Development of equipment for storage of liquid helium is discussed. Derivation of design curve and working equations for estimating effects of either perfect or imperfect heat transfer in storage device are described. Mathematical models of heat transfer conditions are provided

Dicarlo, J. A.

English

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el 
Liquid 
Nitrogen 
(77K) 
Liquid 
Helium 
(4K) 
High 
Vacuum 
June 1972	 B72-10286. 
NASA TECH BRIEF 
Lewis Research Center 
NASA Tech Briefs announce now 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. 
Design Curve for Liquid Helium Storage Vessels 
Figure 1. 
The problem: 
A major problem in the design of an efficient liquid 
helium storage vessel is the reduction of heat conduction 
along the stainless steel tubes which support the helium 
reservoir. A schematic of such a helium storage vessel is 
shown in Figure 1. This is usually solved by allowing the 
boil-off helium vapor to escape through the tubes so that 
a substantial portion of the conduction heat will be 
absorbed into the vapor and thereby prevented from 
reaching the liquid helium. Based on the assumption that 
maximum absorption can be achieved with baffles or 
other inserts, design curves have been computed for pre-
dicting that portion of the conduction heat which still 
reaches the liquid helium. However, there are frequent 
applications in which the interior of the support tubes 
cannot be obstructed by baffles or similar devices. In
10 
10 
E 
C., 
E 
Ui 
U-
102 
101
0.1	 1	 E	 10	 100 
Figure 2. 
these cases, finite tube lengths and vapor flows preclude 
the attainment of maximum or perfect heat transfer. 
Therefore, use of such curves for the determination of 
liquid helium hold-times becomes unwarranted. 
The solution: 
The single design curve shown in Figure 2 and its 
working equations have been derived for estimating the 
effects of either perfect or imperfect heat transfer in the 
tubes. The W0 (mW), is the conduction heat reaching a 
helium reservoir supported by n vapor-cooled stainless-
steel vent tubes each with cross sectional area A(cm2), 
length L(cm), and constant end-point temperatures of 
4 and 77 K. The We (mW) includes all helium reservoir 
heat inputs other than W0 . For perfect transfer, the para-
meter E0 1; for imperfect transfer, E 0
 <1. 
It can be estimated from: 
E0 L/( L + 2in)
(continued overleaf) 
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https://ntrs.nasa.gov/search.jsp?R=19720000285 2020-03-17T03:28:33+00:00Z
where th = 1.4 (W0
 + We)/n is the helium vapor flow 
(liquid cm 3 /hr) passing through each tube. In most im-
perfect transfer problems, E0 has a value between 0.1 
and 0.7. 
How it's done: 
Given any three of the four design parameters A, L, 
W0, We, the fourth can be easily determined by using the 
data in Figure 2 and its working equations. For instance, 
consider the design problem to determine the total boil-
off rate M (=nii) for a helium reservoir supported by 
two (n=2) unobstructed stainless tubes each with A = 0.4 
cm  and L = 20 cm. Because ?h is not known, an inter-
mediate value of E0 = 0.4 should be assumed. In the 
limiting situation where We = 0, one then directly uses 
the data in Figure 2 to determine E* = 0.4, W 0 24 mW, 
and M = 2m34 cm 3/hr. However, if radiation from 
liquid nitrogen radiation shield surfaces produces We = 
10 mW, determination of boil-off is not as immediate 
but requires a simple reiterative calculation. That is, one 
must first assume an initial value for W 0 (e.g, W0 = 
24 mW), compute the corresponding E* (0.57), use the 
design curve to calculate a new W0 ( 18 mW), replace 
this new W0 in the E* equation and recalculate, con-
tinuing this process until W0 converges to within the 
accuracy desired: W0 = 16 mW. Thus for We = 10 MW,
=36 cm3 /hr. This result in turn yields E0 = 0:36, a 
value consistent with the initial E0
 assumption. If perfect 
transfer (E0
 = 1) had been assumed, one would have 
obtained M=17 cm 3 /hr for We = 0 and M = 20 cm3/hr 
for We = 10 mW, or an error in the liquid helium hold-
time of approximately 100%. 
Notes: 
1. The following reference contains background informa-
tion on the technique described: Design Curve for 
Liquid Helium Cryostats with Vapor-Cooled Vent 
Tubes, J. A. DiCarlo, The Review of Scientific 
Instruments, Vol. 42, No. 2, pp. 262-264, February 
1971. 
2. No further documentation is available. Specific ques-
tions, however, may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B72-10286 
Patent status: 
No patent action is contemplated by NASA. 
Source: J. A. Di Carlo
Lewis Research Center

(LEW-1 1498)
. 
Category 02


Design curve for liquid helium storage vessels

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