An improved heat transfer device particularly suited for use as an evaporator plate in a diffusion cloud chamber. The device is characterized by a pair of mutually spaced heat transfer plates, each being of a planar configuration, having a pair of opposed surfaces defining therebetween a heat pipe chamber. Within the heat pipe chamber, in contiguous relation with the pair of opposed surfaces, there is disposed a pair of heat pipe wicks supported in a mutually spaced relationship by a foraminous spacer of a planar configuration. A wick including a foraminous layer is contiguously related to the external surfaces of the heat transfer plates for uniformly wetting these surfaces

Eaton, L. R.

English

NASA Technical Reports Server

United States Patent [I91 [ 1 11 3,940,62 1 
Fletcher et al. [451 Feb. 24, 1976 
[541 HEAT TRANSFER DEVICE Primary Examiner-Davis L. Willis 
[ 761 Inventors: James C. Fletcher, Administrator Attorney, Agent, or Firm-Wayland H. Riggins; L. D. 
Wofford, Jr.; John R. Manning of the National Aeronautics and 
Space Administration, witH respect 
[22] Filed: Jan. 21, 1975 
[21] Appl. No.: 542,754 
[ 521 U.S. C1. ................................................ 250/335 
[51] Int. Cl ............................................ .. COlT 5/04 
[ 5 8 ]  Field of Search ...................... 250/335: 165/105 
mi References Cited 
UNITED STATES PATENTS 
3,496,356 211970 Vash et al ........................... 2501335 
[571 ABSTRACT 
An improved heat transfer device particularly suited 
for use as an evaporator plate in a diffusion cloud 
chamber. The device i s  characterized by a pair of mu- 
tually spaced heat transfer plates, each being of a pla- 
nar configuration, having a pair of opposed surfaces 
a heat pipe chamber. Within 
in contiguous relation with the 
es, there is disposed a pair of 
heat pipe wicks supported in a mutually spaced rela- 
tionship by a foraminous spacer of a planar configura- 
tion. A wick including a foraminous layer is contigu- 
ously related to the external surfaces of the heat trans- 
fer plates for uniformly wetting these surfaces. 
3 Claims, 6 Drawing Figures 
to an invention of Larry R. Eaton, 
Huntington Beach, Calif, 
WATER 
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U.S. Patent Feb. 24, 1976 Sheet 1 of 2 3,940,621 
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U.S. Patent Feb. 24, 1976 Sheet 2 of 2 3,940,621 
3,940,62 1 
2 
being of a planar configuration, separated by a contigu- 
ously related spacer formed 0f.a foraminous material. 
It is another object to provide, for use in a diffusion 
cloud chamber, an improved heat transfer device hav- 
5 ing an external surface including an external layer of a 
foraminous material, whereby a uniform wetting of the 
surface is facilitated. 
It is another object to provide;for use in a diffusion 
cloud chamber, an improved internally supported heat 
10 transfer device which includes a pair of m 
spaced heat transfer plates, each being of a 
BACKGROUND OF THE INVENTION eonfiguration, having a pair of opposed first surfaces 
invention relates to heat transfer devices and defining therebetween a heat pipe chamber, a Pair of 
more particularly to a heat transfer device particularly mutually spaced heat pipe wicks disposed within the 
suited for use as an evaporator plate in a diffusion 15 chamber and a foraminous spacer Of a planar COnfigU- 
cloud chamber. rdtion interposed between the wicks in contiguous sup- 
Studies of cloud condensation nuclei require that Porting engagement therewith and a foramino 
precisely controlled supersaturated environments, be- contiguouslY to the external surface Of 
tween 100 percent and 103 percent relative humidity, transfer device for a uniform 
be maintained when employing diffusion cloud cham- 2o thereof* 
vide such an environment are by two 
active surfaces must be precisely and uniformly con- 
trolled to a tolerance of & 0. 
requirement being that the thermally active surfaces be 
uniformly wetted. 
1 
HEAT TRANSFER DEVICE 
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 Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 
85-568 (72 Stat. 435; 42 U.S.C.. 2457): 
hers. Unfortunately, diffusion chambers used to pro- 
stringent requirements. The first being that thermally 
’ These and other objects and advantages ar 
through the use of an internally supported heat transfer 
which includes a pair of superimposed layers of metal- 
c. or better. The second 25 lic screen comprising a wick, a foraminous spacer inter- 
posed between the wicks for maintaining the wicks in 
mutually spaced relation, a pair of mutually spaced 
heat transfer plates defining therebetween a heat pipe 
are characterized by high flow fluids Or 30 wicks, and an external surface including a foraminous 
device a pair Of heat pipe wicks, each Of 
the necessary contro!, chamber for receiving said spacer and said pair of 
extended area 
be appreciated, such systems are 
control systems’ As ‘a9 
‘low in ‘e- lay& contiguously related to the external surfaces of the heat transfer es for facilitating a uniform wet- sponse time, and generally inefficient in power usage. 
Moreover, the usual approach of .using multiple heat 
pipes with metal to metal heat transfer regions does not 35 
adequately provide the necessary temperature unifor- 
mity over the extended surfaces. 
In order to achieve uniformly water wetted surfaces, 
ting 
, 
FIG. 
DESCRIPTION OF THE DRAWINGS 
is a diagrammatic view of a diffusion cloud 
chamber within which there is disposed a pair of heat 
trasfer devices, which embody the pinciples of the 
it currently is common Practice to deposit filter Paper instant invention, each being connected with a heat 
on these surfaces and employ the paper 
However, it has been found that, in practice, it is Very 
difficult to assure that uniform wetting will be Fxperi- 
enced under all operating conditions. 
cal heat transfer device which can readily be employed 45 of one-corner of the heat transfer device illustrated in 
as an evaporator plate in a diffusion cloud chamb FIG. 1 depicting one manner in which the heat transfer 
order to overcome. the aforementioned difficulties device is connected with a tubular heat pipe. 
disadvantages. ’ FIG. 4 is a sectioned view taken generally along line 
tion to provide an improved internally supported heat 50 FIG. 5 is an exploded, partially sectioned view of the 
transfer device which includes thermally active sur- 
faces particularly adapted to be reliably and uniformly FIG. 6 is a cross-sectional view taken generally along 
wetted under .substantially all operating conditions 
while the temperatures thereof are precisely and uni. 
DESCRIPTION OF THE PREFERRED 
EMBODIMENT 
formly controlled to facilitate the maintenance of tem- 55 
perature uniformity over the external surfaces of this 
device. Referring now to the drawings wherein like reference 
characters designate like or corresponding parts OBJECTS AND SUMMARY OF THE INVENTION throughout the several views, there is shown in FIG. 1 
It is an object of the instant invention to provide an 60 a diffusion cloud chamber, not designated, within 
improved heat transfer device which can be employed which there is disposed a pair of improved heat transfer 
to overcome the aforementioned difficulties an isad- devices, generally designated 10 and 1 
vantages. the principles of the instant invention 
It is another object to provide an improved heat It is to be understood, of course, th 
transfer device particularly suited for use as apo- 65 chambers, their purposes, and their operations are well 
rator plate for a diffusion cloud chamber. known and understood. Therefore, a detailed descrip- 
It is another object to provide an imp heat tion of the diffusion cloud chamber illustrated in FIG. 1 
transfer device including a pair of heat pipe wicks, each is omitted in the interest of brevity. However, it is to be 
a wick. 40 sink through a tubular heat pipe. 
FIG; 2 is a fragmented plan view of a heat transfer 
of the instant device which embodies he 
invention. 
Therefore, there currently exists a ne a Practi- FIG. 3 is a partially sectioned, fragmented, plan view 
It is, therefore, a general purpose of the instant inv 4-4 Of FIG. 2. 
device shown in FIG. 2. 
line 6-6 of FIG. 3. 
3,940,62 1 
3 
understood that through a use of the cloud chamber, 
cloud nuclei are rendered visible as a consequence of 
the formation thereon of liquid droplets, as they are 
caused to pass through the cloud chamber. 
As shown in the drawings, the devices 10 and 12, 
which embody the principles of the instant invention, 
serve as evaporator plates which are spaced apart a 
suitable distance while a flow of particle-free air is 
established about the surfaces of the devices 10 and 12 
from a delivery conduit 14 extended into the cloud 
chamber. A stream of air bearing cloud nuclei to be 
counted is introduced into the chamber via a conduit 
16 and directed to flow along a linear path extended 
through a zone, not designated, of supersaturation lo- 
cated between the devices 10 and 12. As a practical 
matter, the zone is located at equidistances from the 
devices 10 and 12. The vapor within this region con- 
denses on the nuclei as they are passed through the 
chamber. An optical counter 18 is connected with the 
cloud and serves to count the nuclei, all in a manner 
well understood by those familiar with diffusion cloud 
chambers. As a practical matter, the plates 10 and 12 
are employed for maintaining a suitable temperature 
gradient through the aforementioned zone of supersat- 
uration. 
In practice, a pair of heat sinks 20 is provided and 
connected with the heat transfer devices 10 and 12 via 
a pair of tubular heat pipes, designated 22, of well 
known design. The particular configuration of the heat 
sinks 20, of course, is varied as is desired. For example, 
a group of thermoelectric units including a fan and.thin 
fins can be connected with the heat pipes 22 to thus 
establish a suitable heat rejection system for terrestrial 
application. In a zero-gravity cloud physics laboratory a 
loosely controlled fluid cooled heat sink may be em- 
ployed to provide the necessary heat rejection. 
Turning now to FIG. 2, it is to be understood that 
each of the heat transfer devices, designated 10 and 12, 
is of a common design, and is fabricated in a similar 
manner, and functions in a similar manner to achieve 
similar results. Therefore, it is believed that a detailed 
description of the heat transfer device, designated 10, 
is deemed sufficient to provide a complete understand- 
ing of the instant invention. 
As best shown in FIG. 2 the heat transfer device 10 is 
of a planar configuration. However, it is to be under- 
stood that, where so desired, the heat transfer device 
10 is provided with a toroidal or similar cross-sectional 
configuration. 
Referring now, for a moment, to FIGS. 2 and 5, the 
heat transfer device 10 includes a spacer, generally 
designated 24, formed of a foraminous material, such 
as, for example, double crimped copper screen formed 
from 0.063 diameter wire. Disposed in contiguous en- 
gagement with the spacer 24, at each of its opposite 
sides, there is a heat pipe wick 26, also of a planar 
configuration. As a practical matter, each of the wicks 
26 comprises a double layer of number 100 mesh cop- 
per screen and functions in a manner well understood 
by those familiar with the operation of heat pipes. 
A pair of heat transfer plates, designated 28 and 30, 
is provided in a mutually spaced relationship and de- 
fines therebetween a heat pipe chamber, designated 32. 
Preferably, the plate 30 is provided with a projected 
peripheral lip 34. This lip serves to establish a periph- 
eral wall for the chamber 32 upon which is seated the 
transfer plate 28. In practice, the lip 34 is provided with 
a plurality of suitably spaced reliefs 36, each being 
5 
10 
15 
20 
25 
30 
35 
40 
45 
5 0  
55 
60 
65 
4 
suitably configured to receive therein a coupling pin 
38, which is extended through a coaxially aligned open- 
ing 40 formed in the peripheral zone of the heat trans- 
fer plate 28. The coupling pins 38 are employed for 
uniting the heat transfer plates 28 and 30 to form an 
integrated unit and are welded, soldered or otherwise 
suitably secured to the plates. Moreover, when so de- 
sired, a plurality of spacer blocks 42 are disposed 
within the chamber 32 and are employed for purposes 
of maintaining the heat transfer plates 28 and 30 in 
parallelism. 
As shown in the drawings, each of the heat pipes 22 
is of a tubular configuration and includes a heat pipe 
wick 44, also of a tubular configuration, mated with 
both of the heat pipe wicks 26, and is disposed within a 
tubular chamber 46 defined within a tubular conduit 
48. Hence, it will be appreciated that each of the heat 
pipes 22 provides a suitable flow path for a working 
fluid, not shown, extended between one of the wicks 26 
disposed within the heat pipe chamber 32 and a heat 
sink 20. As a practical matter, any suitable working 
fluid is employed and, where so desired, is introduced 
into the heat pipe chamber 32 via the tubular heat pipe 
chamber 46. 
In order to facilitate a uniform wetting of the external 
surface of the heat transfer devices 10, a layer of num- 
ber 200 mesh copper screen 50 is deposited on the 
external surface of the device 10 and secured in place 
through a use of welds, solder or other suitable means. 
This layer of screen functions as a wick for causing a 
flow of water to be established across the surface. A 
water delivery conduit 52 is, where desired, extended 
into the cloud chamber for delivering water to the 
surface of the heat transfer device 10. In any event, it is 
to be understood that the layer of screen 50 functions 
as an exterior wick for uniformly wetting the surfaces 
of the plate. 
OPERATION 
It is believed that in view of the foregoing descrip- 
tion, the operation of the device will readily be under- 
stood and it will be briefly reviewed at this point. 
With the diffusion cloud chamber assembled in the 
manner hereinbefore described, each of the heat trans- 
fer devices, designated 10 and 12, is provided to serve 
as an evaporator plate. Water is delivered via the con- 
duit 52, to the surfaces of the heat transfer devices 
whereupon the layer of screen 50 serves to uniformly 
wet the external surfaces thereof through a wicking 
action. Within each of the heat transfer devices 10 and 
12 the working fluid is caused to be wicked along the 
internal surfaces of the heat transfer devices 10 and 12 
while the heat sinks 20 perform necessary heat rejec- 
tion functions in a manner well understood by those 
familiar with the heat pipe art. 
It will, therefore, be appreciated that through the 
instant invention it is possible to achieve precise uni- 
form, thermal conditions for thermally active surfaces 
which are uniformly wetted in order to effectively and 
economically establish a zone of super-saturation 
within the diffusion cloud chamber. 
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. 
We claim: 
. _  
3,940,62 1 
5 6 
1. In a diffusion cloud chamber, an improved inter- 
A. means including a pair of mutually spaced heat 
transfer plates, each being of a planar configura- 
tion, having a pair of opposed first surfaces defin- 
ing therebetween a heat pipe chamber; 
face of each heat transfer plate, opposite to the first 
surface thereof, comprising a foraminous sheet 
contiguously related thereto. 
2. The device of claim 1 wherein said spacer is 
formed from a woven material having a relatively low 
mesh number and each wick of said pair of heat pipe 
nally supported heat transfer device comprising: 
B. means defining a pair of mutually spaced heat pipe 
wicks disposed within said chamber and contigu- 
ously related to said pair of first surfaces; 
C. means defining a foraminous spacer of a planar 
configuration interposed between said wicks in 
contiguous supporting engagement therewith; and 
D. means externally related to said chamber for uni- 
formly wetting a selected portion of a second sur- 
wicks comprises a pair of superimposed layers of metal- 
lic screen having a relatively high mesh number. 
3. The device of claim 1 further comprising means 
l o  for connecting said improved evaporator plate to a heat 
sink including a tubular heat pipe having a heat pipe 
wick connected with each wick of said pair of heat pipe 
wicks. * * * * *  
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