Temperatures of restricted turbulent fire plumes

A study has been made of the restricted plume flow above horizontal, fine mesh screens which intercept a small-scale, turbulent fire plume. Measurements were made of centerline temperatures in both restricted and free plumes, together with screen friction forces associated with restricted plumes. Counter to intuition, the restricted plume displayed higher time-averaged mean temperatures. A model based on the return of the flow of the restricted plume to the pre-screen (universal) Froude number has been developed to predict the increased time-averaged mean temperatures above the screen, i.e. lifting of the virtual point source, as a function of the plume/screen friction force. Assuming engineering velocity distributions, the theoretical model was confirmed experimentally for screen friction forces up to at least half the total plume momentum at screen level.