Hello everybody,
I am modeling a Direct Absorption Collector (DAC) using the discret ordinate model available in Ansys Fluent. I have to define the absorption coefficient of a semi transparent medium (Glass) in the material list panel which unit is (m-1). I have found in the manufacturer's catalog that the absorption coefficient of glass is 92%. Do I have to divide this value by the glass's thickness, and then to introduce it in fluent ?
I think the number they are giving you is the extinction coefficient (k). If that is true, then you can calculate the absorption coefficient using the equation:
a=4*pi*k/lambda.
Where:
a: Absorption coefficient (m-1)
k: extinction coefficient (specific to a wavelength)
lambda: radiation wavelength (m), these usually are presented in nm
I assume the number they gave you has a validity to wavelengths related with some temperature. If you know the temperature of the body that emitted the radiation you can use Wien's law to calculate the peak intensity wavelength emitted by a blackbody:
lambda=b/T
Where:
T: Temperature of blackbody (K)
b: Wien's constant (0.028977 m*K)
I hope this is helpful. If you like the answer please vote it up.
Good luck!
if using the above formula, and using the 92%, and a temperature 1200k, that will get a very large absorption coefficient: 478,146 (m-1), is this reasonable?
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