bluuebunny/crossref_metadata_2025_split huggingface dataset:
Local and macroscopic transport from a 1.5‐in. Cylinder in a turbulent air stream
Authors: Galloway T. R. , Sage B. H. 
Published: June 2004

AbstractThe local and macroscopic thermal transfer coefficients were experimentally investigated for a 1.5‐in. copper cylinder located in a transverse flowing turbulent air stream. Measurements of local transport and pressure coefficient were made throughout the entire perimeter of the cylinder. The Reynolds number was varied from 2,600 to 86,000 and the free‐stream turbulence from 0.013 to 0.25. The estimated integral turbulence scale was found to vary from 0.3 to 0.5 in. over the range of conditions of flow investigated. The local transfer coefficient near stagnation increased 35% as a result of an increase in turbulance over the range indicated. Displacements of the locus of separation with varying Reynolds numbers and turbulence level were found.
Gas‐liquid mass transfer with a tangentially moving interface: Part II. Experimental studies
Authors: Byers Charles H. , King C. Judson 
Published: June 2004

AbstractA horizontal, rectangular channel of high aspect ratio has been built for the study of interphase mass transfer in stratified, laminar gas‐liquid flow. Cases were examined where the resistance to mass transfer is confined to the gas phase and where the control is distributed between phases. Measurements of the rate of evaporation of ethanol into oxygen and carbon dioxide confirmed that cocurrent interface motion enhances gas phase‐controlled mass transfer coefficients substantially. On the other hand countercurrent motion of the interface decreases the coefficient. Agreement with basic convective diffusion theory was found for the evaporation of ethyl ether into helium and carbon dioxide from dilute solutions in ethanol, cases where the mass transfer control is distributed between the phases. Experiments with aqueous solutions were hampered by the accumulation of surfactants at the interface. A diaphragm cell technique was used to measure diffusivities of 0.87 × 10−5 sq.cm./sec. for ethyl ether at high dilution in ethanol and 0.96 × 10−5 sq.cm./sec. for ethyl ether at high dilution in water at 25°C.
On a tracer method for evaluating catalytic data
Authors: Kuo James C. W. , Wei James 
Published: June 2004

AbstractThis paper presents theoretical studies of a method of using a radioactive tracer technique to evaluate the kinetic data of heterogeneous catalytic reactions that are coupled with a Knudsen type of pore diffusion. By superimposing a transient radioactive tracer response over the steady state concentration profile in the catalyst particle, one can establish an implicit relation between the total amount of radioactive components diffused out of the particle and the kinetic data of the reaction system. This relation can then be used to evaluate kinetic data of the reaction system. A detailed study of general monomolecular complex systems is given. Use of the method for nonlinear systems is also included.
Kinetics of the aluminum‐chlorine reaction
Authors: Cozewith Charles , Li Kun 
Published: June 2004

AbstractThe reaction between aluminum, in the form of flat plates, and chlorine was investigated in a flow system at temperatures from 500° to 650°F. Gaseous aluminum chloride was the reaction product at these temperatures. At 500°F. the reaction proceeded by pitting, and the rate appeared to be chemically controlled. The reaction mechanism changed at higher temperatures to give a smooth reacted surface, and the reaction rate was found to be dependent upon both mass transport and kinetic parameters. The method proposed by Rosner for calculating mass transport‐dependent reaction rates was found to correlate both average and local rate data and was used to obtain estimates of the kinetic parameters for the heterogeneous surface reaction.
Laminar dispersion in capillaries: Part IV. The slug stimulus
Authors: Gill William N. , Ananthakrishnan V. 
Published: June 2004

AbstractAn exact analytical theory of the local behavior of finite slugs which are dispersed in three‐dimensional velocity fields is developed. It is shown that the dispersion coefficient enters the problem as an eigenvalue. For the important special case of fully developed straight pipe flow, considered first by Taylor and later generalized by Aris, the dispersion coefficient can be found very easily by the present method, which also provides the basis for studying a large class of more complicated problems.A detailed numerical analysis is carried out to determine the limits of applicability of the analytical theory. Fortunately, it is found that dispersion of slug stimuli in fully developed laminar tube flow is described by Equation (15) when τ exceeds certain minimum values which depend only weakly on Peclet number and are independent of slug length in the region considered here. Since peak mean concentrations are predicated accurately by Equation (19) for X > 0.1, this is a convenient quantity to use to determine dispersion coefficients experimentally.On comparing the numerical and analytical results for local point concentrations, good agreement is found, provided the average concentration is predicted accurately by Equation (15). This is significant because it implies that a broad class of difficult transient heat and mass transfer problems, with aperiodic inlet disturbances, can be solved by using superposition in conjunction with the present approach.
Some observations on the effect of interfacial vibration on saturated boiling heat transfer
Authors: Nangia K. K. , Chon W. Y. 
Published: June 2004

AbstractAn experimental investigation was carried out to determine the effects of vibration of the heat transfer surface in saturated pool boiling of water at atmospheric pressure. Wires of 0.01 in. diameter were heated electrically and vibrated electromagnetically at frequencies ranging from 20 to 115 cycles/sec. and amplitudes from 0.0118 to 0.0701 in. An increase in heat transfer up to a maximum of 200% at low ΔTwas observed for an increase in frequency and/or amplitude. At a heat flux of 105B.t.u./(hr.) (sq. ft.) high‐speed motion pictures were taken at 4,800 frames/sec. of a wire vibrating at 45 cycles/sec. with an amplitude of 0.0492 in. Comparison of these films with those taken at the same heat flux without vibration showed that the generating period and diameters at break‐off for the pulsed wire follow normal distribution. The waiting period is much longer and more fluctuating in nature. A slight increase in bubble emission frequency was also observed for pulsating wire.
High‐Pressure vapor‐liquid equilibria in ammonia‐water‐nitrogen‐hydrogen system
Authors: Guerreri Gianfranco 
Published: June 2004

AbstractThe results of ideal and nonideal vapor‐liquid equilibria of ammonia‐water‐nitrogen‐hydrogen, a system of industrial importance, have been examined. Redlich‐Kwong equation of state and the Gompertz equation have been used to determine the fugacities and activity coefficients in the vapor and liquid phases, respectively. The standard fugacity in the liquid phase is found by integrating the fundamental thermodynamic equation by using the Gamson‐Watson expression.A trial and error procedure for the determination of a nonideal equilibrium system has been suggested. A comparison has been made between the available experimental values and the calculated ones. The importance of the use of fugacities which include deviations from ideality in calculating thermodynamic equilibria has been pointed out.
Pyrolysis of propane in a shock tube
Authors: Benson A. M. 
Published: June 2004

AbstractThe pyrolysis of propane has been studied over the temperature range 830° to 1180°C. with a single‐pulse shock tube employed to effect rapid heating and quenching. Both the uncatalyzed decomposition and the decomposition catalyzed by hydrogen sulfide were studied. First‐order rate constants for the uncatalyzed reaction are in excellent agreement with published data obtained in nonisothermal, tubular reactors. The product distribution differs from that obtained in other studies. It is characterized by decomposition of propane via two routes at roughly equal rates, one route leading to propylene and hydrogen, the other to ethylene and methane or ethane. Propylene subsequently is converted, almost stoichiometrically, to ethylene and acetylene. Hydrogen sulfide accelerates the initial decomposition of propane, thus maintaining high propylene selectivity to high propane conversion. A free radical mechanism is used to explain the gross features of the pyrolysis.
Measurement of coalescence frequency in an agitated tank
Authors: Howarth W. J. 
Published: June 2004

AbstractA new method for measuring the frequency of coalescence of drops in an agitated tank is proposed. It makes use of the fact that the rate of establishment of a new steady state mean drop size following a reduction in agitation intensity is related to the coalescence frequency in the tank. This method allows independent examination of the effects of drop size and impeller speed on coalescence frequency, and has the advantage that, since the measurement is not dependent upon the addition of external substances, high degrees of purity can be maintained and the effect of trace additions to the dispersion observed. The results provide some support for the assumption of an inverse proportionality between coalescence frequency and drop size. For constant drop size, coalescence frequency was found to depend on impeller speed raised to the power of 1.3 to 1.65 and the volume fraction of dispersed phase to the power of 0.6. The magnitude of density difference between the phases and the operating temperature were found to affect coalescence frequency, although it is suspected that these two effects are interrelated. The addition of small quantities of simple electrolytes to the continuous phase was found to cause a marked reduction in coalescence frequency.
Polymer reactors and molecular weight distribution: Part I. Free radical polymerization in a continuous stirred‐tank reactor
Authors: Duerksen J. H. , Hamielec A. E. , Hodgins J. W. 
Published: June 2004

AbstractAn investigation was made of the simulation of bulk and solution polymerization of styrene in a continuous stirred‐tank reactor (CSTR). A theoretical model from the literature was used to predict conversion, molecular weight distribution (MWD), and molecular weight averages. The kinetic rate constants required to solve the model were also taken from the literature.Styrene polymerizations were done at steady state in a laboratory‐scale CSTR over a range of experimental conditions. The recently developed gel permeation chromatograph (GPC) was used to measure MWD and average molecular weights. Comparisons were made between the theoretically predicted and experimentally determined values.The effect of solvent was included in the theoretical model but further investigation is necessary before the effects of thermal polymerization, viscosity, and mixing can be included. Where the latter effects were not important, good agreement was obtained between theoretical and experimental values.
Permeation of vapors through polymers at low temperature and elevated pressures
Authors: Henley Ernest J. , Santos Marcos Luiz Dos 
Published: June 2004

AbstractThe permeation of propane, propylene, ethane, and ethylene through 0.0051‐cm. thick polyethylene films was measured at temperatures between 25° and −30°C. Plots ofPvs. 1/Tfor C3H8, C3H6, and C2H6were saucer shaped, the activation energies changing from positive (endothermic) to negative (exothermic) over a narrow temperature range. This change is attributed to a plasticization‐condensation phenomenon and a change in intermolecular potentials.
An improved version of the rate equation for molecular diffusion in a dispersed phase
Authors: Jury Stanley H. 
Published: June 2004

AbstractA frequency domain analysis of reversible molecular diffusion in a granule or relatively stagnant drop of fluid reveals that for the larger values of time the rate equation reduces to

Compared with an earlier time domain result

the rate predicted is 15/π2 = 1.516 greater and this has been confirmed by results of experiment. An analysis of time constants shows that the dimensionless group relation

defines mathematically that which is meant by the larger value of time limitation.
Dirichlet problems for laminar forced convection with heat sources and viscous dissipation in regular polygonal ducts
Authors: Cheng K. C. 
Published: June 2004

AbstractThe effects of viscous dissipation on fully developed laminar forced convection with heat sources in various regular polygonal ducts under the thermal boundary conditions of uniform wall heat transfer per unit duct length and circumferentially uniform wall temperature are approached by the method of point matching. The method uses the exact solutions to the governing partial differential equations and satisfies the boundary conditions exactly only at selected points. This method complements the method of complex variables for various noncircular geometrical configurations where the velocity and temperature fields are not deducible directly from the boundary equations. The relationship between the average velocity and the average of (gradu)2over the cross section is pointed out. Other useful relationships between heat transfer quantities based on analogy or the observation of the results from literature and present investigation are also pointed out. The numerical results presented can be used to evaluate the effects of viscous dissipation on mean temperature, overall heat transfer rate at the boundary, heat transfer coefficient and Nusselt number. Graphical results for the representative cases are also presented for the heat transfer rate and the Nusselt number.
Separation of gas mixtures in free jets
Authors: Anderson James B. 
Published: June 2004

AbstractSpatial distributions of species flux in axisymmetric free jets of helium‐argon mixtures were determined experimentally. The experiments encompass the transition range between inviscid and free molecular flow at the exits of the nozzles forming the jets. Comparison is made with existing theories of separation. The results confirm the validity of Sherman's predictions and Rothe's measurements of diffusive separation for nearly inviscid flow. In the transition range departures from the nearly inviscid theory occur. The maximum degree of separation is observed in this range.
Stability of naturally bounded nonlinear systems
Authors: Maurer Charles J. , Garlid Kermit L. 
Published: June 2004

AbstractLiapunov's direct method is used to obtain regions of asymptotic stability for nonlinear systems with natural boundaries. In some cases this leads to larger stable regions of interest than if the bounds had been neglected. With account taken of the natural boundaries, a design method is formulated to find controller gains that give stable responses for anticipated disturbances. To compare the stability effects of different controllers and their gains, the change in the shape of the Liapunov function must be considered as well as the change in size of the region in which its time derivative is negative definite. Neglect of changes in the shape of the Liapunov function has led to misleading conclusions in previous work.
Multiphase viscoelastic flow through porous media
Authors: Slattery John C. 
Published: June 2004

AbstractLocal volume averaging of the equations of continuity and of motion over each phase in a porous medium is discussed. For a Noll simple material, inertial effects may be neglected with respect to viscous effects as the product of a Reynolds number with a Weissenberg number goes to zero (in the limit of a Newtonian fluid, inertial effects may be neglected as the Reynolds number goes to zero). When inertial effects can be neglected, a resistance transformation for each phase is introduced which in part maps the local volume‐averaged velocity vector into the local force per unit volume which that phase exerts on the pore walls and the moving phase interfaces. Capillary pressure is defined through a local surface average of the jump balance for momentum. The shape of the curve denoting capillary pressure as a function of saturation in a two‐phase flow may vary with the contact angle. For an isotropic multiphase flow of incompressible materials, the functional dependence of the resistance coefficient for a Noll simple material and for a Newtonian fluid is discussed by means of the Buckingham‐Pi theorem.
A mathematical model of a packed‐bed heat‐exchanger reactor for Dehydrogenation of Methylcyclohexane: Comparison of predictions with experimental results
Authors: Hawthorn R. D. , Ackerman G. H. , Nixon A. C. 
Published: June 2004

AbstractThe selective, highly endothermic reaction of methylcyclohexane to toluene and hydrogen was studied experimentally over a commercial Pt/Al2O3 catalyst, in an electrically heated tube serving as a packed‐bed reactor heat exchanger. The constant‐flux reactor, with measurement of temperatures within the bed at points intermediate along its length, proved well suited as an integral reactor for providing information on the reaction rate. A simple analytical model of the reactor was developed, and some of the data were used with the model to derive a rate expression.The model gives a good representation of radial variation of temperature in the packed bed. In the region of high Reynolds numbers investigated, radial transport of enthalpy is described in the model by a film resistance at the tube wall defined by heat transfer coefficient, and a diffusive transport through the packing, dominated by eddy diffusion.
Direct contact heat transfer between immiscible liquids in turbulent pipe flow
Authors: Porter J. Winston , Goren Simon L. , Wilke Charles R. 
Published: June 2004

AbstractThis paper reports on an experimental study of the direct contact heat transfer between oil and water in turbulent pipe flow under nonboiling conditions. Data were taken by a new technique, namely, monitoring on a very fast response recorder the output of a small thermocouple placed in the two‐phase flow. The variables studied were the liquid velocity, the pipe diameter, the water volume fraction, and, to a lesser degree, the interfacial tension and the oil viscosity. A successful semiempirical method of correlating the data is also presented.
Mechanism of interfacial mass transfer in membrane transport
Authors: Kaufmann Thomas G. , Leonard Edward F. 
Published: June 2004

AbstractDialysis of binary aqueous solutions of several sugars through a cellophane membrane was studied in a stirred batch dialyzer. Sherwood numbers describing mass transfer resistance in the fluid adjacent to the membrane were determined as a function of the corresponding Reynolds and Schmidt numbers. The results establish a reproducible environment for membrane testing in which a known controllable and small interfacial resistance is placed in series with that of the membrane. The results are also shown to support, for this geometry, the postulation of a third power relationship between eddy diffusivity and dimensionless distance from the phase boundary as well as the Sherwood‐Ryan nondimensionalization of this distance.
Catalytic dehydrogenation of cyclohexane: A transport controlled model
Authors: Graham R. R. , Vidaurri F. C. , Gully A. J. 
Published: June 2004

AbstractExperimental data and a mathematical model for the dehydrogenation of cyclohexane on a platinum‐on‐alumina catalyst in the presence of excess hydrogen are presented. Differential rate data were obtained by using a fixed bed flow reactor over a temperature range of 400° to 500°C., and a pressure range of 21.3 to 41.8 atm. at modified Reynold's numbers of 20 to 65. Cyclohexane concentration was varied from 16 to 25 mole %. In the development of the basic model, complete transport control of the overall reaction rate with equilibrium at the fluid external surface interface is assumed. The average deviation between experimentally determined and basic model calculated rates was 5.65%.Modification of the model by replacing the equilibrium assumption by a crude surface rate expression resulted in a reduction in average deviation to 4.3% and the maximum deviation was reduced from 22 to 12%.
Local and average interphase heat transfer coefficients in a randomly packed bed of spheres
Authors: Gillespie Bernard M. , Crandall Edward D. , Carberry James J. 
Published: June 2004

AbstractLocal and average heat transfer coefficients have been measured for a sphere in a randomly packed bed. A steady state technique was employed in which internally heated spheres were placed in a bed 35 in. deep and 12 in. sq. Air passed through the bed in downflow, the range of Reynolds numbers being from 120 to 1,700 based on the sphere diameter and the superficial velocity.Average heat transfer coefficients have been measured at twenty‐five positions permitting the assessment of the effect of position. An entrance region limited to the first two particle layers in the bed has been verified.Distributions of the local heat transfer coefficient on the surface of a single sphere in the top layer and in the nineteenth layer of the bed have also been measured. These distributions indicate that a laminar boundary layer exists over portions of the sphere surface.
Response of a tubular heterogeneous catalytic reactor to a step increase in flow rate
Authors: Lehr Carl G. , Yurchak Sergei , Kabel Robert L. 
Published: June 2004

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

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

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