Shock-tube measurements of end-wall radiative heat transfer in air.

Abstract

Measurements of radiative heat transfer to the end wall of a shock tube are presented for incident shock velocities from 6.5 to 9.5 mm/jusec and an initial driven tube pressure of 1-mm Hg. A thin film heat- transfer gage, mounted behind a sapphire window at the end of an arc driven shock tube, was used to measure the radiative flux behind reflected shock waves in air and in the wavelength region of 0.17 to 6 jit. Radiative heating rates in excess of 150 kw/cm2 were observed. For the conditions of the experiment, it is shown that equilibrium radiation dominates the end- wall heat transfer, and the experimental data are compared with equilibrium air radiation calculations for a transparent, homogeneous gas. For the higher shock velocities, the data are found to be factors of 2 or more lower than this prediction. Calculations are also presented to show the importance of radiative cooling and self- absorption. These calculations are compared with the data and the importance of these phenomena are discussed.