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Author Borkink, J. G. H. ♦ Westerterp, K. R.
Source CiteSeerX
Content type Text
File Format PDF
Subject Domain (in DDC) Computer science, information & general works ♦ Data processing & computer science
Subject Keyword Velocity Profile ♦ Radial Porosity Profile ♦ Radial Porosity ♦ Model Fitting ♦ Heat Balance ♦ High Value ♦ Effective Heat Transport Coefficient ♦ Wall Effect ♦ Predicted Ntu ♦ Radial Superficial Velocity Profile ♦ Porosity Profile ♦ Low Tube-to-particle Diameter Ratio ♦ First-order Exothermic Reaction ♦ Predicted Temperature ♦ Two-region Model ♦ Radial Velocity Profile ♦ Exothermic First-order Chemical Reaction ♦ Effective Radial Heat Conductivity ♦ Effective Transport Coefficient ♦ Low Value ♦ Concentration Profile ♦ Literature Correlation ♦ Mass Balance ♦ Reynolds Number ♦ Abatmct-the Influence ♦ Wall-cooled Packed Bed ♦ Active Catalyst ♦ Cold-flow Experiment ♦ Convective Term ♦ Non-uniform Distribution ♦ Hot-spot Temperature
Abstract Abatmct-The influence 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. IN’I’BODUCTION
Educational Role Student ♦ Teacher
Age Range above 22 year
Educational Use Research
Education Level UG and PG ♦ Career/Technical Study
Publisher Date 1993-01-01