Ṣe iwọn resistance inu si wahala rirẹ

Viscosity agbara (ti a tun pe ni viscosity pipe) ṣe iṣiro iye agbara ti o nilo lati gbe fẹlẹfẹlẹ kan ti omi kọja miiran. O jẹ ohun-ini abinibi ti omi funrararẹ, ominira ti iwuwo. Awọn iye ti o ga julọ tumọ si resistance diẹ sii.

Agbekalẹ: τ = μ × (du/dy) nibiti τ = wahala rirẹ, du/dy = gradient iyara

Awọn ẹya: Pa·s (SI), poise (P), centipoise (cP). Omi @ 20°C = 1.002 cP

Viscosity agbara ti a pin nipasẹ iwuwo

Viscosity kinematic ṣe iwọn bi omi ṣe nṣàn ni iyara labẹ walẹ. O ṣe akiyesi mejeeji resistance inu (viscosity agbara) ati ibi-pupọ fun iwọn didun (iwuwo). A lo nigbati ṣiṣan ti o ni agbara walẹ ṣe pataki, gẹgẹbi ṣiṣan epo tabi sisọ omi.

Agbekalẹ: ν = μ / ρ nibiti μ = viscosity agbara, ρ = iwuwo

Awọn ẹya: m²/s (SI), stokes (St), centistokes (cSt). Omi @ 20°C = 1.004 cSt

• μ (agbara) = 1.002 cP = 0.001002 Pa·s
• ρ (iwuwo) = 998.2 kg/m³
• ν (kinematic) = μ/ρ = 1.004 cSt = 1.004 mm²/s
• Iwọn: ν/μ ≈ 1.0 (omi ni itọkasi)

• μ (agbara) = 62 cP = 0.062 Pa·s
• ρ (iwuwo) = 850 kg/m³
• ν (kinematic) = μ/ρ = 73 cSt = 73 mm²/s
• Akiyesi: Kinematic jẹ 18% ga ju agbara lọ (nitori iwuwo kekere)

• μ (agbara) = 1,412 cP = 1.412 Pa·s
• ρ (iwuwo) = 1,261 kg/m³
• ν (kinematic) = μ/ρ = 1,120 cSt = 1,120 mm²/s
• Akiyesi: Viscous pupọ—1,400× nipon ju omi lọ

• μ (agbara) = 0.0181 cP = 1.81×10⁻⁵ Pa·s
• ρ (iwuwo) = 1.204 kg/m³
• ν (kinematic) = μ/ρ = 15.1 cSt = 15.1 mm²/s
• Akiyesi: Agbara kekere, kinematic giga (awọn gaasi ni iwuwo kekere)

Ilana ASTM D88, ti a lo ni ibigbogbo ni Ariwa America fun awọn ọja epo

ν(cSt) = 0.226 × SUS - 195/SUS (wulo fun SUS > 32)

• Wiwọn ni awọn iwọn otutu kan pato: 100°F (37.8°C) tabi 210°F (98.9°C)
• Ibiti o wọpọ: 31-1000+ SUS
• Apeere: Epo SAE 30 ≈ 300 SUS @ 100°F
• Ẹya Saybolt Furol (SFS) fun awọn omi ti o ni viscous pupọ: iho ×10 tobi

Ilana British IP 70, ti o wọpọ ni UK ati Commonwealth tẹlẹ

ν(cSt) = 0.26 × RW1 - 179/RW1 (wulo fun RW1 > 34)

• Wiwọn ni 70°F (21.1°C), 100°F, tabi 140°F
• Ẹya Redwood No. 2 fun awọn omi ti o nipọn
• Iyipada: RW1 ≈ SUS × 1.15 (isunmọ)
• Ti rọpo ni pataki nipasẹ awọn ilana ISO ṣugbọn tun tọka si ni awọn alaye lẹkunrẹrẹ agbalagba

Ilana German DIN 51560, ti a lo ni Yuroopu ati ile-iṣẹ epo

ν(cSt) = 7.6 × °E - 6.0/°E (wulo fun °E > 1.2)

• Wiwọn ni 20°C, 50°C, tabi 100°C
• °E = 1.0 fun omi @ 20°C (nipasẹ itumọ)
• Ibiti o wọpọ: 1.0-20°E
• Apeere: Epo diesel ≈ 3-5°E @ 20°C

Idanwo laabu ti o gunjulo julọ ni agbaye (lati ọdun 1927) ni University of Queensland fihan ipolowo (ota) ti nṣàn nipasẹ funnel kan. O dabi ri to ṣugbọn o jẹ omi ti o ga julọ ti o ga julọ—100 bilionu igba diẹ viscous ju omi lọ! Awọn isubu 9 nikan ti ṣubu ni ọdun 94.

Lava Basaltic (viscosity kekere, 10-100 Pa·s) ṣẹda awọn eruption onírẹlẹ ti ara Hawahi pẹlu awọn odò ti nṣàn. Lava Rhyolitic (viscosity giga, 100,000+ Pa·s) ṣẹda awọn eruption ibẹjadi ti ara Oke St. Helens nitori awọn gaasi ko le sa fun. Viscosity gangan ṣe apẹrẹ awọn oke onina.

Ẹjẹ jẹ 3-4× diẹ viscous ju omi lọ (3-4 cP @ 37°C) nitori awọn sẹẹli ẹjẹ pupa. Viscosity ẹjẹ ti o ga pọ si eewu ọpọlọ/ikọlu ọkan. Aspirin iwọn lilo kekere dinku viscosity nipa idilọwọ akojọpọ platelet. Idanwo viscosity ẹjẹ le sọ asọtẹlẹ arun inu ọkan ati ẹjẹ.

Lodi si itan-akọọlẹ olokiki, awọn ferese atijọ ko nipọn ni isalẹ nitori ṣiṣan. Viscosity gilasi ni iwọn otutu yara jẹ 10²⁰ Pa·s (aimọye aimọye igba ti omi). Yoo gba gun ju ọjọ-ori agbaye lọ lati ṣàn 1mm. O jẹ ri to otitọ, kii ṣe omi ti o lọra.

SAE 10W-30 tumọ si: 10W = viscosity igba otutu @ 0°F (sisan iwọn otutu kekere), 30 = viscosity @ 212°F (aabo iwọn otutu iṣẹ). 'W' jẹ fun igba otutu, kii ṣe iwuwo. Awọn epo olona-ipele lo awọn polima ti o yika nigbati o tutu (viscosity kekere) ati gbooro nigbati o gbona (ṣetọju viscosity).

Awọn strider omi lo anfani ẹdọfu dada, ṣugbọn tun lo anfani viscosity omi. Awọn iṣipopada ẹsẹ wọn ṣẹda awọn iji lile ti o Titari lodi si resistance viscous, ti nfa wọn siwaju. Ninu omi viscosity odo (imọ-jinlẹ), wọn kii yoo le gbe—wọn yoo yọ laisi isunki.

Isaac Newton ṣe apejuwe viscosity ni Principia Mathematica. Ṣe afihan imọran ti 'ija inu' ninu awọn omi.

Jean Poiseuille ṣe iwadi sisan ẹjẹ ninu awọn capillaries. Ṣe agbekalẹ Ofin Poiseuille ti o ni ibatan oṣuwọn sisan si viscosity.

George Stokes ṣe agbekalẹ awọn idogba fun sisan viscous. Ṣe afihan ibatan laarin agbara ati viscosity kinematic.

Osborne Reynolds ṣe afihan nọmba Reynolds. Ṣe ibatan viscosity si ijọba sisan (laminar vs. rudurudu).

Saybolt viscometer jẹ boṣewa ni AMẸRIKA. Ọna ife efflux di boṣewa ile-iṣẹ epo.

Poise ati stokes ni a fun ni orukọ bi awọn ẹya CGS. 1 P = 0.1 Pa·s, 1 St = 1 cm²/s di boṣewa.

Idanwo ju ipolowo silẹ bẹrẹ ni University of Queensland. Si tun nṣiṣẹ—idanwo laabu ti o gunjulo julọ lailai.

SI gba Pa·s ati m²/s bi awọn ẹya boṣewa. Centipoise (cP) ati centistokes (cSt) wa ni wọpọ.

ASTM D445 ṣe iwọn wiwọn viscosity kinematic. Viscometer capillary di boṣewa ile-iṣẹ.

Awọn viscometer iyipo n jẹ ki wiwọn awọn omi ti kii ṣe Newtonian ṣiṣẹ. Pataki fun awọn kikun, awọn polima, ounjẹ.

Awọn viscometer oni-nọmba ṣe adaṣe wiwọn. Awọn iwẹ ti o ni iṣakoso iwọn otutu ṣe idaniloju deede si ± 0.01 cSt.

Yiyan epo engine, omi hydraulic, ati lubrication gbigbe:

• Awọn ipele SAE: 10W-30 tumọ si 10W @ 0°F, 30 @ 212°F (awọn sakani viscosity kinematic)
• Awọn ipele ISO VG: VG 32, VG 46, VG 68 (viscosity kinematic @ 40°C ni cSt)
• Yiyan gbigbe: Tinrin pupọ = yiya, nipọn pupọ = ija/ooru
• Atọka Viscosity (VI): Ṣe iwọn ifamọ iwọn otutu (giga = dara julọ)
• Awọn epo olona-ipele: Awọn afikun ṣetọju viscosity kọja awọn iwọn otutu
• Awọn ọna ẹrọ hydraulic: Ni deede 32-68 cSt @ 40°C fun iṣẹ ṣiṣe to dara julọ

Awọn alaye lẹkunrẹrẹ viscosity epo, epo robi, ati isọdọtun:

• Epo epo ti o wuwo: Wiwọn ni cSt @ 50°C (gbọdọ wa ni kikan lati fa omi)
• Diesel: 2-4.5 cSt @ 40°C (spec EN 590)
• Isọdi epo robi: Imọlẹ (<10 cSt), alabọde, wuwo (>50 cSt)
• Sisan opo gigun ti epo: Viscosity pinnu awọn ibeere agbara fifa
• Awọn ipele epo bunker: IFO 180, IFO 380 (cSt @ 50°C)
• Ilana isọdọtun: Visbreaking dinku awọn ida ti o wuwo

Iṣakoso didara ati iṣapeye ilana:

• Gbigbe oyin: 2,000-10,000 cP @ 20°C (da lori ọrinrin)
• Aitasera omi ṣuga oyinbo: Omi ṣuga oyinbo Maple 150-200 cP, omi ṣuga oyinbo agbado 2,000+ cP
• Awọn ọja ifunwara: Viscosity ipara ni ipa lori sojurigindin ati rilara ẹnu
• Chocolate: 10,000-20,000 cP @ 40°C (ilana tempering)
• Carbonation ohun mimu: Viscosity ni ipa lori dida o ti nkuta
• Epo sise: 50-100 cP @ 20°C (oju eefin ni ibamu pẹlu viscosity)

Kun, awọn alemora, awọn polima, ati iṣakoso ilana:

• Viscosity kun: 70-100 KU (awọn ẹya Krebs) fun aitasera ohun elo
• Aṣọ sokiri: Ni deede 20-50 cP (nipọn pupọ di, tinrin pupọ nṣiṣẹ)
• Awọn alemora: 500-50,000 cP da lori ọna ohun elo
• Awọn yo polima: 100-100,000 Pa·s (extrusion/molding)
• Awọn inki titẹ sita: 50-150 cP fun flexographic, 1-5 P fun aiṣedeede
• Iṣakoso didara: Viscosity tọkasi aitasera ipele ati igbesi aye selifu

Viscosity agbara (Pa·s, poise) ṣe iwọn resistance inu omi si rirẹ—'nipọn' pipe rẹ. Viscosity kinematic (m²/s, stokes) jẹ viscosity agbara ti a pin nipasẹ iwuwo—bi o ṣe nṣàn ni iyara labẹ walẹ. O nilo iwuwo lati yipada laarin wọn: ν = μ/ρ. Ronu nipa rẹ bi eyi: oyin ni viscosity agbara giga (o nipọn), ṣugbọn mercury tun ni viscosity kinematic giga laibikita jijẹ 'tinrin' (nitori pe o jẹ ipon pupọ).

Kii ṣe laisi mimọ iwuwo omi ni iwọn otutu wiwọn. Fun omi nitosi 20°C, 1 cP ≈ 1 cSt (nitori iwuwo omi jẹ ≈ 1 g/cm³). Ṣugbọn fun epo engine (iwuwo ≈ 0.9), 90 cP = 100 cSt. Oluyipada wa dina awọn iyipada oriṣiriṣi lati yago fun awọn aṣiṣe. Lo agbekalẹ yii: cSt = cP / (iwuwo ni g/cm³).

Awọn ipele viscosity SAE ṣalaye awọn sakani viscosity kinematic. '10W' tumọ si pe o pade awọn ibeere sisan iwọn otutu kekere (W = igba otutu, idanwo ni 0°F). '30' tumọ si pe o pade awọn ibeere viscosity iwọn otutu giga (idanwo ni 212°F). Awọn epo olona-ipele (gẹgẹbi 10W-30) lo awọn afikun lati ṣetọju viscosity kọja awọn iwọn otutu, ko dabi awọn epo ipele-ẹyọkan (SAE 30) eyiti o tinrin ni iyalẹnu nigbati o gbona.

Awọn iṣẹju-aaya Saybolt Universal (SUS) ṣe iwọn bi o ṣe gba to fun 60mL ti omi lati ṣan nipasẹ iho ti a ti ṣe iwọn. Agbekalẹ ti o da lori iriri jẹ: cSt = 0.226×SUS - 195/SUS (fun SUS > 32). Fun apẹẹrẹ, 100 SUS ≈ 21 cSt. SUS tun nlo ni awọn alaye lẹkunrẹrẹ epo laibikita jijẹ ọna agbalagba. Awọn laabu ode oni nlo awọn viscometer kinematic ti o ṣe iwọn cSt taara fun ASTM D445.

Iwọn otutu ti o ga julọ fun awọn molikula ni agbara kainetik diẹ sii, ti o jẹ ki wọn rọra kọja ara wọn ni irọrun diẹ sii. Fun awọn olomi, viscosity ni deede dinku 2-10% fun °C. Epo engine ni 20°C le jẹ 200 cP ṣugbọn 15 cP nikan ni 100°C (idinku 13×!). Atọka Viscosity (VI) ṣe iwọn ifamọ iwọn otutu yii: awọn epo VI giga (100+) ṣetọju viscosity dara julọ, awọn epo VI kekere (<50) tinrin ni iyalẹnu nigbati o ba gbona.

Pupọ julọ awọn ọna ẹrọ hydraulic ṣiṣẹ dara julọ ni 25-50 cSt @ 40°C. Kere ju (<10 cSt) nfa jijo inu ati yiya. Giga ju (>100 cSt) nfa idahun onilọra, agbara agbara giga, ati kikọ ooru. Ṣayẹwo spec olupese fifa soke rẹ—awọn ifasoke vane fẹ 25-35 cSt, awọn ifasoke piston farada 35-70 cSt. ISO VG 46 (46 cSt @ 40°C) jẹ epo hydraulic gbogbogbo ti o wọpọ julọ.

Ko si o pọju imọ-jinlẹ, ṣugbọn awọn wiwọn iṣe di nira ju 1 million cP (1000 Pa·s). Bitumen/ipolowo le de 100 bilionu Pa·s. Diẹ ninu awọn yo polima kọja 1 million Pa·s. Ni awọn viscosity ti o pọju, aala laarin omi ati ri to di didan—awọn ohun elo wọnyi ṣe afihan mejeeji sisan viscous (bii awọn olomi) ati imularada rirọ (bii awọn okele), ti a pe ni viscoelasticity.

Poise bu ọla fun Jean Léonard Marie Poiseuille (1840s), ẹniti o kẹkọọ sisan ẹjẹ ninu awọn capillaries. Stokes bu ọla fun George Gabriel Stokes (1850s), ẹniti o gba awọn idogba fun sisan viscous ati fihan ibatan laarin agbara ati viscosity kinematic. Reyn kan (iwon-agbara iṣẹju-aaya fun square inch) ni a fun ni orukọ lẹhin Osbourne Reynolds (1880s), olokiki fun nọmba Reynolds ni awọn agbara omi.