The effect of variable properties on momentum and heat transfer in a tube with constant wall temperature

Abstract The effect of variable properties on momentum and heat transfer is investigated applying an asymptotic method that had been used before with the thermal boundary condition q w = const. Though the changes are in the thermal boundary condition only it turns out that both cases are quite different in several aspects. As a main result it turns out that a method empirically used in both cases (property ratio method) is not uniquely valid in the T w = const. case of this study.