A circular ice rink 60 m in diameter is enclosed by a hemispherical dome 100 m in diameter. The 0°C ice has emissivity of arink = 0.9, and the 20°C dome has emissivity of Edome = 0.3. The side ring seating area is a blackbody at 20°C. All surfaces are opaque, diffuse, and gray. Determine: A) The radiosity for the ice rink (Jrink), and the dome (Jdome). B) Net radiation heat transfer (grink-dome in W) between the ice rink and dome. Ddome 100 m Tdome = 20°C Drink - 60 m Trink=0°C Tseating = 20°C

11.68 Two infinitely large, black, plane surfaces are 0.3 m apart, and the space between them is filled by an isothermal gas mixture at 811 K and atmospheric pressure. The gas mixture consists of by volume. If one of the surfaces is maintained at 278 K and the other at 1390 K, calculate (a) the effective emissivity of the gas at its temperature, (b) the effective absorptivity of the gas to radiation from the 1390 K surface, (c) the effective absorptivity of the gas to radiation from the 278 K surface, and (d) the net rate of heat transfer to the gas per square meter of surface area.

11.41 Determine the steady-state temperatures of two radiation shields placed in the evacuated space between two infinite planes at temperatures of 555 K and 278 K. The emissivity of all surfaces is 0.8.

A tungsten filament is heated to 2700 K. At what wavelength is the maximum amount of radiation emitted? What fraction of the total energy is in the visible range (0.4to0.75m)? Assume that the filament radiates as a graybody.

Determine the rate of radiant heat emission in watts per square meter from a blackbody at (a) 15C, (b) 600C, and (c) 5700C.