Heat transfer measurements on a flat plate and cylinders at high velocity conditions: Comparison of calculation models with infrared thermography

In this study, various heat transfer measurement models using infrared (IR) thermography were applied to a flat plate and cylinders to examine the accuracy and suitability of the measurements in a transonic blow-down test facility recently developed at Korea Aerospace University. Experiments were performed under three inlet velocity conditions for the flat plate, and for the cylinders, two diameters, two turbulence intensity levels, and five inlet velocity conditions. The surface temperature distribution during the experiment was acquired using an IR camera, and the surface heat transfer coefficient (HTC) was calculated using four HTC calculation models based on the one-dimensional semi-infinite (1D SI) solid assumption: step change (STEP), Duhamel's superposition (DUH), 1D finite volumetric model (1D FVM), and linear regression model (LRM). The LRM showed minimum deviation with reference correlation for the flat plate heat transfer measurements, while STEP, DUH, and 1D FVM showed increased deviations at higher mainstream velocity conditions. The measurements by LRM at the cylinder stagnation location showed the most comparable value with the reference correlation, whereas STEP and FVM showed about 10% deviation from the reference. It is concluded that the LRM is the most suitable heat transfer calculation model for high velocity tests because the model excludes the ramping data during the transient tests, and it can also obtain the local adiabatic wall temperature experimentally.