A critical comparison between the wave model and the standard dispersion model

Iordanidis, AA; Annaland, van M Martin Sint; Kronberg, Alexandre E.; Kuipers, J.A.M.

doi:10.1016/s0009-2509(03)00151-9

Cited by 9 publications

(8 citation statements)

References 16 publications

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“…The relationship between the wave (relaxation) model and diffusion model of longitudinal dispersion accompanied by chemical reaction was discussed by Moshinskii ( Moshinskii, 2003 ). Also Iordanidis et al ( Iordanidis et al, 2003 ) critically compared the wave model and the standard dispersion model for various exothermic reactions and concluded that the main difference is in the description of energy transport; discrepancies are more significant for fast processes with steep temperature and concentration profiles along the reactor.…”

Section: Shortcoming Of Standard Dispersion Model (Sdm) and The Wave mentioning

confidence: 99%

Residence time distribution (RTD) revisited

Rodrigues

2021

Chemical Engineering Science

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Residence Time Distribution (RTD) theory is revisited and tracer technology discussed. The background of RTD following Danckwerts ideas is presented by introducing “distribution” functions for residence time, internal age and intensity function and how to experimentally obtain them with tracer techniques (curves C and F of Danckwerts). Compartment models to describe fluid flow in real reactors are reviewed and progressive modeling of chromatographic processes discussed in some detail. The shortcomings of Standard Dispersion Model (SDM) are addressed, the Taylor-Aris model discussed and the Wave Model of Westerterp’s group introduced. The contribution of Computational Fluid Dynamics (CFD) is highlighted to calculate RTD from momentum and mass transport equations and to access spatial age distribution and degree of mixing. Finally smart RTD and future challenges are discussed.

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Section: Shortcoming Of Standard Dispersion Model (Sdm) and The Wave mentioning

confidence: 99%

Residence time distribution (RTD) revisited

Rodrigues

2021

Chemical Engineering Science

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“…Some different approaches to this problem have included the cross-flow model, 24 the alternating flow model, 25 and the wave model, first put forward by Stewart 26 and more recently strongly championed by Kronberg and his colleagues. 27,28 The application of the wave model to fixed bed heat transfer was demonstrated by Kronberg and Westerterp 27 whose work showed that this model also results in parameters that must be determined from experimental data.…”

Section: Background To Velocity-based Modelsmentioning

confidence: 99%

“…In parallel with the problems associated with heat transfer modeling in packed tubes, several authors have expressed dissatisfaction with the standard dispersion model (SDM) which uses effective diffusion to represent axial and radial dispersion and has drawbacks including infinite speed of propagation and overestimation of back-mixing. Some different approaches to this problem have included the cross-flow model, the alternating flow model, and the wave model, first put forward by Stewart and more recently strongly championed by Kronberg and his colleagues. , The application of the wave model to fixed bed heat transfer was demonstrated by Kronberg and Westerterp whose work showed that this model also results in parameters that must be determined from experimental data.…”

Section: Background To Velocity-based Modelsmentioning

confidence: 99%

A New Approach to Fixed Bed Radial Heat Transfer Modeling Using Velocity Fields from Computational Fluid Dynamics Simulations

Behnam

Dixon

Nijemeisland

et al. 2013

Ind. Eng. Chem. Res.

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A new velocity-based approach to fixed bed radial heat transfer is presented. Axial and radial velocity components were averaged from detailed 3D computational fluid dynamics (CFD) fixed bed simulations of computer-generated beds of spheres and used to model radial thermal convection. The convection terms were coupled with a radially varying stagnant bed thermal conductivity in a 2D pseudocontinuum fixed-bed heat transfer model. The usual effective radial thermal conductivity k r and apparent wall heat transfer coefficient h w were not used, and there were no adjustable parameters. The radial and axial temperature variation predicted by the velocity-based model agreed well with the angular-averaged temperatures from the detailed 3D CFD simulations over the range 80 ≤ Re ≤ 1900 and for N = 3.96, 5.96, and 7.99.

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“…The kinetic equations used for this work are valid in a temperature range from 250°C to 400°C, an interval compatible with the reaction temperatures. Where as a general formulation: …”

Section: Feed Sectionmentioning

confidence: 99%

Risk-Based Decision Making for the Management of Change in Process Plants: Benefits of Integrating Probabilistic and Phenomenological Analysis

Demichela

Baldissone

Camuncoli

2017

Ind. Eng. Chem. Res.

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Management of changes in the work environment is recognized to be a fundamental part of the safety management, in particular for process plants. The approaches for change management usually entail a risk-based decision-making strategy, to verify if the modification of the process, equipment, or procedure can increase the prior level of risk. Usually the risk assessment in process plants is conducted through the quantitative risk assessment traditional techniques, based on consolidated techniques and widely accepted (as hazard and operability analysis, fault trees, etc.). However, they are static, hardly taking into account time-dependent events, and are carried out separately from the consequence analysis. In recent years, some dynamic risk assessment methodologies have been proposed, supported by process simulation. This paper shows an application of the methodology called integrated dynamic decision analysis, highlighting the benefits of integrating the logical-probabilistic modeling and the phenomenological behavior of a system for the risk-based decision making in case of plant modification. The case study refers to a production plant of formaldehyde, where the reactor cooling system, based on melted salts, had to be switched to a water-based system. With the new plant arrangement, the analysis of the risks in terms of extra management costs, showed a reduction in risks of about 83% for dangerous occurrences, against a risk of plant in emergency for low temperatures, affecting the productivity, increased by 16%. But, mostly important, the analysis allowed for the identification of the more critical sequences of events the system could undergo in terms of probabilities, consequences, and risk, returning an integrated model of the revamped system to be used for the process management, the training of operators, and the technological transfer within the organization.

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A critical comparison between the wave model and the standard dispersion model

Cited by 9 publications

References 16 publications

Residence time distribution (RTD) revisited

Residence time distribution (RTD) revisited

A New Approach to Fixed Bed Radial Heat Transfer Modeling Using Velocity Fields from Computational Fluid Dynamics Simulations

Risk-Based Decision Making for the Management of Change in Process Plants: Benefits of Integrating Probabilistic and Phenomenological Analysis

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