Effect of porous media transparency on spherical and cylindrical filtrational combustion heaters performance

An influence of partial transparency of a porous media on radiative efficiency, maximum solid phase temperature and combustion localization radius of cylindrical and spherical filtration heater has been investigated by numerical modeling. It is shown that partial transmittance of radiation in amorphous quartz balls bed provides for 2–5% increase in heater radiative efficiency in comparison with opaque material of carcass. In conditions of elevated ambient temperatures (as in, e.g., thermal kilns etc.), the increase in efficiency is smaller. It is shown that the transparency of porous media may not only decrease but, unexpectedly, increase maximum solid temperatures in comparison with the opaque one, in the case of big system size and high flow rate. In the later case, superadiabatic temperature excess (50–150 K) can be obtained in a solid phase. Also, some models of porous media optical properties are discussed.