Wildfire fuel heat transfer sensor

Energy exchange in the fire environment is highly influenced by the heterogeneous and dynamic coupling between the atmosphere, fire, and fuels. While it has long been known that radiation and convection are the dominant heat transfer mechanisms in wildfire spread, much is unknown about their relative contribution. This is largely due to significant challenges observing these processes in the extreme wildfire environment. We describe a low cost, easy to deploy, simple heat transfer sensor and associated model, which was developed to measure heat transfer in wildfire. The sensor consists of stainless steel thermocouple probes differing in emissivity and similar in geometry and size to fine fuel elements responsible for carrying fire. Field and laboratory tests indicate that stainless steel probes with 3.2 mm and 1.6 mm diameters alone are not able to resolve the highly-dynamic heat transfer ahead of the fire. However, coupling the probes with a fine-wire thermocouple significantly improves its sensitivity. Results presented here indicate that the sensor and model are capable of measuring physically realistic convective and radiative heat transfer in high-intensity crown fire and simple laboratory scenarios when compared to observations in literature. Some limitations are identified for future investigation and additional testing and validation are required.