heat radiation modelling

chubb · March 18, 2010, 05:31

Hi all,

I want to simulate a simple model using STAR-CCM+ that calculates radiation heat transfer in a participating grey gas enclosed between walls. That means there is no convection and no fluid flows.

I have created and imported a cube. The interior of the cube has to be modelled with the surfaces as boundaries.

My problem is, that I don't know which models and options to choose. I clearly want to use the Discrete Ordinate Method (DOM) radiation model, but I am unsure what segregated and coupled flow means. Apart from that I used laminar flow, but I don't really want to simulate any flow at all.

Can you help me?

Vinicius · March 18, 2010, 12:36

Hi Chubb.

The segragated and coupled formulation are imported if you are preocupated with the flow, and they are indicated for different kind of flow. For Radiation, you can select the segregated flow, and selecting the radiation model, more options for radiation will appear, then you select the Participating media Radiation and Gray thermal radiation.

The point that I didn´t understand is what body will be the radiation source, and where do you want to measure the heat flux?

Regards,

Vinicius

chubb · March 18, 2010, 13:00

Hi Vinicius,

the radiation source are e.g. the walls, that is the inside of the cube I have imported. I will give it a temperature, so that it radiates. The participating gas in the interior is e.g. cold at T = 0K.
I want to know the heat flux at different locations inside, e.g. at a centerline of one wall, or in a plane section in the interior.

I know how to do that, my problem is still to get it running without an error after having successfully created a volume mesh.

I use the models you mentioned and stationary, steady, 3dimensional, laminar, constant density.

Vinicius · March 18, 2010, 13:37

hmm, so the flow is important, not for you, but to the convergence. Try to change the model to coupled flow, ideal gas equation and turbulent model (k-e should be fine).

Maybe this is a unsteady problem... try to run as an unsteady too..

chubb · March 19, 2010, 07:52

Ok, I tried what you have said. But the calculation starts and after the line "Calculating grid flux in region Volume Mesh:Region 1" nothing happens even after it runs for a few minutes. I have 65760 cells, that shouldn't be too much in my opinion...
Not even the first iteration of the residuals finishes.

chubb · March 20, 2010, 17:39

Ok, it works now, but only if I choose the boundary condition "convective" for the wall of the cube, instead of "temperature", which I would have liked to choose.
I wonder why I can't use a preset temperature of 500K for the walls and 300K for the medium. Now I try to make the convection as small as possible, so that it doesn't influence the radiation.

March 18, 2010, 05:31	heat radiation modelling	#1
chubb New Member Hubert Chubb Join Date: Mar 2010 Posts: 4 Rep Power: 16	Hi all, I want to simulate a simple model using STAR-CCM+ that calculates radiation heat transfer in a participating grey gas enclosed between walls. That means there is no convection and no fluid flows. I have created and imported a cube. The interior of the cube has to be modelled with the surfaces as boundaries. My problem is, that I don't know which models and options to choose. I clearly want to use the Discrete Ordinate Method (DOM) radiation model, but I am unsure what segregated and coupled flow means. Apart from that I used laminar flow, but I don't really want to simulate any flow at all. Can you help me?

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March 18, 2010, 12:36		#2
Vinicius Member Vinicius Girardi Join Date: Mar 2009 Location: Sao Paulo, Brazil Posts: 80 Rep Power: 17	Hi Chubb. The segragated and coupled formulation are imported if you are preocupated with the flow, and they are indicated for different kind of flow. For Radiation, you can select the segregated flow, and selecting the radiation model, more options for radiation will appear, then you select the Participating media Radiation and Gray thermal radiation. The point that I didn´t understand is what body will be the radiation source, and where do you want to measure the heat flux? Regards, Vinicius

March 18, 2010, 13:00		#3
chubb New Member Hubert Chubb Join Date: Mar 2010 Posts: 4 Rep Power: 16	Hi Vinicius, the radiation source are e.g. the walls, that is the inside of the cube I have imported. I will give it a temperature, so that it radiates. The participating gas in the interior is e.g. cold at T = 0K. I want to know the heat flux at different locations inside, e.g. at a centerline of one wall, or in a plane section in the interior. I know how to do that, my problem is still to get it running without an error after having successfully created a volume mesh. I use the models you mentioned and stationary, steady, 3dimensional, laminar, constant density.

March 18, 2010, 13:37		#4
Vinicius Member Vinicius Girardi Join Date: Mar 2009 Location: Sao Paulo, Brazil Posts: 80 Rep Power: 17	hmm, so the flow is important, not for you, but to the convergence. Try to change the model to coupled flow, ideal gas equation and turbulent model (k-e should be fine). Maybe this is a unsteady problem... try to run as an unsteady too..

March 19, 2010, 07:52		#5
chubb New Member Hubert Chubb Join Date: Mar 2010 Posts: 4 Rep Power: 16	Ok, I tried what you have said. But the calculation starts and after the line "Calculating grid flux in region Volume Mesh:Region 1" nothing happens even after it runs for a few minutes. I have 65760 cells, that shouldn't be too much in my opinion... Not even the first iteration of the residuals finishes.

March 20, 2010, 17:39		#6
chubb New Member Hubert Chubb Join Date: Mar 2010 Posts: 4 Rep Power: 16	Ok, it works now, but only if I choose the boundary condition "convective" for the wall of the cube, instead of "temperature", which I would have liked to choose. I wonder why I can't use a preset temperature of 500K for the walls and 300K for the medium. Now I try to make the convection as small as possible, so that it doesn't influence the radiation.