The Energy Budget in Suppressed Tunnel Fires

Measurements were undertaken during the course of medium-scale fire tests using stacks of wooden (80%) and plastic (20%) pallets. This combination of combustibles was considered to be representative of HGV loads in Singapore. The fire heat release rates were estimated using the oxygen depletion calorimetry method, based on sensors installed within a smoke exhaust hood. A low-pressure deluge system with discharge density in the range of 8-12mm/min was used in the tests. Results from the medium-scale fire tests and also from full-scale fire tests suggest that the convective heat transfer rate is generally no more than 50% of the suppressed fire heat release rate. This finding may allow a reduction in the capacity of longitudinal ventilation systems for smoke control.