Full-field surface heat flux measurement using non-intrusive infrared thermography

• A method was developed to measure full-field surface heat flux from a fire.
• The method was validated against traditional heat flux measurement techniques.
• Effects of plate material on measurement precision were investigated.
• Measurement precision was found to be inversely proportional to resolution.

A method was developed to measure full-field, transient heat flux from a fire onto a surface using infrared (IR) thermography. This research investigated metal plates that were directly exposed to fire while the unexposed side temperature of the plate was measured using IR thermography. These temperatures were then used in a two-dimensional finite difference inverse heat transfer analysis to quantify the heat flux. The method was demonstrated through a series of experiments with direct fire exposures onto vertical and horizontal plates. Fires were produced using a propane sand burner and ranged from 20 to 100 kW. Point heat flux measurements were also measured using a Schmidt–Boelter heat flux gauge. It was found that heat fluxes obtained via IR thermography were within one standard deviation of those from the Schmidt–Boelter gauge. The effect of plate material was studied both numerically and experimentally for stainless steel and aluminum plates. It was found that although precision is affected by material, appropriate resolutions can be selected to obtain similar precision for both materials. Spatial and temporal resolution effects were also investigated and it was found that the precision of the heat flux measurement is inversely proportional to both spatial and temporal resolutions.