[alikashif]

Hi,Everyone hope all of you are good in health and doing well. I am using fluent
to heat transfer between two circular tubes.after the completion of simulation I check Results. when i see temperature contour there is nothing change in inner tube but the heat is transfer occurred in mid wall.But In Temperature Contour Color is same from start to end. What do You thinks what's the problem with this why heat transfer did't show in inner tube. I also Attached Temperature contour with Please Aslo check that.
Thanks in advance.

[Comi]

Hi, could you describe the boundary conditions of your model please?

Thank you very much

[alikashif]

Yeah Sure,
There are three Interiors.Two is for two Fluid and one is Solid interior between the two fluids.
Two Velocity inlet for two Fluids. The fluid type is Counter Flow.
Two pressure outlet for both fluids
And three walls one is external and two walls are solid walls.

[alikashif]

Int-Fluid 1=interior Default
Int-Fluid 2 =interior Default
Int-Solid =interior Default
Wall-inlet = Wall
Wall-outlet= Wall.These two are solid Inlet face and outlet face
Inlet Fluid 1= Velocity Inlet
Inlet Fluid 2 =Velocity Inlet
Outlet Fluid 1= Pressure Outlet
Outlet Fluid 2 = Pressure Outlet
Wall External = Wall
Wall Internal = Wall
Wall Mid = Wall

[ares]

Do not look at contour only, it can be deceiving. You can compute inlet and outlet mass weighted average static temperature of the inner fluid. To me, it seems that the system is not enough to heat the inner fluid. Did you check Cp value? And try isolating external wall by giving 0 heat flux, this way heat would only be transferred to inner tube. Also check that thermal condition for inner wall is coupled. By the way there should be some shadow walls, did you just not write them or are they missing?

[alikashif]

Yes I Compute inlet and outlet mass weighted average static temp is same on outlet which I give On inlet.and the other thing you are talking about isolating external wall heat flux yes I already given this value 0.The shadow Walls I just don't write it.

[ares]

Checking carefully your temperature contour, indeed the heat loss from outer fluid is towards inner pipe. You can also compute or check from reports total heat transfer flux from/to inner wall. It should be different than 0. That heat flux should increase or decrease inner fluid temperature accordingly. Most probably, your heat exchanger is insufficient. Check material properties and mass flow rates.