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TFAWS Paper Session. Analytical Approach in DeCoM. 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 Matt Garrison Dr . Jentung Ku

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analytical approach in decom

TFAWS Paper Session

Analytical Approach in DeCoM

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
  • Matt Garrison
  • Dr. Jentung Ku
  • Tamara O'Connell
  • Thermal Engineering Branch at Goddard Space Flight Center

TFAWS 2011 – August 15-19, 2011

outline
Outline
  • Introduction
  • Governing Equations
  • Develop 1D Computer Code
    • DeCoM
  • Conclusion
    • Summary

TFAWS 2011 – August 15-19, 2011

introduction purpose
Introduction:Purpose
  • Purpose
        • To develop a model which efficiently and accurately simulates LHP Condenser
    • Understand basic principles of two-phase flow
        • Correlation method for two-phase convection value
        • Governing equations to obtain quality change

TFAWS 2011 – August 15-19, 2011

introduction introduction to lhp
Introduction:Introduction to LHP
  • Compensation Chamber, QCC
    • Excess fluid is stored here, from which the LHP can increase its performance by accessing or storing the excess fluid.
  • Evaporator, QE
    • Liquid from the bayonet is flown into the wick where it is converted to vapor, from the heat that is conducted from the instrument.
  • Vapor Line
    • Vapor from evaporator is transferred to the condenser, adiabatically.

Bayonet Tube

  • Liquid Line, LL
    • Subcooled liquid from the condenser is returned to the evaporator.
  • Condenser – QC (Condenser), QSC (Subcooled)
    • QC is the amount of heat rejected when the fluid is in two-phase, and QSC is for condensed Subcooled liquid section (1-phase fluid).

TFAWS 2011 – August 15-19, 2011

introduction condenser basics
Introduction:Condenser Basics
  • Condenser:
    • Vapor generated travels from vapor transport line and enters the heat exchanger (condenser).
    • Vapor enters as saturated vapor and phase change occurs, after which it is condensed to liquid.

Condenser and Subcooler

TFAWS 2011 – August 15-19, 2011

outline1
Outline
  • Introduction
  • Governing Equations
  • Develop 1D Computer Code
    • DeCoM
  • Conclusion
    • Summary

TFAWS 2011 – August 15-19, 2011

slide8

Governing Equations:

Control Volume Analysis

Node, Outlet

Node, Inlet

FLUID

WALL

T

(oC)

Control Volume for which Equations are formulated

Superheated Vapor

RADIATOR

Subcooled Liquid

Pressure = constant

  • The thermodynamic plot above describes the regions (arrows) that the equations are derived for.
  • A fluid is defined by its any two thermodynamic property (e.g. temperature and pressure)
  • Radiative Tsink

T1 = T2

2

1

Two-Phase Envelope

Sat’d Liquid

and

Sat’d Vapor

  • Conservation of Energy
  • Condenser source code is based on the Conservation of Energy equation. Applied on each node.

v (m3/kg)

TFAWS 2011 – August 15-19, 2011

slide9

Governing Equations:

Control Volume Analysis

IF

FLUID

WALL

TRADIATOR

  • Inlet conditions are known
  • Equations can vary depending upon the state of the fluid (2φ or SC), as shown above.
  • Lockhart-Martinelliequations are used to solve for the G2φvalue.
  • 2-Phase section
  • Subcooled section

TFAWS 2011 – August 15-19, 2011

slide10

Governing Equations:

Fluid flow regimes

  • Flow regimes of the fluid inside a tube
    • Two-Phase Lockhart-Martinelli calculations are based on an Annular Flow regime
    • This is a general case in all simple condensers, and a safe assumption

TFAWS 2011 – August 15-19, 2011

slide11

Governing Equations:

2φ Lockhart-Martinelli Calculations

  • Calculate , two-phase heat transfer coefficient multiplier.
  • Lockhart – Martinelli correlation
    • An empirically formulated two-phase multiplier equation
    • X – Lockhart-Martinelli parameter

Wall

Fluid

Vapor

  • Lockhart-Martinelli correlation is based upon an annular flow regime.

TFAWS 2011 – August 15-19, 2011

slide12

Background Theory / Governing Equations: 2φ Heat Transfer Calculations

  • Solving for the convection value using Lockhart-Martinelli multiplier

T

(oC)

  • Thermodynamic Plot highlights the region being analyzed (arrow).
  • The plot on the right shows behavior of the convection value in relation to the fluid quality for saturation temperature at -4 degC @ 216W.

Superheated Vapor

Subcooled Liquid

99.5

Pressure = constant

T1 = T2

2

1

Two-Phase Envelope

Sat’d Liquid and

Sat’d Vapor

v (m3/kg)

TFAWS 2011 – August 15-19, 2011

slide13

Background Theory / Governing Equations: Liquid Phase Heat Transfer Calculations

T

(oC)

  • Equations here are based upon 1-phase, subcooled liquid. Using the flow characteristics, either turbulent or laminar, the heat transfer coefficient is calculated.
  • Thermodynamic plot above shows (the blue arrow) section being analyzed.

Superheated Vapor

Subcooled Liquid

Pressure = constant

T1 = T2

2

1

Two-Phase Envelope

Sat’d Liquid and

Sat’d Vapor

v (m3/kg)

TFAWS 2011 – August 15-19, 2011

outline2
Outline
  • Introduction
  • Governing Equations
  • Develop 1D Computer Code
    • DeCoM
  • Conclusion
    • Summary

TFAWS 2011 – August 15-19, 2011

decom implementation
DECOM Implementation
  • DeCoM (Deepak Condenser Model) Implementation
    • Code based on FORTRAN language.
    • Model works for transient and steady state conditions
      • Response time to transient is part of future work.
    • 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

decom implementation nodal network
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 Internal
    • The above diagram shows the network of nodes in the solution (code).

TFAWS 2011 – August 15-19, 2011

decom implementation calculations flow chart
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

outline3
Outline
  • Introduction
  • Governing Equations
  • Develop 1D Computer Code
    • DeCoM
  • Conclusion
    • Summary

TFAWS 2011 – August 15-19, 2011

slide19

Summary

  • Alternative LHP Condenser modeling method
    • Purpose of explicit condenser modeling
  • Understand condenser governing equation
    • Implement two-phase correlation method
    • Fluid to Wall interaction modeling
  • Developed FORTRAN code based on governing equations.

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