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Defining Convective Heat flux and Heat Flux correctly
Posted May 23, 2014, 4:00 a.m. EDT Heat Transfer & Phase Change Version 4.4 1 Reply
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Hello Guys,
Im not sure how to define some fluxes in my model.
Right now im working on heat Transfer and Need a Little help from you guys. In the Picture gitter.png u'll see a grid through which my Geometrie is getting cooled. i calculated the hydrolic Diameter for a single hole (not for the whole grid) , it's D_eff and im kinda confused, if i should leave it like it is in the Picture ( one convective heat flux for the whole grid) or should i define for every single hole another convective heat flux with theese same Options ?
My second question is about cable.png , there will be copper cables attached on those 6 selected surfaces you're seeing and theese cables will take some heat away from my Geometrie, so i want to simulate them as heat sinks and defined for that purpose heat fluxes on those surfaces. But im not sure how to define the heat flux, i'll assume those cables are always at room temperature and build an Expression dependent on the cable length and the temperature of the surface its attached to. How should i define the heat fluxes in this case ?
Excuse my poor english
Greetings
Tunc
Im not sure how to define some fluxes in my model.
Right now im working on heat Transfer and Need a Little help from you guys. In the Picture gitter.png u'll see a grid through which my Geometrie is getting cooled. i calculated the hydrolic Diameter for a single hole (not for the whole grid) , it's D_eff and im kinda confused, if i should leave it like it is in the Picture ( one convective heat flux for the whole grid) or should i define for every single hole another convective heat flux with theese same Options ?
My second question is about cable.png , there will be copper cables attached on those 6 selected surfaces you're seeing and theese cables will take some heat away from my Geometrie, so i want to simulate them as heat sinks and defined for that purpose heat fluxes on those surfaces. But im not sure how to define the heat flux, i'll assume those cables are always at room temperature and build an Expression dependent on the cable length and the temperature of the surface its attached to. How should i define the heat fluxes in this case ?
Excuse my poor english
Greetings
Tunc
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1 Reply Last Post May 26, 2014, 6:29 a.m. EDT
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Posted:
1 decade ago
Hi Tunc,
I do not know about the channels.
With regards to the cables: do you have forced fluid flow around them? If not, you will have to look at the Rayleigh number to see if you get significant natural convection. If you do and you want to do it correctly I think it is best to build a full multiphysics model with heat transfer and fluid dynamics to model the heat flux in and outside the cables, together with the fluid flow around the cables. Otherwise you might be able to find a nice analytical model which you can translate into a heat transfer coeficient.
I do not know about the channels.
With regards to the cables: do you have forced fluid flow around them? If not, you will have to look at the Rayleigh number to see if you get significant natural convection. If you do and you want to do it correctly I think it is best to build a full multiphysics model with heat transfer and fluid dynamics to model the heat flux in and outside the cables, together with the fluid flow around the cables. Otherwise you might be able to find a nice analytical model which you can translate into a heat transfer coeficient.