solidification process of phase change material through convective heat transfer and heat structure

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  • Last Post 03 March 2020
Rasyid03 posted this 26 February 2020

Hi,

I kind of new with ANSYS fluent and need some help. I'm trying to simulate solidification process of phase change material (pcm) with 2D model. the pcm fills the free space in the comb-liked heat transfer structures and at the top and bottom of the comb, there are heat transfer fluids that have temperature lower than the pcm. for the simulation I just draw a thin wall(blue) with thickness of 1,5 mm where at one side, the comb make contact with the wall and at the other side, heat transfer fluid.

after running the simulation for 4h, there is no temperature change to the heat structure. anyone knows why this happened?

 

regards,

rasyid

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abenhadj posted this 27 February 2020

So the blue lines are another fluid zone? Please more details about geometry boundary cond8...

Best regards, Amine

Rasyid03 posted this 27 February 2020

The blue line is the thin wall, which above/ under it flows heat transfer fluid with constant temperature of 285 dgrC. The walls have direct contact with the combs. I have defined wall BC on the fluid side with const temperature, since i only know the temperature as design requirement.. the pcm has melting temp of 306 dgrC and at the start of simulation, i set the pcm temperature as 326 dgrC

Rasyid03 posted this 27 February 2020

Above is my answer..feel free to ask me if you need more info..really glad if you can give me solution for it Thanks

abenhadj posted this 27 February 2020

I do see blue regions and cannot figure out where the blue line is: I am an old man can you please clarify where your boundary conditions are ? Under Report check if there is heat flux going across the walls in contact with the PCM domain.

Best regards, Amine

Rasyid03 posted this 28 February 2020

the BC is marked with red arrow and is named with wall_pp.unten

after checking, there is no heat flux across the walls

 

 

 

rwoolhou posted this 28 February 2020

I can't see any wall - wall:shadow pairs or interface zones so there's a good chance the two (or more) volumes aren't connected and therefore don't know to transfer heat. 

Rasyid03 posted this 28 February 2020

do you know how can I create the interface zones between two solid zones?

abenhadj posted this 28 February 2020

In the adjacency panel in Fluent look in the boundaries related to each cell zone. Aldo add good screenshots.

Best regards, Amine

Rasyid03 posted this 28 February 2020

 

abenhadj posted this 28 February 2020

You have definitely an issue with your mesh: why do have so many fluid zones?

Anyway now check here if you have a wall/wall-shadow connection connecting the kamm-solid to the other fluid zones. Do you see them? 

Best regards, Amine

Rasyid03 posted this 28 February 2020

in DM I make surface from 3D model of the pcm separately. and that's why i have many fluid zones

the are wall/wall-shadow connections between fluid zones pcm and the kamm-solid zones and the connections are coupled.

but there is no interfaces or coupled wall between kamm-solid and pp.unten-solid/pp.oben-solid

abenhadj posted this 28 February 2020

But you can create named selection for all fluids together and for solid..

Check now if under Flux/Report you have heat flux across the wall/wall shadow connections.

Best regards, Amine

Rasyid03 posted this 28 February 2020

there is no heat flux across it, even though the walls are coupled

abenhadj posted this 28 February 2020

What do you mean no heat flux? Add a screenshot?

 

I recommend

 

1/Better to go to pre-processing and create a single fluuid zone and the other solid zones

2/Recreate the case from scratch.

Best regards, Amine

Rasyid03 posted this 02 March 2020

I recreated the case from the beginning by removing the solid-pp.unten/.oben and using the shell conduction instead of separate parts in the simulation model. the simulation worked and heat were transfered through both wall.

am I doing this correctly (shell conduction)?

another thing is, when I simulated the solidification process for 10 hours, I got this liquid fraction (see below), which I think doesn't make any sense for sudden increase in liquid fraction. Am I correct?

liquid fraction for 10 h with time step of 30 min

 

and when I run it with 1 hour time step and for 5 hours, the pcm is fully melted after 4 hours which contradicts with the plot above. what did i do wrong here?

abenhadj posted this 02 March 2020

? Can you describe better after you changed almost everything? Just double check the time step size by running steady pseudo transient for two steps to get that time step as initial guess.

Best regards, Amine

Rasyid03 posted this 03 March 2020

I just remove the named components and modeled them as shell conduction. and I named all the pcm zone as one component with named selection. that's all

 

could you explain more to me regrading your second sentence?. I don't quite unterstand it.

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