1. 공정 열역학 Chapter 6. Thermodynamic Properties of Fluids
고려대학교 화공생명공학과
강정원

2. Introduction
Numerical values of properties are most important for heat and work calculations
Enthalpy, Internal Energy, Entropy, …..
Measurable Quantities : PVT data and heat capacity
Properties relations are important to calculate one properties from the other.
Generalized correlations are used when experimental values are not available.

3. 6.1 Properties Relations for Homogeneous Phases
From the 1st law and 2nd law of Thermodynamics,
Although this eqn. has been derived for the special case of reversible process, it only contain state properties of the system.
Can be applied to any process
from one equilibrium state to another
The only requirements are that the system be closed and that the change occur between equilibrium states.

4. 6.1 Properties Relations for Homogeneous Phases
When the equations are written in molar units;

5. 6.1 Properties Relations for Homogeneous Phases
Fundamental Properties Relations
These fundamental properties relations are general equation for homogeneous fluid of constant composition

6. 6.1 Properties Relations for Homogeneous Phases
Exact Differential Equation
If a function F is a property (not depending on the path)
The total differentiation

7. 6.1 Properties Relations for Homogeneous Phases
Exact Differential Equation
Condition for exactness

8. 6.1 Properties Relations for Homogeneous Phases
Maxwell’s Relation

9. QUIZ
Obtain fundamental property relationship and Maxell’s relation. (Without the help of the textbook)

10. Enthalpy as a Function of T and P
T and P : easily measurable

11. Entropy as a Function of T and P
T and P : easily measurable

12. Internal Energy as a Function of T and P
T and P : easily measurable

13. QUIZ [Hint] Obtain Expressions for H, S and U as a function of T and P
Obtain Expressions for H, S and U as a function of T and P for ideal gas (Apply ideal gas law for above problem)
[Hint]

14. Ideal-Gas State

15. Alternative Form for Liquid
For liquids,

16. Internal Energy as a Function of T and V
Sometimes T and V are more useful than T and P
Equation of States are expressed as P = F(V,T)

17. Entropy as a Function of T and V
Sometimes T and V are more useful than T and P
Equation of States are expressed as P = F(V,T)

18. QUIZ
Express Enthalpy as a Function of T and V
Open Book

19. Gibbs Free Energy as a Generating Function
G = G(T,P)
Canonical Variable
Conforms to a general rule that is both simple and clear

20. Gibbs Free Energy as a Generating Function
Fundamental Properties Relationship
When Gibbs energy given as a function of T and P serves as a generating function for other thermodynamic properties, and implicitly represents complete property information

21. 6.2 Residual Properties
No experimental method to measure G as a function of T and P
Residual Property
Departure function from ideal gas value
M is any molar property : V, U, H, S, A or G

22. 6.2 Residual Properties Advantages of using Residual Properties
Generating Function  Normally function of T,P
Ideal Gas Property
P = RT/V
Cp = Cp (T) = dH/dT , Cv = Cv(T)=dU/dT, Function of T only
If we can use other method to evaluate residual properties, we can calculate all the other properties
Equation of State
Generalized Correlation