Gardon gauge measurements of fast heat flux transients

• A fast heat flux transient measurement method using Gardon gauges is introduced.
• Simulations and experiments of heat flux transient measurements verify the method.
• Convert Gardon gauge with a limited response to fast-response heat-flux sensor.
• Gardon gauge measurement accuracy is improved for heat flux transients.

Heat flux measurements are widely used in thermal analyses. Gardon heat flux gauge are a widely used diffusion type heat flux gauge that can be used in harsh thermal environments such as in fires, combustors, and aerospace applications. However, Gardon gauges are usually regarded as quasi-steady-state sensors with a limited frequency response and are not often used for transient measurements. This paper introduces a fast radiative heat flux transient measurement method using Gardon gauges. The analysis assumes that the heat flux transient is a continuous function of time in every small/micro time interval. The transient heat flux density functions are determined from the transient output voltages of the gauge. Two cases with fast and slow heat flux transients were numerically investigated to verify the method. The analyses show that the gauge transient response must be corrected not only for fast heat flux transients, but also for slow heat flux transients. The gauges were then tested in experiments to measure radiative heat flux transients on a hot graphite plate in a vacuum chamber to evaluate the effects of the corrections. This method can use a limited frequency response Gardon gauge for fast heat flux measurements without other instrumentation adjustments. The Gardon gauges measurement accuracy is then greatly improved with transient measurements. The analysis shows how to accurately measure transient heat fluxes and improve the performance of Gardon gauges.