Numerical Modeling and Performance Analysis of a Biogas-Fueled Injera Baking Burner for Clean and Sustainable Cooking Applications Using COMSOL Multiphysics

Abstract

Traditional injera baking across Sub-Saharan Africa still relies on highly inefficient biomass cookstoves, causing severe thermal losses, high operating costs, indoor smoke exposure, and broader environmental and economic costs. Biogas offers a clean, renewable alternative, but achieving uniform radial temperature distribution across large-diameter clay baking pans (Mitad, D > 48 cm) remains a major technical challenge. To address this, a biogas-fueled, three-ring concentric burner system featuring two intersecting central channels for balanced biogas distribution and inward-inclined flame ports was developed and evaluated using a decoupled two-stage 3D multiphysics numerical model built in COMSOL Multiphysics. The model couples turbulent reactive flow (k-ε), Eddy-Dissipation combustion kinetics, surface-to-surface (P1) radiative transfer, conjugate heat transfer, and a transient moisture evaporation sub-model. Validation against experimental benchmarks confirmed strong predictive accuracy (MAE = 3.12°C, RMSE = 4.08°C, R² = 0.94, GCI = 0.24%). The optimized burner achieved an average pan surface temperature of 185.4°C, a peak of 212°C, and superior radial thermal uniformity (±8.5°C). Surface heat flux integration yielded an overall thermal efficiency of 61.2% ± 2.1% and a specific fuel consumption of 0.29 kg biogas/kg Injera a 28.0% ± 2.2% gain in net heat transfer efficiency and a 20.0% ± 1.8% reduction in baking time relative to traditional three-stone wood-burning stoves (8% efficiency), with peak moisture evaporation reaching 0.020 kg/m²s during the initial flash-off phase. These results show that multi-ring aerodynamic staging with controlled swirling flow overcomes the thermal non-uniformities limiting biogas injera stoves, offering a validated design tool for scaling clean cooking technologies across Sub-Saharan Africa in support of SDGs 3, 7, and 13.