radiative heat transfer in participating media
 

Hi everyone and merry xmas!

I'm modeling heat exchanger with two fluids separated by thin wall in CFX 12.1. One fluid is air and other is the exhaust gas modeled as a mixture of CO2, H2O, N2 and O2. The exhaust gas temperature is about 1250 K so I need to include radiation in participating fluid in my flow&heat transfer calculation.The problem is that when I set both fluids and assign them to the separate fluid domains (each on the oposite side of the wall) to flow throught the heat exchanger, I can not set thermal radiation option.
In that case thermal radiation field in Domain's Fluid Models definition tab can be set only to "none".
If I delete one of the fluids then I can set all radiation properties and solve my model. But in such case the exhaust gas is presented in the domain where air should be. So my results are not right even if I set emissivity factors to minimum for the walls of the "air" side to prevent exhaust gas from
absorbing and emitting heat energy on that side of heat exchanger.

Could someone please help me?