Consider Problem 9.95 with N = 4 sheets of thin aluminum foil ( = 0.07), equally

Question:

Consider Problem 9.95 with N = 4 sheets of thin aluminum foil (ε_ƒ = 0.07), equally spaced throughout the 50-mm gap so as to form five individual air gaps each 10 mm thick. The hot and cold surfaces of the enclosure are characterized by E = 0.85.

(a) Neglecting conduction or convection in the air, determine the heat flux through the system.

(b) Accounting for conduction but neglecting radiation, determine the heat flux through the system. The effect of variable properties is important. Calculate the air properties for each gap independently, based on the average gap temperature.

(c) Accounting for both conduction and radiation, determine the heat flux through the system. Calculate the air properties for each gap independently.

(d) Is natural convection negligible in part (c)? Explain why or why not.