Reflectivity measurements are often used to obtain surface radiation properties. Diffuse spectral reflectivity of a fire brick wall maintained at 500 K is shown below:
The wall is exposed to a bed of coal at 2500 K. Determine the total hemispherical emissivity and emissive power of the fire brick wall. What is the total absorptivity of the wall to the irradiation resulting from emission by coal?
Use the following Plank's radiation functions :
|
lT (mmK)
|
F(0 - l)
|
|
1,200
6000
30,000
|
0.0025
0.7383
0.9912
|
Assume that the brick wall is opaque and the spectral distribution of irradiation at the brick wall approximates that due to emission from a black body at 2500 K.