Heat transfer evaluation on ice roughened cylinders in transition regime

A high-resolution, non-intrusive heat transfer measurement method based on infra-red thermography and transient heat transfer analysis is presented. This technique was successfully applied to ice-roughened cylinders made from castings of natural accreted impact ice surface roughness. A total of eight representative icing conditions that contain two time series (30s, 60s, 90s, and 120s) were reproduced at the Adverse Environment Rotor Test Stand facility at the Pennsylvania State University. The ice roughness was retained using ice molding and casting techniques. Roughness on casting models was categorized into a smooth zone and a rough zone. Smooth to rough zone transition location and ice limit of each case was recorded. Arithmetic averages of roughness height (R_a) were measured for 10 locations (0°-90° azimuth angle) for each of the casting models. Empirical predictions for both maximum roughness height and smooth zone width have been proposed and resulted in mean absolute deviations of 15% and 7% respectively. Heat transfer measurements were conducted in a low-speed wind tunnel using thermal transient infra-red measurement techniques and validated against multiple embedded heat flux sensors as well as reference data found in the literature. The measured heat transfer coefficients were compared at three different test speeds (Re = 1, 2, 3×10⁵). Scaling of the heat transfer measurements at the turbulent regime was found necessary during comparison. A novel scaling coefficient for heat transfer in a turbulent regime, relates the Stanton and the Reynolds number (CSR) was introduced and has been proved to successfully scale the results from Re = 4.8×10⁴ to 4×10⁶.