A 2-in.-OD stainless steel tube has 16 longitudinal fins spaced around its outside surface as shown. The fins are 1/16-in. thick and extend 1 in. from the outside surface of the tube.
a. If the outside surface of the tube wall is at 250°F, the surrounding air is at 80°F, and the convective heat-transfer coefficient is 8 Btu/h ft²°F, determine the percent increase in heat transfer for the finned pipe over that for the unfinned pipe.
b. Determine the same information as in part (a) for values of h of 2, 5, 15, 50, and 100 Btu/h ft²°F. Plot the percent increase in q vs. h. What conclusions can be reached concerning this plot?