Plate, serving as heat pipe, can be built into cell to control temperature and water inventory. Plate consists of matrix, filled with liquid water, and a space, filled with water vapor. Both matrix and space extend beyond fuel-cell stack so heat and water may be removed as necessary

Asher, W. J.

English

NASA Technical Reports Server

April 1974	 1	 B73-10489 
NASA TECH BRIEF	
c Marshall Space Flight Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Fuel-Cell Heat and Mass Plate 
..
A fuel-cell system requires that the temperature and 
the amount of water in the system be controlled. 
Rather than regulate these by external systems, it is 
preferable to save weight and reduce complexity by 
making the system self-controlled. 
A heat and mass plate that serves as a heat pipe can 
be built into the cell to control the temperature and the 
water inventory. The plate consists of a matrix, filled 
with liquid water, and a space, filled with water vapor. 
Both the matrix and the space extend beyond the fuel-
cell stack, so that heat and water may be removed as 
necessary. 
The side of the matrix opposite the space faces the 
reaction chamber, where water is produced electro-
chemically. Heat is removed as the heat of vaporization 
of water. Water evaporates from the matrix on the side 
of the space where the partial pressure is less than on the 
reactant side. The water vapor moves through the vapor 
space to outside the cell stack, where it condenses on the 
matrix to release the heat of vaporization. Water 
condensed on the matrix is then drawn back into the 
cell by capillary action. 
The vapor space is kept at a controlled pressure by 
venting it to the atmosphere. This pressure determines 
the boiling point of the water and, thus, the temperature 
of the matrix surface. The temperature of the electrodes 
likewise is controlled, because they are close to the 
matrix. 
The performance of the heat and mass plate may be 
enhanced by keeping the liquid/water-vapor interface 
exactly in the plane where the matrix meets the water-
vapor space. This can be done by adjusting the boiling 
point in the matrix or by controlling the venting, in one 
of the following ways: 
a. A matrix with an ion-exchange capacity may be used. 
The concentration of ions in the water, in the matrix, 
will elevate its boiling point.
b. Ions (e.g., K+ or OH) can be included in the matrix 
solution, thus raising the boiling point of the water 
there. 
c. The vapor space can be kept at a higher pressure 
than the liquid in the matrix. With a small-pore 
matrix, the local radius of curvature of the interface 
will increase the temperature required to evaporate 
water from the matrix. 
d. Two discontinuous metal strips can be deposited on 
the vapor side of the matrix, and the conductivity 
between them can be measured. The vent valve then 
would be opened only when the conductivity is above 
a specified value: 
Notes: 
1. The development of a fuel-cell system is further 
described in the following NASA Tech Briefs: 
B73-10475, Vapor-Deposited Platinum as a 
Fuel-Cell Catalyst 
B73-10472, A Methanol/Air Fuel-Cell System 
B73-10473, An Electrochemical Engine 
2. Requests for further information may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A&PS-TU 
Marshall Space Flight Center, Alabama 35812 
Reference: B73-10489 
Patent status: 
NASA has decided not to apply for a patent. 
Source: W. J. Asher of
Exxon Corp.
under contract to
Marshall Space Flight Center
(MFS-21318, 21319) 
Category 07,06 
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.
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Fuel-cell heat and mass plate

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