ISSN:0001-1541    

DOI:10.1002/aic.690160402

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractExperimental gas absorption studies for bubbles transported in turbulent pipe flow of water strongly indicate that liquid phase controlled mass transfer is due to surface renewal by turbulent eddies. Predictions of transport behavior from the conditions of turbulent flow cannot be made in support of this mechanism because no satisfactory theory of turbulent transport near a gas‐liquid interface is available. This work considers a model of the hydrodynamic behavior near the surface which provides a link between the observed mass transfer behavior and the state of the turbulent field.In this model, the very small scales of turbulent motion are considered to be controlling. These motions are idealized, and their flow and mass transfer behavior are solved analytically. The overall result for eddies of various sizes is related to the turbulent energy spectrum by using only the easily accessible parameter ϵ, the energy dissipation rate. This model gives quantitative agreement to within a factor of 2 for three widely different experimental situations including gas‐liquid and liquid‐solid interfaces. However, the predicted Reynolds number dependence is somewhat higher than the experimental result.The model attempts to clearly define the basic physical process at the interface. Therefore, it indicates the direction for further experimentation needed to clarify the basic relationship between the mass transfer rates in the liquid phase and the hydrodynamic behavior of the turbulent

ISSN:0001-1541    

DOI:10.1002/aic.690160403

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractTemperature and velocity measurements were carried out at the center of the test section of an 8‐in. I.D. cylindrical graphite chamber in a confined nitrogen jet issuing from a 40‐kw. D.C. plasma torch. The test section was located 10.5 in. below the torch nozzle, and temperatures and velocities up to 4,300°F. and 120 ft./sec. were obtained.The overall rates of heat transfer by forced convection were measured to water cooled circular and square cylinders in two orientations. Results indicated that, owing to the high level of turbulence of the jet, turbulent boundary layers prevailed in the low range of Reynolds numbers investigated. Correlations are presented in terms of the Nusselt, Reynolds, and Prandtl numbers, with the physical properties of the gas evaluated at the bulk tempera

ISSN:0001-1541    

DOI:10.1002/aic.690160404

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractA theoretical analysis of the laminar‐turbulent transition phenomenon is presented for the case of steady, isothermal, fully developed flow of Newtonian fluids in straight ducts of constant isosceles triangular cross section. As a result of this analysis, the simultaneous existence of macroscopically large stable regions of laminar and turbulent flow are predicted to occur during the transition phenomenon. The existence of this special type of flow field, which has not been previously predicted theoretically, is shown to be a consequence of the presence of an asymmetric shear stress distribution. The results of an experimental study are also presented. These data verify the predictions made by the theoretical analysi

ISSN:0001-1541    

DOI:10.1002/aic.690160405

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractThe inversion of sucrose by partially deactivated ion exchange resin catalysts has been studied in a fixed bed reactor under conditions where intraparticle diffusion of sucrose is slow. Results show that the reaction remains apparently first order for deactivated catalyst. Activity is directly related to hydrogen content of the resin and is also dependent on the nature of the ion used to poison the catalyst.

ISSN:0001-1541    

DOI:10.1002/aic.690160406

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractPredictive equations for terminal velocities of liquid drops in Newtonian and non‐Newtonian systems are reviewed. The wave theory analogy is extended to include liquid‐liquid systems. Experimental data obtained with seven different systems are presented. The agreement with predictive equations is satisfactory. Interface rigidity was observed in all the systems investiga

ISSN:0001-1541    

DOI:10.1002/aic.690160407

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

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

ISSN:0001-1541    

DOI:10.1002/aic.690160408

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

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

ISSN:0001-1541    

DOI:10.1002/aic.690160409

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractAn anisotropic porous media model has been suggested for fluid motion in fuel cell cavities and has been shown to be valid experimentally with an actual fuel cell plate. Analytical solutions for pressure, velocity, and stream function have been obtained for finite and for point sources and sinks in rectangular cavities. Constant purge time curves have been constructed.

ISSN:0001-1541    

DOI:10.1002/aic.690160410

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractApproximate expressions of velocity profile and drag coefficients have been obtained for viscous incompressible non‐Newtonian flow over a fluid sphere in the intermediate Reynolds number range.The equations of motion of both external and internal fluids are satisfied by using Galerkin's method. The internal fluid is assumed to be Newtonian, while the external is assumed to be non‐Newtonian and can be described by the power law model. Furthermore, the condition that the tangential stress is transmitted across the fluid‐fluid interface without diminution is also satisfied with Galerkin's condition.Comparisons are also made between the predicted results and the experimental data available in the literature. The possible reasons for the discrepancy are also disc

ISSN:0001-1541    

DOI:10.1002/aic.690160411

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY