[MrAndersDk]

Hello

I'm new to OpenFOAM, or actually I'm looking into if I should learn OpenFOAM. So I have no experience with OpenFOAM, but I will take the time to learn if, it can solve the following problem.

I have a large pipe system with serveral heat exchangers placed at different places in the system. I'm currently not interested in the heat transfer in the system but only the flow in the pipes.

I know the Kv value for the heat exchangers (that is the pressure drop vs velocity). Is it possible to simulate this kind of problem. That is regular flow in the pipes, but when the flow reaches a heat exchanger it should use the known Kv value to calculate the pressure drop and flow through the region of the heat exchanger. I know it cannot tell me much about the flow inside the heat exchanger region, but that is ok, I need to know the flow in the pipe system.

I need this kind of setup to check how the flow is in our systems. As I'm not currently a user of OpenFOAM you donøt have to write a long explanation of how to do it, but if you can confirm such a thing is possible, or maybe show a link to an example where something similar is done it would be much appreciated.

[akidess]

Yes, this is possible, either with a porous region or a porousBafflePressure (jump condition).

[MrAndersDk]

Thanks. I had found something about the porous region and thought that might be the solution. However, I could not find out if it is possible to simply just give it at Kv value, or I had to do some hack to get it to do what I want.

Are there somewhere where I can find a good description of what porous region does?

[akidess]

It does not make sense to apply a Kv-Value to a region, because Kv is independent of size. You need to compute an equivalent porosity if you want to go this route. If all you care about is the jump, apply a jump condition.

[MrAndersDk]

I see. But can I make the jump condition depend on the velocity field, and can i make sure that the velocity field is the same on the other side of the jump region?

How would one go about calculating a equivalent porosity?

[akidess]

Originally Posted by MrAndersDk

I see. But can I make the jump condition depend on the velocity field, and can i make sure that the velocity field is the same on the other side of the jump region?

This is default behaviour. Go ahead and check out porousBafflePressure.

How would one go about calculating a equivalent porosity?

You should understand Darcy's law and it's implementation in OpenFOAM. With Darcy's law you get a pressure gradient, which you need to scale with the dimensions our your porous region to get a certain pressure drop. You can find a lot of documents on this online, but I'd recommend the jump condition.

[MrAndersDk]

Hello again. Thank you so much for your suggestions. I actually stumbled across the porousBafflePressure BC in my research after you led me in the right way.

Is it correct that the difference between porousBafflePressure and porous medium is that, with porousBafflePressure I will get an instantanous jump in pressure (which could be fine in my case), and with the porous medium I can have the pressure increase more gradually over a volume?

So I could use porousBafflePressure BC for thin heat exchangers, but for larger thicker heat exchangers I maybe should use porous medium.?


I'm currently going through Nagy youtube channel, as you have convinced me OpenFOAM can be used for my applications.

[akidess]

Originally Posted by MrAndersDk

Is it correct that the difference between porousBafflePressure and porous medium is that, with porousBafflePressure I will get an instantanous jump in pressure (which could be fine in my case), and with the porous medium I can have the pressure increase more gradually over a volume?

Yes, that's correct.

Originally Posted by MrAndersDk

So I could use porousBafflePressure BC for thin heat exchangers, but for larger thicker heat exchangers I maybe should use porous medium.?

Depends on what you want to know. If you don't care about the flow in or very close to the heat exchangers, you can always use the jump condition.

[MrAndersDk]

Thanks for the clarification