# Saturated steam equations

I found the following paper and am attempting to put Saturated Pressure and Saturated Temperature into excel. I got Saturated Pressure to work, but can't get saturated Temperature to work.

Saturated Steam Equations Paper

Saturated Pressure (working)
=(B18+273.15)/647.096 [cacluates Tr from C]
=EXP(9.56756 + 5.39806*LN(B19) - 6.16183*(LN(B19))^2 + 1.49572*(LN(B19))^4 + 0.433*B19^5 )

Saturated Temperature (not working)
=B15/22064 [calculates Pr from kPa]
=EXP((0.00937817 + 0.000498951*B16 + 0.0000111049*B16^2 + 0.000000334995*B16^3 + 0.0000000344102*B16^4)^(-0.4))

I thought maybe it was outputting in K, but that did not solve it.

Either I didn't correctly translate the equation, or the equation is wrong. Thoughts? Thanks!

• How do you know it is not working? – user190081 Sep 13 '18 at 22:00
• I compared it to the TLV online calculator. tlv.com/global/US/calculator/steam-table-pressure.html – ericnutsch Sep 13 '18 at 22:22
• If someone prefers python: there is IAPWS module. from iapws import IAPWS97; IAPWS97(P=1, x=1).T gives 453K for 1MPa – Xpector Jun 12 at 13:25

## 1 Answer

For your temperature, the last term ^-0.4 needs to be applied to the full expression, not just the term to the power ^0.4

Ie [exp(xxx + xxx + xxx + xxx)] ^-0.4

Ok, so I realise that what Eric has is correct, I read it wrong, but I won't delete it as the comments have value.

• The parenthesizes do include the entire expression... sorry kindof hard to read on two lines like that. "exp" in excel is "e" in the math world. It needs to be done last because its just the reverse of the natural log to get T instead of ln(T). I've spent way too long looking at this... surely they checked it before publishing lol. – ericnutsch Sep 14 '18 at 5:04
• They can have typing errors too... – Solar Mike Sep 14 '18 at 5:05
• Yeah. I should probably just find some digital steam tables and run my own regression on them. Then publish some some usable equations :D Thanks for having a look. – ericnutsch Sep 14 '18 at 5:09
• I did something similar a long time ago and made an interpolation formula using vlookup several times (to get the table values either side of the target) - worked out very well for the resulting values in the table.... – Solar Mike Sep 14 '18 at 5:45
• Cool, that might be a good interim solution. Thanks! – ericnutsch Sep 14 '18 at 6:05