Comparative evaluation of heat conduction and radiation models for CFD simulation of heat transfer in packed beds

The existing major heat conduction and radiation models for packed bed of particles are reviewed and evaluated by comparing the predicted results with experimental data. For low-temperature condition, it is found that the Zehner-Bauer-Schlünder (ZBS) model is less sensitive to the effect of contact area and is thus recommended for the calculation of effective thermal conductivity of packed bed. For high-temperature condition, although numbers of models can be used to calculate the radiative heat transfer behavior in packed bed, the Breitbach and Barthels (B-B) correlation is the optimal method applicable for different particle diameters, emissivities and voidages. The results of CFD simulations using the identified optimal heat transfer models agree well with the thermal measurements by thermocouple in four coal pyrolysis fixed-bed reactors mounted with or without particularly designed internals.