Gibson, Marc A.

Jaworske, Donald A.

Sanzi, James L.

NASA Technical Reports Server

National Aeronautics and Space Administration 
www.nasa.gov 
Observations of Thermosyphon Flooding in 
Reduced Gravity Environments  
Donald A. Jaworske, Marc A. Gibson, James L. Sanzi 
1 
May 1-3, 2012 
https://ntrs.nasa.gov/search.jsp?R=20150010133 2019-08-31T07:54:23+00:00Z
National Aeronautics and Space Administration 
www.nasa.gov 
Planetary Applications of Fission Power  
• Several architecture studies have examined the use of Fission Power 
Systems (FPS) for the human exploration of the moon and Mars. 
 
2 
• For a 40 kWe installation, radiators 
would be needed to dissipate 
approximately 140 kWt of waste heat. 
• A 180 m2 radiator panel over 10 years 
would have 3.6 hits of sufficient kinetic 
energy to damage fluid flow. 
• The design solution to mitigate the risk 
of rupturing a fluid line is to utilize 
multiple heat pipes. 
– In the event of a micrometeoroid hit to a 
single heat pipe, only the fluid in the heat pipe 
is lost. 
• The design solution also includes high thermal 
conductivity composite facesheets to distribute 
heat across the radiator panel.  
National Aeronautics and Space Administration 
www.nasa.gov 
FPS Preliminary Reference Concept 
• A guide for technology 
development. 
• Power levels, 
temperatures, pressures, 
flow rates, and 
efficiencies become 
notional requirements. 
 
 
 
 
 
 
3 
National Aeronautics and Space Administration 
www.nasa.gov 
Heat Pipes Operating as Thermosyphons 
• Radiators equipped with thermosyphons 
spread and reject waste heat effectively. 
 
• With the aid of gravity, thermosyphons 
can be used within appropriate heat 
transfer limits. 
– The limit of most concern is the flooding limit. 
 
• Understanding these limits requires 
testing of thermosyphons in Reduced 
Gravity Environments (RGEs). 
– Drop towers 
– Parabolic flights 
– Sounding rockets 
 
• Parabolic flights provide the opportunity to 
achieve both lunar and Martian gravity 
environments. 
 
 
 
 
 
 
4 
National Aeronautics and Space Administration 
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Experiment Justification 
5 
• In the literature, it was found that the flooding limits of 
thermosyphons have never been tested in RGEs. 
 
• If existing flooding models were incorrect then the heat rejection 
system could be under-designed, leaving significant risk that the 
thermosyphons could reach their flooding limit. 
 
• Upon flooding, the reactor and power converters would have to be 
powered down. 
– A decrease in temperature would allow thermosyphon recovery. 
 
• After recovery, the fission power system may have to operate at a 
lower power level. 
 
National Aeronautics and Space Administration 
www.nasa.gov 
The Flooding Limit 
6 
• Heating in the evaporator vaporizes fluid 
which travels upward into the condenser. 
 
• Vapor condenses on the condenser wall 
and travels back down to the evaporator 
with the aid of gravity. 
 
• As heating increases, more vapor is 
formed and travels at a higher velocity up 
the pipe. 
 
• As more vapor condenses, the fluid 
thickness on the wall increases. 
 
• The increasing mass flow and shrinking 
vapor throat area create high shear 
between the vapor and the fluid. 
 
• This shear force overcomes the gravity 
force and the condenser floods. 
 
National Aeronautics and Space Administration 
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Experiment Setup 
7 
• Twelve 0.25” O.D. x 0.035” wall Ti/H2O 
thermosyphons 
 
• Individual evaporators heated electrically 
 
• Maximum heat input:  350 W/each 
 
• Forced air cooling w/aluminum-finned 
condensers 
 
 
• National Instruments 
PXI realtime DAC 
system 
 
• Labview programming 
 
• Laptop computer 
control 
 
 
 
 
National Aeronautics and Space Administration 
www.nasa.gov 
Predictions via the Bond Number 
8 
Faghri’s Correlation 
?̇?𝑄𝑚𝑚𝑚𝑚𝑚𝑚 = 𝐾𝐾ℎ𝑓𝑓𝑓𝑓𝐴𝐴𝑣𝑣[𝑓𝑓𝑔𝑔(𝜌𝜌𝐿𝐿 − 𝜌𝜌𝑉𝑉)]1 4� �𝜌𝜌𝑉𝑉−1 4� + 𝜌𝜌𝐿𝐿−1 4� �−2 
𝐾𝐾 = �𝜌𝜌𝐿𝐿
𝜌𝜌𝑉𝑉
�
0.14
𝑡𝑡𝑚𝑚𝑡𝑡ℎ2𝐵𝐵𝑂𝑂1 4� = 𝑅𝑅 𝑡𝑡𝑚𝑚𝑡𝑡ℎ2𝐵𝐵𝑂𝑂1 4�  
𝐵𝐵𝑜𝑜 = 𝐷𝐷 �𝑓𝑓(𝜌𝜌𝐿𝐿−𝜌𝜌𝑉𝑉 )𝑔𝑔 �12 
Tien and Chung 
?̇?𝑄𝑚𝑚𝑚𝑚𝑚𝑚 = 𝐶𝐶𝐾𝐾2ℎ𝑓𝑓𝑓𝑓𝐴𝐴𝑣𝑣[𝑓𝑓𝑔𝑔(𝜌𝜌𝐿𝐿 − 𝜌𝜌𝑉𝑉)]1 4� �𝜌𝜌𝑉𝑉−1 4� + 𝜌𝜌𝐿𝐿−1 4� �−2 
𝐶𝐶𝐾𝐾 = √3.2tanh⁡(0.5𝐵𝐵𝑜𝑜1 4� ) 
National Aeronautics and Space Administration 
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Establishing the Flooding Limit (1g) 
9 
National Aeronautics and Space Administration 
www.nasa.gov 
Initial 1g Flooding Limit Data 
10 
National Aeronautics and Space Administration 
www.nasa.gov 
Flight Week 1, September 2011 
11 
• 40 parabolas per day 
 
• 12 Lunar, 3 Martian, 25 zero 
 
• 4 days totaling 160 parabolas 
 
 
National Aeronautics and Space Administration 
www.nasa.gov 
Data Analysis 
12 
National Aeronautics and Space Administration 
www.nasa.gov 
Lunar Results 
13 
National Aeronautics and Space Administration 
www.nasa.gov 
Conclusions 
• The observed RGE flooding limit falls between Faghri 
and Chung’s correlations providing boundaries for 
analysis. 
 
• Initial results show that correlation models may have 
discrepancies in the slope at lower temperatures as 
compared to the test data, both in 1g and reduced g. 
 
• Follow on work is continuing in 2012 to reduce data 
scatter and provide an improved correlation.  
 
 
 
14 


Observations of Thermosyphon Flooding in Reduced Gravity Environments

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