How to Select a Static Mixer

Static Mixers are easily sized using available formulas and pressure drop charts. Your initial selection can be made by following the guidelines listed below. To fine tune your selection contact our application engineering staff.

(1) Determine the mixer type using the Motionless Table:

Type of Flow # of LPD # of ISG Elements
Turbulent
2 - 6
4
Laminar
Viscosity Ratio = 0.1 to 1,000
24
10
Viscosity Ratio = 1,000 to 10,000
36
14
Viscosity Ratio = 10,000 to 100,000
48
20

*Viscosity Ratio = µp/µm
(viscosity of primary stream p / viscosity of minor stream m)

(3) Estimate Pressure Drop

1. Compute the Reynolds Number:

 NRe  = 6.31w = 3,161 Q * sg µD µD

NRe = Reynolds number dimensionless
D = Inside diameter of mixer housing, inches
Q = Volumetric flow rate, gallons/minute
w = Mass flow rate, pounds/hour
sg = Specific gravity
µ = Absolute viscosity, centipoise

2.

If NRe < 500 the flow is laminar. Use either Fig.1 for LPD or Fig.3 for ISG mixers to estimate the pressure drop per element. If NRe > 500, the flow is turbulent. The pressure drop per element is estimated from Fig.2 for LPD or Fig.4 for ISG mixers.

3. Multipy the pressure drop per element by the total number of elements to obtain the estimated pressure drop through the mixer.

4.

The estimated pressure drop must be corrected for physical properties as follows:

• For turbulent flow, multiply the estimated pressure drop by the specific gravity and the correction factor K from the table below to obtain the actual pressure drop.
Viscosity, cps.
K
10
1.1
100
1.3
1000
1.5
5000
1.6
• For laminar flow, the pressure drop is proportional to the viscosity. Since Fig.1 and Fig.3 are based on a fluid having a viscosity of 10,000 cps, the actual pressure drop is calculated as follows:
 Actual Pressure Drop = viscosity in cps x est. pressure drop 10,000
5. To determine LLPD pressure drop, multiply LPD pressure drop by 0.46 (if turbulent). In laminar flow, the LPD and LLPD have similar pressure drop.

6.

If actual pressure drop exceeds the allowable value, repeat above steps using a larger mixer diameter.
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