed to obtain the optimum operating conditions.
Mass transport in porous materials under combined gradients of composition and pressure
Authors: Gunn Robert D. , King C. Judson
Published: June 2004

An expression is derived for the analysis of gas‐phase mass transport in porous media in the presence of gradients in pressure and mole fraction. The behavior of porous media is contrasted with that of capillary tubes. A continuous‐flow diffusion and permeation apparatus was employed for studies of mass transport in a fritted glass diaphragm. Measurements were obtained at varying levels of pressure and cover both isobaric binary diffusion and the permeation of pure gases and gas mixtures. These experimental results and previous data obtained by Hewitt and Sharratt and by Mason, et al. bear out the form of the equation and successfully provide independent checks of the three constants necessary to characterize a given porous medium.
Drying polymers during screw extrusion
Authors: Coughlin R. W. , Canevari G. P.
Published: June 2004

Partial removal of dissolved or absorbed solvent from polymers can be accomplished during the process of screw extrusion. This paper shows how two simple transport models based either on an effective diffusivity or on an empirical mass transfer coefficient can be combined with the fluid mechanical equations which describe polymer flow during screw extrusion. In this way, the drying of solvent from a polymer during extrusion can be correlated in terms of the design and operating parameters of the extruder screw and a mass‐transfer coefficient or an effective diffusivity. This approach is illustrated employing data obtained by using two extruders of different size and two different solvent‐polymer systems. Furthermore, it is pointed out how the results can be used to predict the extent of drying during screw extrusion as well as how modifications in extruder‐screw design can permit more extensive drying of polymers during the extrusion process.
Drop formation from cylindrical jets in immiscible liquid systems
Authors: Meister Bernard J. , Scheele George F.
Published: June 2004

A theoretical analysis is presented for predicting the size of drops formed from a laminar cylindrical jet when one Newtonian liquid is injected through a nozzle into a second immiscible Newtonian liquid. The analysis couples stability theory with the requirement that the disturbances travel at the same velocity as the jet interface. Comparison of the theory with experimental data for thirteen mutually saturated liquid‐liquid systems covering a wide range of physical properties shows a mean error of 11.7% in prediction of the specific surface.
Derivation of the three‐parameter Wilson equation for the excess Gibbs energy of liquid mixtures
Authors: Renon Henri , Prausnitz J. M.
Published: June 2004

No Abstracts.
A comparison between rheological data for polymer melts and the Spriggs four‐constant viscoelastic model
Authors: Denson C. D. , Prest W. M. , O'Reilly J. M.
Published: June 2004

An experimental and analytical study was made to determine how well the material functions, derived from the Spriggs four‐constant viscoelastic model, could describe the rheological properties of polymer melts. Viscosity and elasticity of selected polymer melts were experimentally determined in the rotational and oscillatory modes using a Weissenberg Rheogoniometer. The Spriggs model was chosen for study because of its success in describing experimental data for polymer solutions and because of its uniqueness in combining results from molecular theory with results from the theories associated with continuum mechanics. It was found that the model provides a good description of the rheological data for polymer melts and that some of the model parameters depend upon the molecular characteristics of the polymer. Since this model contains a small number of well defined constants, it should be useful in developing dimensionless engineering correlations for the complex flows encountered in processes of industrial importance. Deviations between the theoretical and experimental results are discussed and deficiencies of the model noted.
The dynamic modeling, stability, and control of a continuous stirred tank chemical reactor
Authors: Ramirez W. Fred , Turner Brian A.
Published: June 2004

A realistic CSTR model was developed and verified experimentally. The reaction studied was the exothermic, base sodium hydroxide catalyzed decomposition of hydrogen peroxide. The model was used to evaluate the usefulness of the following stability analyses: steady state analysis, local linearization and Liapunov's direct method through Krasovskii's theorem. The effect of control valve hysteresis on the system was also investigated.
Concerning the calculation of residence time distribution functions for systems in which diffusion is negligible
Authors: Cokelet G. R. , Shair F. H.
Published: June 2004

No Abstracts.
Saturated‐liquid and vapor densities for polar fluids
Authors: Halm Roland L. , Stiel Leonard I.
Published: June 2004

Relationships have been developed for the saturated‐liquid density and the compressibility factor of saturated vapors by an extension of Pitzer's acentric factor approach. The fourth parameter for polar fluids defined previously by the authors in terms of the vapor pressure was utilized. For the saturated‐liquid density and the critical compressibility factor quadratic terms were necessary to accurately represent the data for a wide range of normal and polar fluids including large polar molecules. Comparisons for substances not used in the development of the relationships indicate that good results can be obtained for polar fluids by the method of this study.
Gaseous diffusion in the transition pressure range
Authors: Mistler T. E. , Correll G. R. , Mingle J. O.
Published: June 2004

Measurements of the effective self‐diffusion coefficients for carbon dioxide and methane were performed in the transition pressure range. The experiments utilized carbon‐14 tagged gases and semiconductor radiation detectors in a transient type of experiment. A detailed analysis of the errors associated with the experiments indicated that the accuracy of the measurements was near 5%. The results verify that the additive resistance law is valid for the representation in the transition range. The unknown effects of surface diffusion make the values to be employed in this law subject to review. As an example one surface diffusion model is considered.
Temperature gradients in turbulent gas streams: Investigation of the limiting value of total prandtl number
Authors: Chia Wu‐Sun , Sage B. H.
Published: June 2004

Measurements of the total viscosity and total conductivity were made as a function of position and Reynolds number for the flow of air between two parallel plates with a separation of approximately 0.7 in. The temperature of the upper plate was 130.0°F. and that of the lower plate 70.0°F. The investigations were carried out at Reynolds numbers from 40,000 to 100,000 and were in good agreement with earlier data obtained at Reynolds numbers up to 40,000. The results obtained indicate little change in the total Prandtl number with increasing Reynolds number from the value of the molecular Prandtl number.
Performance of tray columns operated in the cycling mode
Authors: Gerster J. A. , Scull H. M.
Published: June 2004

Tray efficiencies were measured for desorbing ammonia from water by air in a small sieve‐tray column operated in the cycling mode, that is, with alternate flow of vapor and liquid. The actual efficiency improvement obtained was compared with that theoretically possible assuming the liquid flows without mixing when dropped. A mixing model was proposed and the mixing parameter evaluated from the experimental data.
Two‐phase flow through porous media
Authors: Slattery John C.
Published: June 2004

In the context of a previously proposed new description for multiphase flow through porous media, we examine constitutive equations for gi, the force per unit volume which phase i exerts upon the pore walls and other adjacent fluids. The principle of material difference is used to determine the most general dependence of gi upon saturation gradient for a nonoriented (no porosity gradient) permeable structure.

Three problems are solved and the results compared with analyses based upon our interpretation of Muskat's equations. The first concerns a semi‐infinite porous column in air, the bottom of which is saturated with a liquid. The same saturation distribution is found with our approach as with Muskat's equations.

The analysis of the second problem indicates the relation between our relative permeability and that of Muskat.

The jump balances for mass and for momentum at a surface of discontinuity (or shock wave) with respect to volume averaged variables are derived. The significance of solutions in which such surfaces of discontinuity appear is discussed.

In the third problem, a plane surface of discontinuity with respect to local saturation moves through an infinite permeable structure. This is similar to the displacement of oil by an aqueous solution in a secondary recovery process. The results are comparable to those with Muskat's equations only in the limit where capillary pressure is neglected (the Buckley‐Leverett case). When capillary pressure differs from zero, Muskat's equations do not admit a shock wave solution.
Stabilizing effects of surface‐active agents on a film flow
Authors: Lin S. P.
Published: June 2004

The effects of surface‐active agents on the stability of a liquid film is reinvestigated. The present analysis differs from the previous works in the treatment of the surface boundary conditions. The well‐known damping and stabilizing effects of surface‐active agents are shown to be due to the redistribution of surface material caused by wave motions and diffusion. The equations of neutral stability for both cases of soluble and insoluble surface‐active agents are obtained.
Perturbation chromatography in chemically reactive systems
Authors: Deans H. A. , Horn F. J. M. , Klauser Gernot
Published: June 2004

A one‐dimensional column is considered in which a number of chemical reactions with arbitrary kinetics may take place among an arbitrary number of components. Initially, the column is in complete chemical and physical equilibrium. A localized small perturbation is introduced in the column at time t = 0. It is shown that, in general, this initial perturbation separates into a definite number of peaks which move with different velocities. Each peak broadens according to an asymptotic relation, depending on a characteristic dispersion coefficient. If n is the number of components, m the number of independent reactions, and σ the number of equations of state to be considered, there are n‐m‐σ peaks. These peaks do not correspond to single substances as in classical chromatography, but each peak has an eigencomposition. The velocities of the peaks are derived as functions of stoichiometry and equilibrium data. The dispersion coefficients depend, in addition, on the kinetics of the chemical reactions and on the rate of mass transfer. Thus, perturbation chromatography offers a means of determining both equilibrium and rate data. The theory is illustrated by means of two examples.
Momentum, heat, and mass transfer to a continuous cylindrical surface in axial motion
Authors: Vasudevan Ganapathy , Middleman Stanley
Published: June 2004

The transport equations for the region exterior to a cylindrical jet issuing continuously from an orifice are solved through the introduction of a similarity transform. The possibility of mass transfer normal to the jet is allowed. Of particular interest are the local transport coefficients (Cf, NNu, NSh) and their dependence on the rate of transfer from the jet.
The effect of Lewis number on the stability of a catalytic reaction
Authors: Lee James C. M. , Luss Dan
Published: June 2004

An extensive numerical study was carried out to determine the effect of Lewis number on the stability of a chemical reaction occurring inside a porous catalyst pellet. It is found that when the Lewis number is different from 1, the coupling between the concentration and temperature causes several pathological effects during the transient periods. One of the most interesting phenomenon is the occurrence of a unique unstable steady state with a periodic appearance of a very hot spot.
Predictive feedback control of a continuous flow stirred tank reactor
Authors: Huber C. I. , Kermode R. I.
Published: June 2004

A novel feedback control system, called apredictive feedback control system, is developed for the regulation of the exit composition of a continuous flow stirred tank reactor (CFSTR). The control system utilized two basic feedback signals. One is the effluent concentration of the composition to be controlled. This is measured by a batch type of composition analyzer such as a chromatograph. The other is a predictive feedback signal which continuously predicts the difference between the actual value of the controlled variable and the measurement supplied by the analyzer. The predictive signal is generated from a plant model which approximately relates the controlled variable and the continuously measured reactor temperature.

Unlike direct feedback control systems, the stability of the predictive system is unaffected by the periodic sampling and time delays introduced by the batch analyzer. Moreover, at steady state the predictive feedback signal disappears, and, like direct feedback systems, predictive feedback systems yield very accurate steady state control.

A computer simulation of the predictive feedback control of a particular CFSTR has shown that predictive control is considerably more effective in composition control than conventional direct feedback control, is more effective than conventional temperature control, and retains the advantages of direct feedback control while partially eliminating the undesirable effects caused by the batch analyzer.
The Mechanism of heat transfer in a spray column heat exchanger: II. Dense packing of drops
Authors: Letan Ruth , Kehat Ephraim
Published: June 2004

Temperature profiles of water in a spray column heat exchanger, 15 cm. in diameter and 150 cm. long, operating with a dense packing of kerosene drops, were measured. The range of superficial velocities was 0 to 0.8 cm./sec. of water and 0.5 to 1.7 cm./sec. of kerosene. The bottom of the dense packing was either slightly above or 15 cm. below the bottom of the column proper.

The physical picture of heat transfer is similar to that for dispersed packings of drops and emphasizes the dominant role of wakes in the heat transfer mechanism. The mathematical equations for dispersed packings of drops were modified to take into account the reduction of wake size at the interface of the two packings and the difference in the mixing patterns at the top of the column. An empirical allowance for the effect of bypassing is suggested. The volume of the wakes and the rate of wake shedding were estimated from the temperature profiles. General agreement was found between the theory and the experimental data of this and three other studies.
Laminar flow in the entrance region of a cylindrical tube: Part I. Newtonian fluids
Authors: Sylvester N. D. , Rosen S. L.
Published: June 2004

Pressure losses at the sharp edged entrance to a cylindrical tube were investigated for glycerine‐water solutions over a Reynolds number range of 6 to 2,000.

For the experimental area contraction ratio of 0.0156, the Hagenbach (K) and Couette (K') coefficients are 2.4 and 295, respectively. Comparison with limited previous work shows that both coefficients increase with the area contraction ratio β over range 0<β<0.162.
Effect of fluid viscosity on combined free forced convection flow phenomena in vertical pipes
Authors: Greene Howard L. , Scheele George F.
Published: June 2004

Distorted velocity and temperature profiles are measured at low Reynolds numbers for upflow constant flux heating of water and two viscous Newtonian sucrose solutions in a long vertical pipe. HeatedL/D's ranged from 29 to 251. Experimental profiles atL/D= 251 show general agreement with the fully developed profile theory based on natural convection effects, but additional profile distortion, attributed at least in part to radial viscosity variation with temperature, is observed even with water.

Natural convection induced transition to disturbed flow occurs for all three liquids as the ratio of heat input to flow rate is increased. The transition process involves the growth in amplitude and radial spread of initially small disturbances. Transition conditions and the dimensionless radial location of the first detectable instability are related to features of the distorted flow fields.
Compressibilities and virial coefficients for methane, ethylene, and their mixtures
Authors: Lee Roy C. , Edmister Wayne C.
Published: June 2004

A Burnett type of apparatus was built for 12,000 lb./sq.in. pressure and temperatures of 25° to 100°C. Isothermal expansions were run on methane, ethylene, and four binary mixtures at 25°, 50°, and 75°C., and compressibility factors were derived from the pressure ratio observations.

From the experimental data, second and third virial coefficients were derived by two techniques, that is, the slope‐intercept and the multiple regressions curve‐fit of the data by the density‐series virial equation. A comparison of these virial coefficients with those from the different empirical equations of state indicates areas of needed improvements in these equations. Second virial cross coefficients were also obtained.
Numerical simulation of convective diffusion in blood flowing in a channel with a steady, three‐dimensional velocity field
Authors: Weissman M. H. , Hung T. K.
Published: June 2004

A numerical study was performed to investigate improvement in mass transfer rates obtainable by introduction of secondary convection into a proposed membrane blood oxygenator. The three‐dimensional Navier‐Stokes equations were solved numerically for the velocity field in channel and the results used in the numerical solution for the local Po2 in the oxygenator. The convective diffusion equation solved is nonlinear, in addition to being three‐dimensional, because of the presence of red cell oxygen sinks.

The convection introduced was generated by moving one wall of the blood flow channel laterally to the main flow. Decreases in blood side film resistance up to 5 × 104 were predicted. In the presence of moderate to strong convection, the limiting factor on oxygenation rate is imposed by the membrane situated between blood and gas phases. It appears that a considerable decrease in required blood priming volume would be possible if the method discussed here were implemented.
Dynamic effects of temperature control tray location in distillation columns
Authors: Shunta J. P. , Luyben W. L.
Published: June 2004

This paper presents the results of theoretical and experimental studies of the dynamic effects of varying the location of the temperature control tray in a distillation column. The binary methanol‐water system was studied in a 24‐tray, 8‐in. I.D. column with reflux manipulated to hold the temperature on various trays in the rectifying section of the column.

The ultimate gain and ultimate frequency of the temperature feedback control loops were found to decrease as the temperature control tray was moved down the column away from the top. This confirmed the qualitative statements made by many workers and the quantitative work recently reported by Beaverstock.

The process natural frequency (or breakpoint frequency) was found, unexpectedly, to increase somewhat as the temperature control tray was moved down the column. This meant that the open‐loop response of tray liquid composition to reflux flow changes was slightly slower for trays near the top of the column. Because of the increasing purity near the top, adjacent trays differed little in composition and the slope of the equilibrium line was flatter. Both contributed to slower dynamic response.

In developing a theoretical model for the real system studied, the linear model and solution techniques of Lamb, Pigford, and Rippin and were extended to include nonequimolal overflow effects.
Transient response of a tubular reactor to upsets in flow rate
Authors: Ramaswamy Venkatasub , Stermole F. J. , McKinstry K. A.
Published: June 2004

This study concerns the transient response of a tubular reactor in which a second‐order reaction takes place under isothermal conditions. The reaction studied was the saponification of methyl acetate with sodium hydroxide. Experimental data were obtained in a tubular reactor for flow upsets.

Theoretical models using residence time distribution (RTD) techniques have been developed. The study was conducted at 36°C. The reactor was a 13‐ft. long, ¼‐in. diam. copper tube in the form of a spiral with a volume of 110 cc.

The agreement obtained between the experimental data and the RTD model predictions was good, verifying that this model is satisfactory for simulation of tubular reactor dynamics. Backmixing was observed in the reactor. This nonideality was accounted for empirically in the RTD model, since backmixing was observed to be mainly a function of flow rate.
Reaction equilibrium of real fluid mixtures
Authors: Gaggioli Richard A. , Nierode Dale E.
Published: June 2004

A theoretical approach to equilibrium calculations for homogeneous real fluid mixtures is presented. The overall approach is developed for, although not theoretically restricted to, a corresponding states equation of state, z(Tr, pr). The method is applied to the gaseous ammonia synthesis data of Larson and Dodge. Excellent agreement was attained with the data. Quite significant improvement was observed over the ideal gas and ideal solutions approximations.
A thermodynamic consistency test for adsorption from binary liquid mixtures on solids
Authors: Sircar S. , Myers A. L.
Published: June 2004

A thermodynamic consistency test for adsorption from binary liquid mixtures is derived using the Gibbs equation for adsorption. Adsorption data for the liquid mixture pairs A‐B, A‐C, and B‐C on the same adsorbent must be thermodynamically consistent. The consistency test is applied to experimental data for adsorption from the binary liquid mixtures benzene‐cyclohexane, benzene‐n‐heptane and cyclohexane‐n‐heptane on silica gel at 30°C.
A theoretical study of a controlled‐cycled stirred‐tank reactor
Authors: Codell R. B. , Engel A. J.
Published: June 2004

A mathematical study was carried out for a stirred reactor in which the feed and product streams were periodically interrupted. The cycled reactor proved superior to a continuous stirred‐tank reactor for first‐ and second‐order reactions, and surpassed a plug‐flow reactor for those cases in which the reaction rate passes through a maximum, such as autocatalytic and exothermic adiabatic reactions. Temperature‐programmed cycled reactors were also studied, but appeared to have little advantage over conventional reactors.
Simultaneous nonisothermal noncatalytic solid‐gas reactions
Authors: Wen C. Y. , Wei L. Y.
Published: June 2004

The kinetics of simultaneous, noncatalytic solid‐gas reaction systems has been analyzed in terms of the selectivity and effectiveness factor, based on the unreacted core shrinking model. The reaction systems discussed include the first‐order independent, parallel, and consecutive reactions with the simultaneous influences of heat and mass transfer. The effects of various chemical and transport properties on the stability, selectivity, and effectiveness factor of the system are discussed. The pseudosteady state approximation is employed to reduce the mathematical difficulties.
Analysis of flow choking of two‐phase, one‐component mixtures
Authors: Klingebiel W. J. , Moulton R. W.
Published: June 2004

The nature of flow choking has been studied as steam‐water mixtures are passed through a tube with ever increasing pressure gradient. Choked flow for two‐phase, one‐component mixtures has been characterized with a separated flow model as resulting from maximization of the ratio of gas to liquid velocities, or slip ratio. Slip ratios at choking were measured and found to increase from 1.2 to 5.0 at 30 lb./sq.in. exit plane pressure with decrease in quality from 0.95 to 0.02. Separated models predict either 9.3 or 28.4 with no quality dependence. The difference is attributed to liquid entrainment. Flow regimes were observed to vary from purely entrained to annular entrained to slug entrained as quality decreased. Normal shock waves were observed in the free jet at qualities above 0.25. Choking flow rates were predicted with an average error of less than 2% with a stagnation energy balance model using an empirically developed slip ratio relation corrected for entrainment.
Adaptive control of a chemical process system
Authors: Ahlgren Theodore D. , Stevens William F.
Published: June 2004

Modification of parameters in the conventional controller equation usually is necessitated by uncontrollable process parameter drifts which occur during the operation of the large scale continuous processes typically found in the chemical industry. To this end, a normalized version of the model reference adaptive control system, including suitable procedures for adjusting the adaptive loop gains, was developed and demonstrated to provide excellent adaptive performance for a single concentration control loop for a simulated stirred‐tank chemical reactor. The three constants in a conventional PID controller were simultaneously adjusted to accomplish this adaptation. Equally excellent adaptive performance was achieved in an interacting control loop scheme simulated by control of both the concentration and the temperature in the same stirred‐tank reactor. In both cases adaptation was achieved in a time interval which was sufficiently short to make this method of adaptive control feasible for use in a real processing situation. Models needed for implementation of the model reference adaptive control scheme were easily developed. In a real application these models could be easily developed from studies which could take place during prestartup or early operations of the process; hence no a priori knowledge would be required. A wide range of adaptive loop gains was demonstrated to provide a stable overall control system. A high degree of stability was demonstrated for the overall system despite the initiation of large extraneous load upsets occurring during the operation of the adaptive control system.

The method presented has not been rigorously proven to be applicable to every real control problem requiring adaptive control. However, the method was demonstrated to be highly effective over a wide range of required controller adjustments in cases similar to those encountered in large continuous processes. Thus the method merits serious consideration for possible implementation whenever adaptive control is required.
Permeation through liquid surfactant membranes
Authors: Li Norman N.
Published: June 2004

A novel separation technique based on the selectivity of a liquid membrane composed of surfactants and water is described. The permeation mechanism is discussed in terms of surfactant concentration, surfactant structure and chain length, the nature of permeate, and the solubility of permeate in water.
Heat and mass transfer in the vicinity of the triple interline of a meniscus
Authors: Wayner P. C. , Coccio C. L.
Published: June 2004

Effective experimental and theoretical techniques for studying the heat transfer characteristics of a stationary evaporating meniscus formed on a flat plate immersed in a pool of liquid were developed. Integral heat transfer data were obtained for the four systems: 304 stainless steel‐water, 6061 aluminum‐water, 304 stainless steel‐methanol, and 6061 aluminum‐methanol. High rates of heat transfer were obtained in the triple interline region with a stable meniscus. Detailed descriptions of the heat flux and temperature field were obtained for the stainless steel‐water and stainless steel‐methanol systems. The effect of the evaporation coefficient on the heat flux distribution was evaluated. The heat transfer process in the interline region proved to be more efficient than a simple conduction process in an evaporating liquid meniscus.
Backmixing in multistage agitated contactors‐‐‐a correlation
Authors: Haug H. F.
Published: June 2004

A generalized correlation is presented for the backmix ratio in multistage agitated contactors. The backmix ratio is shown to be a function of the ratio of impeller tip speed to superficial flow velocity, and of the column configuration and impeller design. For single‐phase flow and for the continuous phase in two‐phase flow, the following expression is recommended:
Calculation of dispersion coefficients by means of moments
Authors: Horn F. J. M.
Published: June 2004

The problem of evaluating the coefficient of dispersion in a general linear two‐component chromatographic system is equivalent to a steady state source problem in multidimensional Euclidean space. The equivalence of the two physical problems provides an intuitive insight into the contributions of different transport processes to dispersion. For a wide class of systems the dispersion coefficient can be expressed as the maximum of a functional. This can be utilized in the numerical evaluation of dispersion coefficients and in the application of perturbation techniques.
The calculation of unsteady state multicomponent distillation using partial differential equations
Authors: Osborne Adam
Published: June 2004

A method is presented for calculating unsteady state multicomponent distillation using partial differential equations. The equations are solved by treating them as continuous in theoretical stage direction and stepped in time. Although some restrictions were placed on the problems actually solved, the method itself is not restricted by number of trays, number of components, number, type or combination of upsets, or by the thermodynamics of the system, and the method readily lends itself to hybrid computer solution.
Control of distillation columns with sharp temperature profiles
Authors: Luyben W. L.
Published: June 2004

Temperature control problems are frequently encountered in distillation columns that, as a result of high purity products and an easy separation, have large temperature changes over a few trays. The describing function technique is used in this paper to analyze the stability of this type of column in which a nonlinear feedback control loop for column temperature control manipulates vapor boilup.

The cycling usually experienced in these systems is shown to be unavoidable in many cases because the process transfer function has such a high gain that it acts like an on‐off switch. The process also displays nonlinear dynamics: system time constants vary with the magnitude of change in vapor boilup.

To overcome these difficulties an adaptive, nonlinear feedback controller is proposed that keeps the loop in a small‐amplitude limit cycle by adaptively changing controller gain. The system is evaluated by digital simulation of a nonlinear model of the column.
Kinetics of noncatalytic, nonisothermal, gas‐solid reactions: Hydrofluorination of uranium dioxide
Authors: Costa Eduardo C. , Smith J. M.
Published: June 2004

A single‐pellet, stirred‐tank reactor was used to measure temperatures, compositions, and rates of reaction for the hydrofluorination of UO2.14 at atmospheric pressure. By correlating the rate with conditions at the reacting surface, the activation energy of the first‐order reaction was found to be 6,070 cal./g.‐mole.

Since the product forms an unreactive layer around the core of UO2.14, and since the heat of reaction is high, significant concentration and temperature differences develop between the gas phase and the reaction surface. The temperature and rate data were used to calculate the effective diffusivity and thermal conductivity of the product layer under reaction conditions.

An adaptation of a pseudosteady state method was developed for predicting the conversion and temperature history of a pellet. Using rate constants for reaction and mass and energy transfer derived from the experimental data, this method gave good results. Predictions with estimated rate constants were poor, indicating that an accurate value was necessary for the effective diffusivity in the product layer.
Slow flow of a non‐newtonian fluid past a droplet
Authors: Wagner Martin G. , Slattery John C.
Published: June 2004

The problem of slow flow past a droplet is considered where both materials may be represented as fluids of grade 3 and where the outer fluid is of infinite extent. Both non‐Newtonian and inertial effects are included in the analysis. A double perturbation technique and the method of matched asymptotic expansions are employed to obtain solutions to the equation of motion.

Solutions, in the form of Legendre polynomial series, are obtained for the stream function (both outside and inside the droplet), for the drag force exerted on the droplet, and for the shape of the droplet.

The results obtained are in complete agreement with those obtained by other workers for the flow of a Newtonian fluid past a Newtonian droplet and for the flow of a fluid of grade 3 past a solid sphere. Droplet shape predictions are in qualitative agreement with experimentally observed shapes.
Computerized catalytic kinetics: A useful extension of the method of Wei and Prater
Authors: Lombardo E. A. , Hall W. Keith
Published: June 2004

An extension of the method of Wei and Prater has been devised for determining the relative rate constants for an isothermal, first‐order, reversible, three‐component system, namely, the catalyzed isothermal isomerization of n‐butenes. The new method reduces the required work to one experiment.
Heat, Mass, and momentum transfer analogies for the fully developed turbulent flow of power law fluids in circular tubes
Authors: Krantz W. B. , Wasan D. T.
Published: June 2004

A new correlation is presented to describe heat and mass transfer at large Prandtl or Schmidt numbers to power law fluids in fully developed turbulent flow in a pipe. The resulting expression for the Stanton number differs from earlier semiempirical correlations in that it is based on a continuous eddy viscosity distribution from the wall to the center of the pipe and contains no adjustable parameters to be determined from heat transfer data. Nusselt numbers determined by the new correlation are in excellent agreement with data on heat transfer to both pseudoplastic and dilatant fluids.
Enzyme kinetics and engineering
Authors: Carbonell R. G. , Kostin M. D.
Published: June 2004

This review article surveys representative literature on enzyme kinetics and engineering published form January 1969 to August 1971. Particlar attention is given to methods of attaching enzymes to solid supports, and to factors, such as pH and temperature, which affect the reaction rate. Recent theories accounting for the high selectivity and high rate of enzyme reactions, calculations taking into consideration the effects of diffusion, methods for analysing kinitic data, and proposals for enzyme reactors are evaluated. Also reviewed are recent methods for extraction of enzymes from cells, procedures for synthesizing enzymes artificailly, and techniques for isolating and purifying enzymes.