Consider a thin circular disk that has been heated up to 100 °c and then left inside a chamber to cool down. the chamber surface is kept at 50 °c and the air inside is maintained at 20 °c. assume that the disk is held at the center of the chamber and the heat conduction is neglectable. what is the total rate of heat transfer from the disk? the disk diameter is 500 mm and the surface emissivity is ε = 0.5. note: air properties: υ = 20.92×10-6 m2 /s, k = 30×10-3 w/mk, pr = 0.7, α = 29.9×10-6 m2 /s and