Convective Heat Flow in Fires
Heat is released from a fire in several forms: radiation, conduction, and convection. It has been determined that convective heat transfer is most important in activating sprinklers.
Convective heat transfer involves heat transfer through a circulating medium, which, in the case of fire sprinklers, is the room air .The air heated by the fire rises in a plume entraining other room air as it rises When the plume hits the ceiling, it generally splits to produce a ceiling gas jet The thickness of this ceiling jet flow is approximately 5 to 12 percent of the height of the ceiling above the fire source, with the maximum temperature and velocity occurring 1 percent of the distance from the ceiling to the fire source. The heat-sensing elements of sprinklers within this ceiling jet are then heated by conduction of the heat from the air.
