Discussion Forum

Posted: 1 decade ago Oct 2, 2012, 8:09 a.m. EDT

COMSOL imposes temperature continuity at the fluid-structure boundary in a conjugate heat transfer problem. There is no need for a different thermal boundary condition there. That boundary condition accounts directly for heat loss from the solid through conduction and the fluid flow that results accounts for convection. Nagi Elabbasi Veryst Engineering

Posted: 1 decade ago Oct 3, 2012, 1:45 a.m. EDT

thanks ....thanks a lot. rgds Anup

Posted: 1 decade ago Nov 4, 2012, 6:03 a.m. EST

Daer Nagi Its fine that comsol itself taking care of interface boundary condition as heat loss from the solid. However, in my problem the solid is under laser heating (consider as a volumetric heat generation based on Beer-Lambert law)in which i am defining optical properties for solid as well as for fluid such that fluid light absorption characteristic is greater than that of solid. I should get a maximum temperature in the fluid domain not in the solid domain because of higher light absorption characteristic of fluid. But , results shows exactly opposite. The max temp is obtained at the solid domain rather than fluid. If my explanation is correct, how to resolve this issue? rgds Anup

Posted: 1 decade ago Nov 4, 2012, 1:10 p.m. EST

Hi Anup, Whether solid or fluid gets higher temperature depends also on the distance the laser travels through them as well (not just their absorption characteristics). I don’t think any special treatment is needed at the fluid-solid boundary. You just need to add the volumetric heat source to fluid and solid domains separately. Nagi Elabbasi Veryst Engineering

Posted: 1 decade ago Nov 9, 2012, 8:20 a.m. EST

thanks rgds Anup

Posted: 1 decade ago Feb 15, 2013, 12:55 a.m. EST

Dear Nagi, I need an immediate help for the thread : www.comsol.com/community/forums/general/thread/34647/ I am somewhere stuck up in meshing part, thus, request you to please reply. -- Ishant Jain

Posted: 1 decade ago Aug 7, 2013, 7:10 a.m. EDT

Dear friends I am solving for transient case for total time of 300secs with time step of 0.1sec [free time step (not strict)]. The time-dependent solver result (for your reference) is attached herewith. Now under step size, some times it appears "out" and sometimes different values. What does it mean? rgds anup

Attachments:

• Time.pdf

Posted: 1 decade ago Feb 20, 2014, 10:08 p.m. EST

[QUOTE] COMSOL imposes temperature continuity at the fluid-structure boundary in a conjugate heat transfer problem. There is no need for a different thermal boundary condition there. That boundary condition accounts directly for heat loss from the solid through conduction and the fluid flow that results accounts for convection. Nagi Elabbasi Veryst Engineering [/QUOTE] Dear Dr. Elabbasi, I am doing a simulation on the heat ans mass transfer in some grains using both the conjugate heat transfer in solids (nitf) and transport of diluted species (chds). The simulation for the heat transfer is quiet good but the not in the mass transport. Maybe there are some issues on the type of mesh that I am using. Anyway, I'll just leave it at that for the moment. What I would like to inquire right now is the problem on the heat loss due to evaporation. The passing of the heat air to the surface of the solid boundary caused heat and mass transfer at the same time resulting to some degree of heat loss. Does the nitf node of COMSOL account for this loss? Because I want to consider the heat loss, I tried adding the convective cooling. However, I am having some problems because the boundaries of the grains are inactive (Attached picture). Am I doing it correctly? Is there any other way to do this so that the heat loss can be included in the analysis? Thank you very much in advance. Beat regards, Jonathan Perez

Attachments:

• Inquiry to Dr. Elabbasi.PNG

Posted: 9 years ago Sep 3, 2015, 4:39 a.m. EDT

Hi everybody, please how comsol assume, boundary at solid-solid Interface? In my simualtion the thin film is irradiated by a laser beam, and the substrate is transparent to the wavelenght. How to set flux and temperature continuity at interface. Thanks.

Posted: 8 years ago Aug 10, 2016, 12:44 p.m. EDT

Hi!! please help me my model is solid with heat flux on the upper face and fluid moving under the lower face , I used Conjugate heat transfer ,but the result show that there are no heat transfer between solid and liquid!!

Posted: 8 years ago Aug 10, 2016, 11:32 p.m. EDT

hello. much better if you upload your file for the other members to comment and have their suggestions.