摘要:

AbstractExperimentally‐measured pressure‐drop data are compared with analytical predictions for laminar flow of non‐Newtonian fluids in circular conduits, under constant wall heat flux boundary condition. The non‐Newtonian pseudoplastic solutions used in this study were aqueous solutions of Methocel® (0.75% – 2% w/w) and Carbopol 934® (0.15% – 0.50%). The heated section was 0.792″ i.d. × 1″ o.d. × 112.87″ long brass tube with an additional length of 68″ acting as the entrance length. The analytical predicitions on pressure drop have been based on numerically computed or analytically‐postulated temperature profiles. The mean deviation of the predicted values from the experimental valu

ISSN:0008-4034    

DOI:10.1002/cjce.5450530601

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractThe behaviour of inclined slurry pipelines at shutdown was studied using different active lengths of pipe. The ultimate settled condition was found to depend on pipe slope in the same fashion as for much shorter pipes. Pressure changes observed at the bottom of the slope gave a good indication of the time scale of the settling/flow process. A preliminary interpretation of the process is provided by a model in which inertial forces, compressibility effects and axial variations of velocities are neglected.

ISSN:0008-4034    

DOI:10.1002/cjce.5450530602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractRadial liquid distribution was measured experimentally for cocurrent, two‐phase downflow in packed beds. The effects of bed length, water and air flow rates, and type of packing were determined. The experimental data were obtained in the gas‐continuous, transition and pulsing trickling‐flow regimes. For all finite air rates, the liquid velocity profiles were approximately flat with the maximum average velocity occurring at the center of the packed column. Increasing the air rate increased the center liquid velocity. The gas rate effect was more pronounced in shorter beds. At higher gas rates the liquid rate had less effect on the radial liquid distribution than at lower gas rates. Operation at higher liquid rates resulted in a flatter radial liquid veilocity profile. It was observed that the bed of pellets operated at high liquid rate and low gas rate was unstable. Increasing the bed height increased the stability of the system and a better liquid distribution was obtained. The effects of water flow rate, bed length, and packing type on the shape of the liquid velocity profiles were

ISSN:0008-4034    

DOI:10.1002/cjce.5450530603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractAn experimental study of the break‐up length of a circular section liquid jet subject to the combined action of a coaxial airstream and an electrostatic field is reported. A high speed photographic technique has been employed and the results have been correlated empirically by the following dimensionless equation:\documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{L_o}}{{d_t}} = K\left[{We_a^{\frac{3}{2}} + 3\frac{{W_{e_l}}}{{{\mathop{\rm Re}\nolimits}}}} \right]^{- 0.22} \left({\frac{{\varepsilon _0 E_a^2 d_l}}{{1000\sigma}}} \right)^{- 0.13} {\mathop{\rm Re}\nolimits} ^b $$\end{document}where “b” and “k” are functions of Reynol

ISSN:0008-4034    

DOI:10.1002/cjce.5450530604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractLiquid phase mixing induced by gas bubbles at low gas velocities was studied experimentally. An experimental technique based on the principle of spectrophotometry was developed and applied in the experimental work. Experimental evidence suggests that the mixing phenomenon can be described as a diffusive process characterized by an effective diffusivity which is found to be a linear function of superficial gas velocity.

ISSN:0008-4034    

DOI:10.1002/cjce.5450530605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractThe drop size distributions produced by the cocurrent flow of kerosene dispersed in water through a vertical column packed with spheres have been measured at different levels of flow rate, volume fraction dispersed phase, packing diameter and height of packed bed. The drop size measurements were made by isolating and photographing a portion of the dispersion as it emerged from the packing. The Sauter mean diameter is predicted by:\documentclass{article}\pagestyle{empty}\begin{document}$$ d_{32} = Cf\left(\phi \right)\varepsilon ^{-.4} \tau ^{-.2} d_p ^{.2} $$\end{document}whereCis a constant,f(ϕ) is the phase fraction effect, ∈ is the power input per unit volume, τ is the residence time anddpis the packing diame

ISSN:0008-4034    

DOI:10.1002/cjce.5450530606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractThe measurements of the integral physical quantities such as circulation, mixing and blending times for helical screw impellers with the draught tube are presented in this paper. The influence of shear‐thinning and elastic properties of the liquids on these quantities are analysed both experimentally and theoretically.The overall circulation was found to be independent of the shear‐thinning character of the liquid. The influence of elasticity is considered in the light of the existing knowledge on sonic simple flow situations. A relation which incorporates the geometry of the mixer and the rheological properties of the liquid is proposed.The mixing and blending time results are analysed and related to the hydrodynamics using the laminar mixing approach of Mohr and his co‐workers. Although the analysis is approximate, it provides a useful tool in explaining the effects of rheology. It also suggests a way to estimate the blending

ISSN:0008-4034    

DOI:10.1002/cjce.5450530607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractThe influence of pretreatment and adsorption conditions on the adsorption of oxygen and hydrogen on supported Pt and Rh catalysts has been studied. It has been found that reduction conditions (temperature and time) and subsequent out gassing conditions influence the amount of gas adsorbed. Oxygen and hydrogen uptakes measured in a static system were significantly different than those measured in a dynamic system. Reproducible adsorption uptakes can be obtained by careful control of pretreatment and adsorption conditions.

ISSN:0008-4034    

DOI:10.1002/cjce.5450530608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractStudies of the adsorption of35S labelled ethyl xanthate ion and of35S labelled diethyl dixanthogen show that both species are competitively chemisorbed to an approximately equal extent on a galena surface, but that ethyl xanthate ion is oxidised to a species which is physically adsorbed, while diethyl dixanthogen is reduced to ethyl xanthate ion which is partially desorbed. It is suggested that galena surfaces are sufficiently heterogenous that oxidative chemisorption and oxidation of ethyl xanthate ion can take place on the anodic parts of the surface while diethyl dixanthogen can be reductively chemisorbed or completely reduced on the cathodic areas.The relationship of these processes to the normal flotation of galena is discussed.

ISSN:0008-4034    

DOI:10.1002/cjce.5450530609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractThe present paper is a study of the interplay between kinetic parameters and different flow patterns and its effect on fractional conversions for second order reactions with arbitrary stoichiometry and arbitrary ratios between the initial concentrations of the reactants. The models studied are the normal, segregated and maximum‐mixed axial dispersion and tanks‐in‐series models. The calculations required have been performed with the aid of digital simulation and the results are presented in diagrams making possible the determination of the fractional conversion for ten different models.When plotted as a function of a reaction rate group the absolute value of the difference between the conversions for the normal and segregated models always attains its highest value for the limiting model represented by complete backmixing, while this difference is zero for the opposite limiting model, i.e. plug flow. In the case of maximum‐mixed and normal models this difference attains its highest value between plug flow and complete backmixing, but the exact value is dependent on other parameter values. The diagrams indicate that it is more important to choose the proper model for certain parameter combinations than for others: the maximum difference between the conversions for different models is about 8%; the lowest

ISSN:0008-4034    

DOI:10.1002/cjce.5450530610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY