Measurement and analysis of transient heat flux on a conical surface using platinum thin film gauges

In this study, both experimental and numerical methods to analyse the transient surface temperature and convective heat flux on a quartz-based conical body with laboratory-fabricated platinum thin-film gauges (film thickness 0.1–1.0 µm on 6 mm Ø × 10 mm quartz substrates) is carried out. During fabrication, platinum paste is dried at 650 °C and silver contacts at 350 °C, yielding a gauge resistance of 4–8 Ω and a measured temperature coefficient of resistance (TCR) of 0.02727 K⁻¹. Additionally, the work covers the dynamic calibration at a steady 10 mA current is supplied to each gauge while high-speed air at 318 K and velocities of 3–5 m/s impinged on the cone for 1 s. Transient temperature histories (300.0–300.7 K) are recorded at 0.01 ms intervals and processed via a one-dimensional semi-infinite conduction model to recover surface heat flux. Numerical simulations in ANSYS Fluent, employing a standard k-ε turbulence model with 0.01 ms time steps (100 steps) and adiabatic, no-slip boundary conditions, reproduced the same flow and thermal conditions. Experimental and numerical heat-flux signals exhibited excellent agreement (maximum convective heat flux ≈ 8 kW/m² at the stagnation point, with deviations < 5%), thereby validating the cost-effective gauge fabrication and calibration methodology and demonstrating its suitability for millisecond-scale surface-heat-flux measurements.