Air at 40°c flows over a long, 25-mm-diameter cylinder with an embedded electrical heater. in a series of tests, measurements were made of the power per unit length, p’, required to maintain the cylinder surface temperature at 300°c for different free stream velocities u of the air. the results are as follows:

air velocity, u (m/s) 1 2 4 8 12
power, p’ (w/m) 450 658 983 1507 1963

(a) determine the convection coefficient for each velocity, and display your results graphically.
(b) assuming the dependence of the convection coefficient on the velocity to be of the form h = cu n , determine the parameters c and n from the results of part (a)

A3-mm-thick panel of aluminum alloy (k 177 w/m-k, c 875 j/kg-k and ? = 2770 kg/m) is finished on both sides with an epoxy coating that must be cured at or above t,-150°c for at least 5 min. the production line for the curing operation involves two steps: (1) heating in a large oven with air at ts,0-175°c and a convection coefficient of h, 40 w/m2. k, and (2) cooling in a large chamber with air at 25°c and a con- vection coefficient of he 10 w/m2.k. the heating portion of the process is conducted over a time interval te which exceeds the ime required to reach 150°c by 5 min (h = r + 300 s). the coating has an emissivity of ? = 0.8, and the temperatures of the oven and chamber walls are 175 and 25°c, respectively. if the panel is placed in the oven at an initial temperature of 25°c and removed from the chamber at a safe-to-touch tempera ture of 37°c, what is the total elapsed time for the two-step curing operation?