Minimum Safe Standoff Distance for Protection from Bushfire Radiation by Commercial Metal Meshes

摘要

For building constructions in bushfire-prone areas, the relevant Australian Standard (AS 3959-1999) recommends that potential building openings be protected against flying debris and burning embers using a metal mesh with an opening less than 1.8 mm. Although the metal mesh can reduce the radiant heat transfer, it can also create hot spots on the object it is intended to protect, particularly if the standoff distance between the mesh and the object is small. These hot spots may even have a higher temperature than the object temperature without metal mesh protection. In this paper, the performance of some commercial metal meshes is simulated and the minimum standoff distance needed to avoid hot spots on the surface of the object is determined. An approximate formula for the calculation of this minimum distance is proposed.