Numerical Simulation of Enhanced Heat Transfer for Stirling Engines in Fluidized Bed Combustors

The work concerns the numerical simulation of the direct coupling between the Fluidized Bed Combustor (FBC) and the heat exchanger of a Stirling engine. However, several issues need to be considered. Here the proper coupling of the Stirling engine with the fluidized bed is analyzed to assess the effective heat exchange enhancement attainable by the proposed configuration. In order to simplify the problem, a 2D simulation has been set. With this approximation the tube bank of the hot side exchanger of the Stirling engine are represented by a envelope surface shown in red in figure 2. This approximation appears justified by the very close spacing of the present heater tubes in the inner part of their cylindrical disposition. The main aim of this simulation is to investigate the level of fluidization attainable along the depth of lateral immersion in the sand. The influence of various parameters on the heat transfer between the FBC and the Stirling exchanger, such as particle diameter, immersion depth and fluidization velocities, is investigated. The simulation of the FB is carried out according to a CFD multi-fluid model. The model is coded using the OpenFOAM libraries.