Learning Forum

[Gordon Howat]

Hello,

In CHT analysis (Fluent), is it possible to specify the flux through an interface, thus forcing a heat flow rate other than that calculated by the solver?

This interface is one of several which are in parallel in the model, but has particularly complex geometry.

I know the flux through the complex geometry from a much smaller partial model. I would now like to build a model of the full system using a simplified representation of the complex geometry to keep mesh size tractable and force the correct, pre-calculated heat flux, by applying it on the interface (if this is possible).   

Thank you in anticipation!

[Rob]

You may be able to force the flux by decoupling a wall wall:shadow pair but there's not anything on an interface to attach the flux to. 

[Gordon Howat]

Thank you for your reply Rob.

Does how the interface is set up change this? It's currently a multibody part ( Inventor .ipt) which I take into Spaceclaim  for clean up. I delete duplicate faces in Spaceclaim so the interfaces becomes single surfaces which Fluent then creates shadow walls for (I think, bit unclear about how this works). If I dont delete those duplicate faces would there be two walls for each interface in Fluent so I can attach +ve flux on the fluid side and -ve flux on the solid side?

[Rob]

So not an interface, it's a wall & shadow pair. If you decouple (slit) the pair using a TUI command both become external to the domain. However, I'd then question why you want to model both parts in the same simulation. 

[Gordon Howat]

Hello Rob, 

Thanks again. The interface is one of several which are in parallel in the model, but has particularly complex geometry. I extracted a flux through the complex geometry from a much smaller partial model which captured the full complexity (so is hopefully accurate). I would now like to build a model of the full system using a simplified representation of that complex geometry to keep mesh size tractable, and force the correct, pre-calculated heat flux according to the new surface area, by forcing that flux on the interface. 

I have decoupled the wall and shadow pair via the GUI and tested it by applying an extreme flux and plotting temperature contours. This appeared to be sending heat in the right direction (and also allowed me to identify which wall/shadow pair to use as I dont see any other way of identifying them). I am now running a partial, simplified model with the required heat flux applied, to compare that with the complex partial model. If I can get a correlation between the solid temperatures there, I think I can proceed to model the full, simplified domain. 

I have little experience here so please advise if there is a better way of doing this.

Kind regards,

Gordon.

[Gordon Howat]

Hello Rob, 

Thanks again. The interface is one of several which are in parallel in the model, but has particularly complex geometry. I extracted a flux through the complex geometry from a much smaller partial model which captured the full complexity (so is hopefully accurate). I would now like to build a model of the full system using a simplified representation of that complex geometry to keep mesh size tractable, and force the correct, pre-calculated heat flux according to the new surface area, by forcing that flux on the interface. 

I have decoupled the wall and shadow pair via the GUI and tested it by applying an extreme flux and plotting temperature contours. This appeared to be sending heat in the right direction (and also allowed me to identify which wall/shadow pair to use as I dont see any other way of identifying them). I am now running a partial, simplified model with the required heat flux applied, to compare that with the complex partial model. If I can get a correlation between the solid temperatures there, I think I can proceed to model the full, simplified domain. 

I have little experience here so please advise if there is a better way of doing this.

Kind regards,

Gordon.

[Rob]

We're very limited on what we can cover on here as the Forum is public and must comply with Export Law. 

With what you propose I'd be VERY careful to ensure I knew where what heat was going and that both the fluxes & temperatures made sense. I'd also continue to question why you're modelling both parts in one simulation if they're decoupled in this way. 

[Gordon Howat]

I understand re. export law. I'm UK based and can contact EDR Medeso for support but hoped this may be faster, I haven't used the forum before. 

Perhaps I'm misinterpreting the terminology. I'm decoupling the wall/shadow pair as it seems to be the only way to force a specific value of heat flux from the solid into the liquid, no other reason.

Changing the wall/shadow from "Coupled" to "Heat Flux" in the GUI enables a flux to be specified.

If there's any other way, I'm happy to do it differently. My objective is to artificially force a pre-calculated heat flux between the solid/fluid, I dont mind how I get there, if in fact it is possible! 

Thanks again.

[Rob]

I was wondering if it was you! :)  

Talk to EDR - they'll want pictures and can go into details. What you're doing could work but I'd exercise caution based on what I can see in your posts. 

[Gordon Howat]

OK, great, shall do. Thanks again Rob!