Modeling micron size features
Modeling micron size features
(OP)
I am trying to do static thermal modeling of a box with the following dimensions:
W: 0.400mm
L: 1.500mm
T: 0.0035mm (3.5um)
One side of this box generates heat and flows to a big heat sink below at a fixed temp. The big heat sink is much bigger (100x) than the heat source.
After many adjustments, COSMOS sucessfully created a mesh for the model. However, when i apply a heat load on one of the surfaces of the little box, the heat fails to conduct to its adjacent surfaces. I've tried setting bonded contacts, but the heat just wont flow.....
Any thoughts?
Thanks!
M.
My Specs: P4 2.4Ghz, 1GHz RAM, not very good video card (so sloooow......upgrading soon)
W: 0.400mm
L: 1.500mm
T: 0.0035mm (3.5um)
One side of this box generates heat and flows to a big heat sink below at a fixed temp. The big heat sink is much bigger (100x) than the heat source.
After many adjustments, COSMOS sucessfully created a mesh for the model. However, when i apply a heat load on one of the surfaces of the little box, the heat fails to conduct to its adjacent surfaces. I've tried setting bonded contacts, but the heat just wont flow.....
Any thoughts?
Thanks!
M.
My Specs: P4 2.4Ghz, 1GHz RAM, not very good video card (so sloooow......upgrading soon)






RE: Modeling micron size features
I suspect somehow that's too small for the mesh to catch?
RE: Modeling micron size features
You might also investigate your problem by using the following relationship to calculate the required time step size:
L^2/(4.alpha)
where
L = element dimension or conducting length in heat flow direction
alpha = diffusivity = k/(ro.C)
RE: Modeling micron size features
If you're worried about the dimensions of the problem then choose some other units, such as micro mm so that your dimensions are 400 x 1500 x 3.5 and modify your conductivity and heat transfer coefficients accordingly. I would doubt that the size of the heat source has little to do with the problem though, but perhaps other sources of heat loss dominate the heat flow rather than the conductivity to other surfaces. Check your material properties too to make sure you have the right units.
corus
RE: Modeling micron size features
Yes, you're right about time step not being applicable to steady state heat flow, Corus. In fact I read over "static" without realising he meant steady state.
That said, sometimes a different approach, like having a look at transient heat flow, also might be informative.
Regards