Abstract
This paper presents the results of analytical and experimental investigations of the local behaviour of turbulent heat and momentum transfer in a hot air flow through a cooled circular tube with a steep radial temperature gradient. It is concluded that in the turbulent core region the profiles of mixing length are not different from isothermal ones. It is presumed that the damping of mixing length near the wall is expressed by extending the Van Driest model to non-isothermal flow of gas. It is shown that the analytical prediction correlates the results of the measurements satisfactorily, and that in the cooling turbulent gas flow of low Reynolds number the deviations of the Nusselt number and friction factor from isothermal ones are negligibly small when they are correlated by using physical properties at bulk temperature.
