Comparative evaluation of heat transfer correlations with different fluid property considerations for fixed-bed reactor modeling

Abstract

Catalytic fixed-bed reactors are well established and frequently used in the chemical industry. Full-scale catalytic fixed-bed reactors are commonly described via pseudo-homogeneous continuum models. The heat transfer is accounted for by correlations that have been predominately fitted under the assumption of constant fluid properties. As a result of chemical reactions taking place, the fluid composition and the temperature in the fixed-bed depend on the spatial position. The resulting system specific non-uniformity of the fluid properties should be taken into account during modeling. The effect of different approaches to consider the fluid properties in the bed on the predictive performance of selected heat transfer correlations is evaluated on a broad range of experimental heat transfer data obtained from the literature. Correlations from both the αw- and the λr(r)-heat transfer models were selected. Although the selected correlations have been fitted under the assumption of constant fluid properties, the predictive performance was improved for all correlations if radial and axial variations of the fluid properties were taken into account. The impact on the resulting temperature field is illustrated based on a case study. In addition, the predictive performances of the selected heat transfer correlations are compared to one another over a broad range of tube-to-particle diameter ratios and Reynolds numbers. A clear superiority of the λr(r)-correlation proposed by Winterberg et al. was identified.