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Coaxial Borehole heat exchanger
Posted Dec 11, 2015, 5:52 a.m. EST Fluid & Heat, Heat Transfer & Phase Change, Porous Media Flow, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 5.2 3 Replies
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I work on geothermal heating systems using borehole heat exchanger (see file attached for general functioning of coaxial geothermal exchanger). To that purpose, I use non-isothermal pipe flow interface (calculates fluid exchanger temperature from reservoir temperature) coupled with Darcy's law and heat transfer in porous media interfaces (pressure and reservoir temperature).
So far I was able to model complex geometry of a single layered pipe loop. Now, I was wondering if there is a way to account for coaxial heat exchanger using the non-isothermal pipe flow interface (simplify 3D geometry of the pipe to 1D element). Due to the high extent of the numerical model, I cannot afford meshing the geothermal system explicitly in 3D. I know the solution exists in other numerical codes (such as FEFLOW) and I would like to reproduce using COMSOL.
Any suggestions would be highly appreciated!
Regards,
Morgan Le Lous
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Hello Morgan Le Lous
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I am working on a similiar problems and I am also interested in using the 1D pipe element to simplify 3D geometry of different types of ground heat exchangers, such as U-tube, double U-tube, coaxial, etc., to model the heat exchange betewen the fluid and the surrounding medium.
It would be great to know if anyone has used the Heat transfer in pipes physics interface to make an equivalent ground heat exchanger in 1D and could tell a bit more about their approach.
Best regards,
Mateusz
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I would advice you to have a look to this article. Authors developed a two-dimensional thermal resistance and capacity models for different types of BHE. The formulation is already available in FEFLOW code. Hope my contribution was helpful.
onlinelibrary.wiley.com/doi/10.1002/er.1689/pdf
Best regards.
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Yes, this can be done in COMSOL, see
www.comsol.com/blogs/modeling-geothermal-processes-comsol-software/
and the links therein.
Best,
Jeff