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Time dependent heat transfer in a thin layer
Posted 03.11.2015, 06:57 GMT-5 Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD) Version 5.1 1 Reply
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I am working on heat transfer through fluid no1-solid (thin layer)- fluid no2. The simulations is transient and the time elapsed during heat transfer from fluid no 1 to fluid no2 is relevant (actually it is the point of the simulation). Does thin layer model account for the time delay during the heat transfer?
1 Reply Last Post 04.11.2015, 02:49 GMT-5
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Posted:
9 years ago
Hi
"Time delay" is rather the question does your "thin" model consider "resistivity" (k only) or "conductance" (k, rho, Cp)
For Thin Layer (solid) you can choose, check the equation used for the appropriate solver, for Thin Film (fluid) the physics consider (k, rho, Cp). But the main hypothesis is that there is only a gradient normal to the "thin" boundary.
The easiest in COMSOL to check the physics setting, and to ensure you understand fully the BC conditions is to make simple "toy models", in this case make a 2D HT model with two blocks one with a boundary in the middle (thin boundary layer) the second block with a physical domain layer of the desired thickness, then add the same material properties to the domains and to the thin layer boundary and solve both with a constant T (higher than the initial 20°C on the lower boundaries of each block.
You can use a general extrusion to observe the temperature difference between the two blocks
Thin layers are only reasonably correct when the layer are "thin" compared to the bulk model.
One caveat, be sure you resolve correct your thin domain with at least 3 mesh elements across to get a reasonable gradient value
--
Good luck
Ivar
"Time delay" is rather the question does your "thin" model consider "resistivity" (k only) or "conductance" (k, rho, Cp)
For Thin Layer (solid) you can choose, check the equation used for the appropriate solver, for Thin Film (fluid) the physics consider (k, rho, Cp). But the main hypothesis is that there is only a gradient normal to the "thin" boundary.
The easiest in COMSOL to check the physics setting, and to ensure you understand fully the BC conditions is to make simple "toy models", in this case make a 2D HT model with two blocks one with a boundary in the middle (thin boundary layer) the second block with a physical domain layer of the desired thickness, then add the same material properties to the domains and to the thin layer boundary and solve both with a constant T (higher than the initial 20°C on the lower boundaries of each block.
You can use a general extrusion to observe the temperature difference between the two blocks
Thin layers are only reasonably correct when the layer are "thin" compared to the bulk model.
One caveat, be sure you resolve correct your thin domain with at least 3 mesh elements across to get a reasonable gradient value
--
Good luck
Ivar