Flashing liquid jets and two-phase droplet dispersion I...

Flashing liquid jets and two-phase droplet dispersion

I. Overview and model implementation/validation

MKOPSC International Symposium, 27-28 October 2008College Station, TEXAS

Henk W.M. Witlox, Mike Harper and Adeyemi Oke, DNV Software, UKPeter Kay and Phil Bowen, Cardiff University, UK

©

Det Norske Veritas AS. All rights reserved Slide 203 December 2009

Flashing liquid jets and two-phase droplet dispersion

Introduction

Scaled experiments and droplet size correlation development (Cardiff)

Large-scale experiments (INERIS)

Model development and model validation (DNV Software)-

discharge modelling-

dispersion modelling

Conclusions and future work

©


Droplet evaporation and distributed rainout

SMD droplet trajectory

(flashing) two-phase discharge from

pipe/vessel

vapour-plume centre-line

Distributed rainout; spreading evaporating liquid pool

UDMDISC/ATEX

©


Discharge and atmospheric expansion (flashing)

L

Flow

Expansion Zone

Leak Orifice

Atmosphere

Vessel (stagnation)

©


DNV Droplet Modelling Joint Industry Project

(2001) Phase I: literature review

(2003-2005) Phase II-

Scaled water experiments (Cardiff University)-

Improved droplet-size correlations; validation flow rate and initial droplet size

(2006-2008) Phase III-

Sponsors: DNV, Gaz

de France, RIVM, TOTAL, Hydro and Statoil -

Experiments-

scaled experiments (Cardiff): water, cyclohexane, butane, propane, gasoline-

large-scale experiments (INERIS): butane experiments-

Modelling including validation-

flow rate and refined droplet correlations-

improved link pool/cloud and distributed rainout

©

Det

Norske Veritas

AS. All rights reserved Slide 603 December 2009

Phase III -

Scaled experiments (Cardiff)

Orifice diameter <

2 mm, pressure < 12 bar

Measurements-

Discharge and expansion zone characterisation-

Droplet size distribution with range of superheats

Chemicals-

Water (low volatily, boiling point 100oC)-

cyclohexane

(low volatility, boiling point 81oC) -

butane (medium volatility, boiling point 0oC)-

commercial propane (high volatility, boiling point ≈

-42oC)-

gasoline (low volatility; multi-component)

Refined initial droplet-size correlations as function of superheat-

Sauter

Mean Diameter (SMD)-

Droplet-size distribution

©

Det

Norske Veritas


Phase III -

Large-scale experiments (INERIS)

T°C (gradian 5th)

T°Cbuse

Pbuse

PVessel

Nitrogen

T°Csurface

Weighting device

Vpre

Vrej

©

Det

Norske Veritas


Phase III -

Large-scale butane experiments (INERIS)

Six experiments with butane (99.5%) jets with variation of orifice diameter, release pressure and superheat:

Measurements: -

ambient: wind speed/direction, temperature, humidity, pressure-

tank: weight, pressure, temperature as function of time-

orifice: pressure, temperature as function of time-

droplet size distribution and droplet speed measurements with “appropriate”

downwind distance and range of crosswind distances (0,+3, +6cm)

number of

experiment

orifice diameter

(mm)

release pressure (barg)

release temperature (C)

PDA axial distances (cm)

PDA resolution dmax (μm)

1 5 6 15-26 60 700 2 10 6 26-27 60,85 800 3 10 10 19-22 60,85 800 4 15 6 17-21 60,85 750 5 10 6 9-10 40,60,85 750 6 10 2 7-9 40,60,85 750

©

Det

Norske Veritas


Large scale butane experiments -

droplet-size distribution

(experiment 2, 10 mm orifice, 6 barg, 26.8oC)

diam : 10mm - pressure : 7 abs bar - Tliquid : 31°C - T release : 26,8°C - time : 34s after opening

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

10 110 210 310 410 510 610 710 810 910 ouplus...

diameter class (µm)

% c

umul

ated

% droplet% volum

SMD : 247 µm

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Det

Norske Veritas


Phase III –

Discharge model implementation/validation

Verification and validation -

flow rate-

Literature review-

Validation non-JIP experiments: water, propane, butane (typically within 20%)-

Validation Phase III experiments (also typically within 20%)

Implementation of droplet size correlations-

SMD -

Droplet size distribution

Validation –

droplet size-

Scaled and large-scale JIP Phase III experiments-

Other experiments from literature

©

Det

Norske Veritas


Discharge model verification and validation

Verification-

Analytical flow-rate equations -

incompressible liquid (Bernoulli)-

ideal gas (choked and un-choked)-

Process simulator (PROII)

Validation-

Subcooled

and saturated water jets -

Sozzi

and Sutherland (varying pipe length)

-

Uchida and Narai

(varying pipe length and stagnation pressure)

-

Hydrocarbon releases-

Full-bore and orifice releases of liquid propane (Shell)-

Orifice releases of butane (Shell)-

Long pipe -

validation against Isle of Grain (full-bore and partial leaks –

LPG)

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Det

Norske Veritas


Discharge model validation for sub-cooled water release

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 0.5 1 1.5 2 2.5

Pipe length (m)

Rat

io o

f pre

dict

ed to

obs

erve

d flo

wra

te (-

)

PHAST6.53-Sozzi&Sutherland

PHAST6.53-Uchida&Narai

©

Det

Norske Veritas


JIP Phase III droplet size correlation

Sub -cooled

Degree of superheat

SMD

0

Fully flashed (80 microns)

Transition

A

B

Superheated

Cutoff (10 microns)

Mechanical Break-up Fully Flashing

Phase III model based on the Phase II model with the following major changes:-

New correlation for mechanical break-up SMD (including fluid property ratios)-

Slight modification of regime transition criteria-

New SMD for fully flashed condition

©


SMD validation

Experiments-

Phase III experiments-

Cardiff: water, cyclohexane, gasoline, butane, propane-

INERIS: butane-

Other experiments-

Water: Cardiff Phase II JIP and Ecole de Mines-

Propane: STEP and HSL -

Butane: INERIS-

R134-A: VKI

SMD correlations-

Yellow Book: modified Weber correlation-

Melhem: generalised Weber criterion in terms of expansion energy-

CCPS: SMD = minimum {Weber mechanical break-up, CCPS flashing break-up} (old Phast)

-

JIP Phase II (now superseded by JIP Phase III)

-

JIP Phase III (new Phast 6.6)

©


SMD JIP II/III predictions (Cardiff water experiments)

too close PDA distance; scatter because of transient capture

0

200

400

600

800

1000

1200

1400

1600

-20 -10 0 10 20 30 40 50Superheat (K)

SM

D [m

icro

ns]

DISC (JIP-II, 0.75 mm)Experimental data (0.75 mm)DISC (JIP-III, 0.75 mm)

0

200

400

600

800

1000

1200

1400

-60 -40 -20 0 20 40 60Superheat (K)

SM

D [m

icro

ns]

DISC (JIP-II, 1 mm)Experimental data (1 mm)DISC (JIP-III, 1 mm)

0.75mm,10barg, L/d=3.54

1mm, 10barg, L/d=4.5

(black data points based on less accurate transient data capture)

©


SMD JIP II/III predictions (Cardiff cyclohexane)

0

200

400

600

800

1000

-80 -60 -40 -20 0 20 40 60Superheat (K)

SM

D [m

icro

ns]

DISC (JIP-II, 1 mm)Experimental data (1 mm)DISC (JIP-III, 1 mm)Experimental (Mechanical Break Up)

0

200

400

600

800

1000

1200

-80 -60 -40 -20 0 20 40 60 80Superheat (K)

SM

D [m

icro

ns]

DISC (JIP-III, 1 mm)MeasurementExperimental (Mechanical Break-up)

0

200

400

600

800

1000

1200

1400

-80 -60 -40 -20 0 20 40 60 80Superheat (K)

SMD

[mic

rons

]

DISC (JIP-III, 2 mm)MeasurementExperimental (Mechanical Break-up)

1mm,7.5barg, L/d=1.01

1mm,12barg, L/d=1.01

2mm,12barg, L/d=0.505

(black data points based on less accurate transient data capture;green data point based on more accurate steady-state data capture)

©


SMD JIP III predictions (Cardiff butane and propane)

Butane-

0.75mm, 10barg,L/d=1.4-

1mm, 8barg, L/d=1-

2mm, 7barg, L/d=0.5

Propane-

1 mm, 6barg, L/d=1.01-

2 mm, 7barg, L/d=0.5

0

50

100

150

200

250

300

350

400

450

500

-80 -60 -40 -20 0 20 40 60 80 100Nozzle Superheat Temperature (K)

SM

D [m

icro

ns]

DISC (JIP-III, 0.75 mm)Experiment (0.75 mm, 10 barg)DISC (JIP-III, 1 mm)Experiment (1 mm, 8 barg)DISC (JIP-III, 2 mm)Experiment (2 mm, 7 barg)

0

100

200

300

400

500

600

-80 -60 -40 -20 0 20 40 60 80Nozzle Superheat Temperature (K)

SM

D [m

icro

ns]

DISC (JIP-III, 2 mm)Experiment (2 mm, 7 barg)DISC (JIP-III, 1 mm)Experiment (1 mm, 6 barg)

(experimental data points based on accurate steady-state data capture)

©


SMD JIP II/III predictions (INERIS experiments)

15 mm, 5 barg (JIP II/III predictions)

5&10mm, 6barg (JIP III predictions)

10mm, 6&10barg (JIP III predictions)

0.E+00

2.E-04

4.E-04

6.E-04

8.E-04

1.E-03

1.E-03

-25 -15 -5 5 15 25 35 45 55Superheat (K)

Dro

plet

dia

met

er (m

)

INERIS_4_JIP-II (15mm, 5barg)

Exp.4: 15mm, 5barg (60cm)


INERIS_4_JIP-III (15mm, 5barg)

0.E+00

1.E-04

2.E-04

3.E-04

4.E-04

5.E-04

6.E-04

7.E-04

8.E-04

-25 -15 -5 5 15 25 35 45 55 65Superheat (K)

Dro

plet

dia

met

er (m

)


Exp.2&5: 10mm, 5.8barg (40cm)

Exp.2&5: 10mm, 5.8barg (60cm)

Exp.2&5: 10mm, 5.8barg (85cm)

INERIS1_JIP-III (5mm, 6barg)

INERIS_2&5_JIP-III (10mm, 5.8barg)

0.E+00

1.E-04

2.E-04

3.E-04

4.E-04

5.E-04

6.E-04

7.E-04

8.E-04

-25 -15 -5 5 15 25 35 45 55 65

Superheat (K)

Dro

plet

dia

met

er (m

)

Exp.2&5: 10mm, 5.8barg (40cm)

Exp.2&5: 10mm, 5.8barg (60cm)

Exp.2&5: 10mm, 5.8barg (85cm)

Exp.3: 10mm, 9.8barg (60cm)

Exp.3: 10mm, 9.8barg (85cm)

INERIS_2&5_JIP-III (10mm, 5.8barg)

INERIS_3_JIP-III (10mm, 9.8barg)

©


Too low droplet size (SMD) using CCPS too little rainout

10

100

1000

10000

10 100 1000 10000Measured SMD [microns]

Pre

dict

ed S

MD

[mic

rons

]

Cardiff_Cyclo-HexaneCardiff_WaterCardiff_GasolineCardiff_ButaneCardiff_PropaneINERIS_ButaneVKI - R134-ASTEP - PropaneHSL - PropaneINERIS - ButaneEcole de Mines - Water+30%-deviation-30%-deviation

©


Improved SMD prediction using Phase III JIP correlation

10

100

1000

10000


Pre

dict

ed S

MD

[mic

rons

]

Cardiff_Cyclo-HexaneCardiff_WaterCardiff_GasolineCardiff_ButaneCardiff_PropaneINERIS_ButaneVKI - R134-ASTEP - PropaneHSL - PropaneINERIS - ButaneEcole de Mines - Water+30%-deviation-30%-deviation

©


SMD prediction using Melhem correlation

10

100

1000

10000


Pre

dict

ed S

MD

[mic

rons

]

Cardiff_Cyclo-HexaneCardiff_WaterCardiff_GasolineCardiff_ButaneCardiff_PropaneINERIS_ButaneVKI - R134-ASTEP - PropaneHSL - PropaneINERIS - ButaneEcole de Mines - Water0% - deviation+30%-deviation-30%-deviation

©


Conclusions –

SMD correlation (meta-stable liquid assumption)

Yellow Book correlation -

conservation of momentum-

over-predicts

CCPS correlation-

Isentropic-

Wrongly advices to take Min (mechanical, flashing) leading to under-prediction-

CCPS flashing correlation over-predicts

JIP II correlation: superseded by JIP III correlation

JIP III proposed correlation-

Overall best agreement-

Seems to marginally over-predict for low stagnation pressures

Melhem correlation (as implemented in Phast)-

Worse or similar to JIP III correlation for all experimental datasets-

Generally under-predicts

©


Dispersion model development and validation

Robust modelling of rainout and re-evaporation-

Improved UDM link between pool and cloud-

Improved predictions for validation-

dispersion from LNG/LPG liquid pools (Burro, Coyote, Maplin Sands)-

dispersion from vapour area sources (Kit Fox)

Droplet parcels and distributed rainout-

range of droplet sizes-

critical droplet size below which rainout occurs-

validation against CCPS experiments-

Single SMD drop-

CCPS correlation (old Phast) under-predicts rainout-

JIP III (larger SMD) predicts more rainout than JIPII-

JIP III with 10 parcels more accurate than single-SMD JIP III correlation

©


Distributed rainout for liquid hexane release (release of 8 kg liquid hexane at 250K with initial SMD = 100μm)

Droplet Trajectories

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25 30

Downwind distance (m)

Hei

ght (

m)

Parcel 1Parcel 2Parcel 3Parcel 4Parcel 5Parcel 6Parcel 7Parcel 8Centreline

Accumulated Rainout Mass

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 5 10 15 20 25 30

Downwind distance (m)

Mas

s (k

g/s)

Droplet trajectories-

Smaller drops (parcels 1-4) fully evaporate

-

Larger drops (parcels 6-8) rainout

Distributed rainout

©


Validation against CCPS experimentsModelled Rainout Fraction against CCPS Rainout Fraction

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0.1 0.2 0.3 0.4 0.5 0.6 0.7

Corrected rainout mass fraction (CCPS)

Rai

nout

mas

s fr

actio

n (m

odel

led)

MeasuredJIP2 (SMD)JIP3 (SMD)JIP3 + 10 ParcelsCCPS

©

Det

Norske Veritas


Conclusions and future work

Conclusions-

Refined JIP III SMD correlation provides best fit against experimental data-

Improved distributed rainout predictions against CCPS experiments using JIP III droplet size distribution correlation

Future work-

Phase IV of droplet modelling JIP (2008-2010)-

sponsors: HSE, Exxon Mobil, DNV, RIVM, StatoilHydro, TOTAL-

objectives: -

compare droplet size measurement methods: HSL photographic versus JIPIII PDA-

enable validation for distributed rainout -

rainout experiments for sub-cooled octane releases (HSL)-

measurements: flow rate, initial droplet size, concentration, distributed rainout-

model refinement and model validation-

Additional rainout experiments and modelling improvements for:-

flashing releases-

multi-component releases

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