Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.
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.
Difference between 2 tutorials; identifier and pressure in the p list
Posted 28 mai 2012, 16:22 UTC−4 Fluid & Heat, Computational Fluid Dynamics (CFD), Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.2a 0 Replies
Please login with a confirmed email address before reporting spam
I am practising COMSOL 4.2a. I learned two tutorials named "Turbulent Flow Through a Shell-and-Tube Heat Exchanger" and "Non-Isothermal Heat Exchanger". In the first one, the flow passes an array of tubes. Meanwhile, the flow is through the tube in the second one. I found that we have to specify the temperature of the tube in the first one. However, we do not need to specify the tube wall temperature in the second tutorial. Why? I think we should define the wall temperature, shouldn't we?
In addition, I am modeling the non-isothermal flow. I tried to follow one tutorial, so in the Model Builder window I went to the Settings for Fluid and from the p list I chose 'Pressure (nift/fluid I)'. However I do not know the reason to do this step. Can anyone explain to me why we need this step?
Furthermore, I tried to specify the Volume Force in my non-isothermal flow modeling. I want it to be the variable-density flow with Buoyancy effect (meaning not only the volumetric source term, but allow the density to change in other terms of the governing equations too). So I added 'g_const*pA*R_air/T’ as my Volume Force, where R_air is the constant I created. However, when I computed, there was some error message. So I have not have a chance to see the result. I have two questions for this. First, does this make my model be the variable-density flow? If it doesn’t, how to make it be? Second, when will we need to use ‘nift.pA’ and when can we use ‘pA’ as the identifier instead?
Thank you very much.
Best regards,
Atit
Hello Atit Koonsrisuk
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.