variations in the evaporation rate of a cryogenic liquid ... · evaporation rate (kg/s m2)...
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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)
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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