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-   -   Two sided wall boundary condition (http://www.cfd-online.com/Forums/fluent/94375-two-sided-wall-boundary-condition.html)

Kamu November 14, 2011 04:41

Two sided wall boundary condition
 
Hi
I am modeling an interface between a fluid and solid and in ANSYS FLUENT I get a wall and its shadow. I want to specify a heat flux on the wall but it looks like when I do that the heat flux is not conducted to the other wall.

sandeep_tu November 14, 2011 10:33

Hi
Wall and wall shadow are the faces for both domains (solid and fluid), specify the same boundary conditions for both wall and wall shadow, it has to work.

raj.cfd November 14, 2011 11:11

Heat transfer through solid and fluid interface
 
Hi,

As far as I understand from your post, You need to toggle in the coupled option for heat transfer to take place from solid to liquid interface, ie..the wall and the shadow.

Kamu November 15, 2011 00:51

Hi Sandeep_tu,

I tried specifying the same boundary conditions for the two walls but it diverges (AM divergence in temperature). I need to specify a heat flux on the wall. Thanks

Kamu November 15, 2011 00:52

Hi Raj.cfd,

Thanks but with the coupled option there is no way i can specify a heat flux on the wall

sandeep_tu November 15, 2011 07:21

May be this helps, scroll down to Thermal Conditions for Two-Sided Walls:

http://jullio.pe.kr/fluent6.1/help/html/ug/node213.htm

regards
sandeep

laurentb November 16, 2011 02:49

It depends on what you want to do exactly (send a scheme can help us for giving response).
Do you want to compute heat transfer inside the solid zone ? Why do you want to impose heat flux on the wall ?

raj.cfd November 16, 2011 18:19

Hi Kamu,

I dont understand why you want to specify heat flux on the coupled interface ( solid-liquid) . Does you problem has got two volumes, one solid and one fluid connected to each other or how is it....??? . Moreover , if you give a boundary condition on one side of the wall of the solid, it has to transfer heat to the fluid zone. I think you can create a sketch of your computational domain and paste as an image file, only then I will be in a better position to guide you.

Kamu November 23, 2011 07:03

Quote:

Originally Posted by laurentb (Post 332264)
It depends on what you want to do exactly (send a scheme can help us for giving response).
Do you want to compute heat transfer inside the solid zone ? Why do you want to impose heat flux on the wall ?

Hi Laurent,

What I want to do is I have wall with a coating the coating has a different emissivity from the wall and I want to impose a heat flux on the wall so that the wall and the shadow are all transfering heat

laurentb November 23, 2011 07:37

Do you mesh the coating zone ? You can compute the coating as a solid zone or just impose a thermal resistance to model the coating without meshing.

Kamu November 23, 2011 07:47

Hi Raj,

I have a wall onto which there is incident solar radiation that is coated with an anti-emission coating. So I have a heat flux boundary condition on the wall yet the coating has a different emissivity from the wall itself

Thanks

Kamu November 23, 2011 07:51

Hi Laurent,

I actually do not mesh the coating! How do I impose the thermal resistance on it so that it remains coupled to the other wall?

raj.cfd November 28, 2011 17:19

Hi Kamu,

you can probably use shell conduction option available in Fluent. No need to mesh...

Kamu November 29, 2011 08:40

Thanks guys I figured out where the problem was, it is now running well and am getting good results. I converted the heat flux into volumetric generation which I used as a coupled wall source

ashrawage February 15, 2012 00:50

How did you convert the heat flux into the Heat Generation?
 
@ KAMU

Sir,
I have the same issue. So i wanted to know how you solved the issue by the conversion of heat flux into the heat generation.

Please let me know the procedure for doing the conversion.

Thanks

abhijeet

as195810@ohio.edu

Kamu February 15, 2012 01:43

Quote:

Originally Posted by ashrawage (Post 344500)
@ KAMU

Sir,
I have the same issue. So i wanted to know how you solved the issue by the conversion of heat flux into the heat generation.

Please let me know the procedure for doing the conversion.

Thanks

abhijeet

as195810@ohio.edu

I used the basic heat conduction principles to convert the heat flux into heat generation. Get the heat rate in W divide by the volume of the material. I hope this helps.

Kamu February 15, 2012 01:44

I used the basic heat conduction principles to convert the heat flux into heat generation. Get the heat rate in W divide by the volume of the material. I hope this helps.

ashrawage February 15, 2012 12:33

@ kamu
 
@KAMU

I have the Heat load value in W.
Do I divide that with the actual SOLID volume of my tank?
I don't see any logic behind dividing it by the hollow volume that the tank holds , hence i want to make sure.

You see i am supposed to heat the water flowing in a tank using the walls of the tank which are 0.01m thick. I need a steady state solution...i don't care how long it needs to heat the water...as long as it heats it.

But like you said the heat flux is giving me more questions than answers.

Chirag2302 May 2, 2012 01:56

URGENT__convective boundary condition on two sided wall
 
Hello,

I have wall as fluid -solid interface means two sided wall. (wall and its shadow wall in FLUENT).

I have a known temperature gradient on that wall and known heat transfer coefficient for convection heat transfer condition.

Wall has solid as its adjacent cell zone and its shadow has gas as its adjacent cell zone.

As I know, temperature gradient can be define using UDF which is constant with respect to time. Now I want heat transfer between solid and gas

with known fixed value of heat transfer co-efficient.

How to define the boundary condition in the above situation in FLUENT...????

Can anyone help me..????????

Thank you...


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