Thermodynamic properties of compressed liquids

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SUMMARY

This discussion focuses on the determination of thermodynamic properties (internal energy, enthalpy, entropy, and specific volume) for compressed liquids, specifically water, at pressures below 5 MPa. The user seeks methods to calculate these properties at 0.5 MPa, referencing various resources including steam tables and thermodynamic equations. Key equations provided include the derivatives of internal energy, enthalpy, and entropy with respect to pressure, which involve the specific volume, volumetric coefficient of thermal expansion, and bulk compliance. The discussion emphasizes the importance of using established tables for coefficients and values away from the critical point.

PREREQUISITES
  • Understanding of thermodynamic properties such as internal energy, enthalpy, and entropy.
  • Familiarity with steam tables and their application in thermodynamics.
  • Knowledge of specific volume and its significance in thermodynamic calculations.
  • Basic grasp of calculus as it applies to thermodynamic equations and derivatives.
NEXT STEPS
  • Research the derivation and application of the equations for thermodynamic properties of compressed liquids.
  • Explore updated steam tables for water and other compressed liquids at varying pressures.
  • Study the volumetric coefficient of thermal expansion and bulk compliance for various substances.
  • Investigate the critical point behavior of liquids and its implications for thermodynamic calculations.
USEFUL FOR

Students and professionals in thermodynamics, chemical engineering, and mechanical engineering who require a deeper understanding of the properties of compressed liquids and their calculations.

guideonl
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TL;DR
required properties for compressed liquids
Hi All,
I have review my thermodynamic notes (~35 year ago..), and I could not able to restore how to get thermodynamic properties (u,h,s,v ..) for compressed liquids. I have found properties tables for compressed liquids ( for water..) but unfortunately the data starts at 5MPa. What if I look for properties of compressed liquids (let say water) at pressures smaller than 5MPa? let say 0.5MPa?
 
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Thank you,
It was helpfull
 
Equations that might be helpful to you are
$$\left(\frac{\partial u}{\partial P}\right)_T=(P\beta-T\alpha)v$$
$$\left(\frac{\partial h}{\partial P}\right)_T=(1-T\alpha)v$$
$$\left(\frac{\partial s}{\partial P}\right)_T=-\alpha v$$where v is the specific volume, ##\alpha## is the volumetric coefficient of thermal expansion, and ##\beta## is the bulk compliance:$$\alpha=\left(\frac{\partial \ln{v}}{\partial T}\right)_P$$and $$\beta=-\left(\frac{\partial \ln{v}}{\partial P}\right)_T$$In these equations, away from the critical point, you can treat the specific volume as constant, and values of the coefficient of thermal expansion and bulk compliance (or its reciprocal, the bulk modulus) are in tables.
 
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Likes   Reactions: Lnewqban
Sorry,
I'm not femiliar with latest formulas you noted above..
Thanks any way
 

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