bluuebunny/crossref_metadata_2025 huggingface dataset:
Momentum, heat, and mass transfer for fixed and homogeneous fluidized beds
Authors: Hughmark G. A.
Published: June 2004

The Carman channel model for flow in packed beds is shown to apply for the minimum fluidization velocity and homogeneous fluidized beds. The channel model also provides correlations for mass transfer in the laminar flow region and heat and mass transfer for turbulent flow in a packed bed. Tube bundle data for pressure drop and heat transfer are also evaluated as a packed bed with the channel model.
The shape of a fluid drop trapped between two horizontal surfaces
Authors: Wood S. M. , Hartland S.
Published: June 2004

In a close packed dispersion, a drop experiences forces from the surrounding drops which affect its shape and rate of coalescence. The geometry is complicated, but a simple model which may help clarify the phenomenon is that of a drop trapped between two horizontal surfaces under the action of an applied force.

The differential equations governing the shape of the surface of such a drop have been solved numerically and the predicted drop dimensions checked experimentally by applying known forces to a drop and recording the shape photographically.
Damping coefficient design charts for sampled‐data control of processes with deadtime
Authors: Luyben W. L.
Published: June 2004

Design charts that give the value of the gain of a proportional sampleddata controller for various closed loop damping coefficient specifications are presented. Charts for first‐ and second‐order processes with various deadtimes are given over a range of sampling rates.

Typical root locus plots in the z plane are also presented to illustrate how increasing deadtime (as an integer multiple of the sampling period) increases the order of the system in the z domain.
Resource recovery: A new field for technology application
Authors: Abert J. G. , Zusman Morris J.
Published: June 2004

This review paper surveys the state‐of‐the‐art of resource recovery from municipal, primarily residential, refuse. Unfortunately, progress in effecting the actual installation of full‐sized recovery facilities has been minimal. The work that has been done has been beset with technical, and more often, economic difficulties. However, the rising cost of traditional means of disposal may allow new systems to become economically competitive. Past research development efforts hold out promise of success and the nation may see the application of efficient technological solutions that in some localities will actually reduce the cost of refuse disposal below that of traditional means.
The utilization of expert opinion in decision‐making
Authors: Klee Albert J.
Published: June 2004

This is a review of the state‐of‐the‐art of rational and primarily quantitative approaches to the utilization of expert opinion in the inexact sciences, among which the engineering sciences must be included. Of primary concern is the decision‐maker's utilization of one or more experts, and the criteria and scoring rules used to evaluate their performance. Also reviewed are certain game‐theoretic strategies used by experts to maximize their own goal satisfaction. With this review, it is hoped that chemical engineers, when acting as decision‐makers, will be able to utilize expert opinion more effectively and will better understand the function of experts when it is necessary for them to adopt such roles themselves.
Modal analysis of convection with axial diffusion
Authors: Cohen William C. , Loeb Alfred M. , Weston Kenneth
Published: June 2004

The one‐dimensional model for convection with diffusion and with a source term for mass or energy generation or interchange is analyzed for the eigenvalues and the corresponding spatial eigenmodes as a function of the Peclet number. It is shown how the modal analysis of the source case, when the source coefficients for heat exchange and chemical reaction are spatially independent, is directly related to the no source solution. Numerical examples of determining the source term coefficient are included. These solutions form a base to discuss dynamic characteristics and stability and to which solutions for spatially dependent coefficients can be compared.
The optimal control of a periodic adsorber: Part I. Experiment
Authors: Kowler Daniel E. , Kadlec Robert H.
Published: June 2004

Cyclic pressure variations in a fixed bed adsorber can cause significant separation of gaseous mixtures. Feed pressure changes are the driving force in this parametric pumping process. The optimal feed sequence is maximum (maximum flow in) pressure, zero flow (variable pressure), maximum flow out (minimum pressure). For the nitrogen‐methane feed gas at 168 k N/m2 and a 1.22 m bed of adsorbent, the optimal cycle time is 3 seconds, and feed is sustained 50% of the time. The zero flow mode is unnecessary if product purity is the sole objective.
The optimal control of a periodic adsorber: Part II. Theory
Authors: Kowler Daniel E. , Kadlec Robert H.
Published: June 2004

The fixed bed binary gas adsorber, when alternately fed and exhausted at one end, produces a purified product from the other end. Coupled partial differential equations in pressure and composition, representing total mass and component balances with local equilibrium, describe the operation. The Maximum Principle is applied to determine the optimal cyclic unsteady feed policy for the balanced objectives of product purity and quantity. The sequence (maximum feed, no flow, maximum exhaust) is optimal. The experimental optimum is close to the calculated optimum. Dimensional analysis is used to determine parametric effects.
Calculation method for the response time to step inputs for approximate dynamic models of distillation columns
Authors: Weigand W. A. , Jhawar A. K. , Williams T. J.
Published: June 2004

A calculation method to determine the response time to be used for approximate mathematical models is developed for the dynamic behavior of distillation columns. Previous work has shown that the concept of Inventory time can be successfully used to approximate the response time, that is, the 60% point of the step response, of distillation columns operating at a high degree of separation. A modified version of the inventory time method, based on the minimum change of storage, has been developed to predict the response time for other ranges of separation within reasonable bounds of error, ± 10%. Only steady state and design data were used. A rigorous nonlinear simulation generates the steady state and transient data upon which the approximate models are based.

While the modified inventory time method developed cannot handle every possible operating condition with the desired degree of accuracy, it has been shown to apply over a much wider range of operating conditions than the original inventory time method.
Determination of friction factors for pulsatile flow of water in distensible tubes
Authors: Ahn John S. , Hershey Daniel
Published: June 2004

Theoretical models for computing velocity profiles and friction factors for sinusoidally pulsing laminar flow in linearly elastic tubes were derived from the Navier‐Stokes equations, a modified Fanning equation, and the pressure‐tube wall movement relationship. The theoretical results were checked experimentally for NRe and λ = ωR2/v values up to 2000 and 57, respectively. It was found that the theoretical friction factors predicted the experimental values to within less than 13%. Also the results showed that the energy losses in elastic tubes were greater than in rigid tubes.
Separation in a thermoelectrogravitational electrophoresis column without reservoirs: Part I. Theoretical development of the transport equation and its application to the analysis of steady state batch operation
Authors: Crosser O. K. , Powers J. E. , Prabhudesai R. K.
Published: June 2004

The thermoelectrogravitational electrophoresis column without reservoirs has been conceived following the principle of the Clusius‐Dickel thermal diffusion column. The transport equation approach in thermal diffusion developed by Jones and Furry to explain the behavior of a conventional thermogravitational thermal diffusion column has been applied to describe the electrophoretic separation in the thermoelectrogravitational electrophoresis column. Equations have been established for a system in which one single or one hypothetically single component is mobile and the other species are at their isoelectric points.

Theoretical calculations for the velocity profiles, temperature distribution, and the steady state batch separation factors have been made with field strength, temperature difference, membrane spacing, and electric mobility as variables, and expected trends of the results are discussed using the steady state solution of the transport equation for batch operation.
Theoretical recoveries in filter cake reslurrying and washing
Authors: Tomiak A.
Published: June 2004

Theoretical equations and graphs are presented for filter cake reslurrying and washing with linear solute sorption.

In the case of washing, the filter cake was represented by a model consisting of a number of mixing cells in series. Due to the complexity of the model, explicit algebraic solutions could not be obtained for countercurrent washing, but numerical data were generated using a computer.

Practical application of the above is outlined.
Fully developed viscous flow in coiled circular pipes
Authors: Austin Larry R. , Seader J. D.
Published: June 2004

The Navier‐Stokes equations in stream‐function/vorticity form were solved numerically by over‐relaxation for the case of steady state, fully developed, isothermal, incompressible viscous Newtonian flow within a rigorously treated toroidal geometry. Solutions were obtained for curvature ratios ranging from 5 to 100 and for Dean numbers as low as I and as high as 1000. The Dean number was demonstrated to be the principal parameter to characterize toroidal flow; however, a second‐order dependence upon the curvature ratio above that expressed in the Dean number was observed. Comparisons of the numerically computed axial‐velocity profiles were made with experimental data. The cross‐sectional pressure distribution was calculated, and a correlation is presented for a diametral pressure drop in terms of the Dean number.
Effect of mixing on nonuniformly initiated polymerization by radiation
Authors: Kawakami Waichiro , Machi Sueo
Published: June 2004

An analytical study was carried out on the effects of mixing on radiation‐induced polymerization in which the species initiating the polymerization were not uniformly produced because of a nonuniform dose rate distribution. The analysis is based on the periodic irradiation of fluid elements circulating in a stirred‐tank reactor having a high dose rate region and a very low dose rate region. It is shown that the rate of polymerization increases with agitation speed and that the bimodal molecular weight distribution of the polymer formed at low agitation speed moves to a unimodal distribution as the agitation speed increases.
A new method of parameter estimation in linear systems
Authors: Gavalas George R.
Published: June 2004

A time domain method is given for estimating the matrix of related parameters in linear systems with constant coefficients and real eigenvalues. The method consists of a one‐dimensional search for the local minima of a scalar function μ(λ), which provide the eigenvalues of the system matrix and the matrix itself when observable. Applications are given to the determination of a transfer function and the estimation of the rate matrix of a monomolecular reaction system. Questions of accuracy, number, and type of measurements required are discussed.
Vapor‐liquid equilibrium: Part II. Correlations from P‐x data for 15 systems
Authors: Byer Stanley M. , Gibbs Richard E. , Van Ness Hendrick C.
Published: June 2004

Pressure versus composition data for 15 binary systems in vapor‐liquid equilibrium at 30°C form the basis for correlation of the excess Gibbs function and the activity coefficients for these systems.
A feasible‐point algorithm for structured design systems in chemical engineering
Authors: Debrosse Charles J. , Westerberg Arthur W.
Published: June 2004

Structured design systems are systems in which the equations representing the equality and inequality constraints are sparse and highly precedenc orderable. An algorithm has been developed for such systems which is guaranteed, under certain assumptions, to arrive in a finite number of steps at a feasible point (that is, one which satisfies all the constraints) or to identify a subset of the constraints for which no feasible point can be found. The algorithm can be applied to a system with only inequality constraints or to a system with both equality and inequality constraints.

The algorithm uses an indirect approach. It hypothesizes that a subset of constraints has no feasible region and then attempts to verify this conjecture. If successful, the subset is identified as infeasible and obviously no feasible point exists. If unsuccessful, either a new hypothesis can be generated or the algorithm has indirectly found a feasible point.

Limited computational experience with the algorithm indicates that the number of steps required to find a feasible point for a system of constraints has been of the same order of magnitude as the total number of constraints in the system. For linear constraints, the efficiency of the algorithm has been comparable to phase one of the Simplex algorithm of Linear Programming.
An improved generalized equation of state
Authors: Yamada Tomoyoshi
Published: June 2004

Two forms of a generalized Benedict‐Webb‐Rubin Equation, BWR24 and BWR44, are proposed for dense gases which represent an improvement by a factor of about three in calculated pressures compared to reduced forms of this relationship in the literature. The method is also tested for accuracy in predicting enthalpy departures for pure components and mixtures. The proposed methods are marginally better than the best of other methods tested. Major advantages for the proposed equations are their relative simplicity, low computer storage requirements, and generality. No mixture interaction constants are required other than those already available in the literature.
A linear model for predicting the washout of pollutant gases from industrial plumes
Authors: Hales Jeremy M. , Wolf Marvin A. , Dana M. Terry
Published: June 2004

A simplified method for predicting the washout of gaseous constituents from industrial plumes has been developed. This method is a linearized version of a more general treatment given previously. It is based upon an application of conventional mass‐transfer theory in conjunction with existing plume dispersion models and accounts for reversibility of the adsorption process and liquid‐phase mass‐transfer resistance. The method presented in this paper is sufficiently simple to permit hand calculation, if necessary.

This model is recommended for calculation of washout of gases from plumes under conditions where the gas exhibits physical or pseudophysical adsorption behavior. It is expected to apply with reasonable accuracy for gases with linear solubility relationships; accuracy for situations involving other gases is expected to be less satisfactory, depending upon the degree of deviation from this idealized behavior.
Liquid‐Liquid contacting in unbaffled, agitated vessels
Authors: Weinstein Bruce , Treybal Robert E.
Published: June 2004

Drop size and dispersed‐phase holdup were measured for liquid dispersions in covered, unbaffled agitated vessels with no gas‐liquid interface and hence no vortex for batch and continous flow. Vessel diameters of 0.245 and 0.372 m, turbine impellers of diameters 0.0762 and 0.127 m in two locations, four organic‐ and three water‐dispersed systems of a wide range of properties, and a wide range of operating conditions were studied. The data for average drop diameter and dispersed‐phase holdup, from which specific interfacial area may be computed, were successfully correlated through modification of the theories of maximum drop size in an isotropically turbulent fluid.
Approximation in control of nonlinear dynamic systems
Authors: Tsang A. C. C. , Luus Rein
Published: June 2004

The type of system approximation in which the system state space x is mapped into a scalar domain V by a quadratic transformation

where Q is appropriately determined, is used to develop a suboptimal control procedure for unconstrained lumped parameter dynamic systems via the application of Pontryagin's Maximum Principle. The optimization problem in the scalar domain becomes an initial value problem when the scalar adjoint variable is held constant through out the course of control. The resulting computational scheme includes an effective and simple way to construct the transformation matrix Q and a straightforward minimum seeking approach to locate the best constant overall average scalar adjoint parameter. For the class of problems with quadratic performance index, system equation approximation further reduces the determination of Q to the solution of a matrix Riccati equation.

The application of the proposed suboptimal control procedure to four chemical engineering systems shows that the procedure is simple direct, and efficient and works particularly well for problems where the final time is large.
Kinetics of crystallite sintering during heat treatment of supported metal catalysts
Authors: Ruckenstein E. , Pulvermacher B.
Published: June 2004

Models are developed to describe sintering of metal crystallites during heat treatment. The growth rate of such crystallites is assumed to depend upon particle migration over the surface of the support as well as on the rate the colliding particles merge (sinter) into a single unit. The theory predicts that the rate of decay of exposed metal surface area S is given as in Equation (1a). The exponent n is related to the assumed size dependence of the diffusion coefficients or of the rate constant of the merging process. It varies from 4 to 8 for diffusion controlled decay and it is less than 3 for sintering controlled decay, that is, when the rate controlling step is the merging of two colliding particles. Diffusion control is associated with strong interactions between the metal and the support, but in sintering control there is a weaker metal‐support interaction.
Observer theory for lumping analysis of monomolecular reaction systems
Authors: Liu Y. A. , Lapidus L.
Published: June 2004

A new approach for the lumping analysis of reversible and/or irreversible monomolecular reaction systems (MRS) with constant or time‐dependent rate coefficients in discrete and continuous mixtures is presented. The observer theory initiated by Luenberger is proposed and extended to obtain the necessary and sufficient conditions of exact and approximate lumping of such systems. Examples are given to illustrate the implications of lumping and to demonstrate the generality and promising aspects of the observer approach. It is shown that this theory is a unifying method for the lumping analysis of MRS. New insights on lumping analysis are discussed.
Computation of three‐dimensional viscous flow between convergent traveling surfaces
Authors: Hazbun Eddy A. , Churchill Stuart W.
Published: June 2004

The Marker‐and‐Cell numerical technique has been adapted to develop a method of solution for three‐dimensional, unconfined, isothermal flow of a highly viscous, Newtonian fluid in a region bounded by two, nonparallel traveling surfaces. Results are reported only for plane and elliptical surfaces, but the analysis is general enough to handle any shape of interest.

A computer program was developed which can be used to generate and plot the flow and pressure fields. Numerical results were obtained for the special case of symmetrically opposed convergent surfaces for a wide range of conditions.
Impurity effects in continuous‐flow mixed suspension crystallizers
Authors: Liu Yih‐An , Botsaris Gregory D.
Published: June 2004

The crystallization of NaCl in the presence of Pb+ + as an Impurity in a continuous, mixed suspension, mixed product removal (CMSMPR) crystallizer was investigated. The results indicated that nucleation and growth rates as well as the dominant crystal sizes can be correlated by simple power functions of impurity concentration. The exponents are constants independent of the impurity concentration, thus permitting the prediction of nucleation rates, growth rates and size distributions at various concentrations of that impurity. This model was shown to apply also to other crystallizing systems.
On filtering in delay systems with continuous dynamics and discrete‐time observations
Authors: Padmanabhan L.
Published: June 2004

Filter equations for linear delay systems with continuous‐time dynamics and discrete‐time measurements are derived by separating the estimation problem into prediction between measurements and updating at a measurement. The result is the analog of the well‐known Kalman filter for the nondelay case. A computational technique for implementing the filter is indicated and illustrated by an example of a scalar system with a delay in the dynamics as well as measurement.
Determination of liquid‐mixture solubility parameters and interaction energy densities
Authors: Lui Peter C. K. , Donnelly Harold G.
Published: June 2004

Integral, isothermal heat‐of‐condensation values for continuously generated vapors of various constant‐composition mixtures, along with the isothermal densities of the condensates, enable the calculation of the cohesive energy densities of solutions. Data for the complete range of composition of the chloroform‐acetone system and for a major portion of the chloroformdiethyl ether system at 35°C are reported. From these data, the specificinteraction‐energy density for each system is calculated, based upon an extension of the Scatchard‐Hildebrand Regular Solution Theory.

The essential equality of the specific‐interaction energy‐density values for the two systems indicates a preponderance of the same kind of hydrogen bonding (CH‐‐‐O) in each.
Enhancement of stagnation flow heat and mass transfer through interactions of free stream turbulence
Authors: Galloway T. R.
Published: June 2004

At the forward stagnation point of a bluff body the laminar flow is influenced by externally generated free‐stream turbulence, such as from grids, in such a way that heat and mass transport are significantly enhanced above their normal values. The basis of this enhancement is an unsteady, threedimensional flow pattern formed at the forward stagnation point and triggered or altered by the free‐stream turbulence. Such complex flows can be interpreted as roll cells oriented with their axes parallel to streamwise coordinates. Such roll cells have been observed by other investigators using special experimental visualization techniques. This complex flow was introduced into the momentum and transport equations, which were then solved numerically to produce the relationships between Nusselt, Reynolds, and Prandtl numbers and free‐stream turbulence. Not only were these relationships nearly identical with earlier established empirical correlations, but they revealed in addition a strong augmentation for high Prandtl number flows. Predictions in slurry flows around bluff bodies were also found to be reasonable.
Restricted diffusion in liquids within fine pores
Authors: Satterfield Charles N. , Colton Clark K. , Pitcher Wayne H.
Published: June 2004

The effect on the liquid‐phase effective diffusivity in fine pores of the ratio of solute molecular diameter to pore diameter and of preferential solute adsorption was studied by measurements on homogeneous silicaalumina bead catalyst (pore diameter = 3.2 nm). A proposed empirical correlation is based on the investigation of a variety of binary systems of paraffins and aromatic hydrocarbons and of aqueous solutions of sugars.
Adsorption and molecular association in the Burnett apparatus
Authors: Eubank Philip T. , Kerns William J.
Published: June 2004

Physical adsorption errors accumulate in the isothermal Burnett PvT apparatus. The equations describing this sequential phenomena plus diagnostic methods and correction procedures are given. Shift of the apparent volume ratio, the prinicipal indication of significant adsorption, is related to the difference between the surface and volume ratios. The effect of adsorption on the usual Burnett graphs follows from real and simulated data examples. Isochoric coupling as related to the adsorption problem is fully reviewed.

Experiences with chemisorption are related and explained for the first time. Molecular association, which is properly measured by the Burnett apparatus, is compared to adsorption where the two phenomena coexist.
Wake phenomena in a liquid‐liquid fluidized bed
Authors: Yeheskel Jacob , Kehat Ephraim
Published: June 2004

Measurements of the size and rate of shedding of wakes of drops, average drop holdup and velocity of the continuous phase as functions of drop size for kerosene, hexane, and benzene dispersed in water in a liquid‐liquid fluidized bed are reported. The average drop size ranged between 3.3 and 4.8 mm. The water velocity was 5.0 to 12.05 cm/s. The average drop hold up was 0.065 to 0.560.

The ratio of wake to drop volume was 0.2 to 2.4, and the rate of wake shedding, reported as time of wake transfer units, was 0.7 to 2.4. At low drop holdups, the effect of single drops and groups of drops is dominant. At high drop holdups, the effect of neighboring drops and wakes is dominant. The wake size is correlated with slip velocity and can be calculated from empirical holdup measurements.
Selective membrane transport
Authors: Reusch C. F. , Cussler E. L.
Published: June 2004

Cyclic Polyethers acting as mobile carriers in facilitated transport can cause changes of as much as three orders of magnitude in the fluxes of various cations across liquid membranes. The cyclic polyether dibenzo‐18‐crown‐6 (2,3,11,12‐dibenzo‐1,4,7,10,13,16‐hexaoxacyclooctadeca‐2,11‐diene) was used in this work to achieve such a large selectivity. The results show that a primary factor leading to the selectivity is the ratio of unsolvated cation radius to polyether central ring radius. The implication is that by selecting a polyether with a desired central ring radius, any two cations of slightly different radius can be separated efficiently.
Simultaneous heat and mass transfer from multicomponent condensing vapor‐gas systems
Authors: Schrodt J. Thomas
Published: June 2004

Multicomponent vapor condensation in the presence of noncondensing gas has been analyzed using numerical solutions to a set of linearized rate equations that describe the simultaneous heat and mass transfer to the condensate film. For specific examples of methanol and water and ethanol and toluene condensing from turbulent air streams in vertical tube and on horizontal tube condensers, it is shown that the alcohol concentrations in both the liquid and gas phases increase as condensation from initially superheated, alcohol‐rich gas phases progresses; the liquid phases also become richer in alcohol. The mass fluxes of the vapors vary with their respective mass transfer coefficients and local concentration driving forces. In the vertical tube condensers, the flux of the alcohols go through maximums. Gas phase saturation is approached as the mixtures cool and the final traces of vapor become more difficult to condense. Interface properties are computed from limited VL equilibrium data, heat of solution data, and a predictive equation. The techniques of solution and analysis have general application to the design of cooler‐condensers in either vertical or horizontal configurations.
Optimization by direct search and systematic reduction of the size of search region
Authors: Luus Rein , Jaakola T. H. I.
Published: June 2004

A direct search procedure utilizing pseudo random numbers over a region is presented to solve nonlinear programming problems. After each iteration the size of the region is reduced so that the optimum can be found as accurately as desired. The ease of programming, the speed of convergence, and the reliability of results make the procedure very attractive for solving nonlinear programming problems.
Momentum transfer through packed beds of various particles in the turbulent flow regime
Authors: Gauvin William H. , Katta Satyanarayana
Published: June 2004

The flow of air through packed beds of solid and hollow particles of a wide range of geometries was studied, with particular reference to the effect of the particle shape on the pressure drop in the turvbulent range. A method of analysis based on the concept of stagnant void fraction and the principle of drag additivity has been developed. Equations for estimating the stagnant voidages for various particle shapes arranged in a random pattern in a packed bed were derived. A new type of friction factor based on this approach was correlated satisfactorily with a shape factor. The momentum transfer data were also correlated with the sphericity of the particles.
Activity coefficients–aqueous solutions of polybasic acids and their salts
Authors: Meissner Herman P. , Peppas Nikolaos A.
Published: June 2004

A method of predicting activity coefficients of polybasic acids and their salts in strong aqueous solutions is presented. Application of the calculation of decomposition pressures of SO2 over sodium sulfite‐bisulfite systems and of CO2 over carbonate‐bicarbonate systems is illustrated.
Interfacial areas of liquid‐liquid dispersions from light transmission measurements
Authors: McLaughlin C. M. , Rushton J. H.
Published: June 2004

A mathematical model simulating light transmission through liquid‐liquid dispersions has been developed. Numerical solutions of the model for various drop size distributions show that the fraction of parallel light which passes through a dispersion is a unique function of a dimensionless group, here named the Transmission Number, regardless of the drop size distribution. The results, which were verified by actual light transmission experiments, show that the interfacial area of a liquid‐liquid dispersion can be calculated from a light reading provided that the light detector receives only parallel light. Application of the results to other two‐phase dispersions is indicated.
An experimental evaluation of Kalman filtering
Authors: Hamilton James C. , Seborg Dale E. , Fisher D. Grant
Published: June 2004

The effectiveness of the stationary form of the discrete Kalman filter for state estimation in noisy process systems was demonstrated by simulated and experimental tests on a pilot plant evaporator. The filter was incorporated into a multivariable, computer control system and resulted in good control despite process and/or measurement noise levels of 10%. The results were significantly better than those obtained when the Kalman filter was omitted or replaced by conventional exponential filters. In this application the standard Kalman filter was reasonably insensitive to incorrect estimates of initial conditions or noise statistics and to errors in model parameters. The filter estimates were sensitive to unmeasured process disturbances. However this sensitivity could be reduced by treating the noise covariance matrices R and Q as design parameters rather than noise statistics and selecting values which result in increased weighting of the process measurements relative to the calculated model states.
An experimental study of the control of condensate subcooling in a vertical condenser
Authors: Archambault Jean‐Paul , Jauffret Jean‐Paul , Luyben William L.
Published: June 2004

Temperature control of subcooled reflux in a distillation column was studied experimentally using coolant flow rate as the manipulative variable. Methanol vapor was condensed and subcooled at one atmosphere in a vertical heat exchanger with 210 copper tubes (0.77 cm I.D., 91.5 cm long). Cooling water flowed countercurrently through the shell side (20.6 cm I.D.).

A proportional‐integral feedback controller provided good temperature control at normal design throughputs. But dynamic control performance deteriorated at low throughputs (or large areas). Thus the normal conservative design practice of providing excess area in this type of condenser leads to poorer temperature control.
Radiation fields inside an elliptical photoreflector with a source of finite spatial dimensions
Authors: Cerd́a Jaime , Irazoqui Horacio A. , Cassano Alberto E.
Published: June 2004

Using the Extense Source Formulation (Irazoqui et al., 1973a), a radiation distribution model for the tubular lamp‐elliptical reflector system was developed for predicting energy density profiles inside the elliptical cavity of the system.

It introduces a significant improvement over the linear‐lamp models since it avoids any form of singularities in the prediction of radiation energy density profiles at the focal points of the elliptical reflector. Also, all lamp and reflector dimensions are parameters of the model.

Calculated results agree well with published experimental data for a similar lamp reflector set up.

One of the most important conclusions is the absence of uniform irradiation from all radial directions at the reactor location.
Bubble‐free expansion of gas‐fluidized beds of fine particles
Authors: Donsì G. , Massimilla L.
Published: June 2004

Five different fine powders with average particle size of about 100 microns or smaller were fluidized with air over their respective bubblefree ranges of fluidization. Photographs taken through the front transparent wall of the column showed that the beds contained cavities and microchannels whose sizes were of the same order of magnitude as the particle size. It is shown that interparticle van der Waals adn capillary forces play an important role in the bubble‐free expansion of small particles. Measurements of bed expansion and average particle drag coefficients are consistent with the proposed role of interparticle forces.
Independent reactions in the presence of isomers
Authors: Whitwell J. C. , Dartt S. R.
Published: June 2004

In reacting systems, the number of independent chemical reactions, the number of components, and the number of chemical chemical species are generally assumed to be so related that the sum of the first two equals the third. Standard methods of obtaining the number of independent reactions (that is, formation equations or rank of the element‐by‐species matrix) may fail when chemical isomers appear in reactant streams, product streams, or both. The errors encountered with various types of isomers are delineated in this paper along with corrective measures. The element‐by‐species matrix is judged to be more suitable as a starting point than formation equations when matrix size and number of manipulations are considered.
Topics in computer‐aided design: Part I. An optimum tearing algorithm for recycle systems
Authors: Pho T. K. , Lapidus L.
Published: June 2004

The concepts of ineligible streams and two‐way edge reduction are extended to simplify the signal flow diagram of a recycle process flow sheet graph. The solution to a tearing problem can be obtained readily by repeated reduction of ineligible streams and two‐way edges. When this fails, a branch and bound method will guarantee optimality at the expense of a few enumerations.
Compressibility factor of polar fluids in the gaseous and liquid regions
Authors: Stipp Gordon K. , Bai S. D. , Stiel Leonard I.
Published: June 2004

The tables of Pitzer et al. for the compressibility factor of nonpolar substances have been extended to polar fluids for the gaseous and liquid regions for reduced temperatures from 0.8 to 1.15 and reduced pressures from 0.2 to 6.0. Available experimental PVT data for polar fluids were related to the acentric factor and fourth parameter at constant reduced temperature and pressure by a quadratic least squares procedure. The resulting relationships reproduced the data utilized with good accuracy for the entire region considered.
Analytical formulas for disk filters
Authors: Tiller Frank M. , Risbud Hemant
Published: June 2004

Formulas relating the rate of filtrate flow in a sectioned disk filter to the process variables are derived. It is demonstrated that an optimum inner radius which yields a maximum flow of filtrate can be chosen. Flow rates for drum and disk filters operating under similar conditions are compared.
Collision breeding: A function of crystal moments and degree of mixing
Authors: Desai R. M. , Rachow J. W. , Timm D. C.
Published: June 2004

An experimental procedure based on continuous crystal seeding was developed which can explicitly determine the fundamental relationship between collision breeding and the leading moments of the crystal size distribution. For the aqueous, cooling crystallization of potassium dichromate, the analysis determined that only the mass moment was successful in correlating observations subject to crystal seeding.

It was also observed that mixing may have a pronounced effect on the nucleation rate but that kinetic orders for collision breeding and growth rate were independent of mixing.
Influence of mixing on the performance of periodic chemical reactors
Authors: Lee C. K. , Bailey J. E.
Published: June 2004

The interaction between imperfect mixing and cyclic operation is examined for several continuous polymerizations in stirred‐tank reactors. The reactor is represented by a mixed model involving two interconnected ideal stirred vessels. Cyclic fluctuations in the concentration of a chain transfer agent during Ziegler‐catalyzed olefin polymerization can yield molecular weight distributions significantly different from those of a conventional steady state reactor. This result is consistent with the available experimental data. It is especially interesting that the cyclic reactor effluent with a modified molecular weight distribution is of approximately time‐invariant composition when the period of cycling is on the order of the reactor holding time. Imperfect mixing has a lesser effect on cycled reactors for free‐radical and polycondensation polymerization than it has on cycled olefin polymerization reactors.
Analysis of fixed bed sorption: Flue gas desulfurization
Authors: Bourgeois Sidney V. , Groves Frank R. , Wehe Albert H.
Published: June 2004

Temperature and concentration profiles are obtained by solution of the coupled nonlinear differential equations which describe transient operation of an adiabatic fixed bed reactor. The unreacted‐shrinking core mechanism describes the multiple, irreversible, exothermic gas‐solid reactions. Numerical integration is accomplished by a predictor‐corrector scheme which is programmed in Fortran IV language. The influence of kinetic parameters, heat and mass diffusivities within pellets, temperature variation of properties, gas velocity, bed and particle dimensions, inlet gas temperature and composition, and initial bed temperature on reactor performance are studied for sulfur dioxide removal from flue gases by fixed beds of copper oxide. Comparison with commercial reactors is in qualitative agreement.
Generalized f/P, ZT and ZP values for liquids at low reduced temperatures
Authors: Hsi Chu , Lu Benjamin C.‐Y.
Published: June 2004

The three‐parameter correlation of Pitzer et al. for fugacity coefficients (f/P) has been extended to liquids in the 0.5 ≤ Tr ≤ 0.8 and 0.2 ≤ Pr ≤ 9.0 region. In addition, values of the derivative compressibility factors ZT and ZP have also been obtained in the same region. This extension is based on the generalized correlation of the compressibility factor Z recently reported. The isothermal coefficient of bulk compressibility βT compiled by Rowlinson has been employed with the pressure effect on βT taken into consideration. The correlation for f/P obtained in this work is compared with that of Curl and Pitzer at Tr = 0.8, Chao et al. at Tr from 0.50 to 0.70, and that of Carruth and Kobayashi in the 0.50 ≤ Tr ≤ 0.64 region. Using the tabulated ZP and ZT values \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{H^* - H}}{{T_c }},{\rm }\left ({\frac{{\partial V}}{{\partial P}}} \right)_T $\end{document}, and \documentclass{article}\pagestyle{empty}\begin{document}$ \left ({\frac{{\partial V}}{{\partial T}}} \right)_P $\end{document} have been calculated and compared satisfactorily with the corresponding values derived from literature data. In addition, a correlation of vapor pressures of both hydrocarbons and nonhydrocarbons is also presented. The agreement between this correlation and those reported by Pitzer et al. and Carruth and Kobayashi is very satisfactory.
A simple algorithm for the time‐optimal control of chemical processes
Authors: Beard John N. , Groves Frank R. , Johnson Adrain E.
Published: June 2004

A simple algorithm for the time‐optimal control of chemical processes during setpoint changes, in processes which can be described by a second‐order lag plus dead time model, is described. Knowledge of the unsteady state model parameters is not required because the algorithm uses a dimensionless phase plane on which the switching curves are independent of system parameters for a given forcing function. The algorithm gives the parameters of a second‐order lag plus dead time model as a by product of the setpoint change. It is easily tuned and is relatively insensitive to changes in the process dynamics. The algorithm does not require a large computer or long computing times and has been implemented on both analog and digital computers in controlling computer simulated systems.
Coagulation of lead chloride aerosol in the presence of water vapor
Authors: Ranade M. B. , Wasan D. T. , Davies R.
Published: June 2004

Polydisperse submicronic lead chloride aerosols were generated from melt phase under dry and humid conditions. The particle size and concentration increased with increasing generation temperature. The aerosol particles generated in a dry atmosphere were pherical while the aerosol particles generated in humid atmosphere showed development of crystallinity at the surface.

Coagulation rates of the aerosol generated in a dry atmosphere were measured at room temperature under different humidities. The coagulation rates were in goodagreement with Smoluchowski's theory, modified to include the effect of polydisperisity and were unaffected by humidity. The interaction of lead chloride particles with the water vapor was characterized by a process of adsorption a the interfce. The coagulated aerosol exhibited a chain structure for humidities lower than 70% and, at higher humidities, compact agglomeration was observed.
Fault tree synthesis for chemical processes
Authors: Powers Gary J. , Tompkins Frederick C.
Published: June 2004

This paper outlines the concepts for a systematic approach to the safety analysis of chemical processing systems. A procedure for automatically generating fault trees is presented. The fault trees describe nearly all the failure modes for the system under analysis. The fault tree generation procedure uses information on (1) the description of the system (detailed flowsheet), (2) physical and chemical properties of materials in and around the system, and (3) unit models which describe the behavior of the units within the system and which are assembled to describe the behavior of the complete system. The unit models are connected to form an information flow structure for the complete processing system. Unit failure models are also defined for common chemical units. By systematically defining hazard states and searching the information flow structure for the system, it is possible to generate fault trees for the complete process. An analysis of the fault trees can reveal the important failure modes for the process.
Facilitated transport via carrier‐mediated diffusion in membranes: Part I. Mechanistic aspects, experimental systems and characteristic regimes
Authors: Schultz Jerome S. , Goddard Joe D. , Suchdeo Shyam R.
Published: June 2004

Carrier‐mediated transport in membranes as a globally nonreactive process is distinguished from film theory with chemical reaction and other facilitated diffusion phenomena. With the concept of stoichiometric and system invariants, an approach is developed for the analysis of carriersediated transport with multiple permeants involving multiple reactions in the membrane. Approximate solutions of the requisite differential equations according to the relative importance of diffusion and reaction rates are reviewed, as well as typical experimental studies. Criteria for evaluating whether a membrane is in the diffusion or equilibrium regime are given, and, in the latter case, the effects of some system parameters are given, for example, binding constants, competitive permeants.
Turbulent dispersion in drag‐reducing fluids
Authors: Taylor A. Richard , Middleman Stanley
Published: June 2004

Turbulent pipe flow was examined by measuring the radial dispersion of dyed fluid introduced at an axial point source within the flow. From the classical theoretical results of G. I. Taylor it was possible thereby to calculate various parameters that characterize the structure of the turbulent flow field. A comparison was made between water, and aqueous solutions of polyethylene oxide (Polyox) at concentrations up to 50 ppm (by weight). Results indicate that Polyox affects the turbulence in the following ways: (1) intensity is reduced, (2) the energy spectrum is shifted toward low frequency, (3) dispersion occurs largely through large scale motion, and intermittency is increased. Indication is also seen that a simple exponential form for the Lagrangian correlation coefficient is superior to other often recommended models.
Quadratically convergent techniques in linearly constrained optimization
Authors: Husen Gregory J. , Eakman James M.
Published: June 2004

Methods for the solution of linearly constrained optimization of a nonlinear objective function are presented and compared. The methods of Fletcher‐Reeves, Fletcher, and Powell are used to generate search directions in the decision variable space. Generalized Kuhn‐Tucker conditions are presented and used to check for a local minimum.
Growth rate of an ice crystal in flowing water and salt solutions
Authors: Vlahakis John G. , Bardhun Allen J.
Published: June 2004

The growth rate of an ice crystal in the basal plane has been measured in subcooled water flowing at velocities of 0.04 to 1 cm/s to test a theory of Fernandez and Barduhn (1967). The theory fits the data in pure water at all velocities and subcoolings studied here and at velocities up to 46 cm/s studied previously. The interfacial tension between ice and water calculated from these data is 33 ± 6 ergs/cm2, a value in good agreement with those determined by others.

Measured growth rates of ice from solution do not follow the theory and in fact are as much as 150% higher in 0.5 to 1% NaCl solution than in pure water. High subcoolings and low flow velocities accentuate this anomaly.
Diffusion in nickel oxide pellets–effects of sintering and reduction
Authors: Kim K. K. , Smith J. M.
Published: June 2004

Diffusion rates were measured at 25°C and 1 atm by a steady state method in pellets of nonporous nickel oxide particles in order to determine the effects of sintering and chemical reduction. Sintering led to a striking decrease in diffusion flux; tortuosities above 100 were found for highly sintered (porosity 0.03) pellets. Reduction caused a sharp increase in diffusion rate when the original pellet was highly sintered. For an originally unsintered pellet the diffusion rate decreased with extent of reduction.

These phenomena were explained quantitatively by using: (1) the random pore model to predict tortuosity factors for an unsintered, unreduced pellet, and (2) the extent of pore interconnections and the fractional reduction to treat the effects of sintering and reduction. In this way an approximate, predictive equation was derived which contained no arbitrary parameters and which required for application only data on porosity and extent of chemical reduction.