Model Based Development of The Enhanced Multi-Mission Radioisotope - - PowerPoint PPT Presentation
Model Based Development of The Enhanced Multi-Mission Radioisotope Thermoelectric Generator and Effect of Thermoelectric Element Length on eMMRTG Swapnil Magdum 1 APRIL 2019 Western Michigan University Mechanical and Aerospace Engineering
Swapnil Magdum APRIL 2019 Western Michigan University Mechanical and Aerospace Engineering
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Introduction Literature Review Project Scope Dimensional Investigation 3-D Modelling Analytical Model Numerical Modelling and Simulation Results Conclusion Future Scope 2
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Images taken from http://www.space.com/12004-nasa-mars- rover-curiosity-photos-mars-science-laboratory.html
Figure 1- Conceptual image of the Curiosity Mars Rover Figure 2- The Curiosity Mars Rover at JPL during the final testing
Launched -11/2011, Landed - 07/2012
Figure 3- Cutaway of eMMRTG Figure 4- CAD model of eMMRTG and its component
Image taken from Woerner D. (2016). Image taken from Holgate et al. (2016).
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Figure 5 - GPHS used in eMMRTG Figure 6- Pu 238 as a fuel for GPHS
Image taken from Hammel et al. (2016)
Same cross-sectional area for both legs. Both use Skutterudite. This reduces overall complexity and analysis. This leads to an overall 25% power increase from the MMRTG.
Images taken from Woerner D.(2016).
Figure 7 - MMRTG and eMMRTG thermoelectric couples
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Holgate T., et al (2015).
Note: The only difference between the MMRTG and eMMRTG is the TE material used. Otherwise the two designs are identical.
Future Mars Rover Modification in the design of eMMRTG to obtain more output power Assumptions
Constant Heat Generation Simplified Model and Estimated dimensions Material properties are independent of temperature
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Images taken from Woerner D.(2016)
Figure 7 - Cutaway of eMMRTG
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Fin shell and fin Module bar Mica Heat distribution block TEG module Liner Aerogel insulation General Purpose Heat Source Figure 8 - Exploded view of the reproduced eMMRTG
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Lee, H.(2017).
Figure 9 - A system with only heat sink
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Heat flux Input Symmetry
Setting up the model with different input parameters
Figure 10 – Setting up the model
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Figure 11- Static temperature contour of all domains Figure 12- Static temperature contour of P-type thermoelement
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Temperature distribution in the thermoelectric element
Figure 13- Static temperature contour of thermoelectric couple
Temperature (K) ANSYS Result JPL Result Hot Side 818.1 873 Cold Side 408.3 373-473
Table 2 - comparison of ANSYS result and JPL result
300 400 500 600 700 800 900 2 4 6 8 10 12 14
Temprature (K) Leg Length (mm)
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Figure 14- Heat transfer from fin to atmosphere (XZ plane) Figure 15- Heat transfer from fin shell to atmosphere (YZ plane)
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Figure 16 - Velocity streamlines (YZ plane) Figure 17 - Temperature profile along the fin
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Image taken from Bardy, E. (2008).
Figure 18 - Theoretical velocity and thermal profile in natural convection along a vertical wall Figure 19 - Thermal boundary layer thickness
290 300 310 320 330 340 350 5 10 15 20 25 30 35
Temperature (K) Length of the fin (mm)
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Image taken from Bardy, E. (2008).
0.01 0.02 0.03 0.04 0.05 0.06 0.07 5 10 15 20 25 30 35
Velocity (m/s) Length of the fin (mm)
Figure 20 - Theoretical velocity and thermal profile in natural convection along a vertical wall Figure 21 - Velocity boundary layer thickness
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𝑆𝑏 = . β. 𝑈
𝑡 − 𝑈𝑗𝑜𝑔 . 𝑀3
α. υ 𝑂𝑣 = 0.6 + 0.387. 𝑆𝑏
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1 + 0.559 𝑄𝑠
9 16 8 27 2
ℎ = 𝑂𝑣. 𝑙𝑏 𝑀 = 9.807 𝑛 𝑡2 𝑙𝑏 = 27.1𝑓 − 3 𝑋 𝑛2𝐿 α = 26.3𝑓−6 𝑛2 𝑡 υ = 18𝑓−6 𝑛2 𝑡 β = 1 𝑈
𝑔
Pr = 0.72 𝑀 = 0.465 𝑛
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Local Heat transfer coefficient along the vertical wall of the fin shell
ℎ𝐵𝑗𝑠 = 2.64 W/m2K ℎ𝐷𝑃2 = 1.12 W/m2K
Analytical Average heat transfer coefficient on the Earth and on the Mars
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Figure 22 – Thermal-Electric Analysis
I = 1.62A 𝑆𝑚𝑓𝑡 = 0.03605 Ω Total 𝑆𝑚𝑓𝑡 = 6.9234 Ω 𝑆𝑚𝑝𝑏𝑒 = 6.9234 Ω 𝑄𝑣𝑜𝑗𝑢 = 𝐽2𝑆𝑚𝑝𝑏𝑒 𝑄𝑣𝑜𝑗𝑢 = 18.17 W 𝑄𝑢𝑝𝑢𝑏𝑚 = 145.36 W
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Table 3 - Comparison of the numerical and the analytical results with the literature
Numerical and Analytical results comparison with the literature
Parameters Literature Results [JPL Results] Numerical Results Analytical Results The hot junction temperature (K) 873 818.1 922.38 The cold junction temperature (K) 373-473 408.3 325.13 Current induced in the circuit (A)
1.64 The output power of the 1/8th unit (W)
18.62 The total output power of the unit (W) 145-170 145.36 148.92
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Table 4 – Effect of the ceramic material on the power output
Effect of the ceramic material on the power output
Material Thermal Conductivity (W/mK) Hot Side (K) Cold side (K) Current (A) Power of the 1/8th unit (W) Total power output (W) Alumina 22 818.1 408.3 1.62 18.17 145.36 Aluminum nitride 140 862.2 442.72 1.71 20.23 161.87
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Figure 24 - Effect of the thermoelectric leg length on the power output
Effect of the thermoelectric element leg length on the power output
Figure 23 - Thermoelectric couple
Image taken from Hammel et al. (2016)
155 165 175 185 195 205 215 225 235 2 4 6 8 10 12 14 Output power (W) Thermoelectric element leg length (mm) Power
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Table 5 – Thermoelectric element leg length effect on the power output
Effect of the thermoelectric element leg length on the power output
Leg length (mm) Load resistance (Ω) Current (A) Power of the 1/8th unit (W) Total power output (W) Rise in the total power output (%) 1 0.55 7.03 27.18 217.45 49.59 % 3 1.64 3.80 23.68 189.44 30.32 % 6 3.27 2.59 21.93 175.44 20.69 % 9 4.91 2.04 20.45 163.60 12.55 % 12.7 6.92 1.71 20.23 161.87 11.35 %
Effect of ceramic material – 11.35% power improvement Effect of Thermoelectric element leg length – 49.59% power improvement
Up to 6 mm- a little bit improvement in the power output At 3 mm and 1 mm – drastic improvement Enable to reduce weight (for the Spacecraft)
Future Scope
ZT value improvement Investigation of the optimum load resistance to internal resistance ratio
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