 ## Fluids

Topics relate to Fluent, CFX, Turbogrid and more

• RicardoGomes
Subscriber

Good afternoon,

My name is Ricardo Gomes and I'm trying to calculate and simulate the temperature of an antenna in space. The antenna is not a gray-diffuse body, this is emission and absorptivity are different (lets assume epsilon = 0.9 and alpha = 0. .

ANSYS doc. says that: "Radiation exchange between surfaces is restricted to gray-diffuse surfaces. Gray implies that emissivity and absorptivity of the surface do not depend on wavelength (either can depend on temperature). Diffuse signifies that emissivity and absorptivity do not depend on direction. For a gray-diffuse surface, emissivity = absorptivity; and emissivity + reflectivity = 1. Note that a black body surface has a unit emissivity."

Does this mean that it is not possible to have different values for the emissivity and absorptivity?

Should I compute this values based on hand calculation using the total flux that is absorbed by the material. This is, I have a thermal flux due to solar radiation that is 1400 W/m^2. If the material as a absorptivity of 0.6 I must only assume and heat flux of 1400*0.6 = 840 W/m^2. 