A New Approach to Ventilation Measurements in Enclosure Fires

The application of Stereoscopic Particle Image Velocimetry (SPIV) is a new approach to quantifying the ventilation in enclosure fires. Stereoscopic PIV is a non-intrusive optical measurement technique which measures the displacement of tracer particles in a flow. The technique is completely independent of temperature and differential pressure measurements typically applied to quantify ventilation in enclosure fires. Stereoscopic PIV is capable of performing thousands of measurements over large planar regions and resolving the flow velocity into its three components, (vx,vy,vz). Using the International Organization for Standards (ISO) 9705 room and a natural gas burner to generate conditions similar to the developing stages of an enclosure fire, SPIV was applied to measure the complete velocity vector field of the flow of air supplied to the room through a doorway. Two separate SPIV configurations were performed to measure the particle displacements normal to the doorway plane. Very good agreement was achieved for the velocity results from the two SPIV configurations, therefore permitting greater confidence in the SPIV results. Conventional measurements of temperature and differential pressure were also performed in the doorway using bare bead thermocouples and bi-directional probes, respectively. This allowed for a comparison of bi-directional probe velocity measurements to an independent method of measuring flow velocity in real fire conditions. There was a wide range of discrepancy between the velocity inferred from the physical probe measurements and the velocity measured with SPIV. The results suggest that flow field characteristics play a significant role in interpreting the measurements from the bidirectional probes.