Numerical Model Investigating Heat and Mass Transfer of Wood During the Heating and Cooling Period of Fire

A numerical model was proposed to analyze the heat and mass transfer process of wood during the entire period of fire including heating and cooling periods. Conservation of enthalpy and mass were considered. Velocities of gas and liquid were calculated by Darcy’s law. The desorption and adsorption of liquid water, pyrolysis of volatile components, burning of combustible pyrolysis gas and glowing of char were considered. Shrinkage of solid and subsequent surface cracking were included in this model. The effect of increasing heat and mass transfer by crack were expressed by additional heat and mass fluxes. Temperature dependent physical properties were used. To verify the model, simulation was conducted and compared with results measured in fire resistance test of glue laminated timber (GLT) wall reported in reference. Temperature, moisture content and burnt-out/charring/coloring depth were compared with experimental results. Experimental and numerical results on temperature and moisture content are in good agreement during the entire experiment process, including heating and cooling period. Numerical result on charred front also in a reasonable agreement with measured value, but the colored depth was smaller than experimental value.