# (Star-CCM+) Arrhenius Equation

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October 27, 2021, 18:16
(Star-CCM+) Arrhenius Equation
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TommyK
Join Date: Oct 2021
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Thanks to everyone who visited.
In short, I want to use other Arrhenius Equation. not provided by STAR-CCM+.

In Star-CCM+, provided Arrhenius Equation is
k = A*(T^b)*exp(-Ea/(Ru*T))
A : pre-exponent factor
b : constant
Ea : Activation Energy
Ru : Universal Gas Constant
T : Temperature

But, I want to use Arrhenius Equation like
k = A*([Co]^n) * exp(-Ea/(R*T))
A : pre-exponent factor
[Co] : Concentration of Oxygen
n : constant
Ea : Activation Energy
R : Universal Gas Constant
T : Temperature

In case of b = 1 & n = 1,

Star-CCM+ equation looks like
k = A*(T)*exp(-Ea/(Ru*T))

The equation what I want (from now on I call it B) looks like
k = A*([Co]) * exp(-Ea/(R*T))

The Difference between Star-CCM+, B is only T/[Co]

So I try to put A as field function
A = constant(original b's constant) * \${MolarConcentrationO2} / (\${Temperature})

But this method gives me error
I attached error message as image.

I thought the reason of this error is because of unit difference
So I tried
1.8 * \${MolarConcentrationO2} / (\${Temperature} * \${Transpose of T})
Transpose of T : 1/K

But this gives me error too..

Is there any method to change Arrhenius Equation from STAR-CCM+ to B?
Attached Images
 error message.jpg (30.9 KB, 5 views)

 Tags arrhenius equation, field function, star-ccm+