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CHAPTER 9. AGITATION AND MIXING
ABRAHAM ROGELIO MARTIN GARCIA
PRESENTATION OUTLINE
-Definitions -Purposes of agitation -Devices to produce agitation -Power consumption of agitators -Blending andMixing -Suspension of solid particles -Dispersion Operations -Agitator selection and Scale up
Copyright ©2003 A. R. Martin
DEFINITIONS • Agitation: It refers to the induced motion of a“homogenous” material in a specified way • Mixing: It is the random distribution, into and through one another, of two or more initially separate phases PURPOSES OF AGITATION • Suspending solid particles •Blending miscible liquids • Dispersing a gas through the liquid • Dispersing a second liquid to form an emulsion or suspension • Promoting heat transfer
Copyright ©2003 A. R. Martin
1
DEVICES TOPRODUCE AGITATION
IMPELLERS • Propellers (high-speed, low viscosity) • Turbines (Moderate viscosity) • High-efficiency impellers
Three-blade marine propeller
Straight-blade turbine
Diskturbine
Pitched-blade turbine Concave-blade CD-6 impeller
Source: McCabe et al. 2001
Copyright ©2003 A. R. Martin
DESIGN OF TURBINES
Da Dt E Dt H Dt W Da J Dt L Da
1 3 1 3 1 1 5 1 12 1 4S1 S2 S3 S4 S5 S6
Source: McCabe et al. 2001
Copyright ©2003 A. R. Martin
2
POWER CONSUMPTION OF AGITATORS It is a function of the volumetric flow rate and the kinetic energy
Values ofNQ NQ q K > SDa n 1 k tan E SDaW @ q (Flow number) 3 nDa Impeller Marine propellers (square pitch) Four-blade 45q turbine (W/Da)=1/6 Disk turbine HE-3 high-efficiency impeller 0.5 0.87 1.3 0.473 q v nDa
NQ
Ek P P
U Vt 2
2 q Ek
U
2
DSnDa 2
NQ ¸ ¸
Un 3 Da5 ¨ ¨
©
§ D 2S 2
2 2
· ¹
Np P
P Un 3 Da5
D 2S 2
NQ
Un 3 Da5
(Power number)Copyright ©2003 A. R. Martin
Np
\ Re, Fr, S1 , S 2 ,..., S n
Source: McCabe et al. 2001
Copyright ©2003 A. R. Martin
3
P P P
5 N p n 3 Da U
For Re 10
3 K L n 2 Da P
For...
ABRAHAM ROGELIO MARTIN GARCIA
PRESENTATION OUTLINE
-Definitions -Purposes of agitation -Devices to produce agitation -Power consumption of agitators -Blending andMixing -Suspension of solid particles -Dispersion Operations -Agitator selection and Scale up
Copyright ©2003 A. R. Martin
DEFINITIONS • Agitation: It refers to the induced motion of a“homogenous” material in a specified way • Mixing: It is the random distribution, into and through one another, of two or more initially separate phases PURPOSES OF AGITATION • Suspending solid particles •Blending miscible liquids • Dispersing a gas through the liquid • Dispersing a second liquid to form an emulsion or suspension • Promoting heat transfer
Copyright ©2003 A. R. Martin
1
DEVICES TOPRODUCE AGITATION
IMPELLERS • Propellers (high-speed, low viscosity) • Turbines (Moderate viscosity) • High-efficiency impellers
Three-blade marine propeller
Straight-blade turbine
Diskturbine
Pitched-blade turbine Concave-blade CD-6 impeller
Source: McCabe et al. 2001
Copyright ©2003 A. R. Martin
DESIGN OF TURBINES
Da Dt E Dt H Dt W Da J Dt L Da
1 3 1 3 1 1 5 1 12 1 4S1 S2 S3 S4 S5 S6
Source: McCabe et al. 2001
Copyright ©2003 A. R. Martin
2
POWER CONSUMPTION OF AGITATORS It is a function of the volumetric flow rate and the kinetic energy
Values ofNQ NQ q K > SDa n 1 k tan E SDaW @ q (Flow number) 3 nDa Impeller Marine propellers (square pitch) Four-blade 45q turbine (W/Da)=1/6 Disk turbine HE-3 high-efficiency impeller 0.5 0.87 1.3 0.473 q v nDa
NQ
Ek P P
U Vt 2
2 q Ek
U
2
DSnDa 2
NQ ¸ ¸
Un 3 Da5 ¨ ¨
©
§ D 2S 2
2 2
· ¹
Np P
P Un 3 Da5
D 2S 2
NQ
Un 3 Da5
(Power number)Copyright ©2003 A. R. Martin
Np
\ Re, Fr, S1 , S 2 ,..., S n
Source: McCabe et al. 2001
Copyright ©2003 A. R. Martin
3
P P P
5 N p n 3 Da U
For Re 10
3 K L n 2 Da P
For...
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