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FE
Thermodynamics
Review
Dr. Omar Meza
Assistant Professor
Department of Mechanical Engineering
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Topics covered
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Thermodynamics Law
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1st and 2nd law
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Energy , heat and work
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Availability and reversibility
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Cycles
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Ideal gases
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Mixture of gases
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Phase change
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Heat Transfer
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Properties of:
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
enthalpy
entropy
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Tips for taking exam
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Use the reference handbook
 Know what it contains
 Know what types of problems you can use it for
 Know how to use it to solve problems
 Refer to it frequently
Work backwards when possible
 FE exam is multiple choice with single correct answer
 Plug answers into problem when it is convenient to do so
 Try to work backwards to confirm your solution as often as
possible
Progress from easiest to hardest problem
 Same number of points per problem
Calculator tips
 Check the NCEES website to confirm your model is allowed
 Avoid using it to save time!
 Many answers do not require a calculator (fractions vs.
decimals)
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Properties of Single-Component
Systems
For a simple substance,
specification of any two
intensive,
independent
properties is sufficient to
fix all the rest.
Handbook page:
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Properties of Single-Component
Systems
A substance that has a
fixed
chemical
composition throughout
is called a pure substance.
Handbook page:
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Properties of Single-Component
Systems
A substance whose properties are uniform throughout is
referred to as
A. A solid
B. An ideal substance
C. A pure substance
D. A standard substance
A substance whose properties are uniform throughout is
referred to as
A. A solid
B. An ideal substance
C. A pure substance
D. A standard substance
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Properties of Single-Component
Systems
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Properties of Single-Component
Systems
 Given: Steam at 2.0 kPa is saturated at 17.5 oC. In what
state will the steam be at 40 oC if the pressure is 2.0 kPa?
T= 40oC
Tsat= 17.5oC
 Analysis:


@ P = 2.0 kPa, Tsat = 17.5oC
Tsat < T  “superheated vapor”
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Properties of Single-Component
Systems
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Properties of Single-Component
Systems

Find the volume occupied by 20 kg of steam at 0.4 MPa,
400oC

At 0.4 MPa the Tsat=142oC approximately. It means that the
steam is in the superheated region
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Properties of Single-Component
Systems
Real gases exhibit idealgas behavior at relatively
low pressures and high
temperatures.
Handbook page:
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Properties of Single-Component
Systems
All real gases deviate somewhat from ideal gas behavior:
PV= mRT. For which of the following conditions is the
deviation the smallest?
A. High temperature and low volume
B. High temperature and low pressures
C. High pressures and low volumes
D. High pressure and low temperatures
When the volume of an ideal gas is doubled while the
temperature is halved, what happens to the pressure?
A. Pressure is doubled
Pv X(2v) 4 Xv
B. Pressure is halved
=
=
T
( T / 2)
T
C. Pressure is quartered
D. Pressure is quadrupled
P
X=
4
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Properties of Single-Component
Systems
Handbook page:
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Properties of Single-Component
Systems
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Properties of Single-Component
Systems
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First Law of Thermodynamics
Handbook page:
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First Law of Thermodynamics
(Qin - Qout ) + (Win - Wout ) = ΔU + ΔKE + ΔPE
Formal sign convention: Heat transfer to a
system and work done by a system are
positive; heat transfer from a system and work
done on a system are negative.
Wb is positive  for expansion
Wb is negative  for compression
Handbook page:
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First Law of Thermodynamics
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First Law of Thermodynamics
During a process, 30J of work are done by a closed
stationary system on its surroundings. The internal energy
of the system decreases by 40 j. What is the heat transfer?
Qin - Qout  + Win - Wout   U  KE  PE
Qnet - Wout  U
Qnet  U  Wout
Qnet  40 J  30 J  10 J
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First Law of Thermodynamics
Handbook page:
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First Law of Thermodynamics
Calculate the work done by a piston contained within a
cylinder with air if 2m3 is tripled while the temperature is
maintained at a constant T = 30oC. The initial pressure is
P1=400 kPa absolute.
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First Law of Thermodynamics
Polytropic process in a closed system
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First Law of Thermodynamics
Handbook page:
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First Law of Thermodynamics
Handbook page:
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First Law of Thermodynamics
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First Law of Thermodynamics
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First Law of Thermodynamics
Handbook page:
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First Law of Thermodynamics
Handbook page:
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First Law of Thermodynamics
Handbook page:
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First Law of Thermodynamics
A steam coil operating at steady state receives 30 kg/min of
steam with an enthalpy of 2900 kJ/kg. if the steam leaves
with an enthalpy of 1600 kJ/min, what is the rate of heat
transfer from the coil?
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First Law of Thermodynamics
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First Law of Thermodynamics
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
Handbook page:
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Basic Cycles
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Ideal Gas Mixture
Handbook page:
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Ideal Gas Mixture
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Ideal Gas Mixture
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Ideal Gas Mixture
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Psychrometrics
Handbook page:
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Psychrometrics
Mollier Diagram
Handbook page:
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Psychrometrics
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Psychrometrics
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Psychrometrics
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Psychrometrics
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Psychrometrics
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Psychrometrics
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Psychrometrics
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Psychrometrics
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Psychrometrics
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Combustion Processes
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Combustion Processes
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Combustion Processes
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Combustion Processes
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Combustion Processes
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Second Law of Thermodynamics
Handbook page:
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Second Law of Thermodynamics
Part of the heat received by a heat
engine is converted to work, while the
rest is rejected to a sink.
This is a law.
1. It is always observed in real heat engines.
2. One cannot derive it from first principles.
3. No exceptions are known.
It is not just that we haven’t looked hard
enough and that future discoveries will make
it possible to convert heat completely to work.
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Second Law of Thermodynamics
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Second Law of Thermodynamics
The efficiency of a refrigerator is
expressed in terms of the
coefficient of performance (COP).
The objective of a refrigerator is to
remove heat (QL) from the
refrigerated space.
Can the value of COPR
be greater than unity?
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Second Law of Thermodynamics
The work
supplied to a
heat pump is
used to
extract energy
from the cold
outdoors and
carry it into
the warm
indoors.
for fixed values of QL and QH
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Second Law of Thermodynamics
A)
B)
C)
D)
1500-MW
600-MW
900-MW
2100-MW
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Second Law of Thermodynamics
A)
B)
C)
D)
Yes
No
Not clear
NA
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Entropy
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Entropy
A)
B)
C)
D)
2.82 kJ/K
6.86 kJ/K
-8.10 kJ/K
8.10 kJ/K
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Preguntas? Comentarios?
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Muchas Gracias !