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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. Acknowledgments . Hume Peabody Matthew Garrison Dr . Jentung Ku

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decom validation

TFAWS Paper Session

DeCoM Validation

Presented ByDeepak Patel

NASA/ Goddard Space Flight Center

Thermal & Fluids Analysis WorkshopTFAWS 2011August 15-19, 2011

NASA Langley Research CenterNewport News, VA

acknowledgments
Acknowledgments
  • Hume Peabody
  • Matthew Garrison
  • Dr. Jentung Ku
  • Tamara O'Connell
  • Thermal Engineering Branch at Goddard Space Flight Center

TFAWS 2011 – August 15-19, 2011

outline
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

introduction thermal analysis tools
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.

TFAWS 2011 – August 15-19, 2011

introduction analysis cases
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
  • **Cases developed for test-bed/development purposes – not design

ATLAS Radiator:

The routing and the radiator are represented, in order to create a simplified 1D model (as shown below)

6 in

372 in

Condenser

Radiator

ATLAS Laser Scenarios

outline1
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

TFAWS 2011 – August 15-19, 2011

excel decom implementation
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.
  • **Equations based on Governing Theory from previous slides.

TFAWS 2011 – August 15-19, 2011

slide8

EXCEL/DeCoM Implementation:Nodal Network

These temperatures and conductor values are calculated by EXCEL/DeCoM

Fluid Boundary Nodes

Fluid – Wall Conductor

Wall Nodes

Wall – Rad Conductor

Radiator Nodes

Nodal Network

  • DeCoM/EXCEL Internal
    • The above diagram shows the network of nodes in the solution (code).

TFAWS 2011 – August 15-19, 2011

excel decom implementation calculations flow chart
EXCEL/DeCoM Implementation: Calculations Flow Chart

Initial Conditions

i= 1 , N

Read Input Values

YES

NO

Determine Fluid Stage

2-Phase Fluid

Subcooled Liquid

Calculate Fluid to Wall Heat Transfer Value

Solve for, φi (as shown in Equation Slides)

Calculate Fluid Parameters

Output Fluid Parameters

TFAWS 2011 – August 15-19, 2011

tth triem t hoang implementation
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.

TFAWS 2011 – August 15-19, 2011

flocad implementation
FloCAD Implementation
  • 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

Thermal Desktop – FloCAD network

MFRSET

STUBE

Fluid node

Junction

TIE

Wall node

Conductor

Radiator node

TFAWS 2011 – August 15-19, 2011

outline2
Outline
  • 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

TFAWS 2011 – August 15-19, 2011

slide13

Results and Comparison – 1D:

Analysis Case

  • Tsat = -4 C Power = 216 W
  • Tsat = 16C Power = 216 W
  • Tsat = 23C Power = 142 W

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 )

ATLAS Radiator

1D

Condenser

Radiator

TFAWS 2011 – August 15-19, 2011

results and comparison 1d quality vs temperature t sat 4 c
Results and Comparison – 1D:Quality Vs. Temperature (Tsat = -4 C)

TFAWS 2011 – August 15-19, 2011

results and comparison 1d quality vs temperature t sat 16 c
Results and Comparison – 1D:Quality Vs. Temperature (Tsat = 16 C)

DeCoM 16 TL

DeCoM 16 XL

TFAWS 2011 – August 15-19, 2011

results and comparison 1d quality vs temperature t sat 23 c
Results and Comparison – 1D: Quality Vs. Temperature (Tsat = 23 C)

FloCAD/DeCoM/EXCEL have similar results

TFAWS 2011 – August 15-19, 2011

slide17

Results and Comparison – 1D:

TTH Justification

PIPE2P routine

G values printed out from TTH LHP Condenser functions.

h (W/m2K)

HX1LEG()

x, quality

Log Scale of G value comparison between DeCoM and TTH

x, quality

PIPE2P routine

h (W/m2K) -> G (W/K)

SINDA

TFAWS 2011 – August 15-19, 2011

results and comparison 1d summary
Results and Comparison – 1D: Summary
        • 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/m2K, 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

outline3
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

TFAWS 2011 – August 15-19, 2011

slide20

Model Correlation – 2D:

GLAS LHP Test Case & Setup

31”

  • GLAS DM LHP Test Case

OD=0.127”

Fluid = Propylene

Wall to Radiator I/F:

Width = ¾”, NuSil

48”

  • 1/8” Al radiator
  • 3 mil Kapton on front and blankets on back.

Liquid Line

  • Temperature sensor location (data point from which TLL was measured.)

NOTE: Test values, and its results have been extracted from the document:

GLAS Final Test Report of DM LHP TV Testing

TFAWS 2011 – August 15-19, 2011

Thermal Desktop Model

GLAS DM LHP

slide21

Model Correlation – 2D:

Results

ΔTavg = ~2.6C

  • 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 TLL sensor Location.
    • Only the condenser outlet temperature was compared, due to the lack of temp. sensor data.
  • Test data vs. DeCoM : steady state results
    • mFLOW*Cp*ΔTavg 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)

Twall = -86.84 C

w/ 0.125” thickness

TFAWS 2011 – August 15-19, 2011

outline4
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

TFAWS 2011 – August 15-19, 2011

slide23

Integrate into ATLAS Instrument Model:

Method Selection

  • 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.

TFAWS 2011 – August 15-19, 2011

slide24

Integrate into ATLAS Instrument Model:

Method Integration

68.7”

** Condenser routing is preliminary

2” x 2” Nodes

Al HC Panel

39.3”

Radiator

Cond L = 325”, OD = ¼ “

NuSil I/F between pipe and radiator.

Inlet

Condenser line

Outlet

  • ATLAS radiator thermal design
    • Size the radiator (Lowest TLaser, Highest QLaser, Hot Environment)
    • Size the radiator heater (Highest/Lowest QLaser , Cold Environments)
      • Heater is sized to prevent condenser fluid from freezing.

TFAWS 2011 – August 15-19, 2011

slide25

Integrate into ATLAS Instrument Model:

Temperature Maps

  • Test Case: -4 C / 212 W
  • Lowest TLaser, highest QLaser Hot Beta 0o
  • Currently no gradient requirements are set. Temperature maps are produced for STOP analysis purposes.

Orbit Day

Orbit Shadow Exit

  • 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.

A

1A

A’

2A

1A’

Temperature, C

slide26

Integrate into ATLAS Instrument Model:

Quality vs. Temperature (TSAT = -4.0 C , 212W)

A’

A

  • Radiator experiences both shadow and day environments in HB00 orbit. (below is the graphical representation of HB00 orbit)

1A’

1A

2A

Shadow (OS)

Day (OD)

Vehicle

TFAWS 2011 – August 15-19, 2011

slide27

Integrate into ATLAS Instrument Model:

Quality vs. Temperature (TSAT = 16.0 C , 212W)

B

1B

3B

3B

B

1B

  • Highest QLaser ,CB90 for cold environments.
  • Subcooling cancelation points occur due to heat leak from the adjoining 2-Phase section of the condenser line.

2B

2B

Condenser Length (in)

TFAWS 2011 – August 15-19, 2011

slide28

Integrate into ATLAS Instrument Model:

Quality vs. Temperature (TSAT = 23.0 C , 142W)

  • Lowest QLaser ,CB90 for cold environments.
  • 2-phase section for this case is minimal, therefore the subcooling temperature increases significantly (at noted locations)

C

2C

C

1C

1C

2C

TFAWS 2011 – August 15-19, 2011

Condenser Length (in)

slide29

Integrate into ATLAS Instrument Model:

Radiator Heat Imbalance

Solar, Albedo, Planet Shine

  • ( - ) Heat Leaving Radiator
  • ( + ) Heat Entering Radiator
  • 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.

TFAWS 2011 – August 15-19, 2011

slide30

Integrate into ATLAS Instrument Model:

Summary

  • 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.

TFAWS 2011 – August 15-19, 2011

outline5
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

TFAWS 2011 – August 15-19, 2011

problems encountered lessons learned
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.

TFAWS 2011 – August 15-19, 2011

slide33

Problems Encountered / Lessons Learned

  • 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.

TFAWS 2011 – August 15-19, 2011

slide34

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

future work
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

TFAWS 2011 – August 15-19, 2011

slide36

Condenser effects on the Radiator

Enjoy this small clip of DeCoM in its workings.

TFAWS 2011 – August 15-19, 2011

backup symbols acronyms
BACKUPSymbols & Acronyms

Subscripts

Superscripts

Acronyms

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