CFD simulation of heat transfer in a combustion chamber

Solid biomass represents the most important renewable energy source in the Republic of Serbia; however, its combustion in small-scale boilers is often associated with increased pollutant emissions. This study examines the influence of refractory elements on heat transfer in the combustion chamber of wood-log gasification boiler. These elements play a crucial role in multistage combustion systems, especially for moist biomass, by enhancing radiative and convective heat transfer, promoting more complete combustion, and reducing gaseous and particulate emissions while minimizing material usage. Special attention is given to the CFD optimization of the refractory ceramic length and the position of the producer gas inlet within the combustion chamber. Non-premixed combustion was modeled by solving the energy equation, applying the standard k-ε turbulence model and the DO radiation model. The results demonstrate that the most effective configuration employs a refractory element that creates a U-shaped flow path, which extends the residence time of flue gases in the chamber. Achieving this flow path requires the element to be at least one half to two thirds the length of the chamber, thereby positioning the combustion zone of the producer gas above the flue gas outlet.