Numerical analysis of heat recuperation in micro-combustors using internal recirculation

[Display omitted] •Heat recirculation in micro-combustors is analyzed using CFD techniques.•Influence of a porous recirculation region in the radiation emission is evaluated.•Metal foams are used as porous media to increase the rate of heat transfer.•Radiation emission increase is more significant for high fuel inlet velocities.•An increase of up to 40% in the emission efficiency was achieved. Heat recuperation in micro-combustors used as a radiation source for micro-thermophotovoltaic devices is an important mechanism to increase system efficiency and improve flame stability. A novel combustor structure is proposed to improve the heat transfer from the combustion gases to the combustor outer wall using an internal recirculation region filled with porous media. Numerical results indicate that the temperature difference in the recirculation region can be reduced up to 10 times using metal foams as porous media, which significantly increase the outer wall temperature. Different porous media and recirculation positions were investigated and it was found that the average radiation emission efficiency, for different inlet velocities, can be increased up to 24% in comparison with combustors without recirculation and up to 18% in comparison with combustors with open-channel recirculation (no porous media). The performance improvement is more significant for higher inlet velocities, with increases up to 40%.