DOI: 10.1615/TSFP5
MEASUREMENTS OF TIME-SPACE DISTRIBUTION OF CONVECTIVE HEAT TRANSFER TO AIR USING A THIN CONDUCTIVE-FILM
SINOPSIS
A measurement technique of time-space characteristics of heat transfer to air has been developed using a thin conductive film and a high-speed infrared thermograph. In this work, a titanium foil of 2 µm thick was used as a test surface, and measured temperature on it by employing an infrared thermograph of 120 Hz. The accuracy of the measurements was confirmed by comparing the heat transfer coefficient of a laminar boundary layer to that of a numerical analysis. In order to verify the applicability of this measurement technique to practical measurements, unsteady heat transfer on the wall of a turbulent boundary layer was examined. It was possible to restore the time-space distribution of the heat transfer coefficient up to 30 Hz in time and 4.5 mm in spatial wavelength by solving the heat conduction equations inside the wall, even though the heat transfer coefficient was low (h = 10 − 20 W/m2K). The results showed that the time-space behavior of the heat transfer was clearly revealed, which was reflected by the streaks formed in the near-wall region of the turbulent boundary layer. The statistical values of the turbulent boundary layer, that is, rms value of the fluctuating heat transfer coefficient and mean spacing of the thermal streaks, agreed well to those of previous data of DNS and experiments.