[bensonnggl]

Hihi! Im new to Ansys and to this forum. Hope to get advise on my Final year project for my degree on this topic.

I am suppose to analyse the effectiveness of a heat pipe in transfering heat from point A to B. This is probably a thermal and fluid analysis which has to be solve simultaneously where the working fluid act as the medium in transferring heat via phase change. This working fluid is embedded in a pipe consisting of the outer wall and an inner porous wick structure (which transports the fluid from the condenser side back to the evaporator side via capillary action) which contains the fluid.

http://en.wikipedia.org/wiki/Heat_pipe

Various questions I like to clarify:
1) Can this analysis be solve simultaneously since there are two differnet physics involve: fluid and solid hence the probable use of flotran elements and solid elements
2) Is it possible to restrict and control the velocity in the fluid as well the fluids that is in the wick structure?

I'm totally new to Ansys hence have been having a hard time learning the software. Hope to be enlightened! Thanks in advance people!

[ghorrocks]

This can be solved entirely within CFX, CFX can do heat transfer in solids.

You will probably want to model the wick as a porous region. You can define different resistances in different directions to account for anisotropy.

The heat transfer in fluid and solid should be OK, likewise the porous body. The tricky bit will be doing something sensible with the phase change heat transfer. This will be tricky as modelling phase change is always tricky.

[Miky1020]

Hi, bensonnggl

A time ago I have simulated a micro heat pipe whose operation is the same as you have described except for capillarity effect is due the variation for interphase radii of curvature instead due the porous wick. Phase change was very tricky as ghorrocks says, especially because you have to modelling condensation and vaporization at the same time in a box closed domain, and this can cause mass imbalance problems, but for me the really big problem was the surface tension model, because interphase is too blurry for a suitable radii of curvature definition.

[bensonnggl]

Hi ghorrocks and Milky1020, thanks for the advice for the post. I am now modeling the heat pipe via CFX which makes the problem much easier! However, I am still facing some issues that I cant solve.

1) How can I model the wick so that the fluid in it flows opposite in direction to the working fluid? I tried setting one end of the working fluid as the inlet for the fluid domain and the other end of the wick as the inlet for the porous domain but this causes both side of the fluid to flow towards the center of the pipe. Is there a way to physically separate the two domains so that there is no interference in the fluid flow in the individual domains yet forming a loop for the fluid to be recycled?

2) Also, can CFX take care of the phase change automatically since the water should vaporise when the temperature soar above 100 degree celsius?

Thanks in advance!

[michael_owen]

Miky,

You will probably want to use a momentum source to model the capillary driven flow in the porous wick. I may have to build such a model for a consulting client in a few weeks, so I might be able to provide some guidance when I get around it it.

Secondly, you will have trouble if heat transfer between the porous wick and the fluid is important, and conjugate heat transfer between the fluid and porous solid in a porous domain is not an out-of-the-box feature in CFX R12. It will be supported in beta when R13 comes out next month. However, I made a recent post where I provided a model for CHT in porous domains in R12 using supported features. Search for the thread on modeling a corn silo.

[DanielLai]

Hi everyone, i am currently doing my undergrad and i get this topic (heat pipe) for my final year project...... Just wanna ask whether cfx or fluent is easier to use to model the boiling part of the working fluid in it. Any suggestion??

for the heating part, do i need to draw a heating medium to contact to the pipe?? or juz put the boundary condition of the heat pipe wall as heat flux in to serve as a heating source??

type of working fluid: water
type of HP material: copper
and there is very thin porous domain in the heat pipe to simplify things....

i'm running out of time, hope anyone in this forum can give some suggestion and guidance.... thanks in advance...

[Heat Pipe]

DanielLai

I posted more than 6 threads no body has any background or experience
be in touch with me to solve it ,, I'm working on same geometry
many people suggested me use Fluent better


cu

[DanielLai]

hi omeradnan,

Thanks for replying me ! YA,sure.. is my pleasure to work together. Just want to ask, do you have the boiling tutorial of FLUENT? can u email to danieleylai@hotmail.com if you have it.... Really appreciate it coz i really running out of time.... thanks alot man!

[Lalit]

Hi Micheal,

Can you explain on how you modeled the wicking by adding source terms.

Thanks
Lalit

[Mahboobe365]

Dear all,

Do you remember your simulations on heat pipe? I am working on the similar problem and I have some question

[mecman]

Hi all
i want simulate Heat pipe in fluent too,any body solve this problem?i want use Vof model for simulate this,But i dont Know how simulate boiling with VOF model in fluent...
plz help..
regard

[ghorrocks]

Try the fluent forum.

[es99]

Hi my dear friends;
I have one question about boundary condition consider in gambit software.
what boundary condition should be consider for heat pipe simulation in fleuent?
for example velocity inlet for heat pipe center or wall for heat pipe wick?
please help me

[ghorrocks]

Again - this is the CFX forum. For Fluent questions try the fluent forum.

[es99]

Excuse me my freind

[shahid nadeem]

Did anyone got the results for it?

[shahriari]

how to model The radial blowing and suction velocities at liquid-vapour
interface in fluent. i want to Numerically Simulate two different regions which contains vapor and wick simultaneously in The Heat Pipe??????

[ghorrocks]

Third time... This is the CFX forum. Try the Fluent forum.