Predicting charring rate of woods exposed to time-increasing and constant heat fluxes

This paper describes an investigation of the charring of wood exposed to a time-increasing heat flux and constant heat fluxes by using a modified partial differential equation (PDE) model, whose calculated result is validated by experimental result under time-increasing heat fluxes. It is assumed that the base of the char layer can be defined by the temperature of 300 °C. The results have shown that the rate of increase of heat flux and the density of woods significantly affect the charring rate and the charring rate of woods under time-increasing heat fluxes is smaller than that exposed to a constant heat flux. Linear regression conducted on the predictions of charring depth with time as the dependent time-increasing was suitable for time-increasing heat fluxes, while power regression was more suitable for constant heat flux. A successful experiential expression, which describing the relationship among char rate of woods and the increasing rate of heat fluxes and density of wood, has been suggested under time-increasing heat fluxes.