Jump to content

Featured Articles

Check out the latest featured articles.

File Library

Check out the latest downloads available in the File Library.

New Article

Product Viscosity vs. Shear

Featured File

Vertical Tank Selection

New Blog Entry

Low Flow in Pipes- posted in Ankur's blog

- - - - -

Water Entropy Estimation

entropy and enthalpy of water

3 replies to this topic
Share this topic:
| More

#1 ahmedi


    Brand New Member

  • Members
  • 1 posts

Posted 19 December 2021 - 04:53 AM



I have a question. The standard molar entropy of subcooled/compressed water (25oC, 1 ATM) is given as 70 J/mol. K. When it is converted to J/gm K the value comes about 3.88 J/kg K. But when we look at the steam tables the value of saturated liquid water entropy is given (25 C, 3.6 kPa) as 0.367 J/kg. K. I could not figure out why there is so much of a difference? As we know, entropy is not a strong function of pressure at a given temperature. Could someone kindly throw light on it please?


S_o (25 C, 101.32 kPa) = 3.88 kJ/kg.K

S_sat (25 C, 3.6 kPa) = 0.367 kJ/kg K  


#2 latexman


    Gold Member

  • Admin
  • 1,320 posts

Posted 19 December 2021 - 07:02 AM

Are these two values from two different steam tables?  They may use different reference conditions.

#3 Said Salim

Said Salim

    Gold Member

  • Members
  • 85 posts

Posted 20 December 2021 - 02:28 PM

You may check the reference temperatures in both sources.As far as I know the triple point is the reference in IAPWS-97.
You check what is the reference temperature when calculating specific standard entropy to get the value of 3.88 kJ/kg.K

Edited by Said Salim, 20 December 2021 - 02:31 PM.

#4 breizh


    Gold Member

  • Admin
  • 5,378 posts

Posted 20 December 2021 - 11:52 PM


Consider this link to support your work (calculators )



Reply to this topic


Similar Topics