摘要:

AbstractA second order closure scheme is developed for the numerical prediction of isothermal, non‐reacting, mono‐dispersed, dilute gas‐particle turbulent shear flows. The model is based on the two‐equation (κ‐ϵ) turbulence model developed for calculating the analogous gas‐phase flows. Contrary to passive additives in a single phase flow, the particles will affect the turbulence structure of the continuous phase. Thus, the κ‐ϵ model has been modified to account for the presence of the dispersed particles. In particular, the particles increase the dissipation rate because of the relative velocity fluctuations between the two phases. New proposals for these added effects based on particle size and loading are added to these equations. The resulting model is used to compute the axisymmetric jet in its developing region. The calculated jet spreading rate, centre‐line velocity decay and entrainment rate are all in excellent agreement with published experimental data. Calculated turbulence quantities such as the kinetic energy and mean Reynolds shear stress are greatly reduced from their “clean jet” levels by the presence of the particles in good agreement with the avai

ISSN:0008-4034    

DOI:10.1002/cjce.5450630301

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

年代:1985

数据来源: WILEY

摘要:

AbstractPotential flow equations for the combined rectilinear flow and a source are used to model the discharge of a jet into a porous media such as the condition in a fixed bed before spouting occurs. The equations derived are compared with data obtained using a measurement technique developed for determining thesuperficialvelocity profile in a packed bed. This technique does not disturb the packing nor the actual flow field at the point where the data is required. The analytical results are also compared with the results of jet flow studies in the literature. In addition, by assuming ideal situations, an equation was derived for minimum spouting which closely resembles equations for predicting minimum spouting that are available in the literature.

ISSN:0008-4034    

DOI:10.1002/cjce.5450630302

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

年代:1985

数据来源: WILEY

摘要:

AbstractAn empirical expression for the prediction of dispersed phase hold‐up and slip velocity in droplet dispersions settling under gravity is presented. Analysis of 998 published experimental results for 29 liquid/liquid systems from 14 different data sources shows that the slip velocity of the drop swarm is given in terms of drop diameter and physical properties of the system by:\documentclass{article}\pagestyle{empty}\begin{document}$$ 4dg\Delta \rho \left({1 - \varepsilon} \right)/\left\{{3\rho _c V_s^2 \left({1 + 4.56\varepsilon ^{0.73}} \right)} \right\} = 0.53 + 24\mu _c /\left({dV_s \rho _c} \right) $$\end{document}Good agreement between experimental and predicted values of slip velocity is obtained over a wide range of hold‐up (0.01 to 0.76) and Reynolds number (0.16 to 31

ISSN:0008-4034    

DOI:10.1002/cjce.5450630303

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

年代:1985

数据来源: WILEY

摘要:

AbstractThis is the first part of a series of two papers to study the agglomeration phenomenon which causes destabilization of certain low and high temperature fluidized beds. A theoretical model is proposed to determine the conditions under which defluidization occurs in fluidized beds in which cohesion forces between granules arise due to the presence of sticky fluids and/or high temperatures. Such bonding mechanisms between particles as solid—liquid bridges, visco‐elastic flattening and high temperature sintering are considered. The theoretical model predicts breakup of aggregates in the bed due to forces generated by bubble motion. The theoretical results are compared with experimental measurements in Part II of the pa

ISSN:0008-4034    

DOI:10.1002/cjce.5450630304

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe limiting fluidization‐defluidization condition for fluidized beds of sticky particles has been studied experimentally in both low temperature beds in which defluidization occurs due to the presence of sticky fluids and in high temperature beds where agglomeration occurs due to sintering of the granules. The experimental results described herein as well as others taken from the literature are compared to the predictions of the theoretical model developed in Part I of this pape

ISSN:0008-4034    

DOI:10.1002/cjce.5450630305

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe effects of interaction between circulating or oscillating droplets on drop formation, terminal velocity, and the continuous phase mass transfer coefficient during free fall were studied. To examine the mass transfer coefficient during free fall both end effects were eliminated by subtracting the mass transferred in a short column from that transferred in a long column. A correlation for the prediction of drop volume based on the equations of Scheele and Meister (1968) for non‐jetting drops, and of Meister and Scheele (1969a, 1969b) for drops formed under jetting conditions, has been developed. The terminal velocity of the drops was enhanced by vertical interaction with adjacent drops at values ofL/dp<5. The continuous phase mass transfer coefficient for circulating drops was reduced due to vertical interaction atL/dp<10; however, for slightly oscillating drops it was not affected by vertical interaction over the range of 1.5

ISSN:0008-4034    

DOI:10.1002/cjce.5450630306

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

年代:1985

数据来源: WILEY

摘要:

AbstractA thermal analysis of the V‐trough solar concentrator for use in solar heating and cooling is presented. A compact analytical expression for estimating Solar Insolation received by a collector for any day with any sky conditions has been formulated. The estimated values are found to be very close to quantities recorded by solar radiation measuring instruments. The V‐trough concentrator was investigated experimentally and found to be more efficient than a flat plate collector. It provided temperatures higher than 90°C. It is thus more suitable to utilize in absorption refrigeration applicat

ISSN:0008-4034    

DOI:10.1002/cjce.5450630307

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe separation theory of horizontal thermal diffusion columns with external refluxes, which was developed by Halle and Jury, has been derived by use of an orthogonal expansion technique. Considerable improvement is obtained when the refluxes and feed position are carefully chosen. The present formulation can be extended to other conjugated Graetz problems in continuous‐contact countercurrent separation processes with refluxes at both end

ISSN:0008-4034    

DOI:10.1002/cjce.5450630308

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

年代:1985

数据来源: WILEY

摘要:

AbstractCombined heat and mass transfer characteristics of laminar free convection flow about a sphere are studied analytically. The analysis assumes negligible interfacial velocities due to mass diffusion as well as insignificant diffusion‐thermo and thermo‐diffusion effects. The surface of the sphere is assumed to be at a uniform temperature and a uniform concentration. Boundary layer equations for the system are solved for the specific cases of convective diffusion of water vapor and naphthalene into air by the local similarity and the local nonsimilarity approaches. Numerical results of the local Sherwood number, the local Nusselt number and local wall shear stress obtained from the local nonsimilarity solutions are reported in a tabular form and the local similarity results are displayed graphically. In the analysis the cases of aiding and opposing thermal and concentration buoyancy forces are considered. Cumulative mass flow rates along with the dimensionless representative profiles of temperature, concentration and tangential velocities are presented for various combinations of paramet

ISSN:0008-4034    

DOI:10.1002/cjce.5450630309

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

年代:1985

数据来源: WILEY

摘要:

AbstractA simple theoretical equation of intraparticle effective diffusivity

ISSN:0008-4034    

DOI:10.1002/cjce.5450630310

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

年代:1985

数据来源: WILEY