摘要:

AbstractTwo experimentally determined sets of impeller boundary conditions were used to simulate the flow generated by a pitched blade turbine in a cylindrical baffled tank. Use of these two sets of boundary conditions in simulations with two different off bottom clearances led to the conclusion that the flow generated by a pitched blade impeller cannot be successfully predicted without considering the impeller location. Correct prediction of velocity fields in the tank required the correct specification of velocity boundary conditions. Successful prediction of the turbulent energy distribution required proper specification of the turbulence boundary conditions. There was almost no interaction between the velocity and turbulence fields. The turbulet kinetic energy dissipation rate was at a maximum close to the impeller in both geometries. Within this region the average dissipation rate was five and a half times greater that the average dissipation rate in the tank.

ISSN:0008-4034    

DOI:10.1002/cjce.5450720201

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper deals with mixing in stirred tank reactors by paddle agitators and two‐blade impellers with different blade widths. Computational Fluid Dynamics (CFD) is used to solve the 3D hydrodynamics and to obtain at every point the flow patterns, the stress components and the viscous dissipation function. From the latter information, the power consumption is calculated. These results are compared with available experimental data: good agreement is observed. For example, for a paddle agitator, the flow is essentially plane far away from the horizontal walls. That means that, in order to create an axial circulation in the volume of the tank, the impeller height has to be decreased.This work documents the ability of CFD to model changes in flow patterns for three dimensional flows in stirred tank

ISSN:0008-4034    

DOI:10.1002/cjce.5450720202

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

年代:1994

数据来源: WILEY

摘要:

AbstractA correlation to the solution of the two‐phase dispersion model has been developed for gas‐solid fluidized bed reactors operating in the bubbling regime. An analytical solution was obtained for fractional gas conversion by using an exponential function to characterize the dense phase gas concentration profile. The coefficient of the exponential function was found to depend on gas axial dispersion and, in order to determine this parameter, a Peclet number correlation was developed. Model predicted gas conversions were in excellent agreement with experimental conversions for a variety of fluidized bed reaction data over a conversion range from 2.5 to

ISSN:0008-4034    

DOI:10.1002/cjce.5450720203

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

年代:1994

数据来源: WILEY

摘要:

AbstractAn obstacle in modeling aseptic processing of particulate foods is the lack of a reliable estimator for the drag force of the non‐Newtonian liquid phase on the suspended particles as they flow through the holding tubes of such systems. The objective was to develop an expression for the drag force on cubic assemblies of spherical particles suspended in a pseudoplastic fluid flowing in a tube.An apparatus was assembled for direct measurement of the drag force exerted by solutions of sodium carboxymethyl cellulose (CMC) on the assemblies inside a tube. An empirical drag correction factor, as a function of particle volume fraction (applicable to Stokes' law), was develope

ISSN:0008-4034    

DOI:10.1002/cjce.5450720204

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

年代:1994

数据来源: WILEY

摘要:

AbstractExperimental data on the pressure drop across 1/2‐in. globe and gate valves in the horizontal plane for non‐Newtonian pseudoplastic fluids in laminar flow are presented. Generalized correlations in terms of the various physical and dynamic variables of the system have been developed for prediction of the frictional pressure drop for each valve. Statistical analysis of the correlations suggest that they are of acceptable accur

ISSN:0008-4034    

DOI:10.1002/cjce.5450720205

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

年代:1994

数据来源: WILEY

摘要:

AbstractChanges in the liquid hold‐up, ϵ, and the diameter ofd, of a foam that are induced by perforated plates (PPs) and the contribution of PPs to foam‐breaking were studied. A foaming system containing a dilute detergent solution in a column with mechanical agitation fitted with a rotating‐disk foam‐breaker (MFRD) was used. After the foam passed through the PPs, ϵ andddecreased and increased, respectively. The use of PPs to achieve a maximum reduction in ϵ and a maximum increase indis confirmed. It is also demonstrated that use of PPs contributes not only to improving the foam‐breaking performance of the MFRD, but also to p

ISSN:0008-4034    

DOI:10.1002/cjce.5450720206

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

年代:1994

数据来源: WILEY

摘要:

AbstractTwo ideal droplet length (l,) distributions have been derived for two different droplet shapes. The dispersed phase holdup (ϵd) increases with increasing dispersed phase velocity (Ud), but decreases with increasing continuous phase velocity, (Uc) in three‐phase fluidized beds. In the droplet‐coalescing flow regime,lvand the droplet rising velocity (vd) increase, but the spherical droplet fraction (k) decreases with increasingUdanduc. In the droplet‐disintegrating flow regime, the effects ofudandUconlvand k are insignificant, but vdincreases with increasing Uc. Maximum values oflv, occur in the bed containing 1.7 mm diameter particles andlvhas an uniform length of around 2.0 mm in beds with particle size larger than

ISSN:0008-4034    

DOI:10.1002/cjce.5450720207

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

年代:1994

数据来源: WILEY

摘要:

AbstractA fibre optic probe has been used to measure voidage profiles in the fountain, spout and annulus of spouted beds. The voidage in most of the annulus was found to be somewhat higher than the loose‐packed voidage and increased with increasing spouting gas flow rate, contrary to usual assumptions. There is a denser region in the annulus where the voidage was a little lower than the loose‐packed bed voidage. In the core of the fountain, the voidage decreased with height for low spouting gas flow rate, consistent with the model of Grace and Mathur (1978); however, at higher gas flow rate, it first increased with height and then decreased towards the fountain top. The radial profiles of local voidage were roughly parabolic in the lower portion of the spout and blunt in the upper port

ISSN:0008-4034    

DOI:10.1002/cjce.5450720208

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

年代:1994

数据来源: WILEY

摘要:

AbstractStudies have been carried out in multiple spouted beds having 2, 3 and 4 spout cells; different fluid inlet orifices and different solids have been used with air and water as spouting fluids. The minimum spouting velocities are measured for different bed depths. The experimental data for particle Reynolds number at minimum spouting have been correlated and the square root mean deviation between the calculated and experimental values is found to be 8.75 %.

ISSN:0008-4034    

DOI:10.1002/cjce.5450720209

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

年代:1994

数据来源: WILEY

摘要:

AbstractA residence time model for a rotating drum with lifting flights which includes axial displacement of airborne particles due to the drag of the gas stream has been developed in Part I of this study (Sherritt et al., 1993). Because the particles fall in curtains, the equations for single particle drag overestimated the effect of the gas stream on the displacement of the falling particles. In this paper, large scale wind tunnel experiments, which involved pouring a curtain of particles into a gas stream, indicated that the shielding effect of the curtain could be represented by a lower‐than‐average gas velocity within the curtain. The magnitude of the curtain shielding effect is related to the flight discharge rate, the fall distance and the flight length. Incorporating the results of the experiments into the residence time model provides a significant improvement on the effect of the gas velocity, and hence the best model available, especially for industrial‐scale equi

ISSN:0008-4034    

DOI:10.1002/cjce.5450720210

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

年代:1994

数据来源: WILEY