Update of values for Modelica.Constants according to codata2017

[HansOlsson]

Update of values for Modelica.Constants
Closes #2207
The values are already more correct that previous ones, and from 2019-05-20 they will be likely be final; except for G and T_zero (on the other hand the triple point for water (suitably defined) will be 273.16K).

Watch live: https://www.youtube.com/watch?v=qA67T7FPBME

[beutlich]

Should we also set the previous value in the comment when it was changed?

[HansOlsson]

Should we also the previous value in the comment when it was changed?

Hmm... I see two possibilities: add date when changed, or just remove previous values. Considering that it will not change in the future the latter seems better.

[beutlich]

the latter seems better.

OK.

[HansOlsson]

Hmm.. It could stay, or could reference https://www.bipm.org/en/CGPM/db/26/1/ - I'll update to the latter; as it seems more future-proof.

[beutlich]

@MartinOtter I resolved the merge conflict. Can you please update your review as library officer of Modelica.Constants. Thanks.

[beutlich]

@HansOlsson The link https://www.bipm.org/en/CGPM/db/26/1/ seems to be no longer valid.

[HansOlsson]

@HansOlsson The link https://www.bipm.org/en/CGPM/db/26/1/ seems to be no longer valid.

I just tested it with 3 browsers without any issue.

[beutlich]

@HansOlsson The link https://www.bipm.org/en/CGPM/db/26/1/ seems to be no longer valid.

I just tested it with 3 browsers without any issue.

Right. Can no longer reproduce the error.

[beutlich]

@MartinOtter I resolved the merge conflict. Can you please update your review as library officer of Modelica.Constants. Thanks.

Unfortunately, there was no feeback by the Library Officer within 2 weeks.

[mestinso]

What is the meaning of the following comment:

Note that T_zero is not exact, instead the triple point of water is 273.16 K.

My understanding is that absolute zero is still precisely defined (0K / -273.15 C)...
Meanwhile, triple point of water is now no longer precise: 273.16000 K +- 0.00010 K
where the 0.00010 figure comes from 273.16*3.7e-7 taken from here: https://www.bipm.org/en/CGPM/db/26/1/

[HansOlsson]

My understanding is that absolute zero is still precisely defined (0K / -273.15 C)...
Meanwhile, triple point of water is now no longer precise: 273.16000 K +- 0.00010 K

Ah, you are right - I must have misread or read a previous version - will update.

Obviously absolute zero is still 0 K.
And Kelvin is determined from a fixed value of Boltzman constant, and degree Celsius just differs by 273.15 K.
Thus the triple point of water (about 273.16 K, 0.01 degree C) and "normal" freezing point (about 273.15 K, 0 degree C) both need to be experimentally determined.