Sea Water Thermodynamic Properties?

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Discussion Overview

The discussion centers on the thermodynamic properties of seawater, particularly specific heat and enthalpy, in the context of designing a solar desalinator. Participants explore how to determine these properties and their implications for energy requirements in evaporation processes.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks to understand how to determine the enthalpy of seawater using the enthalpy of salt and water.
  • Another participant provides specific values for the density and specific heat of seawater, citing external sources for verification.
  • A participant questions the unit of specific heat provided, suggesting a potential discrepancy with the specific heat of water.
  • Another participant references historical research on seawater thermodynamic properties, noting that these properties vary with salinity.
  • A later reply reiterates the concern about the specific heat units and suggests that the value may depend on salinity, providing an additional source for reference.

Areas of Agreement / Disagreement

Participants express differing views on the specific heat values and their units, indicating a lack of consensus on this aspect of seawater thermodynamics. The discussion remains unresolved regarding the exact values and their implications.

Contextual Notes

There are limitations regarding the dependence of thermodynamic properties on salinity and the potential for unit discrepancies in specific heat values. The discussion does not resolve these issues.

tanky322
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Im looking for thermodynamic properties of seawater, especially specific heat and enthalpy. I am designing a solar desalinator, and I am trying to determine the required amounts of energy to evaporate the water.

Is there a way in which I can determine the enthalpy of seawater by knowing the enthalpy of both salt and water?


Thank you
 
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Thank you!
 
Astronuc said:
The density of seawater is about 1025 kg/m^3 and the specific heat is about 3850 J/(kg C).

I think there is a unit issue with the specific heat of 3850 J/(Kg K), given that the specific heat of water is around 2200 KJ/(Kg K).

I just wanted to see if what I am saying here is making sense.


Thanks
 
Kaiser Engineering did an extensive research study for the government on the thermodynamic properties of seawater about 40 years ago. The properties vary with the salinity, which also varies in different parts of the seas. It is available from the Library of Congress
 
tanky322 said:
I think there is a unit issue with the specific heat of 3850 J/(Kg K), given that the specific heat of water is around 2200 KJ/(Kg K).
3850 is the right order of magnitude, depending on the salinity.

See here - no disclaimers required for this source:
http://www.kayelaby.npl.co.uk/general_physics/2_7/2_7_9.html
 

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