2. BONUS TRACK….
• Remember that gas is a collection of particles which are moving in random
motion.
• Due to structure of the molecules, there is a molecular forces between
particles that interact with each other and creating a force field.
• However, if the distance between particles are vast enough, this forces
interaction become small and can be neglected.
• A gas in which the inter-molecular forces are neglected, is called a perfect
gas.
• This assumption is valid for wide range of temperature and pressure
Introducing the Perfect Gas
3. Universitas Nurtanio - Thermodynamic Class 2012/2013
BONUS TRACK….
Please recall ideal gas state equation:
/ n
/ M
adalah specific gas constant in
Untuk udara,
Perfect gas:
4. Universitas Nurtanio - Thermodynamic Class 2012/2013
BONUS TRACK….
Internal energy and enthalpy
Atau dalam besaran spesifik,
Enthalpy didefinisikan sebagai:
Untuk perfect gas,
Yang turunan-nya menjadi,
Dan untuk calorically perfect gas dimana
cp dan cv adalah konstan,
u & h adalah state variables dan tidak
bergantung pada proses.
5. For a perfect gas,
Divide above equation with cp, Divide above equation with cv,
And since And since
or or
BONUS TRACK…
6. Universitas Nurtanio - Thermodynamic Class 2012/2013
BONUS TRACK….
Example:
Diketahui sebuah ruangan tertutup dengan panjang 7 m, lebar 5 m, dan tinggi 3
m. Pada suatu kondisi, temperatur dan tekanan udara dalam ruangan tersebut
adalah 25 °C dan 1 atm. Hitung energi dalam dan enthalpy dari udara dalam
ruangan tersebut!
1 atm = 1.01*10e5 Pa
1 °C = 273 K
Ans: U=2.92 x 10e7 Joule
H=4.08 x 10e7 Joule
7. Universitas Nurtanio - Thermodynamic Class 2012/2013
INTRO TO 2ND
LAW
Consider this:
• Sistem: udara bertekanan tinggi dalam tabung.
• Ketika katup dibuka, maka udara akan keluar dan membuat tekanan dalam
tabung sama dengan lingkungannya. (equilibrium)
• Berdasar insting, kita bisa berkata bahwa inilah proses yang terjadi secara
spontan dan bukan sebaliknya.
8. Universitas Nurtanio - Thermodynamic Class 2012/2013
INTRO TO 2ND
LAW
Consider this:
• Namun, hukum pertama sebetulnya tidak pernah membatasi inilah proses
yang terjadi. Selama energi terkonservasi dalam proses tersebut.
• Hukum pertama membolehkan, ketika katup dibuka, udara dari lingkungan
akan masuk ke dalam tabung dan termampatkan, selama energi kekal.
• Proses ini tidak mungkin terjadi secara spontan.
9. Universitas Nurtanio - Thermodynamic Class 2012/2013
INTRO TO 2ND
LAW
Consider this:
• Dibutuhkan perangkat untuk memberitahu kita, apa proses yang terjadi secara
spontan, dan kemana arahnya.
• Hukum ke-dua.
10. INTRO TO 2ND
LAW
Universitas Nurtanio - Thermodynamic Class 2012/2013
Irreversibility of a process
Reversible process
Proses reversibel adalah proses dimana sistem dan
lingkungannya dapat dengan tepat dikembalikan ke keadaan
awalnya setelah satu proses berlangsung.
Irreversible process
Jika suatu sistem mengalami proses, maka proses tersebut dikatakan
irreversible jika tidak dapat dilakukan secara terbalik dan sistem tidak
dapat dikembalikan ke keadaan semula-nya.
11. Universitas Nurtanio - Thermodynamic Class 2012/2013
INTRO TO 2ND
LAW
Irreversibility of a process
• All actual processes are irreversible!
• We used reversible assumption to simplify an analysis, or to determine the best
(maximum) thermodynamic performance of a systems.
Entropy of the universe is always growing. And process tend to occur
in a direction that gives positive change in entropy.
12. Universitas Nurtanio - Thermodynamic Class 2012/2013
INTRO TO 2ND
LAW
Consider again our expanding gas example. Instead of permitting the air to
expand aimlessly into the lower-pressure surroundings, the stream could
be passed through a turbine and work could be developed.
Recognizing this possibility for work, we can pose two questions:
• What is the theoretical maximum value for the work that could be obtained?
• What are the factors that would preclude the realization of the maximum
value?
The second law of thermodynamics provides the means for determining the
theoretical maximum and evaluating quantitatively the factors that preclude
attaining the maximum.
Cunning thought to power cycle
13. Universitas Nurtanio - Thermodynamic Class 2012/2013
THE 2ND
LAW STATEMENT
Clausius and Kelvin-Planck
Statement
“ Adalah tidak mungkin suatu sistem
beroperasi dalam siklus thermodinamik dan
hanya secara spontan mentransfer energi
dalam bentuk panas dari resoir bersuhu
rendah ke resevoir bersuhu lebih tinggi”
By Clausius:
Untuk dapat memindahkan energi dari temperatur rendah ke temperatur tinggi,
dibutuhkan usaha yang ditambahkan ke dalam sistem. e.g.: mesin pendingin
14. Universitas Nurtanio - Thermodynamic Class 2012/2013
THE 2ND
LAW STATEMENT
Clausius and Kelvin-Planck
Statement
By Kelvin-Planck:
“Adalah tidak mungkin suatu sistem dapat
beroperasi dalam siklus thermodinamik
dan hanya menghasilkan energi dalam
bentuk kerja, jika menerima energi dalam
bentuk kalor dari satu reservoir termal.”
15. Universitas Nurtanio - Thermodynamic Class 2012/2013
THE 2ND
LAW STATEMENT
Clausius and Kelvin-Planck
Statement
• A constraint is imposed by the first law on the net
work and heat transfer between the system and its
surroundings. According to the cycle energy
balance,
In words, the net work done by the system
undergoing a cycle equals the net heat transfer to
the system. Although the cycle energy balance
allows the net work Wcycle to be positive or
negative.
16. Universitas Nurtanio - Thermodynamic Class 2012/2013
THE 2ND
LAW STATEMENT
Clausius and Kelvin-Planck
Statement
• According to the Kelvin–Planck statement, a
system undergoing a cycle while communicating
thermally with a single reservoir cannot deliver a
net amount of work to its surroundings. That is, the
net work of the cycle cannot be positive. However,
the Kelvin–Planck statement does not rule out the
possibility that there is a net work transfer of
energy to the system during the cycle or that the
net work is zero.
17. THE 2ND
LAW IMPLICATION
Universitas Nurtanio - Thermodynamic Class 2012/2013
TO POWER CYCLES
• If the value of QC were zero, thermal
efficiency of such a cycle would have a value of
unity (100%).
• This method of operation would violate the
Kelvin–Planck statement and thus is not
allowed.
• Only a portion of the heat transfer QH can be
obtained as work, and the remainder, QC, must
be discharged by heat transfer to the cold
reservoir
18. Universitas Nurtanio - Thermodynamic Class 2012/2013
THE 2ND
LAW IMPLICATION
The coefficient of performance for a power
cycle is
TO POWER CYCLES
19. Universitas Nurtanio - Thermodynamic Class 2012/2013
THE 2ND
LAW IMPLICATION
TO REFRIGERATION & HEAT
PUMP CYCLES
• As the net work input to the cycle Wcycle
tends to zero, the coefficients of performance
approach infinity.
• This method of operation would violate the
Clausius statement and thus is not allowed.
• Coefficients of performance must invariably
be finite in value.
20. Universitas Nurtanio - Thermodynamic Class 2012/2013
THE 2ND
LAW IMPLICATION
The coefficient of performance for a heat
pump cycle is
The coefficient of performance For a
refrigeration cycle is
TO REFRIGERATION & HEAT
PUMP CYCLES
21. Universitas Nurtanio - Thermodynamic Class 2012/2013
THE 2ND
LAW IMPLICATION
By steadily circulating a refrigerant at low
temperature through passages in the walls of the
freezer compartment, a refrigerator maintains the
freezer compartment at -5°C when the air
surrounding the refrigerator is at 22°C. The rate of
heat transfer from the freezer compartment to the
refrigerant is 8000 kJ/h and the power input required
to operate the refrigerator is 3200 kJ/h. Determine
the coefficient of performance of the refrigerator and
compare with the coefficient of performance of a
reversible refrigeration cycle operating between
reservoirs at the same two temperature!
EXAMPLE:
22. Universitas Nurtanio - Thermodynamic Class 2012/2013
THE 2ND
LAW IMPLICATION
EXAMPLE:
Known:
Tc = -5 °C =268 K
Th = 22 °C = 295 K
= 8000 kJ/h
= 3200 kJ/h
c
Q
cycle
W
s
Joule
h
s
h
kJ
c
Q /
2222
/
3600
/
8000
s
Joule
h
s
h
kJ
c
W /
888
/
3600
/
3200
93
.
9
27
268
268
295
268
50
.
2
888
2222
23. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENTROPY
Entropi (S) : adalah ukuran ke-
tidakberatur-an suatu sistem dalam
skala mikroskopis.
Entropi merupakan variabel keadaan
(state variable) yang dapat digunakan
untuk membantu memastikan arah dari
suatu proses.
There exists for every system in
equilibrium a property called entropy,
which is a thermodynamic property of a
system
24. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENTROPY
• Mathematically, change of entropy is defined as:
Where “s” is the entropy of the system, “qrev“ is incremental amount of heat being
added to the system in reversible process, and “T” is absolute temperature of the
system. The equation defines change of entropy in term of reversible addition of
heat.
• for irreversible/actual process, change of entropy is:
25. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENTROPY
dsirrev is entropy generated due to irreversible, dissipative process. This
dissipative process always increase entropy of the system.
• In above statement, the equal sign applied when process is reversible, giving
out our first equation.
• If we combine the last two
equations, we would have
• And further assuming if the process is adiabatic
where
For reversible process, ds = 0
For irreversible process, ds > 0
• Common unit for
entropy is Joule per
degree Kelvin or J/K
26. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENTROPY
Implication of this statement is that nature, always looking for a process in which
resulted in net increase of entropy, or that entropy change is positive.
27. Universitas Nurtanio - Thermodynamic Class 2012/2013
CARNOT CYCLE
Siklus Carnot merupakan contoh yang bagus tentang siklus daya reversibel yang
beroperasi di antara dua reservoir termal.
Karena beroperasi secara reversible, maka siklus ini mampu menghasilkan
effisiensi maksimum
28. Universitas Nurtanio - Thermodynamic Class 2012/2013
CARNOT CYCLE
Siklus Carnot terdiri atas 4 proses, yaitu 2 proses adiabatik dan 2 proses
isotermik secara bergantian.
Ada empat komponen dalam mesin karnot, yaitu:
a) boiler,
b) turbine,
c) condenser, and
d) pump
29. Universitas Nurtanio - Thermodynamic Class 2012/2013
CARNOT CYCLE
• As the water flows through the boiler, a
change of phase from liquid to vapor at
constant temperature TH occurs as a result of
heat received (Qin) from the hot reservoir.
Since temperature remains constant, pressure
also remains constant during the phase
change.
30. Universitas Nurtanio - Thermodynamic Class 2012/2013
CARNOT CYCLE
• The steam exiting the boiler expands
adiabatically through the turbine and work is
developed (Wout). In this process the
temperature decreases to the temperature of
the cold reservoir, TC, and there is an
accompanying decrease in pressure.
31. Universitas Nurtanio - Thermodynamic Class 2012/2013
CARNOT CYCLE
• As the steam passes through the condenser, a
heat transfer to the cold reservoir (Qout) occurs
and the vapor condenses into fluid at constant
temperature TC. Since temperature remains
constant, pressure also remains constant as
the water passes through the condenser.
32. Universitas Nurtanio - Thermodynamic Class 2012/2013
CARNOT CYCLE
• The fluid then compressed adiabatically by a
pump and work is done to the fluid (Win)
during this process. The temperature is
changing from TC to TH and there is also
change in pressure.
33. Universitas Nurtanio - Thermodynamic Class 2012/2013
CARNOT CYCLE
• If a Carnot power cycle is operated in the
opposite direction, the magnitudes of all energy
transfers remain the same but the energy
transfers are oppositely directed.
• Such a cycle may be regarded as refrigeration
or heat pump cycle
34. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
ENGINE
CYCLES
Otto
Diesel
Brayton
Rankine
35. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
Outlined view of how steam power plant
(PLTU, in Indonesian) operates.
36. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
The “magic” of the
plant were in particular
section denoted with
the later “A”.
But what happened
here?
37. ENGINE CYCLES
Universitas Nurtanio - Thermodynamic Class 2012/2013
Cycle with 2 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
• Vapor from the boiler (at state 1), having an elevated
temperature and pressure, expands through the turbine to produce
work and then is discharged to the condenser (at state 2) with
relatively low pressure.
• The energy balance for turbine section, assuming a) no heat
transfer to the surrounding, and b) system is stationary is reduced
to give the rate at which work is developed per unit of mass of
steam passing through the turbine
38. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
• In the condenser there is heat transfer from the vapor (at state 2)
to cooling water flowing in a separate stream. The vapor condenses
(at state 3) while the temperature of the coolant increases.
• The energy balance for condenser section assuming steady state,
gives the rate at which energy is transferred by heat from the
working fluid to the coolant per unit mass of working fluid passing
through the condenser.
39. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Cycle with 2 path Cycle with 4 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
• The liquid condensate leaving the condenser (at state 3) is
pumped from the condenser into the higher pressure boiler (at
state 4). By pumping mechanism, work is added to the working
fluid.
• The energy balance for pump section, assuming a) no heat
transfer to the surrounding, and b) system is stationary is reduced
to give the rate of power input per unit of mass fluid passing
through the pump.
40. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
• The working fluid completes a cycle as the liquid leaving the
pump (at state 4), called the boiler feedwater, is heated to
saturation and evaporated in the boiler (at state 1).
• The energy balance for boiler section, gives the rate of heat
transfer from the energy source into the working fluid per unit
mass passing through the boiler
41. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Cycle with 2 path Cycle with 4 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
• The thermal efficiency defined as how much the energy inputted
to the working fluid passing through the boiler is converted to the
net work output.
42. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Cycle with 2 path Cycle with 4 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
Siklus Otto (motor bakar), paling banyak digunakan
dalam kehidupan manusia. Mobil dan sepeda motor
berbahan bakar bensin (Petrol Fuel) adalah contoh
penerapan dari sebuah siklus Otto.
Terdiri dari 2 proses isentropik dan 2 proses
isokhorik :
1-2 : Kompresi isentropik
2-3 : Pembakaran isokhorik
3-4 : Ekspansi isentropik
4-1 : Langkah buang isokhorik
43. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
compression ratio r is
defined
as the volume at bottom dead
center divided by the volume
at top dead center.
44. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Cycle with 2 path Cycle with 4 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
• Proses 1–2 adalah kompresi isentropik udara, ketika
piston bergerak dari bottom dead center menuju top dead
center.
45. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Cycle with 2 path Cycle with 4 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
• Process 2–3 is a constant-volume heat transfer to the air
from an external source while the piston is at top dead
center. (combustion)
46. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Cycle with 2 path Cycle with 4 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
• Process 3– 4 is an isentropic expansion (power stroke).
47. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Cycle with 2 path Cycle with 4 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
• Process 4–1 is constant-volume heat rejection from the
air while the piston is at bottom dead center.
48. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
K=1.4
49. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
Siklus diesel untuk mesin diesel terdiri dari
2 proses isentropik, 1 proses isobarik dan 1
proses isokhorik
1-2 : Kompresi isentropik
2-3 : Pembakaran isobarik
3-4 : Ekspansi isentropik
4-1 : Pembuangan isokhorik
50. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
Process 1 - 2 is the same as in the Otto cycle: an isentropic
compression.
51. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Cycle with 2 path Cycle with 4 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
Process 2 - 3 is combustion that makes up the first part of the
power stroke. Here, heat is added to the air at constant pressure
52. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Cycle with 2 path Cycle with 4 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
Process 3 – 4 is isentropic expansion and made the second part of
the power stroke.
53. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Cycle with 2 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
Process 4 – 1 is constant-volume heat rejection from the air
while the piston is at bottom dead center.
54. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Cycle with 2 path Cycle with 4 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
55. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Cycle with 2 path Cycle with 4 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
Brayton cycle
56. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Cycle with 2 path Cycle with 4 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
Proses yang terjadi pada suatu sistem turbin gas yang ideal:
1. Pemampatan (compression) , udara di mampatkan ,
proses isentropik
2. Pembakaran (combustion) , campuran fuel dan udara ,
proses isobarik
3. Pemuaian (expansion) gas hasil pembakaran ke nozel &
turbine, proses isentropik
4. Pembuangan gas (exhaust) gas hasil pembakaran , proses
isobarik
57. Universitas Nurtanio - Thermodynamic Class 2012/2013
ENGINE CYCLES
Cycle with 2 path Cycle with 4 path
Diesel cycle
Otto cycle
Rankine cycle
Brayton cycle
Editor's Notes
#25:Some books would call dsirrev as σ or the level of irreversibility of a system executing a cycle. It is a concequences of claussiun inequality
#35:Coba bikin notes dan pengen lihat efeknya gimana
