Simulation of fixed bed regenerative heat exchangers for flue gas heat recovery

Fixed-bed regenerators are used to provide high temperature process gases in the glass and steel industries, in power plants and in waste heat recovery systems. In all these situations the temperature levels require the regenerator packing to be made from the low thermal conductivity materials such as ceramic. Simulation of the operation of fixed bed heat exchangers must accommodate the heat transfer from the gas to the packing surface and the temperature distribution within the core of the ceramic spheres. Most of the mathematical models employed in theory and practice assume either that the internal thermal resistance to heat flow within the core is negligible, or that the resistance can be incorporated in a lumped convective heat transfer coefficient at the surface. This investigation considers both approaches in the analysis of the experimental data obtained for a regenerator packed with alumina balls. Unifying theory and practice in this way allows the influence of flow rate and periodicity of operation to be investigated free from the effect of misleading interactions. The difference between the effectiveness results is firstly due to the experimental errors in the parameter measurements and secondly due to the heat losses from the main bed which has not been taken into account in the mathematical model.