Fire Safety Science Digital Archive

An integral model is presented for the heat-up and pyrolysis phases of the combustion of noncharring thermoplastic materials. The heat transfer within the material is calculated by a one dimensional transient heat conduction model. For each phase, the original partial differential equations are transformed into a set of two ordinary differential equations by assuming a known temperature profile throughout the solid and using a moment technique. The model is different from previous integral models, since instead of a linear or exponential temperature profile, a quadratic temperature profile is assumed within the solid. The model provides for a specified external radiant heat flux and heat losses, including re-radiation and convection. The accuracy of the integral model is evaluated by comparison of the results with analytical solutions, numerical simulations and experiments. Since the model is simple, and computationally cheap, it can be incorporated into computer fire codes where the available memory and CPU time are always serious limitations. Calculations presented here show that it is ideal for this task.