- A Rectangular Air Heating Duct Is Suspended From The Ceiling Where The Ambient Temperature Is 5 C The Duct Is 15 M Lo 1 (311.84 KiB) Viewed 29 times
A rectangular air heating duct is suspended from the ceiling, where the ambient temperature is 5 °C. The duct is 15 m long, and its cross-section is 350 mm x 200 mm. (Given the properties of air:p=1.1 kg/m3 and Cp= 1008 J/kg) (b) For an uninsulated duct with average outer surface temperature of 50 °C, estimate the rate of heat loss from the duct. Given, the surface emissivity and convection coefficient are approximately 0.5 and 4 W/m².K, respectively. (5 marks) If heated air enter the duct at a temperature of 58 °C and a velocity of 4 m/s and the heat loss corresponds to the result of part (a), what is the outlet temperature? (5 marks) If the air heating duct is insulated with 4 cm of rubber (k = 0.15 W/m.K), determine the heat loss using shape factor method by considering the heat loss from the edge and neglect the radiation. Assume the temperature difference between the inner and outer surface of the rubber is 40 °C. (c) (d) (8 marks) After the duct is insulated as stated in part (c), what is the outlet temperature and how many percentage that the heat will be saved? (5 marks) What is the disadvantage of using rectangular duet compare to circular pipe?