The Devil is in the Details : Understanding the impact of your design selection on the flow behavior in a Modular Liquid Sampling System

Transcription

1 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 1

2 Agenda Modular Sampling System Design Parameters Flow Capacity Definition and Modeling Cleanliness Study Residence Time Conclusions 2

3 Design Parameters Modular Sampling System 3

4 Flow Capacity Definition & Makeup # of GPM/1 psid (std. cond.) Cv=Q/ P (Resistance-k: C v = 29.9 d 2 / k 1/2 ) Modes of pressure loss Small Cv is not bad. Large internal volume with a small Cv is Bad! 4

5 Flow Capacity System Cv System Cv ΔP total = ΔP i 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 Components perform differently once in the system If need to test with gas decrease the Cv by 5-10% 5

6 Flow Capacity Case Study Conventional Test Assembly 6

7 Flow Capacity Case Study Outlet Inlet 7 Intraflow Test Assembly

8 Flow Capacity Prediction Methods Intraflow 3D CAD Model 8

9 Flow Capacity Prediction Methods Simplified CAD Model 9

10 Flow Capacity Prediction Methods Internal Fluid Volume 10

11 Flow Capacity Prediction Methods Mesh the volume Solve the Flow equations CFD Analysis 11

12 Flow Capacity Results Cv Modular System Conventional Prediction.110 (CFD) (Crane 410) Tested 0.106* 0.114* About 0.75 psid is required to push 300 cc/min of water through! 12 * Preliminary test data. Subject to final verification.

13 Cleanliness Study System Fluid 13

14 Cleanliness Study Clean-In-Place 14

15 Cleanliness Study Design Comparison CFD Investigation of 5 likely cases for areas of entrapment ANSYS CFX cc/min) 1/8 Dead leg Weld Crevice Parker's Modular Taper 1/4 Dead leg Weld Expansion 15

16 Cleanliness Study 1/8 Dead leg 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 16

17 Cleanliness Study ¼ Dead leg Flow has a hard time sustaining the momentum to reach deep into the leg 17

18 Cleanliness Study Weld Crevice 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 18

19 Cleanliness Study Weld Expansion Flow s velocity slows down once it expands into the larger volume by (d/d)^2 The steps cause pressure loss 19

20 Cleanliness Study Weld Expansion The lowered velocity produces lower Wall Shear 20

21 Cleanliness Study Parker s Modular Taper It s the fluid volume between the substrate and the connector 21

22 Cleanliness Study Parker s Modular Taper The tapered side is creating room for the flow to circulate and is also guiding it deeper into the crevice 22 Stronger Wall Shear on the incident wall

23 Cleanliness Study Design Comparison Wall Shear Plotted to same scale! 23

24 Cleanliness Study Design Comparison 24

25 Cleanliness Study Case Study Moisture Challenge Test Intraflow Conventional Moisture (ppmv) Time (min.) 25

26 Residence Time Challenges Directly tied to Cleanliness hampered by the same challenges Residence Time through a 1/8 straight conduit is 4x less than through a ¼ conduit Prediction 26

27 Residence Time Design Comparison for dead legs Time:.092 sec Asymmetric residence time at Outlet Time:.099 sec 27

28 Residence Time Design Comparison for weld crevice Slow flow caused by the crevice takes the longest time Sticks around the wall Time:.067 sec 28

29 Residence Time Design Comparison for weld expansion Time:.123 sec Large & Slow area of Recirculation A large volume of slow flow 29

30 Residence Time Design Comparison for modular taper Slower flow in the crevice Time:.071 sec 30

31 Residence Time Design Comparison Geometry Time, sec. Weld Crevice.067 Weld Expansion.123 Dead Leg_ Dead Leg_ Modular Taper.071 Modular Taper w/swirl.076 How big is the refuge volume and how hard are you flushing it! 31

32 Residence Time Effects of Cv Geometry Time, sec. Cv Weld Crevice Weld Expansion Dead Leg_ Dead Leg_ Modular Taper Modular Taper w/swirl Similar Cv doesn t necessarily translate into similar residence time!

33 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! 33

34 Thank You. 34