Abstract
This paper describes the unsteady prediction method for the ceiling jet in large building spaces. For the application to unsteady cases, the terms of time differential in the government equations and the one dimensional heat transfers in the ceiling were added to the Alpert's theory. Moreover some of the functions such as the friction force against the ceiling and the air entrainment rate were refined for improving of the accuracy and the coverage. By this model, the profiles of the velocities, the gas temperatures and the heights of the ceiling jet are computed as time sequential, considering the influence of the heat loss into the ceiling and the dilution by the air entrainment. The result of a prediction was compared against Alpert's and Heskestad's practical correlations and the basic performances were confirmed. In the final part of this paper, the comparison of the predictions by this model was performed against measurements in a case of fire experiment using a large building space for validation.
