Durable Heat Flux Sensor for Extreme Temperature and Heat Flux Environments

This paper reports on the development and evaluation of a novel heat flux sensor, the high-temperature heat flux sensor,tested at temperatures and heat flux levels in excess of 1000 degrees C and 10-13 W/cm(2), respectively. The current sensor configuration uses type-K thermocouple materials in a durable welded thermopile arrangement contained within a surface-mountable high-temperature housing. The steady-state sensitivity of the design is predicted using a simplified one-dimensional thermal-resistance model. The design performance of a prototype sensor is validated using both conduction and convection heat transfer calibration at low temperature. The average experimental values of the sensitivity are 623 +/- 33 mV/W/cm(2) and 579 +/- 29 mV/W/cm(2) in conduction and convection, respectively. These calibration results compare very well with the predicted room-temperature sensitivity or 559 mu V/W/cm(2). Minimal dependence on heat transfer coefficient is found in convection. Prolonged thermal cycling of the sensor using a high-temperature kiln and a propane torch apparatus demonstrates survivability near the maximum temperature of the thermoelectric materials with negligible oxidation or loss of calibration.