Learning Forum

[Benjamín]

Dear community, I am having problems applying the convective h equation in Ansys fluent results. I am performing a tubular simulation where I need to evaluate the convective heat transfer coefficient along the path. I have created planes but I cannot apply the equation as an expression in the planes of interest.

[Rob]

What are applying where? HTC is a fluid-wall effect, so you may need to rethink your approach. 

Moderator comment: posting multiple times is not recommended. 

[Benjamín]

I need to use the image expression in plans of interest created in cfd-post (results) because my objective is to know the convective coefficient of heat transfer of my transient simulation at specific times, y difficulty is how can I write the equation for the plan that I have created

[Rob]

On a plane it's meaningless. On a line maybe, but you then need to assign Tw and Tm (and q) in the maths. There's a reason we use reference values in the several functions in Fluent for HTC. 

[Benjamín]

I need the expression to be for a plane due to its irregularity, it is not an ideal circumference, so the plane would be more appropriate to cover the entire area, I share an image of my geometry. I know that it is possible to create an expression that is something like: Average(SurfaceHeatFlux/(Temperature-273.15 [K]),GetBoundary("@Heat Flow 1"),"Plane 1")

 

I appreciate any help you could give me to obtain the value of the convective heat transfer coefficient

[Rob]

Not really as there isn't a heat flux from that surface. Did you run the calculation in Fluent? 

[Benjamín]

That's right, the simulation is running and as I mentioned, the planes you see are planes created in cfd post to obtain values, the value of h is only one of the results I'm getting. I share with you another view of the geometry.

[Rob]

OK. In Fluent create the same surfaces using the isosurface tool and have the vessel wall selected when you apply the operation. That gives you a line on the surface. Create the same surface with the wall deselected. You can get the plane & wall surface temperatures at that position.  In the experiment I assume you use that data to then find the HTC? 

[Benjamín]

But is it not possible to simply create an expression like for example: Average(SurfaceHeatFlux/(Temperature-273.15 [K]),GetBoundary("@Heat Flow 1"),"Plane 1")
these expressions applied directly to the planes created in cfd.post? I say this because of the time and computational resources

[Rob]

There is no heat flux on a plane surface in a fluid zone. Heat flux is through something - you only have temperature data. This is why planning post processing before building a model is important. Adding bands or similar to the wall would make this trivial as we can report the flux directly in Fluent, along with various temperatures assuming the built in htc functions weren't suitable. 

CFD Post was recommened for Fluent for a few versions but Fluent's post processing is (for the most part) now much better: for numerical data I'd always use Fluent's output. 

[Benjamín]

The image is only a reference, the geometry is tubular, fluid circulates inside it, the planes were created to obtain the convective h value.