A surface-tension liquid pumping system is provided by one or more arrays of converging solid monofilament fibers or metal wires (strands) spaced apart at an input end to gather liquid, and gathered close together at the opposite end where menisci forms between wetted strands to force liquid in the direction of convergence of the strands. The liquid pumping system is independent of gravity. It is illustrated as being used in a heat pump having a heating box to vaporize the liquid and a condensing chamber. Condensed liquid is returned by the pumping system to the heating box where it is again vaporized. A vapor tube carries the vapor to the condensing chamber. In that way, a closed system pumps heat from the heating box to the evaporating chamber and from there radiated to the atmosphere

Collins, Earl R., Jr.

English

NASA Technical Reports Server

United States Patent [191 
Collins, Jr. 
1111 Patent Number: 4,877,082 
[45] Date of Patent: Oct. 31, 1989 
[54] CONVERGENT STRAND ARRAY LIQUID 
[75] Inventor: Earl R. fillins, Jr., La Canada, Calif. 
E731 Assignee: United States of America as 
PUMPING SYSTEM 
represented by the Administrator, 
National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 337,767 
[22] Filed: Apr. 13,1989 
[51] Int. Cl.4 .............................................. F28D 15/02 
[52] U.S. CL ................................. 165/104.26; 165/41; 
122/366; 222/187; 239/145; 417/53; 417/572 
[58] Field of Search ............................. 165A04.26, 41; 
122/366; 222/187; 239/145; 417/53, 572 
1561 References Cited 
2,551,114 5/1951 Goddard . 
2,885,123 5/1959 Turpin ................................. 222/187 
3,174,688 3/1965 Chatten ................................. 239/20 
3,379,855 4/1968 Forrester et al. ................... 219/274 
3,428,222 2/1969 Wright . 
3,576,210 4/1971 Trent .............................. 165A04.26 
US. PATENT DOCUMENTS 
3,984,051 10/1976 Labbe et al. .......................... 239/44 
4,109,709 8/1978 Honda et al. ................... 16V104.26 
4,116,266 9/1978 Sawata et al. .................. 16W104.26 
Primary Examiner-Albert W. Davis, Jr. 
Attorney, Agent, or Firm-Thomas H. Jones; John R. 
Manning; Charles E. B. Glenn 
A surface-tension liquid pumping system is provided by 
one or more arrays of converging solid monofilament 
fibers or metal wires (strands) spaced apart at an input 
end to gather liquid, and gathered close together at the 
opposite end where menisci forms between wetted 
strands to force liquid in the direction of convergence 
of the strands. The liquid pumping system is indepen- 
dent of gravity. It is illustrated as being used in a heat 
pump having a heating box to vaporize liquid and a 
condensing chamber. Condensed liquid is returned by 
the pumping system to the heating box where it is again 
vaporized. A vapor tube carries the vapor to the con- 
densing chamber. In that way, a closed system pumps 
heat from the heating box to the evaporating chamber 
and from there radiated to the atmosphere. 
[57l ABSTR4CX 
6 Claims, 4 Drawing Sheets 
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U.S. Patent od. 31,1989 Sheet 1 of 4 4,877,082 
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U.S. Patent oct. 31,1989 Sheet 3 of 4 4,877,082 
U.S. Patent oct. 31,1989 Sheet 4 of 4 4,877,082 
* 4,877,082 1 
CONVERGENT STRAND ARRAY LIQUID 
PUMPING SYSTEM 
ORIGIN OF THE INVENTION 
The invention described herein was made in the per- 
'formance of work under a NASA contract, and is sub- 
ject to the provisions of Public Law 96-517 (35 USC 
202) in which the Contractor has elected not to retain 
title. 
TECHNICAL FIELD 
This invention relates to passive liquid feed systems 
that operate independently of gravity, and more partic- 
ularly to an array of convergent filaments in a surface 
tension, liquid pumping system. 
BACKGROUND ART 
Nonmechanical pumping of liquid is desirable and 
sometimes required for some applications where power 
for driving a pump is not available or is very precious, 
such as in a remote terrestrial location or a space labora- 
tory. The problem is most common in space because of 
the !ack of gravity that might otherwise be used in 
moving a liquid from one point to another, but the prob- 
lem can also occur in terrestrial applications at remote 
locations. 
An example of a terrestrial application is in connec- 
tion with transporting oil from the arctic through a 
pipeline laid over tundra. The oil is first heated in a 
storage tank and then pumped through an elevated 
pipeline. Because the ground is always frozen below the 
surface, the pipeline is not buried and is instead elevated 
to a height sufficient to allow animals to pass beneath it 
and insulated to minimize heat loss from the oil in order 
to maintain its lowered viscosity. Stanchions which 
support the pipeline will, however, conduct heat into 
the tundra sufficient to cause significant thawing around 
the tundra. During some period of the year, the thaw 
may extend from one stanchion to the next, thus creat- 
ing a continuous ribbon of thawed tundra that may 
deter animals from crossing. To prevent creation of this 
ribbon of thawed tundra, it is desirable to provide a heat 
pipe that conducts heat away from the base of each 
stanchion and into the air. 
A heat pump operating without any mechanical mo- 
tion of parts may consist of a heat exchange system in 
which liquid is evaporated in a space in thermal contact 
with the base of the stanchion. The vapor produced is 
then carried by a tube to a condensing space where heat 
is radiated into the atmosphere. Condensed liquid that 
accumulates in that condensing space must then be 
pumped back into the space in thermal contact with the 
base of the stanchion. The problem then is to pump the 
return liquid without the use of a mechanical pump and 
independently of gravity. 
Nonmechanical pumping of liquids has been achieved 
in the prior art by porous materials used in wicking 
systems, such as that disclosed in U.S. Pat. No. 
3,984,051 and by hollow capillary tubes, such as that 
using tapered capillary tubes disclosed in U.S. Pat. No. 
3,379,855. However, these known prior-art systems 
have limitations, so there is a need for nonmechanical 
pumping systems that do not rely upon internal absorp- 
tion or capillary tubes. 
L 
STATEMENT OF THE INVENTION 
In accordance with the present invention, a surface- 
tension liquid pumping system is comprised of an array 
5 of converging solid monofilament fibers or metal wires 
(hereinafter referred to as strands) spaced apart at an 
input end and gathered close together at the opposite 
end where a meniscus is formed between the converg- 
ing strands. Surface tension will force liquid from the 
10 input end to the opposite end without any mechanical 
pumping elements. Support elements of suitable geo- 
metric shape (linear, rectangular, elliptical, circular, or 
the like) are provided to space the strands at the input 
end and to gather them at the output end. A housing 
15 encloses the array of strands and secures the spacing 
and gathering support elements. Alternatively, the sup- 
port elements may be made as an integral unitary part of 
the housing. . 
The novel features that are considered characteristic 
20 of this invention are set forth with particularity in the 
appended claims. The invention will best be understood 
from the following description when read in connection 
with the accompanying drawings. 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 illustrates a surface-tension liquid pumping 
system, which operates without the use of moving parts 
and independently of gravity, in accordance with the 
present invention used in a heat pump shown in an 
FIG. la illustrates a plan view of a spacing element at 
the liquid input end of strands as seen from the left in 
FIG. 1. 
FIG. l b  illustrates a plan view of a gathering element 
35 at the liquid output end of strands as seen from the left 
FIG. IC illustrates sections of two converging strands 
FIG. 2u illustrates schematically a cross section of the 
40 heat pump in FIG. 1 for comparison with a prior-art 
heat pump shown in FIG. 26 which has no moving parts 
but relies upon gravity. 
FIG. 3 illustrates schematically a plan view of a sec- 
ond embodiment of a heat pump utilizing two surface- 
45 tension liquid pumping systems and one vapor tube 
arranged between a heating box and a condensing 
chamber. 
FIG. 4 illustrates schematically a cross section taken 
on line 4-4 in FIG. 3 to show an elliptical shape of the 
50 array geometry at the input end and an annular shape of 
the array geometry at the output end of the surface-ten- 
sion pumping apparatus, and the shape of the vapor tube 
between a heating box and a condensing chamber. 
FIG. 5 illustrates a plurality of rectangular arrays of 
55 strands for use in a surface-tension liquid pumping sys- 
tem with a rectangular vapor tube between a heating 
box and a condensing chamber. 
DETAILED DESCRIPTION OF THE 
INVENTION 
Referring to FIG. 1, a conical array 10 of strands 11 
made of monofilament fibers (such as polymeric mono- 
filament material commercially available for use as fish- 
ing line) or of small gauge metal wire (such as copper 
65 wire commercially available for use in small transform- 
ers) is supported between annular elements 12 and 13 of 
different diameters. A plan view of the spacing element 
12 (shown in FIG. la as seen from the left in FIG. 1) is 
25 
30 isometric view partially broken away. 
in FIG. 1. 
wetted by liquid. 
60 
4,877,082 
3 4 
of a diameter sufficiently large to space apart the strands thus the force which drives the liquid from the condens- 
at the input end where liquid accumulates in a condens- ing chamber into the heating box 17, while a vapor tube 
ing chamber 14. That annular spacing element is affimed 20 provides for flow of liquid vapor from the heating 
to the inside face of a condensing plate 15 of the cham- box 17 to the condensing chamber 14. 
ber 14. A plan view of the annular gathering element 13 5 Referring now to FIG. 26, a prior-art heat pump 21 is 
is shown to a larger scale in FIG. 16 as seen from the illustrated for comparison with the heat pump of FIG. 
left. 1, shown schematically in FIG. 2u. For convenience, 
A knot is tied in each strand before it is placed in a elements of the pumping apparatus shown in FIG. 1 and 
groove across the face and side of the spacing element illustrated schematically in FIG. 20 are identified by the 
12, and before the spacing element 12 is affmed flat 10 same reference numerals, namely a conical array 10 of 
against the condensing plate 15, such as by epoxy or strands, a heating box 17, a condensing chamber 14, a 
small screws. Once the annular element l2 is affixed flat condensing plate 15, a housing 18, and a vapor tube 16. 
against the inside face of the condensing plate 15, each In the prior-art heat pump 21, a closed hollow cylinder 
strand is secure in its slot due to the knot tied in its end. 22 has a flat base plate 23 at the bottom end which is 
This firmly secures on end of each strand in a radial slot 15 buried in the tundra or is otherwise placed in thermal 
cut in the element 12. The free ends of the strands are contact with something out of which heat is to be 
then drawn taut through the opening of the annular pumped. Liquid in the chamber is then vaporized in the 
gathering element 13 and secured to posts 13u by a half cylinder 22, and the vapor rises. At the top of the cylin- 
hitch or other suitable knot with three strands per post. der, the vapor condenses and a dome 24 accumulates 
To assure that the knot remains secure, epoxy may be 20 liquid. The liquid formed on the dome runs to the wall 
applied to the strands on the posts. This gathers the of the cylinder, and from there down to the base plate 
strands so that, in passing through the opening of the 23, all under the force of gravity. Returned liquid is 
annular element 13, each strand comes in contact with heated at the base plate and vapor rises in the cylinder 
adjacent strands. to complete one cycle. Fins 25 at the top of the cylinder 
The gathering element 13 is affued to a wall 16 of a 25 enhance the radiation of heat for the condensation of 
heating box 17. Alternatively, the gathering element 13 the vapor. 
may be simply an opening in the wall 16 with posts The heat pump of FIG. 20 is also a closed cycle sys- 
spaced around the opening. A housing 18 protects the tem, and to enhance the radiation of heat from the con- 
strands 10 and spaces the condensing chamber 14 away densing chamber 14, its end plate 15 may be provided 
from the heating box 17. 30 with fins 1Sa. Liquid that accumulates in the heating 
Once the strands 11 have been wetted from the input box 17 is dispersed by the porous material 19 so that it 
end to the output end, surface tension of the liquid in a may be more readily vaporized. The vapor flows 
meniscus between two adjacent strands near the output through the tube 16 into the condensing chamber 14. 
end will force liquid toward the output end (from right Condensed vapor on the plate 15 gathers on strands at 
to left) in FIG. 1, as shown in FIG. IC by arrows indi- 35 the input end of the conical array 10. The return flow of 
cating the direction of flow. As surface tension forces liquid, driven by surface tension in the conical array 10, 
liquid to the left, it draws liquid from the strands passing continually replenishes liquid that is vaporized, while 
through slots on the side of the spacing element l2 on the tube 16 continually replenishes vapor in the con- 
the right. As liquid is drawn out of the accumulation densing chamber. As the vapor condenses in the cham- 
area in the annular support element 13 for evaporation, 40 ber 14, the vapor pressure drops below that of the vapor 
surface tension forces liquid to replace the liquid drawn coming out of the heating box. This pressure differential 
out. keeps vapor moving into the condensing chamber. The 
It should be noted that in passing through the gather- closed cycle thus functions to pump heat from the heat- 
ing element 13, the adjacent strands are all parallel. In ing box 17 to the condensing chamber 14. From there 
the short parallel section of the strands, the liquid is no 45 heat radiates into the atmosphere. 
longer driven by surface tension. It is instead driven by Because of this horizontal flow of liquid and vapor, 
more liquid behind it that is forced into that parallel all without reliance on gravity, the heating box 13 of the 
section by surface tension between converging strands. heat pump shown in FIG. 2u can be thermally con- 
Thus, the liquid will tend to be moved away from the nected directly to the base of a stanchion (not shown) 
converghg strands and into the heating box 17. This 50 that supports an oil pipeline above arctic tundra. The 
parallel section may be made longer to provide a larger heat pump will draw heat directly out of the base of the 
place for liquid to accumulate, but in a heat pump ab- stanchion and radiate it into the atmosphere before it 
sorbing material 19 (such as cotton) is provided in the reaches the tundra so that the tundra that supports the 
heating box to immediately distribute accumulated liq- stanchion will not thaw. Thus, the heat pump of FIG. 
uid in the heating box for vaporization. 55 2u has the advantage that the heating box may be ther- 
As just noted above, for use in a heat pump as illus- mally connected directly to the stanchion because it is 
trated in FIG. 1, the spacing support element l2 is horizontally oriented. A further advantage is that the 
spaced away from the gathering element 13 by the cy- closed cycle will operate more efficiently with a greater 
lindrical housing 18 which protects the array 10 of volume of recirculated liquid by the surface tension of 
strands. Thus, at the input end, the element 12 spaces 60 the strands because the number of strands may be 
the strands apart in the condensing chamber 14 over a readily increased, as will now be described. 
distance sufficient to allow condensing vapor to gather FIG. 3 illustrates schematically two arrays 31 and 32 
on the plate 15, the spacing element 12 affmed to the of strands between a heating box 33 and a condensing 
plate 15, and the strands to keep the strands wetted. chamber 34 and a large vapor tube 35. FIG. 4 illustrates 
Surface tension of liquid in a meniscus between adjacent 65 schematically a cross section taken on line 4-4 of FIG. 
strands at the exit end (as shown in FIG. IC) contiually 3. FIG. 5 illustrates schematically in a perspective view 
forces the liquid wetting the strands to move in the partially broken away two arrays 41 and 42 of strands 
direction of the gathering element 13. Surface tension is between a heating box 43 and a condensing chamber 44 
4,877,082 
5 6 
and a large vapor tube 45 formed by adjacent side walls strands with each strand converging with adjacent 
46 and 47 which, together with an overall housing not strands, and a housing surrounding said array of strands 
only defines the heating box 43 and the vapor tube 45 supporting said spacing element spaced apart from said 
but also the condensing chamber 44. Note that the gath- gathering element to protect said array of strands and 
ering elements for the arrays 41 and 42 are here formed 5 maintain said strands taut. 
by OP-gS of Plates 48 and 4% Posts are Provided to 3. A passing liquid pumping system as defined in 
%Cure the ends of the Strands to those Plates. spacing claim 2 wherein said spacing element spaces said strands 
element 50 and 51 affixed to a condensing plate 52 are in a closed geometric pattern, and said gathering ele- 
rectan@ar and may each be provided with a grid Of ments gathers said strands in a closed geometric pattern. 
horizontal and vertical slots on the back side. The 10 4. A passive liquid pumping system as defined in 
gathering element in the plates 48 and 49 across the at said spacing 
back to the gathering elements. 
have been described and illustrated herein, it is recog- 
nized that modifications and variations may readily 
occur to those skilled in the art. Other applications of 
the heat pump, and indeed of the surface-tension pump- 
S k U l d S  in these back-side Slots are COntinUOUS from the 3 &d housing includes a chamber for 
receiving liquid 
gathering element. 
5. A passive liquid pumping system as defined in 
claim wherein said utilizing is a heating box for 
vaporizing said liquid and said chamber is a condensing 
chamber, and a tube for guiding vapor flow 
wets said 
Of the 50 and 51 and from there element, and means for utilizing liquid gathered at said 
Although particular embodiments of the invention 15 
ing appwam itself, will occur to those s u e d  in the m9 20 from said heating box to said 
p d c d u l y  applications aboard ip spacecraft. Come- 
quently, it is intended that the be interpreted to 
chamber, 
thereby to provide a system for Pumping heat from said 
box t0 Said chamber from which heat iS radiated Out to 
cover such modifications and variations. the atmosphere. 
I claim: 
1. A sdace-tension liquid pumping system 
6. A passive liquid pumping system for forcing liquid 
25 from one place to another independent of gravity com- 
prised of at least one array of taut converging strands prised of an array of converging strands held taut be- 
spaced apart at one end adapted to receive liquid and t ~ e e n  a Spacing element at one end of said strands and 
gathered close together at the opposite ends of the a gathering element at the opposite end of said strands, 
strands to allow fiq& wetting the strands to form me- where said spacing element is positioned at said one 
nisci between adjacent strands where they approach 30 place and said gathering element is positioned at said 
convergence thereby to cause surface tension to force other place, thereby to cause liquid wetting said strands 
liquid wetting the strands to flow toward the converg- to form menisci between adjacent strands where they 
ing ends of the strands. approach convergence, and thus cause surface tension 
2. A passive liquid pumping system as defined in to force liquid wetting the strands to flow toward the 
claim 1 wherein said spacing element spaces said strands 35 converging ends of said strands independent of gravity 
uniformly with each strand spaced equally from adja- and without any moving parts. 
cent strands, and said gathering element holds said * * * * *  
40 
45 
50 
55 
60 
65 


Convergent strand array liquid pumping system

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