[chinna]

Hai, Im simulating heat exchanger as the hot fluid in the tube and the cold fluid in shell. At first i close the flow path with caps and fill them in Geometry stage and suppress the caps. When i reach Fluent setup, it requires 3 walls setups,
1- tube which is internal fluid wall
2-external fluid, 1 for the outer wall and 1 for the inner wall which in shape of tube.
I tried setup the both walls (tube and external fluid inner wall) as shell conduction by dividing the thickness of the tube i wanted to simulate. Fluent solve it, however I think there is error in my results because of the setup. Can anyone please help me...?? is there anyways to combine the walls or any other ways to simulate this...???

[vasava]

Do you mean you want to set-up the interface between fluid and solid?

[chinna]

yes... and by the way..i didn`t mesh the solid tube, i just activate the shell conduction under convection..is it correct..??

[vasava]

I have no experiences with shell conduction so no comments on that part. If you need to make an interface here are the steps.

1. Subtract the inner object from the outer one.
2. Just mesh the whole model and ansys meshing program will take care of the interface.
3. When you import the mesh in to fluent remember to enable coupling in the interface section. Otherwise no heat-transfer will not occur.

[chinna]

okey..thank you... i try as u said then

[chinna]

Sir, now im facing a problem..is there any ways to avoid this error...
Note: zone-surface: cannot create surface from sliding interface zone.
Creating empty surface.

[vasava]

This may happen if you do not declare your domains as fluids during mesh generation.

[vasava]

One easy way to verify if the interface has been created properly is to see if there is an additional boundary named 'interior' created. See the picture.

[chinna]

ok sir..thank u..its settle..
sir, im planing on doing periodic heat transfer in heat exchanger... as for interval 10min, 20min,...
as in user guide anasys fluent, its says edit Periodic Conditions under boundary sondition..however that option not active in my case.. how to solve it Sir???
thanks alot for your time sir.

[chinna]

Sir, every time i reopen fluent that i did earlier, the interface boundary is missing sir, the shadow wall and shows...
Error: inquire-adjacent-threads: wrong type argument[1] (thread)
Error Object: #f
is there anyways to prevent this..??

[vasava]

First of all no 'sir' please. I am an Indian and British wont be happy about you calling me sir......... :-)

Anyways, this error is new for me. You can re-create the case but make sure that you declare domain type 'fluid' during meshing process.

If the problem persists than I am afraid I can not help you any more (about this error). Feel free to ask more.

[chinna]

ok...thank you... and i wont
how about the periodic heat transfer...?? i want to measure how much the cold fluid temperature rise in certain period of time.. i tried set the interface as periodic but its failed... is there any other way to solve it??

[vasava]

By periodic you mean heat transfer with time-dependent boundary conditions right?

For doing so, you can run a transient simulation. I think you are confused between the 'periodic' nature of the domain and periodic boundary condition. A periodic domain repeat itself after certain length or angle, and a periodic boundary condition (that you implement on a boundary) is like a pulse that repeat after certain time period.

[chinna]

yes.. i meant time dependent boundary conditions..thank you, i`m clear now...i start working on transient simulation setup..hope it will end up gud..

[chinna]

The solution diverge with the error as below... i tried to change the solution method, yet it diverge some how..
i don't really understand what its meant by increasing relaxation sweeps.however i just tried reduced the relaxation of the minimum static temperature from 1K to 0.5K.... and it diverge after about 30+ iteration compare to before... is there any ways to solve it?? or should i reduce the minimum static temperature?

# Divergence detected in AMG solver: temperature -> increasing relaxation sweeps!

Error: Divergence detected in AMG solver: temperature
Error Object: #f

[chinna]

Hai, Im bit curious about how to analyse or how should i analyse the data to finalize the answer. im varying the velocity, materiel and the shapes of the tube. i need to find an optimum material, shape and velocity for the heat exchanger.