A heat transfer device is characterized by an hermetically sealed tubular housing including a tubular shell terminating in spaced end plates, and a tubular mesh wick concentrically arranged and operatively supported within said housing. The invention provides an improved wicking restraint formed as an elongated and radially expanded tubular helix concentrically related to the wick and adapted to be axially foreshortened and radially expanded into engagement with the wick in response to an axially applied compressive load. The wick is continuously supported in a contiguous relationship with the internal surfaces of the shell

Kalkbrenner, R. W.

English

NASA Technical Reports Server

>NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
Y. D.C. 20546
^
«74-18552
. CSCI 20H
Uncla
TO:
FROM:
_^
KSI/Scientific & Technical Information DivYsion
Attn: Miss Winnie M. Morgan
GP/Office of Assistant General
Counsel for Patent Matters
SUBJECT: Announcement of NASA-Owned U.S. Patents in STAR
In accordance with the procedures agreed upon by Code GP
and Code KSI, the attached NASA-owned U.S. Patent is being
forwarded for abstracting and announcement in NASA STAR.
The following information is provided:
U.S. Patent No. ; .J . * " / / / ^
Government or
Corporate Employee
Supplementary Corporate
Source (if applicable)
NASA Patent case No. AJ P 0 - U ( *o - (
NOTE - If this patent covers an invention made by a corporate
employee of a NASA Contractor, the following is applicable:
YES NO / /
Pursuant to Section 305 (a) of the National Aeronautics and
Space Act, the name of the Administrator of NASA appears on
the first page .of— the_pa-ten-t-;— however , the name of the actua.l_
inventor (author) appears at the heading of column No. 1 of
the Specification, following the words "...with respect to
an invention of ..."
Bonnie L. Woerner
Enclosure
https://ntrs.nasa.gov/search.jsp?R=19740010439 2020-03-17T14:27:08+00:00Z
United States Patent
Low et al.
[in 3,789,920
[45] Feb. 5, 1974
[ 54] HEAT TRANSFER DEVICE
[76] Inventors: George M. Low, Deputy
Administrator of the National
Aeronautics and Space
Administration in respect to an
invention of; Ralph W.
Kalkbrenner, P.O. Box 10864,
Pittsburgh, Pa. 15236
[22] Filed: May 21, 1970
[21] Appl. No.: 39,343
[52] U.S. Cl 165/105, 29/157.3 R, 267/166
[51 ] Int. Cl F28d 15/00
[58] Field of Search 165/105; 29/157.3; 267/166
[56] References Cited
UNITED STATES PATENTS
Grover et al 165/105 X
Levedahl 165/105
Levedahl 165/105
OTHER PUBLICATIONS
Deverall; J. E. et al., High Thermal Conductance De-
3,554,183
3,498,369
3,528,494
1/1971
3/1970
9/1970
vices, Los Alamos Scien. Lab., Calif., (4/1965),
(LA3211-ReportNo.).
Primary Examiner—Albert W. Davis, Jr.
Attorney, Agent, or Firm—John R. Manning; J. H.
Warden; Monte F. Mott
[57] ABSTRACT
A heat transfer device characterized by an hermeti-
cally sealed tubular housing including a tubular shell
terminating in spaced end plates, and a tubular mesh
wick concentrically arranged and operatively sup-
ported within said housing. A feature of the invention
resides in the provision of an improved wicking re-
straint formed as an elongated and radially expanded
tubular helix concentrically related to the wick and
adapted to be axially foreshortened and radially ex-
panded into engagement with the wick in response to
an axially applied compressive load, whereby the wick
continuously is supported in a contiguous relationship
with the internal surfaces of the shell.
1 Claim, 3 Drawing Figures
/P5-
/?3
PATENTED"* 51974 3,789,920
RALPH W. KALKBRENNER
INVENTOR
ATTORNEYS
- . - 3,789,920
1 2
HEAT TRANSFER DEVICE These and other objects and advantages are achieved
through a simplified heat transfer device having pro-
/-»ni<"ixi r\r? IXT\/CXTTH-.XI vided therein a retainer comprising an elongated helixORIGIN OF INVENTION . , , . „ , , * , .• „
adapted to be axially foreshortened and radially ex-
The invention described herein was made in the per- 5 panded in the presence of axially applied compressive
formance of work under a NASA contract and is sub- loads and employed for supporting a tubular mesh wick
ject to the provisions of Section 305 of the National in an operative disposition relative to the inner surface
Aeronautics and Space Act of 1958, Public Law of a tubular shell.
85-568 (72 Stat. 435; 42 U.S.C. 2457).
,0 BRIEF DESCRIPTION OF THE DRAWING
BACKGROUND OF THE INVENTION _, _ , . , . , . „ . . ,FIG. 1 is an exploded, partially sectioned elevation of
1 . Field of the Invention a heat transfer device embodying the principles of the
The invention relates to heat transfer devices of the present invention.
type generally disclosed in U.S. Pat. No. 3,229,759,
 FiG. 2 is a partially sectioned perspective view illus-
and more particularly to an improved heat transfer de- 15
 trating the heat transfer device of FIG. 1 in an assem-
vice having a tubular wick concentrically arranged jj|e(j configuration
within a tubular shell and an expanded helix function-
 FIG 3 is a crOss-sectional end view of the heat trans-
ing as a wicking restraint for continuously supporting fer device
the wick in an operative disposition relative to the in-
ternal surfaces of the shell. 20 DESCRIPTION OF THE PREFERRED
2. Description of the Prior Art • EMBODIMENT
The prior art is replete with heat transfer devices Referring now to the drawing wherein like reference
which employ a wick of the type commonly employed
 characters designate like or corresponding parts
in the so-called heat pipe. In such devices, the wick is
 throughout the several views, there is shown in FIG. 1,
supported in a seated disposition, relative to an adja- 25
 in an exploded> perspective view> a heat transfer device
cent circumscribing wall of a shell which defines a
 10 which embodies the principles of the instant inven-
sealed chamber. One technique heretofore employed
 t-
in supporting such a wick requires that a srping-loaded
 The heat transfef devie ,0 Js ided wjth an don.
retainer be utilized for urging the wick into engagement
 d housi includi a tubular shel, , , and a ir of
with the adjacent wall of the shell. However, due to the 30
fact that working fluids frequently require operative ^
 wofk. chamber ^ m^n t|w chamber .
temperatures of magnitudes which tend to have delete- . . ... .. ... ., . „ ,, .. . j.
. „ . , , . . . concentric relationship with the shell 11, there is dis-
rious effects on springs, the spring-loaded retainers . . . . . . ,,,
 f . ,. . . .
. . .
 r. , -i j I j ^ posed a tubular wick 14 of any suitable design. As athus employed often fail under prolonged use. Conse- f ... „
 t. . , .. , ,, • f Jr
, , „ f~ . t r, , . . , , -is practical matter, the wick 14 preferably is formed fromquently, the overall efficiency of the device is reduced. -0 . ,, - , . . , . • .
Another technique often employed in mounting a sultal>le Stamless ^1 mesh stock havmg a predeter-
wick within a shell of a heat transfer device requires rn'ned res.liency wh.ch accommodates a radial expan-
that a tubular shell be integrated with a tubular wick sl°n ot th^ W1C|CJ , . . . , , _, . , .
through a swaging process. However, mutual with- . U ls to be understood that the w.ck 14 is employed
drawal or "springback" of the thus integrated wick and 40 ln conveying , quid working fluids, not shown from a
shell tends to affect the interface established between 'c°o1 re8lon to a 'hot reelon- alon8 a cyllndncal
the wick and the adjacent surface of the wall of the Path- whereupon the working fluid is vaporized and
shell. Since it is desirable to accurately control pres- subsequently returned along a concentric axial path to
sures established at the interface between a wick and the "co°l region," whereupon condensation is
its associated shell, this technique frequently fails to 45 achieved. The particular fluid employed varies in ac-
satisfy existing needs cordance with the uses and temperatures operatively
encountered. Since the use of such fluids is well known,
OBJECTS AND SUMMARY OF THE INVENTION
 a detailed description is omitted.
It therefore is an object of the instant invention to An elongated wick retainer 16 is arranged in a con-
provide an improved heat transfer device adapted to be 50 centric relationship with the wick 14 and serves to sup-
employed over extended periods of use. Port the wick m an operative disposition relative to the
It is another object to provide a heat transfer device adjacent wall of the shell 11. In practice, the retainer
having a wick maintained in an operative disposition 16 '» of a configuration conforming to a tubular helix,
through an application of a constantly applied pressure. which, when axially compressed, is foreshortened and
It is another object to provide an improved heat radially expanded. The helix is so configured that a ra-
transfer device having a retainer adapted operatively to dially directed, predetermined pressure is developed
be seated within a tubular mesh wick and apply a radi- and applied along the internal surfaces of the tubular
ally directed, uniform pressure to the internal surfaces wick 14 as the helix axially is compressed. Pressure
of the wick as it is subjected to an axially applied, com- thus developed is employed in urging the wick into a
pressive force. seated relationship with the internal surface of the shell
It is another object of the instant invention to provide 12. The helix which serves as the retainer 16 is fabri-
an improved, readily fabricated heat transfer device cated in any suitable manner from a tubular metal
which may be employed over prolonged periods at ele- stock of a material such as a high grade of stainless
vated temperatures.
 65 steel. Where preferred, a stainless steel tube of a suit-
It is another object to provide a novel wick retainer able diameter and wall thickness is machined or milled
for a heat transfer device of the type commonly called to include a helical kerf 18 extending throughout the
a heat pipe. length of the tube, whereby the helix is formed.
3,789,920
The width of the thus formed kerf 18, as well as its
spiral lead, is employed in determining the radial ex-
pansion of the retainer 16 as it is foreshortened through
an axially applied compressive force. It should readily
be apparent that the material from which the retainer 5
is fabricated and the width of the helical kerf 18, as well
as the lead thereof, and the thickness of the wall of the
tube serve to dictate the limits of radial expansion
which are experienced as the retainer is foreshortened
under forces of compression. Therefore, in practice, 10
the width and lead of the kerf 18 are compatible with
the stock material employed in fabricating the retainer
16. As a practical matter, the wall of the retainer 16 is
provided with suitable perforations 19 which accom-
modate a passage of fluid therethrough in order to en- 15
hance the flow of the working fluid. Hence, the
strength and resiliency of the retainer are affected by
the size and number of such openings.
The end plates 12 are fabricated from a suitable ma-
terial compatible with the high grade stainless steel of 20
the shell 11 and the retainer 16. As best illustrated in
FIG. 2, each of the plates includes a circumscribing
skirt 23 which is inserted into an end of the shell 12 in
a manner such that the plates are arranged in a coaxial
relationship with the retainer 16. Preferably, the skirts 25
23 abut the ends of the wick 14 and circumscribe the
ends of the retainer as they are inserted into the ends
of the shell 11. The plates are then welded at beads 24,
or otherwise are secured to the shell 11 in order to es-
tablish the working chamber 13. 30
It is important to note that during the assembly of the
heat transfer device 10, the wick 14 is inserted into the
outer shell 11, and then the retainer 16, in its relaxed
state, is inserted through the wick 14 in a manner such
that its opposite ends extend a distance X, FIG. 1, from 35
the opposite ends of the shell 11. The end plates 12
now are positioned in a coaxial relationship with the re-
tainer 16 and compressively are displaced towards each
other so that the ends of the retainer 16 engage the end
plates 12 and become seated within the skirt 23. Con- 40
tinued mutual displacement of the end plates serves to
impose an axial loading on the retainer 16 for causing
the retainer to become foreshortened, through the dis-
tances X. As the retainer is foreshortened, it becomes
radially expanded and applies a radially directed pres- 45
sure to the adjacent surface of the wick 14. Once the
plates are fully seated within the opposite ends of the
shell 11, they are welded in place at weld beads 24,
formed in any suitable manner compatible with con-
ventional stainless steel welding techniques. The wick 50
14 of the device 10 thus assembled is supported with a
determinable pressure being applied by the retainer 16
maintained in its radially expanded state by the end
plates 12.
As a matter of convenience, it is preferred that one
of the end plates 12 be provided with a vent 25 through
which communication with the chamber 13 can be es-
tablished. This vent includes a tubular conduit 26
which axially extends through the plate. During assem-
bly of the device 10 the conduit 26 is employed in
flushing and delivering the working fluid to the cham-
ber. Once the end plates 12 are secured to the shell 11,
a selected working fluid is deposited in place and a vac-
uum is drawn through the conduit 26 whereupon the
conduit is "pinched" or otherwise hermetically sealed.
With the heat transfer device 10 thus assembled, it is
readied for employment in a known manner consistent
with the employment of heat pipes.
It should readily be apparent that the heat transfer
device 10, as heretofore disclosed, is assembled em-
ploying relatively simple and economical techniques,
while a sustained and predictable restraint of the wick
14 is achieved, even when the device is employed at el-
evated temperatures over prolonged operative periods.
Although the invention has been herein shown and
described in what is conceived to be the most practical
and preferred embodiment, it is recognized that depar-
tures may be made therefrom within the scope of the
invention, which is not to be limited to the illustrative
details disclosed.
What is claimed is:
1. An improved heat transfer device comprising:
A. an elongated shell of a tubular configuration;
B. a tubular wick concentrically related to said shell
and seated therein;
C. means for supporting said wick in contiguous en-
gagement with the internal surfaces of said shell in-
cluding,
1. a perforated body of a tubular configuration,
2. means for facilitating radial expansion of said
body, including means defining a helical kerf ex-
tended along the body, whereby the body is
adapted to be readily deformed in response to ax-
ially applied compressive stress, and
3. means for axially applying compressive stress to
said body, including a pair of end plates inte-
grally connected to said shell at the opposite ends
thereof in contiguous engagement with the oppo-
site ends of said perforated body; and
D. a working fluid confined within said shell.
55
60
65


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