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Joule Heating and Laminar Flow in microfluidics

Posted 19 févr. 2013, 15:58 UTC−5 Low-Frequency Electromagnetics, Fluid & Heat, Heat Transfer & Phase Change, Microfluidics Version 4.2, Version 4.3a 3 Replies

Susie Sen
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I'm trying to find the temperature distribution in a microfluidic channel. The heat is generated by two electrode in a microfluidic channel. When I create the model without laminar flow everything looks fine. I can get the temperature increase in the channel by the joule heating.

However, as soon as I add laminar flow, all of the velocity profiles look fine, but there is no heat generated. I noticed the electrical field within the channel is no longer available (not applicable). Does this mean that I cannot combine laminar flow with joule heating for fluids? While using the laminar flow model I cannot have electrical current through any of my fluids? Is there anyone has idea to solve this problem?

Thanks.
3 Replies Last Post 21 févr. 2013, 02:58 UTC−5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 20 févr. 2013, 01:40 UTC−5
Hi

check the physics you are using and the dependent variables, you might have chosen complex physics such that you solve twice for the temperature T, T2 (or V, V2) and then you need to make them "equivalent" at the appropriate boundaries, or better select the physics such that you have each dependent variable only defined once

--
Good luck
Ivar
Hi check the physics you are using and the dependent variables, you might have chosen complex physics such that you solve twice for the temperature T, T2 (or V, V2) and then you need to make them "equivalent" at the appropriate boundaries, or better select the physics such that you have each dependent variable only defined once -- Good luck Ivar
Susie Sen
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Posted: 1 decade ago 20 févr. 2013, 18:03 UTC−5
Thanks for your reply. But I'm not quite understanding what you said. I'm using two physics: Joule Heating and Laminar Flow. I noticed when I add "heat transfer in fluid" under Joule Heating tab, I can not select the inlet surface or outlet surface of the fluid as "electric potential" or "ground" any longer (the fluid within the microfuidic channel is heated by two electrodes that are placed in the inlet or outlet).
Thanks.






Hi

check the physics you are using and the dependent variables, you might have chosen complex physics such that you solve twice for the temperature T, T2 (or V, V2) and then you need to make them "equivalent" at the appropriate boundaries, or better select the physics such that you have each dependent variable only defined once

--
Good luck
Ivar

Thanks for your reply. But I'm not quite understanding what you said. I'm using two physics: Joule Heating and Laminar Flow. I noticed when I add "heat transfer in fluid" under Joule Heating tab, I can not select the inlet surface or outlet surface of the fluid as "electric potential" or "ground" any longer (the fluid within the microfuidic channel is heated by two electrodes that are placed in the inlet or outlet). Thanks. [QUOTE] Hi check the physics you are using and the dependent variables, you might have chosen complex physics such that you solve twice for the temperature T, T2 (or V, V2) and then you need to make them "equivalent" at the appropriate boundaries, or better select the physics such that you have each dependent variable only defined once -- Good luck Ivar [/QUOTE]
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 21 févr. 2013, 02:58 UTC−5
Hi

you must ensure you turn the links on between EC and NITF once in EC for the temperature (Current conservation node), then you need to add a heat sorce in the NITF fluid domain linked to the EC Joule heat dissipation

I use NITF as this has solid, and fluid heat exchange included (Solid+HT+SPF combined physics)

I have added a v4.3a example model (I do not have any earlier versions running)

--
Good luck
Ivar
Hi you must ensure you turn the links on between EC and NITF once in EC for the temperature (Current conservation node), then you need to add a heat sorce in the NITF fluid domain linked to the EC Joule heat dissipation I use NITF as this has solid, and fluid heat exchange included (Solid+HT+SPF combined physics) I have added a v4.3a example model (I do not have any earlier versions running) -- Good luck Ivar

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