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Heat flux (type 2) boundary condition with fluid flow - tflux_eshcc??
Posted 08.06.2011, 16:25 GMT-4 2 Replies
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Hi,
I am specifying an incoming amount of energy (Ein) along a boundary [W m-2]. Fluid flows out of the model through the same boundary.
Does COMSOL automatically remove the energy (heat) contained in the fluid that is convecting through the boundary? Or do I need to specifically subtract that amount of heat (cflux_eshcc) from the boundary condition (Ein-cflux_eshcc)?
Also, is convective heat flow OUT of the model always negative, or does it depend on the coordinate system?
Thanks much,
(suggestions on where this type of information is found in the manual/literature would be greatly appreciated)
I am specifying an incoming amount of energy (Ein) along a boundary [W m-2]. Fluid flows out of the model through the same boundary.
Does COMSOL automatically remove the energy (heat) contained in the fluid that is convecting through the boundary? Or do I need to specifically subtract that amount of heat (cflux_eshcc) from the boundary condition (Ein-cflux_eshcc)?
Also, is convective heat flow OUT of the model always negative, or does it depend on the coordinate system?
Thanks much,
(suggestions on where this type of information is found in the manual/literature would be greatly appreciated)
2 Replies Last Post 09.06.2011, 11:40 GMT-4
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Posted:
1 decade ago
Hi
in V4 you need to define an outflow BC for the thermal boundary loosing heat via flow.
In general you must ensure, for multiphysics cases, that you define enough and coherent BCs FOR EACH physics independently AND linked. It's a good exercicie to structure your model hence your thinking (or the opposite)
In case of doubts, I always turn on the equations and check them to be sure I understand what is going on ;)
--
Good luck
Ivar
in V4 you need to define an outflow BC for the thermal boundary loosing heat via flow.
In general you must ensure, for multiphysics cases, that you define enough and coherent BCs FOR EACH physics independently AND linked. It's a good exercicie to structure your model hence your thinking (or the opposite)
In case of doubts, I always turn on the equations and check them to be sure I understand what is going on ;)
--
Good luck
Ivar
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Posted:
1 decade ago
Just to make sure I understand...
-n.N=No; N=-Keq(delT)+Cl*u*T
where No is the inward heat flux.
If No=0, the boundary is thermally insulated and heat will not enter or leave the system through that boundary?
If No=tflux_eshcc (total heat flux from convection and conduction in porous media), heat will be removed from the system based on the heat reaching the boundary via conduction and convection.
So if the incoming energy is Ein, and there is outward flow of warmer fluid, the boundary heat flux needs to be assigned as: Ein-tflux_eshcc
still learning...
-n.N=No; N=-Keq(delT)+Cl*u*T
where No is the inward heat flux.
If No=0, the boundary is thermally insulated and heat will not enter or leave the system through that boundary?
If No=tflux_eshcc (total heat flux from convection and conduction in porous media), heat will be removed from the system based on the heat reaching the boundary via conduction and convection.
So if the incoming energy is Ein, and there is outward flow of warmer fluid, the boundary heat flux needs to be assigned as: Ein-tflux_eshcc
still learning...