COMSOL Natural Convection Thermosyphon Convergence Problem

In summary: Thanks for trying to help!In summary, the model went haywire when the temperature difference exceeded 1degK.
  • #1
Conwedge
4
0
Hello,
I am having some problems with COMSOL multiphysics 3.5a. I am using 2D weakly compressible flow with general heat transfer and am trying to model a natural convection loop.

The Approach I have taken is to use properties of the material for a certain range of temperatures to model the variations in density with temperature which are responsible for the natural convection loop.

I have got the model working only for very small temperature difference (1degK) but above this temperature difference the model goes haywire. I was wondering if anyone has any insights into this problem.
 
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  • #2
Conwedge said:
Hello,
I am having some problems with COMSOL multiphysics http://www.3gcgroup.com/index.php/contact/careers" 3.5a. I am using 2D weakly compressible flow with general heat transfer and am trying to model a natural convection loop.

The Approach I have taken is to use properties of the material for a certain range of temperatures to model the variations in density with temperature which are responsible for the natural convection loop.

I have got the model working only for very small temperature difference (1degK) but above this temperature difference the http://www.3gcgroup.com/index.php/contact/careers" problem.

Are you sure you should be using 2D weakly compressible flow? I feel like you should be using something else. Did anyone figure this out!? THANKS
 
Last edited by a moderator:
  • #3
Hello,
Im having some problems with COMSOL multiphysics 3.5a. I am using 2D weakly compressible flow with general heat transfer and am trying to model a natural http://www.3gcgroup.com/index.php/contact/careers" loop.

The Approach I have taken is to use properties of the material for a certain range of http://www.3gcgroup.com/index.php/contact/careers" temperatures to model the variations in density with temperature which are responsible for the natural convection loop.

I have got the model working only for very small http://www.3gcgroup.com/index.php/contact/careers" problem.

Yeah i had the same problem/ I think the material temperature is off with the variations in density.
 
Last edited by a moderator:

1. What is a natural convection thermosyphon?

A natural convection thermosyphon is a heat transfer device that uses natural convection (the movement of fluid due to density differences) to circulate hot and cold fluids in a closed loop. It consists of a hot reservoir, a cold reservoir, and a connecting tube filled with a working fluid. As the fluid heats up and becomes less dense, it rises to the hot reservoir, where it releases heat and becomes denser, causing it to sink back down to the cold reservoir. This cycle continues, creating a natural convection loop.

2. What is a convergence problem in COMSOL?

A convergence problem in COMSOL occurs when the solution to a simulation does not converge or reach a stable solution. This can happen for various reasons, such as incorrect boundary conditions or mesh settings, or when the physics of the problem are too complex for the solver to handle. It is important to address convergence problems in order to obtain accurate and reliable results from simulations.

3. How does natural convection affect the convergence of a thermosyphon simulation?

Natural convection can greatly affect the convergence of a thermosyphon simulation because it introduces complex fluid dynamics and heat transfer phenomena. This can lead to difficulties in accurately modeling the behavior of the working fluid and the heat transfer between the hot and cold reservoirs. It is important to carefully consider the modeling parameters and boundary conditions when simulating a natural convection thermosyphon to ensure convergence.

4. What are some ways to improve the convergence of a COMSOL natural convection thermosyphon simulation?

There are several ways to improve the convergence of a COMSOL natural convection thermosyphon simulation. One way is to carefully select the mesh and element size, ensuring that it is fine enough to capture the complex fluid dynamics and heat transfer phenomena. Another way is to simplify the problem by adjusting boundary conditions or using simpler physics models. It may also be helpful to use a more advanced solver or adjust solver settings to improve convergence.

5. How can I validate the results of a COMSOL natural convection thermosyphon simulation?

To validate the results of a COMSOL natural convection thermosyphon simulation, it is important to compare them with experimental data or analytical solutions. This can help to ensure that the simulation accurately captures the behavior of the working fluid and the heat transfer processes. It may also be helpful to perform sensitivity analyses to assess the impact of different modeling parameters on the results. Additionally, it is important to carefully review and interpret the results to ensure they make physical sense.

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