bluuebunny/crossref_metadata_2025_split huggingface dataset:
An analytical investigation of the flow in the saturated zone of ice counterwashers
Authors: Barak Amitzur , Dagan Gedeon 
Published: June 2004

AbstractThe flow of brine through the ice bed in gravitational counterwashers is investigated by analytical methods. Two types of counterwashers are considered: a drained‐top counterwasher and a flooded one. Only counterwashers of rectangular cross section and two dimensional flows are investigated. By assuming that the ice crystals move vertically upwards with a uniform velocity and that the relative flow of brine and wash water with respect to the ice bed obeys Darcy's law, the differential equations and the boundary conditions of the flow are derived. The solutions are obtained by using complex variables and conformal mapping. The solutions are presented as formulae, which make possible the rational design of counterwashers and the optimization of their dimensions and operation parameters.
The measurement of surface temperatures with platinum films during nucleate boiling of water
Authors: Foltz G. E. , Mesler R. B. 
Published: June 2004

AbstractThis report describes a simple and reliable method of constructing small platinum film thermometers on Pyrex glass. The thermometers were used to measure surface temperature during nucleate boiling of water at pressures between 1 and 4 lb./sq.in. abs. The thermometers showed that as superheated microlayers of water evaporated beneath vapor bubbles, the surface temperature often dropped 40° to 75°F. before ultimately reaching the saturation temperature. The thermometers proved to be accurate (±1°F.) and capable of fast response (145°F./msec.).
A diffusion model for reactions with turbulent mixing
Authors: Mao K. W. , Toor H. L. 
Published: June 2004

AbstractA diffusion model based on the simultaneous interdiffusion and reaction between alternate slabs of reactants is used to simulate the data of Vassilatos and Toor. After slab sizes are chosen to fit the conversion data for very rapid reactions in a stoichiometric mixture, reasonably good predictions are obtained of the effect of stoichiometry and reaction velocity constant on conversion. The results are close to the predictions of Kattan and Adler's stochastic mixing model, and the similar behavior of these disparate models implies that conversion is insensitive to the details of the mixing.
Cell model theory of homogeneous fluidization: Density and viscosity behavior
Authors: Saxton James A. , Fitton John B. , Vermeulen Theodore 
Published: June 2004

AbstractAs a step toward a unified treatment of particulately fluidized beds, a statistical‐thermodynamic approach has been investigated, with the smoothed potential cell theory of pure liquids used to establish an equation of state and a collisional‐viscosity relation. This treatment has correlated well with experimental data on liquid‐fluidized beds, and the same method gives reasonable predictions for gas‐fluidized beds. A parameter equivalent to thermodynamic temperature has been identified for fluidized beds, which depends solely upon fluid properties and includes the three‐halves power of superficial velocity. This approach should be of value for interpreting other liquidlike properties of fluidized systems.
The effect of turbulence on hot‐film anemometer response in viscoelastic fluids
Authors: Serth R. W. , Kiser K. M. 
Published: June 2004

AbstractFrom studies of turbulence in round jets of Newtonian and non‐Newtonian fluids, it has been found that the response of wedge shaped, hot‐film probes can be influenced by the structure of the flow. In water and in weakly viscoelastic fluids the probe is little affected by turbulence, but for more highly viscoelastic fluids the rate of heat transfer from the hot film is markedly increased. Increases as great as 37% were found in this work; this corresponds to a 250% increase in apparent velocity. For this reason, care must be taken in interpreting measurements obtained with hot‐film wedges (and probably cylinders and cones also) in flows with both laminar and turbulent regimes.
A liquid‐phase adsorption study of the rate of diffusion of Phenol from aqueous solution into activated Carbon
Authors: Miller Conrad O. M. , Clump Curtis W. 
Published: June 2004

AbstractThe differential equation for diffusion of a solute in a quasi‐homogeneous, spherical, ion exchange particle, previously solved for time‐dependent boundary conditions, is applied to an activated carbon adsorption system. This solution differs from the infinite volume solution which assumes constant boundary conditions. The result is applied to experimental data and yields effective adsorbent‐phase diffusion coefficients. Equilibrium and rate studies were performed by using the aqueous phenol solution—activated carbon system. The rigorous solution to the diffusion equation is compared with a recently published frequency domain solution. Excellent agreement is obtained for values of the effective diffusion coefficient computed from the two rate equations.It is recommended that the rigorous model be used for mechanism and diffusion coefficient determination. After the mass transfer parameters have been obtained, the simplified rate equation may be used for either lumped parameter or distributed parameter models for prediction of fixed‐bed adsorber response. Further studies are required to determine if the simplified model adequately describes fixed‐bed behavior.
The structuring of process optimization
Authors: Christensen James H. 
Published: June 2004

AbstractThe efficiency of process optimization by mathematical programming can be increased by tearing, that is, rearranging the design equations so as to reduce the number of equality constraints. The structure of a system of equations may be depicted as an undirected bipartite graph; algorithm I‐T utilizes this graph to determine an order of solution for the equations which requires no tears. If this is impossible, then algorithm II‐T uses indexing in conjunction with algorithm I‐T to produce an order which minimizes the number of torn equations. This procedure is extended to the problem of minimum recycle parameters, and the two‐way interaction between tearing and algebraic simplification is illustrated.
Conversion and temperature profiles for complex reactions in laminar and plug flow
Authors: Merrill Lavaun S. , Hamrin Charles E. 
Published: June 2004

AbstractAn investigation of the mass and heat transfer equations describing radial and axial profiles for tubular reactors in laminar and plug flow is reported. Reactor conditions evaluated were isothermal, constant wall temperature, and adiabatic. Both diffusion and nondiffusion were considered. The reaction investigated was the demethylation of toluene in the presence of hydrogen.It was found that diffusion plays only a minor role in laminar flow for the conditions investigated. It was also found that isothermal and constant wall temperature reactor operation affected the temperature and concentration profiles very little when r/R was less than 0.6.
Simultaneous energy and mass transfer in the laminar boundary layer with large mass transfer rates toward the surface
Authors: Manganaro J. L. , Hanna O. T. 
Published: June 2004

AbstractThe laminar boundary‐layer equations are solved asymptotically for simultaneous mass and energy transfer in a variable property binary gas mixture when one component is rapidly transferred toward the surface. Flow is past a surface of arbitrary geometry, and both forced and free convection are studied. Advantage is taken of a mole fraction formulation of the boundary‐layer equations, which considerably simplifies the final results. General results are obtained for energy and mass transfer rates when physical properties are arbitrary functions of both temperature and composition. By considering two sets of property variations, representing extremes between which many actual variations lie, it is shown that in many forced convection problems the rates of energy and mass transfer can be expressed in a particularly simple form. The results also show that property variations are generally more important for free convection than for forced convection.
Upper and lower bounds on the drag coefficient of a sphere in an Ellis model fluid
Authors: Hopke Scott W. , Slattery John C. 
Published: June 2004

AbstractHill's extremum principles are not directly applicable to an Ellis model fluid. A method of adapting Hill's principles to the Ellis model was developed and used to calculate upper and lower bounds on the drag coefficient for a sphere moving slowly through such a fluid. Available experimental data were compared with the average of the upper and lower bounds. Agreement was poor with Slattery's data and good with Turian's data. Some reasons to suspect Slattery's data have been pointed out.
A new simulation method for equilibrium stage processes
Authors: Tomich John F. 
Published: June 2004

AbstractThis paper presents a new, general method for mathematical simulation of equilibrium stage operations. The procedure solves component material balance equations with a tridiagonal matrix algorithm. Heat balances and summation equations are handled with Broyden's method. The unique feature of this procedure is that, in a mathematical sense, all equations are solved simultaneously. Therefore, the method can be used for all types of equilibrium stage processes. Additionally, the use of Broyden iteration insures solutions which are both stable and more rapid than current techniques. An exact solution for a twenty tray column with twenty components takes approximately 30 sec. on an IBM 360/65 computer. Successful simulations have been made for both absorption and distillation type of operations which have included complex columns with multiple feeds and side product streams. Design applications of the method cover a variety of equilibrium stage processes in the chemical and petroleum industries.
Single drop breakup in developing turbulent pipe flow
Authors: Swartz John E. , Kessler David P. 
Published: June 2004

AbstractAn experimental study was made on the breakup of a single drop in two phase liquid‐liquid developing turbulent pipe flow. The predominant breakup mechanism was controlled by dynamic pressure forces, and the drop breakup was characterized by one or two smaller drops breaking off a larger drop.The effect on the increase in interfacial area and the resulting size distribution of the fragmented drops of drop velocity, interfacial tension, initial drop size, and the distance down the pipe was studied. Regression analysis was used to determine the significant effects. Most of these regression equations had significant cubic and two‐factor interactions, which is indicative of the complexity of drop breakup.The size distribution of the fragmented drops can be approximated by a normal distribution. However, the steady state distribution was not fully developed in the work here.
Combined reactors: Formulation of criteria and operation of a mixed tubular semifluidized reactor
Authors: Rao Kothapalli Babu , Doraiswamy L. K. 
Published: June 2004

AbstractCombined reactors in which the mixed reactor is followed by a tubular reactor can be optimal for a large number of simple adiabatic exothermal reactions. In the present paper, optimality criteria defined earlier for simple reactions involving a single reactant species have been extended to reactions involving two reactant species and for a system of consecutive reactions.The oxidation of benzone has been studied in an adiabatic semifluidized mixed tubular (MT) reactor. A definite improvement is possible when the oxidation is carried out in this reactor, as observed by a comparison of the experimental results obtained in tubular, mixed, and MT reactors under adiabatic conditions.
Absorption and scattering of thermal radiation by a cloud of small particles
Authors: Nagy A. R. , Lenoir J. M. 
Published: June 2004

AbstractAn experimental investigation was made of the absorption and scattering of thermal radiation by a cloud of small, spherical, micronsized, aluminum oxide particles in a plane‐parallel enclosure. By using carbon tetrachloride and carbon disulphide as suspendign media, transmission measurements were made with collimated and diffuse sources for wavelengths from 2 to 11μ. By employing a two‐flux diffuse model, the data were correlated to obtain absorption and back‐scattering cross sections. From the diffuse and collimated data, a backscattering coefficient was found which varied linearly with relative refractive index. With the developed coefficients, the absorptivities of the cloud of particles were determined.
An optimal control algorithm using the Davidon‐Fletcher‐Powell method with the fibonacci search
Authors: Birta Louis G. , Trushel Peter J. 
Published: June 2004

AbstractA numerical method for solving a class of nonlinear optimal control problems is presented. The approach reformulates the associated two‐point boundary value problem as a multidimensional minimization problem. This problem is, in turn, solved by using the method of Davidon‐Fletcher‐Powell. The one‐dimensional minimization problem implicit in the implementation of the Davidon‐Fletcher‐Powell algorithm is handled with the Fibonacci search technique. Several examples are presented to demonstrate the effectiveness of the method for problems with and without magnitude constraints on the control variable(s).
On the numerical solution of problems in multicomponent distillation at the steady state II
Authors: Billingsley D. S. 
Published: June 2004

AbstractA modification is presented of the Kb method described by Holland. This modified procedure exhibits substantially improved convergence characteristics when compared with the unmodified procedure or with the classical bubble point approach. Further, it provides by far the fastest algorithm known to the author. A second procedure for determining stage temperatures is also given. In this method, flow equations as well as equilibrium relations are satisfied by the temperature profile at each iteration. Next, an improved scheme for handling nonideal mixtures is given. Finally, it is shown that a positive solution to the convergence acceleration equations of Holland may not exist when this procedure is applied to a purity specification.
Statistical models for surface renewal in heat and mass transfer. Part III: Residence times and age distributions at wall surface of a fluidized bed, application of spectral density
Authors: Koppel L. B. , Patel R. D. , Holmes J. T. 
Published: June 2004

AbstractA method was developed for estimating the age density of transporting elements at a transport surface by using the spectral density of the total element counts. Only total counts, and not individual element histories, need be observed. The method was compared with autocorrelation methods used in an earlier work. Residence times were measured for several sizes of particles at a paticular wall surface of a stirred fluidized bed and at various gas velocities using both spectral density and autocorrelation methods. A dimensionless plot brought all data points near a single curve, valid only for this surface in this bed. Checks of these residence times against values obtained by direct observation of individual particles confirmed the methods.
Acoustic isotherms for argon, nitrogen, methane, tetrafluoromethane, dichlorodifluoromethane, and their mixtures, plus derived interaction potential force constants
Authors: Nierode D. E. , Lewis J. L. , Gaggioli R. A. , Obert E. F. 
Published: June 2004

AbstractAcoustic velocity data for various isotherms from 1 to 70 atm. are presented for argon (32°F.), nitrogen (32°F.), methane (32°, 70°F.) tetrafluoromethane (32°, 70° F), dichlorodifluoromethane (240°F., p < 30 atm.), and various mixtures (32°F.). Interaction potential force constants for the pure gases are derived from the acoustic data with values for tetrafluoromethane and dichlorodifluoromethane differing significantly from previous literature values. BWR constants are also reported for argon and tetrafluoromethane.
Birefringent flow visualization of transitional flow phenomena in an isosceles triangular duct
Authors: Hanks Richard W. , Brooks James C. 
Published: June 2004

AbstractA flow visualization study was made with an optically birefringent solution of milling yellow dye in water flowing through a transparent duct of isoceles triangular cross section. The present data confirm a number of theoretical predictions concerning transitional phenomena in triangular ducts. One of the most interesting of these phenomena is the existence of a region of simultaneous laminar and turbulent flow in the duct. The present results, which agree with the theory, indicate an order of laminar and turbulent flow which is inverse to previous observations made with smoke filament tracings.
Evaluation of models for tubular, laminar flow reactors
Authors: Andersen Theodore S. , Coull James 
Published: June 2004

AbstractSignificant error can result when the plug flow model is applied to the analysis or design of luminar flow reactors due to nonconstant radial profiles of velocity, composition, and temperature.An analysis and comparison of suitable models for the nonisothermal, homogeneous, first‐order, irreversible, laminar, gas flow reactor has shown the finite‐difference solution for radial profiles to be superior to the power‐series approximation of radial temperature and composition profiles.New capabilities of the present computer solution include isothermal or adiabatic wall, dilute or concentrated feed, any stoichiometric product‐to‐reactant ratio. Chapman‐Enskog model for gas diffusivity, calculation of both heat transfer parameters, and a correction factor to apply to plug flow calculations.The new, improved computer solution may be used in the basic design or analysis of tubular, laminar flow reactors.
Heterogeneous reactions in the photochlorination of propane
Authors: Boval Bruno , Smith J. M. 
Published: June 2004

AbstractAn experimental study of the photochlorination of propane was undertaken to assess the significance of heterogeneous termination steps (wall reactions). Data were obtained in 2‐ and 10‐mm. I.D. tubular flow reactors with varying oxygen concentrations. The results indicated that homogeneous terminations were dominant in the large reactor, and heterogeneous ones were dominant in the small unit. A kinetic scheme which explained the data was proposed. It included two parallel termination steps: a second‐order homogeneous reaction between C3H7. and oxygen and a first‐order heterogeneous reaction between C3H7. and the reactor wall.Even though the data were taken in the laminar flow regime, the rate of reaction was a function of Reynolds number for the 10‐mm. reactor. Kinetic factors may explain these results, but the reasons are not clear. More research in this area is needed.Data taken in the 10‐mm. reactor packed with quartz cylinders gave results similar to those for the 2‐mm. reactor. This provided confirming evidence for the proposed scheme of parallel, heterogeneous and homogeneous termination steps.
Purge dynamics of fuel cells
Authors: Gidaspow Dimitri , Sareen Sarvajit 
Published: June 2004

AbstractAn anisotropic porous media model has been suggested for fluid motion in fuel cell cavities and has been shown to be valid experimentally with an actual fuel cell plate. Analytical solutions for pressure, velocity, and stream function have been obtained for finite and for point sources and sinks in rectangular cavities. Constant purge time curves have been constructed.
Hemolysis in simple shear flows
Authors: Shapiro Stephen I. , Williams Michael C. 
Published: June 2004

AbstractWhole human blood was sheared in the flow field of a concentric cylinder Couette viscometer in the hope of isolating the physical traumas specifically related to the escape of intracellular hemoglobin. The experimental results indicated that laminar shear stresses per se were not instrumental within the investigated range (up to 600 dynes/sq.cm.). This, plus the hematocrit dependence, evidenced the importance of interaction of individual red cells with a surface in the hemolytic event.
Heat and mass transfer in a channel with surface mass addition: Application to phase change processes
Authors: Sparrow E. M. , Yu H. S. 
Published: June 2004

AbstractThe heat and mass transfer processes in a binary mixture flowing in a parallel plate channel with mass addition at the bounding surfaces are investigated analytically. The rate of mass addition, the temperature, and the mass fraction are arbitrarily prescribed at each of the bounding walls. Similarity solutions are evaluated numerically to yield pressure gradient, Nusselt number, and Sherwood number results for a wide range of each of three governing parameters. It is found that increasingly strong surface mass addition markedly increases the magnitude of the axial pressure gradient. Mass addition decreases the Nusselt and Sherwood numbers at the channel wall at which the injection is strongest but may actually increase these moduli at the opposite wall. A generalizing analysis is performed to accommodate phase change processes as well as to accommodate the specification of plenum conditions rather than wall surface conditions. Application is made to the evaporation of liquid water by an air stream. It is shown that the rate of evaporation is augmented as the rate of air injection increases, but the extent of the augmentation is less than the causative increase in the air flow rate.
Analysis of kinetic parameters from batch and integral reaction experiments
Authors: Seinfeld John H. , Gavalas George R. 
Published: June 2004

AbstractThe estimation of chemical reaction rate constants from experimental batch or integral reactor data is examined. Consideration is given to the effect on the accuracy of the parameter estimates of the number of concentrations measured, extending the range of measurements to higher conversions, and experimental errors. The study is based on estimates of two rate constants obtained by quasilinearization in the pyrolytic dehydrogenation of benzene. It is found that if fewer than the number of independent components are to be measured, certain components produce better parameter estimates than others. The level of experimental errors is by far the most significant factor in obtaining reliable parameter estimates.
Predicting fractionator dynamics by using a frequency domain solution technique
Authors: Bollinger R. E. 
Published: June 2004

AbstractMethods are described for predicting the dynamic behavior of high purity fractionators. The paper shows how to model both the composition and hydraulic response in towers with many trays and in towers which are subject to a variety of disturbances. The technique involves the transformation of the linear dynamic equations to the frequency domain and the solution of the resulting complex algebraic equations for specific values of frequency. The paper includes a description of the model formulation, solution, and validation, and applications including the design of feedforward controllers.
Small surface waves and gas absorption
Authors: Dick G. F. , Marchello J. M. 
Published: June 2004

AbstractSurface renewal models based on wave induced drift currents are proposed to explain gas absorption data in deep tanks. A model assuming plug surface flow was found to best represent the available data for the absorption of carbon dioxide, oxygen, propylene, and helium into water. Velocities obtained by fitting the mass transfer data agree with experimental velocities obtained from dye studies.