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Evaluation of LNG tank suitability of Complex concentrated Alloys through “Thermal Distribution Analysis”

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

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

(2)

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

(3)

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.

(4)

Utilization of CCAs on thermal insulation

Strong & Ductile

Thermally stable

Low conductivity

Highly formable

from cryogenic to elevated T

Low thermal expansion 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

(5)

Thermally insulativemetallic materials : HEA

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

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

Low 𝜿𝜿

(6)

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

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Basics of Heat Transfer

1. What is heat transfer?

Some kind of energy that can be transferred from one system to 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.

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Basics of Heat Transfer

3. Heat transfer Mechanisms 1) Conduction

Transfer of energy from the more energetic particles to the

adjacent less energetic ones as a result of interactions between the particles

2) Convection

Mode of energy transfer between a solid surface and adjacent liquid or gas that is in motion

3) Radiation

Energy emitted by matter in the form of electromagnetic waves

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Thermal resistance concept for tank

1. Conduction resistance 2. Convection resistance

3. Radiation and combined resistance

The convection and radiation

resistances are parallel to each other

h

combined

= h

conv

+ h

rad

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Thermal resistance concept for tank

4. Thermal resistance network

Rate of

heat convection or radiation into the wall

Rate of

= heat conduction = through the wall

Rate of

heat convection or radiation from the wall

We need this value.

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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

Gibbs free energy (HCP-FCC) (J)

Mn contents(%)

8 10 12 14 16 18 20 22 24 26 28

0 500 1000 1500 2000 2500 3000 3500 4000

Gibbs free energy (HCP-FCC) (J)

Ni contents(%)

14 16 18 20 22 24 26 28 30 32

0 500 1000 1500 2000 2500 3000 3500 4000

Gibbs free energy (HCP-FCC) (J)

Co contents(%)

18 20 22 24 26 28 30

0 500 1000 1500 2000 2500 3000 3500 4000

Gibbs free energy (HCP-FCC) (J)

Fe contents(%)

Co Mn Fe

Cr 20 20 20 20 Ni 20

Mn Ni Fe Co

By Lowering ∆G

γ→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

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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 ↑

(13)

Configuration entropy of CCAs

0 2 4 6 8 10 12 14

TRIP TADP TWIP

Configuration entropy

Cantor

∆Smix= -Rln(xCrlnxCr+ xMnlnxMn+ xFelnxFe+ xColnxCo+ xNilnxNi)

∆Smix: Configuration entropy R: gas constant

xx: mole fraction

(14)

Sample preparation for Thermal diffusivity test

Cantor TWIP TRIP TADP

Thermal diffusivity specimen

Laser Flash Method

(15)

Thermal diffusivity of CCAs

50 100 150 200 250 300

0 3 6 9

12 Cantor

TWIP TRIP TADP

Thermal diffusivity(mm2 /s)

Temperature(oC)

α = 𝟎𝟎. 𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏 � 𝒆𝒆𝒅𝒅𝟐𝟐

𝟏𝟏/𝟐𝟐

Temperature Signal Versus

Time

Laser Pulse α: Thermal diffusivity

d: thickness of the sample

t1/2: 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

(16)

Thermal conductivity in room temperature

κ = α * specific heat * Density

κ: Thermal conductivity α: Thermal diffusivity

12.0 12.3 12.6 12.9 13.2 13.5

0.012 0.014 0.016 0.018

Thermal conductivity

∆Smix

Cantor TWIP TRIP

TADP

κ ∆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

(17)

Sample preparation for Thermal expansion coefficient test

Cantor TWIP TRIP TADP

Thermal expansion coefficient specimen

Thermomechanical Analyzer (TMA)

(18)

Thermal expansion of CCAs

50 100 150 200 250 300

0 1 2 3 4 5

dL/L (mm/mm)

Temperature (°C)

Cantor TWIP TRIP TADP

CTLE = 𝟏𝟏

𝑳𝑳𝟎𝟎 𝒅𝒅𝑳𝑳 𝒅𝒅𝑻𝑻

CTLE: Coefficient of linear thermal expansion

L0: initial length 2.5 mm

5 mm

• Linear thermal expansion is used to determine the rate and which a material expands as a function of temperature.

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12.0 12.3 12.6 12.9 13.2 13.5 17.6

17.8 18.0 18.2 18.4 18.6

Thermal expansion coefficient

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

(20)

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

TWIP TRIP TADP

Thermal expansion(ppm/K)

Cantor 0.010

0.012 0.014 0.016 0.018 0.020 Thermal conductivity

Thermal conductivity(W/mm)

Single phase Multi phase

CCA have trade-off tendency of

“Thermal conductivity” vs “Thermal expansion coefficient”

Low Thermal conductivity

High Thermal expansion coefficient High Thermal conductivity

Low Thermal expansion coefficient

(21)

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

(22)

Numerical 3D Solution (FEA)

5 ℃

(Boundary Condition)AIR

0 ℃ SEA WATER

(Boundary Condition)

*-139.7 ℃

(Boundary Condition)LNG

Ship Side Shell

LNG Tank

Water Draft (m)

Ship Internal structure

3. Boundary condition

(23)

Numerical 3D Solution (FEA)

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

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

9%Ni Steel CCAsor

Insulation

Tank Size : 30K CBM

Thermal Conductivity

9%Ni : 0.029 W/mm

CCAs : 0.018W/mm

4. 3D modeling

(Input Tools : Hyper-Mesh)

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Numerical 3D Solution (FEA)

LNG Tank

9%Ni Temperature : -139.7 ℃

LNG Tank

CCAs Temperature : -139.7 ℃

5. Results: LNG Tank

(25)

Numerical 3D Solution (FEA)

Ship Structure

9%Ni Temperature : -2.14 ℃ Ship Structure

CCAs Temperature : 1.85 ℃

5. Results: Ship structure

(26)

Conclusion

The challenge of LNG

1. 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 LNG

inside 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-off occurs 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 pressure increases cannot be managed effectively and require alternative solutions.

Handling the pressure

If we controlled the low temperature against warming, we can keep a consistent pressure and control boil-off gas.

(27)

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”

(28)

Thank you for your kind attention

(29)

Mechanical property of CCAs

Cantor TWIP TRIP TADP

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 0.8

0 200 400 600 800 1000 1200 1400

Cantor TWIP TRIP TADP

True stress(σ)

True strain(ε)

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