CFD Simulation Film Coeficient

[inventor111]

At first I want to apologize for my bad english.

I have some troubles with the CFD Simulation. I want to simulate an extruder of an 3D printer. In my opinium when you have two different materials you have to enter the film coeficient. But the film coeficient is impossible to know or to calculate. Therefore I have aquestion? Is it necessary to enter the film coeficient or is it the false way what I did? 

I am very thankful for your ansers.

[Jon.Wilde]

You should never assign internal Surface Boundary Conditions, CFD will calculate all of that for you so no, if I understand correctly, you do not need to apply this.

Thanks,

Jon

[inventor111]

Thank you. I have thought that, but I think I make a big mistake. So I describe the way how I did my simulation.

1.) I assigned the materials inclusive air

2.) Then I enter Heat Generation to the catridge heater under Boundary Conditions.

3.) Mesh Sizing

4.) I click Solve and after the Simulation it comes: 

*** Heat Transfer was disabled because either no thermal boundary conditions were found or the applied conditions are insufficient.

I hope I have described my problem.

Thank you for your help. I would be very gladful if you could help me.

[Jon.Wilde]

You need a reference/ambient temperature somewhere. Use a temp or a film coeff on an external surface.

[inventor111]

Thank you I think that was my problem. Nevertheless I have a few questions.

1.) Is ist necessary to have air in every where were air is?

2.) The only thing I have to apply under boundary counditions is Temperature at the surfaces of the air and heat generation where the heat is generated. Are I'm right?

Thank you for your answers

inventor111