Combined Convection-Radiation Heat Transfer in a Surface Combustor-Heater

The paper presents a model to predict combined conduction-convection-radiation heat transfer in a porous bed from which heat is extracted by a coolant circulated in tubes embedded in the porous matrix. The two-dimensional model is based on first principles of mass, momentum and energy conservation. The flow is modeled using the Brinkman-Forchheimer modified Darcy's equations, and the differential approximation is used for radiative transfer in the porous bed. Energy balances are made on the solid and the gas separately. The model equations are solved numerically using the SIMPLER algorithm. The numerical results reported in the paper show that the opacity of the bed and the product of the heat transfer coefficient and the surface area per unit volume of the bed are important parameters which control the thermal performance of the system