Learning Forum

[hurch346]

Hello,

I'm currently modelling a heat exchanger in ANSYS Fluent that exhibits periodic symmetry. In practice, the heat exchanger has many repeating ducts, but for simplicity and to reduce computational cost, I am only simulating two ducts.

My domain consists of:

• A cold fluid stream (flowing horizontally),

• A hot fluid stream (flowing vertically),

• A wall separating the two streams (inner wall),

• And a second wall enclosing the hot fluid (outer wall).

To represent the periodic nature of the full heat exchanger, I want the outer face of the cold fluid, and the outer wall (represented by the red and black dashed lines) to transfer heat to each other, as if the geometry repeated. I’ve attempted this by defining the two outer faces as a mesh interface in Fluent.

This created:

• intf:01:coldinterface::wallinterface

• intf:01:coldinterface::wallinterface-shadow

Both are set to "coupled" under Thermal Conditions. I also have the energy equation enabled and inlet/exit boundary conditions set. 

However, the simulation does not show any heat transfer occurring between these faces. Just to clarify:

• There is heat transfer between the hot and cold fluid domains through the inner wall.

• There is no heat transfer through the outer wall (where the coupling is intended).

Any suggestions on what might be going wrong or what I should double-check would be greatly appreciated. I am unable to do a periodic boundary condition due to having multiple fluid domains.

Thanks in advance!

[Rob]

The coupled option is for direct contact wall, and the interface is intended for touching surfaces. Now, if you can set the periodic non conformal (turn off one-to-one coupling for the older GUI panel) you can set non conformal periodics. However, you can't have a solid zone on a translational periodic as that breaks the maths. 

Assuming it's a PHX stack you might be able to model hot/cold channel with half of the cold/hot channel on each side. The outer faces could then be symmetry.