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ChemE 260 Equations of State

ChemE 260 Equations of State. Dr. William Baratuci Senior Lecturer Chemical Engineering Department University of Washington TCD 2: E & F CB 2: 6 – 8, Supplement. April 4, 2005. Equations of State. Relationship between Ideal Gas EOS : Universal Gas Constant: R

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ChemE 260 Equations of State

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  1. ChemE 260 Equations of State Dr. William Baratuci Senior Lecturer Chemical Engineering Department University of Washington TCD 2: E & FCB 2: 6 – 8, Supplement April 4, 2005

  2. Equations of State • Relationship between • Ideal Gas EOS: • Universal Gas Constant: R • R = 8.314 J/mol-K = 0.082054 L-atm/mol-K = 1.987 Btu/lbmole-oR • When does the IG EOS apply ? • When molecules interact very little with each other • At high T and low P • Generally: • Diatomic gases are especially unlikely to interact Baratuci ChemE 260 April 4, 2005

  3. Advanced Equations of State • Compressibility Factor EOS (graphical) • Virial EOS • Van der Waals EOS • Redlich-Kwong EOS • Soave-Redlich-Kwong EOS Baratuci ChemE 260 April 4, 2005

  4. Compressibility Factor EOS • Compressibility Factor: • Principle of Corresponding States • Reduced Properties: • Compressibility Charts • Z vs PR • Curves of constant TR • Curves of constant Baratuci ChemE 260 April 4, 2005

  5. Virial EOS • Uses a power series expansion to describe deviations of Z from 1, the IG value • B, C, D, etc are the Virial “constants” • functions of T, only • Determined experimentally • Truncated Virial EOS: • Estimating B: Baratuci ChemE 260 April 4, 2005

  6. Van der Waals EOS • First cubic EOS • Constants have physical interpretation Baratuci ChemE 260 April 4, 2005

  7. RK & SRK EOS’s • Redlich-Kwong • Soave-Redlich-Kwong Baratuci ChemE 260 April 4, 2005

  8. Applications of EOS’s • Given any 2 of the 3 variables, determine the value of the unknown • Cubic EOS’s and other even more sophisticated EOS’s can be used to… • predict properties of liquids • Estimate molar internal energies, enthalpies and entropies of gases and liquids • In this way, sophisticated EOS’s are used to generate the Thermodynamic “Data” Tables that we use Baratuci ChemE 260 April 4, 2005

  9. Next Class • Problem Session ! • After that… • Chapter 3 – Heat Effects • Internal Energy and Enthalpy • Using the NIST Webbook Baratuci ChemE 260 April 4, 2005

  10. Example #1 • An Application of Equations of State • Estimate the pressure of ammonia at a temperature of 22oC and a specific volume of 0.600 m3/kg. • The Ideal Gas EOS • The Virial EOS • The van der Waal EOS • The Soave-Redlich-Kwong EOS • The Compressibility Factor EOS • The Steam Tables Baratuci ChemE 260 April 4, 2005

  11. Example #1 – Answers • Ideal Gas: Ans.: P = 288.2 kPa • Virial: Ans.: P = 280.6 kPa • van der Waal: Ans.: P = 283.6 kPa • SRK: Ans.: P = 281.5 kPa • Z-Factor: Ans.: P = 282.0 kPa P = 281.0 kPa • Steam Tables: Ans.: P = 281.7 kPa Baratuci ChemE 260 April 4, 2005

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