Learning Forum

[Karthikkurinji]

Dear ANSYS Fluid Fraternity,

I have a steady-state heat transfer problem, where I cool a heat source (bottom) with flowing water(laminar) with the help of cylindrical fin arrays. I have an 8x8 array and an 8x1 array and I need to compare the local heat transfer coefficient so that I can validate using an 8x1 instead of an 8x8 to reduce the computational effort needed for my simulation. I need to calculate the local heat transfer coefficient (h) for the below-shown systems. All I can do in ANSYS Fluent now is to calculate the volume-averaged Surface heat transfer coefficient.

Consider, in these geometries, each cell is 5mm x 5mm. (with a cylindrical fin in the center of each cell as shown in the image below)

I would like to know how I can individually calculate the heat transfer coefficient for each cell (Fluid separately, Fin/Solid separately) so that I can compare both the geometries. Any leads are very much appreciated.

Thanks,

Karthik

[Karthik Remella]

Hello If I understand your CHT problem, you will need to estimate a surface average rather than a volume average heat transfer coefficient - since, convection heat transfer is a surface phenomenon.
You should be estimating this on the wall - wall-shadow surface between the fluid and solid (fin). If you have each wall - wall-shadow defined as a separate named selection, then you can simply pick them up when estimating your surface average.
Please make sure to use the same reference values when comparing.
Karthik

[Karthikkurinji]

Hello Kremella Thank you very much for your response.
You are right. Convection is indeed a surface phenomenon. However, there is both conduction and convection happening in this setup. There is conduction from the constant heat source at the bottom, to the fin as well as the fluid, and also convection between the source and the fluid and the fin and the fluid.
Hence, I am going for a volume-averaged heat transfer coefficient. I will be calculating h_fins and h_fluid and will take a ratio and would plot it cell-wise. Then I have to do the same for the 8x8 and compare these plots.
Because this h_solid/h_fluid ratio is important for me, is why I need to know how I can find it cell-wise. Please let me know if it is possible to do that.
Thank you very much for your time!
Karthik

[Rob]

HTC is a surface only value. If you have surfaces in the solid zone you can plot heat FLUX through that, and similarly from the fluid to the solid at the surface.

[Karthik Remella]

Hello You can create a separate named selection for the solid-fluid wall and another for the fin-fluid surface. This will allow you to extract the values you need. Don't use volume-averaged. This is incorrect.
Karthik

[Karthikkurinji]

Understood. Thanks for clarifying!