Phase Locking Protocol (Cont.) The Two Phase Locking Protocol The Two
Two-phase fluid flow: Guideline to Pipe Sizing for Two-Phase (Liquid-Gas)
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Transcript of Two-phase fluid flow: Guideline to Pipe Sizing for Two-Phase (Liquid-Gas)
Two-phase fluid flowGUIDELINE TO PIPE SIZING FOR TWO-PHASE FLOW (LIQUID-GAS)
AUTHOR: VIKRAM SHARMADATE: 2nd MARCH 2017
Table of ContentsWhat is two-phase flow?Types of Gas-Liquid flowBaker’s map for gas-liquid flowCalculation methodologyReferences
What is two-phase flow?Single-phase flow → fluid flow in a single
stateMultiphase flow → simultaneous flow of
several fluid phasesCommon multiphase flow are (i) gas-liquid,
(ii) liquid-liquid or (iii) liquid-solid.Why is it so important? Severity of pressure
drop problems that may result to operational problems in a process
Types of Gas-Liquid flowBubble flow:Bubbles (gas) are dispersed throughout the
liquid & moves along the upper part of the pipe due to their buoyancy.
Velocity of the bubble of gas ≈ velocity of the liquid
Occurs when the gas content is 0.3 wt. frac. of the total volumetric flow & at high mass flow rates
Linear vel. of the liq. = 1.5-4.8 m/s (typical)Linear vel. 0f the vap. = 0.15-0.61m/s
(typical)
Types of Gas-Liquid flow (cont’d)Plug flow: Intermittent type two-phase flowAlternate plugs of liq. & gas where the gas
portion moves along the upper part of the pipe.
Liq. → along the bottom part of the pipeExpected to occur when liq phase is at 0.61
m/s and vapour phase is < 1.22 m/s
Types of Gas-Liquid flow (cont’d)Stratified flow:2 phases separated frm. by a common interfaceLiq phase stratified at the bottom of the piping due
to gravitySeen in horizontal & slightly inclined pipelines ↓ gas flow: smooth fluid interface or possible
rippling by small capillary waves of a few mm lengths
↑ gas flow: waves of small amplitude appears, droplets can be entrained, deposited at the wall or interface
Liq. vel < 0.15 m/s, gas vel: 0.15-3.05 m/s (typical)
Types of Gas-Liquid flow (cont’d)Wave flowSimilar to stratified flow, gas flow at ↑
velocity ↓ gas vel. – gas-liq. Interface is flatAs gas vel. increases – interface becomes
unstable due to small disturbances & waves are seen
Shape & size of waves α pipeline geometry & fluids flow rates
Types of Gas-Liquid flow (cont’d)Slug flowLiq. rich slugs - may or may not cover the
entire inner section of a pipeObserved when the rapidly moving gas
created waves & form froth slugsThis slugs travel along the pipeline @ vel.
Higher than ave. liq. Vel.Vibrations are due to ↑ vel. travelling against
fittingsLiq. vel ≈ 4.58 m/sGas vel.: 4.58-15.24 m/s
Types of Gas-Liquid flow (cont’d)Annular flowGas vel. further increases resulting to gas
flow through the liq. FlowLiq. Film @ the bottom of the pipe is thicker
due to gravityLiq vel. < 0.15 m/sGas vel. > 6.1 m/s
Types of Gas-Liquid flow (cont’d)Dispersed flowLiq. entrained as the fine droplets by the gas
phase in the gas-liq flowThe dispersed phase in both gas-liq. / liq.-liq.
- flow rates of both phases as the interface is deformable
The dispersed phase of the dispersed flow coalesces & become continuous phase with ↑ flow rate
Occur when the gas content is > 30% of the total weight flow rate
Baker’s map for two phase flowLiq. entrained as the fine droplets by the gas
phase in the gas-liq flow
Calculation procedureObtain physical properties of the fluid (mass
flowrate, density, viscosity and surface tension) for both gas and liquid.
Obtain piping layout. Piping is to be divided into segments as fluid regime and properties varies along the piping route
Determine the flow regime for 1st pipe segment
Perform ΔPfriction, ΔPelev. & ΔpfittingsRepeat the above calculations for other pipe
segments
Calculation procedure (cont’d)
Break the pipe into a couple of segments.For Segment 0-1, determine the fluid flow regime
by calculating Bx and By (refer to Slide #11). Intersection of Bx and By gives the fluid flow
regimeThe next step is to calculate the ΔP of individual
phase (ΔPL, bar/100m & ΔPG,bar/100m)
1 2 3 4 5 6 n
Fluid in
Fluid out
0
Calculation procedure (cont’d)The next step is to calculate the ΔP of individual
phase (ΔPL, bar/100m & ΔPG,bar/100m) (cont’d)
Darcy friction factor (fD) is expressed as:
fD can calculate for both laminar and turbulent flows
Calculation procedure (cont’d)Lockhart-Martinelli (LM) parameter, X is the
ratio of liquid and gas pressure drop. It is a function of mass fluxes, densities,
viscosities of the liq.. & gas and pipe diameter.
We have to determine the frictional pressure drop multipliers for both liq. (φ2
L) and gas (φ2G).
The multipliers are a factor of fluid Reynolds number (turbulent, laminar (viscous)).
Transitional flow is considered as TURBULENT.
Calculation procedure (cont’d) Transitional flow is considered as TURBULENT (cont’d)
φ2L decreases with increasing X, φ2
G increases with increasing X
Extracting data is cumbersome, may lead to inaccurate date.
Calculation procedure (cont’d)Extracting data is cumbersome, may lead to
inaccurate date (cont’d).Chisholm (1967) incorporated the effect of
interfacial shear forces in the LM correlation.New correlation ensures engineers to
determine the hydraulic diameters of the phases more accurately compared to LM.
It do not require the use of graph (refer to Slide #16)
Chisholm (1967) correlations in terms of Lockhart-Martinelli (1949):
Calculation procedure (cont’d)Chisholm (1967) correlations in terms of
Lockhart-Martinelli (1949) (cont’d)
The frictional pressure drop can be calculated based on either liquid phase or gas phase.
The next step is to calculate the ΔPstatic due to elevation
Calculation procedure (cont’d)The next step is to calculate the ΔPstatic due to
elevation (cont’d)We have to include pressure drop due top
fittings. We rely on equivalent length method to
determine the pressure drop.This method approximates the pressure drop
of fittings based on hypothetical piping length
Calculation procedure (cont’d)The next step is to calculate the ΔPstatic due to
elevation (cont’d)We have to include pressure drop due top
fittings. We rely on equivalent length method to
determine the pressure drop.This method approximates the pressure drop
of fittings based on hypothetical piping length
Calculation procedure (cont’d) This method approximates the pressure drop of
fittings based on hypothetical piping length (cont’d) Consider the effect of erosion-corrosion on piping. In certain flow regimes, liq vel approach or exceed
gas vel & this leads to erosion-corrosion Determine if erosion-corrosion may occur at a
particular velocity.
Total pressure drop is:
P1 of Segment 0-1 is obtained: ΔP0 – ΣPTP..
Calculation procedure (cont’d)P1 of Segment 0-1 is obtained: ΔP0 – ΣPTP..
(cont’d)The properties for Segment 1-2 is based on
Point 1. Repeat the above calculations to determine the total pressure drop of horizontal pipe straight length.
Do not segmentized pipe fittings! Choose your segments appropriately.
References Akiwi, S. (2010, September 7). Dispersed Flow. Retrieved
February 23, 2017, from THERMOPEDIA: A-to-Z Guide to Thermodynamics, Heat & Mass Transfer, and Fluids Engineering: http://www.thermopedia.com/content/5/
Alain, L., & Fabre, J. (2011, February 9). Stratified Gas-Liquid Flow. Retrieved February 21, 2017, from THERMOPEDIA: A-to-Z Guide to Thermodynamics, Heat & Mass Transfer, and Fluids Engineering: http://www.thermopedia.com/content/266/
Coker. (2007). Fluid Flow. In Applied Process Design for Chemicals and Petrochemical Plants (4th ed., Vol. 1, pp. 133-302). Burlington: Elsevier Inc.
Hewitt, G. F., & Taylor-Hall, N. S. (2013). Flow regimes in horizontal and inclined flow. In Annular Two-Phase Flow (p. 7). Oxford: Elsevier.
McCready, M. J. (n.d.). Flow regimes in gas-liquid flows. Retrieved February 22, 2017, from https://www3.nd.edu/~mjm/flow.regimes.html
References Mekisso, H. M. (2004). Comparison of Frictional Pressure Drop
Correlations for Isothermal Two-Phase Horizontal Flow. Stillwater: Oklahoma State University.
Sreenivas, J. (2011, February 11). Wavy Flow. Retrieved February 21, 2017, from THERMOPEDIA: A-to-Z Guide to Thermodynamics, Heat & Mass Transfer, and Fluids Engineering: http://www.thermopedia.com/content/269/
Szilas, A. P. (1975). Selected topics in flow mechanics. In Production and Transport of Oil and Gas (p. 54). New York: Elsevier.
Thermal-FluidsCentral. (2010, July 9). Frictional pressure drop correlations based on the separated flow model. Retrieved March 1, 2017, from http://www.thermalfluidscentral.org/encyclopedia/index.php/Frictional_pressure_drop_correlations_based_on_the_separated_flow_model
Thome, J. R. (n.d.). 1: Two-Phase Flow Patterns and Flow Pattern Maps Chapter 12 (in Databook III) [Lecture Notes]. Retrieved February 14, 2017, from Two-Phase Flows and Heat Transfer: http://ltcm.epfl.ch/files/content/sites/ltcm/files/shared/import/migration/COURSES/TwoPhaseFlowsAndHeatTransfer/lectures/Chapter_12.pdf