[Kwiaci]

Hello Everyone!

I'm new here and it's my first post. I'm currently performing some heat transfer analyses in FLUENT.
I want to obtain a temperature distribution in function of time in a solid body containing 2 layers: titanium and aluminum. It is an unsteady 2D analysis. The problem is that internal wall between these solids don't transfer heat. Do you know why or what boundary condition should be used there?

Second question: does anyone know how to model in Fluent a thermal contact resistance ?

In attachment there is a plot of current result.

Thanks,
Kwiaci

[xrs333]

"coupled" type should be used.

[Kwiaci]

Thanks,
Yes I did "coupled" there by doing two interfaces there. Now it works great.

[hittie]

hi,
where did you find the coupled option? because i have also a problem for the heat transfer.

thanks

[Kwiaci]

In Gambit you make two interfaces in place where two solid are in contact. Then in Fluent you use "Grid Interface" option to couple them. Next Fluent creates a new item - shadow which is interface between these two solids. In thermal options of this boundary condition there is coupled option. That's all.

[hittie]

thanks a lot

[fufilnikku]

Hi all
I am trying to simulate a concentric tube heat-exchanger in 2D.
The heat-exchanger data is as given below:
inlet tube internal diameter = 54mm
pipe thickness = 3mm (aluminium)
Outer tube diameter = 159mm
Heat-exchanger height = 1000mm
i have meshed the whole geometry using mapped meshing in gambit with quad mesh.
I have modelled two mesh models. one with 5 zones: water-aluminium-gas-aluminium-water. Second with 3 zones: water-gas-water with walls separating the zones from each other instead of solid zones (aluminium).
inlet velocity for gas = 0.5m/s with 723 K. I%= 5% & hydraulic diameter = 0.054m
inlet velocity for water on left zone = 0.2 m/s with 323 K. I%=5% and hydraulic diameter = 0.052m
the outer tube walls are defined as adiabatic Boundary condition.
I am unable to decide the 'Boundary condition' for the walls separating water from aluminium and aluminium from gas to allow heat transfer from gas to aluminium and from aluminium to water.
In 2nd geometry with 3 zones only, how should i define the 'Boundary condition' for the walls separating water from gas to allow heat-trasnfer between gas and water. in this geometry, i am defining wall thickness as 3 mm to account for aluminium.
I can email the .cas & .msh files to anyone who could help. I would highly appreciate your help.
Thanks in advance.
Sushil

[Kwiaci]

Did you created "interface" boundary condition between aluminium and gas? It should help. It is very convenient way to do this. When you create interface don't merge lines in Gambit so you will get two lines coincident in one location. I hope it'll help a bit.

[fufilnikku]

Thanks for your reply. I am kinda new to GAMBIT but i will give it a try. I would try to create interface BC for the the 2D model.