Integrated heat-flux sensors for harsh environments using thermal-spray technology

Heat-flux sensors are widely used in thermal and heat-transfer engineering applications. Commercial heat-flux sensors currently available for harsh environments, however, remain limited due to complications in positioning/attaching the sensor onto the component, the inability to operate at high temperatures, and potentially altering or degrading the engineering device by the physical presence of the sensor. In this paper, heat-flux sensors have been fabricated for the first time entirely by using a thermal-spray technology. The sensors are fabricated directly onto engineering surfaces and consist of five to seven thermocouples arranged electrically in series and thermally in parallel, such that the heat flux is measured normal to the surface, on which the sensor resides. Devices are tested under both steady-state and transient conditions at temperatures up to 100°C. They exhibit a very good linearity between the heat flux and voltage output. Analytical modeling of the steady-state and transient responses is also presented and compared to experimental results. If successful, thermal-spray heat-flux sensors could represent a significant enabling technology for heat-flux sensing at high temperatures, in harsh environments, and in embedded sensor applications.