investigations of physical processes in microgravity
TRANSCRIPT
National Aeronautics and Space Administration
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Investigations of Physical Processes in Microgravity
Relevant to Space Electrochemical Power Systems
Dr. Vadim F. Lvovich, Dr. Robert Green, and Ian Jakupca
NASA Glenn Research Center
Cleveland, OH 44135
6th International Symposium on Physical Sciences in Space, Kyoto, Japan
September 15, 2015
National Aeronautics and Space Administration
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Regenerative Fuel Cells
• Develop Components and Integrated Systems
– kW-size Fuel Cell stacks with advanced water removal
– Balanced-pressure passive liquid-feed, vapor-feed or hybrid Electrolyzer
– Advanced MEAs for both Fuel Cells and Electrolyzers
– Compact, efficient balance-of-plant components
– Advanced manufacturing processes for high-pressure operation and reduced mass,
volume and cost
– Discrete Fuel Cell and Electrolyzer systems to optimize efficiency of each
Regenerative Fuel Cell with Array
Electrolyzer
Fuel Cell
H2 O2H2O
kWe
kWe
Main Power Bus
Photovoltaic Array
kWe
Electrical
Loads
Regenerative Fuel Cell
Electrolyzer Stack
FC
Stack
MEA
BOP
Components developed to
create system
Non-Flow-Through Fuel Cell
Shuttle Flow-Through Fuel Cell
Heat
2
Regenerative Fuel Cell with Array
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Shuttle
“Active BOP”
Alkaline
“Active BOP”
PEM
GlennResearch Center
JohnsonSpace Center
17 - 20 psia
BULKHEAD FITTING
TAP WATER
T FITTING
ACCUMULATOR
PTTP
PT
PT5
PT6
TP
TP5
TP6TP PT
PT3TP3TP PT
M1RV1
COOLANT
OXYGEN PURGE 3/4" **
AS4395-12 Male flare
fitting
OXYGEN* Supply to 3/8" **
AS4395-06 Male flare fitting
PR1
PR2
FC1
WT1
PT
PT1
PT2
PRODUCT WATER 1/4"
AS4395-04 Male flare fitting
19 psia +/- 3CATHODE
HYDROGEN* Supply to 1/4" **
AS4395-04 Male flare fitting
TP
TP1
TP2
SV1
SV2
ANODE
FACILITYPOWERPLANT
T1Accumulator
with bellows
MV1
H1
HYDROGEN PURGE 1/2" **
AS4395-08 Male flare fitting
SV3
RV2
TP PT
SV4
AIR
DI WATER
HYDROGEN
LEGEND PRESSURE REGULATING VALVE
SOLENOID VALVE (NO)
SOLENOID VALVE (NC) WATER SEPARATOR
FILL PORT
CIRCULATION PUMP
PRESSURE TRANSDUCERPPT
TEMPERATURE PROBETTP
COOLANT PUMP
MIXING VALVEELECTRIC HEATER
HEAT EXCHANGER HEAT EXCHANGERRELIEF VALVE
PT4TP4
M2
WT2
HX2
MV2
100 - 275 psia
Temp > 10 C
21 psia +/- 2
19 psia +/- 3
19 psia +/- 3
21 psia +/- 3
17 psia
21 psia +/- 2 100 - 275 psia
Temp > 10 C
17 - 20 psia
50 - 56 deg C
17 -20 psia
44 - 50 deg C
3/4" Primary Coolant Loop
30 psia +/- 2
32 psia +/- 2
45 psia +/- 2
PT
PT
PT7
PT8
M3
Secondary Coolant Loop
HX1
PRIMARY COOLANT INLET 3/4"
AS4395-12 Male flare fitting
PRIMARY COOLANT OUTLET 3/4"
AS4395-12 Male flare fitting
25 +/- 10 deg C
50 - 56 deg C
44 - 56 deg C
17 - 20 psia
PRODUCT WATER 1/4"
AS4395-04 Male flare fitting44 - 56 deg C
Hydrogen pressure manifold
Oxygen pressure manifold
Flow-Through Flow-Through
GlennResearch Center
“Passive BOP”
PEM
Flow-Through
“Passive BOP”
PEM
GlennResearch Center
an
ode
ca
thode
H2O
MEA
H2O
H2 O2
H2O
H2O
coo
lan
t
hyd
roph
ilic m
em
bra
ne
an
ode
ca
thode
H2O
MEA
H2O
H2 O2
H2O
H2O
coo
lan
t
hyd
roph
ilic m
em
bra
ne
an
ode
ca
thode
coo
lan
t
MEA
H2O
injector/ejector
passive water
separator
H2 O2
H2OH2O
O2
O2 / H2O
an
ode
ca
thode
coo
lan
t
MEA
H2O
injector/ejector
passive water
separator
H2 O2
H2OH2O
O2
O2 / H2O
Non-Flow-Through
Active Mechanical Component
(pump, active water separator)= Passive Mechanical Component
(injector/ejector, passive water separator)=
NASA Fuel Cell Technology Progression
Active coolant
pump
(coolant loop
not shown)
Active coolant
pump (coolant
loop not shown)
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PEM Electrolysis Systems
4
Liquid water Anode Feed• water fed on anode side, dragged to cathode side
• greatest electrical efficiency
• requires 2 phase separators, 2 pumps
• used by the Navy
Liquid water Cathode Feed• water fed on cathode side, diffuses to anode
• reduced electrical efficiency
• requires 1 phase separator, 1 pump
• used in OGA (ISS)
Highest rate and efficiency; most complex Lower rate, simpler system
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Physical Science ISS Flight Experiments
• Space Fuel Cell and Electrolysis systems management require separation
of gas/liquid multiphase streams in microgravity
• In this section, we present a quick overview of results from 2 ISS Physical
Science flight experiments
– Involves multiphase flows (i.e. gas/liquid flows)
– Has analogies to electrochemical work in microgravity
– Demonstrates maturity level needed to develop electrochemical flight
experiments of similar complexity
• Microgravity Fluid Physics discipline
– Boiling and condensation experiment
• MABE - Microheater Array Boiling Experiment
– Capillary flows experiment
• CCF – Capillary Channel Flow
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ISS Boiling Flight Experiments
Boiling eXperiment Facility (BXF) – 2011
• BXF included two separate pool boiling investigations:
– Microheater Array Boiling Experiment (MABE)
– Nucleate Pool Boiling Experiment (NPBX)
• Improved understanding of local boiling heat transfer
mechanisms & critical heat flux in microgravity for nucleate
and transition pool boiling.
• Detailed measurements of bubble growth, detachment and
subsequent motion of single and merged (larger) bubbles
• Developed a criteria for Boiling Transition– Buoyancy Dominated Regime (BDB)
• Heat transfer by bubble growth and departure
• Heat flux increases with gravity
– Surface Tension Dominated Regime (SDB)
• Dominated by the presence of a non-departing primary bubble
• Effect of residual gravity is very small
– Transition Criteria based on Capillary Length
• Enhanced the development of two-phase thermal
management systems, which provide isothermal control with
reduced radiator area and mass.
• Pool boiling studies are the first critical step to understanding
flow boiling in 0-g.
• A combined condensation and flow boiling experiment is
scheduled for 2018.
(Top) Paulo Nespoli installing BXF in MSG.
(Middle left) Coalescence of vapor bubbles
on NPBX wafer. (Middle right) Subcooled
nucleate boiling in g. The MABE
microheater array is colorized with actual
heat flux data. (Bottom) Transition of boiling
Heat Flux as a function of acceleration
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0
0
W/c
m2
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Key Result from MABE Flight Investigation:
Heat Transfer Model for Varying g-levels
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Heat flux vs. gravitational acceleration for a given TemperatureRaj, Kim, & McQuillen, Trans ASME, 2012.
• Two regimes identified– Buoyancy Dominated Regime (BDB)
– Surface tension Dominated Regime (SDB)
• Regime boundary characterized as a large
“jump” and is defined by Lh/Lc = 2.1. – where Lh = width of square heater
– and Lc = capillary length.
• Magnitude of jump requires further work.
• Slopes for SDB and BDB regimes:
ONBCHF
ONBW
TT
TTT
*
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Boiling Curves Under Varying Gravity Conditions
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Single Phase
(natural convection)
Nucleate boiling
CHF
Film Boiling
Key results from ground-based testing:
• Boiling in microgravity is possible.
• Bubble departure diameters in µg are
greater than 1 g, but smaller than
predictions
• CHF are also lower in µg than 1g but
higher than correlations.
• Surface tension and contact angle affect
boiling behavior.
• Bond number (Bo – relative strength of
body forces to surface tension) alone
cannot be used for correlations (regime
indicator).
Compendium of ground-based test results by Kim, Univ. of Maryland
)( fW TThq
2)( aLBo VL
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Example Boiling Results in Low and High-g Conditions
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Capillary Channel Flow Experiments on the ISS
ESA PI: Prof. Michael Dreyer, ZARM
Co-I: Prof. Mark Weislogel, Portland State University
PM: Robert Hawersaat, NASA GRC
PS: Robert Green, NASA GRCObjectives
– To enable design of spacecraft tanks that can supply gas-free
propellant to spacecraft thrusters, directly through capillary
vanes, significantly reducing cost and weight, while improving
reliability.– Experiment #1 (EU#1)
• Determine critical flow-rates (choking) in the capillary-inertial regime as a function of channel length for true channel and half channel.
• Probe the nature of critical behavior by introducing wave oscillation of variable amplitude and frequency for both channel configurations and variable lengths.
– Experiment #2 (EU#2)• Determine critical flow rates (choking) in the capillary-inertial,
visco-capillary, and overlap regimes for wedge channels as a function of channel length.
• Probe the nature of bubble transport, migration, and phase separation as a function of flow rate, channel length, bubble diameter and frequency.
Topics
– Experimental studies of open capillary channel flow stability.– Two experiment units with three different channel geometries.– Steady, oscillating, unsteady, and two-phase flow conditions.– Total of 50 days of effective experimental time aboard the
ISS.– Main ground station located at ZARM in Bremen, Germany.– Interactive access to the ISS for controlling and data
download.
Motivation: capillary channel flow in surface tension tanks
Capillary channels with free liquid surfaces are widely used
for propellant management in surface tension tanks. Vanes
provide channels of various shapes to transport the liquid to
the outlet. The free surfaces have to withstand the pressure
difference and prevent gas ingestion; the stability is of
significant importance for the spacecraft propulsion system.
Experimentally investigated geometries of capillary channels
Two experiment units (EU#1, EU#2) provide three different
channel geometries, each with one or two free liquid
surfaces. The plates are manufactured of glass for camera
observation and surface image analysis; a=5 mm, b=25
mm, H =30 mm, α=7.9o, variable length l =0...48 mm.
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CCF Results:
Liquid-Gas Phase Separation Regime Maps• Data reduction indicates well-defined boundaries between full and partial (or no)
gas/liquid phase separation.
• Two example regime maps are shown below for two
bubble generation frequencies ( Qg = 𝑓𝑉𝑏𝑢𝑏𝑏𝑙𝑒 ).
Flow conditions for 100% bubble separation in an open wedge channelFrom Jenson et. al., Int. J. Multiphase Flow, 2014
The Capillary Channel Flow (CCF) test section is an inverted interior corner geometry with a triangular cross-section.
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NASA Fuel Cell Stack Ground Orientation Testing
Two orientations of the stack in 1-g gravity with respect to water flow
• “baseline” (preferred for water removal)
• “inverted” (impeding water removal)
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NASA Fuel Cell Stack Ground Orientation Testing
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Conclusions
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• Understanding of gas-liquid separation processes are very important for
effective management of advanced regenerative fuel cell systems
• Gas-liquid separation process patterns are different in 1-G and 0-G
• Boiling experiment (q vs. T) in microgravity, has analogy to electrochemical
work (I vs. V) with non-departing primary bubble resulting in both higher
wall temperature (TW) and higher voltage (V) for same heat flux (q) and
current (I).
• Capillary channel flow with “free surface” can be used for passive gas-
liquid multiphase separation in 0-G.
• Fuel cell stack orientation in 1-G experiments affects long term power
performance