Calculate the heat lost by the disk and the temperature of the shield. 8-60 Two concentric cylinders have properties of d = 20 cm, = 0.6, T = 500C and d2 = 40 cm, 2 = 0.7, T2 = 100C. Both are enclosed in a large room at 20C. Cal- culate the length of the cylinder that would enable one to use Equation (8-43) for calculating the heat transfer with no more than a 10 percent error.