Sampling System Design

©2009 Parker Hannifin CorporationAll Rights Reserved

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“The Devil is in the Details”: Understanding the impact of your design selection on the flow

behavior in a Modular Liquid Sampling System”

Tony Bougebrayel, P.E., PhD.Parker Hannifin


Agenda

Modular Sampling System Design Parameters

Flow Capacity Definition and Modeling

Cleanliness Study

Residence Time

Conclusions

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Design Parameters Modular Sampling System

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Flow Capacity Definition & Makeup

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Small Cv is not bad. Large internal volume with a small Cv is Bad!

# of GPM/1 psid (std. cond.) Cv=Q/√∆P (Resistance-k: Cv = 29.9 d2 / k1/2 )

Modes of pressure loss


Flow Capacity System Cv

A system Cv can never exceed the lowest component Cv in the system

Although an elbow geometry is fixed, its effect is altered once mounted in a non-planar way

Manufacturers can not test all possible configurations. Some engineering judgment is required by the design engineer

Prediction methods: CFD, Testing, Supplier

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If need to test with gas decrease the Cv by 5-10%

System Cv ΔPtotal = ∑ ΔPi

Components perform differently once in the system


Flow Capacity Case Study

Conventional Test Assembly6


Flow Capacity Case Study

Intraflow Test Assembly7

Inlet

Outlet


Flow Capacity Prediction Methods

Intraflow 3D CAD Model

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Simplified CAD Model

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Internal Fluid Volume

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Mesh the volume

Solve the Flow equations

CFD Analysis


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Cv Modular System Conventional

Prediction.110(CFD)

0.124(Crane 410)

Tested 0.106* 0.114*

Flow Capacity Results

About 0.75 psid is required to push 300 cc/min of water through!

* Preliminary test data. Subject to final verification.


Cleanliness Study System Fluid

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Cleanliness Study Clean-In-Place

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Cleanliness Study Design Comparison

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CFD Investigation of 5 likely cases for areas of entrapment

1/8” Dead leg

1/4” Dead leg

Weld Crevice

Weld ExpansionParker's Modular Taper

ANSYS CFX 11.0 (water @ 300 cc/min)


Cleanliness Study 1/8” Dead leg

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Full recirculation

Flow has enough momentum to reach the bottom

Wall Shear indicates the intensity of the cleaning action on the surface

Good cleaning action on bottom and front side

Weak flow on back-facing wall


Cleanliness Study ¼” Dead leg

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Flow has a hard time sustaining the momentum to reach deep into the leg


Cleanliness Study Weld Crevice

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Flow hits the wall and turns down but Not much room for strong recirculation

Strong Wall Shear on incident wall & Lower Wall Shear on other surfaces


Cleanliness Study Weld Expansion

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Flow’s velocity slows down once it expands into the larger volume by (d/D)^2

The steps cause pressure loss


Cleanliness Study Weld Expansion

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The lowered velocity produces lower Wall Shear


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Cleanliness Study Parker’s Modular Taper

It’s the fluid volume between the substrate and the connector


Cleanliness Study Parker’s Modular Taper

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The tapered side is creating room for the flow to circulate and is also guiding it deeper into the crevice

Stronger Wall Shear on the incident wall


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Wall Shear – Plotted to same scale!



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Cleanliness Study Case Study

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10

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30

40

50

60

0 0.45 1 1.5 2 2.5 3 3.5 4 4.5

Moi

stur

e (p

pmv)

Time (min.)

Moisture Challenge TestIntraflow Conventional


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Directly tied to Cleanliness – hampered by the same challenges

Prediction

Residence Time Challenges

Residence Time through a 1/8” straight conduit is 4x less than through a ¼” conduit


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Asymmetric residence time at Outlet

Time: .092 sec Time: .099 sec

Residence Time Design Comparison for dead legs


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Time: .067 sec

Residence Time Design Comparison for weld crevice

Slow flow caused by the crevice takes the longest time

Sticks around the wall


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Residence Time Design Comparison for weld expansion

Time: .123 sec

Large & Slow area of Recirculation

A large volume of slow flow


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Residence Time Design Comparison for modular taper

Slower flow in the crevice

Time: .071 sec


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Geometry Time, sec.

Weld Crevice .067

Weld Expansion .123

Dead‐Leg_125 .092

Dead‐Leg_250 .099

Modular Taper .071

Modular Taper w/Swirl .076

Residence Time Design Comparison

How big is the refuge volume and how hard are you flushing it!


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Geometry Time, sec. Cv

Weld Crevice .067 .663

Weld Expansion .123 .417

Dead‐Leg_125 .092 .631

Dead‐Leg_250 .099 .620

Modular Taper .071 .649

Modular Taper w/Swirl .076 .488

Similar Cv doesn’t necessarily translate into similar residence time!

Residence Time Effects of Cv


Conclusions

The pressure required to drive liquids through modular components is reasonable

For a fluid volume to be stagnant it would have to be quite removed from the main flow stream

Large and Slow recirculation take a long time to clear the system

Many variables come into the system and affect its performance

Treacherous pathways are costly!

Published Cv values are not final!

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Thank You.

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Documents

Sampling System Design