20.500.12556/RUL-152539 Thermal streak spacing in fully developed duct flow with different Reynolds and Prandtl numbers The present study investigates the behaviour of thermal streaks on a heated foil which is cooled with turbulent flow in a square duct channel. Real-time infrared thermography is used to visualize and measure the spacing between the thermal streaks. A stainless-steel foil with a thickness of 25 microns is cooled by water. The experiments were performed in a range of Reynolds numbers from 5000 to 20000 and Prandtl numbers from 3 to 7. The mean temperature, root-mean-square of temperature and autocorrelation function have been calculated and used to measure the average thermal streak spacing and power spectra in the spanwise and streamwise directions. The root mean square temperature was 0.3 °C to 0.5 °C which corresponds to roughly 10% of the mean temperature difference between foil and water. The uncertainty in mean temperature difference and root mean square temperature was around 5% and 10%, respectively. The measured thermal streak spacing was 100 wall unit to 180 wall unit under the present experimental range. The uncertainty in measured thermal streak spacing was around 2.5%. The effects of Reynolds number, Prandtl number and heat flux on the thermal streak spacing and also on the statistics of the temperature field have been presented and discussed in this paper. A new correlation has been proposed to predict the dimensionless thermal streak spacing. The error in the prediction is estimated within ± 15 %. thermal streaks thermal streak spacing Reynolds number Prandtl number heat flux true false true Angleški jezik Ni določen Članek v reviji 2023-11-27 09:44:00 2023-11-27 09:44:00 2023-11-28 03:36:29 0000-00-00 00:00:00 2023 0 0 Str. 2105–2116 iss. 11 Vol. 59 2023 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 621.039 1432-1181 10.1007/s00231-023-03399-z 159282435 s00231-023-03399-z_(1).pdf s00231-023-03399-z_(1).pdf 1 4BE6CEE080B58B95A7F50B83BAA4C503 9f4a276cf2074805fc7387abea3b737e6b8f6dce9891535e27a22653ec204f26 65b01401-8d01-11ee-8ac8-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=178062 https://link.springer.com/article/10.1007/s00231-023-03399-z 0 4a049fbc-8d01-11ee-8ac8-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=178061 Fakulteta za matematiko in fiziko 0 0 0