Consider the application of the Dittus-Boelter relation [Equation (6-4a)] to turbulent flow of air in a smooth tube under developed turbulent flow conditions. For a fixed mass flow rate and tube diameter (selected at your discretion) investigate the effect of bulk temperature on the heat-transfer coefficient by calculating values of h for average bulk temperatures of 20, 50, 100, 200, and 300oC. What do you conclude from this calculation? From the results, estimate the dependence of the heat-transfer coefficient for air on absolute temperature.