Modeling shear-thinning medium: Temperature drop
 

Hello everyone,

I'm posting my question here because it doesn't fit into any other sub-forum. It's about the physical background of my test simulation.

I am simulating a simple pipe with an orifice plate. The pipe has a diameter of 18 mm. The orifice has a very small opening of 0.1mm. A shear-thinning medium (liquid plastic) is pressed through the opening. The mass flow inlet is on the left of the pictures. The mass flow was set to 573K (!). The pressure outlet is on the right.

[Picture: Geometry]


Since I have heard that the Cross-WLF model is the most accurate way to map a shear-thinning medium, I used a predefined Cross-WLF medium.

The result (pictures below) is generally OK. Only the temperature confuses me, as it is significantly colder (557K) at the inlet than at the outlet (573K). The way I see it, the temperature on the left side should be the same or higher, because the pressure on the left side is higher and the density is the same.

[Picture: Temperature]


Now to my question: How is the Temperature-Drop to explain? And is there a physical law that can explain the lowering of the temperature in the first chamber?

What I have already tried:
- Higher mesh resolution - same result
- Different model approach of the shear-thinning medium - same result
- Simulation with water - temperature remains constant

I am looking forward to your suggestions 😊
Thank you very much in advance.


All other important variables are listed below:
[Picture: Fields]