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Two different HTC values in a single anular pipe

Question asked by Simone Storace on Mar 26, 2015
Latest reply on Apr 23, 2015 by Jared Conway

Good morning,

I have a problem / doubt.

I want to post-process some HTC values (heat transfert coefficient) in a CFD model.

The CAD is very simple, two concentric pipes in which steam evolves (an image is appended).

The boundary conditions are:

- Mass flow inlet = 30 kg/s (steam)

- Inlet temperature = 735 K

- Inlet Pressure = 102 absolute bar

- Outlet Pressure = 101 absolute bar

 

Results:

[FACE1] External pipe External face = 100 w/(m2 k) imposed in General Settings

[FACE2] External pipe Internal face = 5000 w/(m2 k)

[FACE3] Internal pipe External face = 400 w/(m2 k)

[FACE4] Internal pipe Internal face = 320 w/(m2 k)

 

How is it possbile that Face 2 and Face 3 have so different HTC values? They are 2 faces seeing "each other" and the steam-flowing on them is the same (same velocity, same temperature, same density, etc...).

Obviously there is a bit temperature difference on the two pipes (4/5 kelvin), but I do not think that it could be the cause of theese unusual HTC values.

 

Thank you

Greetings,

Simone

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