A thin electrical heating tape is to be used in the laboratory to keep the temperature of a 0.35 kgs' stream of 45C water constant while it flows through a Teflon tube (k= 0.22 Wm'K") of 2.5 cm outer radius and 4.0 mm wall thickness. The tube is mounted horizontally in quiescent 20C air, and the heating tape generates heat uniformly at the outer surface of the tube. a. Neglecting radiation exchange, calculate the heat flux that must be supplied by the tape to ensure a uniform water temperature of 45C in the tube. b. If the emissivity of the outer surface of the tube is 0.95 and the large surroundings are at 15C, recalculate the required heat flux by accounting for radiation exchange with the large surroundings