[fahimeh456]

Hi

I have a question. When I am writing a function Expression for fluid properties can be faced with an error.

All the fluid properties, except for the dynamic viscosity, vary linearly with temperature. The specific heat is the only quantity that increases with a rising temperature.

But my problem is specific heat capacity function Expression when I am faced with this error:

The ANSYS CFX solver exited with return code 1. No results file |

| has been created.

And its function is as follows :

807.163 [ j kg^-1 K^-1 ]+3.58 [ j kg^-1 K^-2 ]*T

But there is no problem for other functions.

Please help me that I solve this problem.

[-Maxim-]

"j" stands for Joule, right? If yes, you should probably capitalize it: "J"
If that didn't help, please share your complete "out file"

[fahimeh456]

I've changed j to J and it has no effect on the answer and the error is same as before. File is attached. Please find the attachment.
tanx
CFX13_010.txt

[Opaque]

You have a density expression for the material "oil", such expression can produce negative densities, and the solver will stop with an out of bounds error.

I would not be surprised there is an inconsistency with the properties that is driving the energy equation to high temperatures (recall you have an energy source in the solid), and the oil density can become 0 @ 1526 [K] = 1253 [C].

You may need to tune down your model one step at a time to understand what is driving the solution out of bounds.

Good luck

[Pumba]

you could set a lower limit to your density expression ( max(500[kg m^-3],yourExpression) ) just to get it running.

Then you could evaluate the unbounded expression in cfd post and look where your problem is.

[fahimeh456]

With a density function (max (500 [kg m ^ -3], 1098.72 [kg m ^ -3] -0.712 [kg m ^ -3 K ^ -1] * T))
The problem was solved without any errors.
Thank you very much for your guide

[Pumba]

But don't forget to check what caused the density to become negative in the first place. Artificial limits can lead to unphysical results

[fahimeh456]

I agree with you. I know when I write a cp expression function then it cause density to become zero or negative. But I do not know exactly how to set up Density range?

[Pumba]

you are asking the wrong questions. why does your temperature exceed 1253 [C]? Is your equation for the density even valid at that temperature?

What are you trying to simulate? Oil at over 1250°C sounds very wrong to me.

Edit: I think your copper heat capacity might be too low, so it causes the temperature to rise. Tbh i don't even understand your heat capacity function with all those steps

[fahimeh456]

I do not know why the temperature reached 1250 degrees probably I got the wrong another place of simulation.
But my question is, Can Specific Heat Capacity at Constant Pressure effect on density ?

[Pumba]

yes of course, Heat capacity affects Temperature -> Temperature affects density

[fahimeh456]

Thankful....