Modelling of surface combusting straw bales

摘要

This report describes a computer model for the calculation of the steady and non-steady behaviour of surface combusting straw bales. The mathematical formulation is one-dimensional and the flow of gas through the straw bales is described by means of Darcy's law for flow through a porous medium. The model treats important phenomena such as: Evaporation, condensation and diffusion of water, Pyrolysis of straw, Combustion of gas, Combustion of straw char. Thermal radiation, Heat conduction in the straw, Straw-gas heat transfer, The straw bale properties such as porosity, permeability and water content may vary with time and the location in the bale. Calculated results are compared to temperature profiles measured in straw bales undergoing surface combustion. It is concluded that the rise in straw bale temperature close to the burning surface as well as the temperature at the surface are predicted reasonably well.