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Thermodynamics Lecture
Series
Introduction to
Thermodynamics – Learning
the Lingo
Applied Sciences Education Research Group
(ASERG)
Faculty of Applied Sciences
Universiti Teknologi MARA
email: [email protected]
http://www5.uitm.edu.my/faculties/fsg/drjj1.html
Quotes
“Learning is not a spectator sport. Students
do not learn much just sitting in classes
listening to teachers, memorizing
prepackaged assignments, and spitting out
answers. They must talk about what they
are learning, write reflectively about it,
relate it to past experiences, and apply it to
their daily lives. They must make what they
learn part of themselves.”
-Source:"Implementing the Seven Principles:
Technology as Lever" by Arthur W.
Chickering and Stephen C. Ehrmann
Introduction
Objectives:
1. State the meaning of terminologies used in
thermodynamics
2. State and identify origins and transformations
of the many different forms of energy
3. State and discuss the characteristics and
description of changes of and to a system
4. State and discuss the zeroth law of thermo.
CHAPTER
1
Basic Concepts
of Thermodynamics –
The science of Energy
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FIGURE 1–5
Some application areas of
thermodynamics
.
1-1
Steam Power Plant
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FIGURE 1–13
System,
surroundings, and
boundary.
1-3
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FIGURE 1–14
Mass cannot cross
the boundaries of a
closed system, but
energy can.
1-4
Systems
Qin
Qout
Energy cross in and out
NO VOLUME CHANGE
Vinitial = Vfinal
V =constant
A rigid tank
Win
Wout
Systems
No mass or dynamic
energy transfer
An isolated system
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FIGURE 1–17
A control volume may involve fixed,
moving, real, and imaginary
boundaries.
1-5
Open system devices
Heat Exchanger
Throttle
Properties:
•Temperature
•Pressure
•Volume
•Internal energy
•Entropy
Properties
System
The system can be either open or
closed. The concept of a property
still applies.
First Law of Thermodynamics
Movable boundary
position gone up
System
System
expands
System
A change has taken
place.
Classes of properties
• Extensive
• Intensive
– MASS, m
– VOLUME, V
– ENERGY, E
–
–
–
–
ADDITIVE OVER
THE SYSTEM.
NOT ADDITIVE OVER
THE SYSTEM.
TEMPERATURE, T
PRESSURE, P
DENSITY
Specific properties
States
• State
– A set of properties describing the
condition of a system
• A change in any property, changes the
state of that system
States
• Equilibrium
– A state of balance
– Thermal – temperature same at all points
of system
– Mechanical – pressure same at all points
of system at all time
– Phase – mass of each phase about the
same
– Chemical – chemical reaction stop
States
• State postulate
– Must have 2 independent intensive
properties to specify a state:
• Pressure specific internal energy
• Pressure & specific volume
• Temperature & specific enthalpy
Processes and cycles
First Law of Thermodynamics
Properties will change
indicating change of
state
Mass in
Qin
Qout
System
E1, P1, T1, V1
To
E2, P2, T2, V2
Win
Wout
Mass
out
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FIGURE 1–25
A process
between states
1 and 2 and
the process
path.
1-6
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FIGURE 1–28
The P-V diagram of a
compression process.
1-7
p
Thermodynamic process
State 1
State 2
V
T
Example: Heating water
T1
T1+dT
T1+2dT
T2
….
T1
T1+dT
T1+2dT
T2
Heat supplied by electricity or combustion.
System analysis of the slow heating process:
System Boundary
Neglect vapor loss
Twater
Assume no heat
losses from sides
and bottom.
Theater
Energy in via electricity
or gas combustion
System analysis for the water under equilibrium processes:
Twater
Twater
Theater
Theater
Energy In
Heating via an equilibrium process
Energy Out
Reversed process of slow cooling,
which is reversible for the water
p
Processes & Equilibrium States
S1
Process Path
V
S2
T
What is the
state of the
system along
the process
path?
Thermodynamic process
Process 1
p
State 1
State 2
Process 2
T
V
Thermodynamic cycles
P1
State 1
State 2
Process Path I
Process Path II
P2
Example: A steam power cycle.
Combustion
Products
Steam
Turbine
Fuel
Air
Pump
Mechanical Energy
to Generator
Heat
Exchanger
Cooling Water
System Boundary
for Thermodynamic
Analysis
Types of Energy
Types of Energy
• Dynamic
– Heat, Q
– Work, W
– Energy of moving
mass, Emass
Crosses in and out of
system’s boundary
• System
– Internal, U
– Kinetic, KE
– Potential, PE
Changes occuring
within system
Types of Energy
• Internal, U
– Sensible,
• Relates to temperature change
– Latent
• Relates to phase change
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FIGURE 1–32
The various forms of
microscopic
energies that make
up sensible energy.
1-8
Types of Energy
• Kinetic
– Changes with square of velocity
• KE = (mv2)/2, kJ; ke = v2/2, kJ/kg
– If velocity doubles,
• KE = (m(2v)2)/2 = (4mv2)/2, kJ
– If decrease by ½, then
• KE = (m(v/2)2)/2 = (mv2)/8, kJ
Types of Energy
• Potential
– Changes with vertical position,
• PE = mg(yf-yi) = mgh, kJ; pe = gh, kJ/kg
– If position above reference point doubles,
• PE = mg(2h), kJ; pe = g2h, kJ/kg
– If decrease by ½, then
• PE = mgh/2, kJ; pe = gh/2, kJ/kg
APPLICATION OF THE
EQUILIBRIUM PRINCIPLE
Zeroth Law of Thermodynamics
Heat, and Temperature
Temperature & heat...
Heat & temperature
Large body
at constant
temperature
T1
Large body
at constant
temperature
T2<T1
Our sense of the direction of
heat flow - from high to low temperature.
Temperature and heat are related.
T1
T1
T2
For metals, high
heat flow - diathermal
materials.
T2
For nonmetals, low
heat flow - insulating.
Caloric definition of temperature
Isolating
boundaries
T2
T1
T1  T2
Bring systems into thermal contact and surround
with an isolating -- adiabatic -- boundary.
T1
T2
Initial configuration of the closed, combined
systems with a diathermal wall between the two.
T1
T2
Heat is observed to flow from the subsystem at the
higher temperature to that with the lower temperature.
T1,final
T2,final
The final observed state of the total system is
that when the temperatures are equal. Heat
flow from subsystem 1 to subsystem 2 decreases
in time.
Zeroth Law of Thermodynamics...
Thermal equilibrium
T1
T2
Initial State: T1  T2
T1,final
T2,final
Final State: T1  T2
Demonstration of the Zeroth Law
A
B
Adiabatic
Diathermal
D
D
C
Two subsystems in equilibrium with a third subsystem
The Zeroth Law
Two systems in thermal
equilibrium with a third
system are in thermal
equilibrium with each other.
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FIGURE 1–41
The greenhouse effect on
earth.
1-11
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FIGURE 1–45
P versus T plots of the
experimental data
obtained from a
constant-volume gas
thermometer using
four different gases at
different (but low)
pressures.
1-12
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FIGURE 1–47
Comparison of
temperature scales.
1-13
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FIGURE 1–51
Absolute, gage, and
vacuum pressures.
1-14
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FIGURE 1–55
The pressure is the same at all
points on a horizontal plane in a
given fluid regardless of
geometry, provided that the
points are interconnected by the
same fluid.
1-15
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FIGURE 1–57
The basic manometer.
1-16
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FIGURE 1–61
Schematic for Example 1–
8.
1-17
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FIGURE 1–63
The basic barometer.
1-18
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FIGURE 1–75
Some arrangements that
supply a room the same
amount of energy as a
300-W electric resistance
heater.
1-19
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FIGURE 1–39
Ground-level ozone,
which is the primary
component of smog,
forms when HC and
NOx react in the
presence of sunlight
in hot calm days.
1-9
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FIGURE 1–40
Sulfuric acid and
nitric acid are formed
when sulfur oxides
and nitric oxides
react with water
vapor and other
chemicals high in the
atmosphere in the
presence of sunlight.
1-10
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FIGURE 1–7
The definition of the force units.
1-2