Example Data Batch Volume Vessel Diameter Specific Gravity difference Viscosity Ratio Density Viscosity
8840 9.5 0.4 1200 1100 15000
gal ft
33.46294 m3 2.8956 m
1180.83 ft3
kg/m3 cp
15 kg/m s
Enter value in colored cell
Step-1 Defining the intensity of mixing
0.4
ft/sec Specific Gravity Difference Less than 0.1 Less than 0.1
Mixing Scale 1 2 3 4 5 6 7 8 9 10
Bulk Velocity (ft/sec) Application 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Miniumum Liquid Motion Miniumum Liquid Motion
Characteristic of most agitation used in chemical industry Less than 0.6
Requires high degree of agitation Less than 1.0
Viscosity Ratio Less than 100 Less than 100
Others
Less than 10000
Suspend trace solids less than 2% with settling rate of 2 to 4 ft/min
Less than 100000
Suspend trace solids less than 2% with settling rate of 4 to 6 ft/min
Step-2 Calculating Teq assuming square batch tank Volume of the contents Equivalent Diameter Volumetric flow rate V Teq Q = = = = 1180.825 ft3 11.45791 ft 41.22306 ft3/sec 2473.384 ft3/min 3.49237 m
Dont alter any value
Step-3 Selecting Agitator Dia Agitator Type D/T ratio W/D Select Ratio of D/T Impeller Dia Impeller Width
Pitched Blade Impeller with 4 blades 0.2 to 0.6 1/5 0.4 1.4 m 0.28 m 55.0 in 11.0 in
Step-4 Calculation of Required rpm Iteration Assume initial rpm Impeller reynolds Number From graph, impeller pumping number Recalculating the rpm required Difference Step-5 Closest standard rpm Reynolds number Viscosity correction factor Power Number Power Requirement 68 rpm 162.2 1.35 1.85 15755.1 kg m2 / s3 15755.1 Watts 21.1 hp 85 24.9 hp 25 hp 1.133 rpm 1 100 238.5 0.44 58.4 41.6 2 90 214.7 0.43 59.7 30.3 3 70 167.0 0.4 64.2 5.8 4 65 155.0 0.395 65.0 0.0
Assume loading % HP Required
4.58 ft
Step-6 Deciding number of impellers Calculated rpm Power required Calculating Height of the tank Vessel Dia For 1 in height, Volume occupied For occupying Height will be Height to Diameter ratio No of Impeller required Z Z/T V 0.16717853 m3 33.462936 m3 200.162876 in 1.75581471 2 5.084137 T 2.8956 m N P 68 rpm 25 hp 1.133333
Load shared by each impeller Initial estimate of diameter Power Number Diameter Impeller Reynolds number For the above reynolds number, Viscosity correction factor Power Number Recalculating Diameter Lower Impeller Location from bottom Upper Impeller Location from bottom
10.563798 hp
7877.553
1.8495 1.21611392 m 122.915771 47.87841
1.47 2.0139 1.19557699 m 0.9652 m 3.38942471 m 47.06987 37.99992 133.4417
Instead of I no of
55.00 in Impeller, two nos with
rps
Viscosity,cp <25000 <25000 >25001 >25001
Maximum Level,Z/T 1.4 2.1 0.8 1.6
No of Impeller 1 2 1 2
kg m2 / s3
in
in in in
, two nos with
47.06987 in diameter is required to provide the same agitation degree
Impeller clearance Lower Upper Z/3 T/3 (2/3) Z Z/3 T/3 (2/3) Z
Pumping Number curve for 4 blade pitched blade turbine impeller (Np = 1.37)
Viscosity correction factor as a function of reynolds number
Values of turbulent power number NP for various impeller geometries. Note: W/D is actual blade-width-to-impeller-diameter ratio.
Vessel Dia ft m 3 0.91 3.5 1.07 4 1.22 4.5 1.37 5 1.52 5.5 1.68 6 1.83 6.5 1.98 7 2.13 7.5 2.29 8 2.44 8.5 2.59 9 2.74 9.5 2.90 10 3.05 11 3.35 11.5 3.51 12 3.66
Volume m3/in gal/in 0.02 4.40 0.02 5.99 0.03 7.83 0.04 9.91 0.05 12.23 0.06 14.80 0.07 17.62 0.08 20.68 0.09 23.98 0.10 27.53 0.12 31.32 0.13 35.36 0.15 39.64 0.17 44.16 0.19 48.94 0.22 59.21 0.24 64.72 0.27 70.47
m3 0.60 0.95 1.42 2.03 2.78 3.70 4.80 6.10 7.62 9.38 11.38 13.65 16.20 19.06 22.23 29.59 33.81 38.41
Square batch gal 158.55 251.77 375.82 535.10 734.03 976.99 1268.40 1612.65 2014.17 2477.34 3006.57 3606.27 4280.84 5034.68 5872.21 7815.91 8930.89 10147.17
L 600 953 1423 2026 2779 3698 4801 6105 7624 9378 11381 13651 16205 19058 22229 29586 33807 38411
Scale up ratio
Assume Volume
DT1 V1
= = =
H1 0.785* DT1 * H1 0.785* DT1
(original vessel is standard cylindrical )
Ratio of volume
V2
DT2
V1 Scale up ratio, R =
DT1 V2 V1 =
Using this ratio for all factors, ex Da2 J2 = = R Da1 R J1
Agitator Speed,
n=1 for equal liquid motion, 3/4 for equal suspension of solid, 2/3 for equal mass transfer
n=2/3, power per unit volume is constant n=1, tip speed is constant
For Mild agitation and blending For vigarous agitation For intense agitation
0.1 to 0.2 0.4 to 0.6
KW/m3 of fluid KW/m3 of fluid
(Mass transfer is importanr0
0.8 to 2
KW/m3 of fluid
Example
Agitator Type Dia of Tank Dia of agitator Height of the Tank Width No of Baffles Baffle width Speed Viscosity Density
Flat blade turbine agitator Dt1 1.83 m Da1 0.61 m H1 1.83 m W1 0.122 m 4 J1 0.15 m N1 90 rpm 10 CP 929 kg/m3
1.5 rps 0.01 Kg / m s
Scale up for 3 times larger for 1)Equal rates of mass transfer is required 2) Equal liquid motion is required
Solution -1
Original Volume Scale up volume Ratio Da2 For equal mass transfer N2
V1 V2 1.442 0.879772 n 1.175072
4.810862 m3 14.43259 m3
m = rps
0.667 70.504 rpm
Reynolds Number
Nre
84492.96
Np
Power required
3972.189
J/sec
3.97 KW
5.33
Solution -2
Original Volume Scale up volume Ratio Da2 For equal liquid motion N2
V1 V2 1.442 0.880 n 1.040042
4.810862 m3 14.43259 m3
m = rps
1 62.403
Reynolds Number
Nre
74783.72
Np
Power required
2754.162
J/sec
2.75 KW
3.70
ssel is standard cylindrical )
DT2
DT1
hp
hp
