Experimental Investigation into Penetration of a Weak Fire Plume into a Hot Upper Layer

A hot upper layer pre-established under the ceiling of a room in a house due to a solar load in the summer or room heating in the winter may cause problems for fire detection by ceiling-mounted smoke detectors. A weak plume from a smoldering fire may be pushed back down by the hot layer, and be unable to reach a ceiling-mounted detector. In this study, based on the physics of plume penetration into a hot upper layer, a model for the penetration height was developed as a function of the distance of an upper layer from a fire source and the temperatures of the upper layer and the plume axis. A series of experiments were conducted to validate the model and determine the value of the coefficient involved in the model. Also measurements were made of the heat of combustion of smoldering fire of Test Fire 3 (TF3) prescribed in ISO/TC21/SC3 N301(Draft) using a cone calorimeter to see if a well-established formula for plume temperature is still usable for predicting penetration of a weak plume. Based on these results, it was confirmed that plume penetration height can be estimated even if the plume originates from a small heat source such as smoldering fire.