Dicrepancy between calculated and called specific enthalpy values for hydrogen

[Tuur Knevels]

Hello there,

I'm trying to calculate properties at various stages in a hydrogen based system.

Typically I try to find mass specific enthalpy using the following command:

 

which works fine.

In a different section I also find the mass specific coefficient of constant pressure, cp:

This also works find and give realistic values.

However, in a later stage I found a discrepancy when I calculate a different variable based on either h or cp

To my understanding h = cp*T. But when I calculate the mass specific enthalpy in this manner, multiplying the called value of cp with the temperature it was called for, I find a different value for h. In total scope the difference is small but unfortuately nog negligible.

Calculating the dh in a different way and finding the delta:

H_diff_lst results

Could somebody explain this discrepancy to me?

Or direct me to which one is more correct, the cp value or the H value?

Thank you in advance!

[Ian Bell]

First off,  please read the first FAQ: https://github.com/CoolProp/CoolProp/blob/master/FAQ.md 

In short, h is not equal to cp*T. A change in enthalpy can be approximated, but only approximated, as cp*T

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