In the central receiver concept of a solar power plant, many heliostats at ground level are used to direct a con- centrated solar flux qs" to the receiver, which is posi- tioned at the top of a tower. However, even with absorption of all the solar flux by the outer surface of the receiver, losses due to free convection and radiation reduce the collection efficiency below the maximum possible value of 100%. Consider a cylindrical receiver of diameter D = 7 m, length L = 12 m, and emissivity s = 0.20.
(a) Estimate the heat gain through the door for the worst case condition corresponding to no insulation (L = 0).
(b) Compute and plot the heat gain and the outer sur- face temperature Ts,o as a function of insulation thickness for 0 L 25 mm.