CFD Online Discussion Forums

CFD Online Discussion Forums (
-   CFX (
-   -   Model with Thermal radiation (

Roland R June 14, 2012 09:19

Model with Thermal radiation

I would like to calculate a steady state simulation with fluid and solid domains. The temperature is quite high in the solids (300-400C) therefore the thermal radiation is important.

I experiment with a simple 2D modell. Firstly I made the modell without thermal radiation. Finally I added the thermal radiation to the model and it was initialized from the previous result. The first model run very fast but the second one (with thermal radiation) is very very slow.

Why does the modell become so difficult with thermal radiation?

The values of parameters (in terms of thermal radiation) are default, I didnít change it. I use the Monte Carlo model, and the Surface to surface option. Is it correct to solve this problem?

Thanks a lot

ghorrocks June 14, 2012 19:07

Mone Carlo radiation simulation is often slow as it is very computationally intensive. If the fluid does not interact with the radiation much (ie radiation just causes surface to surface heat transfer) consider the Discrete Transfer model, it is much faster.

Roland R June 15, 2012 05:52

I complated a simple 3D model. There is a large air domain, and it contains two cylinders (with diameter 10cm). Material of the cylinders is steel. Distance between the cylinders is 1cm. Temperature of one of two cylinders is 400C. It was defined at the wall of cylinder. Velocity of air is 1m/s.

Based on result, temperature of second cylinder will be about 122-129C. I don't understand this. I think that the temperature of second cylinder should be more higher.

Which parameter can be incorrect (in case of thermal radiation)? (At the moment all parameters and settings are default.)


ghorrocks June 15, 2012 06:57

If you are new to radiation modelling I strong recommend you do a simple model with an analytical answer (eg heat transfer between two parallel plates) to make sure you know how to get accurate answers in radiation modelling before trying to tackle a real problem.

Roland R June 15, 2012 06:59

Yes, this is a good idea ;)

All times are GMT -4. The time now is 13:39.