Cancel
Showing results for
Did you mean:

Valued Contributor

Hi everyone, one more problem that i can´t solve

Just trying to understand the basics on how this software calculates

My model:  A small heat source and a solid to be heaten on steady state condition

Boundary counditions: radiation (all) and radiative heating (solar, collimated and total power)

The weird part

When i set a thermal optical property for the solid which i want to heat up, i get the following scenarious

1) Solar absorptivity = 1 and on infrared properties, Transmissivity = 1 my solid gets hot

2) Solar Absorptivity = 1 and on infrared properties, Reflectivity = 1, solid doesn´t have it´s temperature changed.

As far as i know, if the absorption coefficient  is higher than 0, photons will be absorbed and a fraction will be reemited and the rest will be transformed in kinect energy. When the system  reaches thermal equilibrium, emissivity = absorption (Kirchoff Law)

So, i thought that with those boundary counditions, the following would happen

Boundary coundition: Spectrum Solar and total power of 300 W = a wavelength distribution of a 5000K (around 45% in visible light and 49 % in IR and 6% UV ) black body (sun) which provides 300 J/s of energy for my solid.  Solar absorptivity = 1 means everything will be absorbed and, since infrared emissivity = 0, 0 J/s can be emitted in IR zone. Conclusion: the solid should heat up, but on the simulation it remains in 20 C

Can anyone help me to understand how NX 10 deals with radiation?

2 REPLIES

Creator
Hi, carlosmeo. Can you send model files? I'll see settings and advise how to solve the problem.