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

Outline 2  Introduction  Literature Review  Project Scope  Dimensional Investigation  3-D Modelling  Analytical Model  Numerical Modelling and Simulation  Results  Conclusion  Future Scope

Introduction - MMRTG 3 Launched -11/2011, Landed - 07/2012 Figure 1- Conceptual image of the Curiosity Mars Rover Figure 2- The Curiosity Mars Rover at JPL during the final testing Images taken from http://www.space.com/12004-nasa-mars- rover-curiosity-photos-mars-science-laboratory.html

Introduction - eMMRTG 4 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).

General Purpose Heat Source (GPHS) 5 Figure 5 - GPHS used in eMMRTG Figure 6- Pu 238 as a fuel for GPHS Image taken from Hammel et al. (2016)

Thermoelectric Couple 6  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. Figure 7 - MMRTG and eMMRTG thermoelectric couples Images taken from Woerner D. ( 2016).

Introduction - MMRTG vs eMMRTG 7 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.

Project Scope 8  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

ANSYS - Dimensional Investigation 9 Figure 7 - Cutaway of eMMRTG Images taken from Woerner D.(2016)

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Exploded view of the reproduced eMMRTG 12

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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15 Analytical Modelling

A Simple Analytical Model 16 Figure 9 - A system with only heat sink Lee, H.(2017).

17 Numerical Modelling and Simulation

Setting up the model with different input parameters 18 Symmetry Heat flux Input Figure 10 – Setting up the model

19 Figure 12- Static temperature contour of P-type thermoelement Figure 11- Static temperature contour of all domains

Temperature distribution in the thermoelectric element 20 900 800 700 Temprature (K) 600 500 400 300 0 2 4 6 8 10 12 14 Leg Length (mm) Temperature (K) ANSYS Result JPL Result 818.1 873 Hot Side 408.3 373-473 Cold Side Figure 13- Static temperature contour of thermoelectric couple Table 2 - comparison of ANSYS result and JPL result

21 Figure 14- Heat transfer from fin to atmosphere (XZ plane) Figure 15- Heat transfer from fin shell to atmosphere (YZ plane)

22 Figure 16 - Velocity streamlines (YZ plane) Figure 17 - Temperature profile along the fin

Thermal Boundary Layer Thickness 23 350 340 330 Temperature (K) 320 310 300 290 0 5 10 15 20 25 30 35 Length of the fin (mm) Figure 18 - Theoretical velocity and on the Mars on the Earth thermal profile in natural convection Figure 19 - Thermal boundary layer thickness along a vertical wall Image taken from Bardy, E. (2008).

Velocity Boundary Layer Thickness 24 0.07 0.06 0.05 Velocity (m/s) 0.04 0.03 0.02 0.01 0 0 5 10 15 20 25 30 35 Length of the fin (mm) Figure 20 - Theoretical velocity and on the Mars on the Earth thermal profile in natural convection Figure 21 - Velocity boundary layer thickness along a vertical wall Image taken from Bardy, E. ( 2008).

Average Convention Heat Transfer Coefficient (h) for Vertical Natural Convection 25 β = 1 υ = 18𝑓 −6 𝑛 2 𝑕 = 9.807 𝑛 α = 26.3𝑓 −6 𝑛 2 𝑋 Pr = 0.72 𝑙 𝑏 = 27.1𝑓 − 3 𝑈 𝑡 2 𝑛 2 𝐿 𝑡 𝑡 𝑔 𝑀 = 0.465 𝑛 𝑡 − 𝑈 𝑗𝑜𝑔 . 𝑀 3 𝑆𝑏 = 𝑕. β. 𝑈 α. υ 2 1 0.387. 𝑆𝑏 6 𝑂𝑣 = 0.6 + 8 9 27 1 + 0.559 16 𝑄𝑠 ℎ = 𝑂𝑣. 𝑙 𝑏 𝑀

Local Heat transfer coefficient along the vertical wall of the fin shell 26 Analytical Average heat transfer coefficient on the Earth and on the Mars ℎ 𝐵𝑗𝑠 = 2.64 W/m 2 K ℎ 𝐷𝑃2 = 1.12 W/m 2 K

• Power calculations- 27 I = 1.62A 𝑆 𝑚𝑓𝑕𝑡 = 0.03605 Ω Total 𝑆 𝑚𝑓𝑕𝑡 = 6.9234 Ω 𝑆 𝑚𝑝𝑏𝑒 = 6.9234 Ω 𝑄 𝑣𝑜𝑗𝑢 = 𝐽 2 𝑆 𝑚𝑝𝑏𝑒 𝑄 𝑣𝑜𝑗𝑢 = 18.17 W 𝑄 𝑢𝑝𝑢𝑏𝑚 = 145.36 W Figure 22 – Thermal-Electric Analysis

Numerical and Analytical results comparison with the literature 28 Literature Results Parameters Numerical Results Analytical Results [JPL Results] The hot junction 873 818.1 922.38 temperature (K) The cold junction 373-473 408.3 325.13 temperature (K) Current induced in the - 1.62 1.64 circuit (A) The output power of the - 18.17 18.62 1/8th unit (W) The total output power of 145-170 145.36 148.92 the unit (W) Table 3 - Comparison of the numerical and the analytical results with the literature

29 Effect of ceramic material on the power output

Effect of the ceramic material on the power output 30 Thermal Conductivity Hot Side Cold side Current Power of the 1/8th unit Total power output Material (W/mK) (K) (K) (A) (W) (W) 22 818.1 408.3 1.62 18.17 145.36 Alumina Aluminum 140 862.2 442.72 1.71 20.23 161.87 nitride Table 4 – Effect of the ceramic material on the power output

31 Effect of thermoelectric element leg length on the power output

Effect of the thermoelectric element leg length on the power output 32 235 225 215 Output power (W) 205 195 185 175 165 155 0 2 4 6 8 10 12 14 Thermoelectric element leg length (mm) Power Figure 23 - Thermoelectric couple Figure 24 - Effect of the thermoelectric leg length on the power output Image taken from Hammel et al. (2016)

Effect of the thermoelectric element leg length on the power output 33 Leg Load resistance Current Power of the 1/8th unit Total power output Rise in the total power output length ( Ω ) (A) (W) (W) (%) (mm) 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 % Table 5 – Thermoelectric element leg length effect on the power output

34 Conclusion  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

Questions 35