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8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
http://slidepdf.com/reader/full/thermodinamika-tekanan-alat-ukurnya-unsada-by-ridwan 1/16
MACAM-MACAM PROSES
• Proses isotermal: proses pada suhuT konstan.
• Proses isobaris: proses pada tekananP konstan.
• Proses isokhoris (isometris): prosespada volume spesifk ν konstan.
• Proses adiabatik : proses di manatidak teradi pertukaran kalor den!anlin!kun!an.
• Proses isentropik : proses pada
8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
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"E#A$A$
• "ekanan (P) : gaya (F) per satuan luas (A).
• Satuan tekanan adalah pas%al (Pa) & $'m.
• ntuk *enda padat !a+a per luas satuan tidak dise*uttekanan, tetapi tegangan (stress).
• ntuk uida diam, tekanan adalah sama ke se!ala arah.
• "ekanan di dalam uida menin!kat sesuai den!ankedalamann+a aki*at *erat uida (pen!aruh !ravitasi)sehin!!a uida pada *a!ian *aah menan!!un! *e*an
+an! le*ih *esar daripada uida di *a!ian atas.• "etapi tekanan tidak *ervariasi pada arah horisontal.
• "ekanan !as di dalam tan!ki dapat dian!!ap sera!amkarena *erat !as terlalu ke%il dan tidak men!aki*atkanpen!aruh +an! *erarti.
8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
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"E#A$A$: #R, A"M,/A#M• "ekanan aktual pada posisi tertentu dise*ut tekanan
absolut dan diukur se%ara relati0 terhadap tekananvakum, +aitu tekanan nol mutlak.
• #e*an+akan pen!ukur tekanan dikali*rasi untuk
mem*a%a nol di atmos0er (tekanan atmos0er lokal).• Per*edaan tekanan a*solut dan tekanan atmos0er
dise*ut tekanan ukur (pressure gage).
• "ekanan di *aah tekanan atmos0er dise*ut tekananvakum (vacuum pressure) dan diukur den!an
pen!ukur vakum +an! menunukkan per*edaan antaratekanan atmos0er dan tekanan a*solut.
• P!a!e & Pa*s 1 Patm (untuk P 2 Patm)
• Pva% & Patm 1 Pa*s (untuk P 3 Patm)
8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
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"E#A$A$ #R, "E#A$A$
A"MOS4ER, "E#A$A$ /A#M
8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
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PE$5#R "E#A$A$
PRESSRE5A5E
MA$OME"ER
6AROME"E
8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
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PR7$S7P MA$OME"ER
Perhatikan!am*ar:
• Seim*an! Σ4& 8
• P9 & P
•
A P9 & A Patm W
di mana W = m
g = ρ V g = ρ A
& "ekanan ukur di dalam tan!
8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
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EXAMPLE : Manometer
A manometer is used tomeasure the pressure in atank. "he uid used has a
spe%if% !ravit+ o0 8.;<,and the manometer%olumn hei!ht is << %m, asshon in 4i!ure. 70 the lo%al
atmospheri% pressure is =>kPa, determine thea*solute pressure ithinthe tank.
8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
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E?AMP@E: SO@"7O$
8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
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E?AMP@E: M@"74@7 MA$OME"ER
Bater in a tank ispressuried *+ air, and thepressure is measured *+ amultiuid manometer (see
4i!ure). "he tank is lo%atedon a mountain at an altitudeo0 9D88 m here theatmospheri% pressure is
;<.> kPa. etermine the airpressure in the tank i0 h9 &
8.9 m, h & 8. m, and h &
8.< m. "ake the densities
o0 ater, oil, and mer%ur+ to*e 9888 k!'m, ;<8 k!'m,
8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
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SO@"7O$
8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
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AP@7#AS7 MA$OME"ER
P1 ρ 1g(a h) - ρ 2gh - ρ 1ga & P2
P1 - P2 & ( ρ 2 - ρ 1 )gh
ntuk ρ 2 22 ρ 1 :
P1 - P2 F ρ 2 g h
Measurin! thepressure dropa%ross a o
se%tion or a odevi%e *+ adiGerentialmanometer:
8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
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6AROME"ER "orri%elli
Patm = g h
8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
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E?AMP@E: 6AROME"ER
• etermine the atmospheri% pressureat a lo%ation here the *arometri%readin! is HD8 mm I! and the
!ravitational a%%eleration is g 9.81ms2. Assume the temperature o0mer%ur+ to *e 98oC, at hi%h its
densit+ is 9,<H8 k!'m.
8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
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E?AMP@E: SO@"7O$
8/17/2019 Thermodinamika (Tekanan & Alat Ukurnya) UNSADA By Ridwan
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"E#A$A$ A"MOS4ER
ELEVASI(m)
E!A"A"
(kPa)
E!A"A"
(mm#g)
8 (sealevel)
989.< H>8.88
9888 ;=.;; >HD.9<
888 H=.<8 <=>.8
<888 <D.8< D8<.D998,888 >.< 9=;.HH
8,888 <.< D9.D; o0 thum*: naik 98 m, tekanan atmos0er turun 9 m