TUSTP 2003 By Ciro A. Pérez May, 2003 DOE Project: HORIZONTAL PIPE SEPARATOR (HPS © )

TUSTP 2003TUSTP 2003

ByBy

Ciro A. PérezCiro A. Pérez

May, 2003May, 2003

DOE Project:DOE Project:

HORIZONTAL PIPE SEPARATOR HORIZONTAL PIPE SEPARATOR (HPS(HPS©©))

Objectives

Physical phenomena in HPS

Modeling approach

Experimental program

Conclusions - Future work

TopicsTopics

Study the behavior of oil-water mixtures in horizontal pipes

Develop a mechanistic model that predicts separation efficiency for given fluids, geometry and flow rates

Compare/refine model with data obtained in this study and from literature

Study effects of using manifolds to install multiple separators in parallel

ObjectivesObjectives

Objectives


Modeling approach


Conclusions - Future Work

TopicsTopics

Zone 1 Zone 2

Zone 3

Zone 4

Oil

Oil with Water droplets

Packed water droplets in oilPacked oil droplets in water

Water with Oil droplets

Water

Physical phenomena in HPSPhysical phenomena in HPS

Inlet Direction of flow Outlets

Oil-Water mixture enters HPS, with droplet distribution function of processes upstream. Some mixing can occur at inlet (Zone 1)

Inside HPS the velocity decreases, turbulence decreases (laminar flow might be reached), settling and coalescence are promoted (Zone 2), layers begin to develop

Up to 6 layers can develop (Zone 3):- Pure Oil- Oil with water droplets- Packed water droplets in oil- Packed oil droplets in water- Water with oil droplets- Pure water

Eventually steady state is reached (Zone 4)


Regimes of operation in HPS

Laminar flow is desirable as it promotes segregation Oil is more likely to flow to be in laminar flow

conditions due to higher viscosity So, desirable flow regimes are:

- Laminar Oil Flow - Laminar Water Flow- Laminar Oil Flow - Turbulent Water Flow

Study flow in HPS requires:- Steady state conditions: max segregation- Transient conditions: how long it will take


Objectives


Modeling approach



TopicsTopics

Previous studies

Proposed model

Modeling approachModeling approach

Previous studies

a. 1D Mechanistic approach: Barnea-Brauner (1991)b. 2D Analytical approach (for laminar flows): Brauner

(1998)c. Numerical approach

- Shoham-Taitel (1984, gas-liquid)- Elseth et al. (2000, VOF method)- Gao et al. (2003, VOF method)

1D mechanistic approach leads to simple solutions, so it will be used as an initial approach


Proposed model:

1- 1D stratified flow pattern model is applied for given fluids and flow rates. If flow is stable, flow characteristics are given by the model

2- If flow is unstable, following procedure applies:- An amount of more viscous phase is assumed to flow to the less viscous

phase- For this new flow rate, properties are calculated for mixture, segregated flow is

assumed, and stability is checked. Migration stops when stability is reached- No convergence means non segregated flow


Preliminary resultsModel tested against experimental data (Shi et. Al (2000)) Test conditions:

- Oil properties: 3 cp, 800 kg/m3

- Water properties: 1 cp, 1100 kg/m3

- Pipe: 0.1 m ID, 18m long- Mixture velocity: 0.4 to 3 m/s- Water Cut: 0.2, 0.4, 0.6, 0.8

Trallero (1995) model used, Sheltering Factor assumed 0 Increased interfacial friction factor as mixing and waves form at the interface


Results: Pure oil and water layer thickness


40% WC

00.10.20.30.40.50.60.70.80.9

1

0 0.5 1 1.5

Mixture Velocity m/s

hl/D

Experimental Oil-Mix level

Experimental Mix-Water Layer

Model Oil-Mix layer

Model Mix-WaterLayer

60% WC

00.10.20.30.40.50.60.70.80.9

1

0 0.5 1 1.5

Mixture velocity m/s

hl/D

Experimental Oil-Mix level

Experimental Mix-Water layer

Model Oil-MixLayer

Model Mix-WaterLayer

Objectives


Modeling approach



TopicsTopics

Test SectionTest Section

Experimental programExperimental program

Calibration:

Level: Pipe centerline was leveled in +-3/32” range from the horizontal

Level sensors: For operating conditions, level meters are able to detect continuous interface with error of 3/32”


Sensor 2 signal function of dimensionless height

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1 2 3 4 5

Voltage

hl/

D

Test 1Test 2Test 3Test 4Top of sensorBottom of sensor

Typical level meter signal at interface


Sensor stem gap:

7/32”

Pitot / Isokinetic sampling probe

Previous works: - Khor, Mendes-Tatsis and Hewitt (1996)- Vedapuri, Bessette and Jepson (1997)- Shi, Cai and Jepson (1999)- Cai, Gopal and Jepson (2000)



Characteristics - ID= 3/16”- OD= 11/32”- Operating dP: 0 to 1” H2O, accuracy dP 0.15%

- Range of operation:

. Min. velocity: 0.06 m/s (error 10% )

. Max. velocity : 0.7 m/s (error 0.073% )


Photo of assembled probe:

BaseBase

PitotPitot

Pressure outletsPressure outlets

Sampling outletSampling outlet


Pitot / Isokinetic sampling probe in place



- Calibration results for single phase


150 lbs/min oil

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0 0.5 1 1.5

Distance from centerline (inches)

Vel

ocity

(m

/s)

1.71875

1.46875

1.21875

0.96875

0.71875

0.46875

0.21875

0.03125

Theoretical

Distance from wall 200 lbs/min water

0

0.05

0.1

0.15

0.2

0.25

0.3

0 0.5 1 1.5

Distance from centerline (inches)

Vel

ocity

(m

/s)

1.75

1.5

1.25

1

0.75

0.5

0.25

0

Theoretical

Distance from wall

Pitot / Isokinetic sampling probe- Problems when measuring oil-water flow. After flushing

with oil, water floods pitot, capillarity causes oscillations in dP while flooding

- Improved with wider pressure taps. dP values to be taken at initial plateau, before flooding occurs.


Signal from dP, at 0.75" from bottom

0

1

2

3

4

5

6

0 20 40 60 80

Time (1/2 sec)

Vol

tage Test 3

Test 2Test 1

PlateauPlateau FloodingFlooding

Calibration results: Effects of oil-water flow Pitot filled with oil, mixture flowing Vsl=0.6 m/s, WC 60%


Velocity Profile: Vmix=0.6 m/s, WC 60%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.2 0.4 0.6 0.8 1

Velocity (m/s)

hl/D Velocity Profile

Objectives

Physical Phenomena in HPS

Modeling approach


Conclusions/ Future Work

TopicsTopics

Initial model for all flow conditions is proposed. Actual model underpredicts thickness of pure fluid zones

Model requires higher interfacial shear stress when mixing layers are present

Pitot measurements for low velocities are affected by capillarity in pitot pressure taps Measurement criterion was adapted for this condition

Conclusions/Future WorkConclusions/Future Work

Measurement of velocity profiles for experimental matrix

Measurement of hold up for experimental matrix Hold up/Interfacial friction factor adjustment with

experimental data and literature data

Future workFuture work

Questions?

HORIZONTAL PIPE SEPARATOR HORIZONTAL PIPE SEPARATOR (HPS(HPS©)©)

Documents

TUSTP 2003 By Ciro A. Pérez May, 2003 DOE Project: HORIZONTAL PIPE SEPARATOR (HPS © )