Heat transfer between fluid-solid domains doesn't occur
 

Hello. I want to do a 3-D simulation of a periodic cell of a printed circuit heat exchanger. The geometric model consists in a prismatic solid domain with two wavy channels (semicircular cross-section) for the circulation of a hot fluid (up) and a cold fluid (down), in counterflow. I have meshed the model in Gambit, with 3 final volume meshes (2 for the fluids and 1 for the solid), and periodic conditions in the up, down, right and left faces of the solid domain. I put velocity-inlet and pressure-outlet boundary conditions for both fluids, with inlet-outlet temperatures, and I also put as interfaces the fluid and solid faces which are in contact.

Then I exported the mesh to Ansys Fluent 12. The solid material is stainless steel and the hot and cold fluids are air.

Well, I created two "mesh interface", with the option coupled wall; one between the solid and the hot fluid interfaces and other between the solid and the cold fluid interfaces.

Once the case is solved, the fluid dynamics solution seems correct, but there is no thermal coupling between the domains. There is no heat transfer from the hot fluid to the solid and from the solid to the cold fluid.

I see that several boundary condition (walls) are created with the two "mesh interfaces". Two are, in example, wall-20 and wall-20-shadow, one for the hot fluid and the other for the solid, which show "coupled" selected in the thermal tab, when you edit them. The same occurs for the cold fluid and the solid interfaces. But other 4 different walls are also created, 2 for the solid and 1 for each fluid, which show "Heat flux = 0" in their thermal tabs. This appears very strange to me.

Can anybody help me?

Many thanks in advance.

Unfortunately, I do not have a solution for you. I am incurring the same problem with my model - fluid dynamics have converged successfully but no heat transfer between fluid/solids.

As I see it, there are two possible problems. Either the mesh is not being created in a way that the mesh from the fluid domain lines up with the solid domain, or Fluent has not received sufficient information to "know" to solve for heat transfer between the domains.

I am not using Gambit, I am using the built in meshing tool from Ansys workbench.

Does anyone know a way to check that the mesh is consistent at the boundaries between a fluid domain and a solid domain?

Does anyone know if special boundary conditions must be specified for fluid/solid boundaries?

I'm having the exact same problem, and I THINK I've heard that Fluent can't do transient conduction. Can anybody verify this?

Gentlemen, I have discovered what our (my) problem is. You need to define in Fluent an interface between the solid and fluid regions.

-Create a surface in your meshing program that occupies the entire interface between the solid and fluid boundary.
-In Fluent, under boundary conditions, set the boundary type for the interface to "interface"
-Under the "mesh interfaces" you will need to create/edit to make a mesh interface

Now when you run the simulation, it should simulate convection between them. Let me know if you are still having problems.

hi,
you can do what justin does, but a simpler and faster solution is as follows:
make mesh in a meshing software and make three domains (2 for fluids and one for solid). set all interfaces between solid and fluid to wall. dont forget that you MUST have ONLY one face in each interface, not two faces. then the only face in each interface should be used by two volumes(one side is solid and one is fluid).
if you are correct upto this, after exporting mesh to fluent, you should see a -shadow boundary condition of type wall for each interface wall. it is ok. one has fluid as adjacent zone and one has solid as adjacent zone. by default these two walls are coupled in thermal conditions. so just specify zone materials, velocity and pressures ion boundaries and solve the problem.(dont forget about enabling heat equation at the first step after importing mesh in fluent.)
yours,
mohammad

Yeah, I did it the way Mohammad suggested and that seems to be working for me. Now if I could just get my UDF to compile....... (I'll save that for another thread.)

Thank you all!

hi mohammad
i do what you said but it seems that fluent is not able to couple heat transfer between solid and fluid.
my project is about railway brake disk cooling.
I need your help.
my mail: behnam67gh@yahoo.com
thanks a lot
Behnam Ghadimi

heat transfer between Solid and fluid domains
 

Hi all,
I have a cylinder in which water flows. I could able to see the conduction for the cylinder but not the convection in to water.
1. Do i need to supply the convection rate?
2. How to maintain conjugate contact between the interface.

In meshing I could see contact between the two surfaces(solid and fluid), but that connection I cannot see in boundary conditions.

Can some one help me..
Thanks alot for reading

Hi Sree
To maintain conjugate contact you should define the interface as wall in Gambit and mesh both (solid and fluid) zone. Note that you should have only one surface between domains and define it as a wall. when you are read mesh file in fluent, Fluent add another wall as shadow wall. if you see the shadow wall in fluent, the heat transfer between solid and fluid is coupled.
Good Luck

Heat Transfer
 

Hi,

My problem is similar but the only difference is that i have to apply heat flux on one side of the wall. That i have done and running but conduction in between the two sides of the wall is not happening.What should I do???

Thanking You

Heat transfer between fluid and solid
 

Hi all,
I have a sphere fluid flow in a channel.
I want to study conduction in the sphere
1) I create 2 zone ( 1 fluid zone and 2 for solid zone (sphere)).
2) I set all interfaces between solid and fluid to wall.
3) After exporting mesh to fluent, I see a -shadow boundary condition of type wall for each interface wall.
4) I enable heat equation. (knowing that the two wall are coupled)

But the problem after running simulation there no transfers conjugate between fluid and solid the temperature of solid remains stable (initial temperature).


Best Regards...

Tumble,

I am doing a similar problem, I think what you have to do is set the wall to an interface in Fluent, then create a "Mesh Interface" and this should solve your problem.

how to define interface
 

how to define interface between fluid and solid region for shell and tube heat exchanger.

A really simple solution would be to create a body (in ICEM) anywhere within the fluid (or domain of interest). After this step I exported my mesh using FLUENT and I did not have any problems with shadow walls.

I hope this helps.

Shadow wall
 

Hi every body
Please see below links:
1. http://web.stanford.edu/class/me469b...s/physical.pdf
2. http://aerojet.engr.ucdavis.edu/flue...ug/node567.htm

cylinder
 

hi every one i have same problem.
in my fluent show shadow of interior wall(middle shadow) ,but it don't work.
in gambit i have two zone water flow in cylinder and air of environment.when hot flow pass the cylinder ,air don't have any changes.
the image is attached.:confused::confused::(
http://8pic.ir/images/r08qlwh567aaaooowcm6.jpg

Once again
 

Hello good people,

I'd liike to ask if somebody could explain the steps in creating this couple wall b.c more clearly

What I have is two bodies - fluid and solid, one of solid's wall is hot, I wanna see how much the fluid heats up, the solid does not cover the whole fluid domain - it works like plate heat exchanger and the inlet's and outlet's solid domain is not defined, only the part governing heat transfer

what I do is:

1/ When I create no named selections in mesher fluent creates a lot of walls and less shadow walls (chich is correct), but I cannot display the ones that are overlapping with connections, which are present in the mesher.

2. If i create named selection corresponding to the interface between solid and fluid, fluent oes not create ny shadow interface part ;<

Kind regards,
Pawel

No special treatment is needed at a fluid-solid interface. As long as your zones are well defined in your mesh, Fluent creates a wall/wall-shadow at the interface and heat transfer will occur across the wall.

If there is (almost) no heat transfer across the wall/wall-shadow, it's probably because of the physics of the problem. Run the same simulation for a longer time or modify thermal properties (k, Cp) in order to validate that heat transfer occurs.

ok but there will be heat transfer between solind and fluid even though there is no shaow walls in boundary condtitions panel?

and what about thermal boundary condition for fluid domain walls? ;(

If Fluent doesn't automatically create a wall/wall-shadow, you have to redo the mesh, zone definition, etc., until you get a wall/wall-shadow.

The thermal conditions for both wall/wall-shadow are set to 'coupled' by default and you keep it like that, see picture.

Hi guys! I read about the problems you had with simulating a coupled conduction-convection problem in fluent.
By making several attempts, before reading your posts, i found out that no thermal exchange between fluid and solid is visible with the pressure-based solver (I only have standards interfaces between solid and fluid and the problem was well solved in a steady state fashion), but if I use the density based, then something seems to happen.
Did you notice simething like this in your cases?

solar collector
 

hello this is the first time i write in this forum, and i have just join.
i have problem with Ansys Fluent about heat transfer between solid material ( the isolation, the collector) and outside environment. in the inside of solar collector there are carbon to adsorb methanol form the evaporator. i am using 2D transient model. the iterating process did work but the result didn't occur. could anyone give any suggestion or help.

best regards

not getting shadow region
 

hello all,
I am trying to design a shell and tube heat exchanger and am using hypermesh to mesh a section of it. I define all my zones and faces as explained in previous posts to this thread, but when I bring the case into fluent, the shadow zone does not get created for the pipes. therefore, when i try to run it, there is no heat transfer. i have tried different meshing methods in hypermesh, but can't get the shadow zone to appear. does anyone have any tips or suggestions?

Hi sara
to couple walls you should define the interface as wall in Gambit and mesh both (solid and fluid) zone. Note that you should have only one surface between domains and define it as a wall. when you are read mesh file in fluent, Fluent add another wall as shadow wall. if you see the shadow wall in fluent, the heat transfer between solid and fluid is coupled.if u dont see the shadow go to wall interfaces in fluent and select the wall between two zone and shadow will appear.good luck

Hi every one
I want to ask how to in put sulfinol and steam material in fluent

Same Issue with StarCCM+
 

I'm having this same issue in StarCCM+. I have a cylindrical sample emitting total heat of 500 W in a cylindrical case filled with air. There is no heat transfer between the air and the cylindrical case (fluid to solid regions).
Has anyone had this issue in StarCCM+ and found a solution?
There are interfaces between all mating surfaces with conjugate heat transfer applied.

Thank you!

Heat Transfer between solid and fluid zone
 

hello every one,
i face problem there is no heat convection between solid zone and fluid zone.
i design a plate heat exchanger,
creat mesh in ICEM
import in fluent and define the boundary condition and also shadow surface as coupled but there is no heat transfer between the two zone.
one side is hot fluid on other side is cold fluid but no transfer of heat from hot to cold fluid through solid zone. Solid zone is steel and fluid is water.
so please gib=ve some suggession on it.

Hello,

I am new to fluent and am trying to model continuous casting.A shadow wall is being created by fluent in the two region interface.The contact resistance should be applied to the shadow wall or the inner wall in order to model the conduction between mould and billet.

You can make new coupled wall between solid-zones in Fluent. You don't have alter the mesh.

Just use the text-command mesh/modify-zones/slit-interior-between-diff-solids.

After this, you have to change the thermal option in these new walls (and shadow walls) to coupled.

Sorry for re-posting!
There are two zones in my model,fluid and solid,a shadow wall is created between them automatically by fluent. Now my question is whether i should assign the shadow wall with material properties of solid or fluid?

If there is nothing between your two zones, put same options for both wall and shadow-wall:
- coupled heat
- thickness 0 m (-> materiar properties don't matter)

Problem is more complex if you want to model some thin layer between your zones.

Thank u :)

Fluid Solid heat transfer problem
 

Can anyone suggest any video tutorial depicting simple heat transfer between solid and fluid zones in Ansys Fluent. In my simulation there seems to be no heat transfer between fluid and solid. I have already tried with coupled wall but that doesn't seem to work.

check your units, when u import mesh to fluent it consider the units as meter

Good morning mohammad sir

I'm also facing the same problem. I'm working on a solidification model. I have filled liquid metal in the cavity with the solid. Two wall (one wall and wall shadow) are there. I have coupled them in thermal tab. I have given constant density, Sp. heat capacity and all other properties. One of the property as thermal conductivity I have given variation with temperature.
But there are no heat transfer after calculation.

Please guide me and give your valuable suggestions.

Thanks & Regards
Sandeep