Problem with modelling heat exchanger(fluid-solid-fluid-solid)
 

hi all
I am trying to model a simple heat exchanger,I want to see the temperature change between the two fluids and across the wall.
I create the geometry and mesh with the gambit,and Analys it with fluent,but flow temperetures,not changes,
T(inlet,cold water)=T(outlet,cold water)
T(inlet,hot water)=T(outlet,hot water)
i think my problem is boundery condition.
I upload gambit files
I hoped that some people on this forum would be able to help with a few issues I am having
please help me
thanks
http://www.4shared.com/file/PTHRtFi2/g-f.html (dbs format)
http://www.4shared.com/file/QZ2PFaij/g-f.html (mesh file)

Can you post some pictures of the setup?
Yes, this sounds like some b.c. problem. What are you using? How did you mesh the solid body?

i mesh model with gambit,and upload gambit and mesh file...

The mesh file doesn't show your fluent settings. Also, I am at work and can't download files from mysterious places.

upload all b.c?
if i upload cas and data file(fluent file),can u download them?

Did you also set the material of the inner pipe to "solid, aluminium"? I can't see it on the picture, but you have some gridpoints in the solid (inner) part, right?

I upload a new pic,
material of the iner pipe and outer pipe set to "solid, aluminium
iner flow inlet: v=0.5
T=370k
outer flow inlet: v=0.5
T=275
i mesh iner flow,outer flow,iner pipe and outer pipe
one question,what b.c set for the wall of iner pipe?(neighboring water)

You need to set both sides of the inner pipe to "coupled" for the thermal b.c.

Why is the inner fluid mesh so coarse?

i improve the mesh and set both sides of the inner pipe to coupled
but the tempreture not change...
):

Did you also set the material property of the solid? I don't know what material is the default setting. Go to "Cell Zone Conditions" -> your solid body under "Zone" and see, if the "Type" is solid. Also click on "Edit..." and see, if the material is aluminium.

yes,i do it

Hmmm... is the mesh conformal at all transitions fluid->solid->fluid?

Also: Did you set both "wall:013" and "wall:013-shadow" to coupled, for both sides of the pipe? I don't know the meaning of these, but I just had a look at some old case and saw, that I did it there.

yes
there is no conduction heat transfer acroas the iner pipe,but i dont know why..!!
:confused:

1) Yes to post #12 or #13?
2) Create a line perpendicular to the pipe and make an XY plot of temperature. Can you post it?
3) How is your y+ at all walls?

i coupled both "wall:013" and "wall:013-shadow",but maybe i do it wrong
pleace say how can i couple walls...

wall:013 and wall:130-shadow are both the same wall. It is on one side of the inner cylinder. You also need to set the "coupled" b.c. to the other side of the inner wall.

Make an XY plot over a line. Not a contour plot.

xy plot: center to outside

Do you have periodic boundary conditions in x-direction?

no,i have'nt
i send u xy plot in y direction