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Old   August 2, 2016, 11:55
Default CEL and variable
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Casper
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Hi All!

How to define density or thermal conductivity variables? When I defined value in CEL expression, it doesn't change like a constant. How Can I define it?
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Old   August 2, 2016, 16:27
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Quote:
Originally Posted by Casper_07 View Post
It doesn't change like a constant.
....I'm confused, can you explain a little more what you are trying to do exactly?

Are you trying to make it a variable of temperature or something?
You have to make an expression in the format: 0.2 [W/m/K^3]*T^2+ 0.2 [W/m/K^2]*T + 0.5[W/m/K]

Last edited by evcelica; August 3, 2016 at 13:43.
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Old   August 2, 2016, 21:38
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is it polynomial function? which you described it . I am going to define two points. And then it should be found variables.
For instance, T= 300[K] , rho=1.17[kg/m^3], cp=1005.7[J/kg/K], thermal conductivity 0.02624[W/(m/K)] dynamic viscosity 18.46x10^-6
T= 1500[K] , rho=0.235[kg/m^3], cp=1230[J/kg/K], thermal conductivity 0.094[W/(m/K)] dynamic viscosity 54.46x10^-6[Pa/S]
How to create like variables?
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Old   August 2, 2016, 22:46
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You can define functions for all these properties (CEL expressions, interpolation functions, user fortran etc) and then you make them define the material properties in the materials tab.
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Old   August 3, 2016, 13:43
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Be careful using functions for both density and specific heat, it can lead to thermodynamic inconsistencies. Use ideal gas instead to avoid this. (Or Constant Specific Heat, which you probably don't want to do)

For your conductivity, if using linear curve fit, it would be:
(5.64667*10^-5)[W/m/K^2]*T + 0.0093[W/m/K]
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