Air at atmospheric pressure and 20 degree Celsius flows with 6 m/s velocities through the main trunk duct of the air conditioning system. The duct is rectangular in cross-section and measures 40 cm by 80 cm. Determine heat loss per meter length of duct corresponding to unit temperature difference. The relevant thermos-physical properties of air are v = 15 106 m2/s a-7.7. 10 2m?/hr k=0.026 W/m degree