A small oven consists of a cubical box of dimension L  = 0.1 m, as shown. The floor of the box consists of a heater that supplies P = 400 W. The remaining walls lose heat to the surroundings outside the oven, which maintains their temperatures at T₃ = 400 K. A spherical object of diameter D = 30 mm is placed at the center of the oven. Sometime after the sphere is placed in the oven, its temperature is T₁ = 420 K. All surfaces have emissivities of 0.4.

(a) Find the following view factors: F₁₂, F₁₃, F₂₁, F₃₁, F₂₃, F₃₂, F₃₃.
(b) Determine the temperature of the floor and the net rate of heat transfer leaving the sphere due to radiation. Is the sphere under steady-state conditions?

Transcribed Image Text:

Radiation surface 3: remaining interior walls, T3, 83 Radiation surface 2: floor T2, 82 L L 4 + Radiation surface 1: sphere, D₁, T₁, 81 Bottom heating: P