Parametric Study of Heating Temperature Non-Uniformity at Porous Burner Outlet: Impacts of Volumetric Flow Rate, Equivalence Ratio, Surface Emissivity, and Thermal Conductivity

Radiant porous burners are favored in household and industrial applications for their high flexibility, minimal emissions, and excellent fuel adaptability. Enhancing heating temperature uniformity improves the heat transfer efficiency and heating quality. This work presents a two-dimensional numerical study on the non-uniformity of the heating temperature (i.e., solid temperature at the burner exit) in a cylindrical porous burner. The root mean square (RMS) of the heating temperature (Ts,rms) is used to quantify the non-uniformity. From the numerical results, the cylindrical porous burner exhibits a non-uniform heating temperature and a non-uniform mass flow rate of flue gas at the sub-outlets. The surface emissivity and equivalence ratio have minor effects on the Ts,rms. However, increasing the volumetric flow rate and solid temperature leads to a more uniform distribution of heating temperature. The Ts,rms decreases from 40 K to 4.4 K as the volumetric flow rate increases from 26.75 slm (standard liters per minute) to 87 slm at an equivalence ratio of 0.96 and emissivity of 0.85. Meanwhile, the results demonstrate that increasing the thermal conductivity of the porous shell improves the heating temperature uniformity. This study presents guidelines for enhancing the uniformity of heating temperature for the cylindrical porous burner.