Thermal analysis of a self-insulated type of radiant porous air heater using the spherical harmonics method

In this work, an advance type of air heater is developed and analysed using porous radiant burners (PRBs). This system operates on the basis of the energy conversion process between gas enthalpy and thermal radiation via porous media. In the five-layered structure, which is analysed in this work, there are five porous layers that are separated by four special quartz glass windows. The main layer operates as a PRB that generates a large amount of thermal radiative energy and in the other layers, the energy conversion process takes place between gas enthalpy and thermal radiation. In order to determine the thermal characteristics of a newly proposed porous air heater (PAH), the coupled energy equations for the gas flows and porous layers and the radiative transfer equation are solved numerically by an iterative method. The spherical harmonics approximation is used to obtain the thermal radiative heat flux distribution inside the solid matrices. Computational results show a very high efficiency for this type of PAH, in comparison with conventional ones.