Evaluation of a new device for simultaneous measurement of heat flux and gas velocity in a diffusion flame

Abstract

This article examines potential use of a new device called multi-directional heat flux and velocity probe for simultaneous measurement of heat flux and flame speed in a diffusion flame. The probe consists of a thin-wall spherical shell with internal insulation to mitigate internal convection. Both pressure and temperature distributions around the sphere are used to indicate local velocity and heat flux. The multi-directional heat flux and velocity probe appears to be a more promising device than the bidirectional velocity probe in the sense that the sphere is a regular geometry with minimum flow separation and should lead to more predictable behavior. However, an outcome of this study is that the device must be used in conjunction with a fire code computational fluid dynamics model because the boundary layer is not isothermal so that the conventional pressure coefficient for a sphere leads to erroneous results.