Burke, Kenneth A.

NASA Technical Reports Server

National Aeronautics and Space Administration 
www.nasa.gov 
2011 Fuel Cell Seminar and Exposition 
October 31st_ November Jrd 2011 
Walt Disney World Swan and Dolphin Resort, Orlando, FL 
Demonstration of Passive Fuel Cell Thermal 
Management Technology 
Kenneth A. Burke 
NASA Glenn Research Center 
Cleveland, Ohio 44135 
Ph. (216)-433-8308 
Kenneth.A.Burke@nasa.gov 
https://ntrs.nasa.gov/search.jsp?R=20150010195 2019-08-31T07:50:33+00:00Z
Demonstration of Passive Fuel Cell Thermal Management Technology 
The objective of the advanced thermal management work is to develop a 
passive means of fuel cell thermal management that can eliminate system 
components within the conventional pumped loop cooling systems used 
presently. This will reduce mass and improve reliability. 
Conventional 
Fuel Cell with 
Pumped Loop 
Thermal 
Management 
Fuel Cell with 
Passive Thermal 
Management 
National Aeronautics and Space Administration 
Fuel Cell 
Stack 
Fuel Cell 
Stack 
Sensors 
Heater 
Thermostat 
Valve 
Fuel Cell 
System Hx 
Fuel Cell 
System Hx 
2 
Demonstration of Passive Fuel Cell Thermal Management Technology 
The purpose of this. work was to: 
• Test two different control valve approaches to the control of the passive 
thermal management of fuel cell stacks. 
• Electronically controlled proportional valve to control the coolant 
flow through the heat exchanger which controlled the fuel cell 
temperature. 
• Thermostatic valve whose actuator opened and closed the valve 
through expansion and contraction in response to the temperature of the 
coolant flowing through the valve. 
• Demonstrate previously developed cooling plate technologies in operational 
fuel cell stacks. 
• Pyrolytic graphite cooling plate fuel cell stack 
• Titanium heat pipe cooling plate fuel cell stack 
National Aeronautics and Space Administration 3 
Demonstration of Passive Fuel Cell Thermal Management Technology 
Passive Thermal Management Control Valves 
When the valve is fully 
closed , a small bypass 
flow gets through 
The piston expands as it As the valve is pushed off 
gets warmer, pushing the the valve seat, greater 
valve off the valve seat amounts of flow go 
iii.liiii~;;,;,;_.-..::::...:___;_~~~-.J through the valve 
Electronically controlled Thermostatic valve 
proportional valve 
• The Electronically controlled proportional valve controls the coolant flow 
in response to a 0-5VDC contr~l signal. 
• The Thermostatic valve actuator opens or closes the valve in response to 
the temperature of the coolant flowing through the valve. 
National Aeronautics and Space Administration 4 
Demonstration of Passive Fuel Cell Thermal Management Technology 
Instrumented Cooling Plate 
• 9 TIC's on one side 
• Pad heater on other side 
Simulated Fuel Cell Stack 
Coolant In 
Interface Heat Exchanger 
• TIC's on inlet/outlet 
• Slots for 4 cooling plates 
• Anodized aluminum 
·Simulated Fuel Cell Stack 
• 4 Instrumented cooling 
plates 
During the testing Plates A&D (the outer-most plates) tended to run cooler than the inner plates (Plates B&C). 
National Aeronautics and Space Administration 5 
Demonstration of Passive Fuel Cell Thermal Management Technology 
7 
Passive Thermal Management Control Test Facilities 
Temperature Data 
The testing was done in 
a vacuum chamber to 
eliminate convective heat 
transfer that would have 
complicated the results 
Computer Workstation 
------------------~ D Heater Control 
Valve Control ~ 
I 
I L __ 
=I 1---------:- -------- -~~
I ; 
I 
I 
I 
I 
I 
I 
I 
I 
I 
- _____ .) 
I"'----" L. ............................. fOccc ~~ 
Power Supply 
Chiller 
Temperature Data 
Computer Workstation 
I"=~--=" L ........... ... ... ............... fOccc ~~ 
Power Supply 
Chiller 
The proportional valve is located outside the vacuum chamber 
because the valves were not compatible with vacuum conditions. The thermostatic valve is located inside the vacuum chamber 
immediately downstream of the interface HX to more quickly National Aeronautics and Space Administration 
respond to temperature changes. 
6 
Demonstration of Passive Fuel Cell Thermal Management Technology 
Passive Thermal Management Control Results - Proportional Valve 
85 85 --,-------- --------------, 
7.77 Watts/Plate Plate 8 
75 
29.9 Watts /Plate Plate 8 
75 ~--------~---~ 
65 (.) 65 
0 
(.) 55 
(J) 
::; 55 
0 .... 
(J) 45 ~ 
::J 
.... 
"' 35 ~ (J) 
a. 
E 25 ~ 
15 
- aooc "' Qj 45 
- ?ooc a. 
60°C E 
- ·5ooc ~ 35 
- 40°C 25 
- 30°C 
15 
- aooc 
- ?ooc 
60°C 
- 5ooc 
0 20 40 60 80 100 0 10 · 20 30 40 50 60 
Time, minutes Time, minutes 
The proportional valve is able to control the plate temperature (with some small offset from the setpoint) 
independent of the power level on Plate B. Plates A,C & D were nearly identical in performance. The 
oscillation about the control value gets greater at greater temperature. No fine tuning of the control loop 
was done to improve the results because the simulated fuel cell stack had an unrealistically low mass. 
An actual fuel cell stack would respond slower and be even easier to control. 
National Aeronautics and Space Administration 
70 
Demonstration of Passive Fuel Cell Thermal Management Technology 
Passive Thermal Management Control Results- Proportional Valve 
60 ~--------------------------------------------~ 35 
Cooling Plate B, 47°C Setpoint 
u 40 ~-----1~~~-----T~~--~~----.-----~----~ 
0 
Q)-
.... 
~ 30 +------1~--~-----+r-----~~----.-----~----~ 
Q) 
c. 
E 
~ 20 ~-----1~-1--------~~~-----.----~--------~ 
10 ~--~-1~-1--------~~~--------------------~ 
- Plate B Average Temperature 
- Plate Power 
30 
25 .! ca 
a.. 
U; 
20 = ca 
~ 
~· 
15 Q) ~ 
0 
a.. 
10 Q) ~ 
a.. 
5 
0 ~----~----~----~~~~----~--~----~-----+ 0 
0:00 0:30 1:00 1:30 2:00 2:30 3:00 3:30 4:00 
Time, hh:mm 
The proportional valve is able to control the plate temperature except when the plate power dropped drastically. 
Because the simulated fuel cell stack had such a low mass (compared to an actual stack) the temperature 
responded very quickly. Fine tuning the control loop could have improved this result, but was not done. 
National Aeronautics and Space Administration 8 
Demonstration of Passive Fuel Cell Ther~al Management Technology 
Passive Thermal Management Control Results- Proportional Valve 
90 ~------------------------------------------~ 35 
Cooling Plate B, 77°C Setpoint 
u 60 +-+----H~~r-----H-------~----~--~~--~ 
0 
~50 +;-----H---+r-----H-------~----~--~~--~ 
::::J 
..... 
~ 40 =l=f-- ---~-.............................. --H---=*====H== ~II=====ft======9 
C1) 
a. 
E 30 -Y+-----~--+--------+--+-----*---------11--- -------ff---- -----------1 {E. 
20 *---~~~-+--------+---1---~----~------------------1 
- Plate B Average Temperature 
- Plate Power 
30 
C1) 
..... 
25 ~ 
a.. 
...... (/') 
..... 
..... 
20 ~ 
..: 
C1) 
15 ~ 
0 
a.. 
C1) 
10 ~ 
a.. 
5 
0 0 
0:00 0:30 1:00 1:30 2:00 . 2:30 3:00 3:30 4:00 
Time, hh:mm 
These are similar to the previous 4 7°C results except the oscillations are slightly bigger in amplitude. 
National Aeronautics and Space Administration 9 
Demonstration of Passive Fuel Cell Thermal Management Technology 
Passive Thermal Management Control Results - Thermostatic Valve 
0 
0 
C1) 
.... 
100 
90 
~ 80 
.... 
Q) 
E" 10 
Q) 
1-
Q) 
'$ 
0:: 
60 
g, 50 
<( 
0 40 
30 
20 
10 
- Plate A Power 
- Plate B Power 
- Plate C Power 
- PlateD Power 
Plate A Avg Temp 
- Plate B Avg Temp 
- Plate C Avg· Temp 
- Plate D Avg Temp 
, 
v J 
r 
I 
0 
0:00 0:20 0:40 
Bypass Flow= 10 ml/min 
Avg. Plate Temp. ac --
- r 
!/ I 
f ~ J 
Plate Power, W/Piate -j I 
I L. 
I 
1:00 1:20 1:40 
Time, hh:mm 
100 
0 
- Plate A Power Bypass Flow = 10 ml/min 0 
a: 90 - Plate B Power 
E 
-
y 
Q) 
- Plate C Power 1- 80 ~ - Plate D Power 
_r s 
- Coolant Outlet Temp 0 70 
E ('CI - Coolant Flow Rate 
0 60 
0 
0 
.... 50 0 
Q) 
'$ 40 
0:: 
~ 30 ~ 
Plate Power. W/Piate Q) 
:1: 
0 20 ll.. 
Q) 
... ('CI 10 0:: 
0 
2:00 2:20 0:00 0:20 0:40 1:00 1:20 1:40 2:00 
Time, hh:mm 
2:20 
The Thermostatic Valve cannot control the plate temperature independent of the plate power., because the 
valve responds with greater coolant flow only after the coolant temperature has increased. 
National Aeronautics and Space Administration 
110 
90 
70 
50 
30 
10 
-10 
Q) 
s 
c § 
E 
<1)' 
'$ 
ll:: 
:1: 
0 
u: 
E 
('CI 
0 
0 
0 
10 
Demonstration of Passive Fuel Cell Thermal Management Technology · 
Passive Thermal Management Control Results - Thermostatic Valve 
70 ~--------------------------------------~ 45 300 
- Plate B Average Temperature 
Plate B Avg. Temp, oc - Coolant Outlet Temperature n 
Coolant Temp, °C 
' 40 60 +-------..---t-- ---- - Plate B Power \ j ~~ j\ 250 
...: 
4) 
Plate Power, W/Piate 
~ 
u 
0 35 
4) 
... 
::::l 
~ 30 
4) 
c. 
E 
~ 25 
... 
0 
4) 20 
16 
~ 
(\ \ V v Coolant Flow Rate, ml/min 
Plate Power, W/Piate \ 
' \ ... 
,~ 
.II 
~ 20 ~----~--~----~-----1~---.----~----~ ~ 15 
...: 
4) 1 "a.&... 
Ill. I.!Lu. 1 1 ,.., .. ll.. 
4) 
«; ~ 10 ~ 
,_ I"" .,-
~ 10 ~--~~~~-----r1-~----~----~------~ ll.. 4) 
~ 5 r "- ....,_r ' 
.,. 
.,.,., 
ll.. 
0 +---~----~--~--~~--~----~--~----~ 
0:00 0:30 1:00 1:30 2:00 2:30 3:00 3:30 4:00 
Time(h:mm) 
- Coolant Temperature 
- .....__ ....., 
- Plate Power 
- Coolant Flow Rate 
0 
0:00 0:30 1:00 1:30 2:00 2:30 3:00 3:30 4:00 
Time.h:mm 
The Thermostatic Valve results show that the coolant flow does not respond as quickly as the power level 
(or plate temperature). When the power level returns to a "baseline" value the plate temperature and 
coolant temperature likewise return to their "baseline" values. 
National Aeronautics and Space Administration 
c 
200 ·E 
::::. 
_§_ 
4) 
150 16 
0:: 
100 
50 
0 
:;:: 
0 
u: 
11 
Demonstration of Passive Fuel Cell Thermal Management Technology 
Passive Thermal Management Control Test Facilities 
+ 
Temperature Data 
r-------------------------------1 
1. 
1 Fuel Cell Power 
Fuel Cell 
Stack 
Chiller 
Computer Workstation 
D 
DODD 
Computer Controlled 
Electric Load 
The coolant from the chiller flows through the interface heat exchanger at a high rate to ensure that the 
interface heat exchanger is essentially iso-thermal. The temperature of this interface is controlled by the 
chiller temperature control. This approach was followed to experimentally remove the interface heat 
exchanger as a contributor to plate temperature differences, and therefore any plate temperature 
differences would be attributable only to cooling plate performance. 
National Aeronautics and Space Administration 12 
Demonstration of Passive Fuel Cell Thermal Management Technology 
Pyrolytic G.raphite Cooling Plate Fuel Cell Stack 
Cooling Plate 
Interface Plate 
(1) 
• 1 to 4 TIC's on each cell 
• Final fuel cell stack had 5 cells (not 6 as shown) 
• Each fuel cell had an active area of 75 cm2 
• Each cooling plate had a slip fit into the interface plate groove 
• Thermal grease filled the cooling plate/interface plate clearance 
National Aeronautics and Space Administration 
Cooling Plate 
Interface Plate (1) 
Interface Heat 
Exchanger (1) 
13 
Demonstration of Passive Fuel Cell Thermal Management Technology 
Pyrolytic Graphite Cooling Plate Fuel Cell Stack Results 
100 +---------------------~-----------+ 
u 
0 
e80 +------------------+--~-----------+ 
::J 
~ Avg Coolant Temperature 
Cl) 
a.6o +--r~~~~~~=-~~=-~====~~=* E 
~ 
0 40 !;~::======~~~~~======1---J 
... -
~ 20 +-=~------------------~------~--~ 
0 
a.. 
0 +-----~------~----~------~----~ 
10.0 
9.0 
8.0 
7.0 
6.0 
5.0 
4.0 
3.0 
2.0 
1.0 
0.0 
0.00 1.00 2.00 3.00 4.00 5.00 
Time, hr 
u 
0 
Cl)-
... 
::J 
-~ 
Cl) 
c. 
E 
~ 
Qi 
u 
c 
~ 
I 
X 
ro 
::?! 
80 
u 
0 
Cl)- 70 
... 
::J 
~ 60 
Cl) 
a. 
E 50 ~ 
0 40 
<( 
'E- 30 
Cl) 
... 
... 
::J 20 
u 
..:.:: 
~ 10 
-en 
0 
Average Cell #2 Temperature \ 
\ 
f 
/ Average Cell Voltage \ 
~ \. 
Stack Current \ 
\ 
I 
J 
0.00 1.00 2.00 3.00 
Time, hr 
4.00 
1.50 
1.40 
1.30 
- 1.20 
1.10 
/ 1.00 0.90 
0.80 
0.70 
" ~ 0.60 0.50 
5.00 
All the thermocouples are at essentially the same temperature throughout the test , therefore the plates are 
highly effective at distributing the heat within a cell and that the cooling plates are very consistent from one 
cell to the next. Besides moving heat out of the stack, the cooling plates are also very effective in moving 
heat into the stack (see beginning and end of test). · 
National Aeronautics and Space Administration 
u 
0 
> 
4i 
C) 
«$ 
-~ 
Qi 
u 
Cl) 
C) 
ro 
... 
Cl) 
~ 
14 
Demonstration of Passive Fuel Cell Thermal Management Techn.ology 
Titanium Heat Pipe Cooling Plate 
~62mm~ 
4 r-6.35mm I 6.35 mm,{33; m;4mm l 
.........__---r---r-- --1 I 
6.35 mm 
4 1 f 
62.2 mm 
I I 
I I 
--- 4 -----~------ 1 
I 
I 
I 
I 
I 
62.2 mm 1 
l 
Heat Pipe Plates 1 ,3, and 5 Heat Pipe Plates 2 and 4 
Each of the five heat pipe cooling plates was instrumented with thermocouples. The evaporator area of 
each heat pipe was approx. 45 cm2 which absorbed the heat from the active area of each fuel cell (which 
was 50 cm2 ). 
National Aeronautics and Space Administration ·15 
Demonstration of Passive Fuel Cell Thermal Management Technology 
Ti Heat Pipe Cooling Plate Fuel Cell Stack 
Cooling Plate 
Interface Plates (5) Heat Pipes (5) 
Interface Heat 
Exchanger 
National Aeronautics and Space Administration 
Cooling Plate 
Interface Plates (5) 
Coolant Ports (2) 
Exchanger 
16 
Demonstration of Passive Fuel Cell Thermal Management Technology 
Ti Heat Pipe Cooling Plate Fuel Cell Stack Results 
90 90 2.00 
Heat Pipe #1 Heat Pipe #1 
80 80 Heat Pipe #3 1.80 Heat Pipe #5 
u 70 70 
0 
1.60 ~ 60 60 ::I 
- u u ctl ... 0
p 50 1.40 ~ ~ 50 (1) 
E ... cU ::I ~ 40 ~ 40 C) 1.20 .s 
... (1) ~ 0 a. 
<{ 30 E 30 1.00 :; 
...: ~ 
~ 20 
... 20 
... 
0.80 ::I 
u 10 10 
Fuel Cell Current 
0 0 0.60 
-10 
-10 0.40 
0 100 200 300 400 500 0 100 200 300 400 500 
Time. minutes Time. minutes 
T he heat pipes were generally within a few degrees of each other except for heat pipes 1 & 5 which were 
the outer-most heat pipes (closest to the stack end plates). At the start of the test the heat pipes actually 
transferred heat from the coolant into the cell stack. Once the fuel cell current was increased to 20A the 
heat pipes got hotter than the coolant. At this point the heat pipes were transferring heat from the cell stack 
to the coolant. Further increases in the current required the coolant temperature to be lowered to maintain 
the stack at 80°C 
National Aeronautics and Space Administration 
u 
17 
Demonstration of Passive Fuel Cell Thermal Management Technology 
Ti Heat Pipe Cooling Plate Fuel Cell Stack Results 
90 80~---------------------------------. 
80 
70 
u 60 
0 
~ 50 
::I 
Heat Pipe #3 
Heat Pipe #5 
p 50+-~MW----------------------~~--~ 
elf 
.... 
::I 
-<V ~ 40+-~---------------------------~~~ 
.... .... 8. 40 Cl) 0. 
E 
Cl) 
1- 30 
E 30 ~r--------------------------------~ {!!. 
20 20+---------------------------------~ 
10 10+---------------------------------~ 
0 0+-----~----~----~----~------~~ 
0 100 200 300 400 500 0 100 . 200 300 400 500 
Time, minutes Time, minutes 
The temperatures on heat pipes #3 (the center-most heat pipe in the stack) and heat pipe #5 (one of the 
outer-most heat pipes) are shown above. The data shows that even though the plates differ by about 1 oac, 
the heat pipes themselves are nearly isothermal. 
National AeronautiGS and Space Administration 18 
Demonstration of Passive Fuel Cell Thermal Management Technology 
Conclusions 
The results demonstrate that passive thermal control of fuel cell stacks is feasible. 
It is controllable and provides the highly uniform thermal environment desired for 
fuel cell operation. This revolutionary thermal control approach reduces the 
components and parasitic power compared to the traditional pumped loop thermal 
control approach. 
• Coolant flow control using either the electronic proportional control valve or the 
thermostatic valve effectively controls the stack temperature . 
• The proportional valve controls the temperature independently of the fuel cell 
stack power, and maintains the stack temperature within a small control band. 
• The thermostatic valve is an extremely simple though less flexible approach. 
The power level and the operating temperature are not independent, but rise or fall 
together. Properly optimized for the fuel cell stack, it could provide an acceptable 
level of thermal control. 
· • The performance of both pyrolytic graphite and titanium heat pipe cooling plate 
technologies proved the feasibility of either style cooling plate. Both technologies 
can be adapted for integration in fuel cell stacks and both produce uniform thermal 
environments for fuel cell operation, both cell-to-cell and within any one cell. 
National Aeronautics and Space Administration 19 
.. . 
N~ ~· 
· .... 


Demonstration of Passive Fuel Cell Thermal Management Technology

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