Transient heat flux assessment using a platinum thin film sensor for short-duration applications

The rapid fluctuations in heat transfer rates make it challenging to determine the surface temperature history and the estimation of accurate heat generation in research applications such as IC engines, gas turbines, and high-speed space vehicles. Therefore, thin-film heat flux sensors (TFHFS) are generally used to measure the heat flux in such applications due to their high sensitivity and quick response time. The present study demonstrates that increasing the annealing heat treatment temperature will enhance the adhesion of the thin film and the capabilities of these hand-made TFHFS for transient measurements at low temperatures and for short periods. In the present work, TFHFS is fabricated in-house using platinum as a sensing element and Macor as an insulating substrate. The sensitivity (S) and temperature coefficient of resistance (TCR) are estimated using an oil batch calibration technique. At the same time, the performance of TFHFS is tested in a dynamic convective environment. The TFHFS is exposed to the convective environment using a designed calibration set-up, and their transient heat fluxes are computed by conducting several trials. Additionally, the numerical solution has been accomplished using various experimental parameters. In comparison to the outcomes of the experimental method, it is observed that the average fluctuating temperature and mean surface heat flux have an inaccuracy of 0.33% and 4.17% respectively.