bluuebunny/crossref_metadata_2025 huggingface dataset:
Small scale tests for attrition resistance of solids in slurry systems
Authors: Bjorklund I. S. , Dygert J. C.
Published: June 2004

In many present day solids‐liquid contacting processes and slurry transport systems, the attrition rate of the solid particles is of primary technical and economic concern. Particle size degradation in a transport pipeline may make the delivered solids entirely unsatisfactory for the intended use, or separation of fines from the liquid phase and makeup of attrited solids may be so costly that an otherwise attractive process becomes unacceptable.

Pilot scale tests to measure attrition in a slurry system are often costly and very time consuming. For this reason small scale tests have been developed for screening candidate systems prior to pragmatic pipe‐loop or pilot‐plant tests. Two of these test methods, crushing tests on individual particles, and annulus flow in a rotating cup apparatus, appear to give useful data on the relative attrition resistance of various solids and to provide a basis for estimating the attrition rate to be expected in a flowing system.

Results obtained by using these test methods with silica gel in hexane and with molecular sieve particles in kerosene yielded some information as to the predominant mechanisms of attrition for these two types of solids. The brittle, glasslike silica gel appears to fail through impact fracture of small to medium size chips from the large particles, while attrition of molecular sieves results from surface abrasion, probably due to failure of the binder material, and yields only extremely fine products of attrition.

This paper, which is based on a rather limited amount of preliminary experimentation, has been prepared in the hope that it may stimulate additional work on the development of useful standardized procedures for evaluating attrition resistance of solids.
Role of concentration level of the nondiffusing species in turbulent gas phase mass transfer at ordinary mass transfer rates
Authors: Wasan Darshanlal T. , Wilke Charles R.
Published: June 2004

Numerical solutions to the diffusion‐convection equations are obtained with a digital computer to establish the role of concentration level of the nondiffusing species in nonequivolume diffusion in fully developed turbulent flow of gases in pipes. Results indicate that under ordinary mass transfer rates for a system at constant Schmidt and Reynolds numbers product of the gas‐phase mass transfer coefficient and the log mean partial pressure of the nondiffusing gas is nearly constant both in the mass transfer entry region and in the fully developed region. These results are compared with the experimental data on vaporization and absorption processes.

We show that the effect of the mass transfer section length on the rate of turbulent mass transfer is quite significant. Furthermore, the results of the diffusion—convection analysis are in better agreement with experimental data for sections of finite length than results calculated from the momentum‐mass transfer analogy. The two methods agree in the limit for tubes of infinite length.
A kinetic theory of catalysis and mass transfer in a cylinder
Authors: Shendalman L. H.
Published: June 2004

The diffusion and mass transfer of a trace component in a background gas in a cylinder, is treated according to a relaxation transport equation. The system is assumed isothermal and at rest. An expression for an effective axial diffusivity is found which goes to the appropriate high and low density limits. Numerically, this diffusivity is similar to one half of the harmonic mean of the high density diffusivities, which is often used as an empirical extrapolating formula.

The radial mass transfer problem results in an integral equation which is solved numerically for all Knudsen numbers.

The case of catalytic reaction on the walls is considered in detail. Rarefaction effects become important under conditions of fast reaction. The problem of sublimation or evaporation from a cylinder wall can be treated by the same equations.
Stability of adiabatic packed bed reactors. Effect of flow variations and coupling between the particles
Authors: Vanderveen John W. , Luss Dan , Amundson Neal R.
Published: June 2004

A simple cell model is used for the determination of necessary and sufficient conditions for the stability of an adiabatic fixed bed reactor. These conditions are stronger than those obtained by considering only a perturbation of a single particle. Because of the nonuniqueness of the steady state profiles certain pathological effects can occur when the flow rate of the reactant is changed. Geometric coupling between the particles and heat transfer by radiation give rise to further complexities. Examples are given in which the trends predicted by the models have been observed experimentally by Wicke and Frank‐Kamenetskii.
On the theoretical calculation of friction factors for laminar, transitional, and turbulent flow of newtonian fluids in pipes and between parallel plane walls
Authors: Hanks Richard W.
Published: June 2004

Various modifications of the Prandtl mixing‐length model for turbulent momentum transport in pipes and between parallel plane walls are discussed. The most complete modification, due to Gill and Scher, is improved by replacing one of their two empirical constants by a theoretically calculable parameter. The new theory is compared with experimental data from the literature and found to reproduce frictional resistance data accurately for all values of the Reynolds number. It is somewhat in error for velocity profiles at high Reynolds numbers, but accurately reproduces velocity profile data in the transition region. The new theory represents the first accurate semi‐theoretical calculation of frictional resistance coefficients for all regimes of flow (laminar, transitional, and turbulent) for both pipes and parallel plane ducts, and of velocity profiles in the transitional flow regime in either geometry.
Coupled energy and multicomponent mass transfer in dispersions and suspensions with residence time and size distributions
Authors: Gal‐or Benjamin , Padmanabhan Lakshminarasimha
Published: June 2004

An analytical solution for the transport equation is presented for the case of coupled energy and multicomponent mass transfer in an ensemble of spherical drops, bubbles or solid particles. The solution is used to evaluate the total interfacial transfer rates in a population with particle size and residence time distributions. Using matrix notation and appropriate transformations, the partial differential equations are solved for each phase by using an integral operator whose kernel is the residence time distribution for the flow system. The method of attack is illustrated by solving the transport equations for fine dispersions or suspensions with high hold‐up values and presence of adventitious surface active agents.
A comparison of theoretical and experimental results for the internal dissolution of soluble cylinders by water in Laminar flow
Authors: Straight Frank , Baasel W. D.
Published: June 2004

A boundary layer solution applicable to a certain general type of mass transfer operations was developed by Baasel and Smith (1). When the solution was adapted to the systems of condensation of a vapor from noncondensing gases and absorption of a gas into a wetted wall column, the temperature and interfacial area could not be completely controlled. To overcome these difficulties, the rate of internal dissolution of a hollow cylinder of benzoic acid was experimentally measured and compared to the theoretically predicted values.

The ratios of the predicted rates to the observed rates fell, with the exception of two runs out of twenty nine, between 0.622 and 1.303. It was therefore concluded that the finite difference techniques used to obtain a mathematical solution were valid. However, it was observed that the assumption of unidirectional diffusion was possibly not valid. It was concluded that for systems in which the ratio of the total molar density of the fluid to the saturation concentration of the material being transferred was large, in the approximate range of 700 to 2,700, the boundary layer approach corresponded to the Leveque approximation of the classical Graetz solution for heat transfer for fluids with a parabolic velocity distribution.
Nonuniform initiation of photoreactions. III. Reactant diffusion in single‐step reactions
Authors: Hill F. B. , Reiss N. , Shendalman L. H.
Published: June 2004

The influence of nonuniform initiation on conversion in single‐step photoreactions is examined theoretically. Reaction types studied include reaction following absorption by reactant and photosensitized reaction. The batch slab reactor and the laminar flow tubular reactor with outside radiation are considered. In the case of reaction following absorption by reactant in the batch slab reactor, nonuniform initiation is found to have no influence on conversion, whereas for the other combinations of reaction and reactor its presence requires the specification of diffusion as well as kinetic parameters in order to characterize the conversion history unequivocally. The characteristics of conversion histories in the presence of nonuniform initiation are determined, and the influence of nonuniform initiation on chemical measurements of radiation and on tubular reactor performance in the neighborhood of laminar‐turbulent flow transitions is discussed.
Hydroisomerization of normal pentane over a zeolite catalyst
Authors: Voorhies Alexis , Bryant Philip A.
Published: June 2004

The most active zeolite hydroisomerization catalyst found during the course of a series of screening experiments was palladium impregnated hydrogen mordenite. The high activity of hydrogen mordenite catalyst was also reported by research workers of the Shell Oil Company. (11) Typical conditions used in this study were 550°F., 450 lb./sq.in. gauge, 8 g. of n‐pentane fed /h./g. of catalyst, and a hydrogen/pentane molar ratio of 3.4.

Process variable studies have shown that neither gas toparticle mass transfer, intraparticle (macro‐pore) diffusion, nor the chemical reactions at the palladium sites are rate limiting. The data can be correlated by a mathematical model based on the assumptions that a first‐order, reversible isomerization reaction on the mordenite acidic sites is rate‐controlling, and the apparent rate constant is an Arrhenius function of thetemperature of the system.

The pressure dependency of the reaction rate constant is consistent with a dual‐site mechanism and Langmuir adsorption isotherms.
The nonsteady flow of fluids through expansible tubes
Authors: Sheppard Robert G. , Osburn James O.
Published: June 2004

A digital computer solution of the equations of fluid motion predicts the pressures in an expansible tube through which liquid is flowing.

To obtain a stable solution, it is necessary to assume that the rate of change of area with time is proportional to the rate of change of velocity with time. This assumption is shown to be a reasonable one.

Calculations for the rate of travel of pressure pulses are in good agreement with experimental results.
Free convective effects on stokes flow mass transfer
Authors: Pearson R. S. , Dickson P. F.
Published: June 2004

Free convective effects on forced convective mass transfer in the Stokes flow region were studied experimentally by using a single drop in a liquid‐liquid system.

Liquids used to form the drops were methyl acetate or 2‐ethoxyethyl acetate with distilled water as the continuous medium. Spherical drops were formed on the capillary tip of a 0.58 cm. O.D. capillary glass tube centered in a 2.5 cm. O.D. pyrex tubular flow cell.

Results are presented graphically as NSh vs. NPe, NSh vs. NRe, and NSh/NRa1/4 vs. NPe to show the variation of mass transfer with flow rate and free convection. The range of variables was 10 ≤ NPe ≤35,000; 0.1 ≤ NRe ≤ 30; 578 ≤ NSc ≤ 1,149; and 12.3 ≤ NGr ≤ 75.7.

Satisfactory comparisons were also made with other investigators' findings.

Results substantiate that at low flow rates (Reynolds number < 10, Peclet number < 1,000) free convective effects either reinforce or interfere with mass transfer. This interference takes place until flow becomes high enough to overcome interfering effects of free convection.
The pseudoparticulate expansion of screen‐packed gas‐fluidized beds
Authors: Capes C. E. , McIlhinney A. E.
Published: June 2004

A study has been made of the expansion characteristics of beds of uniformly sized spherical particles of lead, nickel, sand, glass, and plastic that have been fluidized with air, carbon dioxide, and helium in columns packed with open‐ended cylindrical screen packing. The addition of packing to a gas‐fluidized bed limits the bubble size, prevents slugging and allows beds of high aspect ratio to expand smoothly in a manner similar to the behavior of liquid‐fluidized beds. Moreover, much of the experimental data for gas‐fluidized screen‐packed beds have yielded straight lines on a Richardson‐Zaki type of plot, again similar to the expansion of liquid‐fluidized beds. The conditions necessary for this pseudoparticulate behavior in packed gas‐fluidized beds are discussed. A correlation, based on the analysis given by Richardson and Zaki for liquid‐fluidized beds, is proposed to relate bed porosity with gas velocity, density and viscosity, particle size and density, and bed diameter.
Calorimetric determination of the isothermal effect of pressure on the enthalpy of methane and two methane‐propane mixtures
Authors: Dillard D. D. , Edmister W. C. , Erbar J. H. , Robinson R. L.
Published: June 2004

By using an isothermal throttling calorimeter, built for recirculating vapor operation, the effects of pressure on the enthalpy of methane and two methane‐propane (93.9 and 86.2% methane) mixtures were measured. Pure methane was run at 150°F. and the two mixtures were studied at 90, 150, and 200°F. The pressures for these experiments were 500, 1,000, 1,500, and 2,000 lb./sq.in.abs.

The resulting data were compared with similar data from other sources for these same systems and conditions. Agreement is good with enthalpy values obtained from both experimental volumetric and Joule‐Thomson data.

Prediction methods for the isothermal pressure effect on the enthalpy are compared with these data. These methods demonstrate the reliability of the Redlich‐Kwong and Benedict‐Webb‐Rubin equations and Pitzer's corresponding states correlation for calculating isothermal enthalpy changes for these systems and conditions.
Bounding chemical reactor transients by estimation of growth or decay rates
Authors: Wang F. S. , Perlmutter D. D.
Published: June 2004

If the transient equations of a plug flow tubular reactor are transformed into a set of corresponding ordinary differential equations, stability information for the former may be obtained graphically from knowledge about the transients of the latter. The analysis presented in this paper combines this simplification with the definitions and theorems of Weiss and Infante to propose a method of direct computation whereby transient bounds may be found for this important class of distributed‐parameter chemical reactor systems.
A theory of laminar flow stability
Authors: Hanks Richard W.
Published: June 2004

The success enjoyed by a laminar flow stability parameter that I previously developed as a generalization of the critical Reynolds number of laminar turbulent transition has occasioned considerable interest in the phenomenological theory underlying the parameter. In this paper an analysis of laminar flow stability is presented which leads naturally to the parameter in a much different manner than originally proposed. The stability parameter is seen to represent the coupling ratio between the rate of change of angular momentum of a deforming fluid element and its rate of loss of momentum by frictional drag. At a certain critical value of this coupling ratio, the element becomes unstable to rotational disturbances. If such disturbances are present, the basic nonlinearity of the momentum transfer process guarantees rapid amplification and generation of a turbulent eddy. The consequnces of the theory are examined for two special fixed boundary classes of motion. The physical interpretation of the parameter is compared with conventional interpretations of the Reynolds number and found to be more fundamentally sound. The application of the theory to moving boundary flows, such as the Couette viscometer, is also discussed and an important physical difference is pointed out.
Mass transfer driving forces in packed and fluidized beds
Authors: Wilkins George S. , Thodos George
Published: June 2004

The evaporation of n‐decane into air from the surface of Celite particles, has been used for the establishment of mass transfer factors for both packed and fluidized bed systems. For these calculations log mean partial pressure differences were used. Actual concentration profiles of the transferable component were also experimentally measured by monitoring, at different bed heights, the concentration of n‐decane vapor present in air used as the carrier gas. This was made possible through the use of an extremely sensitive hydrocarbon analyzer. The resulting profiles were used to obtain, by graphical integration, the actual driving force prevailing for each run. A nearly one‐to‐one correspondence was found to exist between the actual driving force and the corresponding log‐mean value for both packed and fluidized bed runs.
Sensitivity of a class of distributed parameter control systems
Authors: Seinfeld John H.
Published: June 2004

A sensitivity matrix is defined as a measure of trajectory deviations to small parameter variations of both open and closed loop controlled nonlinear parabolic and first‐order hyperbolic systems. In general the parameters may enter through the system equations or the boundary conditions and may be time or spatially dependent. The introduction of a positive measure of the sensitivity, the norm of the sensitivity matrix, into the performance index is shown to be effective in limiting the trajectory deviations due to the parameter variations. The open and closed loop control of a double pipe heat exchanger is analyzed with the open loop problem solved by an approximate procedure. The sensitivity reformulation is successful in reducing trajectory sensitivity, however at the cost of decreased overall performance.
Surface rheological properties of foam stabilizers in nonaqueous liquids
Authors: Mannheimer R. J.
Published: June 2004

The rheological properties of foam stabilizers have been measured with an improved canal viscometer that provides absolute values of surface shear viscosity and yield strength. Studies conducted in room air confirmed previous reports of complex non‐Newtonian film properties for oil soluble surfactants at the air‐oil interface. Both shear and time dependent behavior were observed in which the apparent surface viscosity increased with decreasing rotational speed. Surface viscosities were low at all fresh interfaces but generally increased with the age of the surface over a period of several hours to several days. Experiments conducted in a controlled humidity environment have established that the phenomenon of aging in room air is due to adsorption of moisture from the gas by the surfactant film. Preliminary results indicate that the shear dependency of films in a high humidity environment can be approximated by a Bingham Plastic model which characterize their rheological behavior in terms of a Newtonian surface viscosity and yield value.
A theoretical study on diffusion in pulsating flow
Authors: Fagela‐Alabastro Estrella B. , Hellums J. D.
Published: June 2004

A theoretical study has been made on the effect of pulsations in the flow field on interphase mass transfer. The phenomenon is of interest in studies of the cardiovascular system as well as in traditional engineering applications. The physical situation studied corresponds to fully developed flow in a long conduit with a periodic pressure gradient. The mass transfer problem was solved analytically for low amplitude pulsations for the two limiting cases of very small and very large frequencies. In addition, several numerical solutions were developed in the intermediate region where the asymptotic solutions are least accurate. The solutions taken together give a good quantitative overall view of the phenomenon.

One of the most interesting and unexpected results is that at very low frequencies it is possible for a pulsatile flow to yield a lower interphase mass flux than a steady Poiseuille flow with the same velocity.
Stability of high dimensional nonlinear systems using Krasovskii's theorem
Authors: Berger Albert J. , Lapidus Leon
Published: June 2004

Liapunov's direct method is used to establish a finite region of asymptotic stability for nonlinear systems with an arbitrary number of state variables. The procedure is a geometric one in multidimensional space which uses the Fletcher‐Powell minimization technique to find the maximum time derivative of the Liapunov function on the closed Liapunov hypersurface. Three detailed examples are presented, the first being the classical 2‐variable CSTR with heat transfer and the third being a 32‐variable 16‐stage model of an adiabatic tubular reactor with axial diffusion.
Network rupture and the flow of concentrated polymer solutions
Authors: Tanner R. I.
Published: June 2004

Entanglement theories for polymer solutions resemble those developed for solid rubbers. These rubberlike theories are extremely successful qualitatively; they give a good indication of the type of response observed experimentally in concentrated solutions. Quantitatively the theories are not so useful; in general they predict constant viscosities in simple shearing motions and ever‐increasing tensile stress in steady elongational flow.

If it is supposed that the lifetime of the entanglements is limited partly by a maximum allowable strain magnitude, and that the network ruptures locally whenever this magnitude is exceeded, greatly improved quantitative predictions are observed. For polyisobutylene‐cetane solutions, where the critical strain magnitude appears to be about 3, excellent prediction of the steady shearing viscosity curve is available starting from the measured dynamical response to small sinusoidal strains and the critical strain magnitude. Normal stress effects are also well represented; in elongational flow the tensile stress shows a slight maximum. It thus appears that the notion of network rupture is useful in guiding the selection of continuum theories for polymer fluid description.
Effects of turbulence on the drag coefficients of spheres in a supercritical flow Ŕegime
Authors: Clamen Allen , Gauvin W. H.
Published: June 2004

Drag coefficients of aerodynamically smooth spheres varying in diameter from 0.0625 to 1.004 in. and in density from 0.195 to 7.80 g./cc. were obtained at acceleration rates ranging from 120 to −30 ft./sq.sec. The particles were subjected to relative turbulence intensities of 7 to 35% and to ratios of Eulerian macroscale to particle diameter of about 0.4 to 5.

Quantitative measurement of particle drag coefficients was made possible by the use of a new particle tracing technique which permits the resolution of time to the nearest tenth of a millisecond. The resulting data extend farther into the supercritical flow regime than any other measurements previously reported.

The variation in drag coefficient with Reynolds number indicates a continuous alteration in the flow pattern around a sphere in this region. The effect of turbulence is, essentially, to increase supercritical drag, although this effect was found to diminish with increasing Reynolds number. Possible mechanisms for the effects of Reynolds number and turbulence on the particle drag coefficient are suggested.
Experimental determinations of the molar heat and entropy of adsorption and the activity coefficient of the adsorbed phase for the methane‐ethane‐silica gel system
Authors: Masukawa Shigehiko , Kobayashi Riki
Published: June 2004

Calculations of the molar heat and entropy of adsorption for pure methane and pure ethane on silica gel at 25°C. show the heterogeneity of the adsorbent when plotted as functions of the spreading pressure. Plots are given for the activity coefficient of methane and ethane in the adsorbed phase based on experimental data for the entire range of compositions at 25°C. up to a maximum pressure of 1,400 lb./sq.in.abs. Similar results were obtained at 5, 15, and 35°C. The activity coefficients deviate from unity at intermediate compositions.
The fluid hydrates of methylene chloride and chloroform: Their phase equilibria and behavior as influenced by hexane
Authors: Tester J. W. , Wiegandt H. F.
Published: June 2004

Thermodynamic properties pertaining to phase equilibria in the binary‐fluid hydrate systems, methylene chloride‐water and chloroform‐water, and the ternary hydrate system, methylene chloride‐chloroform‐water, were measured. Total vapor pressure data were recorded as a function of temperature over a range of −3 to + 10°C. Quadruple locus measurements of the ternary four‐phase equilibrium, L1‐L2‐H‐G, and isobaric studies of the ternary system chloroform‐methylene chloride‐water, support the existence of a solid solution hydrate between methylene chloride and chloroform. The addition of the nonhydrate former, hexane, to the methylene chloride‐water system lowered the isobaric critical decomposition temperature of the hydrate.
Laminar velocity profiles in developing flows using a laser doppler technique
Authors: Berman Neil S. , Santos Valerio A.
Published: June 2004

A laser doppler flowmeter is used to obtain velocity profiles in circular glass tubes downstream from a plug composed of brass screens. The apparatus for measuring point velocities of particles suspended in a fluid is described. Measurements were made very close to the plug at Reynolds numbers of 16.5, 47, and 274, and the flow development followed down the tube. The results show that the entrance flow development is dependent on the inlet profile shape and the Reynolds number for Reynolds numbers below 300.

The flow development at Reynolds numbers less than 300 was considerably slower than that predicted by the boundary‐layer solution of the equations of motion starting with a flat profile.
Heat transfer from a cylinder in an air‐water spray flow stream
Authors: Mednick R. Lawrence , Colver C. Phillip
Published: June 2004

Forced convection heat transfer from vertical cylinders normal to an air‐water spray flow stream was measured over an air velocity range from 60 to 140 ft./sec. and a water spray density range from 0.03 to 0.50 lb.m/(min.) (sq. in.). Local heat transfer coefficients were determined at 15 deg. intervals around the circumference of both a 1.5 and a 1.0 in. diam. cylinder. It was found that the addition of 0.426 lb.m/(min.) (sq. in.) of water spray to a 133 ft./sec. air stream raised the stagnation point heat transfer coefficient from 45 to 1,650 B.t.u./(hr.) (sq. ft.) (°F.). Similar intensification was found for other angles around the cylinder circumference; however, the magnitude decreased with increasing distance from the stagnation point. Local heat transfer coefficients were normalized with respect to their corresponding stognation point values and plotted parametrically as a function of angle and air velocity. These profiles showed that the normalized heat transfer coefficients decreased with increasing air velocity at angles other than the stagnation point. Average cylinder heat transfer coefficients were calculated from the air‐water data and two correlations were obtained relating these coefficients to the air and the water spray Reynolds number.
A thermodynamic equation relating equilibrium vapor‐liquid compositions and enthalpy differences in isobaric multicomponent systems
Authors: Tao Luh C.
Published: June 2004

A rigorous and simple thermodynamic equation relating equilibrium vapor‐liquid compositions and the phase enthalpy differences for a binary, isobaric system is extended to multicomponent systems. An analysis is made to indicate the potential applications of computing the latent heat of vaporization directly from the isobaric vapor‐liquid equilibrum data and testing the consistency of phase composition and enthalpy data.
A simple solution for boundary layer flow of power law fluids past a semi‐infinite flat plate
Authors: Hsu Chen‐Chi
Published: June 2004

The steady, two‐dimensional, incompressible laminar boundary‐layer flow of power law fluids past a semi‐infinite flat plate is studied analytically by the method of series expansion and the method of steepest descent (Meksyn's method). The shear stress of the fluids considered is proportional to the nth power of the velocity gradient. The solution obtained is a series of gamma function with the coefficient being a function of the material constant, n. The first ten terms of the series solution are then considered for the sum to determine the velocity gradient at the plate, fηη(0). The results obtained for fηη(0) and the coefficient of skin friction are in excellent agreement with the numerical solutions available in the range of 0.1 ≤ n ≤ 2.5.
Newtonian jet stability: The role of air resistance
Authors: Fenn Robert W. , Middleman Stanley
Published: June 2004

The stability of high speed laminar Newtonian jets is studied as a function of ambient air pressure. For Weber numbers less than 5.3 (based on air density) air pressure has no effect on stability. Ambient viscosity, through the effect of shear stresses acting on the jet surface, gives rise to the maximum in the breakup curve. For large Weber numbers ambient pressure effects can alter, and eventually control, the appearance of the maximum.
The effects of internal mass transfer on the hydrogenation of benzene over nickel‐alumina catalyst
Authors: Jiracek Frantisek , Horak Josef , Pasek Josef
Published: June 2004

The influence of mass transfer on reaction kinetics, within the porous structure of a catalyst, was investigated during the hydrogenation of benzene. The temperature range for a nickel catalyst at atmospheric pressure was 99 to 160°C. The rate equation and the apparent activation energy on a cylindrical catalyst pellet (4.5 mm. in diameter and 5.5 mm. in height) and on the catalyst particles (0.5 to 0.63 mm. in diameter) were evaluated.

The effect of internal diffusion on the dependence of the reaction rate, on the temperature, and on the partial pressures of benzene and hydrogen was satisfactorily explained by means of theoretical relations. The values of the effective diffusion coefficient of benzene were compared by calculating the kinetic data and temperature difference in the cylindrical pellet.
Effects of transpiration and changing diameter on heat and mass transfer to spheres
Authors: Brian P. L. T. , Hales H. B.
Published: June 2004

Mass transfer to spheres suspended in an agitated liquid has been studied both experimentally and theoretically. Finite‐difference solutions are obtained for mass transfer from a sphere to a fluid flowing past it in steady viscous flow. The effects of a transpiration velocity at the surface of the sphere and of a continuously changing sphere diameter are included. A normalized presentation of these effects is quite insensitive to the bulk flow Peclet number. When these theoretical corrections for transpiring and shrinking spheres are applied to the mass transfer data for ice spheres that are melting in an agitated brine bath, the corrected mass transfer coefficients are brought into agreement with a generalized correlation published elsewhere. This agreement suggests that the theoretical results apply, with reasonable accuracy, to a shrinking and transpiring sphere that is suspended in a turbulent liquid.
Crystallization kinetics of pure and binary melts
Authors: Kirwan D. J. , Pigford R. L.
Published: June 2004

An absolute rate theory based on a plausible model of the activated state, was developed for the interfacial kinetics of crystal growth from the melt. Except for liquid metals the theory predicts the growth rates of pure materials within about an order of magnitude. A microinterferometric technique was employed to observe liquid compositions near the faces of crystals growing from binary melts. For the simple eutectic system composed of salol and thymol, the theory represents the composition and temperature dependence of the growth rate.
Mass and heat transfer relations in evaporation through porous membranes
Authors: Findley M. E. , Tanna V. V. , Rao Y. B. , Yeh C. L.
Published: June 2004

This study concerns rates of evaporation and mass transfer of water vapor from a heated salt solution through a water repellent porous membrane to a cooled water condensate. This transfer is a result of temperature differences and corresponding vapor pressure differences across the membrane. Three groups of experiments were carried out which indicate that the major factor influencing the rates of transfer is diffusion through a stagnant gas in the membrane pores. However, an equation considering film heat transfer coefficients, membrane thermal conductivity, and an empiricial correction based on temperature driving force appears to be necessary for representing all the data. The empirical correction appears to be related to internal condensation and possibly diffusion along surfaces.
Acetone photolysis: Kinetic studies in a flow reactor
Authors: Matsuura Takeshi , Cassano A. E. , Smith J. M.
Published: June 2004

The photodecomposition of acetone vapor was studied in a tubular flow, differential reactor at atmospheric pressure and from 82 to 112°C. The products included significant amounts of biacetyl along with carbon monoxide and ethane. A rate equation was developed from a sequence of elementary reactions believed to explain the photolysis of acetone. The effects of light intensity and acetone concentration, indicated in the derived rate equation, were confirmed by the data.

The rate is less than first‐order with respect to acetone, and this is believed to be due to reformation of stable acetone molecules by deactivation of CH3COCH3*.
Profiles of laser‐created cavities on metal surfaces
Authors: Deming John L. , Weber James H. , Tao Luh C.
Published: June 2004

Metal surfaces of titanium, aluminum, copper, lead, and zinc were irradiated by a 25 joules pulsed laser with an energy flux ranging from 106 to 108 cal./(sq.cm.) (sec.). The resulted cavities were sectioned, polished and measured to compare with the isotherms computed from several heat conduction models. Reasonable agreement was found between the experimental cavity diameters at the interface and those calculated from the disk source model. Also, a graphical correlation between the cavity depth and its interface diameter is presented.
Experimental and theoretical investigation of purification in a column crystallizer of material with impurities of the eutectic forming type
Authors: Albertins Rusins , Powers J. E.
Published: June 2004

A theoretical analysis of the operation of a Schildknecht type of column crystallizer is presented and simplified to three special cases. Experimental determinations were made of concentration profiles established during the purification of benzene with cyclohexane as impurity under steady state, batch conditions of operation. Benzene containing 34 to 500 ppm. cyclohexane was obtained by processing feed material with 5,000 to 30,000 ppm. cyclohexane. It was found that experimental data obtained under conditions of normal operation are well correlated by theoretical expressions if it is assumed that the crystals are not pure but contain cyclohexane at the level of 34 to 100 ppm. It was further established that the resistance to mass transfer between the liquid which adheres to the crystals and the wash liquid is negligible in comparison to backmixing effects as represented in the model by an eddy diffusion term. Smooth operation of the column was obtained at crystal rates below a limiting upper value and at oscillation frequencies above a lower limit.
Heat transfer and pressure drop for nitrogen flowing in tubes containing twisted tapes
Authors: Kidd George J.
Published: June 2004

Heat transfer and pressure‐drop studies were made on a series of electrically heated tubes containing full‐diameter, full‐length twisted tapes. The A nickel tubes had a nominal inside diameter of 0.4 in. (10.1 mm.) and a heated length of 12 in. (30.5 mm.). Nitrogen at 200 lb./sq.in. gauge (14.6 atm.) was the working fluid, and the tests covered the Reynolds number range from 20,000 to 200,000. Twist ratios, defined as the ratio of the tube length per 180 deg. twist to the tube diameter, were varied from 2.5 to 14. The effect of tube wall‐to‐gas temperature ratio was studied for values of up to 1.8 and the heat flux was varied from 104 to 105 B.t.u./hr. · sq.ft. (3 × 104 to 3 × 105 w./sq.m.).

The results were compared with the results of previous heat transfer and pressure‐drop studies and were generally found to be in good agreement. An empirical correlation was developed for the heat transfer results that accounts for the effects of twist ratio, wall‐to‐gas temperature ratio, and tube length and includes most of the previous single‐phase results.
A study of the effects of internal rib and channel geometry in rectangular channels. Part II. Heat transfer
Authors: Buonopane Ralph A. , Troupe Ralph A.
Published: June 2004

Heat transfer and pressure drop data were taken on commercial plate heat exchange equipment. Nusselt and Euler correlations were determined for each of the six commercial heat exchangers investigated. These correlations were combined to establish a single heat transfer‐pressure drop relationship for any plate type of heat exchanger channel.

The results of this investigation were tested by using the correlations developed in Part I of this series to predict pressure drop data for the commercial unit based on their channel geometries. These predicted pressure drops were then used with the results of this part of the series to predict and compare heat transfer data.

The correlations developed in this work allow one to determine the heat transfer characteristics in a ribbed rectangular channel from the pressure drop characteristics of the channel in question.
Radiative transfer, H. C. Hottel and A. F. Sarofim, McGraw‐Hill Book Company, New York, 1967. 52 pages
Authors: Eckert E. R. G.
Published: June 2004

No Abstracts.
Effect of liquid‐packing surface interaction on gas absorption and flooding in a packed column
Authors: Coughlin Robert W.
Published: June 2004

Gas absorption, pressure drop, liquid holdup, and loading behavior in a packed column have been investigated using packing materials almost geometrically identical but fabricated from three different materials (ceramics, Saran, and polyethylene). For the absorption of oxygen into sodium sulfite solution, observed values of the liquid‐side, composite, overall mass transfer coefficient, KLa, were about 25% larger for the ceramic packing than for the polymeric packings. It was also observed that liquid loading occurs more readily in the case of the polymeric packing materials and it appears that the usual type of correlation is inadequate for predicting loading when polymeric packings are employed. In the case of liquid operating holdup no differences were observed from packing to packing. These observations are discussed in terms of the nature of the interaction between liquid and packing surface and it is pointed out how these phenomena may be fundamentally different from those of previous investigations, which relied upon surface‐active agents added to the liquid.
Prediction of jet length in immiscible liquid systems
Authors: Meister Bernard J. , Scheele George F.
Published: June 2004

The stability theory is used to predict jet length from jet inception to disruption for injection of one Newtonian liquid into a second immiscible Newtonian liquid. Knowledge of the length is essential for predicting the size of drops formed from jets. At low velocities jet length is controlled by the amplification of symmetrical waves which travel at the interfacial velocity of the jet. At higher velocities an abrupt lengthening of the jet may occur as a result of drop merging, and the jet length is then controlled by the growth rate of sinuous waves which are strongly velocity dependent. Jet disruption results from a geometrical limitation on the maximum amplitude of the sinuous waves. Predictions show good quantitative agreement with experimental data for thirteen mutually saturated systems over a wide range of variables and qualitative agreement with limited experimental data on the effects of initial disturbance level and mass transfer.
Temperature profiles of molten flowing polymers in a heat exchanger
Authors: Forsyth T. H. , Murphy N. F.
Published: June 2004

The Graetz‐Nusselt problem for polymeric flow in a constant wall temperature tube was studied, using a temperature‐dependent power law rheological model and temperature dependent fluid properties. Theoretical results compare within 6% of experimental results. The fluid model predicts an experimentally observed temperature maxima at a reduced radius between 0.7 and 0.8 for cooling at low flow rates.
Viscosity measurements on carbon monoxide, nitrogen up to 900 atmospheres and correlation to mass diffusion
Authors: Chierici Gian Luigi , Paratella Alberto
Published: June 2004

No Abstracts.
Comparison of Lagrangian time correlations obtained from dispersion experiments and from space‐time correlation functions
Authors: Rodriguez J. M. , Patterson G. K.
Published: June 2004

No Abstracts.
The properties of gases and liquids, Second Edition, Robert C. Reid and Thomas K. Sherwood, McGraw‐Hill, New York(1966). 646 pages
Authors: Thodos George
Published: June 2004

No Abstracts.
Some general equations for reverse osmosis process design
Authors: Ohya Haruhiko , Sourirajan S.
Published: June 2004

A generalized approach to reverse osmosis process design is presented for solution‐membrane‐operating systems characterized by the dimensionless parameters γ, θ, and λ defined in terms of the pure water permeability constant A, solute transport parameter (DAM/Kδ), mass transfer coefficient k on the high pressure side of the membrane, and the properties of the solution. Analytical expressions are derived, in terms of dimensionless quantities, for the change of volume of solution, concentration of the bulk solution and that of the concentrated boundary solution on the high pressure side of the membrane, the change in the permeating velocity of solvent water through the membrane, solute separation, and the other related quantities, at any instance, as a function of concentration of the product solution on the atmospheric pressure side of the membrane, or time from the start of the operation for reverse osmosis systems specified by γ, θ, and λ. The equations are applicable to membranes for which (DAM/Kδ) is independent of solute concentration and feed flow rate, and for aqueous feed solutions whose molar density can be assumed constant and whose osmatic pressure is proportional to mole fraction. The equations are developed first for the case of batch‐by‐batch operation, and their applicability to the flow case is then indicated.
Laminar‐nonlaminar transition for non‐Newtonian flow in annuli
Authors: McEachern Donald W.
Published: June 2004

Experimental results on the laminar‐nonlaminar transition of aqueous solutions of hydroxyethyl cellulose in axial, isothermal flow in annuli are presented. For each polymer solution the end of the laminar regime is observed to occur at different flow rates at different axial distances from the entrance of the test section. For some polymer solutions in nonlaminar motion, the pressure gradient is not constant over the length of the test section.

These data on transition in annuli are compared with predictions made using Hanks' transition criterion where only viscous contributions are considered and where viscous effects are considered and elastic effects accounted for approximately. Predictions where both viscous and elastic properties of the fluids are considered are in fair agreement with experiments. Predictions using purely viscous theory are less accurate than the viscoelastic predictions.
Thermal instability of a horizontal layer of liquid with maximum density
Authors: Sun Zu‐Shung , Tien Chi , Yen Yin‐Chao
Published: June 2004

An investigation is carried out to determine the onset of convection of a horizontal layer of liquid subject to temperature of T1 and T2 at lower and upper surfaces, respectively. The liquid is assumed to possess a maximum density value at Tmax with Tmax between T1 and T2. The temperature‐density relationship within the temperature range |T1 — T2| can be expressed as ρ = ρmax [1 — γ1 (T — Tmax)2 — γ2 (T — Tmax)3].

Both rigid‐rigid and rigid‐free surface conditions were considered. The critical Rayleigh number defined in Equations (20) and (24) is found to be dependent upon two parameters.

Experimental observations on the onset of convection were made and compared with the theoretical results. The experimental work consists of the measurement of the melting rate of a block of ice with melting from both below and above. In all cases, excellent agreement between experimental and theoretical results were obtained.
Errata
Authors: Slattery John C. , Distefano G. Paul , Tao Luh C. , Stewart Warren E. , Mannheimer R. J.
Published: June 2004

No Abstracts.
An analytical investigation of the flow in the saturated zone of ice counterwashers
Authors: Barak Amitzur , Dagan Gedeon
Published: June 2004

The 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

This 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

A 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.