Torque Agitator Calculation

Topic: How Do I Estimate The Torque For An Impeller Agitator? 25 February 2013posed by

I need to estimate the torque for an impeller agitator. a gitator. Characteristics of the impeller: d: 17'' x h: 13.5''. For the tank: 3'' diameter x !'' height. "he impeller is an anchor t#pe $ith four %lades. .

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319 Posts Dave DickeyForum DickeyForum Moderator 319

Re: How Do I Estimate The Torque For An Impeller Agitator?  25 February 2013 at 11 11:27am :27am

Your Your ancor impe!!er does not "it your tank. #n ancor impe!!er "or a 23$ diameter tank sou!d be 20$ to 22$ in diameter. %e 17$ diameter impe!!er &i!! &i!! do !itt!e more tan rotate rotate te contents o" te tank' &ic &i!! not provide muc mi(in). *o&ever' + can )ive you a metod "or estimatin) te amount o" tor,ue re,uired. %e viscous po&er number "or your impe!!er is 17-. %e viscous po&er number is is a caracteristic o" te impe!!er )eometry. )eometry. + assumed tat eac o" te "our b!ades is is 1$ &ide. #n ancor impe!!er impe!!er &i!! ave a constant viscous viscous po&er number "or impe!!er eyno!ds numbers !ess tan 1.0. +mpe!!er eyno!ds number number /dimension!ess can be ca!cu!ated by te "o!!o&in) "ormu!a: Re = !"# $ D%& D%& $ ' $ sp"gr" ( )isc %e eyno!ds number is dimension!ess' te constant 10.7 is a conversion "actor and D is your impe!!er diameter in inces' &ic is s,uared'  is te rotationa! speed o" te impe!!er in revo!utions per minute' sp.)r. is te density o" te "!uid as speci"ic )ravity &it respect to &ater /)ramscubic centimeter' and tat ,uantity is divided by te visc te viscosity in centipoise. %e tor,ue "or te impe!!er is as "o!!o&s: Torque To rque *inch+pounds, = -"./!%+. $ )isc $ ' $ D%0 %e tor,ue is in incpounds' te coe""icient is -.4 times 10 to te 4 po&er /0.0000000-4 inc!udes your viscous p o&er number' times te viscosity in centipoise' times te rotationa! speed in rpm' times te impe!!er diameter in inces cubed. Remem1er the 2ormula 2or torque is onl3 )alid 2or Re3nolds num1ers less than "!" #s te eyno!ds number number increases' so does te ca!cu!ated tor,ue. %e impe!!er tor,ue )radua!!y increases as te "!o& becomes more turbu!ent as de"ined by a !ar)er eyno!ds number. %e tor,ue in te turbu!ent ran)e cou!d be more tan 1000 times te tor,ue ca!cu!ated by tis "ormu!a' dependin) on te amount o" rotation o" te "!uid. Your Your sma!! impe!!er may not increase te tor,ue tat muc since you &i!! not be mi(in)' on!y spinnin) te "!uid. "he ans$ers %# this expert are %ased on the %est a&aila%le interpretation of the

information pro&ided. "he consequences of the application of this information are the responsi%ilit# of the user. If clarification is needed please su%mit a further question.

i!!a *ercu!e4ommunit3 Mem1er 1 Post

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Re: How Do I Estimate The Torque For An Impeller Agitator?  25 February 2013 at 3:06pm

%e product mi(ed is so sensitive' tat is &y tat desi)n as been used. %e rotationa! speed is 100P' te viscosity 20 cp and te sp. )r is 1.065. + attac a "i!e &it "urter in"ormation on te impe!!er desi)n. y usin) te "ormu!a you )ave on a precedent topic /ay 31' 2011' + estimated te eyno!ds 8 1.4 ( 106. #s te eyno!ds &as "or a turbu!ent "!o&' + ten estimated te correction "actor' ten a"ter +ve been ab!e to estimate te po&er o" te impe!!er /0.136 *P. Fina!!y' kno&in) tat : %or,ue ;!b".in< 8 39- 000 P ;*P<  2=pi=  ;P<' +ve been ab!e to "ound out te re,uired tor,ue o" 45 !b".in Do you tink' +ve )ot te ri)t pat> %ank you "or your e!p. Attached Files  #)itatordesi)n.pd" 

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Dave DickeyForum Moderator 319 Posts

Re: How Do I Estimate The Torque For An Impeller Agitator?  2- February 2013 at 11:15am

%e attaced impe!!er dra&in) !ooks notin) !ike &at is typica!!y kno&n an an ancor impe!!er. %e impe!!er dra&in) so&s more o" a &ideb!ade padd!e /or turbine impe!!er. @n"ortunate!y' usin) typica! corre!ations and corrections "or modi"ied ancor impe!!ers and &ideb!ade padd!e impe!!ers )ive di""erent resu!ts "or te same dimensiona! e(tremes. ecause te impe!!er !ooks more !ike a "ourb!ade' &ideb!ade padd!e impe!!er' &orkin) "rom simi!ar turbine impe!!ers seems reasonab!e. %e impe!!ertotank diameter ratio and "!uid properties are c!oser to tose common!y mi(ed &it turbine impe!!ers. %e best data "or ancor impe!!ers is at muc i)er viscosities and !ar)er impe!!ertotank diameter ratios. @sin) a modi"ied corre!ation "or a &ideb!ade impe!!er' te eyno!ds number is about 1-'000' te po&er estimate is "or 0.-- p and te resu!tin) tor,ue at 100 rpm is 614 !b" in. %e po&er and tor,ue estimates cou!d be i) compared &it actua! measurements i" te "!uid rotates "ree!y and does not e(perience muc vertica! and radia! "!o&. %e eyno!ds number does indicate turbu!ent conditions' but te "!o& pattern may be more !ike Aouette "!o&' &ic cou!d mean a !o&er tor,ue. %is situation as a su""icient number o" uni,ue caracteristics tat estimates based on more conventiona! mi(in) e,uipment may not be accurate. %e reason "or te ,uestion about tor,ue may in"!uence o& conservative te estimate sou!d be. +" te mi(er drive is siBed based on re,uired tor,ue' a i)er estimate is recommended.

"he ans$ers %# this expert are %ased on the %est a&aila%le interpretation of the information pro&ided. "he consequences of the application of this information are the responsi%ilit# of the user. If clarification is needed please su%mit a further question.