convective heat transfer, how?

Steffen · August 14, 2010, 08:19

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...

August 14, 2010, 08:19	convective heat transfer, how?	#1
Steffen New Member Steffen Heidrich Join Date: Aug 2010 Posts: 6 Rep Power: 15	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

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August 16, 2010, 12:57		#2
neilduffy1024 Member Neil Duffy Join Date: Mar 2010 Posts: 34 Rep Power: 16	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

August 17, 2010, 06:04		#3
Steffen New Member Steffen Heidrich Join Date: Aug 2010 Posts: 6 Rep Power: 15	seems its just surface properties you can assign for the wall....

October 21, 2010, 12:06		#4
Jade M Senior Member Join Date: Feb 2010 Posts: 148 Rep Power: 17	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.

October 22, 2010, 05:20		#5
Steffen New Member Steffen Heidrich Join Date: Aug 2010 Posts: 6 Rep Power: 15	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.

October 22, 2010, 10:15		#6
michael_owen Senior Member Michael P. Owen Join Date: Mar 2009 Posts: 196 Rep Power: 17	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.

October 25, 2010, 05:42		#7
Steffen New Member Steffen Heidrich Join Date: Aug 2010 Posts: 6 Rep Power: 15	seems to work, thanks! Found a tutorial on boundary conditions in the www...