The influence of large, cold objects on engulfing fire environments

Abstract

Appropriate thermal boundary conditions for analytical predictions of the thermal response of large, cold objects (such as nuclear spent-fuel shipping casks) engulfed in flames are not well understood. These objects have been shown experimentally to respond differently to engulfing flames than small calorimeters, and traditional scaling parameters are not successful in explaining these observed differences. One possible explanation is that a large, cold object interacts with and cools the surrounding flames, resulting in lower incident heat fluxes to the large object. A simple model is constructed to investigate this hypothesis. Results of calculations with the model indicate that such an interaction does occur and can significantly reduce incident heat fluxes to large objects. This implies that appropriate thermal boundary conditions for large, cold objects engulfed in flames are dependent on the size, shape, and thermal response of the object. 10 refs., 13 figs.