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Jonny6001 September 22, 2010 09:33

Heat transfer through solid
Hello, I am very new with Star CCM but so far I'm very impressed compared with Fluent, regaring the structure of the software.

Firstly I am looking at modelling a pipe with hot gases inside and ambient temperature on the outside, with the aim of predicting the temperatures in the actual solid pipe rather than the gases.

The way I have approached this is to model each flow region separately and mesh them individualy and save them as .ccm files. Then bring all 3 regions in to a new simulation and work on them from there.
I have contact interfaces between the solid and internal gas, and the solid and external ambient air.

I have ran the case and the fluid regions seem to behave as expected but the solid region has more or less a constant bulk temperature. I would expect the region to show a temperature gradient relative to the internal and ambient temperatures.
I think there is a "thermal specification" setting for the interfaces that can be altered but I am unsure what they should be, at present I have them set to adiabatic where I could chose "temperature, heat flux, convective".

One thing that Fluent does well is provides very good manuals about exactly what settings do and how they alter the solution.

I hope someone can give me some help.

Thanks a lot.

nomad September 23, 2010 12:46

What's the pipe material, how thin is it?
If it's a highly conductive pipe, then there might not be a noticeable gradient across it. Did you crop the temperature scale to a few degrees or even less to see if there is a gradient?

Jonny6001 October 3, 2010 09:35

Hello, sorry for replying late, have been away for a while.

I quickly realized the issue, the external wall had been set to adiabatic condition so the wall temperature was obviously going to match the gas it was in contact with once the system had reached steady state.

Does anyone know how the local nusselt number is used in a heat transfer situation? I mean, the heat transfer from hot gas running through a pipe is going to be dependant on the flow characteristics,so areas of slower gas will have different transfer to quicker and turbulent areas will be different again.

I am unsure how this is treated in Star CCM+ and how is best to model the situation.

Thanks a lot.

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