Surface to surface vs. Participating media. Slow progress.
 

Hi all!

I'm currently modelling HVAC in some room but have some difficulties with calculation progress using "surface to surface" both of Discrete Transfer and Monte-Carlo radiation models.
For model having ~15,000,000 tetra/hexa elements i've got approximately 150 iterations per 12 hours for participating media case. Don't know why, but when i switch to "surface to surface"
implementation no one (!) iteration had been completed per 12 hours. Just in case there is huge glazing of one side of the room.

Following settings are being used:

- ~15,000,000 tera/hexa elements with 2 non-conformal mesh interfaces;
- steady state;
- Gas: air ideal gas;
- Heat transfer model: thermal energy;
- Turbulence: k-eps;
- radiation: discrete ordinates (s2s), number of rays (12), spectral model - gray;
- glazing BC - fixed radiation heat flux, fixed outer temperature and heat transfer coefficient;
- PC: 8 x Xeon 2.5GHz, 32Gb OM, 60 Gb free space
- Ansys 16.2.

I guess that s2s implementation must be simplier that PM, isn't it?

Does anybody know how comes it and how can i fix it?
Can it depends on number of surfaces or it's shape (curving, edge length, etc.)?

Excuse me for my poor English. :)
Thanks in advance!