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. T=constant vapor solid p Triple line Solid+Vapor T Critical point1” 2” 3” 4” 5” c c 1’ 2’ 3’ 4’ 5’ 5 5” 1” 2” 3” 4” 5’ 1’ 2’ 3’ 4’ 1 2 3 4 1 2 3 4 5
vapor
Liquid +Vapor
Critical point
Liquid
Liquid +solid
Solid+Vapor
solid p T
Triple line

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

7. Extract on freezing 2-3-2 p-T diagram Melting line Expand on freezing
Critical point
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.
t ℃
P, MPa v’ v” h’ h” s’ s”
100
0.1013
1.6738
419.06
2676.3
1.3069
7.3564
200
1.5551
352.4
2791.4
2.3307
6.4289
Enthalpy ---- the combination property:
H=U+PV
Or, per unit mass h=u+Pv

9. 2-4-2 Saturated Mixture
One property 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
T ℃
P=0.1 MPa
v, m3/kg
h, kJ/kg
s, kJ/kg.K
100
1.6958
2676.2
7.3628
150
1.9364
2776.4
7.5438

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
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 as 1/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