An extensive research and development program has been carried out to devise an improved method of removing waste heat of reaction from a developmental 2 kW hydrogen-oxygen fuel cell

Allan, K. N.

Bjorkman, H. K.

Elbert, T. E.

Hurley, J. R.

English

NASA Technical Reports Server

December 1968
	
Brief 68-10544 
NASA TECH BRIEF 
NASA Teèh Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Cooling of 2KW H 2-02 Fuel Cell 
An extensive research and development program 
has been carried out to devise an improved method of 
removing waste heat of reaction from a developmental 
2KW 1­1 2-02 fuel cell. The objectives of this effort 
were to eliminate an intermediate heat exchanger, in-
crease system reliability, improve thermal perform-
ance (to reduce radiator requirements and enable the 
fuel system to accept a greater range of coolant tem-
peratures), and to reduce system cost and weight. 
In one method which was developed, waste heat of 
reaction is removed from the fuel cell by conduction 
through the cell plates, via a suitable thermally con-
ductive electrical, insulator, to channeled cold plates. 
Coolant is passed through the'-Cold-plates on two 
sides of the cell stack, and heat is removed from the 
stack by conduction through the cell plate edges and 
the cold plates. The flow channels are of rectangular 
cross section to take advantage of the large heat 
transfer coefficients associated with high geometric 
aspect ratios. The cold plates are constructed of alumi-
num, and all welding is performed by the electron 
beam process. The insulating medium is a 0.007-inch-
thick layer of a silicone polymer loaded with mag-
nesium oxide to improve thermal conductivity. This 
insulation is a resilient material capable of compensat-
ing for small irregularities in the surface formed by the 
cell plate edges. Fuel cell temperature is controlled by 
varying the flow rate of the coolant through the cold 
plates. The basic design of the cooling system can be 
adapted to allow various now patterns and manifold-
ing arrangements without altering the fuel cell stack 
or other components. 
A water cavity, heat pipe cooling method, which 
was investigated, requires further development. This 
method would have potential application to all fuel 
cell systems using the static moisture removal method 
of collecting fuel cell product water. At a current den-
sity of 200 amperes per square foot, approximately 33
percent of fuel cell waste heat of reaction is removed 
as latent heat of vaporization at the water removal 
matrix and is rejected to the coolant at the water con-
denser. Water, supplied from the recovery subsystem 
at approximately 60 psi, is injected either into the oxy-
gen or hydrogen cavity; the water is then removed as 
vapor with the product water. Fuel cell temperature is 
controlled by the frequency, duration, and rate of 
water injection. Condensation of the vapor and col-
lection of the condensate are accomplished by a con-
denser using a water-glycol coolant loop and recovery 
subsystem of adequate capacity. 
Another method of cooling fuel cells, primarily 
under reduced gravity, has been in a conceptual stage 
of development. In this method, the coolant fluid 
would be supplied to the distribution manifold under a 
slight pressure and conveyed to the heat source by 
capillary wicks. The resultant vapor develops a pres-
sure head, which would be converted to a velocity 
head in the injector nozzle of an impulse pump. A 
pressure drop would thus appear at the vapor orifice. 
Condensate from the condenser would be carried into 
the vapor stream and accelerated in an accelerator 
barrel. The velocity head is partially converted to a 
pressure head, which is greater than the initial vapor 
pressure. This pressure rise, plus the pressure-gradient 
increase due to the capillary wicking, would force the 
liquid to flow into the fuel cell. Operation of the im-
pulse pump is similar to that of a steam-water injector 
used on a boiler. 
Note: 
Documentation is available from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Price $3.00 
Reference: B68-10544
(continued overleaf) 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19680000500 2020-03-12T06:30:15+00:00Z
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: J. R. Hurley, H. K. Bjorkman,

K. N. Allan, and T. E. Elbert

of Allis-Chalmers
under contract to

Marshall Space Flight Center

(M FS- l3737, 13740, & 13749)
. 
. 
Brief 68-10544	 -	 Category 01
	 -.


Cooling of 2 kW H subscript 2-O subscript 2 fuel cell

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