bluuebunny/crossref_metadata_2025_split huggingface dataset:
The change in pore size distribution from surface reactions in porous media
Authors: Schechter R. S. , Gidley J. L. 
Published: June 2004

AbstractWhen a porous solid is penetrated by a reactive fluid which changes the pore geometry, the macroscopic properties of that porous material may be greatly changed. A model is proposed in which the matrix is visualized as being a number of short cylindrical pores dispersed randomly throughout the solid. The change in the distribution of these cylindrical pores is then represented by a integrodifferential equation which is solved for two special cases.The evolution of the pore size distribution is determined by the particular way in which the solid‐liquid boundary takes place. The case considered here is that of a surface reaction which dissolves the solid thus continuously enlarging the pores. The rate of reaction is calculated theoretically using a laminar flow diffusion model and this growth rate expression is then taken as the basis for numerical calculations relating to the action of dilute hydrochloric acid on limestone.A comparison is made with experimental results and it is found that the model behaves in much the same way as the real system although the observed rate of pore growth was two to three times that predicted by the diffusion model. Several possible explanations for this discrepancy are being tested.An exact solution of the integrodifferential equation for highly retarded reaction rates has been found with the change in permeability being given in terms of the change in porosity. This result will permit a prediction of the stimulation that can be achieved in acidizing oil wells with retarded acids.
Mathematical analysis of bubble dissolution
Authors: Duda J. L. , Vrentas J. S. 
Published: June 2004

AbstractA perturbation series solution is derived for isothermal bubble dissolution and bubble growth from an initially finite size. The new solution is superior in several aspects to the quasi‐stationary and quasi‐steady state approximations derived previously. The accuracy and range of validity of the new results are investigated by comparison with finite‐difference solutions of the equations governing bubble growth or dissolution. In addition, previous numerical solutions of the problem are compared to the finite‐difference results of this study.
The experimental determination of the volumetric properties and virial coefficients of the methane‐ethylene system
Authors: McMath H. G. , Edmister W. C. 
Published: June 2004

AbstractAn apparatus was constructed for making isochoric measurements of P‐V‐T properties. Experimental compressibility factors were obtained and are presented for methane, ethylene, and four intermediate mixtures at 60, 40, and 20°F., with pressures from 260 to 2,220 lb./sq.in.abs. Second and third virial coefficients and interaction virial coefficients were determined from the data. The compressibility factors and the virial coefficients are compared with the Benedict‐Webb‐Rubin equation of state, applied in its original form and in a recent generalized form.
Viscoelastic jet stability
Authors: Kroesser F. William , Middleman Stanley 
Published: June 2004

AbstractThe breakup of a low speed horizontal jet is investigated. Weber's theory for the Newtonian jet is extended to a linear viscoelastic fluid. The theory predicts a dependence of breakup length on the elasticity number. Breakup lengths are measured for low concentration solutions of polyisobutylene in tetralin. Two molecular weights, several concentrations, and five capillary diameters were studied. A single correlation is obtained for all data which gives the breakup length as a function of the elasticity number, and the parameters of Weber's theory. At constant values of the Ohnesorge number and Weber number, the breakup length decreases with increasing elasticity number. The effect of the length of the capillary is studied. At large elasticity numbers short tubes give rise to slightly shorter breakup lengths than long tubes under identical flow conditions.
The aqueous phase oxidation of cyclohexane using gamma radiation
Authors: Ashline Ronald C. , Von Berg Robert L. 
Published: June 2004

AbstractA study was made of the radiolytic oxidation of cyclohexane in aqueous solution by using cobalt 60 gamma radiation. In the presence of dissolved oxygen gas the reaction proceeds irreversibly with the formation of a number of oxidation products. Those identified were cyclohexanol, cyclohexanone, and hydrogen peroxide. Trace quantities of carbon dioxide were also detected in the liquid phase. Using a constant dose rate of 15 × 104 rad./hr. in all runs, radiation yields were G(C6H11OH) = 0.49, and G(C6H10O) = 1.08. When molecular oxygen was excluded from the system, neither cyclohexanol nor cyclohexanone was formed on irradiation. A simplified kinetic model based on competition by the various solutes in the system for a single primary radical species produced by radiolysis of the solvent molecules is developed. Results generated using the mathematical model are compared with the experimental data. Excellent agreement between the observed and computed trends is noted at radiation doses up to 50 × 104 rad.
Optimal control of tubular reactors. Part II. Jacketed configuration with step feed disturbance
Authors: Chang K. S. , Bankoff S. G. 
Published: June 2004

AbstractThe optimal unsteady control of a jacketed tubular reactor with and without heat generation due to chemical reaction in response to a step disturbance in the feed stream concentration is computed. More rigorous control action was found to be necessary for the case with heat generation than without heat generation. Convergence of the method was also investigated with fixed and free final time.
Model simulation of adiabatic continuous flow stirred tank reactors
Authors: Keairns D. L. , Manning F. S. 
Published: June 2004

AbstractManning, Wolf, and Keairns' model for continuous flow‐stirred tank reactors has been extended to include adiabatic as well as isothermal operation. The adiabatic, steady state yield of a continuous flow‐stirred tank reactor was measured experimentally using the second‐order, homogeneous, exothermic reaction between sodium thiosulfate and hydrogen peroxide. Model predictions of overall tank yield agreed closely with the data, thus verifying the applicability of this model to explain the effects of operating variables such as impeller size, impeller type, agitator speed, feed location, feed concentration, and flow rates.
Thermally induced solid state polycondensation of nylon 66, nylon 6‐10 and polyethylene terephthalate
Authors: Chen F. C. , Griskey Richard G. , Beyer G. H. 
Published: June 2004

AbstractThe mechanism of solid state polycondensation has been subjected to a fundamental analysis. Equations were formulated for combined diffusion and chemical reaction for two separate situations. One was for solid state polycondensation in polymer flakes or chips. The other dealt with polymer powders. The resultant solutions related molecular weight changes to rate functions. A technique for deriving the rate functions from experimental data is described.Solid state polycondensations were then studied for nylon 66, nylon 6‐10, and polyethylene terephthalate. These data which ranged from 120 to 200°C. were tested with various mechanisms. The most appropriate one was found to be that developed in the present work. Chemical reaction was found to be the rate controlling step in solid state polycondensation in nylon 66, polyethylene terephthalate, powders of nylon 6‐10 and larger particles of nylon 6‐10 at and above 160°C. Diffusion of byproduct through the solid was the rate controlling step for larger particles of nylon 6‐10 at temperatures below 160°C. Thermograms of nylon 6‐10 indicated morphological changes which possibly influenced the behavior of the larger nylon 6‐10 particles. The Arrhenius relation was fitted to the situations where chemical reaction controlled.
Axial dispersion with time variable flow in multiphase systems
Authors: Gill William N. 
Published: June 2004

AbstractA theory has been developed for heat or mass transfer between phases which may have unsteady time dependent velocity fields. The configuration analyzed involves two concentric tubes, but the analysis can be extended to more than two phases, or streams, and to noncylindrical cross sections. For the configuration considered, the dispersion coefficient is found from first principles.It is noteworthy that the dispersion model given by Equation (15) or (63) and (64), which is consistent with the basic continuum model of Equations (8) and (9), is based on the superficial velocity rather than the interstitial velocity. This strongly suggests that experimental observations on packed beds, or other multiphase systems, should be interpreted on the basis of um, the superficial velocity, rather than the interstitial velocity which has been used often in the past.
Performance predictions for a cocurrent spray dryer
Authors: Baltas Leon , Gauvin W. H. 
Published: June 2004

AbstractA step‐by‐step prediction procedure has been developed to predict the evaporation of a sodium nitrate spray consisting of small drops moving at terminal velocity through the drying air. The procedure accounts both for the existence of radial gradients as well as radial mixing in the dryer and is selfsustaining except for values of the local air velocity.Because the procedure can be applied only to the free‐fall zone, at some distance below the nozzle, a method was developed for the indirect determination of the amount of water remaining in the partly evaporated droplets at the beginning of the free‐fall zone. This procedure was then applied to experimental data on drop size distributions obtained at the beginning of this zone. Owing to uncertainties concerning the salt concentration in the drops, a number of assumptions had to be made and the procedure was only partially successful in describing the spray evaporation, although it did compute the radial spray transfer. It was possible, however, to indicate by means of a model drop distribution the general validity of the procedure.
Transport characteristics of a cocurrent spray dryer
Authors: Baltas Leon , Gauvin W. H. 
Published: June 2004

AbstractThe design of an experimental cocurrent spray dryer and its method of operation are described. The rationale for the development of some new measurement techniques and modifications to existing ones is discussed. These techniques were used to obtain profiles at several dryer levels of the air velocity, air humidity, and spray mass velocity for the case of a 30% sodium nitrate solution sprayed into 100°C. air. Somewhat less detailed measurements of the spray moisture and radial turbulent diffusivity were also made.The humidity and spray moisture measurements gave very nearly identical results for the progress of the evaporation along the length of the dryer. The axial injection of the spray was found to result in steep gradients for the air velocity, air humidity, and salt mass velocity but these were found to decay under the influence of turbulent mixing which is also generated by the spray injection.
A numerical solution for the single‐screw extrusion of a polymer melt
Authors: Dyer David F. 
Published: June 2004

AbstractA general numerical‐analysis procedure is presented for the screw extrusion of a non‐Newtonian material. The full Navier‐Stokes energy and continuity equations are used in the numerical procedure. The flow is taken as steady and incompressible, and the viscosity is written according to the Ostwald‐de Waele model in which the viscosity is assumed to be inversely proportional to the square root of the second invariant of the rate of deformation tensor and exponentially dependent on the temperature.The procedure allows the prediction of vorticity, stream‐function, swirl velocity, internal energy, and viscosity over any cross section of a groove containing plastic. Calculations for the mass extrusion rate and power consumption (shear rate) for the screw extruder are also given. Typical cases are considered for which all the quantities listed above are determined. The results compare favorably with other theoretical work.
Static pressure and velocity profiles in swirling incompressible tube flow
Authors: King M. K. , Rothfus R. R. , Kermode R. I. 
Published: June 2004

AbstractThe phenomenon of reversing axial flow in swirling incompressible flow through a tube has been investigated experimentally. The study was carried out in a 2 in. I.D. test section of plexiglass tubing 10 ft. long. The swirl was introduced by injection of the total fluid stream through two symmetric tangential inlets perpendicular to the tube. Measurements have been made with specially constructed stagnation and static pressure probes.Velocity and pressure profiles obtained for tests conducted at four Reynold's Numbers in one fixed geometrical configuration are presented and discussed in general terms. Swirl decay rate is characterized in a plot of weighted tangential velocity/inlet velocity ratio versus distance along the test section from the inlets. A model presented by a previous investigator to explain the flow reversal phenomenon is discussed in the light of present work. Finally the data is used in an order of magnitude analysis to reduce the turbulent Navier‐Stokes equation describing the flow to simpler (though still indeterminate) form.
Scale‐up criteria for stirred tank reactors
Authors: Evangelista J. J. , Katz Stanley , Shinnar Reuel 
Published: June 2004

AbstractA method is derived for the design of stirred tank reactors for homogeneous reactions. A simple mixing model proposed previously by Curl (4) is used to compute the effects of finite mixing time on complex chemical reactions. It is also shown how the parameters of the model can be obtained by tracer experiments, or estimated theoretically by the assumption of isotropic turbulence. It is shown that in many practical cases the assumption of ideal mixing is a good approximation. However, the effects of imperfect mixing are more likely to be felt in a large reactor than in a pilot plant. Some quantitative examples are discussed. Methods are derived to compute the average outlet concentration for complex systems such as autothermic reactions, polymerization, crystallization, etc.
Combined forced and free convective diffusion in vertical semipermeable parallel plate ducts
Authors: Ramanadhan Krishnan , Gill William N. 
Published: June 2004

AbstractThe effect of natural convection on polarization and flow patterns in liquid phase convective diffusion in a vertical duct with semipermeable membrane walls has been investigated theoretically. It is found that at low flow rates, gravitational fields can play a significant role in distorting the velocity profiles and thereby they affect the transition from laminar to turbulent flow. Natural convection also significantly affects mass transfer rates and therefore the extent of polarization at low flow rates. Results are presented for both momentum and mass transfer in upward and downward flows for different wall Peclet numbers. The hydrodynamic stability of the system also has been investigated and critical values of the buoyancy parameters are reported. Also, these results enable one to estimate when natural convection may create errors in membrane testing systems.The analysis and results are of practical interest in reverse osmosis and other membrane separation processes. The more productive the system, the more likely it will be that buoyancy effects are important.
Simultaneous flow and temperature correction in the equilibrium stage problem
Authors: Tierney John W. , Yanosik John L. 
Published: June 2004

AbstractIterative methods for the solution of the steady state equilibrium stage problem are studied. Equations are first developed for calculating the effect of a change in temperature or flow rate on all energy balances, and then it is shown that these equations can be used in the multiple variable form of the Newton‐Raphson correction process to correct either the temperatures or the flow rates when only energy balance errors are used. Similar equations for material balance errors which have been developed previously are then combined with the energy balance equations to provide a method for simultaneous correction of the temperatures and the flow rates. Because first‐order interactions between flow rates and temperatures are included the method is applicable to a wide range of equilibrium stage problems. Sample problems are presented, and it is shown that quadratic convergence is obtained for the simultaneous correction process.
On integration of the coexistence equation for binary vapor‐liquid equilibrium
Authors: Van Ness H. C. 
Published: June 2004

AbstractNumerical integration of the coexistence equation for isothermal P‐x data can be carried out by standard techniques. Two questions are considered with respect to this procedure: (a) Do continuous, analytic P‐x relations exist which fail to provide thermodynamically acceptable results? (b) Does it matter from what point one starts the numerical integration? It is the purpose of this paper to demonstrate in each case that the answer is affirmative.
Fixed bed adsorption drying
Authors: Chi C. W. , Wasan D. T. 
Published: June 2004

AbstractIn this paper, mathematical models for a single adsorbate component present in a gas phase have been developed for isothermal and adiabatic dynamic adsorption‐desorption processes with special emphasis on adsorption drying by supported hygroscopic salts. The proposed generalized models are applicable to both an unsupported absorbent bed and a fixed bed of adsorbents impregnated on a supporter which may have nonlinear equilibrium relationships. The partial differential equations governing the dynamic adsorption‐desorption processes and the nonlinear equilibrium relations were solved numerically on the digital computer.An experimental study was conducted to measure the adsorption and desorption rates of water vapor by lithium chloride impregnated on a solid supporter, Torvex.The proposed adiabatic adsorption‐desorption model has been verified for unsupported adsorbent beds in the cases of water vapor adsorption from air by silica gel and of methane adsorption from a helium‐methane mixture by activated carbon. The validity of the generalized adiabatic model for supported adsorbent beds with nonlinear equilibrium relationships was established by a direct comparison of experimental data obtained in this study with the predicted values.
Numerical evaluation of temperature profiles and interface position in filaments undergoing solidification
Authors: Morrison Milton E. 
Published: June 2004

AbstractA numerical method has been described for the solution of the general equations which depict solidification in the cylindrical coordinate system. The method has been outlined for cooling and solidification of a moving filament of molten polymer. The solution is given in terms of six dimensionless variables: αl/αs,kl/ks,hR/kR,L/[Cps(To−Tc)],To/Tc, and σϵpR(To−Tc)3/kR. Plots are shown for the solution of the heat transfer equations and associated boundary conditions for several values of the dimensionless variables. The method describes the process of cooling and freezing liquids when convective and/or radiative energy losses are considered. The form of the theoretical equation compares very favorably with experimental data.
Evaporation rates of volatile liquids in a laminar flow system: Part I. Pure liquids
Authors: Clark Michael W. , King C. Judson 
Published: June 2004

AbstractNormal pentane and isopentane were evaporated into nitrogen in laminar, concurrent flow in a rectangular channel. Composition profiles within the gas phase were measured, and the evaporation rates were compared with theoretical predictions with satisfactory agreement. The interfacial mole fraction of the evaporating species in the gas phase ranged as high as 0.74. A solution is reported for the Leveque problem under high flux conditions.
Mass transfer in a nonuniform impinging jet: Part II. Boundary layer flow‐mass transfer
Authors: Scholtz M. T. , Trass Olev 
Published: June 2004

AbstractExact solutions of the boundary layer equations were used to calculate the local mass transfer coefficients for an impinging jet with a parabolic velocity distribution. Boundary conditions were obtained from an inviscid flow solution and also from experimental pressure distributions. Experimental data for the air/naphthalene system were in good agreement with theoretical results. Mass transfer from the impingement surface was independent of nozzle height in the range 0.5 to 12 nozzle radii. For lower nozzle heights the effect of the constriction of flow between the nozzle and the surface led to increased transfer rates near the nozzle wall; data followed the predicted behavior.
Vapor‐liquid equilibria and dielectric constants for the helium‐carbon dioxide system
Authors: Burfield Diana W. , Richardson H. P. , Guereca R. A. 
Published: June 2004

AbstractPhase equilibria data are presented for the helium‐carbon dioxide system at 253°, 273°, and 293°K. and pressures to 139 atm. Equilibrium is established under flow followed by nonflow conditions, and liquid and vapor samples are isolated without disturbing equilibrium. Liquid‐and vapor‐phase compositions are monitored with miniaturized capacitors, and compressibility factors are computed from resulting dielectric constants. The data are internally consistent and compare favorably with available literature values.
Thermocapillary flow around hemispherical bubble
Authors: Larkin Bert K. 
Published: June 2004

AbstractA hemispherical bubble, attached to a plate, is surrounded by an initially quiescent and isothermal liquid. By suddenly heating the plate, a thermal gradient over the bubble surface results. Because surface tension is temperature dependent, tangential stresses arise at the bubble surface. The liquid is viscous, and motion in the liquid phase begins. Such motion is an example of thermocapillary flow. This problem, besides being of interest from a fundamental point of view, is of possible concern in the design of space vehicles capable of storing cryogenic fluids for long periods of time in a weightless condition.Solutions to the problem are developed by numerical treatment of the governing equations. Flow and temperature fields, which depend upon the Prandtl and Marangoni numbers, were obtained for Prandtl numbers 1 and 5 and Marangoni numbers from 0 to 100,000.Results show that liquid is pulled toward the intersection of the bubble and the plate, then flows around the bubble surface, and leaves the bubble as a jet. The extent of the jet increases with increasing Marangoni number and decreases with increasing Prandtl number.Thermocapillary flow increases heat transfer (Nusselt number) over that obtained from conduction, but the increase is modest. The Nusselt number increases with the Marangoni number and is insensitive to the Prandtl number. At a Marangoni number of 40,000, the local Nusselt number was increased by a factor of 2. In order for thermocapillary flow to become a dominant heat transfer mechanism, the Marangoni number must exceed 100,000.
Correlation and prediction of vapor‐liquid equilibria with the redlich‐kwong equation of state
Authors: Zudkevitch David , Joffe Joseph 
Published: June 2004

AbstractA modified Redlich‐Kwong equation has been applied to the calculation of phase equilibria in multicomponent systems. The two parameters of the Redlich‐Kwong equation are treated as temperature functions. They are obtained for each pure component from experimental vapor pressures and liquid densities with the help of a generalized fugacity coefficient correlation for saturated vapors. The need to submit coefficients for pure components is thus eliminated. At least one experimental vapor‐liquid equilibrium point is required to establish an interaction constant for each binary system. Applications have been made to binary and multicomponent systems containing hydrocarbons, hydrogen, carbon dioxide, and hydrogen sulfide.