Numerical investigation of extracted position characteristics in porous media with lean methane and air premixtures combustion

Hydrogen production through steam generated from low-grade fuel recovery is considered a prospective method. To maximize the energy recovery, the influence of the heat exchanger position on the heat extraction stability of lean methane-air premixtures combustion in a porous burner has been numerically explored. The extracted position coefficient (EPC) is defined and a heat extraction model is validated through the experimental findings. It is shown that extracted position has a significant influence on the temperature profile, heat transfer capacity, heat loss as well as heat recovery rate. When the EPC is lower than 0.18, the filtration burner shows worse stability with great heat loss, the heat transfer behavior of the heat exchange tubes is severely weakened and heat recovery efficiency is merely about 13%. The optimal heat recovery position is recommended in the EPC range of 0.36–0.55, which has shown excellent heat extraction performance and accelerated the process of acquiring a quasi-steady state. Within this EPC range, the fluctuation of outlet temperature difference can be stabilized within 0.2 K, which maximizes the heat flux of heat exchangers, and heat recovery efficiency of about 70%–89% recovered with a concentration of 0.4%–0.8%.