摘要:

During the past three years we have developed a tentative cold bed hydrodynamic model for an idealized fluidized bed gasifier. The computer program calculates the pressure, the void fraction and the velocities for a single size solid and for a gas. The fluid bed never reaches a steady slate, but continually oscillates, as bubbles form, rise through the bed and collapse on top of the bed.

ISSN:0098-6445    

DOI:10.1080/00986448308940060

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Steady-state and time-dependent non-Newtonian properties of structurally complex systems, such as suspensions and foodstuffs, are simulated by the extension of a recently developed fluid model. This model accommodates the concept of structure variation induced by flow via a kinetic approach similar to the treatment of reversible chemical reactions. Purely viscous and viscoelastic responses are considered, entailing different equations for the computation of their contribution to the overall stress sustained by the systems. The model successfully describes pseudoplastic and thixotropic behavior, with or without yield stress.

ISSN:0098-6445    

DOI:10.1080/00986448308940061

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

For differential equations exhibiting steep gradients and large curvature of the solution, the arc-length transformation has been proposed. The transformed differential equations can be accurately represented by a small number of equally spaced mesh points. The transformation can be used both for initial and boundary value problems. This transformation proved to be useful for reactor, flame and combustion problems, calculation of dissipative structures and transient behavior of certain autocatalytic reactions. Three sample examples are solved.

ISSN:0098-6445    

DOI:10.1080/00986448308940062

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Equations of state are shown to be mathematically equivalent to conservation equations, when the distance-time plane is replaced by the pressure-temperature plane. The Clapeyron equation is consequently developed, as a “shock condition“, based on the discontinuity in molar volume between phases at equilibrium. An important application of this point of view is a systematic approach to the development of empirical equations of state. A two-stage process is suggested, each step requiring an empirical fit with only a single independent variable.

ISSN:0098-6445    

DOI:10.1080/00986448308940063

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A model is presented for the diffusional release of theophylline and albumin from ethylene-vinyl acetate based polymeric systems with dynamically changing porosity. The model may be used to predict values of tortuosity of certain types of controlled drug delivery polymeric systems if drug dissolution limitations are negligible. The values of the tortuosity factor calculated indicate that small constrictions between large pores play an important role in the solute release behavior from these samples.

ISSN:0098-6445    

DOI:10.1080/00986448308940064

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

It is confirmed experimentally that a “Diffusion controlled slow reaction model'“ explains very well the alkaline hydrolysis ofn-amyl acetate at constant inlerfacial area. Mass transfer coefficient obtained from the model agrees well with that obtained from pure mass transfer experiment. Mass transfer coefficient can be correlated against Reynolds number, Schmidt number and vessel dimensions. Effect of diluents and solutes can also be explained using the above model. From the extraction rate of H-amyl acetate dispersed in aqueous phase in an agitated vessel, the second order reaction rate constant for hydrolysis of the ester with alkali in aqueous phase is estimated based on the above model. The estimated value of second order reaction rate constant for H-amyl acetate is almost identical to that for iso-amyl acetate orn-butyl acetate.

ISSN:0098-6445    

DOI:10.1080/00986448308940065

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The periodic switching between two feed compositions to a gradientless reactor has been found to increase significantly the average reaction rate compared with steady stale operation. Another advantage of periodic feed switching, which has not been fully exploited in catalyst studies is in kinetic model discrimination where large variations can be forced into the predicted responses of several competitive models under consideralion. The elementary step model, with parameters determined from transient experiments, is used to simulate observed transients during forced periodic feed experiments. The model is found to fit the observed behaviour well, in contrast to Langmuir-Hinshelwood models which only prove adequate for steady state behaviour. Simulation studies coupled with experimental work help to clarify the role of adsorbed species during forced cycling.

ISSN:0098-6445    

DOI:10.1080/00986448308940066

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A hybrid modeling approach is proposed for modeling and identification of an uniformly sampled continuous process in a closed loop where noises exist. This approach combines the determination of an ARMAX model with the determination of a continuous model as an integrated modeling procedures. The resulted model is designated as the HM(n,m,s) model. By using this modeling approach, the identifiability of the HM(n,m,s) model will be regardless to the regulator that is being used in the closed loop. Besides, the HM(n,m,s) model provides more accurate dynamic information than those of the conventionally estimated ARMAX model, which may be quite misleading sometimes. A systematic modeling strategy is proposed to obtain an adequate low order model. Numerical examples that use the simulated data and the proposed HM(n,m,s) modeling approach are also given. The results of the examples reveal that the advantage of the HM(n,m,s) modeling approach is remarkable.

ISSN:0098-6445    

DOI:10.1080/00986448308940067

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The effect of suspension viscosity on power consumption in fully baffled stirred tanks is investigated phase solid-liquid two

ISSN:0098-6445    

DOI:10.1080/00986448308940068

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

ISSN:0098-6445    

DOI:10.1080/00986448308940069

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor