Parameter evaluation and sensitivity for transient heat transfer in fixed beds

The dynamic response of a packed bed to a pulse of heat input has been studied to provide estimates of the axial dispersion coefficient, fluid-particle heat transfer coefficient, intraparticle thermal conductivity and particle heat capacity. Packings of spheres and cylinders of different material and size were investigated. The dynamic response found in experiment was compared with the dynamic response calculated for the same inlet perturbation by numerical analysis of the partial differential equations for the fluid-phase dispersion model including intraparticle conduction. The fluid-phase dispersion model was used in the analysis as unlike other models it has been subjected to statistical tests which showed its validity and its consistency over a wide range of experimental results. The method of analysis of beds of spheres was the Alternating Direction Implicit Method and it has been given in an earlier study. This method was then developed to the Alternating Phase Implicit-Explicit Method to enable its application to beds of cylinders. A Bayesian approach was followed in parameter estimations. In this approach prior information and information provided by the experimental run were combined to give mean posterior values of the four heat transfer parameters together with estimates of their accuracy. The Bayesian approach adopted in this study was also applied to resolve the parameter interaction which existed between the axial thermal dispersion and the heat transfer coefficient, two parameters which were found to be highly correlated.