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
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 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 insulativemetallic 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 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.
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
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
radThermal 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.
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 Note1 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
TRIP TADP TWIP
Configuration entropy
Cantor
∆Smix= -Rln(xCrlnxCr+ xMnlnxMn+ xFelnxFe+ xColnxCo+ xNilnxNi)
∆Smix: Configuration entropy R: gas constant
xx: mole fraction
Sample preparation for Thermal diffusivity test
Cantor TWIP TRIP TADP
Thermal diffusivity specimen
Laser Flash Method
Thermal diffusivity of CCAs
50 100 150 200 250 300
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
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
Sample preparation for Thermal expansion coefficient test
Cantor TWIP TRIP TADP
Thermal expansion coefficient specimen
Thermomechanical Analyzer (TMA)
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.
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
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
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 ℃
(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
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)Numerical 3D Solution (FEA)
LNG Tank
9%Ni Temperature : -139.7 ℃
LNG Tank
CCAs Temperature : -139.7 ℃
5. Results: LNG Tank
Numerical 3D Solution (FEA)
Ship Structure
9%Ni Temperature : -2.14 ℃ Ship Structure
CCAs Temperature : 1.85 ℃
5. Results: Ship structure
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.
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
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)