[arianam]

I tried to model boiling with reactingEulerFoam and it worked as the first step.
more details:
The geometry is a simple closed block full of liquid water near saturation temperature. The block temperture on bottom surface is higher than Tsat.
The phase type is ThermalPhaseChangePhaseSystem for water in two phases of liquid and gas.

As the second step, I devided the block to half liquid and half gas by setfields. The species is still water.
By applying the same BCs, the solution does not converge. The temperature and pressures diverges very quickly to small values.
I looked more carefully in the code and I understood this might be due to Tf and interfacial mass transfer or phase change calculation.

So basically, I am trapped between using one of these two: InterfaceCompositionPhaseChangePhaseSystem that is for interfacial phase change and ThermalPhaseChangePhaseSystem that I need it for wall boiling phase change.

I know that this code is a new code, and few people have gone through it, but any help is appreciated!

[S.Colucci]

Originally Posted by arianam

I tried to model boiling with reactingEulerFoam and it worked as the first step.
more details:
The geometry is a simple closed block full of liquid water near saturation temperature. The block temperture on bottom surface is higher than Tsat.
The phase type is ThermalPhaseChangePhaseSystem for water in two phases of liquid and gas.

As the second step, I devided the block to half liquid and half gas by setfields. The species is still water.
By applying the same BCs, the solution does not converge. The temperature and pressures diverges very quickly to small values.
I looked more carefully in the code and I understood this might be due to Tf and interfacial mass transfer or phase change calculation.

So basically, I am trapped between using one of these two: InterfaceCompositionPhaseChangePhaseSystem that is for interfacial phase change and ThermalPhaseChangePhaseSystem that I need it for wall boiling phase change.

I know that this code is a new code, and few people have gone through it, but any help is appreciated!

Hi,
I did the same successfully! When you have this kind of problem I think it depends on the phase change rate that is too high because the water at initial conditions is too much oversaturated. If you need, I can send you the input file of my simulation.

Best Regards

Simone

[arianam]

Originally Posted by S.Colucci

Hi,
I did the same successfully! When you have this kind of problem I think it depends on the phase change rate that is too high because the water at initial conditions is too much oversaturated. If you need, I can send you the input file of my simulation.

Best Regards

Simone

Thanks for your response Simone!
Actually, I pushed forward the problem. I do still think that convergence is a big issue for this case and solver. However, I could control it.
Now, The problem that I face is the diffusion of liquid and gas at the interface. So the interface fades with time which is not physical.
The pipe is closed with half liquid and half gas.The cylindrical patch is divided into two(in longitudinal direction) so that two different temperature is applied to these half cylinders.
Do you have any idea where the problem is?

[erlend_grotle]

Hi,

Im searching for tutorial cases in which the problems you mention are relevant. I think InterfacialCompositionPhaseChange is the one I need, to solve direct-contact phase change in separated flow.

Which tutorial should I go to? Or even better- can you hand over the case you show with the tank?


BR
Erlend

[arianam]

Hi Erlend,
I think the best tutorial for you would be :
tutorials/multiphase/reactingTwoPhaseEulerFoam/RAS/wallBoiling
It is a good starting point for your case that is not very far from what you try to model by OpenFOAM. it is based in ThermalPhaseChangeModel.
For wall phase change, you can use the wall functions implemented in most recent vesions of OpenFOAM.(alphatPhaseChange family wall functions).
Best,
Mohsen

Originally Posted by erlend_grotle

Hi,

Im searching for tutorial cases in which the problems you mention are relevant. I think InterfacialCompositionPhaseChange is the one I need, to solve direct-contact phase change in separated flow.

Which tutorial should I go to? Or even better- can you hand over the case you show with the tank?


BR
Erlend

[erlend_grotle]

Hi arianam,
Thanks for your reply. I want to have interfacial phase change between liquid and gas, direct-contact. Do you think the model are relevant for this as well?
I will investigate and do the tutorial.

BR
Erlend

[arianam]

Yes. AFAK, this phase system model (ThermalPhaseChangePhaseSystem) takes in to account the two phase change mechanisms(volume and wall). idmdt field corresponds to interfacial phase change that is the same as volumic phase change. wdmdt is the wall phase change term obtained by wall function phase change term. The total phase change is the sum of two. However, you should know that the model doest not seem capable of modelling interfacial phase change in form of evaporation(diffusion of liquid phase in gas phase). For that, you need to change to InterfaceCompositionPhaseChangePhaseSystem.
Best,
Mohsen

Originally Posted by erlend_grotle

Hi arianam,
Thanks for your reply. I want to have interfacial phase change between liquid and gas, direct-contact. Do you think the model are relevant for this as well?
I will investigate and do the tutorial.

BR
Erlend

[erlend_grotle]

Thank you arianam for this information.

BR
Erlend

[erlend_grotle]

Dear Mohsen,

I have tried to change the tutorial "wallboiling" to a closed system with only walls. Then I use setFields to create a stratified initial case. I am excluding heat supply and try with slight temperature difference between liquid and gas. The results are strange.

I have not changed the Properties in any way. Is this related to unphysical starting conditions, or do I have to change the model properties? Im not sure if the stratified case can run with the existing model set-up.
Sorry for the lack of information, but if I understood you correctly you had looked into almost similar case.

Thanks,
Erlend

[arianam]

Hi,
How do you apply the difference between liq and gas temperatures? If you apply it by setFields, it is OK.
Surely, you will have the problem of convergence in stratified case, and need to work on that.
Did you cancel the boiling conditions or you want to keep them?
If it is possible, upload your case, so I might be able to help you in a more efficient way.
Best,
Mohsen

Originally Posted by erlend_grotle

Dear Mohsen,

I have tried to change the tutorial "wallboiling" to a closed system with only walls. Then I use setFields to create a stratified initial case. I am excluding heat supply and try with slight temperature difference between liquid and gas. The results are strange.

I have not changed the Properties in any way. Is this related to unphysical starting conditions, or do I have to change the model properties? Im not sure if the stratified case can run with the existing model set-up.
Sorry for the lack of information, but if I understood you correctly you had looked into almost similar case.

Thanks,
Erlend

[erlend_grotle]

Thanks for you help.
It is stable now. I added a heated wall in the bottom and slight temperature difference between liquid and gas. Only walls now, no empty patch.

Please find the attach case files, and any comment will be very much appreciated.

BR
Erlend

[erlend_grotle]

But there is nothing happening, so I guess there is something wrong with the set-up

BR
Erlend

[arianam]

There is not a fast magic way for using OpenFOAM. It need one to be consistent. I looked at your case, it is important to know that when you modify part of your case it need to consistent to the other parts. For example:
by checkingMesh:
Overall domain bounding box (0 0 0) (0.05 2 0.1)
But how come for settingField you use this?!:
regions
(
boxToCell
{
box (-100 -100 -100) (100 1 100);
fieldValues
(
volScalarFieldValue alpha.liquid 1
);
}

boxToCell
{
box (-100 1 -100) (100 100 100);
fieldValues
(
volScalarFieldValue alpha.gas 1

);
}

The other example, if you compare alpha.* files with k.* files in 0 folder after setting field, you will see that the size of internalFields are not the same. You might have changed the meshing, so you need to change other boundary conditions since this case initial condition for both internalFields and patchfields are not uniform. There is a matrix and array of numbers given for internal field and boundary field that is probably obtained from running the case with a simpler code without activating all of its features to find a stable initial condition.
So, what I suggest is that you go through all initial conditions, and set them uniformly since we do not have any idea which initial condition guess is better for you case.
Alway before running your case, check it out with paraFoam for t=0. As you can see, it gives you the error of the size of k field(it is the first field read) since it is not compatible to your mesh.
checkMesh gives you hint on the size of your matrixes.
Work on your case step by step. If there is nothing in that to change mesh, put it aside for the moment, and just concentrate on initial conditions.

I hope that you'll find this helpful.

Originally Posted by erlend_grotle

But there is nothing happening, so I guess there is something wrong with the set-up

BR
Erlend

[erlend_grotle]

Thanks for your reply. I turned on to laminar for the moment, and that's why the k-files are not consistent with the rest.

BR
Erlend

[Prandtl_2]

Originally Posted by arianam

Thanks for your response Simone!
Actually, I pushed forward the problem. I do still think that convergence is a big issue for this case and solver. However, I could control it.
Now, The problem that I face is the diffusion of liquid and gas at the interface. So the interface fades with time which is not physical.
The pipe is closed with half liquid and half gas.The cylindrical patch is divided into two(in longitudinal direction) so that two different temperature is applied to these half cylinders.
Do you have any idea where the problem is?

Dear Mohsen,

I use the interCondensatingEvaporatingFoam solver from OpenFoam v1606+ and have a similar problem with the convergence at the interface between the liquid and gas phase.
Could you please describe how you controll it and how you solve your other problems? I hope I can transfer it to my case.

Best regards
Robin

[Prandtl_2]

Hello,

Meanwhile I also use reactingEulerFoam.

My aim is to simulate the evaporation of water into air and I would follow the mass fraction of water vapour in air.

For my case I devided my domain into a liquid phase (water) at the bottom and gas phase (0.5 air/ 0.5 water vapour) on the top by setfields.
I used the interfaceCompositionModel "saturated" with the saturation model ArdenBuck.
But at the moment my simulation break up very fast and I have no increasing of the vapour mass fraction in the gas phase.

Could anyone please help me?

Best regards

Robin

[BlnPhoenix]

Originally Posted by Prandtl_2

Hello,

Meanwhile I also use reactingEulerFoam.

My aim is to simulate the evaporation of water into air and I would follow the mass fraction of water vapour in air.

For my case I devided my domain into a liquid phase (water) at the bottom and gas phase (0.5 air/ 0.5 water vapour) on the top by setfields.
I used the interfaceCompositionModel "saturated" with the saturation model ArdenBuck.
But at the moment my simulation break up very fast and I have no increasing of the vapour mass fraction in the gas phase.

Could anyone please help me?

Best regards

Robin

Hi Robin,

have you managed to converge your case? I'm trying reactingTwoPhaseEulerFoam right now and tried to get it stable by increasing Pimple Iterations and lower convergence parameters.

[linhz0hz]

Hello,
I am also hitting similar problems.
I tried to modify the bubbleColumnEvaporating example for reactingTwoPhaseEulerFoam and I want to model boiling of water. I changed the bottom to be a wall, and then increased the temperature close to saturation. I changed to Antoine saturation model because I eventually need to model some other liquid, but ArdenBuck is only for water (as I understand).
I kept the 350 degree temperature, but still I am finding that the solver will diverge and get non-physical temperatures (negatives or over 1000K). I tried to get finner mesh and smaller time-step which mediated this problem, and the solver can run fine with 350deg initial temperature. But when I increase the temperature a bit that issue hits me again. I am not sure if I should just increase mesh size or there is something fundamentally wrong with my setting / BC.

I am an undergrad student just stated to learn CFD and OpenFOAM on my own, any help greatly appreciated.

[sjohn2]

Does anyone have the theory behind the
thermalPhaseChangeTwoPhaseSystem ?

How does OpenFoam compute the mass trasnfer terms based on interpolation from the saturation values provided in .csv files?

[Sk Hossen Ali]

Dear Mohsen and others,

I am also trying to simulate evaporation of water in reactingTwoPhaseEulerFoam, using thermalPhaseChangeTwoPhaseSystem for mass and heat transfer between water(liquid in lower half of the domain) and air-water(gas in the upper half of the domain) mixture.

In my case I assume the liquid initially to be at saturation condition and heat flux is coming from the gas (higher temperature) side. I am also proving heat flux boundary condition from the outlet(upper side) to make the evaporation process speedy.

I expect evaporation to happen due to heat transfer from the hotter gas and constant heat flux from outside, but no matter what always the temperature of gas near the interface drops beyond the saturation temperature of liquid and condensation starts at the interface.

I am attaching my case file please please have a look at it , and suggestion and help would be highly appreciated.

https://drive.google.com/file/d/1DhB...ew?usp=sharing

Thanks in advance.