Consider a cubical furnace with a side length of 3 m. The top surface is maintained at 700 K. The base surface has emissivity of
0.90 and is maintained at 950 K. The side surface is black and is maintained at 450 K. Heat is supplied from the base surface at a rate of 340 kW. Determine the emissivity of the top surface and the net rates of heat transfer between the top and bottom surfaces, and between the bottom and side surfaces. Answers: 0.44; 54.4 kW; 285.6 kW
1 answer:
Answer:
Check the explanation
Explanation:
Assumptions.
1. The surfaces are diffuse, may and opaque
2. steady operating conditions exist
3. Heat transfer from and to the surfaces is only due to Radiation
Consider the base surface to be surface 2 the top surface to be surface and the side surfaces to surface 3 1. cubical furnace can be considered to be three-surface enclosure. the areas and black body emissive powers of surfaces can be calculated as seen in the attached images below.
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Answer:
1.
2.
Explanation:
1.
Given:
- height of the window pane,
- width of the window pane,
- thickness of the pane,
- thermal conductivity of the glass pane,
- temperature of the inner surface,
- temperature of the outer surface,
<u>According to the Fourier's law the rate of heat transfer is given as:</u>
here:
A = area through which the heat transfer occurs =
dT = temperature difference across the thickness of the surface =
dx = t = thickness normal to the surface =
2.
- air spacing between two glass panes,
- area of each glass pane,
- thermal conductivity of air,
- temperature difference between the surfaces,
<u>Assuming layered transfer of heat through the air and the air between the glasses is always still:</u>