System for transferring cryogenic liquids to a dewar prevents boiloff of residual liquid by venting the boiloff to the atmosphere during the transfer tube cooling period. The system is most useful with liquids having very small heat of vaporization

Hegland, D. E.

English

NASA Technical Reports Server

April 1966	 Brief 66-10157 
NASA TECH BRIEF	
I All 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Cryogenic Liquid Transfer System Reduces Residual Boiloff 
Vent Disk 
Hole 
The problem: 
In filling a partially empty dewar with a cryogenic 
liquid, the warm transfer tube causes the first entering 
liquid to boil off as gas and this brings about boiloff 
and raises the temperature of the residual liquid in the 
dewar. Several liters of fluid can be lost from a rela-
tively small dewar while the transfer tube is cooling. 
Temperature excursions of up to 40°K may occur in 
some instances.
The solution: 
A system that vents the boiloff to the atmosphere 
during the transfer tube cooling period, thus prevent-
ing boiloff of the residual liquid. 
How it's done: 
The system incorporates a large-diameter closed 
bottom tube, extending into the dewar, that permits 
boiloff of the transferred liquid during the cooling 
period. The transfer tube terminates near the bottom 
(continued overleaf) 
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Aeronautics and Space Administration. Neither the United States 
"	 Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
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of the large tube, adjacent to a final transfer tube ex-
tending through the bottom. The top of the large 
tube is vented to the atmosphere. The entire assembly 
is installed in the dewar opening by means of an 
0-ring sealing device. 
When cryogenic liquid drops below a hole in the 
wall of the lower extension of the final transfer tube, 
transfer is started from the supply source. A vent disk 
is removed from the large tube and boiloff gas gener-
ated by cooling of the transfer tube is vented to the 
atmosphere. The hole in the lower extension of the 
final transfer tube prevents the residual liquid from 
being siphoned into the large tube. When the transfer 
tube has cooled, liquid collects on the bottom of the 
large tube and overflows the standpipe portion of the 
final transfer tube to refill the dewar.
Notes: 
I. Using this system, less than one third of the resid-
ual liquid was lost in refilling a 3-liter de war. The 
temperature change in the residual liquid was 
0.02'K at worst and not observable at best through 
a series of tests. 
2. This system is most useful with liquids having very 
small heat of vaporization such as helium. It is not 
as useful with liquids with higher latent heat, such 
as N2. 
3. Inquiries concerning this innovation may be di-
rected to:
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio, 44135 
Reference: B66-10157 
Patent status: 
No patent action is contemplated by NASA. 
Source: D. E. Hegland 
(Lewis-274) 
Brief 66-10157	 Category 02


Cryogenic liquid transfer system reduces residual boiloff

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