Air enters a smooth insulated 25-mm-duct at a Mach number of 0.35, a temperature of 5◦C, and a pressure of 120 kPa. What is the maximum length of duct that could be used without affecting the inflow...

Air enters a smooth insulated 25-mm-duct at a Mach number of 0.35, a temperature of 5◦C, and a pressure of 120 kPa. What is the maximum length of duct that could be used without affecting the inflow conditions? Under this limiting condition, what would be the temperature, pressure, and velocity at the exit? Assume that the dynamic viscosity of air depends only on the temperature of the air and that the friction factor at the entrance of the duct is representative of the friction factor throughout the duct.