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
[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.