[6863523]

Hi, I am facing am interface setting problem in fluent.
I want to do the simulation of evaporation. There are two regions, one is water vapor, the other is wick saturated with liquid water. the evaporation is supposed to occur at the contact line between wick and vapor.
Need i specify the boundary type? Which kind? Interface? wall? porous-jump?
My email is 815719752@qq.com
Any suggestions would be appreciated. Thank you.
interface.png

[swiftaircraft]

If I understand your problem it has been set up 2 dimensionally. This will not provide any meaningful results. Correct me if I am wrong but you should have warm air flowing through the channel, say from bottom to top, and this channel is lined with the saturated wick. The warm air will then cause the evaporation. Is this correct? Are you trying to model another geometry?

[6863523]

Originally Posted by swiftaircraft

If I understand your problem it has been set up 2 dimensionally. This will not provide any meaningful results. Correct me if I am wrong but you should have warm air flowing through the channel, say from bottom to top, and this channel is lined with the saturated wick. The warm air will then cause the evaporation. Is this correct? Are you trying to model another geometry?

Hi David,
I have posted at http://www.cfd-online.com/Forums/blo...interface.html
I am sorry for the trouble.
Bill

[swiftaircraft]

When I click on the link you gave above nothing happens. Can you post as part of this thread?

[6863523]

Originally Posted by swiftaircraft

When I click on the link you gave above nothing happens. Can you post as part of this thread?

Hi David,
Thank you for your reply.
flow pattern.jpg
Please let me know if I have made the operation of my simulation model clear.
Best Regards,
Bill

[swiftaircraft]

I would not know how to model the wick in terms of it holding the water without it raining down from the upper surface. I expect that to overcome this you could turn off gravity since what you are trying to accomplish is the movement of the fluid due to the phase change. Ensure that when you define the water phase that you make the physical properties as a function of temperature. You will then also need to define a mass transfer function. I would say you need three phases. One is water, one is air and the other it water-vapour. Air and water-vapour to be defined as a species to ensure that they mix correctly. For a start I would define the wick area as a separate fluid zone so that you can force only water to be there. On the surface this looks a relatively simple problem but unless I am missing something it is going to be rather complex to set up.

[6863523]

Originally Posted by swiftaircraft

I would not know how to model the wick in terms of it holding the water without it raining down from the upper surface. I expect that to overcome this you could turn off gravity since what you are trying to accomplish is the movement of the fluid due to the phase change. Ensure that when you define the water phase that you make the physical properties as a function of temperature. You will then also need to define a mass transfer function. I would say you need three phases. One is water, one is air and the other it water-vapour. Air and water-vapour to be defined as a species to ensure that they mix correctly. For a start I would define the wick area as a separate fluid zone so that you can force only water to be there. On the surface this looks a relatively simple problem but unless I am missing something it is going to be rather complex to set up.

Hi David,
Thank you for your reply. I have got some confusions.
1. I did not turn on the gravity, the condensate at the outlet should flow back because of the capillary force supplied by the porous wick;
2.The flat heat pipe was vacuumized to remove air, because air will degrade the performance of the heat pipe. I wonder if the air is still need to add in the simulation.
3.The temperature difference of the whole model is only about 1K, I do not think the properties of water would change very much. What's your opinion?
4.By " define the wick area as a separate fluid zone", you mean I have to mesh the porous region alone. Well, actually, I have did the simulation only with porous wick region, velocity inlet/pressure outlet.But how to connect it with the vapor region. Have I mistook what you mean?
5.Yes. I am sure the evaporation interface is quite a complicated probelm. I have read some articles about it. They treated the wick-vapor interface mainly with three equations as below.
wick-vapor interface.png
But I have not got any clue how to do exactly.
I am really appreciated for your help.
Best Regards,
Bill

[arunraj]

Hi, Did you solve how to give velocity inlet at condenser interface and velcoity outlet at the evaporator interface. how can we provide velocity at the interface?