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Re: Difference between "Wall" and "Wall to Ambient" radiation surface boundary condition
can you give us some context of your application? that may solidify what is described from a feature perspective.
also where exactly are you trying to create this radiative surface? wall or radiative surface? what version of the software are you using?
in general the answer is wall means wall to wall, wall to ambient means wall to ambient (environment)
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Re: Difference between "Wall" and "Wall to Ambient" radiation surface boundary condition
Hi Jared,
My requirement is to analyze the heatsink (image below) performance at natural convection.
So the heatsink with black anodized finish will be exposed to ambient atmosphere and will dissipate heat from the hot surface.
In this case, do I need to apply "wall" or "wall to ambient" to the heatsink surface?
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Re: Difference between "Wall" and "Wall to Ambient" radiation surface boundary condition
woah, thats a crazy heat sink
why are you trying to make a radiative surface? if you turn on radiation, all surfaces by default are radiative
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Re: Difference between "Wall" and "Wall to Ambient" radiation surface boundary condition
Hi Jared, we specialize in those heatsinks.
I want to exclude the surface in contact with heater from radiative surface definition.
For the default option, I chose a low emissivity value material like Aluminum polished and then define the rest of the surfaces with black anodized.
Even if use the default option, I still have the option of choosing "wall" or "wall to ambient". What do you recommend in this application?
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Re: Difference between "Wall" and "Wall to Ambient" radiation surface boundary condition
can you describe how you are setting up the analysis and post pictures of where you are seeing wall and wall to ambient?
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Re: Difference between "Wall" and "Wall to Ambient" radiation surface boundary condition
Hi Jared,
I am performing External analysis, the heatsink is exposed to open atmosphere.
All the external surface (except bottom) will participate in Radiation heat transfer.
In this case do I need to choose "wall to ambient" or "wall to wall"
I also have some other situations where the heatsink is inside the enclosure (enough clearance between Heatsink & enclosure)... What condition should I define here...
Thanks in advance for your response.
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Re: Difference between "Wall" and "Wall to Ambient" radiation surface boundary condition
if you enable radiation, radiation is on. you don't need to apply wall radiation unless you want to create an artificial source or change the properties of a particular radiative face.
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Re: Difference between "Wall" and "Wall to Ambient" radiation surface boundary condition
Hi Jared,
The default radiation option chooses "wall to wall". So I am not sure if this case is wall to wall.
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Re: Difference between "Wall" and "Wall to Ambient" radiation surface boundary condition
please post a screenshot of what you're talking about
general settings define the defaults
wall conditions (wall bc) define overrides
radiative surfaces create additional radiative elements that aren't geometry based
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Re: Difference between "Wall" and "Wall to Ambient" radiation surface boundary condition
Hi Anand
Wall to ambient: The energy that is dissipated by radiation from the fins of your heat sink is transfered to the sorroundings (ambient) and is not comming back . However, in your case due to the configuration/arragements of your fins, there is radiation from fin to fin as they see each other and they might be at different temperatures. Imagine that you only have one fin, then it is safe to assume that the energy dissipated by radiation is tranferred exclusively to the sorroundings (some will actually go to the HS-base or the table that supports your heat sink). If you have two fins, some of the energy goes to the ambient and some is exchanged between the two fins.
I hope this makes sense.
Ed
