a) An unknown specimen, 2.5 cm in diameter and 1 cm thick (a disk) is placed in a device that measures thermal conductivity. The device works by passing heat (measured to be 98 W) through the disk in the axial direction (1 cm thickness). The temperatures of the axial faces of the disk are measured to be 40 and 35, C respectively. What is the thermal conductivity of the disk? What material is it?
b) What is the thermal resistance to heat flowing radially in an aluminum annular ring (k=160 W/m/K) with the inside and outside radii of 3 and 3.5 cm, respectively? The annular ring is 10 cm long.