A global model on temperature profile of buoyant ceiling gas flow in a channel with combining mass and heat loss due to ceiling extraction and longitudinal forced air flow

This paper investigates temperature profiles of buoyancy-driven gas flow (both upstream and downstream) beneath a channel ceiling with combining heat and mass loss due to ceiling extraction (right above the buoyancy source) and longitudinal forced air flow. Experiments are conducted in a large scale model channel with dimensions of 72 m (length) × 1.5 m (width) × 1.3 m (height). The gas temperature profiles beneath the channel ceiling are measured by K-type thermocouples. Computational Fluid Dynamics (CFD) Large Eddy Simulations (LES) are carried out correspondingly by Fire Dynamics Simulator (FDS). It is found that: (a) with ceiling extraction only, the gas temperature profiles along the ceiling are symmetrically similar for upstream and downstream; and both decay faster longitudinally with increase in ceiling mass extraction velocity; however (b) with both ceiling extraction and longitudinal forced air flow, the gas temperature decays faster upstream than that downstream. A global model is theoretically proposed to describe the gas temperature profiles in both upstream and downstream direction with combination of mass and heat loss due to ceiling extraction and longitudinal forced air flow. Its predictions are in good agreement with measured values and CFD simulation results.