Design and Fabrication of a Thick Film Heat Flux Sensor for Ultra-High Temperature Environment

In this paper, a ceramic-based thick film heat flux sensor (TFHFS) to monitor the heat flux in high-temperature environments is described. The TFHFS consists of 130 pairs of Pt-Pt/Rh thermocouples distributed in a serpentine form on a ceramic substrate. An insulator was used to generate the temperature difference, which increases the thermoelectric potential (output voltage) and improves the sensitivity of the proposed TFHFS. There are two pairs of independent thermocouples for temperature monitoring. The screen-printing process is used as the fabrication process. The characterization results indicate that the Pt electrodes and the Pt/Rh electrodes were well connected after sintering at 1350°C, and the thickness and width of the thermocouple electrodes were approximately $20~\mu \text{m}$ and $300~\mu \text{m}$ , respectively. The test results indicate that the proposed heat flux sensor has a maximum output voltage of approximately 1.44 mV, and the heat flux sensitivities for 3-57 kW/m
²
were well distributed in the range of 0.025-0.030 mV/(kW/m
²
), thereby demonstrating that the fabricated sensor exhibits high sensitivities in the given heat flux range. Furthermore, the reusability investigation indicated that the prepared TFHFS achieves a stable output voltage and a low error level at 50-900 °C. Therefore, we assume that the proposed sensor can be used for monitoring the heat flux in harsh applications such as turbomachinery and aerospace industries.