An 8-m-long, uninsulated square duct of cross section 0.2 m × 0.2 m and relative roughness 10–3 passes through the attic space of a house. Hot air enters the duct at 1 atm and 85°C at a volume flow rate of 0.15 m3/s. The duct surface is nearly isothermal at 60°C. Determine the rate of heat loss from the duct to the attic space and the pressure difference between the inlet and outlet sections of the duct. Evaluate air properties at a bulk mean temperature of 80°C. Is this a good assumption?.