Effect of particle contact point treatment on the CFD simulation of the heat transfer in packed beds

Abstract

In recent years, computational fluid dynamic (CFD) simulation of fully resolved fixed beds has become a popular tool for getting deeper insight in local phenomena in packed beds. To get correct simulation results, special care has to be taken on how to treat particle/particle and particle/wall contact points.In this work a local contact point modification, the local bridges method is investigated to study its effect on the heat transfer in packed beds. Packings were created using the Discrete Element Method (DEM) software discrete Flow, and were modified to implement the bridges. Using Design of Simulation Experiments (DoSE) the influence of different parameters on the heat transfer was studied. The simulated heat transfer in packed beds, considering conduction as well as natural convection, is compared to measurements and well-established correlations. Based on the Design of Simulation Experiments, a model for the correction of the effective thermal conductivity of bridges, to reduce the simulation error as a function of particle diameter D, is suggested. The suggested correction was tested on spheres of different material and sizes to check its validity. Using this correction, the simulation error for the beds surface temperature could be reduced by 75 % in a representative example case.