Cold sink in the element:Heat Transfer problem
Cold sink in the element:Heat Transfer problem
(OP)
I am trying to simulate LENS deposition process. But to start with simple I have been running a Heat transfer analysis where I have one deposit block which I removed in step-1 and added in step-2 and I am encountering a cold sink problem in the activated deposit block, although analysis completes without any errors. I have attached a detailed word document with few pictures and would be grateful if you can tell me where I am going wrong.
http:// files.engi neering.co m/getfile. aspx?folde r=180b3052 -5340-4265 -a23f-e34c 86a728c3&a mp;file=AB AQUS_HT_pr oblem.docx
http://





RE: Cold sink in the element:Heat Transfer problem
Tata
RE: Cold sink in the element:Heat Transfer problem
I will run the analysis by refining mesh. But can you tell me what you mean by initial time step?.
RE: Cold sink in the element:Heat Transfer problem
Refined the mesh:
Deposit block has 4000 elements and reduced the initial step time from 0.5 to 0.00005 and still the problem persists. Also, the step completes half the way (i.e. no conduction along the entire length of the block and of course not into substrate. If I add an additional step-3 and just carry HT it finishes with one increment only (i.e. no cooling).
http://
RE: Cold sink in the element:Heat Transfer problem
If you apply a heat flux to one surface and insulate everywhere else then temperatures will tend towards infinity over time. I think that is happening in this case.
You should also try and use symmetry to reduce the size of the problem, or even consider using a 2D mesh
Tata
RE: Cold sink in the element:Heat Transfer problem
I have tried to refine mesh in the regions where there is problem with the nodal temperature, tied the surfaces, gave very high gap conductance but the problem still persists. The file attached now has last two modifications made. I have no idea why this is happening. I have not used anything fancy here expect for model change.
http://
RE: Cold sink in the element:Heat Transfer problem
Where you have apparently made a single part it appears that you can see that the temperatures aren't equal at the intersection of the 'two' parts, for some reason. The contours of NT11 should run across the 'two' parts but don't. It suggests that the single instance is a still two parts.
The instability in the solution is common in severe transients and does damp out as the solution continues through time. Try modelling it in 2D or 1D and put a very fine mesh, biased twards the point where the heat flux is applied and you should see an improvrmrnt. My guess is you'll still see some instability where, mathematically, temperatures appear to reduce below the position in which the flux is applied. I tend to ignore these discrepancies where they occur in the very initial period of the transient as they quickly disappear and the solution smoothes to a more reasonable result.
Tata