Consider the conditions of .49, but nowallow for radiation

Chapter 7, Problem 7.50

(choose chapter or problem)

Consider the conditions of 7.49, but nowallow for radiation exchange between the surface of theheating element (??0.8) and the walls of the duct,which form a large enclosure at 27?C.(a) Evaluate the steady-state surface temperature.(b) If the heater is activated from an initial temperatureof 27?C, estimate the time required for the surfacetemperature to come within 10?C of the steady-state value.(c) To guard against overheating due to unanticipatedexcursions in the blower output, the heater con- troller is designed to maintain a fixed surface tem-perature of 275?C. Determine the power dissipationrequired to maintain this temperature for air veloci-ties in the range 5V10 m/s.