High-Temperature calibration of direct write heat flux sensors from 25 °c to 860 °c using the in-cavity radiation method

Heat flux sensors fabricated using Direct Write Thermal Spray are thin, surface-based devices that can operate at high temperatures. In this paper, Direct Write heat flux sensors are calibrated over a temperature range of 25 °C-860 °C. A substitution-based quartz lamp configuration is used to measure the steady-state sensitivity and transient response of Direct Write sensors at ambient temperatures, with repeatability confirmed over a 10-month period and after thermal aging. A matched heat flow approach is used to characterize the sensors at operating temperatures up to 860 °C. The sensitivity is found to increase by a factor of two from 25 °C to 650 °C, after which it plateaus up to the maximum tested temperature of 860 °C. A cubic polynomial calibration function captures the temperature dependence of the sensitivity and provides a good agreement for the measured data.