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Modeling and Analysis of a Heat Transport Transient Test Facility for Space Nuclear Systems

Modeling and Analysis of a Heat Transport Transient Test Facility for Space Nuclear Systems. Adam Wheeler Department of Nuclear Engineering & Radiation Health Physics Oregon State University March 20, 2013. Outline. Introduction Reference design Variations from the Reference Design

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Modeling and Analysis of a Heat Transport Transient Test Facility for Space Nuclear Systems

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  1. Modeling and Analysis of a Heat Transport Transient Test Facility for Space Nuclear Systems Adam Wheeler Department of Nuclear Engineering & Radiation Health Physics Oregon State University March 20, 2013

  2. Outline • Introduction • Reference design • Variations from the Reference Design • Modeling programs • SolidWorks • STELLA • Models • Goals • Assumptions • Results from analysis • Discussion of results • Conclusion and future work • References

  3. Introduction • Objective: Develop and analyze a test facility based on a 1 to 10kWe heat-pipe cooled space nuclear reactor • Goals: • Design a feasible test facility • Predict steady state performance • Predict transient responses • Method: Use a lumped parameter model and a 3D CAD simulation program for analysis

  4. Reference Design • Reference system is a 1 to 10kWe reactor module • Developed by a collaboration between NASA Glenn and Marshall Research Centers and Los Alamos National Laboratory

  5. Newest Rendition of the Reference Design • Heat pipes on the outside of the reflector instead of in the core • Or heat pipes between the reflector and the fuel • Conductive material based radiator with heat pipe bands on the inside to spread the heat load

  6. Variations from the Reference Design Original Design • 1000K sodium heat pipes in core • 8 to 16 heat pipes from core to power convertors • Pin or plate fuel interface to heat pipes • Direct energy conversion via Stirling engines or Thermoelectrics • Cone-shaped radiator array Test Facility • 423 to 600K water heat pipes in core simulator • 8 heat pipes between core & power convertor simulators • Stainless steel cylinder interface to heat pipes • Power conversion thermal absorption simulator • Cylindrical radiator array

  7. Heat Pipe Data

  8. Water Heat Pipe Limits

  9. Limits to the System • Upper bounds: • 600K in the heat pipes from the core to the ECS • 600K in the radiator array heat pipes • 1171K in the stainless steel cylinders (70% ) • Lower bounds: • 423K in the heat pipes from the core to the ECS • 423K in the radiator array heat pipes • Representative heater rod manufacturer limits • 1255 K maximum for the Incoloy sheath • A maximum of 10 to 15.5 W/cm^2 • Precise levels TBD depending on manufacturer

  10. Modeling Programs SolidWorks • Used for 3D rendering and various types of simulations • Flow Simulation package allows for heat and fluid flow in a time dependent simulation • Lacks computational stability and speed but can give very detailed results STELLA • Object oriented flow based system • Great for modeling the transfer of some item (heat, chemicals, water, population, etc.) to another location through time • Lacks accuracy and detail but is very versatile and fast (STELLA can be made more accurate but quickly reaches a diminishing return in effort and time which makes more complex programs such as STAR-CCM and FLUENT more attractive)

  11. SolidWorks Model Boundary Conditions • To simulate the affects of convection, a direct heat sink boundary condition was applied which simplified the model • A heat source was placed in the core simulator’s heater rods • To model the heat pipes, a custom material with very high conductance at the heat pipe’s operating temperatures was used along with the heat pipe operator in Flow Simulation • Radiation transfer boundary conditions were placed on the outer surfaces of the model ECS

  12. Flow Simulation Interface

  13. Stella Model Assumptions • Axial heat transfer is negligible in comparison to radial heat transfer • Heat transfer to and from sinks and sources can be done with 1D radial methods • Adiabatic boundary conditions assumed for outer edges of the system

  14. Stella Model Energy Conversion Simulator Cross-section Core Simulator Cross-section

  15. STELLA Model • STELLA model uses three basic components • Convertor • Used to control flow and system variables • Reservoir • Points for collecting the heat passing through system • Bidirectional flow • Forces directional flow between Reservoirs and • Controlled by connections between Convertors and Reservoirs

  16. STELLA Model

  17. STELLA Model • The whole thing:

  18. Scenarios Analyzed • Startup • STELLA and SolidWorks In-Depth Discussion • One Core Heat Pipe Lost • STELLA and SolidWorks In-Depth Discussion • Staggered Core Heat Pipes Lost • SolidWorks Only, In-Depth Discussion • One Bank of Radiator Heat Pipes Lost • SolidWorks Only, In-Depth Discussion • Two Core Heat Pipes Lost • STELLA and SolidWorks, Brief Overview • Three Core Heat Pipes Lost • SolidWorks only, Brief Overview • Opposite Core Heat Pipes Lost • SolidWorks only, Brief Overview • One Absorber Lost • SolidWorks only, Brief Overview • One Radiator Heat Pipe Lost • STELLA and SolidWorks, Brief Overview

  19. STELLA Results: Startup Core Heat Pipes

  20. STELLA Results: Startup Radiator Heat Pipes

  21. SolidWorks Results: Startup Core Heat Pipes

  22. Core

  23. SolidWorks Results: Startup Radiator Heat Pipes

  24. Radiator

  25. ECS

  26. STELLA Results: One Core HP Lost

  27. STELLA Results: One Core HP Lost

  28. SolidWorks Results: One Core HP Lost

  29. SolidWorks Results: One Core HP Lost

  30. SolidWorks Results: One Core HP Lost Core

  31. ECS

  32. SolidWorks Results: One Core HP Lost

  33. Radiator System

  34. STELLA Comparisons • Startup • One Core Heat Pipe Lost • Two Core Heat Pipes Lost • Continue the trend of startup and one core heat pipe lost scenarios • One Radiator Heat Pipe Lost • Showed the same trend as previous comparisons (all scenarios were run with STELLA and the trends stayed constant throughout, but there is not enough time or room to speak on all of them)

  35. SolidWorks Results: Staggered Heat Pipes Lost Core

  36. ECS

  37. SolidWorks Results: Staggered Heat Pipes Lost

  38. SolidWorks Results: Four Radiator Heat Pipes Lost Core

  39. ECS

  40. SolidWorks Results: Four Radiator Heat Pipes Lost

  41. Radiator

  42. SolidWorks Results: Two Core Heat Pipes Lost ECS Core System Radiator

  43. SolidWorks Results: Three Core Heat Pipes Lost ECS Core Radiator System

  44. SolidWorks Results: Opposite Core Heat Pipes Lost ECS Core System Radiator

  45. SolidWorks Results: One Absorber Lost ECS Core

  46. SolidWorks Results: One Absorber Lost Radiator System

  47. SolidWorks Results: One Radiator Heat Pipe Lost ECS Core System Radiator

  48. Discussion of Results • STELLA: • System is fast in responding to heat transients • Temperature changes as a result of heat pipe losses are less then 100 K • The changes in temperatures in comparison to SolidWorks are off by as much as 40 K • Startup steady state is 40 K less than SolidWorks • SolidWorks: • Reasonably agrees with the STELLA time changes, and shows in greater detail and accuracy the temperature differences across the system

  49. Discussion of Results

  50. Conclusion • STELLA can be used for a rough first analysis because the differences from it to SolidWorks are consistent • SolidWorks is a valuable tool, but it needs a better heat pipe model with a lower and upper temperature bound • Heat pipes are resilient heat transport mechanisms which work well with low power systems • The resilience is shown in their ability to withstand and continue operations even after catastrophic failures • Heat pipes undergo a graceful degradation in transient scenarios • Heat pipes are not appropriate for high MW class systems • Scenarios analyzed are safe for testing in the yet to be built Heat Transport Transient Test Facility (?)

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