Learning Forum

[Pierre Drut]

Good afternoon,

I'm trying to design a protection cover going over a steel pipe and used to insulate the pipe. I have represented below a simplified model. The various parts of the model are as per discruption below: Insulation cover (in red) / Air gap / Internal gaz / Steel pipe.

In reality the model is more complex but I have made some simplification here for better comprehension.

This is for a cool down analysis where the internal gas (in yellow) will be heated up to approx 80°C. When gas flow is shut down, during a given time, the area under the insulation cover (in red) must stay above a given temperature. My client is asking to use CFD (Fluent) rather than a typical transient thermal within workbench to assess the convection effect of the air entraped (in green) and also in the internal gas (in yellow).

1. I assume that there won't be any gas circulation during cool down. Is it possible within Ansys fluent to specify no inlet or outlet? or we must have some inlet and outlet to perform such analysis.
2. I want to set-up the internal gaz to be at 80°C a t=0s and let the gas cool down for 1hr (for example). How to do that within Ansys fluent? External surfaces of the assembly will be at 4°C.
3. How to asign the starting temperature to the gas? I can asign a temperature to a surface but it seems not possible to asign a temperature to the full internal gaz?

Thanks in advance for your help

 

[Rob]

You can model a sealed fluid zone, just make sure you use an ideal gas or Bousinesq for density: the gas is going to move due to buoyancy. The initial conditions will need to be patched, this means you can set different zones at different temperatures. 

Re the external surfaces, I'd reconsider fixing a temperature.