Air at 1 atm and 285 k enters a 2-m-long rectangular duct with cross section 75 mmx150 mm. the duct is maintained at a constant surface temperature of 400 k, and the air mass flow rate is 0.10 kg/s. determine the heat transfer rate from the duct to the air and the air outlet temperature.

At steady state, air at 200 kpa, 325 k, and mass flow rate of 0.5 kg/s enters an insulated duct having differing inlet and exit cross-sectional areas. the inlet cross-sectional area is 6 cm2. at the duct exit, the pressure of the air is 100 kpa and the velocity is 250 m/s. neglecting potential energy effects and modeling air as an 1.008 kj/kg k, determine ideal gas with constant cp = (a) the velocity of the air at the inlet, in m/s. (b) the temperature of the air at the exit, in k. (c) the exit cross-sectional area, in cm2