Data Available: 
Thermal Conductivity 
Thermal Conductivity 

UNITS  W/(mK) 
a  2.4219 
b  1.986637 
c  1.257441 
d  0.961209 
e  9.6106 
f 
0.777857 
data range 
0.1291 
equation range 
0350 
curve fit standard error relative to data 
3.1 
Has equation of the form: 
Therefore k Solves as: 
Where:  Coefficients a – f are summarized in the appropriate table and 
T is the temperature in K (xaxis), and y is Thermal Conductivity, k to solve for.  
"erf(x)" is the Gauss error function and "exp()" is the exponential.  
NOTE:  The error function (sigmoid shape) is used to blend fits over separate temperature ranges. 
The error function ‘erf(x)’ (also known as the Gauss error function) is defined as:
(When x is negative, the integral is interpreted as the negative of the integral from x to zero.) In Excel the error function may be calculated by employing the following format ‘ERF( lower_limit, upper_limit)‘ or simply ‘ERF(value of x)‘. For example ERF(0, 1.5) = ERF(1.5) which results in the integral of error function between 0 and 1.5. Excel 2010 and later evaluate correctly for both possitive and negative values of x. Whereas earlier versions can only evaluate for positive values of x (ie x > 0). Thus one must employ –ERF(x) = ERF(x) to evaluate negative values of x properly in earlier versions of Excel (prior to 2010). 