Abstract Besides cooking applications, biomass contributes significantly to space heating applications in cold-affected areas. Although the fundamentals of combustion remain the same in both cooking and heating stoves, they differ substantially in their design and operations. In the present study, the available literature for biomass cookstoves and furnaces and existing combustion models have been leveraged to investigate the heating stove. A Computational Fluid Dynamics-based numerical model has been employed to study the biomass stove functioning and optimizing its design for better thermal performance through its top surface- the comal. The maximum and average temperatures on the comal surface and heat transfer from it have been computed for varying magnitudes of identified parameters, like the location and quantity of secondary air, a critical gap in the flow of combustion products, and the height of the combustion chamber. In general, maximizing the heat transfer from the comal surface has been the objective function, although some variations from it, too, have been mentioned. Cylindrical surfaces inside the combustion chamber mimic the wooden log surfaces with volatiles releasing in the normally outward direction. A turbulence-based model has been used to determine the reaction rates and only gaseous-phase combustion with intermediate CO formation has been used. Results show better performance when secondary air inlets are placed away from the primary combustion location and close to the comal surface with a primary-to-secondary air ratio of 90:10. The gap between the exit of the capture tunnel and the comal surface is a critical parameter as lowering this could result into the back pressure and could make exhaust of gases inside the room, whereas increasing this gap decreases the interaction of flames with the comal surface and result into less heat transfer to the ambiance. A gap of 25 mm has been found suitable; however, to accommodate the practical behavior of biomass stoves, a range for this gap could be prescribed as 25 - 55 mm based on the low slope of the heat transfer curve. The height of the combustion chamber has a slight effect on the thermal performance, and in general, decreasing the height of the chamber increases the temperature of the comal surface; however, this is subject to the practicality of the stove and the size availability of the wooden biomass.
Kaundal et al. (Tue,) studied this question.