[Prandtl_2]

Hello!

I'm new in OpenFoam and use the interCondensatingEvaporatingFoam solver.
The tutorial condensatingVessel slightly confuses me. Of course the material values depend on the temperature. The vapour values are given for T=386, its the same like the initial value of the temperature, so that sounds logical. But I don't understand which temperature is assigned to the liquid phase (I think ca. 330K, because of the values from FC-72) and why?
An other question is which Prandtl Number I should use?
And the last question: The saturation temperature in the thermophysicalProperties is given to T=366 K. I checked this and found for FC-72 a T_Sat=330K. It is a mistake or is there a deeper meaning behind it?

I hope anybody can help me to understand this solver.

Regards

Robin

[floquation]

Originally Posted by Prandtl_2

Hello!

I'm new in OpenFoam and use the interCondensatingEvaporatingFoam solver.
The tutorial condensatingVessel slightly confuses me. Of course the material values depend on the temperature. The vapour values are given for T=386, its the same like the initial value of the temperature, so that sounds logical. But I don't understand which temperature is assigned to the liquid phase (I think ca. 330K, because of the values from FC-72) and why?

This solver is not part of my OF40 tree and you did not specify where you found it, hence all I'm going to do is give you a guess:
The "setFields" utility is probably called by that tutorial in "Allrun". There is an associated "./system/setFieldsDict" in which you can overwrite the initial condition for all fields with a different value in a specific region. That's also how they add a water column to the "damBreak" tutorial.

Originally Posted by Prandtl_2

An other question is which Prandtl Number I should use?

You'll have to look up the value of your fluid in literature. (You probably have to look some more - that link was found within one minute without really looking at it.) Be careful though, it is a temperature-dependent quantity.

Originally Posted by Prandtl_2

And the last question: The saturation temperature in the thermophysicalProperties is given to T=366 K. I checked this and found for FC-72 a T_Sat=330K. It is a mistake or is there a deeper meaning behind it?

The saturation temperature is a function of the environmental pressure. That is, a highly pressurized liquid requires a greater temperature to evaporate. In other words, the tutorial is probably concerned with a different pressure than the value that you found.

[Prandtl_2]

Thank you for your response, but I think I must specify my concern.

interCondensatingEvaporatingFoam is a relativ new solver from OpenFoam v1606+.
The tutorial is about a vessel which is filled with gas and then you have a negativ heat flow so that the temperature drops and the gas begins to condense.
The material values are for the gas phase as well as for the liquig phase from the transportPorperties.
But I don't understand why exactly these material values are used for the liquid phase.

The inital pressure is given to 1bar. Out of this value I have checked the saturation temperature and find the value T=330K...

Maybe I make a big mistake.

[floquation]

Originally Posted by Prandtl_2

The inital pressure is given to 1bar. Out of this value I have checked the saturation temperature and find the value T=330K...

Is it a closed bottle? If so, you'd expect the pressure to decrease as more gas is converted to liquid. Then, in principle, you should have a pressure-dependent saturation temperature. The tutorial is probably, however, a simple model, in which a "reasonable" constant saturation temperature is taken instead, just to obtain the qualitative behaviour. This saturation temperature should then be a decent average saturation temperature in the observed pressure range. Or, eventually a steady state is reached in which you will have some liquid and some gas inside the bottle, while the bottle is at a very low pressure. They could choose this "steady state" saturation temperature to get the correct final result.
However, if you start at 1atm and the pressure will only drop, then you'd expect , which is not the case in this tutorial (as they have chosen a too large saturation temperature according to your source). Therefore, it is probably not a closed bottle?

If the pressure remains constant, and you found a valid source that says at the given pressure, then there could be an incorrect value in the tutorial. But does it matter for you? It is just a tutorial - change the geometry / physical properties to whatever values you need for your problem.

[Prandtl_2]

The bottle is open at the top.
Of course you're right, I can change the saturation temperature. I found it just a little strange.

The issue that confuses me more is my first question: the liquid phase material values in the transportProperties. Do you have any ideas about this?

[floquation]

Originally Posted by Prandtl_2

The issue that confuses me more is my first question: the liquid phase material values in the transportProperties. Do you have any ideas about this?

In a phase change problem, it is typically a good approximation to assume one phase to be at the saturation temperature. (See e.g. the 1D Stefan problem.)
Since you have a problem with a cooling gas, the gas is at the varying temperature, and therefore the liquid may be assumed to be at the saturation temperature. Therefore, I reckon the liquid properties are taken at the saturation temperature. In your first post you estimated the temperature of the properties to be , and you found the saturation temperature to be equal to , hence this seems correct.
The saturation temperature was, however, set to a higher value, but as we had already concluded: that seems to be inconsistent/incorrect.

[Prandtl_2]

Ok, that sounds logical.
Thanks a lot for your help, that makes me a big step forward!