Thermal streak spacing in fully developed duct flow with different Reynolds and Prandtl numbers

Abstract The present study investigates the behaviour of thermal streaks on a heated foil which is cooled with turbulent flow in square duct channel. Real-time infrared thermography used to visualize and measure spacing between streaks. A stainless-steel thickness 25 microns by water. experiments were performed range Reynolds numbers from 5000 20000 Prandtl 3 7. mean temperature, root-mean-square temperature autocorrelation function have been calculated average streak power spectra spanwise streamwise directions. root was 0.3 °C 0.5 corresponds roughly 10% difference uncertainty around 5% 10%, respectively. measured 100 wall unit 180 under experimental range. 2.5%. effects number, number heat flux also statistics field presented discussed this paper. new correlation has proposed predict dimensionless spacing. error prediction estimated within ± 15 %.