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chapter 2 Properties of Pure Substances

chapter 2 Properties of Pure Substances. 2-1 Pure Substance. 2-1-1 Definition of Pure Substance A homogeneous substance is pure substance 2-1-2 Phases of Pure Substance Solid Liquid Gas Plasma. 2-2 Phase Change Process of Pure Substance.

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chapter 2 Properties of Pure Substances

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  1. chapter 2 Properties of Pure Substances

  2. 2-1 Pure Substance 2-1-1 Definition of Pure Substance A homogeneous substance is pure substance 2-1-2 Phases of Pure Substance Solid Liquid Gas Plasma

  3. 2-2 Phase Change Process of Pure Substance 2-2-1 Constant Pressure Process of Water

  4. p T 4” 5” 5 5’ 3” 4” 5” 1” 2” 3’ 4’ 5’ 4’ 1’ 2’ 1 2 3 4 5 2” 2’ 2 3” 3 3’ 4 1 1’ 1” v v Critical point p Liquid vapor solid Liquid +solid Liquid +Vapor Triple line Solid+Vapor T T=constant c c

  5. 2-2-1 Properties of Water 1.One point： Critical point C 2.Two lines： Saturated water line, Saturated vapor line 3.Three Regions: Compressed water region, Saturated mixture region, superheated vapor region 4.Five states: Compressed water, Saturated water, Saturated mixture, Saturated vapor, superheat vapor

  6. 2-3 P-v-T surface and P-T diagram 2-3-1 p-v-T Surface

  7. Extract on freezing 2-3-2 p-T diagram Critical point Melting line Expand on freezing P liquid Vaporization Solid Vapor Sublimation T

  8. 2-4 Property Tables 2-4-1 Saturated Liquid and Vapor One property is enough to Calculate other properties. Enthalpy ---- the combination property: H=U+PV Or, per unit mass h=u+Pv

  9. 2-4-2 Saturated Mixture Oneproperty to calculate saturated properties, but how to determine the properties of saturated mixture? One special property to calculate the fraction of liquid and vapor, the quality

  10. 2-4-3 Superheated Vapor Two independent properties are used to Calculate other properties

  11. 2-4-4 Reference state and reference value Water: Saturated liquid at 0.01 ℃ is taken as the reference state, where u=0 s=0 R-12: Saturated liquid at -40 ℃ is taken as the reference state, where u=0 s=0 Notice:The reference state differ with different tables

  12. 2-5 The Ideal-Gas Equation of State 2-5-1 The Ideal-Gas The molecules of ideal-gas have no volume There are no attraction among molecules of ideal-gas 2-5-2 The Ideal-Gas Equation of State (1). pV = mRT pv=RT R------The gas constant (2)pVm = μRμT pvm=RμT Rμ-----The universal gas constant = 8.314kJ/kmol.K

  13. 2-6 Real Gases 2-6-1 Compressibility Factor Pv=RT can only be employed for the gas under high temperature or low pressure For real gas, from pv=RT : z------- Compressibility Factor: a measure of deviation from ideal-gas behavior z=1: Ideal-Gas z>1 or z<1: Real-Gas

  14. 2-6-2 Van der Waals Equation of State (1)consider the volume occupied by the molecules themselves from pv=RT : Since the smaller space for the molecules flying will lead to more chance of hit on its container ,the pressure of the gas will increase then . Correct this by replacing v as v-b

  15. The contraction should be in proportion to ρ2 which can be write as1/v2. ‘a’ is proportional coefficient decided by experiment (2) consider contraction among the molecules The contraction will lead to a decrease on pressure, so correct the equation as following:

  16. 2-6-3 Other Equations of State (1) Beattie-Bridgeman Equation (2) Martin-Hou Equation (3) Virial Equation

  17. The end of This Chapter Thank you

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