A comprehensive CFD based model for domestic biomass heating systems

Abstract This paper presents the efforts toward a reliable baseline computational fluid dynamics (CFD) model for domestic biomass heating systems with a special emphasis on CO and CO 2 emissions. The model accounts for the different phases of biomass thermochemical conversion steps (drying, pyrolysis, gasification, gaseous combustion and char combustion). The conversion of biomass is described using a bed model approach which is considered to be an arrangement of three layers: drying layer, pyrolysis layer and char layer. The fuel release conditions are provided by these layers via a set of mixture fractions. Standard k-e model is employed for turbulence modelling. Turbulence – chemistry interactions are described by a pre-assumed PDF (Probability Density Function) – mixture fraction method. Radiation is accounted for by the DOM model (Discrete Ordinates Model). The model is developed in the framework of Code_Saturne (open source software). It is applied to analyze the design of a commercial wood log stove with a nominal thermal capacity of 10 kWt. Experiments have been also performed to provide data for model input and validation. The simulation results revealed a considerable potential for stove geometry optimization and emissions reduction. The CFD results can be taken as a guideline for an improved design with regards to emissions and efficiency.