Computational Fluid Dynamic (CFD) Analysis of Gas and Liquid Flow Through a Modular Sample System

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2 Computational Fluid Dynamic (CFD) Analysis of Gas and Liquid Flow Through a Modular Sample System Tony Y. Bougebrayel, PE, PhD John J. Wawrowski Swagelok Solon, Ohio IFPAC 2003 Scottsdale, Az January 21-24, 2003

3 Agenda Objective Cv, K Factor CFD Background MPC - CFD Model Description, Procedure Results Conclusions

4 Objectives Evaluate the flow capacity (Cv) for a threeposition Swagelok MPC substrate flow component Investigate the effects of using different surfacemount components on the total system Cv Determine an analytical method for predicting the total system Cv Investigate the effect of the fluid type on the pressure drop through a substrate flow component Determine the pressure required to flow a liquid sample through a Swagelok MPC system

5 Cv and K Factors The Cv Approach The K Approach What causes Cv and K and how are they determined? How do they relate to the MPC?

6 The Cv Approach Cv: Flow capacity (component) For Newtonian Liquids: Through control components: q = N 1 *F p * C v * ( p /G f ) 1/2 (ISA 75.01) Through straight pipes: p = f L ρ Q 2 / d 5 For Gases: Through control components: q = N 7 *F p * C v * p 1 * Y * [x / (G g T 1 Z)] 1/2 (ISA 75.01) (Darcy s) For Low pressure drop: 1.0 < Y < 2/3, (p 1 < 2p 2 ) and Y = 1 x / (3F k x t ) For high pressure flow (choked flow, p 1 >2p 2 ): Y= 2/3, x t =.5 and q = N 7 *F p * C v * p 1 *.471*[1 / T 1 Z)] 1/2 Swagelok Company, 2002

7 The K Approach K-Factor: Resistance to flow (system) Head loss through a pipe, valve, or fitting: h L = K v 2 / 2g where: K = f L / D (Darcy s) Bernoulli s equation (mechanical energy): z p 1 /ρ 1 + v 12 /2g = z p 2 /ρ 2 + v 22 /2g + h L Potential Pressure Kinetic Total Energy Energy Energy Head Loss

8 The Make-up of Cv and K Changes in the flow direction (turns) Changes in the geometry (expansion, contraction, flow obstacles) Geometry size Weight of the fluid (density effects) Velocity of approach (entry and exit velocity) Friction between the fluid and solid as well as within the fluid layers (viscosity effects) Elevation (1psi is about 27.8 inches of water head)

9 The Make-up of Cv and K Order of Importance 1. Transition: A sharp 90-degree turn costs the flow more energy (pressure) than the frictional losses or pipe reduction losses (i.e. losses due to a short 90 deg. turn are four times greater than losses due to a half size reduction in the pipe diameter) 2. Pipe Size: Pipe size reduction has a 5-power effect on the flow where the frictional losses are at 1 st order 3. Friction: The frictional losses are of greater relative importance in smaller components (frictional losses decrease with the increase in flow velocity or pipe diameter)

10 How are Cv and K determined? Testing (ISA 75.02) Empirical values (macroscopic approach) CFD (microscopic approach)

11 Computational Fluid Dynamics Background CFD History How it works Swagelok s Effort

12 CFD History Scientific community (space research and power production) Current Status and Applications Challenges

13 How Does CFD Work? Geometry Mesh Boundary Conditions Solution Method Post Processing

14 Geometry Swagelok Company, 2002

15 Geometry Swagelok Company, 2002

16 Mesh External Volume Swagelok Company, 2002

17 Mesh Internal Volume Swagelok Company, 2002

18 Boundary Conditions Mass Flow Rate Pressure Velocity Inlet-Vent Inlet-fan

19 Solution Method Coupled/Segregated Laminar/Turbulent K-ε, RSM, k-ϕ, LES, Compressible/Incompressible Steady State/Transient Set the Boundary Conditions Initialize the Solution Solve

20 Post Processing Swagelok Company, 2002

21 Post Processing Swagelok Company, 2002

22 Post Processing Swagelok Company, 2002

23 Swagelok s Effort Swagelok gained in-house CFD capabilities in 1997 The majority of applications revolve around finding/optimizing Cv and Heat transfer analysis Swagelok tool box: Fluent, Floworks, and Pipeflow

24 MPC CFD Model Swagelok Company, 2002

25 MPC - CFD Model Model: Turbulent, Steady State, Segregated, Implicit Geometry: 3D with symmetry about the center plane Viscous Model: Standard k-ε turbulence model Medium: Water, Air and some Hydrocarbons Boundary Conditions: Inlet: Mass Flow Rate (300 ml/min) Outlet: Atmospheric pressure Mesh: Hybrid, 120k order Convergence Criteria: Conservation of mass, Y +

26 Results Cv of a three-position system

27 Results Predicted Cv: Tested Cv: Flow Direction

28 Results Cv changes based on surface-mount components

29 Results Total system Cv: 1/Cv total 2 = Σ (1/Cv i ) 2 Cv1 Cv2 Cv3 Cv4 Cv5 Cv6 Cv7 Flow Direction

30 Results - Effects of fluid type on required driving pressure For liquids with similar kinematic viscosities (υ = µ/ρ): P fluid / P water = (1/SG fluid ) x (mass flow rate of fluid/mass flow rate of water) 2 For liquids with different kinematic viscosity (i.e. motor oil): P fluid / P water = (υ fluid / υ water ).5 Viscosity vs. Pressure Drop Correlation Benzene Water Ethylene-Glycol (C2H6O2) Ethyl Alcohol (C2H5OH) Delta P total Kinematic Viscosity Water Ethylene-Glycol (C2H6O2) Ethyl Alcohol (C2H5OH) Benzene

31 Results Pressure drop on 3 position assembly Media Density (kg/m 3 ) Kinematic Viscosity (m 2 /s) P (psi) Air x Ethyl Alcohol x Benzene x Ethylene-Glycol 1, x Swagelok Company, 2002

32 Results Pressure Required to drive 300 ml/min through Swagelok's MPC (3-position assembly) 30 Total Presssure Required, psig Benzene Water Ethylene-Glycol (C2H6O2) Ethyl Alcohol (C2H5OH) Air

33 Conclusions A valid model for predicting flow capacity of a Swagelok MPC system The surface-mount component has the largest effect on total system Cv Developed a valid equation for predicting pressure to drive liquids Based on kinematic viscosity MPC requires minimal driving pressure Visit Swagelok at Booth 51

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