Effect of thin-film sensors on local heat transfer in convective heat flux measurement

Thin-film heat flux sensors are usually attached to the interesting surface for the measurement of wall heat flux in the aerospace industry. However, the presence of the surface-mounted sensors may disturb the velocity and thermal boundary layer, alert the local wall heat flux, and induce erroneous measured results. This study numerically investigates the effect of the presence of thin-film heat flux sensors on the local flow and heat transfer. The effects of both Reynold number of the flow and the geometry of the sensor are investigated. The results show that the local convective heat transfer can be remarkably enhanced by the presence of the sensor. In particular, when the height of the thin-film heat flux sensor is within 2% of the flow boundary layer, the enhancement of the convection heat transfer caused by the heat flux sensor is independent with the inlet velocity of the flow. Finally, an empirical model for estimating the influence of the sensor on the heat transfer is established based on the numerical findings, which can provide a useful tool for practical design to evaluate and minimize the effect of the sensor on the local convective heat transfer.