[salvo-K61IC]

Hello guys,

i want to share with you my case. I am making a new post because i did not find anything from all the threads i saw in this Forum, i really hope that someone will be interesting to solve problem together!

I USE SALOME 6.6.0 FOR MESHES AND OPENFOAM 2.3.X

I have to study a simple heat transfer between two spheres suspended in the air in a box (or room) as you can see from the pictures in the following link:

http://imagizer.imageshack.us/a/img661/3933/3stE7n.png
http://imageshack.com/a/img537/559/couMpy.png

The sphere 1 is at 300K the bridge (blue cylinder) at 400 K and the sphere 2 at 400 K and they are suspended in the air for example in a room or in a box.

I want to study the heat transfer from the sphere 2 to the sphere 1 through the bridge which shares the two surfaces with them .

I started making a search and i found that a good solver for this case could be chtMultiRegion. I chose chtMultiRegionSimpleFoam so i started with the a simple case (1 sphere suspended in the air) with a flow over the sphere and it works perfectly, but in this case which i am sharing with you i have natural convection...

So my case is actually a natural convection let's say in a room or box due to the heat transfer between the sphere 1 and sphere 2

(in my domain i defined 4 fixedWall which are the walls of the room)

My BC on the walls are:


fixedWall

T : zeroGradient
P: zeroGradient
P_rgh: zeroGradient
U: fixedValue
uniform (0 0 0)

in the folder costant i changed the direction of g (9.81) and it is directed downwards as the z axe (the longer side of the box).

So finally my questions are:

1. Why do not i get i good result with these BCs ?
2. Do you think that should i change the solver ? But as you can see
http://imageshack.com/a/img901/7827/AGlbOE.png
the cht is made also for buoyant cases
3. What do you think about my case ?

I wanna remark that i am just interested to study the heat transfer between the spheres without convective flux (natural convection)

Please i would like to have same help because i worked for weeks getting anything good. I did not upload my whole case, if are interested i ll send you by email or i ll attach here as a attachment.

Thank you in advance

best regards

Salvo

[Micha69822]

Hy,

can you explan your Problems exactly? What isn't good?

In the P-file I would put all parameters to "calculated".

I sent you an message to send me your file. I'll have a look on it.

Originally Posted by salvo-K61IC

Hello guys,

i want to share with you my case. I am making a new post because i did not find anything from all the threads i saw in this Forum, i really hope that someone will be interesting to solve problem together!

I USE SALOME 6.6.0 FOR MESHES AND OPENFOAM 2.3.X

I have to study a simple heat transfer between two spheres suspended in the air in a box (or room) as you can see from the pictures in the following link:

http://imagizer.imageshack.us/a/img661/3933/3stE7n.png
http://imageshack.com/a/img537/559/couMpy.png

The sphere 1 is at 300K the bridge (blue cylinder) at 400 K and the sphere 2 at 400 K and they are suspended in the air for example in a room or in a box.

I want to study the heat transfer from the sphere 2 to the sphere 1 through the bridge which shares the two surfaces with them .

I started making a search and i found that a good solver for this case could be chtMultiRegion. I chose chtMultiRegionSimpleFoam so i started with the a simple case (1 sphere suspended in the air) with a flow over the sphere and it works perfectly, but in this case which i am sharing with you i have natural convection...

So my case is actually a natural convection let's say in a room or box due to the heat transfer between the sphere 1 and sphere 2

(in my domain i defined 4 fixedWall which are the walls of the room)

My BC on the walls are:


fixedWall

T : zeroGradient
P: zeroGradient
P_rgh: zeroGradient
U: fixedValue
uniform (0 0 0)

in the folder costant i changed the direction of g (9.81) and it is directed downwards as the z axe (the longer side of the box).

So finally my questions are:

1. Why do not i get i good result with these BCs ?
2. Do you think that should i change the solver ? But as you can see
http://imageshack.com/a/img901/7827/AGlbOE.png
the cht is made also for buoyant cases
3. What do you think about my case ?

I wanna remark that i am just interested to study the heat transfer between the spheres without convective flux (natural convection)

Please i would like to have same help because i worked for weeks getting anything good. I did not upload my whole case, if are interested i ll send you by email or i ll attach here as a attachment.

Thank you in advance

best regards

Salvo

[zfaraday]

You chose the proper solver for your case, but remember: chtMultiRegionSimpleFoam is for steady state and chtMultiRegionFoam is for time-depending evolutions.

What kind of bad results are you getting with this configuration?

Cheers,

Alex

[salvo-K61IC]

Hi zfaraday,

thank you for your reply!

I am not sure with the BCs that i used... I do not know if in this room a have to use 6 walls or i have to use inlet and outlet and 4 walls to make it converge, but actually i am just interested the the heat transfer from the hot sfere to the cold sphere. Which BCs do u suggest me? if u want to have a look i can send u the case

thank you in advance

best regards
salvo

[zfaraday]

Send me your case and I will take a look when I have time (I don't know if I will be able to do it this weekend...).

alexx.roque@gmail.com