Publications

Experimental-modeling approach for predicting radiation and conduction heat transfer through a uniform, highly-charring foam

Erickson, Kenneth L.; Celina, Mathias C.; Hogan, Roy E.; Nicolette, Vernon F.; Aubert, James H.

Polymer foam encapsulants provide mechanical, electrical, and thermal isolation in engineered systems. In fire environments, foams, such as polyurethanes and epoxies, can liquefy and flow during thermal decomposition, and evolved gases can cause pressurization and failure of sealed containers. In systems safety and hazard analyses, heat transfer and thermo-mechanical response in systems involving coupled foam decomposition, liquefaction, flow, and pressurization can be difficult to predict using numerical models. This is particularly true when liquefaction and flow create inhomogeneous "participating media" that behave inconsistently and significantly impact radiant heat transfer to encapsulated objects. To mitigate modeling issues resulting from foam liquefaction and flow, a hybrid polyurethane cyanate ester foam was developed that has mechanical properties similar to currently used polyurethane foams. The hybrid foam behaves predictably, does not liquefy, and forms approximately 50 percent by weight uniform char during decomposition in nitrogen. The char forms predictably and is a relatively uniform "participating medium." Experimental and modeling approaches were developed to predict radiation and conduction heat transfer to encapsulated objects before, during, and after foam decomposition. Model parameters were evaluated from independent small-scale experiments. Largerscale radiant heat transfer experiments involving encapsulated objects were done to provide data for model evaluation. Model predictions were within the variation in experimental results for the major portion of the experiments. © (2009) by BCC Research All rights reserved.