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Variations in the evaporation rate of a cryogenic liquid on a water surface

Harri K. Kytömaa, Ph.D., P.E.Timothy L. Morse, Ph.D.

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Biography of the AuthorsBiography of the AuthorsDr. Harri K. Kytömaa, Ph.D., P.E.Corporate Vice President and Director of the Thermal Science Practice, Exponent Inc.

• Performs research in cryogenic fluid mechanics, heat transfer and phase changephenomena.

• Worked on numerous LNG projects with the industry in the US and internationally and haspublished extensively in this area.p y

• Member of the ISO TC67, WG10 working group that is developing a guidance document onthe major hazards associated with the planning and design of onshore LNG facilities andassociated marine activities.

• Has held several positions, including that of Associate Professor of Mechanical Engineering ath M h I i f T h lthe Massachusetts Institute of Technology.

Dr. Timothy L. Morse, Ph.D.S i A i t Th l S i P ti E t I

• Performs research in thermal and flow processes, including cryogenic fluid mechanics.• Extensive experience in experimental techniques for fluid dynamic and thermodynamic

systems.

Senior Associate, Thermal Science Practice, Exponent Inc.

y• Previously a researcher in the Fluid Mechanics Research Laboratories at Cornell University.

Conducted research in fluid-structure interaction.

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i i G iBackground: Previous studies on LNG evaporation

Authors Year Test name Evaporation rate (kg/s m2)(kg/s m )

Blackmore et al. 1982 Maplin Sands tests, 1980 0.085

Burgess et al. 1970 U.S. Bureau of Mines, lab tests 0.181

Burgess et al. 1972 U.S. Bureau of Mines, pond tests 0.155

Feldbauer et al. [Hightower et. al. 2004] 1972 Esso tests, Matagorda Bay 0.195

Boyle & Kneebone [Hightower et al 2004] 1972 Shell lab tests 0 024−0 195Boyle & Kneebone [Hightower et. al. 2004] 1972 Shell, lab tests 0.024 0.195

Valencia-Chavez & Reed 1979 Lab scale, pure methane 0.05−0.23

Valencia-Chavez & Reed 1979 Lab scale, tertiary LNG 0.02−0.28

Fay 2003 Theoretical 0.21−0.30

Conrado & Vesovic 2000 Theoretical; film boiling 0.072

Kli k d Sh l 1982 Th i l fil b ili l i 0 073Klimenko and Shelepen 1982 Theoretical; film boiling correlation 0.073

Range: 0.02 to 0.30

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i ( )Background: Hissong, D.W. (2007)“Keys to modeling LNG spills on water.” J. of Haz. Mat. Vol. 140, p. 465-477

Identified turbulence as an important factor

Defined a “turbulence factor” to adjust the heat Defined a “turbulence factor” to adjust the heat transfer coefficient between water and LNG

“Turbulence factor” determined empirically from LNG evaporation tests

“Turbulence factor” depends on spill velocity

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0.7

Background: LN2 Tests

0.4

0.5

0.6

ate

(kg/

s m

2 )

Presented at AICHE 2010 Spring Meeting

0.1

0.2

0.3

Eva

pora

tion

ra

Liquid nitrogen thickness has a large effect on evaporation

0.6

0

0.1

0 1 2 3 4 5 6 7

Thickness of LN2 (cm)

rate (unexpected result)

0.4

0.5

(kg/

s m

2 )

Quantified evaporation rate dependence on turbulence

0.2

0.3

Eva

pora

tion

rate

intensity

0

0.1

0 0.05 0.1 0.15 0.2 0.25 0.3

u rms (m/s)

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M d li LNG illModeling LNG spills

Models typically assume a constant evaporation rate

Spread rate

Evaporation rateSpill rate

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F t ff ti ti tFactors affecting evaporation rate

air temperatureair temperaturewind speed

spill thicknessinterface speed

water temperaturewater salinity

turbulence intensity

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Testing Setup vapor Testing Setupdouble‐walled 

tube vapor

pout

• Double-walled acrylic tubeID = 17.3 cm

cryogenic liquidturbulent surface

• Submerged jetCentrifugal pumpControl valve

turbulent jet

waterControl valveNozzle (1.3 cm diameter)

• LNG poured on top

nozzle

p pup to ~7 cm thick

flow control valve

pump

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Testing Setup

Front viewFront view

Testing Setup

Vent PortTop viewTop view

Fill Port

OrificePressure Relief ValveRelief Valve

Jet nozzleJet nozzle

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Experimental measurementsExperimental measurements

Evaporation ratevapor out

• Pressure (in cylinder)• Temperature at orifice• Orifice size

Mass flow rate through orifice

double‐walled tube vapor

cryogenic liquidturbulent surface

turbulent jet

cryogenic liquidsurface

Turbulence intensityMeasure water height fluctuations at the centerline

nozzlewater

22 2 hgu Δ=flow control valve

2uurms =pump

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W t f h i ht tWater surface height measurements

Rod Light source

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W t f h i ht tWater surface height measurements

Example imageExample imageOptical setup

Surface

surfaceRod

RodCylinder

Image processing → h(t)

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W t f h i ht tWater surface height measurements

0 3

0.4

present resultsy

0.2

0.3m

s (m

/s)

Hu (1993)

nce i

ntens

ity

0.1

u rm

Turb

ulen

0.00 2 4 6 8 10 12 14

Jet flow rate (GPM)Jet flow rate (GPM)

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iExample LN2 evaporation run urms = 0.12 m/s

bursts

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Effect of liquidEffect of liquid nitrogen height

3 runsVarying initial thickness

Plot vs. thickness remainingPlot vs. thickness remaining

Data collapses onto single trend

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Effect of cryogenic liquid height (LN2)0.7

0 5

0.6

m2 )

0.4

0.5

n ra

te (

kg/s

m

0.2

0.3

Eva

pora

tion

0

0.1

E

0 1 2 3 4 5 6 7

Thickness of LN2 (cm)

17

Effect of water turbulence (LN2)0.6

(avg. thickness ~ 2 cm)

0 4

0.5

s m

2 )

0.3

0.4

atio

n ra

te (k

g/s

0.1

0.2

Eva

pora

00 0.05 0.1 0.15 0.2 0.25 0.3

( / )u rms (m/s)

Increasing turbulence intensity

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G iExample LNG evaporation run urms = 0.22 m/s

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Thi k Eff t

LN2urms = 0.12 m/s

Thickness Effect: LNG vs. LN2

Evaporation rate much more dependent on liquid thickness for

LNG 0 22 m/s

liquid thickness for liquid nitrogen

urms = 0.22 m/s

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0.4

Effect of water turbulence (LNG) (avg. thickness ~ 2 cm)

0.3

kg/s

m2 )

0.2

ratio

n ra

te (

0.1

Evap

or

ICE(tests cannot be r n)

?

00 0.05 0.1 0.15 0.2 0.25 0.3

u rms (m/s)

(tests cannot be run)

Increasing turbulence intensity

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Previous investigationsPrevious investigationsAuthors Year Test name Evaporation rate

(kg/s m2)Blackmore et al. 1982 Maplin Sands tests, 1980 0.085

Burgess et al. 1970 U.S. Bureau of Mines, lab tests 0.181

Burgess et al. 1972 U.S. Bureau of Mines, pond tests 0.155Burgess et al. 1972 U.S. Bureau of Mines, pond tests 0.155

Feldbauer et al. [Hightower et. al. 2004] 1972 Esso tests, Matagorda Bay 0.195

Boyle & Kneebone [Hightower et. al. 2004] 1972 Shell, lab tests 0.024−0.195

Valencia-Chavez & Reed 1979 Lab scale, pure methane 0.05−0.23

Valencia-Chavez & Reed 1979 Lab scale, tertiary LNG 0.02−0.28

Fay 2003 Theoretical 0 21−0 30Fay 2003 Theoretical 0.21 0.30

Conrado & Vesovic 2000 Theoretical; film boiling 0.072

Klimenko and Shelepen 1982 Theoretical; film boiling correlation 0.073Present results 0.12 – 0.27

(depending on turbulence intensity)

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Range of LNG Evaporation DataRange of LNG Evaporation Data

0 3

0.35

0.2

0.25

0.3

te (kg/s m

2 )

Presentlt

0.1

0.15

vapo

ratio

n Ra

t results

0

0.05

Ev

Extrapolated to zero turbulence

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C l iConclusions

1 Evaporation rate can vary 1. Evaporation rate can vary significantly

2. Depends on:• Turbulence intensity • liquid layer thickness

(strongly)(less so for LNG) liquid layer thickness

• (other factors)

3 These factors should be 0.3

0.4

kg/s

m2 )

(less so for LNG)

3. These factors should be included in spill models

0.1

0.2

Eva

pora

tion

rate

(k

00 0.05 0.1 0.15 0.2 0.25 0.3

E

u rms (m/s)

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F t W kFuture Work

1. Incorporate results into spill model

2. Quantify other factors affecting evaporation rate

3. Determine underlying mechanism for thickness effecty g

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Acknowledgements

Distrigas of Massachusetts – Frank KatulacFor providing the LNG used in these testsFor providing the LNG used in these tests

MIT Cryogenic Laboratory – Prof Joseph SmithMIT Cryogenic Laboratory Prof. Joseph SmithFor use of cryogenic equipment

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Supplemental Material

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Wh i th l thi k ff t?Why is there a layer thickness effect?

Increased pressure at interface?

Nucleate Boiling Height effect

1 cm LN2: hydrostatic pressure = 0.01 psi

C li d 0 05 t 1 iFilm BoilingVarying orifice size (¼” to ½”)

Cylinder pressure = 0.05 to 1 psig

No noticeable effect on Evaporation

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0.6

Effect of water turbulence (LN2) (avg. thickness ~ 2 cm)

0 4

0.5

s m

2 )

0.3

0.4

atio

n ra

te (k

g/s

Orifice i

Evap. Rate (k / 2 )

Typ. Pressure ( i)

0.1

0.2

Eva

pora size (kg /m2s) (psi)

1/2” 0.1953 0.063/8” 0.1897 0.17

00 0.05 0.1 0.15 0.2 0.25 0.3

( / )

1/4" 0.2002 1.0

u rms (m/s)

Increasing turbulence intensity

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Wh i th l thi k ff t?Why is there a layer thickness effect?

Heat transfer through walls?

Natural acrylic ≈ 2 W

air LNG

atu agas vapor

Based on simple 1-D heat transfer,with LNG thickness of 1 cm (LN similar)air

water

with LNG thickness of 1 cm (LN2 similar)

N2 gas ≈ 1000 W

Based on a typical evaporation rate of 0.2 kg/m2 sBased on a typical evaporation rate of 0.2 kg/m s

Also: evaporation tests on iced over water shows no thickness effect