Heat exchanger, using water as heat medium, converts liquid hydrogen to gaseous hydrogen at a very high rate. Possible applications include treatment of liquified natural gas in cities to bring the gas on-line quickly, conversion of liquid oxygen and liquid nitrogen for steel mills, and high volume inert purging

Bartlit, J. R.

Boyer, K.

Williamson, K. D.

English

NASA Technical Reports Server

October 1970
	 Brief 70-10591 
AEC-NASA Tech Briefs announce new technology derived from the research and development program of the U.S. AEC or 
from AE-NASA interagency efforts. They are issued to encourage commercial application. Tech Briefs are available on a 
subscription basis from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Requests for individual copies or questions relating to the Tech Brief program may be directed to the Technology Utilization 
Division, NASA, Code UT, Washington, D.C. 20546. 
The Water-Cryogen Heat Exchanger 
The problem: 
Development of the nuclear rocket has required the 
conversion of an enormous quantity of liquid hydro-
gen into gaseous hydrogen at a very high rate during 
test runs, using heat for the transformation. Typically, 
300,000 gallons of LH 2 had to be converted in one 
hour, which meant that in each second 8 gallons had 
to be raised from a temperature of —422°F to +50°F. 
This involved a total heat flux exceeding 77,000 Btu 
per second. No commercial vaporizers existed which 
approached this capacity. Even aircraft jet engines 
were inadequate at this demand rate, and were also 
undesirable because of cost and complexity. 
The solution: 
Design of the first known cryogenic heat exchanger 
in which water is used as the heating medium.
Ho it's done: 
The exchanger consists of 4 identical units, mani-
folded for parallel operation. Each unit is 80 feet long, 
and consists of concentric pipe which is looped into 
4 passes, providing a 320 foot run per pass. The outside 
pipe forms a water jacket, while the inside pipe, made 
of specially extruded aluminum, carries the hydrogen. 
The key to the system involves preheating 100,000 
gallons of water using a small propane burner, which 
brings the water to +200°F in one week. For the test 
run this reservoir is "dumped" into the heat exchanger 
at 748 lb/sec. Because of the exchanger manifolding 
and pipe size, the water pressure drop is under 5 lb; 
water temperature after converting the hydrogen is 
+80°F. In 4 years of usage the exchanger has been 
cycled several hundred times without a significant 
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Administration. Neither the United States Government nor any per-	 method, or process disclosed in this document may not infringe pri-
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problem. Contrary to expectation, no ice clog has ever 
occurred. After one 45-second water valve failure, 
ice had not even formed half-way across the water 
jacket cross section. 
Applications of this principle become increasingly 
attractive as the volume of liquid to be converted 
is increased, since commercial vaporizers are used 
for lesser amounts. Prototype analysis, supported by 
full-size construction and use, indicates that scaling 
presents few problems. One possible usage lies in the 
treatment of liquified natural gas in cities, so that 
gas can be brought on-line quickly during rush hours. 
Other uses could include LOX and LN 2 conversion for 
steel mills, high volume inert purging in many com-
mercial processes, and oceanographic installations.
Note: 
Inquiries concerning this innovation may be directed 
to:
Technology Utilization Officer 
-AEC-NASA Space Nuclear Propulsion Office 
U.S. Atomic Energy Commission 
Washington, D.C. 20545 
Reference: B70-10591 
Patent status: 
No patent action is contemplated by AEC or NASA.

Source: Keith Boyer, John R. Bartlit, and

Kenneth D. Williamson of

Los Alamos Scientific Laboratory

under contract to

Space Nuclear Propulsion Office

(NUC- 11029)
Ll 
S 
Brief 70-10591	 Category 03


The water-cryogen heat exchanger

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