Experiment-4-unit-ops.docx

Technological Technological Institute of the Philippines – Manila Unit Operations Laboratory II, 1 st Semester 21!"21#

%6IT%TION  Abstract  — This e$periment gi%es an insight to system systemss in%ol%i in%ol%ing ng agitat agitation& ion& Using Using 'iffer 'ifferen entt tan( an' impeller geometries, as )ell as the flui' property, the po)er re*uirement to 'ri%e an impe impell ller er is to be 'ete 'eterm rmin inee' in this this e$periment&

 Index Terms Terms +  Impeller,  Impeller, Agitation, Agitation, Mixing, baffles, power  requirement, vortex 

1. I NTRODUCTION Mixing of fluids is a discipline of fluid mechanics. Fluid motion is used to acceleate the othe!ise slo! pocesses of diffusion and conduction to "ing a"out unifomit# of concentation and tempeatue$ "lend mateials$ facilitate chemical eactions$ "ing a"out intimate contact of multiple  phases$ and so on. %gitation efes to focing a fluid "# mechanical means to flo! in a ciculato# o othe patten inside a &essel. %gitatos usuall# consist of an impelle and a shaft. %n impelle is a oto located !ithin a tu"e o conduit attached to the shaft. It helps enhance the pessue in ode fo the flo! of a fluid "e done. Moden industial agitatos incopoate pocess contol to maintain "ette contol o&e

Fig. 1 Thee ae thee diffeent t#pes of impelles that can "e used in agitation. % popelle is an axial2flo!$ high2speed impelle fo li'uids of lo! &iscosit#. % paddle is fo simple  agitation po"lems. addles tun at slo! to modeate speeds in the cente of a &essel3 the# push the li'uid adiall# and tangentiall# !ith almost no &etical motion at the impelle unless the "lades ae pitched. 4hile tu"ines ae effecti&e o&e a &e# !ide ange of &iscosities.

the mixing pocess . Fo this expeiment !e ae to detemine the po!e e'uiement of diffeent impelles impelles dei&ed fom fluid popeties and tan( and impelle geomet#. )i'uids ae agitated fo a num"e of puposes$ depending on the o"*ecti&es of the pocessing step. These puposes include 1. ,. . /.

0.

Flo! pattens in agitated &essel depends on the t #pe of the impelle$ the chaacteistics chaacteistics of the fluid and the si5e and  popotion of the tan($ "affles "affles and agitato. agitato. %ction of agitation sometimes sometimes leads to fomation of &otex$ !hich is undesia"le "ecause in &otex thee is no eal mixing. The solid paticles in the li'uid settle in the "ottom theefoe$ no dissolution. %nd lastl#$ ai ma# "e entapped in solution causing degadation of oxdisa"le mateials. 6eneall#$ fomation of &otex is undesia"le "ut it can "e pe&ented. In small tan(s$ the impelle can "e mounted off cente. The shaft is mo&ed a!a# fom the centeline of the tan($ then tilted in a plane pependicula to the diection of the mo&e. In lage tan(s$ the agitato ma#"e mounted in the side of the tan($ !ith the shaft in a hoi5ontal plane "ut at an angle !ith a adius. %nd lastl#$ "affles ma# "e installed in lage tan(s. Fig. , sho!s t#pical stied tan( configuations and timea&eaged flo! pattens fo axial flo! and adial flo! impelles. In ode to pe&ent fomation of a &otex$ fou &etical "affles ae nomall# installed.

+usp +uspen endi ding ng soli solid d pati paticl cles es -len -lendi ding ng mis misci ci"l "lee li'u li'uid idss Dispesi Dispesing ng a gas though though the li'uid li'uid in in the the fom fom of small "u""les Dispesi Dispesing ng a second second li'ui li'uid$ d$ immis immisci"le ci"le !ith the fist$ to fom an emulsion o suspension of fine dops omotin omoting g heat heat tans tansfe fe "et!een "et!een the li'uid li'uid and and a coil o *ac(et

)i'uids ae most often agitated in some (ind of tan( o &essel. T#pical agitation pocess &essel is sho!n in Fig. 1. The li'uid depth is appoximatel# e'ual to the diamete of the tan(. %n impelle is mounted on an o&ehung shaft$ !hich is di&en "# a moto. The impelle ceates a flo!  patten in s#stem$ s#stem$ causing the the li'uid to ciculate ciculate though the &essel and etun e&entuall# to the impelle. impelle. These &essels !ee designed depending on the natue of the agitation po"lem.

1

Experiment No. 1 iffusion of Li*ui's through Stagnant -on"iffusing .ir

Re#nolds num"e can "e coelated to the po!e num"e to get the po!e e'uiement using a gaph of Re#nolds num"e$ po!e num"e and the t#pe of impelle used$ as sho!n in Fig .

Fig. , Fo a gi&en impelle and tan( geomet#$ the impelle Re#nolds num"e detemines the flo! patten in the tan(7 Fig 

2

 D  Nρ  μ

ℜ=

,.

!hee D 8 impelle diamete$ N 8 otational speed$ and 9 and : ae the li'uid densit# and &iscosit#. Rotational speed  N is t#picall# epoted in e&olutions pe minute$ o e&olutions pe second in +I units. Radians pe second ae almost ne&e used. T#picall#$ Re ; 1
3

Mateials7

Impelle

4ate  

Metestic(  1A inches Tan(  /eny -& -aran0o $ Chemical ?ngineeing Depatment$ Technological Institute of the hilippinesB College of ?ngineeing and %chitectue$ Manila$ hilippines$ <01/1E e2mail7 chinnaan*oGgmail.comH.

 P gc  ρ N   D

%ppaatus7

Tachomete 

4hile the flo! patten is o"se&ed$ anothe impotant consideation in design of an agitated &essel is the po!e e'uied to di&e the impelle. The po!e  da!n "# the impelle is made dimensionless in a goup called the po!e  num"e7

 N  P =

?@UIM?NT+ %ND %%R%TU+

5

The fom of such coelation can "e found "# dimensional anal#sis$ gi&en the impotant measuements of  the tan( and the impelle$ the distance of the impelle fom the tan( floo$ the li'uid depth$ and the dimensions of the  "affles if the# ae used. The num"e and aangement of the  "affles and the num"e of "lades in the impelle must also  "e fixed. The &aia"les that ente the anal#sis ae the impotant measuements of tan( and impelle$ the &iscosit# and the densit# of the li'uid$ the speed$ and "ecause  Ne!ton>s la! applies$ the dimensional constant gc. The

2

Technological Institute of the Philippines – Manila Unit Operations Laboratory II, 1 st Semester 21!"21#

.

M?TODO)O6J

4IT -%FF)?7

Maine Impelle


Tial 1 11.<<

Tial , .A

Tial  1<.E

/ -lade addle Impelle  Tial Tial Tial 1 ,  .< .0 .1

E
1./

1,.0

A.E

.E0

.1<

A.,


10.

1,.EA

1,.E

A.<

.E

1,
10.A

1A.<

11.E

A./

.<

%&e. ps

1/.
1.,

1<.<

.A<

A.<1

1<.< < 1<.  A.E

Time

T%-)? OF C%)CU)%T?D R ?JNO)D+ NUM-?R %ND O4?R  R ?@UIR?M?NT 4ITOUT -%FF)?7

/.

R ?+U)T %ND DI+CU++ION Ti me

T  H  2 O=30 ° C 

 ρ= 995.602

Maine Impelle  Tial 1 Tial ,

 N  ,0EA. 

 kg m

A ,E. 4

,,</. ,0 1.10 4

Tial  ,/,,0. 1 ,<.// 4

3

 Pave .=21.53 W  −4

 μ=8.196 x 10

 kgm 2

s

Ti me

D%T% FOR  T? +??D OF T? IM?))?R 

/ -lade addle Impelle  Tial 1 Tial , Tial 

 N  1,/1. 

EE 1./ 4

1E001. E, 1.EA 4

1A. A1 E./ 4

4ITOUT -%FF)?7

 Pave .=22.55 W  Maine Impelle


Tial 1 1<.<

Tial , .

Tial  .

/ -lade addle Impelle  Tial Tial Tial 1 ,  /., /. /.EA

E
11./,

.A0

.<

.AA

/.,,

/.EA


11.<<

A.,

.

.

/.1/

E.

1,
1<.,

.1

1<.
.

/.,E

E.1

%&e. ps

1<.A/

.,

.AA

/.<1

/.

0.E<

Time

4IT -%FF)?7

Ti me

Maine Impelle  Tial 1 Tial ,

 N  /. 

3

0A 0.10 4

10
Tial  ,0A/
Experiment No. 1 iffusion of Li*ui's through Stagnant -on"iffusing .ir

 Pave .= 45.44 W 

/ -lade addle Impelle  Tial 1 Tial , Tial 

Ti me

,/,E,<. 1 .10 4

,/10,. ,A 1<. 4

,A<,. 1 10<.,A 4

Calculate the po!e e'uied (4 of the mixe.

6i&en7

Find7

Da 8 <.E1m



 Dt 

 N 



a.

W   J 

=

=

1.A m

<.1,, m

<.10 m

=

 Pave .=118.93 W 

 N  0.

CONC)U+ION %ND R ?COMM?ND%TION

-ased on the data gatheed$ the po!e e'uiement of a maine impelle is less than that of the / "lade paddle. The Re#nolds num"e and po!e e'uiement also inceases !hen !e used "affles in the tan(. Theefoe$ the po!e  e'uiement of an impelle can "e affected "# the fluid  popeties$ as !ell as the tan( and impelle geomet#. E. 1.

E<

=

1.0< e&Bs

 ρ 

=

C,C (gBm 

 µ 

=

F1< cpHF1 x 1< 2 H

% N+4?R+ TO @U?+TION+

 N Re

Fo agitation$ the e'uipment to "e used ma#  "ase on the agitation po"lem. Diffeent t#pes of impelles ma# "e used. % popelle is an axial2flo!$ high2speed impelle fo li'uids of lo! &iscosit#. % paddle is fo simple agitation po"lems. addles tun at slo! to modeate speeds in the cente of a &essel3 the#  push the li'uid adiall# and tangentiall# !ith almost no &etical motion at the impelle unless the "lades ae pitched. 4hile tu"ines ae effecti&e o&e a &e# !ide ange of &iscosities.

=

 D a, N  ρ 

F<.E1H , F1.0
<.<1

=

01A0,.10

Fo

 Da B W   N  p

 N  p 0

=

=

=

0 and  Dt  B  J  1, =

0 fo  N Re

=

01A0, .10

 Pg c 

0

 ρ  N   Da

 P F1H =

FC,CHF1.0
 P  1,/ MBs 1.,/ (4 F1.DD hpH =

% dou"le2flight helix impelle 2ft diamete and 2ft high is opeating at < pm in a ., ft diamete tan(. The tan( is filled A0K full !ith a 1<<< poise fluid ha&ing a densit# of E0 l"Bft. ?stimate hp e'uiement.

 ".

Fo the same conditions$ except fo the solution ha&ing a &iscosit# of 1<<<< c$ calculate the e'uied (4.

,

.

<.<1 a.s

 µ 

=

,.

=

+olution7

?numeate the diffeent e'uipment fo agitation and discuss its uses. 

C< =

 N Re

% flat L "lade tu"ine agitato !ith dis( ha&ing six  "lades is installed in a tan(. The tan( diamete is 1.A m$ the tu"ine diamete is <.E1 m. Dt 8  and the !idth is <.1,, m. The tan( contains fou "affles$ each ha&ing a !idth of <.10 m. The tu"ine is opeated at < pm and the li'uid in the tan( has a &iscosit# of 1< c and a densit# of , (gBm.

=

 N  p 8 /

4

 D a  N  ρ   µ 

F<.E1H , F1.0
1<

=

01.A0

Technological Institute of the Philippines – Manila Unit Operations Laboratory II, 1 st Semester 21!"21#

 N  p

/

=

 Pg c 

0

 ρ  N   D a

 P F1H =

FC,CHF1.0
 P  1<0C J  B  s =

=

1.<0CkW  1./,hP  =

5