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January 31, 2017, 00:51 |
Fluid-Fluid interface as thin material
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#1 |
Member
Adil Syyed
Join Date: May 2012
Posts: 49
Rep Power: 14 |
I am performing analysis on a double pipe heat exchanger with the hot fluid in the outer shell and cold fluid in the inner tube.
Now I can model a solid domain between the two fluid domains and specify the material, or I can simply define a fluid-fluid interface and specify the interface thickness along with material. My question is, if I specify a fluid-solid interface after modeling the metal tube, do I still need to give this interface the thickness and material? I already defined a solid domain of 1 mm thickness between the two fluid domains. |
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January 31, 2017, 04:08 |
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#2 |
Senior Member
urosgrivc
Join Date: Dec 2015
Location: Slovenija
Posts: 365
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You do not need to model the solid domain (tube).
1. First you create 2 domains (outer fluid, iner fluid) and under heat transfer you check either thermal or total energy. 2. create an Interface (pick the pairing surfaces) and under fluid models check no slip wall this means that no fluid can flow through the interface than Heat transfer options ocure and you can select conservative interface flux (this will be thermal energy) and under interface model you have an option to select thin material than select the material and its thicknes. that is it... You will not be able to see volume temperatures of the tube in cfx post, only on both sides (wals of the tube) and in the fluid domains ofcourse. ______________ The other option is to do a CHT simulation If you would do that you would need a third solid domain but why complicate if it is not nesecary And the ansver for the last question is, no, if you model the solid tube domain than you dont have any additional interface material, unles the tubes have let say a lot of lime stone on them that could be the interface material , but you do hawe two (fluid solid) interfaces, |
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February 1, 2017, 01:11 |
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#3 | |
Member
Adil Syyed
Join Date: May 2012
Posts: 49
Rep Power: 14 |
Quote:
PS: I may use solid domain IF the geometry i.e diameter of the outer fluid shell effects other parts of the geometry. Then to preserve the geometry this approach might be used. |
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February 1, 2017, 01:14 |
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#4 |
Member
Adil Syyed
Join Date: May 2012
Posts: 49
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The two fluids does not mix, only heat transfer across the interface occurs.
What if I use water as first fluid and steam as second. There is no physical interaction, no mass transfer occurs. But still it becomes a two phase flow and requires two phase flow modeling. How can one get around that problem. PS: I asked a similar question in another thread, hope that's not a problem. |
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February 1, 2017, 01:38 |
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#5 | |
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Adil Syyed
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Quote:
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February 9, 2019, 22:16 |
Mass Transfer across Fluid-Fluid Interface
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#6 |
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Soumitra Vadnerkar
Join Date: Aug 2018
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What if I want both Mass and Heat Transfer to occur between two domains?
What should I select? Can you please elaborate what does Conservative Interface Flux mean? |
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February 10, 2019, 06:46 |
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#7 |
Super Moderator
Glenn Horrocks
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Location: Sydney, Australia
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Conservative interface flux means exactly what it says - the flux of the variable over the interface is conserved. This might sound obvious but a simple interpolation at an interface is not always conservative - meaning material is created or destroyed by the numerical approach of the interface.
By mass transfer do you mean your flow passes through it, or do you mean a mass fraction passes through it, such as water diffusing into a solid?
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February 10, 2019, 12:47 |
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#8 |
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Soumitra Vadnerkar
Join Date: Aug 2018
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Thanks.
And by mass transfer I mean fluid flow passing through the interface without any loss. In my case, I have two exactly same fluid domains but with different geometries and with common cross section at the interface. I want to simply connect the two domains and allow fluid flow (carrying mass and heat) in-between the two domains as if there is no interface boundary; which option should I use? |
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February 10, 2019, 17:57 |
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#9 |
Super Moderator
Glenn Horrocks
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If you set up a interface between two fluid domains the default condition is that it allows fluid flow and all scalar variables with it (heat, volume/mass fraction, other scalars) to pass through the interface. No special handling is required.
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February 27, 2019, 12:14 |
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#10 | |
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