thermal analysis between bodies not in contact

[stef_design]

hi guys, I have a question to ask you on how to set a stationary thermal analysis between bodies non in contact in ansys wb13.
I'll get you an image.
I have a 120°c cylinder. I wanted to know the temperature of the bullet walls.
Hi:

 

[stef_design]

hi to all, I went ahead in the setting of the analysis using also a pdf (Annex).
I applied a temperature bond to the small cylinder (120°c) and of the radiation constraints to the faces of the other two solids. the system of course is all closed, the parallelepiped contains inside the two cylinders.
Where am I wrong?
I also attach the file si ansys wb v13
Thank you:

 

[TheGio]

I do not know very well ansys so I might be wrong but from the pdf you have attached it seems to me to understand that you have assigned to the outer surface of the intermediate cylinder and to the inside of the box of the radiant properties, leaving however to do as with the external supericie of the hot cylinder and the inside of the intermediate cylinder.
heat exchange occurs in two steps:
Hot Cylinder Cylinder Intermediate Cylinder
intermediate cylinder-box
So there are 4 radiant surfaces!

 

[stef_design]

I do not know very well ansys so I might be wrong but from the pdf you have attached it seems to me to understand that you have assigned to the outer surface of the intermediate cylinder and to the inside of the box of the radiant properties, leaving however to do as with the external supericie of the hot cylinder and the inside of the intermediate cylinder.
heat exchange occurs in two steps:
Hot Cylinder Cylinder Intermediate Cylinder
intermediate cylinder-box
So there are 4 radiant surfaces!

thank you young people for the attention.
It could be as you say, now I try and let you know.
I had followed this image and the pdf attached above.
does not seem to have applied radiant properties even to the small cylinder that emanates heat in the center. What are you talking about?
Hi.

 

[stef_design]

I did the test.
cylinder temperature 120°C
temperature ambiene 23°c

I don't know if it's right... shouldn't you see a "zebrature" of temperatures and not two distinct colors (blue and red)?

 

[TheGio]

irradiation allows heat transmission from one surface to another, but has nothing to do with the temperature gradient inside the body (zebrature).
to be able to appreciate the temperature change within the body it is necessary to assign to each body a material and therefore its thermal conductivity.
I can't be more precise.

 

[stef_design]

irradiation allows heat transmission from one surface to another, but has nothing to do with the temperature gradient inside the body (zebrature).
to be able to appreciate the temperature change within the body it is necessary to assign to each body a material and therefore its thermal conductivity.
I can't be more precise.

OK, I press that I have already assigned a material to the two bodies (steel). If I apply two sided surfaces, I should at least see a "smooth" of the temperature plus the two surfaces move away.
For example:
if the body is at 100°c plus the body b (and therefore its surfaces) is distant from to and more the temperature should descend.
then the surfaces near to will be red, those distant blue. everything then goes to fade.
Right?

 

[TheGio]

if the body is at 100°c plus the body b (and therefore its surfaces) is distant from to and more the temperature should descend.
then the surfaces near to will be red, those distant blue. everything then goes to fade.
Right?

depends on the middle between the bodies (empty air, other gases).
in the presence of vacuum, for example, the effect of radiation should be independent from the distance, in the presence of air I do not know....

But do they extract that in the image you posted do not see mesh? ?

 

[stef_design]

depends on the middle between the bodies (empty air, other gases).
in the presence of vacuum, for example, the effect of radiation should be independent from the distance, in the presence of air I do not know....

But do they extract that in the image you posted do not see mesh? ?

to simplify the analysis there is nothing between the 2 bodies (only the vacuum).
to consider the air should:
1-model a solid between the two bodies
2-apply air properties (density, specific heat and cond.termic)
3-enforce conduction constraints between the various surfaces (and not irradiation)

according to you how did the analysis set above (that of pdf with 3 bodies)?
Thank you.

 

[TheGio]

according to you how did the analysis set above (that of pdf with 3 bodies)?
Thank you.

I don't know well ansys.

the strange thing is that in the outer cylinder there is not even a decrease in temperature moving towards the outside as if in the analysis it is not considered the conduction

 

[stef_design]

as if in the analysis is not considered the conduction

In fact, I did not consider the conduction but only the radiation.
to the model I applied only radiation constraints:
between the outer surface of the small cylinder and the inner surface of the large cylinder.

 

[TheGio]

In fact, I did not consider the conduction but only the radiation.
to the model I applied only radiation constraints:
between the outer surface of the small cylinder and the inner surface of the large cylinder.

I did not mean conduction between the two bodies, I meant conduction within the body itself, if a certain amount of heat is removed on the internal surface for the phenomenon of the conduction you should see a gradient of temperature outwards.

 

[stef_design]

I did not mean conduction between the two bodies, I meant conduction within the body itself, if a certain amount of heat is removed on the internal surface for the phenomenon of the conduction you should see a gradient of temperature outwards.

looking at the image there is a slight gradient of temperature.

but between the two cylinders there is the vacuum (I didn't shape the air). therefore in theory the gradient should be almost constant. No?

 

[TheGio]

Oh, here you are!
the temperature differences were not appreciated in the images before.
you should try to hide the piece at 120° and change the display scale

a question:
Can it be that the analysis is right, did you make preliminary accounts to know what results you expect?

 

[stef_design]

Oh, here you are!
a question:
Can it be that the analysis is right, did you make preliminary accounts to know what results you expect?

You're right, I didn't make two accounts in time.
This is an experiment to see if I could then apply the concept to a more complicated model. for matters of time I have not dealt with the problem analytically.

theoretically if I have the vacuum between two bodies the gradient is almost constant.
in fact if I insert the air (i.e. I create a solid and give the properties of the air) I have a gradient + diversified.