Convective heat transfer on a plate in an impinging round hot gas jet of low Reynolds number

Abstract

An experimental study has been made of the local heat transfer on the plane isothermal surface in the normal impinging round hot jet of combustion products produced by a rapid heating tunnel burner. A conductivity heat plug, impact tubes and fine wire thermocouples were used to measure heat flux, mean velocity and temperature distributions. Some centerline relative turbulence intensity measurements were done with a Laser Doppler Anemometer. All measurements were obtained at two efflux Reynolds numbers 1860 and 1050; the density ratio between hot combustion products and ambient air was 7.6. Heat transfer was measured at distances between 2 and 20 D. The stagnation point heat transfer within the distances xD ⩽ 5 is in good agreement with Sibulkin's laminar boundary layer theory. In the developed region xD ⩾ 8 strong free jet turbulence effects augmenting the convective heat transfer were observed. The radial heat transfer distributions are qualitatively consistent with those known in the impinging cold jet investigations at low Reynolds numbers.