evaluation of lng tank suitability of complex concentrated

Department of Materials Science and Engineering,Seoul National University, Republic of Korea

ESPark Research Group e-mail : [email protected] : http://espark.snu.ac.kr

Evaluation of LNG tank suitability of

Complex concentrated Alloys through

“Thermal Distribution Analysis”

Current Status of Structural Materials

2020.06.29

Jeong-Won Yeh, Sanghun Son

2ESPark Research Group

Introduction of LNG tank

Liquefied Gas Carrier always keep the cryogenic temperature

• basic theories including science about heat transfer

• applied LNG carrier (IMO-Type C Tank) in practice.

Brittle fracture of LNG tnak

detailed study about thermal distribution of hull is needed


Utilization of CCAs on thermal insulation

• Strong & Ductile

• Thermally stable

• Low conductivity

• Highly formable

from cryogenic to elevated T

• Low thermal expansion coefficient

LNG tank materials

CCA structure

∆𝑆𝑆𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐. = 𝑅𝑅𝑅𝑅𝑅𝑅(𝑅𝑅)𝒏𝒏𝒏𝒏𝒏𝒏𝒏𝒏𝒏𝒏𝒏𝒏 𝒐𝒐𝒐𝒐 𝒏𝒏𝒆𝒆𝒏𝒏𝒏𝒏𝒏𝒏𝒏𝒏𝒆𝒆𝒆𝒆 ↑ ↔ 𝒄𝒄𝒐𝒐𝒏𝒏𝒐𝒐𝒄𝒄𝒄𝒄𝒏𝒏𝒏𝒏𝒄𝒄𝒆𝒆𝒄𝒄𝒐𝒐𝒏𝒏𝒄𝒄𝒆𝒆 𝒏𝒏𝒏𝒏𝒆𝒆𝒏𝒏𝒐𝒐𝒆𝒆𝒆𝒆 ↑

∆𝑮𝑮𝒄𝒄𝒐𝒐𝒏𝒏𝒐𝒐𝒄𝒄𝒄𝒄. = ∆𝑯𝑯𝒄𝒄𝒐𝒐𝒏𝒏𝒐𝒐𝒄𝒄𝒄𝒄. − 𝑻𝑻∆𝑺𝑺𝒄𝒄𝒐𝒐𝒏𝒏𝒐𝒐𝒄𝒄𝒄𝒄.


Utilization of CCAs on thermal insulation

• Strong & Ductile

• Thermally stable

• Low conductivity

• Highly formable

from cryogenic to elevated T

• Low thermal expansion coefficient

LNG tank materials

(1) Thermodynamics : high entropy effect

(2) Kinetics : sluggish diffusion effect

(3) Structure : severe lattice distortion effect

(4) Property : cocktail effect

(3) Structure : severe lattice distortion effect

Distorted lattice of HEA can hinder thermal conduction effectively

Fracture toughness & yield strength – CrMnFeCoNi


Thermally insulative metallic materials : HEA

Appl. Phys. Lett. 109, 061906 (2016)

CCA is one of the most thermal-insulative materials among metals

Low

𝜿𝜿


Contents

1. Basics of Heat Transfer

2. Thermal resistance concept for tank

3. Relationship between configuration entropy and Thermal properties

5. Conclusion

• Thermal conductivity • Thermal expansion coefficient

4. Thermal Distribution Analysis


Basics of Heat Transfer

1. What is heat transfer?Some kind of energy that can be transferred from one systemto another as a results of temperature difference.

2. The law of heat transfer (Thermodynamics)1) Conservation of Energy

(Energy Balance for System)(No work, Just stored energy)

Energy required to raise the temperature of unit mass by 1℃

2) Heat be transferred in the direction of decreasing temperature.


Basics of Heat Transfer

3. Heat transfer Mechanisms1) Conduction

Transfer of energy from the more energetic particles to theadjacent less energetic ones as a result of interactions betweenthe particles

2) ConvectionMode of energy transfer between a solid surface and adjacent

liquid or gas that is in motion

3) RadiationEnergy emitted by matter in the form of electromagnetic waves


Thermal resistance concept for tank

1. Conduction resistance

2. Convection resistance

3. Radiation and combined resistance

The convection and radiationresistances are parallel to each other

hcombined = hconv + hrad


Thermal resistance concept for tank

4. Thermal resistance network

Rate ofheat convection or radiation

into the wall

Rate of= heat conduction =

through the wall

Rate ofheat convection or radiation

from the wall

We need this value.


CCA design with similar σy and different deformation mechanism

8 10 12 14 16 18 20 22 24 26 28

0

500

1000

1500

2000

2500

3000

3500

4000

Gib

bs fr

ee e

nerg

y (H

CP-F

CC) (

J)

Mn contents(%)8 10 12 14 16 18 20 22 24 26 28

0

500

1000

1500

2000

2500

3000

3500

4000

Gib

bs fr

ee e

nerg

y (H

CP-

FCC

) (J)

Ni contents(%)14 16 18 20 22 24 26 28 30 32

0

500

1000

1500

2000

2500

3000

3500

4000

Gib

bs fr

ee e

nerg

y (H

CP-

FCC

) (J)

Co contents(%)18 20 22 24 26 28 30

0

500

1000

1500

2000

2500

3000

3500

4000

Gib

bs fr

ee e

nerg

y (H

CP-

FCC

) (J)

Fe contents(%)

CoMn FeCr Ni20 20 20 20 20

Mn Ni Fe Co

By Lowering ∆Gγ→ε , deformation mechanism can be changed

# Composition ∆G(hcp-fcc)(J) Deformation mechanism Note

1 Cr20Mn20Fe20Co20Ni20 1927.8 Dislocation gliding Cantor

2 Cr20Mn14Fe24Co24Ni16 771.0 Twinning TWIP

3 Cr20Mn10Fe30Co30Ni10 245.3 Phase transformation TRIP

4 Cr20Mn8Fe32Co32Ni8 59.4 Phase transformation TADP


Tendency of thermal conductivity

Temp ↑Collision frequency ↑

Scattering free electron ↑Thermal diffusivity ↓

What tendency does thermal conductivity show as ∆Smix increases in 5 component system?

1, 2, 3 component system: Temp↑, κ↓ 4, 5 component system: Temp↑, κ ↑

Temp ↑Energy of free electron ↑


Configuration entropy of CCAs

0

2

4

6

8

10

12

14

TADPTRIPTWIP

Co

nfig

urat

ion

entro

py

Cantor

∆Smix = -Rln(xCrlnxCr + xMnlnxMn + xFelnxFe + xColnxCo + xNilnxNi)∆Smix: Configuration entropyR: gas constantxx: mole fraction


Sample preparation for Thermal diffusivity test

Cantor TWIP TRIP TADP

Thermal diffusivity specimen

Laser Flash Method


Thermal diffusivity of CCAs

50 100 150 200 250 3000

3

6

9

12


Ther

mal

diffu

sivity

(mm

2 /s)

Temperature(oC)

α = 𝟎𝟎.𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏 � 𝒅𝒅𝟐𝟐

𝒆𝒆𝟏𝟏/𝟐𝟐

Temperature Signal VersusTime

Laser Pulse

α: Thermal diffusivityd: thickness of the samplet1/2: time to the half maximum in s

• Energy heats the sample on the bottom side and detector detects the

temperature signal versus time on the top side

• In 5 component system, Thermal diffusivity tends to increase as the

temperature increases


Thermal conductivity in room temperature

κ = α * specific heat * Densityκ: Thermal conductivityα: Thermal diffusivity

12.0 12.3 12.6 12.9 13.2 13.5

0.012

0.014

0.016

0.018

Ther

mal

cond

uctiv

ity

∆Smix

Cantor

TWIP

TRIP

TADPκ ∆Smix

Cantor 0.01133 13.38087

TWIP 0.01326 13.0769

TRIP 0.01436 12.51081

TADP 0.01828 12.09888

Thermal diffusivity decreases when Configuration entropy increases


Sample preparation for Thermal expansion coefficient test


Thermal expansion coefficient specimen

Thermomechanical Analyzer (TMA)


Thermal expansion of CCAs

50 100 150 200 250 3000

1

2

3

4

5

dL/L

(mm

/mm

)

Temperature (°C)


CTLE = 𝟏𝟏𝑳𝑳𝟎𝟎

𝒅𝒅𝑳𝑳𝒅𝒅𝑻𝑻

CTLE: Coefficient of linear thermal expansion

L0: initial length 2.5 mm

5 m

m

• Linear thermal expansion is used to determine the rate and which a material

expands as a function of temperature.


12.0 12.3 12.6 12.9 13.2 13.517.6

17.8

18.0

18.2

18.4

18.6

Ther

mal

expa

nsio

n co

effic

ient

∆Smix

Thermal expansion coefficient in room temperature

Thermal diffusivity increases when Configuration entropy increases

Cantor

TWIP

TRIP

TADP

CTLE ∆Smix

Cantor 18.56 13.38087

TWIP 17.97 13.0769

TRIP 17.78 12.51081

TADP 17.69 12.09888


trade-off tendency between “Thermal conductivity” vs “Thermal expansion coefficient”

17.6

17.8

18.0

18.2

18.4

18.6

18.8 Thermal expansion coefficient

TADPTWIP TRIP

Ther

mal

expa

nsio

n(pp

m/K

)

Cantor0.010

0.012

0.014

0.016

0.018

0.020

Thermal conductivity

Ther

mal

cond

uctiv

ity(W

/mm

)

Single phase Multi phase

CCA have trade-off tendency of “Thermal conductivity” vs “Thermal expansion coefficient”

Low Thermal conductivityHigh Thermal expansion coefficient

High Thermal conductivityLow Thermal expansion coefficient


Numerical Solution

1. Why 3D FEA Solution needed?• The analytical 2D calculation using heat equilibrium equation can solve only

one direction of heat transfer. • So, 3D FEA is needed to check considering 3-dimensional analysis.

2. FEA Tools• Solver: ABAQUS


Numerical 3D Solution (FEA)

5 ℃

AIR(Boundary Condition)

0 ℃

SEA WATER(Boundary Condition)

*-139.7 ℃

LNG(Boundary Condition)

Ship Side Shell

LNG Tank

Water Draft (m)

Ship Internal structure

*Start temperature is considered with the convection of the internal gas

3. Boundary condition



<Ship Model - Whole> <Ship Model - Internal View>

<LNG Tank Model - Whole> <LNG Tank Model - Internal View>

9%Ni Steelor

CCAs

Insulation

◎ Tank Size : 30K CBM◎ Thermal Conductivity• 9%Ni : 0.029 W/mm• CCAs : 0.018W/mm

4. 3D modeling (Input Tools : Hyper-Mesh)



LNG Tank9%Ni Temperature : -139.7 ℃

LNG TankCCAs Temperature : -139.7 ℃

5. Results: LNG Tank



Ship Structure9%Ni Temperature : -2.14 ℃

Ship StructureCCAs Temperature : 1.85 ℃

5. Results: Ship structure


Conclusion

The challenge of LNG1. While the tanks on an LNG carrier are designed to stay cool, they cannot provide perfect

insulation against warming. Heat slowly affects the tanks, which can cause the LNGinside to evaporate and produces a substance known as boil-off gas (BOG).

2. Natural gas remains liquefied by staying at a consistent pressure, but when boil-offoccurs and it returns to gas, the larger volume of gas will increase the tank pressure.

3. While the tanks are designed to handle the rise over short distances, prolonged pressureincreases cannot be managed effectively and require alternative solutions.

Handling the pressureIf we controlled the low temperature against warming, we can keep a consistent pressureand control boil-off gas.


Conclusion

From this study, it can be mentioned that CCAs’ conductivity is lower than the 9%Ni steel’s conductivity then maintaining and storing LNG at a stable temperature can be managed effectively in the LNG tank applied with CCAs.

CCA have trade-off tendency of “Thermal conductivity” vs “Thermal

expansion coefficient”

Thank you for your kind attention


Mechanical property of CCAs


Yield stress(MPa) 307 279 291 300

Ultimate stress(MPa) 679 699 798 870

Uniform elongation 0.32 0.45 0.46 0.42

*TADP: TRIP-assisted dual phase

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

200

400

600

800

1000

1200

1400


True

stre

ss(σ

)

True strain(ε)

evaluation of lng tank suitability of complex concentrated

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