Oxidation

Marek, L. F.

doi:10.1021/ie50489a019

Cited by 1 publication

(1 citation statement)

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“…This criterion is independent of the reactor length, whereas computer calculations, e.g. of Carberry and Wendel [3], Marek and Hlavacek [4,51, who calculated axial temperature and conversion profiles for heterogeneous exothermic reactions in an adiabatic packed bed reactor, indicate that the significance of axial heat dispersion decreases with increas-ing bed length. Later, Mears [6] derived a criterion for neglecting the axial dispersion of heat in non-isothermal packed bed reactors, based on the inlet rate data, which does depend on reactor length.…”

Section: Significance Of Axial Heat Dispersion For the Description Ofmentioning

confidence: 97%

Significance of the radial porosity profile for the description of heat transport in wall-cooled packed beds

Borkink

Westerterp

1994

Chemical Engineering Science

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Abatmct-Theinfluence of a radial porosity and velocity profile on the predicted temperature and concentration profiles in wall-cooled packed beds is studied, with and without an exothermic first-order chemical reaction, on the basis of literature correlations for the effective transport coefficients. Furthermore, values for the effective heat transport coefficients are obtained from "cold-flow" experiments by means of model fitting, with and without taking the radial velocity profile into account. The radial porosity and velocity profiles are approximated by a step-function, which is referred to as the "two-region model". It is shown that the effective radial heat conductivity can be taken constant over the radius, despite the wall effect. Nevertheless, the influence of a radial superficial velocity profile can be significant through the convective term in the heat balance, especially for low tube-to-particle diameter ratios. The predicted NTU can increase the order of 20% for high values of the Reynolds number and up to 100% for low values. This is confirmed by the results obtained from the model fitting. In case of a first-order exothermic reaction, significantly higher values for the hot-spot temperatures are predicted, if a radial porosity and velocity profile is incorporated in the heat and mass balances. This is found to be mainly caused by the non-uniform distribution of active catalyst over the radius, due to the porosity profile.

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Section: Significance Of Axial Heat Dispersion For the Description Ofmentioning

confidence: 97%