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-   -   convective heat transfer, how? (http://www.cfd-online.com/Forums/ansys/79151-convective-heat-transfer-how.html)

Steffen August 14, 2010 08:19

convective heat transfer, how?
 
Hi,

what I am trying to do is model heat transfer in air gaps. Example a double glazed window, different temperatures both sides. What can Ansys do, and how? Tried CFX, but could not work out how to assign the temperatures to the boundary surfaces.

Cheers,

Steffen

neilduffy1024 August 16, 2010 12:57

Hi Steffen,

I assume you are talking about Fluent as both CFX and Fluent are now part of ANSYS. In CFX, to set a temperature to a boundary condition (BC) go to insert-boundary (It will also appear on the toolbar as a box with 2 arrows). You'll need to set your BC to a "wall". you should then be able to specify temperatures, emmisivities etc.

Regards,

Neil

Steffen August 17, 2010 06:04

seems its just surface properties you can assign for the wall....

Jade M October 21, 2010 12:06

That's right, if you are just doing CFD, then it will only allow you to assign values to the boundaries.

It sounds like you are interested in a conjugate heat transfer problem. In that case, you would need to like a Thermal analysis to CFX. Then the temperature of the solid-liquid interface becomes part of the solution. Temperatures or heat fluxes can be applied to the boundaries of the fluid and solid regions.

Steffen October 22, 2010 05:20

its just, could not find, how to assign temperatures in Ansys. Only surface roughness and velocities. What I am trying to do is natural convection, different temperatures both sides of the air gap and this will start to make the air move. Then see how it behaves with different thicknesses of the air gap.

michael_owen October 22, 2010 10:15

If you can't see where to assign boundary temperatures it's because you are using an Isothermal energy equation. Switch it to Thermal Energy on the Fluid Models tab of the Domain definition.

Steffen October 25, 2010 05:42

seems to work, thanks! Found a tutorial on boundary conditions in the www...


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