Question

I have been using the stefan Boltzmann equation to calculate the radiation rate of a surface made of carbon fiber that has 0.96 emissivity factor. The temperature of the radiating surface is at 38ºc with 10 m2. the temperature of the surroundings is at 4ºC. I get 1969 Watts.
My problem is that when I want to calculate the same radiative power into a specific wave length, the same equation gives 54 watts approx ..finding out that 53% is in the 3 to 14 um range.
My question why do I get 54 watts for the same temperature and the same surface while I had previously 1969 Watts of radiative powe

Answer 1

thank you very much for your prompt answers.
What I trying to do is measure the quantity of radiation of a plane surface of 10M2 made of carbon fiber funcioning at 38ºC in the 3 to 14 um wavelength range.
Emissivity is 0.96.
I have been using the equations of hyper physics first to calculate the radiation rate and then the quantity of it within the above mentioned range. I´ve verifired 3 times and i am actually using the same parameters but it gives rather different values as stated above.
I would really appreciate if you could help me through with this.
Thank you

Answer 2

in the first calculation I am using Tc at 4ºC.

Answer 3

actually not .. well if I understand well. Please go to the following link http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html cliking on "heat and thermodynamics" and then on "radiation". Input the above parameters and it will give you 1969 watts. Then, on the same page, further below, there is a link that says "Fraction of power in a wavelength range". Please input the same values you will see that it gives 53 Watts instead of 1969. This is what I do not understand. It makes me feel like an idiot which is what I probably am so your help is more appreciated. thanks