thin electrical heating tape is to be used in the laboratory to keep the temperature of a 0.35 kgs-1 stream of 45C water constant while it flows through a Teflon tube (k = 0.22 Wm-1 K-1 ) 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