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surface tension and capillarity

152 Views, 13 Replies
12/24/2017 8:37 AM

is CFD able to consider the surface tension and the capillarity pressure in tight channel flow?

can phase change be analyzed?


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Message 1 of 13 ( Views: 152 )

Re: surface tension and capillarity

12/27/2017 5:34 PM
I would say no, we definitely cannot capture surface tension and I do not think we can capture capillary pressure either...
How is the flow driven?

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Message 2 of 13 ( Views: 129 )

Re: surface tension and capillarity

12/28/2017 7:59 AM

i hope coming version can capture the surface tension ...  

really don't like ansys interface :{

 

flow happens inside the flat plate or the vapor chamber...

working fluid evaporates because of heat which dissipates from a heat source

to the evaporator in the chamber, the fluid then flows toward the condenser.

after it condenses, the capillarity of the wick pump it back to the evaporator.


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Message 3 of 13 ( Views: 123 )

Re: surface tension and capillarity

12/28/2017 8:56 AM

OK, we definitely can't do that :D

 

Honestly I am not sure if it something that is coming or not, did you log it on the Idea Station?

It's quite a specific need I think, worth asking though!

 

Thanks,

Jon


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Message 4 of 13 ( Views: 117 )

Re: surface tension and capillarity

12/28/2017 10:58 AM

sue, i will post in idea station.. a large percentage of electronics cooling application

depends on phase change, where the capillarity is a vital factor.

 

what about phase change in cfd ?

is it possible to consider and see the phase change 

 for example, if we have flow inside a heated pipe 

and evaporation or condensation should happen,

can this be captured?

 


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Message 5 of 13 ( Views: 115 )

Re: surface tension and capillarity

12/28/2017 11:18 AM

We can capture phase change but I would say it depends what you are modelling.

For example, if you want to capture phase change in a pipe network for a refrigeration system, that is where we can work well.

 

If you are looking at something like a heat pipe, that is where you might as well just use a highly conductive material instead as we cannot really model this sort of change and it is not really worth the effort when you can just use a nice simple material :)

 

What sort of phase change are you modelling here exactly?

 

Thanks,

Jon


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Message 6 of 13 ( Views: 113 )

Re: surface tension and capillarity

12/28/2017 11:46 AM

if i have a water or refrigerant flow in a pipe ( with a reasonable diameter where we can neglect the surface tension)

suppose i heat the fluid in the bottom side of the pipe to evaporate it and make it flow up then cool it in the top side 

to condense it and make it flow down (because of the effect of gravity)  and complete the cycle. 

is it possible to capture things in this case?


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Message 7 of 13 ( Views: 111 )

Re: surface tension and capillarity

12/28/2017 11:54 AM

I would say not, no. Ours works more for a change in flow in a single direction.

Not for what is more like surface evaporation.

 

Is it just a heat pipe?


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Message 8 of 13 ( Views: 109 )

Re: surface tension and capillarity

12/28/2017 11:58 AM

yes, heat pipe or thermosyphon

 


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Message 9 of 13 ( Views: 107 )

Re: surface tension and capillarity

12/28/2017 12:26 PM

OK then there is usually a far simpler way to model it :)

 

Check the manufacturers datasheet but we tend to assign them something like this (much simpler a usually really similar to the real thing!).

You can also change the conductivity so that it is just copper in the normal directions but really high in the axial direction so the heat can transfer along it's length like a real heat pipe.

 

I hope that helps!

Jon


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Message 10 of 13 ( Views: 104 )

Re: surface tension and capillarity

12/29/2017 8:26 AM

thank you Jon, 

can you reshare the last link again, i can't have an access to the page.  


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Message 11 of 13 ( Views: 97 )

Re: surface tension and capillarity

12/31/2017 9:16 AM

please notice the paper in the attachments

it will be very nice if anyone can compute the evaporation, condensation, permeability  around the pillar with CFD 

not FLUENT any one 

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Message 12 of 13 ( Views: 86 )

Re: surface tension and capillarity

01/02/2018 7:01 AM

OK, try it again :)

 

It is also OK just to follow my description, it probably contains more than the article.


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Message 13 of 13 ( Views: 76 )