Two dimensional temperature distributions in a ceiling jet generated by a finite line-source fire: An experimental study

Abstract

The temperature distributions of ceiling jets are fundamental characteristics in enclosure fire dynamics. It is also the basics in the designs of fire safety devices in buildings, like detection, sprinkler, smoke control and standard fire protection. However, the only exists equation is for the radial ceiling jet temperature profile induced by a point source. There are no studies on line source despite the fact that the non-axisymmetric sources are the more common fires in buildings. This paper, for the first time, investigates the temperature profiles in ceiling jet induced by a finite line-source fire plume impinging upon an unconfined ceiling. Experiments are carried out with a buoyant jet fire and a pool fire. The temperature profile under the ceiling was measured along with flow condition visualized by a laser sheet. It is found that the temperature profile is two-dimensional and decays slower in the y-direction (perpendicular to line source longer side) than that in the x-direction (parallel to line source longer side). The characteristic length scales for characterizing the temperature profiles in the two directions are then proposed on the basis of the dimensions of the plume impinging zone. An equation is derived to describe the two-dimensional temperature profile based on the characteristic length scales. The present study provides basic data and a new equation for temperature profiles of ceiling jet induced by finite line-sources for building fire science.