Diagram Moody

Diagram Moody

Ya Moody diagram sangat bermanfaat untuk menghitung aliran yang terjadi pada suatu pipa, sejujurnya saja sangat susah untuk menghitung n ilai friction didalam pipa, apalagi bila pipa tersebut mempunyai panjang yang lumayan, sehingga perbandingan antara diameter dan panjang  pipa sangatlah kecil. cara yang paling mudah adalah dengan pembacaan melalui moody diagram, tanpa mengetahui dengan pasti nilai dari kekasaran pipa, kita dapat memperkirakan dengan mudah melalui  pembacaan diagram ini.

Dasar teori head loss pada pipa karena gesekan dapat dihitung dengan den gan persamaan Darcy-Weisbach Darcy-Weisbach seperti dibawah ini dengan, h = head loss loss f = friction factor   = length of pipe ! = !elocity of fluid trough pipe D = Diameter of pipe g = acceleration due to gra!ity Diagram Moody memberikan faktor gesekan pipa. "aktor ini dapat ditentukan oleh bilangan #eynold dan kekasaran relatif dari $ipa.  bila pipa semakin kasar, maka kemungkinan turbulent akan semakin besar, kekasaran relatif didefinisikan sebagai dengan,  e = absolute roughness D = diameter of pipe sedangkan bilangan reynold didefinisikan sebagai dengan, # = #eynolds number  D = diameter  ! = !elocity % = kenimatic !iscosity of fluid ok. moody diagram dapat dilihat pada diagram dibawah berikut

Cara Baca  Dengan melihat diagram Moody itu menunjukkan bahwa sudut kanan atas benar-benar turbulent dan bagian atas kiri adalah laminar. &ntuk menentukan faktor gesekan, nilai kekasaran relatif dari pipa dapat dilihat di sebelah kanan. 'emudian cari #eynolds number di bagian bawah, tarik keatas sampai memotong, sebelah kiri akan didapatkan nilai faktor gesekan. dan jenis aliran apakah turbulen ataukah laminer 

Contoh Pemakaian

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Diagram Moody

Me ng g un a k anDi a gr a m Mo od yad al a hu nt u kme mp er o l e hn i l a ig es e k a np i p a( f )d and ap atd i l a k u k an d en ganme ng et a hu ib eb er a papa r a me t ers e pe r t i b er i k u t:

1. 2. 3.

• • •

Mat er i al Pi pa,unt ukmenget ahuini l ai kek asar anpi pa( epsi l onat aue) Di amet erPi pa( D) Bi l anganRe y nol d( Re) Se ba g ai c o n t o h:

Ma t e r i a lPi p a=Ga l v a ni z edI r o n=e=0 . 15mm Di a me t e rPi p a=1i n c i=2 5. 4mm Bi l a ng anRe y nol d( Re )=6 000( t u r b ul en ) / D=0 . 0 0 6 0 Has i l per hi t ungane

Pe r h at i k anpa daga mb arc a r aun t u kme ne nt u kanni l a if:

1.

Te nt uk an ni l aie/ D pada s umbu " y "ba gi an k ana n ber war na mer ah dan i k ut ial urgar i s ber war nabi r u( war ni ng! ! ! ,gar i sber war nabi r ut i daksel ur uhny agar i sl ur us ) . 2. Ten t uk anni l ai Repad as umbu" x"bagi anba wahber war namer ahda nt egakl ur us . 3. Per t emuangar i se/ D danRe t ega kl ur uspadasumbu " y "s ebe l ah k i r iber war na c ok l at 0 3 1 9. me r u pa ka nn i l a if=0.

Moody Diagram to estimate friction coecients (ponsored inks )here are two definitions of the friction factor  •

SI based

•

Imperial based

)he (* based friction factor is four times larger than the *mperial based friction factor. SI based Moody Diagram

)he Moody friction factor - λ (or f) - is used in the Darcy-Weisbach major loss e+uation. )he coefficient can be estimated with the diagram below

*f the flow is transient - 2300 < Re < 4000 - the flow !aries between laminar and turbulent flow and the friction coefiicient is not possible to determine. )he friction factor can usually be interpolated between the laminar !alue at Re = 2300 and the turbulent !alue at Re = 4000. Example - SI based Friction Factor

"or a $ pipe with absolute roughness k = 0.0015 10-3 (m), hydraulic diameter  Dh = 0.1 (m) and #eynolds number  Re = 10  - the relati!e rougness can be calculated as 7 

k/Rh = (0.0015 10-3 m) / (0.02 m)

= 0.000075 "rom the diagram abo!e, with the relati!e rougness and the #eynolds number - the friction factor  can be estimated to apro/. 0.011. Alternative Moody Diagram

0 !ery nice Moody diagram in pdf-format from 1lasgow ollege of 2autical (tudies can be found here

•

Moody Diagram

(ponsored inks

Related Topics •

Fluid Mechanics - The study of uids - li!uids and gases" Involves various properties of the uid# such as velocity# pressure# density and temperature# as functions of space and time"

Related Documents •

•

•

Reynolds Number - An introduction and de$nition of the dimensionless %eynolds &umber - 'ith online calculators Major loss in Ducts, Tubes and Pipes  - Ma(or loss - head loss or pressure loss - due to friction in ducts# pipes and tubes Colebroo !"uation - )alculate friction loss coe*cients in pipes# tubes and ducts

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