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How to fix the temperature of a domain to a constant value ?

Posted 26.02.2020, 01:45 GMT-5 Electromagnetic Heating, Heat Transfer & Phase Change Version 5.4 2 Replies

Ayush Kumar
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I am using comsol 5.4 2-D axis-symmetric geometry. I have to fix the temperature at 300K throughout the model in all domains. How do I do this?

2 Replies Last Post 20.05.2020, 19:38 GMT-4
Magnus Ringh COMSOL Employee

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Posted: 5 years ago 27.02.2020, 10:05 GMT-5

Hi Ayush,

It's hard to say why you want a model with a fixed temperature everywhere. That said, I think it can be achieved in some different ways:

  • A heat transfer model with constant and consistent temperature boundary conditions and initial conditions and with no dynamics would keep that fixed temperature throughout the simulation.
  • If you have other physics in your COMSOL Multiphysics model, you can choose to not solve for the temperature and let it be represented, under Values of variables not solved for in the Settings window for the study, by its (fixed and constant) initial expression, defined in the Initial Values node.
  • A third possibility is to force the temperature in the domain using a Pointwise Constraint node to set the temperature to a fixed value using a Constraint expression such as 293[K]-T (to access that functionality, you need to first enable Equation-Based Contributions in the Show More Options dialog box).

Best regards,

Magnus Ringh, COMSOL

Hi Ayush, It's hard to say why you want a model with a fixed temperature everywhere. That said, I think it can be achieved in some different ways: * A heat transfer model with constant and consistent temperature boundary conditions and initial conditions and with no dynamics would keep that fixed temperature throughout the simulation. * If you have other physics in your COMSOL Multiphysics model, you can choose to not solve for the temperature and let it be represented, under **Values of variables not solved for** in the **Settings** window for the study, by its (fixed and constant) initial expression, defined in the **Initial Values** node. * A third possibility is to force the temperature in the domain using a **Pointwise Constraint** node to set the temperature to a fixed value using a **Constraint expression** such as `293[K]-T` (to access that functionality, you need to first enable **Equation-Based Contributions** in the **Show More Options** dialog box). Best regards, Magnus Ringh, COMSOL
Ignacio Giménez de Córdoba
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Posted: 5 years ago 20.05.2020, 19:38 GMT-4

Hi Magnus,

I am trying to simulate a heated flow (always at 37ºC) through a structure at ambient temperature (20ºC). To make calculations easier for comsol to avoid long calculation times, I am definig it as a liquid without movement (so I eliminate laminar flow, I leave heat transfer in solids and fluids only). The problem comes when I try to keep this temperature always at 37ºC, because I am defining an initial value of 37ºC but when time passes, the heat "flows" to the structure so the fluid ends up being at 34ºC. How can I fix the temperature of the fluid at 37ºC. I am trying to add a constraint but I don't know how.

Thanks!

Hi Magnus, I am trying to simulate a heated flow (always at 37ºC) through a structure at ambient temperature (20ºC). To make calculations easier for comsol to avoid long calculation times, I am definig it as a liquid without movement (so I eliminate laminar flow, I leave heat transfer in solids and fluids only). The problem comes when I try to keep this temperature always at 37ºC, because I am defining an initial value of 37ºC but when time passes, the heat "flows" to the structure so the fluid ends up being at 34ºC. How can I fix the temperature of the fluid at 37ºC. I am trying to add a constraint but I don't know how. Thanks!

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