1. 1 Basic Concepts of Thermodynamics 1-1 Thermodynamics and Energy
Definition of Thermodynamics
Thermodynamics is defined as the science of energy.
Engineering thermodynamic deals with the principles of energy and energy conversion in engineering and the thermal properties of substances as well.
It can be divided into: Classical Thermodynamics macroscopic approach
Statistical Thermodynamics microscopic approach
Contents of Thermodynamics
The Basic Laws of Thermodynamics :
(1) The First Law of Thermodynamics:
an expression of the quantity relationship during energy change
(2) The Second Law of Thermodynamics:
an expression of the quality relationship during energy change

2. The Properties of Material
(1) Ideal Gas
(2) Vapor: Water Steam, Freon , Ammonia
(3) Mixtures: Gas mixture, Gas-vapor mixture
Practical Application
Gas Power Cycle
Vapor and Combine Power Cycle
Refrigeration

3. From Le Systeme International d’Unites
History :
French National Assembly charged the French Academy of Science
The Metric Convection Treaty was signed by 17 nations.General Conference of Weights and Measures ( CGPM ) was established
the CGPM produced the SI
Dimensions and Units
Any physical quantity can be characterized by dimension
The arbitrary magnitudes assigned to the dimensions are called Units
Primary( foundamental ) dimensions and units:
Mass m, Length L, time t, temperature, T, mol
Secondary dimensions:
velocity V, energy E , volume V
English system:
Also known as the United States Customary System(USCS)
SI: International System
From Le Systeme International d’Unites

4. Some SI and English units
Refer to our Text book
Dimensional Homogeneity
Every term in an equation must have the the same units.
* the student must keep in mind that a formula which is not dimensionally homogeneous is definitely wrong, but a dimensionally homogeneous formula is not necessarily right

5. 1-2 Thermodynamics System
1-2-1 The definition of Thermodynamics System
System : A quantity of matter or a region in space for study
The real or imaginary surface that separates the system from its surroundings is called boundary
Anything outside the boundary is called surrounding
The boundary can be real or imaginary; fixed or changeable, has no thickness and volume , and does not contain any substance.

6. 1-1-3-2 The Classification of Thermodynamics system
Closed system :
A system that only energy can cross the boundary but no mass can enter or leave ( also known as control mass )
Opened system :
A system that not only energy but also mass can cross the boundary (also known as control volume )

7. isolated system :
A system that neither energy nor mass can cross the boundary
(a special closed system)
The Universe

8. 1-3 State and Equilibrium
1-3-1 Definition: All macroscopic characteristics of a system at one time point
1-3-2 Classification:
Equilibrium state:
any part of the system have the same characteristics
any characteristics don’t change with time
Nonequilibrium state:
1-3-3.Conditions of Equilibrium
Thermal equilibrium
Mechanical equilibrium
Chemical equilibrium
Phase equilibrium

9. 1-4 Properties of System ∮dx = 0 Intensive property： 1-4-1 Definition
Any characteristic of a system is called a property
Characteristic of property
Related with States but have nothing to do with the path from one state to another
According to mathematics：
∮dx = 0
Classification of property
Intensive property：
Properties independent of the size of system, such as：
temperature, pressure, specific volume

10. Extensive property：
Properties whose values depend on the size or extent of system, such as：
volume, entropy, enthalpy

11. 1-5 The state postulate
The state of system is described by its properties,But obviously we don’t need to specify all the properties to fix a state,Then how many properties are enough to fix a state?
State postulate
The state of a simple compressible system is completely specified by two independent, intensive properties
A system is called simple compressible system in the absence of electrical, gravitational, motion, and surface tension effects.

12. 1-6 Thermodynamics Property Coordinates
Since two properties can fix a state, it’s very convenient to draw a state point on a two-dimension coordinates. p v
equilibrium state
nonequilibrium state

13. The usually used coordinates are: p-v coordinates, T-s coordinates, h-s coordinates

14. How to change under equilibrium state?
1-7 Process and Cycle
Process:
any change that a system undergoes from one equilibrium state to another
Quasi-static process:
a process proceeds in such manner that the system remains infinitesimally close to an equilibrium state at all time p v
Quasi-static process
nonequilibrium process
Initial state
final state

15. Cycle:
A path-closed process p v

16. 1-8 Forms of energy
1-8-1 Total energy
The total energy E of a system is the sum of thermal, mechanical, kinetic, potential, electric,chemical and nuclear energy.
On a unit mass basis,
1-8-2 Classification of energy
1.Macroscopic form : kinetic energy KE and potential energy PE
and
On a unit mass basis
and

17. 2.Microscopic form:
relate to the molecular structure of a system and the degree of the molecular activity. The sum of all the microscopic forms of energy is called the internal energy, denoted by U or u on a unit mass basis.
1-8-3 Expression of total energy
On a unit mass basis

18. 1-9 Pressure 1-9-1 definition
The force exerted by a fluid per unit area
Calculation:
Unit:
SI: Pa N/m2
English: psi------lbf/in2

19. 1bar=105 Pa
= 0.1 Mpa
=100 kPa
1atm=101,325 Pa
= kPa
= bar
= psi

20. The pressure calculated by formula P=F/A
Gage pressure and vacuum Pressure
Absolute pressure: the actual pressure at a given position is called the absolute pressure
manometer

21. In SI the unit also is Pa, but in English psig usually employed
Gage pressure:The pressure over atmospheric pressure while gas pressure is larger than that of atmosphere，expressed by Pg
Vacuum pressure:The pressure below atmospheric pressure while gas pressure is smaller than that of atmosphere，expressed by Pv

22. Absolute pressure? gage pressure? vacuum pressure? woooooooo!
Which one is the state property?

23. 1-10 Temperature I think it is the measure of hotness or coldness
Am I right?
1-10 Temperature
What is temperature?
The zeroth law of thermodynamics
If two bodies are in thermal equilibrium with a third body , they are also in thermal equilibrium each other .

24. 1-10-2 thermodynamics definition of temperature
It’s the property to describe if systems are in thermal equilibrium
Temperature scale
Three factors of Temperature scale ：
zero point
two states point ( easily reproducible states )
Scale

25. Formerly called the centigrade scale, in 1948 it was renamed after the Swedish astronomer A.Celsuis ( )
named after the German instrument maker G.Fahrenheit ( )
Temperature scale in history
SI: Celsius scale
English: Fahrenheit scale

26. Thermodynamics temperature scale:
SI: Kelvin scale
English: Rankine scale
Relations of scales: