ENGR%202213%20Thermodynamics

1
ENGR 2213 Thermodynamics

• F. C. Lai
• School of Aerospace and Mechanical
• Engineering
• University of Oklahoma

2
Syllabus
Instructor Dr. F. C. Lai (FH 218A) Phone
325-1748, Fax [phone], Email
flai_at_ou.edu Office Hours 1400-1500 MTWR or by
appointment
Textbook Thermodynamics An Engineering Approach
by Y. A. Çengel and M. A. Boles, 4th edition,
McGraw-Hill, 2002.
3
Course Outline
Introduction (1) ? Basic Concepts ? Properties
First Law (2-6) ? Energy Analysis for Closed
System ? Energy Analysis for Control Volumes
Second Law (7-12) ? Entropy ? Exergy
(Availability)
4
Course Outline
Power Systems (12-16) ? Vapor Power Systems ?
Gas Power Systems
5
Grade
? Homework (8-10) 25 ? Quizzes
(3) 45 ? Final Exam 30 Final
grade (in absolute scale) 85 A 75-84
B 65-74 C 55-64 D 55- F
6
Introduction
Thermo- dynamics
heat
force
? Energy ? Engineers ? Properties of
Matter ? Scientists
7
History of Development
1700 Building a steam engine (T. Savery and
T. Newcomen) 1849 First use of the term
Thermodynamics (Lord Kelvin) 1859 First
textbook of Thermodynamics (W.
Rankine) gt1900 Become a mature science
8
Approaches
Macroscopic Approach (Classical Thermodynamics)
- is concerned with the overall behavior of a
system - no model of the structure of matter at
the molecular, atomic, and subatomic level is
directly use
Microscopic Approach (Statistical Thermodynamics)
- is concerned directly with the structure of
matter - characterize, by statistical means, the
average behavior of the particles making up a
system of interest and relate this information
to the observed macroscopic behavior of the
system
9
Definitions
System the subject of the analysis
Surroundings everything external to
the system
Boundary the surface that separates the
system from its surroundings
surroundings
system
10
Definitions
System the subject of the analysis
Surroundings everything external to
the system
Boundary the surface that separates the
system from its surroundings
boundary
11
Systems
Closed Systems
- A fixed quantity of matter - There can be no
transfer of mass across its boundary - Energy,
in the form of heat or work, can cross the
boundary - The volume of a closed system does
not have to be fixed
Control Volumes
- A fixed volume in space through which mass may
flow - It usually enclose a device which
involves mass flow such as a compressor,
turbine, or nozzle
12
Systems
Piston and Cylinder Assembly
Water Heater
Closed System
13
Systems
Piston and Cylinder Assembly
Water Heater
Closed System
Control Volume
14
Properties
Macroscopic characteristics of a system to which
numerical values can be assigned.
Extensive Properties
Properties that their values depend on the size
or extend of a system.
Examples mass, volume
Intensive Properties
Properties that their values are independent of
the size or extend of a system.
Examples temperature, pressure
15
Properties
? Divide and Conquer ? Rule of Sum

For a quantity, if its value for a system is the
sum of its values of each partition, then it is an
extensive property.
16
Properties
? Divide and Conquer ? Rule of Sum

For a quantity, if its value for a system is the
sum of its values of each partition, then it is an
extensive property.
M M1 M2 M3 M4
Mass is an extensive property
1
2
3
4
17
Properties
? Divide and Conquer ? Rule of Sum

For a quantity, if its value for a system is the
sum of its values of each partition, then it is an
extensive property.
V V1 V2 V3 V4
Volume is an extensive property
1
2
3
4
18
Properties
? Divide and Conquer ? Rule of Sum

For a quantity, if its value for a system is the
sum of its values of each partition, then it is an
extensive property.
P P1 P2 P3 P4
Pressure is not an extensive property
1
2
3
4
19
Properties
? Divide and Conquer ? Rule of Sum

For a quantity, if its value for a system is the
sum of its values of each partition, then it is an
extensive property.
T T1 T2 T3 T4
Temperature is not an extensive property
1
2
3
4
20
Properties
Specific Properties
- Extensive properties per unit mass
- A specific property is an intensive property
Examples specific volume
density
21
Basic Concepts
State
The condition of a system as described by its
properties
Process
A transformation from one state to another
At a given state, each property has a definite
value that is Independent of how the system
arrived at that state.
22
Basic Concepts
The change in value of a property as the system
is altered from one state to another is
determined solely by the two end states and is
independent of the particular way the change of
state occurred.
A quantity is a property if, and only if, its
change in value between two states is independent
of the process.
23
Basic Concepts

Denver
OKC
Latitude Longitude Elevation Denver 39º
45 104º 52 5280 OKC 35º 24 97º
36 1285
24
Basic Concepts
Phase
A quantity of matter that is homogeneous
throughout in both chemical composition and
physical structure.
Homogeneous in physical structure means that the
Matter is all solid, all liquid, or all vapor
(gas).
A system can contain one or more phases.
For example water and vapor
2 phases
25
Basic Concepts
Phase
A quantity of matter that is homogeneous
throughout in both chemical composition and
physical structure.
Homogeneous in physical structure means that the
Matter is all solid, all liquid, or all vapor
(gas).
A system can contain one or more phases.
For example water and vapor
2 phases
water and oil
2 phases
26
Basic Concepts
Phase
A quantity of matter that is homogeneous
throughout in both chemical composition and
physical structure.
Homogeneous in physical structure means that the
Matter is all solid, all liquid, or all vapor
(gas).
A system can contain one or more phases.
For example water and vapor
2 phases
water and oil
2 phases
water and alcohol
1 phase
27
Basic Concepts
Phase
A quantity of matter that is homogeneous
throughout in both chemical composition and
physical structure.
Homogeneous in physical structure means that the
Matter is all solid, all liquid, or all vapor
(gas).
A system can contain one or more phases.
For example water and vapor
2 phases
water and oil
2 phases
water and alcohol
1 phase
oxygen and nitrogen
1 phase
28
Basic Concepts
Pure Substance
One that is uniform and invariable in chemical
composition
A pure substance can exist in more than one phase
A uniform mixture of gases can be regarded as a
pure substance provided it remains a gas and does
not react chemically
29
Equilibrium

A state of balance In an equilibrium state,
there are no unbalanced potentials (driving
forces) within the system.
Thermodynamic Equilibrium ? Thermal
Equilibrium ? Mechanical Equilibrium ? Phase
Equilibrium ? Chemical Equilibrium
30
Thermodynamic Equilibrium

Thermal Equilibrium
? The system involves no temperature
differentials
? Temperature is uniform in the system
Mechanical Equilibrium
? No change in pressure at any point in the
system
? The pressure may vary within the system with
elevation as a result of gravitational effect
31
Thermodynamic Equilibrium

Phase Equilibrium
? The mass of each phase remains the same
Chemical Equilibrium
? Chemical composition does not change with time
? No chemical reactions occur
32
Basic Concepts
Quasi-Equilibrium Process
A process that proceeds in such a manner that the
system remains infinitesimally close to an
equilibrium state at all times
A quasi-equilibrium process is an idealized
process to approximate an actual process
33
Basic Concepts
Process Path
The series of equilibrium states through which a
system passes during a process
To describe a process completely, one needs to
specify the initial and final states of the
process, as well as the path it follows
Steady State
Properties of the system does not change with time
Cycle
A sequence of processes that begins and ends at
the same state