1. TFAWS Paper Session DeCoM Validation Presented By Deepak Patel NASA/ Goddard Space Flight Center Thermal & Fluids Analysis Workshop TFAWS 2011 August 15-19, 2011 NASA Langley Research Center Newport News, VA

2. Hume Peabody Matthew Garrison Dr. Jentung Ku Tamara O'Connell Thermal Engineering Branch at Goddard Space Flight Center TFAWS 2011 – August 15-19, 2011 2 Acknowledgments

3. Outline Introduction –Thermal Analysis Tools –Analysis cases Developed/Exercised 1D computer codes –DeCoM/EXCEL –TTH –FloCAD Compare 1D Results Validate against 2D Test Case Integrate into ATLAS Instrument Model Conclusion –Problems Encountered/ Lessons Learned –Summary –Future Work TFAWS 2011 – August 15-19, 2011 3

4. Introduction: Thermal Analysis Tools Thermal Analysis is based on a Nodal Network Scheme Thermal Desktop (TD): Used for View Factors and Environmental heat calculations. –A GUI (Graphical User Interface) for GMM (Geometric Math Model). Also generates SINDA (System Improved Numerical Differencing Analyzer) construct logics FloCAD: GUI for FLUINT (Fluid Integrator) constructs. 4 TFAWS 2011 – August 15-19, 2011

5. Introduction: Analysis Cases 1D – Radiator –Similar area to ATLAS radiator model in Thermal Desktop (TD) 1D – Condenser (1D Flow) – Length: 372in, Diameter: ¼” – Steady state conditions, constant mass flowrate – Ammonia as working fluid Environment – Radiative Tsink = -80C Limitations –Single condenser line –No evaporator/CC modeled – Short condenser nodes (2” Nodes) Analysis Cases & Calculated % Area margin 5 Power (W) Saturation Temperature ( o C) Calculated Area (in^2) ATLAS Radiator Area (in^2) % Area Margin 216-4 19072232 15.0 21616 13142232 41.0 14223 7672232 66.0 ATLAS Laser Scenarios 6 in 372 in ATLAS Radiator: The routing and the radiator are represented, in order to create a simplified 1D model (as shown below) **Cases developed for test-bed/development purposes – not design

6. Outline Introduction Developed/Exercised 1D computer codes –DeCoM –TTH –FloCAD Compare 1D Results Validate against 2D Test Case Integrate into ATLAS Instrument Model Conclusion –Problems Encountered/ Lessons Learned –Summary –Future Work 6 TFAWS 2011 – August 15-19, 2011

7. EXCEL/DeCoM Implementation EXCEL implementation –Calculate LHP condenser performance off-line using boundary conditions similar to those from the 1D analysis cases. –Project GLAS (GeoScience Laser Altimeter System) had predicted its condenser results based on EXCEL analysis similar to the one in this implementation. –Tested for steady state results only. For multiple iterations, manual input is required. DeCoM (Deepak Condenser Model) implementation –Code based on FORTRAN language. –Model works for transient and steady state conditions Steady state results are produced, to compare against 1D EXCEL model. –Calculate condenser fluid quality, temperature values, and fluid – wall convection value. Radiator and wall temperatures are calculated by SINDA. –Input DeCoM in VAR 1 of SINDA, in order for the logic to be executed at every time step. 7 **Equations based on Governing Theory from previous slides. TFAWS 2011 – August 15-19, 2011

8. 8 DeCoM/EXCEL Internal – The above diagram shows the network of nodes in the solution (code). EXCEL/DeCoM Implementation: Nodal Network Nodal Network Fluid Boundary Nodes Radiator Nodes Wall Nodes Fluid – Wall Conductor These temperatures and conductor values are calculated by EXCEL/DeCoM Wall – Rad Conductor TFAWS 2011 – August 15-19, 2011

9. EXCEL/DeCoM Implementation: Calculations Flow Chart 9 TFAWS 2011 – August 15-19, 2011 2-Phase Fluid Subcooled Liquid Solve for, φ i (as shown in Equation Slides) YESNO Initial Conditions i= 1, N Read Input Values Determine Fluid Stage Calculate Fluid to Wall Heat Transfer Value Calculate Fluid Parameters Output Fluid Parameters

10. TTH (Triem T. Hoang) Implementation TTH Description –NASA SBIR (Small Business Innovation Research) task development software –A LHP system solver (CC, Evap, Cond, L/V Lines). –Compiled library for use in SINDA. Appropriate for transient and steady state cases –TTH condenser is part of an overall LHP model code. Condenser section of the code was called as a subroutine for specific computations. Independently of other components. Implementation –Used as a validation tool against EXCEL/DeCoM implementation. –Output steady state results only. Restricted to steady state in order to compare with EXCEL implementation. –Calculates fluid temperatures, quality and heat transfer value between fluid and wall. SINDA calculates radiator temperatures. 10 TFAWS 2011 – August 15-19, 2011

11. FloCAD Implementation 11 FloCAD – FloCAD with FLUINT calculates entire network with fluid nodes, wall nodes, and radiator nodes as one network. – DeCoM calculates fluid node parameters based on wall node conditions (which are based on radiator nodes) – Third data point for comparison to TTH & EXCEL/DeCoM Implementations for 1D. Implementation – Initial and boundary conditions similar to DeCoM/EXCEL and TTH. – Lockhart-Martinelli correlation option used Plenum STUBE MFRSET Junction TIE Wall node Conductor Thermal Desktop – FloCAD network Radiator node Fluid node TFAWS 2011 – August 15-19, 2011

12. Introduction Develop/Exercise 1D Computer Codes –DeCoM –TTH –FloCAD Compare 1D Results Validate against 2D Test Case Integrate into ATLAS Instrument Model Conclusion –Problems Encountered/ Lessons Learned –Summary –Future Work Outline 12 TFAWS 2011 – August 15-19, 2011

13. Tsat = -4 CPower = 216 W Tsat = 16CPower = 216 W Tsat = 23CPower = 142 W 13 Results and Comparison – 1D: Analysis Case Results and Comparison – 1D: Analysis Case Radiator Condenser 1D ATLAS Radiator ATLAS Radiator: The routing and the radiator is represented, in order to create a simplified 1D model (as shown adjacently) (ATLAS radiator was unfolded with the condenser to create a 1D model ) TFAWS 2011 – August 15-19, 2011

14. Results and Comparison – 1D: Quality Vs. Temperature (T sat = -4 C) 14 TFAWS 2011 – August 15-19, 2011

15. Results and Comparison – 1D: Quality Vs. Temperature (T sat = 16 C) 15 TFAWS 2011 – August 15-19, 2011 DeCoM 16 TL DeCoM 16 XL

16. Results and Comparison – 1D: Quality Vs. Temperature (T sat = 23 C) 16 FloCAD/DeCoM/EXCEL have similar results TFAWS 2011 – August 15-19, 2011

17. Log Scale of G value comparison between DeCoM and TTH TFAWS 2011 – August 15-19, 2011 17 h (W/m 2 K) HX1LEG() x, quality h (W/m 2 K) -> G (W/K) SINDA G values printed out from TTH LHP Condenser functions. Results and Comparison – 1D: TTH Justification Results and Comparison – 1D: TTH Justification PIPE2P routine x, quality

18. Results and Comparison – 1D: Summary 18 The hand calculated length is an estimate at which all input power would be rejected. DeCoM/EXCEL and FloCAD results are close to hand calcs in comparison to TTH condenser method. Results show that TTH condenses much earlier than other methods. TTH code calculates the quality based on a G value from empirical data (6000 W/m 2 K, for Vapor). DeCoM and FloCAD calculate the quality based on a G value from the Lockhart-Martinelli correlation. FloCAD seems to use more CPU time. DTIMEF chosen by SINDA * User must be familiar with run settings, in order to decrease the CPU time. Once the modifications were made, CPU time was ~8.0 seconds. DeCoM method is both accurate and fast. TFAWS 2011 – August 15-19, 2011

19. Outline Introduction Developed/Exercised 1D computer codes –DeCoM –TTH –FloCAD Compare 1D Results Validate against 2D Test Case Integrate into ATLAS Instrument Model Conclusion –Problems Encountered/ Lessons Learned –Summary –Future Work 19 TFAWS 2011 – August 15-19, 2011

20. GLAS DM LHP 20 GLAS DM LHP Test Case Thermal Desktop Model 48” 31” OD=0.127” Fluid = Propylene Wall to Radiator I/F: Width = ¾”, NuSil Test # Power (W) Tsat ( o C) Tsink ( o C) 11206.5-100.0 21247.2-100.0 – 1/8” Al radiator – 3 mil Kapton on front and blankets on back. Model Correlation – 2D: GLAS LHP Test Case & Setup Model Correlation – 2D: GLAS LHP Test Case & Setup NOTE: Test values, and its results have been extracted from the document: GLAS Final Test Report of DM LHP TV Testing – Temperature sensor location (data point from which T LL was measured.) Liquid Line TFAWS 2011 – August 15-19, 2011

21. 21 DeCoM implementation – Approximate length of the condenser was used, based on scaling, as shown in previous slide. – Liquid line was also approximated to be starting from the T LL sensor Location. – Only the condenser outlet temperature was compared, due to the lack of temp. sensor data. Test data vs. DeCoM : steady state results – m FLOW *Cp*ΔT avg equates to ~1.9W, which may be the result of parasitic heat leak from the system. (1.9W is the amount of subcooling greater then the test data) – Modified power shows the temperature differences are less then a 1⁰C. – Possible factors for this heat leak, resulting in power/temperature differences Mechanical support structure. Transport lines insulation (modeled assumed to be perfectly insulated) GLAS Condenser Test Results vs. DeCoM Results Power (W) Tsat (C) Tsink (C) TEST LL TEMP (C) DeCoM LL TEMP (C) 1206.5-100.0-23.0-20.49 1247.2-100.0-20.0-17.38 Model Correlation – 2D: Results Model Correlation – 2D: Results ΔT avg = ~2.6C Modified (W) o C (118) -22.23 (122) -19.05 TFAWS 2011 – August 15-19, 2011

22. Outline Introduction Developed/Exercised 1D computer codes –DeCoM –TTH –FloCAD Compare 1D Results Validate against 2D Test Case Integrate into ATLAS Instrument Model Conclusion –Problems Encountered/ Lessons Learned –Summary –Future Work 22 TFAWS 2011 – August 15-19, 2011

23. Requirements for ATLAS model integration –Source code available for distribution and/or modification –Must not be detrimental to model runtime. –Method validated against test data and hand calculations. Selected method – TTH is not easily distributable or modifiable. Based on the work performed (explicitly for condenser, and 1D model) further validation of the condenser subroutine is required. – FloCAD take longer to calculate. If model is not well configured, it may take longer, else the difference is shown in previous 1D analysis slide. One of the drawbacks, is that it requires a license  DeCoM is distributable, accurate and fast. Therefore, DeCoM was chosen to be used as the code to predict the ATLAS laser radiator performance. 23 Integrate into ATLAS Instrument Model: Method Selection Integrate into ATLAS Instrument Model: Method Selection TFAWS 2011 – August 15-19, 2011

24. 24 ATLAS radiator thermal design –Size the radiator (Lowest T Laser, Highest Q Laser, Hot Environment) –Size the radiator heater (Highest/Lowest Q Laser, Cold Environments) Heater is sized to prevent condenser fluid from freezing. Integrate into ATLAS Instrument Model: Method Integration Integrate into ATLAS Instrument Model: Method Integration Condenser line Radiator Inlet Outlet NuSil I/F between pipe and radiator. ** Condenser routing is preliminary 39.3” 68.7” Al HC Panel Cond L = 325”, OD = ¼ “ 2” x 2” Nodes TFAWS 2011 – August 15-19, 2011

25. 25 Integrate into ATLAS Instrument Model: Temperature Maps Integrate into ATLAS Instrument Model: Temperature Maps Test Case: -4 C / 212 W Lowest T Laser, highest Q Laser Hot Beta 0 o Currently no gradient requirements are set. Temperature maps are produced for STOP analysis purposes. Orbit Day Orbit Shadow Exit Temperature, C A’ 1A’ A 1A 2A Subcooling cancelation occurs when some amount of heat leaks from the vicinity of 2-phase into subcooling region. Points on the maps, represent phase change (A,A’) and subcooling cancelation (1A,2A, 1A’) locations. Points are graphically represented in the next slides.

26. 26 Integrate into ATLAS Instrument Model: Quality vs. Temperature (T SAT = -4.0 C, 212W) Integrate into ATLAS Instrument Model: Quality vs. Temperature (T SAT = -4.0 C, 212W) A 1A 2A A’ 1A’ Radiator experiences both shadow and day environments in HB00 orbit. (below is the graphical representation of HB00 orbit) Shadow (OS) Day (OD) Vehicle TFAWS 2011 – August 15-19, 2011

27. 27 B 1B 2B 3B Integrate into ATLAS Instrument Model: Quality vs. Temperature (T SAT = 16.0 C, 212W) Integrate into ATLAS Instrument Model: Quality vs. Temperature (T SAT = 16.0 C, 212W) Highest Q Laser, CB90 for cold environments. Subcooling cancelation points occur due to heat leak from the adjoining 2-Phase section of the condenser line. Condenser Length (in) B 2B 1B 3B TFAWS 2011 – August 15-19, 2011

28. 28 C 1C 2C Integrate into ATLAS Instrument Model: Quality vs. Temperature (T SAT = 23.0 C, 142W) Integrate into ATLAS Instrument Model: Quality vs. Temperature (T SAT = 23.0 C, 142W) Lowest Q Laser,CB90 for cold environments. 2-phase section for this case is minimal, therefore the subcooling temperature increases significantly (at noted locations) Condenser Length (in) C 1C 2C TFAWS 2011 – August 15-19, 2011

29. 29 ATLAS Radiator Heat Data – Tabular data shows that physics of the radiator is satisfied. All energy is balanced. – 2P power does not match the input power – In a phase change (2P to liquid), some amount of heat from liquid phase (node) is leaked back into the 2P (node), and there is a decrease or increase in 2P power depending on the direction of the leak. Integrate into ATLAS Instrument Model: Radiator Heat Imbalance Integrate into ATLAS Instrument Model: Radiator Heat Imbalance ( - ) Heat Leaving Radiator ( + ) Heat Entering Radiator T-4C (Orbit Shadow Exit) 212W HB00 T-4C (Orbit Day) 212W Condenser 2P (two-phase)212W Condenser 2P210W Subcooled Liquid21 W Subcooled Liquid15 W ATLAS8W 2W SAP338WSAP363W SC Backload7W 7W SPACE-585WSPACE-596W Heat Imbalance0W 0W T16C 212W (CB90)T23C 142W (CB90) Condenser 2P220W Condenser 2P147W Subcooled Liquid45 W Subcooled Liquid42 W ATLAS3W 5W SAP346WSAP272W SC Backload0W 0W SPACE-615WSPACE-466W Heat Imbalance0W 0W Solar, Albedo, Planet Shine TFAWS 2011 – August 15-19, 2011

30. DeCoM integration into ATLAS –The CPU time difference of before and after the Code integration was negligible, difference is less then 1sec. Results –Minimum liquid line temperature Results help size the radiator heater power required in order to keep ammonia from freezing. The last column in the table indicates an approximate amount of heat rejected to the radiator in the subcooled phase. 30 Temperature Case Liquid Line Temperature ( o C) Q (W) -4.0 C (least condensed)-32.0021.00 -4.0 C (most condensed)-24.0015.00 16.0 C-39.0046.00 23.0 C-60.0048.00 Integrate into ATLAS Instrument Model: Summary Integrate into ATLAS Instrument Model: Summary TFAWS 2011 – August 15-19, 2011

31. Outline Introduction Developed/Exercised 1D computer codes –DeCoM –TTH –FloCAD Compare 1D Results Validate against 2D Test Case Integrate into ATLAS Instrument Model Conclusion –Problems Encountered/ Lessons Learned –Summary –Future Work 31 TFAWS 2011 – August 15-19, 2011

32. Problems Encountered / Lessons Learned DeCoM / EXCEL –Property calculations in EXCEL differed from DeCoM Property vs. temperature plots had to be generated to obtain equation of the lines. –Radiator temperatures were modeled as wall temperatures. Had to create iterative equations to calculate radiator temperatures. –Reading Thermal Desktop values Reading/editing node temperatures, conductor heat rates, and modify the conductance values, was learned. –Printing quality and temperature values A “WRITE” statement (FORTRAN Language) was implemented. – Temperature and quality results did not match EXCEL EXCEL property Vs. temperature plot equations were applied to the code. FORTRAN programming language was learned from this exercise. 32 TFAWS 2011 – August 15-19, 2011

33. 33 TTH Problems Encountered – Integrating with the Thermal Desktop model Full understanding of the software’s limitations was required. A library file was inserted to call condenser subroutine for fluid calculations FloCAD Problems Encountered – Nodal Network was unclear An understanding of tanks and plenums was required. – Correlation method similar to that of EXCEL and FORTRAN Parameter to call the Lockhart-Martinelli method had to be applied – CPU time usage was too high (as shown in the 1D results slide) User input is required, and must be familiar with run settings in order to decrease the CPU time. Problems Encountered / Lessons Learned TFAWS 2011 – August 15-19, 2011

34. 34 Summary Understand and develop a condenser Model set of equations Compare three possible solution methods for a 1D simplified radiator and condenser (1D flow). Correlate the DeCoM method against test data from GLAS LHP. Implement the DeCoM into ATLAS thermal model and provide radiator temperature predictions. TFAWS 2011 – August 15-19, 2011

35. Future Work DeCoM Future Possibilities –Package the code as a subroutine. Including user manual for use on other projects. Better integration with generic SINDA models. Return of USER requested internal Parameters. (e.g. quality) –Allow user defined node lengths (currently only 2”) –Investigate DeCoMs response to quick transient changes in environment or due to load –Check validity of FloCAD and TTH against the 2D test case. –Correlation against various other LHP test data, will validate the method even further, making it more reliable. Properties other then Ammonia needs to be built-into the code. –Alternate correlation schemes to Lockhart-Martinelli –Integrate option for multiple condenser lines 35 TFAWS 2011 – August 15-19, 2011

36. 36 Condenser effects on the Radiator Enjoy this small clip of DeCoM in its workings. TFAWS 2011 – August 15-19, 2011

37. BACKUP Symbols & Acronyms 37 SubscriptsSuperscriptsAcronyms SINDA: Systems Improved Numerical Differencing Analyzer) FLUINT: Fluid Integrator) SC:SubCooled LL:Liquid Line LHP:Loop Heat Pipe STOP:Structural-Thermal- Optical Performance TFAWS 2011 – August 15-19, 2011