Chapter 3: Evaluating Properties. Property Relations in Engineering Thermodynamics. Lava flowing into the Pacific Ocean in Hawaii. Photo courtesy of Mike Benson. The State Principle.
Property Relations in Engineering Thermodynamics
Lava flowing into the Pacific Ocean in Hawaii. Photo courtesy of Mike Benson.
Two independent, intensive, thermodynamic properties are required to fix the state of a simple compressible system.
P and v
T and u
x and h
Intensive thermodynamic properties:
Note the location of the following:
- Single phase regions
- Two phase regions
- Saturation states
- Triple line
- Critical Point
Diagram courtesy of Jerry M. Seitzman, 2001.
Constant Pressure phase change of water:
L – Value in table at lower end
H – Value in table at upper end
None – value of interest
LET b = ANY INTENSIVE PROPERTY
Enthalpy is a property constructed due to the frequent occurrence of the above combination of properties.
Using ‘Incompressible Substance Model’Approximations for liquids and solids
The Ideal Gas Model:
When specific heats are assumed constant Table A-20(E):
Tables A-22(E) and A-23 (E)
For a closed system:
Expansion/Compression (Moving Boundary) Work (Ideal Gas OR liquid):
Ideal Gases ONLY: