Air at 1 atm and 100°C flows through a straight, 5-cm-diameter circular tube, cast from naphthalene, at a Reynolds number of 1,500. Air entering the tube has an established laminar-flow velocity profile. Properties are given in Example 3.14. If pressure drop through the tube is negligible, calculate the length of tube needed for the average mole fraction of naphthalene in the exiting air to be 0.005.