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Drilling
Posted May 14, 2012, 11:05 a.m. EDT Version 4.2a 1 Reply
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Good morning,
I'm doing a study of drilling in comsol, but there are some factors that I am not able to complete well.
First: I did a study of meshes and the results were almost the same ranging from a mesh of 0.05mm to 0.5mm, is this normal?
Second: I'm adding a cooling and this also is not influencing the outcome, which would be the h what would you use to cooling with water or oil?
Thank you,
Isabella
I'm doing a study of drilling in comsol, but there are some factors that I am not able to complete well.
First: I did a study of meshes and the results were almost the same ranging from a mesh of 0.05mm to 0.5mm, is this normal?
Second: I'm adding a cooling and this also is not influencing the outcome, which would be the h what would you use to cooling with water or oil?
Thank you,
Isabella
1 Reply Last Post May 14, 2012, 3:17 p.m. EDT
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Posted:
1 decade ago
Hi
Normally a model is considered "mesh stable" or "mesh independent" if the results do not differ significantly (a few %) when you double the number of elements, so it looks like your coarse mesh is sufficient (as the model is set up, any change in BC or physics might change that drastically)
Adding heat exchange too a colant should indeed change the temperature (if you have some phyics that increases the temperature). I use typically 3 to 5 [W/m^2/K] for [h] in natural (unforced) air cooling, but for water and oil it's very dfferent, and rather T dependent too, for your case. It will vary also strongly with the fluid flow (heat transport by material transport) this becomes really multiphysics. As an example I use 10 to 20 [W/m^2/K] for "h" in forced air flow.
There must be further values for water or oil in the litterature, even if for these the alpha is rather low and the heat takes ages to conduct through the fluid, compared to air
--
Good luck
Ivar
Normally a model is considered "mesh stable" or "mesh independent" if the results do not differ significantly (a few %) when you double the number of elements, so it looks like your coarse mesh is sufficient (as the model is set up, any change in BC or physics might change that drastically)
Adding heat exchange too a colant should indeed change the temperature (if you have some phyics that increases the temperature). I use typically 3 to 5 [W/m^2/K] for [h] in natural (unforced) air cooling, but for water and oil it's very dfferent, and rather T dependent too, for your case. It will vary also strongly with the fluid flow (heat transport by material transport) this becomes really multiphysics. As an example I use 10 to 20 [W/m^2/K] for "h" in forced air flow.
There must be further values for water or oil in the litterature, even if for these the alpha is rather low and the heat takes ages to conduct through the fluid, compared to air
--
Good luck
Ivar