Application of sensitivity analyses to condensed-phase pyrolysis modeling

In this study, sensitivity analyses are performed on a given pyrolysis model. An approach is presented, which involves complex-step differentiation, to compute the normalized first-order local sensitivity coefficients of relevant model outputs with respect to the inputs, i.e. the material properties. This approach is systematic and robust and provides sensitivity coefficients that are dynamic; that is, sensitivity values are given as a function of time for the entire pyrolysis process. In order to demonstrate the proposed methodology, the anaerobic thermal degradation of generic homogeneous materials (a semi-transparent non-charring material, simulating a thermoplastic, and an opaque charring material) exposed to heat flux levels leading to thermally thin and thermally thick material responses is considered. The dynamic sensitivities of mass loss rate and surface temperature are calculated and discussed. The information inferred from the sensitivity analyses presented herein can provide insights into the behavior of a given pyrolysis model and help reduce its complexity for specific applications.