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-   -   Multiple Thermal Conductivity for a Material at different temperature (http://www.cfd-online.com/Forums/ansys/116373-multiple-thermal-conductivity-material-different-temperature.html)

ajhunte April 17, 2013 20:24

Multiple Thermal Conductivity for a Material at different temperature
 
I am trying to create a material in ANSYS that has a different thermal conductivity at different temperatures. I tried the following:

Creating a function "Function 1" with my data:
-Argument Units: K
-Output Units : W m^-1 K^-1

Creating an expression "Expression 1" linked to the function:
-Expression 1= Function 1(K)

This gives me the following error:
Bad expression value 'Expression 1' detected in parameter 'Thermal Conductivity' in object '/LIBRARY/MATERIAL:Zirconium/PROPERTIES/THERMAL CONDUCTIVITY'.
CEL error:
The following unrecognised name was referenced: K.

Which basically says that I can't use K as the input to my function?

vagantes April 18, 2013 02:59

Quote:

Originally Posted by ajhunte (Post 421368)
I am trying to create a material in ANSYS that has a different thermal conductivity at different temperatures. I tried the following:

Creating a function "Function 1" with my data:
-Argument Units: K
-Output Units : W m^-1 K^-1

Creating an expression "Expression 1" linked to the function:
-Expression 1= Function 1(K)

This gives me the following error:
Bad expression value 'Expression 1' detected in parameter 'Thermal Conductivity' in object '/LIBRARY/MATERIAL:Zirconium/PROPERTIES/THERMAL CONDUCTIVITY'.
CEL error:
The following unrecognised name was referenced: K.

Which basically says that I can't use K as the input to my function?

Hi ajhunte !

from the info you have given, it seems that you have tried to modify an element's properties from the MATERIALs library. Something is wrong with you re-definition. Could you provide additional info - what module of ANSYS do you use?

Possible solutions for the definition of temperature dependence of thermal conductivity:
1. if you use Transient module, you can specify temperature dependence of thermal conductivity in a Table form in the section 'Engineering Data'.
2. if you use FLUENT module, you can define a User-Defined Function (code it in C) and either compile or interpret it, and then use this function in material's properties specification. (There is a reference guide on how to make the User-Defined Functions in FLUENT).

regards,

dklastiwka April 20, 2013 10:15

This looks like it is in CFX. Try putting square brackets around K. Like this:

[K]


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