A nonequilibrium thermal model for rapid heating and pyrolysis of organic composites

A nonequilibrium heat transfer model is developed to predict the through-thickness transient temperature variation in organic composites subjected to intensive heating. In addition to heat conduction, the model incorporates four important mechanisms: rate-dependent pyrolysis, pyrolysis byproduct outgassing, irradiance-dependent convection heat loss, and radiation heat loss. The heat conduction in the solid part is considered to be one-dimensional, and the compressible gas flow in the pyrolysis region is treated as two-dimensional. Both the shape of the gas flow channel and the gas addition velocity from the channel wall are evaluated based on the decomposition reaction rate. An iterative numerical procedure is formulated to solve the coupled heat transfer and gas flow equations. Numerical results, including the through-thickness temperature transients, the continually changing gas channel, and the pressure distribution in the decomposition gas are obtained and discussed.