# ThermodynamicData Wrong Air Enthalpy

I'm using ThermodynamicData to do some calculation. By I found that there is a problem in the enthalpy of air.

Input:

temperature = Quantity[Range[200, 250, 10], "Kelvins"];
enthalpy = ThermodynamicData["Air", "Enthalpy", {"Temperature" -> temperature}];
ListLinePlot[Transpose[{temperature, enthalpy}]]


Output:

However, this is wrong, according to multiple sources.

Yet another source:

Someone already pointed out that the "difference" in enthalpy is the same, so it doesn't matter. But if I want to solve an engineering equation that involve finding a temperature corresponding to a certain enthalpy, then the result may be wrong. Can anyone help me solve that?

• This question seems more appropriate for tech support than stack exchange. – Jason B. Nov 16 '18 at 22:09

There is likely nothing wrong at all. Enthalpies are normally tabulated from a reference state. If the reference state is different, then the reported enthalpies will also vary. What matters are the relative differences. From the look of your graph, it looks like enthalpy differences between two states are the same. This is what matters.

• Matches, for example, data engineeringtoolbox.com/air-properties-d_156.html – Alex Trounev Nov 2 '18 at 17:08
• @Whelp But when I solve an engineering equation, the answer will be different. For example if I want to find the temperature of water when its enthalpy is 2300kJ/kg. – user155860 Nov 13 '18 at 8:25
• The enthalpy values between the two tables only differ by a constant. All you need to do is to align them. – Whelp Nov 14 '18 at 10:52
• I think I can also change the initial condition to fit the reference in MMA? – user155860 Nov 16 '18 at 6:31
• I think you mean the same thing as I did. Basically just adjust for the different reference state, and the calculations should be fine. – Whelp Nov 16 '18 at 9:45