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### DeCoM Validation

Outline

Presented ByDeepak Patel

NASA/ Goddard Space Flight Center

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

NASA Langley Research CenterNewport News, VA

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

- 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

- 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

- 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

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 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

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

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 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
- 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

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

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 (Tsat = -4 C)

TFAWS 2011 – August 15-19, 2011

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 (Tsat = 23 C)

FloCAD/DeCoM/EXCEL have similar results

TFAWS 2011 – August 15-19, 2011

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

- 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

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

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

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

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

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

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

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

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

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

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)

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

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

- 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

- 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

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

- 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

- 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

Condenser effects on the Radiator

Enjoy this small clip of DeCoM in its workings.

TFAWS 2011 – August 15-19, 2011

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

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