Problem Set #11 Combined Heat Transfer Modes Consider a cylindrical boiler in an enclosed room. The fluid inside the boiler is maintained at 300 C, and the convective heat transfer coefficient between the fluid W . The inside m2 C diameter of the boiler is 3m, the steel boiler walls are 4 cm thick, and the insulation wrapped around the boiler is 10 cm thick. The room is 15m square (15m long x 15m wide). The boiler is 3m tall and the room walls are Sm tall. Through ventilation, the air and walls ofthe room are maintained at 30 C. The average air velocity around the inside the boiler and the interior surface ofthe boiler walls is 50 outside of the boiler is 0.5 %. Neglect heat transfer from the top and bottom surfaces of the boiler, and neglect heat transfer to the ceiling and floor ofthe room. Calculate the total rate of heat transfer (thermal loss) from the fluid inside the boiler. Given: W ksteel = 60 m ac W kinsulation = 0-03 m QC 5 insulation = 0-9 5room walls 2 0-85 Properties of air at about 100 C (approx. film temp.): kg = 0.9458 p m3 Pr = 0.7111 w k = 0.03095 . m C m2 v = 2.306 x 105 T 39