D091201034 - Ariq Rabbani Sutrisno - Tugas Termodinamika 3
D091201034 - Ariq Rabbani Sutrisno - Tugas Termodinamika 3
D091201034 - Ariq Rabbani Sutrisno - Tugas Termodinamika 3
2. Each receives QH from the hot reservoir. The reversible cycle develops work WR, while the
irreversible cycle develops work WI. The reversible cycle discharges QC to the cold reservoir,
while the irreversible cycle discharges QC.
a) Evaluate cycle for cycle I in terms of WI, WR, and temperature TC of the cold reservoir only.
b) Demonstrate that WI < WR and Q’C > QC.
ANSWER:
a. Q siklus = WR – WI / TC
b. WR > WI
WR = QH - QC
WI = QH – Q’C
QH – QC > QH -Q’C
Q’C > QC
3. A reversible refrigeration cycle R and an irreversible refrigeration cycle I operate between the
same two reservoirs and each removes QC from the cold reservoir. The net work input required
by R is WR, while the net work input for I is WI. The reversible cycle discharges QH to the hot
reservoir, while the irreversible cycle discharges Q’H. Show that WI > WR and Q’H > QH.
ANSWER:
4. A reversible power cycle receives energy Q1 and Q2 from hot reservoirs at temperatures T1 and
T2, respectively, and discharges energy Q3 to a cold reservoir at temperature T3.
a) Obtain an expression for the thermal efficiency in terms of the ratios T1/T3, T2/T3, q =
Q2/Q1.
b) Discuss the result of part (a) in each of these limits: lim q S 0, lim q S , lim T1 S .
ANSWER:
a. n = W/TH
W/TH > W/T’H W menghilang karena kedua siklus menghasilkan kerja yang sama
T’H > TH
b. n = W/TC
W/TC > W/ T’C W menghilang karena kedua siklus menghasilkan kerja yang sama
T’C > W/TC
c. n = W/TH
W/TH > W/T’H W menghilang karena kedua siklus menghasilkan kerja yang sama
T’H > TH
6. The system shown schematically in Fig. P6.6 undergoes a cycle while receiving energy at the rate
Q0 from the surroundings at temperature T0, from a source at temperature Ts, and delivering
energy at the rate at a use temperature Tu. There are no other energy transfers. For Ts Tu T0,
obtain an expression for the maximum theoretical value of in terms of and the temperatures Ts,
Tu, and T0.
ANSWER:
= QS . (1 – T0/TS) / (1-T0 / TU)
ANSWER
a. Benar karena Perubahan entropi sistem tertutup hanya bergantung pada keadaan sistem, yang
berarti tidak bergantung pada cara sistem mencapai keadaan tersebut.
b. Salah karena Perubahan entropi dalam proses isothermal Δs = -R ln (p2 / p1) = R ln (v2 / v1)
menyatakan bahwa entropi dapat meningkat (ekspansi) atau menurun (kompresi).
c. Benar karena energi internal tertentu dan entalpi gas ideal adalah fungsi suhu saja, dan entropi
spesifik adalah fungsi suhu, tekanan dan volume tertentu.
d. Salah karena diambil dari rumus Gibbs du = Tds – Pdv seharusnya Tds = dU + Pdv
e. Salah karena entropi berbanding lurus dengan suhu, jika suhu meningkat maka entropi juga
meningkat
8. A closed system consists of an ideal gas with constant specific heat ratio k.
a) The gas undergoes a process in which temperature increases from T1 to T2. Show that the
entropy change for the process is greater if the change in state occurs at constant pressure than
if it occurs at constant volume. Sketch the processes on p–v and T–s coordinates.
b) Using the results of (a), show on T–s coordinates that a line of constant specific volume
passing through a state has a greater slope than a line of constant pressure passing through
that state.
c) The gas undergoes a process in which pressure increases from p1 to p2. Show that the ratio of
the entropy change for an isothermal process to the entropy change for a constant-volume
process is (1 - k). Sketch the processes on p–v and T–s coordinates.
9. Answer the following true or false. If false, explain why.
a) A process that violates the second law of thermodynamics violates the first law of
thermodynamics
b) When a net amount of work is done on a closed system undergoing an internally reversible
process, a net heat transfer of energy from the system also occurs.
c) One corollary of the second law of thermodynamics states that the change in entropy of a
closed system must be greater than zero or equal to zero.
d) A closed system can experience an increase in entropy only when irreversibilities are present
within the process
e) Entropy is produced in every internally reversible process of a closed system.
f) In an adiabatic and internally reversible process of a closed system, the entropy remains
constant.
g) The energy of an isolated system must remain constant, but the entropy can only decrease.
ANSWER:
a. Salah karena hukum pertama dan kedua termodinamika bersifat independent ( berdiri
sendiri)
b. Salah karena komperesi reversible internal adibatik
c. Salah karena hasil entropi harus lebih besar atau sama dengan nol.
d. Benar karena Entropi bernilai 0 dalam proses reversibel dan meningkat dalam proses
ireversibel
e. Salah karena Perubahan entropi dari proses adiabatik yang dapat dibalik secara internal
menghasilkan nol.
f. Benar karena Proses adiabatik adalah versi khusus dari proses isentropik tidak ada
perubahan entropi dan proses reversibel internal hanya dapat muncul jika tidak ada
perubahan entropi
g. Salah karena dalam sistem yang terisolasi secara termal, energi harus tetap konstan tetapi
entropi hanya dapat meningkat atau tetap
10.A fixed mass of water m, initially a saturated liquid, is brought to a saturated vapor condition while
its pressure and temperature remain constant
a) Derive expressions for the work and heat transfer in terms of the mass m and properties that
can be obtained directly from the steam tables.
b) Demonstrate that this process is internally reversible
ANSWER:
a. W = mp (Vg – Vf)
Q = m (Hg – Hf)