# Enthalpy equation

1. Jun 28, 2008

### ZachGriffin

Hi guys,

I'm trying to implement the enthalpy equation in C++ converting it from an excel macro I found on this forum. I'm having a problem with the results which I think is as a result of having the incorrect order of operations. Can somebody help with the order of operations for this with brackets? Any help is much appreciated.

The enthalpy equation:
Code (Text):
H/(R*T) = A1 + A2*T/2 + A3*T^2/3 + A4*T^3/4 + A5*T^4/5 + A6/T

The macro equation:
Code (Text):

H = H + W * r * t * (a1 + t * a2 / 2 + t ^ 2 * a3 / 3 + t ^ 3 * a4 / 4 + t ^ 4 * a5 / 5 + a6 / t)
My Implementation:
Code (Text):
ocpcOxidantEnthalpy += w * universalGasConstant * ocpcOxidantTemperature * (fuelContainer.a1 + ocpcOxidantTemperature * fuelContainer.a2 / 2 + Math::Pow(ocpcOxidantTemperature,2) * fuelContainer.a3 / 3 + Math::Pow(ocpcOxidantTemperature,3) * fuelContainer.a4 / 4 + Math::Pow(ocpcOxidantTemperature,4) * fuelContainer.a5 / 5 + fuelContainer.a6 / ocpcOxidantTemperature);

2. Sep 16, 2008

### Mike222

I think that power is fractional 2/3, 3/4, 4/5.
Could you please provide the values of A1 to A6 you are using?
Regards,
Mike.