This document provides an overview of the ME2320 Thermodynamics I course for Summer I 2016, including the instructor details, syllabus, homework format, and chapter outlines. The first chapter introduces fundamental thermodynamics concepts like systems, properties, processes, the laws of thermodynamics, and temperature and pressure units and scales. It emphasizes developing problem-solving skills through a systematic 7-step technique.

1. ME2320 Thermodynamics I
Summer I 2016
Instructor: Dr. William W. Liou

2. Syllabus
http://homepages.wmich.edu/~liou/wp_course.htm

3. 3
Homework Solutions Format

4. How to get, and stay, ahead in this class?
 Preview
 Book to Class
 Review
 Homework
Will it work if I “Preview”, but not “Book to Class” ?
Well, yes, maybe, but…

5. Chapter 1
INTRODUCTION AND
BASIC CONCEPTS

6. Objectives
6
• Identify the unique thermodynamics vocabulary.
• Review the metric SI and the English unit systems.
• Explain the basic concepts of thermodynamics such
as system, state, state postulate, equilibrium,
process, and cycle.
• Review temperature, temperature scales, pressure,
and absolute and gage pressure.
• Introduce an intuitive systematic problem-solving
technique and the format of homework solution.

7. Application Areas of Thermodynamics
7

8. 1-1 THERMODYNAMICS AND ENERGY
• Thermodynamics: The science of
energy.
• Energy: The ability to cause changes.
• thermodynamics stems from therme
(heat) and dynamis (power).
• Conservation of energy principle:
During an interaction, energy can change
from one form to another (transform) but
the total amount of energy remains
constant.
 Energy cannot be created or destroyed.
• The first law of thermodynamics: An
expression of the conservation of energy
principle.
 The first law asserts that energy is a
thermodynamic property.
Energy cannot be created
or destroyed; it can only
change forms (the first law).
8

9. • The second law of thermodynamics:
 It asserts that energy has quantity as well as
quality.
 Actual processes occur in the direction of
decreasing quality of energy.
Heat flows in the direction of
decreasing temperature.
• Classical thermodynamics: A macroscopic approach to the study of
thermodynamics that does not require a knowledge of the behavior of individual
particles (continuum). - EASY
• Statistical thermodynamics: A microscopic approach, based on the
average behavior of large groups of individual particles. – NOT EASY!
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10. 1-2 IMPORTANCE OF DIMENSIONS AND UNITS
10
• Any physical quantity can be characterized by dimensions.
• Primary or fundamental dimensions
Basic dimensions, such as
mass m,
length L,
time t,
temperature T
• secondary or derived dimensions
such as
velocity V,
energy E,
volume V
are expressed in terms of the primary dimensions.
• The magnitudes assigned to the dimensions are called units.

11. •
11

12. Some SI and English Units
Force
12

13. Some SI and English Units
13
Time Rate of Energy (such as Power)
Work = Force  Distance
1 joule (J) = 1 N∙m
1 calorie (cal) = 4.1868 J
1 Btu = 1.0551 kJ
Energy (such as Work)
Power = Energy/Time
1 watt (W) = 1 J/s
1 horsepower (hp) = 746 W

14. Unity Conversion Ratios
Unity conversion ratios are identically equal to 1 and are unitless, and thus
such ratios (or their inverses) can be inserted conveniently into any
calculation to properly convert units.
14
Dimensional homogeneity
All equations must be dimensionally homogeneous.
• Every term in an equation must have the same unit.
LAST page !

15. 15
1-3 SYSTEMS AND CONTROL VOLUMES
• System: A quantity of matter or a region in space
chosen for study.
• Surroundings: The region outside the system
• Boundary (------): The real or imaginary surface that
separates the system from its surroundings.
 fixed or
 movable.
• Systems may be considered to be
 closed or
 open.
Closed System (control mass):
 Fixed amount of mass
 No mass can cross its boundary
 No mass + No energy = isolated
system.
piston-cylinder device

16. Open System (control volume):
 Encloses a device that involves mass flow
o such as compressor, turbine, or nozzle.
 Both mass and energy can cross the boundary of a control volume.
 Control surface (-----): The boundaries of a control volume. It can be
real or imaginary.
16

17. 1-4 PROPERTIES OF A SYSTEM
• Property: Any characteristic of a system, such as
 pressure P, temperature T, volume V, and mass m, etc.
 Properties are considered to be either intensive or extensive.
 Intensive properties: Values independent of the
mass of a system,
o temperature, pressure, and density, etc
 Extensive properties: Values depend on the size
or extent of the system.
o mass and volume
 Specific properties: Extensive properties per unit
mass.
17

18. 1-5 DENSITY AND SPECIFIC GRAVITY
Specific gravity (SG): The ratio of the density of a
substance to the density of water at 4°C.
Density
Specific weight: The weight of a unit volume
of a substance.
Specific volume
18

19. 1-6 STATE AND EQUILIBRIUM
• State: Condition of a system
 Thermodynamics deals with equilibrium states.
• Equilibrium: A state of balance with no unbalanced
potentials (or driving forces) within the system.
 Thermal equilibrium: temperature is the same throughout
the entire system.
 Mechanical equilibrium: no change in pressure at any
point of the system with time.
 Phase equilibrium: If a system involves multiple phases
and when the mass of each phase reaches an equilibrium
level and stays there.
 Chemical equilibrium: chemical composition of a system
does not change with time, that is, no chemical reactions
occur.
A closed system reaching
thermal equilibrium.
19

20. The State Postulate
• The state of a simple compressible system is completely
specified by two independent, intensive properties.
 Simple compressible system: If a system involves no electrical,
magnetic, gravitational, motion, and surface tension effects.
20

21. 1-7 PROCESSES AND CYCLES
Quasistatic or quasi-equilibrium process:
A process proceeds in such a manner that the system remains infinitesimally
close to an equilibrium state at all times.
Process: Any change that a system undergoes from one equilibrium state to
another.
Path: The series of states through which a system passes during a process.
• A process : initial state, final states, as well as the path it follows, and the interactions with the
surroundings.
Process Diagram
21

22. The P-V diagram of a compression
process.
• Some common properties that are used as coordinates are temperature T,
pressure P, and volume V (or specific volume v).
• Prefix iso- designates a process for
which a particular property remains
constant
 Isothermal process: A process during
which the temperature T remains constant.
 Isobaric process: … pressure P….
 Isochoric (or isometric) process: …
specific volume v….
• Cycle: A process during which the
initial and final states are identical.
22

23. The Steady-Flow Process
fluid
properties
within
the
control
volume
may
change
with
position
but
not
with
time.
• steady implies no change with time.
• Steady-flow process: A process during
which a fluid flows through a control
volume steadily.
• A large number of engineering devices
operate for long periods of time under the
same conditions, and they are classified
as steady-flow devices.
 turbines,
 pumps,
 boilers,
 condensers, and
 heat exchangers
 power plants
 refrigeration systems.
mass and energy contents of a
control volume remain constant.
23

24. 24
1-8 TEMPERATURE AND THE ZEROTH LAW
OF THERMODYNAMICS
• The zeroth law of thermodynamics: If two bodies are in thermal
equilibrium with a third body, they are also in thermal equilibrium with
each other.
• By replacing the third body with a thermometer, the zeroth law can
be restated as two bodies are in thermal equilibrium if both have the
same temperature, even if they are not in contact.

25. 25
Temperature Scales
A constant-volume gas thermometer would read
-273.15°C, or 0 K, at absolute zero pressure.
• All temperature scales are based on some easily reproducible states
such as the freezing and boiling points of water: the ice point and the
steam point.
• Ice point: A mixture of ice and water that is in equilibrium with air
saturated with vapor at 1 atm pressure (0°C or 32°F).
• Steam point: A mixture of liquid water and water vapor (with no air) in
equilibrium at 1 atm pressure (100°C or 212°F).
• Celsius scale: in SI unit system
• Fahrenheit scale: in English unit system
• Thermodynamic temperature scale: A temperature scale that is independent of
the properties of any substance.
 Kelvin scale (SI)
 Rankine scale (E)

26. 26

27. 27
1-9 PRESSURE
Some basic pressure gages.
Pressure: A normal force exerted by a fluid per unit area

28. • Absolute pressure: The actual pressure (relative to absolute
vacuum)
• Gage pressure: The difference between the absolute pressure and
the local atmospheric pressure.
 Most pressure-measuring devices are calibrated to read zero in the atmosphere,
and so they indicate gage pressure.
• Vacuum pressures: Pressures below atmospheric pressure.
28

29. THE BAROMETER AND ATMOSPHERIC PRESSURE
• Atmospheric pressure is measured by a device called a barometer; thus, the
atmospheric pressure is often referred to as the barometric pressure.
• standard atmosphere: Pressure produced by a column of mercury 760 mm (= h)
in height at 0°C (Hg = 13,595 kg/m3) under standard gravitational acceleration
(g = 9.807 m/s2).
Barometer
29

30. PROBLEM-SOLVING TECHNIQUE
30
• Step 1: Problem Statement
• Step 2: Schematic
• Step 3: Assumptions and Approximations
• Step 4: Physical Laws
• Step 5: Properties
• Step 6: Calculations
• Step 7: Reasoning, Verification, and Discussion