Steady State Ceiling Jet Behavior under an Unconfined Ceiling with Beams

Abstract

Smooth horizontal and sloped ceiling jets have been studied extensively. The characteristics of these jets, i.e., temperature and velocity profiles, have been defined previously, particularly for horizontal ceilings. The presence of beams and obstructions pose a real challenge for both modeling and detector placement procedures. The present paper reports temperature profiles of ceiling jets for horizontal beamed ceilings, within beamed spaces that do not contain the plume impingement point. Furthermore, these results apply to an unconfined ceiling corresponding to large spaces or long enclosures where the end walls are far away. The research results can be highly useful for prediction of temperature of ceiling jet flows for spaces with continuous beams or joists, but may also be useful for other types of obstructions such as long light fixtures as well as smoke curtains in high bay areas. The correlation developed for temperature distribution within the bays of the beamed ceiling is based on the beam depth to ceiling height and is referenced to the smooth ceiling correlation developed by Motevalli. All data has been obtained from scaled experiments for non-dimensional fire sizes ranging from 0.0024 to 0.035. This range corresponds to fires from 38 kW to 560 kW for a 3 m ceiling height.