thermal expansion coefficient in FLUENT
 

Hello everyone,

my study case is transient natural convection in which I'm using boussinisq density in air property, the problem is in the thermal expansion coefficient.

-I search online, and I found a value of 0.0032 (1/k) for air.
-but I found a tutorial video in YouTube that use 0.036 (1/k),
-when I'm using a value of 0.00032(1/k) I found good results.
so my question is! is it logical if I use 0.00032 ?

and how can I know the right value in my case?

I'll be so grateful for any comments or answers.

Best wishes,

Dounia

For ideal gases, you have (see Thermal expansion). You can use more real properties if you like.

Hi LuckyTran, I am using NIST real gas model in fluent and I want to know how to access the thermal expansion coefficients via UDF?

Many thanks,
Bryce

I'm not sure if there is predefined in UDF macro to get thermal coef value

what you can do is:
1. get thermal coef value using scheme, write it to any variable
(to get this variable you may use TUI commands and pick-a-real command.
On the other hand, there should be a scheme name of variable for thermal coef which I don't know)
2. read this variable in UDF

Hi Alex,

Thanks for your advice, as I searched there is no macro to access the thermal expansion coefficients. However, I can calculate it using matlab via REFPROP (the values versus temperature). Could you give more details about your approach?

Thanks,
Bryce