Menu

Discussion Forum

New Discussion
Filtra

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Temperature not continuous at solid/fluid interface

Posted 30 lug 2015, 22:47 GMT-4 Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD) 2 Replies

LEE
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi everyone,

The case I'm working on is typical conjugate heat transfer. Two tubes are arranged in concentric configuration. The inner tube is heated on the inner surface and cooled by water flowing between the tubes. There is no coating on the surfaces of inner tube that would act as thermal resistance. My purpose is to find out the highest temperature in the cooling water region.

After running some simple tests (Reynolds number is >10000), I have found that when the k-episilon turbulence model is used, the temperature is not continuous at the solid/fluid interface. However, there is no such a problem when I change to laminar flow model.

So, here are my questions.
1. When I try to estimate the highest temperature in the cooling water region from turbulence model, it turns out the results given by the surface maximum and volume maximum functions are not the same (I made sure only the boundaries or the domain of cooling water region are selected). Since my concern is the highest temperature in fluid, which value should I trust?

2. Is the result of discontinuous temperature from k-episilon model caused by the adoption of wall function because the viscous sublayer is not considered? If this is true, can I solve this problem by using Low Reynolds number turbulence model instead, since it solve the Navier-Stokes equations all the way down to the wall?

Any comment would be highly appreciated and thanks for anyone's kind help in advance.
2 Replies Last Post 22 dic 2016, 03:45 GMT-5
COMSOL Moderator

Hello LEE

Your Discussion has gone 30 days without a reply. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help.

If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base.

Emilio Codecido
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 8 years ago 21 dic 2016, 09:50 GMT-5
I'm having a similar issue. Did you figure out the problem/explanation? Please let me know, thanks.
I'm having a similar issue. Did you figure out the problem/explanation? Please let me know, thanks.
Frank van Gool COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 8 years ago 22 dic 2016, 03:45 GMT-5
Dear How ming, you are correct with point 2, the k-eps model uses wall functions, which causes the discontinuous temperature field.
If you use a turbulence model without wall functions, it will be continuous from the fluid to the wall.
Best regards,
Frank
Dear How ming, you are correct with point 2, the k-eps model uses wall functions, which causes the discontinuous temperature field. If you use a turbulence model without wall functions, it will be continuous from the fluid to the wall. Best regards, Frank

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content