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nlexa [21]
4 years ago
12

Consider a 20-cm X 20-cm X 20-cm cubical body at 477°C suspended in the air. Assuming the body closely approximates a blackbody,

determine
(a) the rate at which the cube emits radiation energy, in W and
(b) the spectral blackbody emissive power at a wavelength of 4 µm.
Engineering
1 answer:
Olin [163]4 years ago
8 0

Answer:

a) The rate at which the cube emits radiation energy is 704.48 W

b) The spectral blackbody emissive power is 194.27 W/m²μm

Explanation:

Given data:

a = side of the cube = 0.2 m

T = temperature = 477°C

Wavelength = 4 µm

a) The surface area is:

A_{s} =6a^{2} =6(0.2)^{2} =0.24m^{2}

According Stefan-Boltzman law, the rate of emission is:

E=\sigma T^{4} A_{s} =5.67x10^{-8} *(477)^{4} *0.24=704.48W

b) Using Plank´s distribution law to get the spectral blackbody emissive power.

E=\frac{C_{1} }{\lambda ^{5}(exp(\frac{C_{2} }{\lambda T}) -1 )} =\frac{3.743x10^{8} }{4^{5}(exp(\frac{1.4387x10x^{4} }{4*477})-1)  } =194.27W/m^{2} \mu m

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4 years ago
3. A 4-m × 5-m × 7-m room is heated by the radiator of a steam-heating system. The steam radiator transfers heat at a rate of 10
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<u>OR</u>

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Let's first start by mentioning the specific heat of air at constant volume. We consider constant volume and NOT constant pressure because the volume of the room remains constant while pressure may vary.

Specific heat at constant volume at 27°C = 0.718 kJ/kg*K

Initial temperature of room (in kelvin) = 283.15 K

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Answer:

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Explanation:

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