Measurement of Magnitude and Direction of Hot Gas Flow in a Fire Compartment with a Five-Hole Probe

Abstract

This report investigates the adaptation of a five-hole probe for measuring the magnitude and direction of hot gas flow in a fire environment. The probe was calibrated and tested in a boundary layer wind tunnel in ambient conditions; it measured the yaw angle to three degrees and pitch to two degrees accuracy over a range of +/- 25 degrees and gave velocity readings within 6%. The probe was then used in a series of 22 full scale fire experiments with the aim of measuring the magnitude and direction of the plume of hot gases spilling out under the soffit of a doorway between two ISO rooms. The measurements were taken at ten positions along a 45-degree line perpendicularly to the plume. It was exposed to temperatures up to 365°C and velocities up to 3.5 m/s. The four variables during the experiments were the fire size, the location of the burner in the fire compartment, the angle of the door in the doorway between the compartments and the size of the front opening of the adjacent compartment. The results allowed a qualitative and quantitative description of the characteristics of the spill plume depending on the aforementioned variables. The probe reached its limitations with the door 40 degrees open due to severe misalignment of the probe with the flow. The scatter of the collected data increased when the front opening was constructed as a doorway and the probe was fully submerged the deep upper hot layer. It is concluded that the five-hole probe can be used in a fire environment to measure the magnitude and direction of hot gases provided it is roughly aligned with the flow. In more complex flow patterns the scatter of the data increases.