Concentric Tube heat-exchanger: Final year Project Help
 

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

When i use air in all the fluid zones, i get heat transfer across the zones. However, it fails to show any heat transfer when water is used the surrounding fluid around Gas zone. the flow in the tubes is parallel.

Mail me the files. May be I can help you..!

hello
 

hello there, i have almost the same problem but using STARCD not fluent : (
if any one can help it will be nice !