Two parallel back disks are positioned coaxially with a distance of 0.25 m apart. The lower disk is 0.2 m in diameter and the upper disk is 0.4 m in diameter. If the lower disk is heated electrically at 20 W to maintain a uniform temperature of 500 K, determine the temperature of the upper disk.

A square 2014-T4 aluminum alloy plate 370 mm on a side has a 50-mm-diameter circular hole at its center. The plate is heated from 16°C to 56°C. Determine the final diameter of the hole. Answer: dfinal mm =

Consider a 150 W incandescent lamp in a room at 25 °C. The filament of the lamp is 5 cm long and has a diameter of 0.5 mm. The emissivity of the filament is 0.90. The diameter of the glass bulb of the lamp is 8 cm. The inside surface temperature of the glass bulb is 150 °C. Determine: (a) the heat flux, in W∙m-2, on the surface of the filament, (b) the heat flux, in W∙m-2, on the surface of the glass bulb, and (c) the surface temperature of the filament. The surface area of a sphere is ? = 4??2, and the volume of a sphere is ? = (4?/3)?3.

Consider a double-paned window consisting of two panes of glass, each with a thickness of 0.500 cm and an area of 0.795 m2 , separated by a layer of air with a thickness of 1.50 cm. The temperature on one side of the window is 0.00 ∘C∘C; the temperature on the other side is 21.0 ∘C∘C. In addition, note that the thermal conductivity of glass is roughly 36 times greater than that of air. Approximate the heat transfer through this window by ignoring the glass. That is, calculate the heat flow per second through 1.50 cmcm of air with a temperature difference of 21.0 ∘C∘C. (The exact result for the complete window is 25.6 J/sJ/s .)