U.S. patent number 3,725,566 [Application Number 05/247,398] was granted by the patent office on 1973-04-03 for evaporative cooling and heat extraction system.
This patent grant is currently assigned to The United States of America as represented by the Secretary of the Navy. Invention is credited to Bruno T. Plizak.
United States Patent |
3,725,566 |
Plizak |
April 3, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
EVAPORATIVE COOLING AND HEAT EXTRACTION SYSTEM
Abstract
Heat transfer is accomplished from electronic components by
inserting simaneously both a liquid coolant and a gas into a
chamber having a high heat flux surface forming one side of the
chamber. A porous membrane section forms on opposite side of the
chamber and permits both the gas and a hot vapor formed from the
water to escape. In operation the gaseous flow is used to break up
the liquid coolant film that forms on the high heat flux
surface.
Inventors: |
Plizak; Bruno T. (Philadelphia,
PA) |
Assignee: |
The United States of America as
represented by the Secretary of the Navy (N/A)
|
Family
ID: |
22934771 |
Appl.
No.: |
05/247,398 |
Filed: |
May 1, 1972 |
Current U.S.
Class: |
174/15.1; 62/314;
165/104.13; 165/109.1; 174/16.3; 257/E23.088; 257/E23.099; 62/64;
165/60; 165/104.33; 165/903; 165/911 |
Current CPC
Class: |
H01L
23/467 (20130101); H01L 23/427 (20130101); F28C
3/08 (20130101); H01L 2924/3011 (20130101); Y10S
165/911 (20130101); Y10S 165/903 (20130101); H01L
2924/0002 (20130101); H01L 2924/0002 (20130101); H01L
2924/00 (20130101) |
Current International
Class: |
H01L
23/427 (20060101); H01L 23/467 (20060101); H01L
23/34 (20060101); F28C 3/08 (20060101); F28C
3/00 (20060101); H01l 001/12 () |
Field of
Search: |
;174/15R,16R,DIG.5
;313/21,35,36 ;317/234A ;165/105,104,60,74
;62/304,314,315,316,515,516,64 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gilheany; Bernard A.
Assistant Examiner: Grimley; A. T.
Claims
What is claimed is:
1. A heat exchange system comprising:
A gas porous material spaced a finite distance from said heat
source; connecting means between said heat source
and gas porous material said connecting means connecting means
comprising a spacer between said heat source and said gas porous
material, a first inlet receiving a gas and positioned for
conducting the gas to impinge upon said heat source, and a second
inlet receiving a liquid so that said liquid comes in contact with
said heat source;
and a housing enclosing said heat source, said gas porous material
and said spacer.
2. A heat exchange system according to claim 1 further
comprising:
said gas porous material adapted to be penetrable by gases and
liquid vapor, and impervious to liquid.
3. A heat exchange system according to claim 2 wherein said heat
source is a transistor.
4. A heat exchange system according to claim 1 wherein said housing
and said spacer have adjacent passageways comprising said first
inlet and adjacent passageways comprising said second inlet.
5. A heat exchange system according to claim 4 wherein said housing
further comprises:
a third inlet adapted to provide a passageway for connecting
electrical wiring to said heat source; and
an outlet adapted to discharge liquid, liquid vapor and gas.
6. A heat exchange system according to claim 5 further
comprising:
said housing comprises inner threads;
said spacer being secured on said threads; and
a retaining ring adjacent to said porous material secured on said
threads.
7. A heat exchange system according to claim 6 further
comprising:
an end of said housing being substantially cylindrical in shape;
and
a cap covering said end of said housing.
8. A heat exchange system according to claim 2 wherein said
connecting means further comprises:
a spacer between said heat source and porous material; and
a heat conducting plate between said spacer and said heat
source.
9. A heat exchange system according to claim 8 further
comprising:
a cover connected to said heat conductor plate for forming an
enclosure for said heat source.
10. A heat exchange system according to claim 9 further
comprising:
an electrical connector connected to said cover; and
electrical wiring connected to said electrical connector and said
heat source for providing electrical power to said heat source.
Description
STATEMENT OF GOVERNMENT INTEREST
The invention described herein may be manufactured and used by or
for the Government of the United States of America for governmental
purposes without the payment of any royalties thereon or
therefor.
BACKGROUND OF THE INVENTION
The present invention generally relates to heat transfer systems
and more particularly to systems suitable for cooling of avionics
equipment by the enhancement of enthalpy and heat of vaporization
of suitable coolants.
Many prior known systems for cooling avionic equipment use
variations of the well known heat pipe. The heat pipe is a sealed
thermodynamic system relaying on internal evaporation and
condensation cycles. It comprises an enclosure, a wicking material
lining the internal walls of the enclosure, and a working fluid for
saturating the wick. One end of the heat pipe is called the
evaporator and serves to absorb heat energy. Vapor formed in the
evaporator is then transported to the other end of the heat pipe
called the condenser. Here the heat is released from the heat pipe
by means of the internal condensation of the working fluid to the
internal walls of the heat pipe. The working fluid is then
recirculated to the evaporator end by the capillary action of the
wick where the cycle is repeated.
Certain performance characteristics of the heat pipe including heat
flux handling capacity vary depending on the vertical orientation
of the evaporator end with respect to the condenser. During
aircraft maneuvers this is apt to continually change. Other
limitations of the device include heat extraction dependence upon
operating temperature level, sonic vapor flow velocities, fluid
entrainment flow, wick dryout, internal generation of
non-condensible gases, and shock and vibration problems. In
addition a high heat dissipating component must be mounted to the
heat pipe by suitable means. This introduces thermal impedances
that are detrimental to any heat transfer system.
SUMMARY OF THE INVENTION
It is therefore a general object of the present invention to
provide an improved system for the cooling of avionics equipment.
It is a further object to provide a system that is independent of
attitude or gravity so as to eliminate variation in operational
characteristics during aircraft maneuvers. Another object is to
provide a system whereby the enthalpy and heat of vaporization of
coolants are more effectively utilized and controlled. A further
object is to provide a lightweight system in which all coolant must
become high quality steam before being removed from the system.
Additional objects are to improve the operating temperature level
and to obviate other known limitations on effectiveness of prior
systems.
This is accomplished in accordance with the present invention by
providing a heat transfer system operable as either a closed or
open loop system in which both a liquid coolant and gas are
inserted simultaneously into an area having a heat exchange surface
to be cooled and enclosed so that only the gas and vapor formed
from the liquid coolant may escape through a porous material
provided for such purpose. The porous material is separated from
the heat exchange surface from which heat is to be extracted by a
finite distance. The physical characteristics of the porous
material are such that the material will readily permit the passage
of gas or vapor molecules but will restrict the liquid coolant from
passing quickly through the porous material by its surface tension
properties. The gas is injected under pressure as pulsating or
steady flow through the coolant fluid and against the heat exchange
surface to reduce the thickness of a liquid evaporating film or
thin liquid boundary layer and to break up insulating vapor bubbles
that form adjacent the surface to be cooled thus improving the heat
transfer capability of the device.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an embodiment of the present invention partially in cross
section;
FIGS. 2a and 2b are views of a spacer of FIG. 1;
FIG. 3 is a top view of a transistor of FIG. 1;
FIG. 4 is an alternate embodiment of the invention partially in
cross section to show the operation more precisely; and
FIG. 5 is a top view of the alternate embodiment of FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. 1-3, inclusive, there is shown a system 10
having a housing 11 with a first opening 12 receiving a flow of
liquid coolant through a hose 14 or a comparable substitute such as
piping. The liquid coolant can be water or other coolant with good
heat transfer properties. A second opening 15 receives cabling 16
having electrical wires 17 connected to a transistor 18. The
connection of these wires 17 to transistor 18 is not shown but may
be introduced into the housing of transistor 18 using any suitable
watertight and heat resistant means such as epoxy for a potting
material. The transistor 18 is inserted in the housing 11 and has a
flanged section 19 that abuts shoulder 21. As shown more clearly in
FIG. 3 this flanged section 19 permits water to flow across the
sides of transistor 18. A spacer 25 is threaded to housing 11 and
has teeth 26 symmetrically spaced around it to permit gas injectors
27 to supply gas such as air to the hot surface 28 of transistor
18. The spacer 25 holds transistor 18 in place and spaces it from a
porous membrane 31 forming a cavity 33. The porous membrane 31 can
be a material such as brass and can be matched to the coolant used,
to restrict it by its surface tension from passing through the
porous material until it has boiled and vaporized. This permits the
vapors to readily pass through the porous membrane while inhibiting
the flow of the coolant in liquid form. In this manner, the heat of
vaporization, btu's/lb., of the coolant liquid is utilized to
extract additional heat. The heat transferred as a result of
vaporization will be many times that extracted by an enthalpy
change alone. These porous membranes 31 are well known to those of
skill in the art and are readily available commercially. A
retaining ring 32 is then screwed into housing 11 to hold porous
membrane 31 in place against spacer 25. A cap 37 impervious to the
vapor and gas is then secured over housing 11. An outlet line 38
removes the vapor and gas from housing 11 and may discharge it to a
condenser and a vent for the gas (not shown) for recirculation, or
the vapor and gas can be wasted in an open loop system.
The operation of the device will now be described with reference to
FIGS. 1-3, inclusive. Electric power to high power transistor 18 is
received from leads 17. A coolant is then supplied to the inlet of
housing 11 and flows over the transistor surface. The water passes
along the sides of transistor 18 into the cavity 33 where the
liquid flow is blocked by porous membrane 31. The liquid in cavity
33 vaporizes from the heat of transistor 18. The evaporization rate
of the liquid coolant is further enhanced by the use of gas
impacters 27 directed at the hot surface of transistor 18. The gas
impacters dissipate the surface resulting in a more efficient use
of the liquid coolant. The vapor and gas passage through porous
membrane 31 is shown by arrows. Afterwards, the vapor and gas are
discharged through outlet 33 which may have a pump connected to it
(not shown) for the removal of water vapor and gas for closed or
open cycle operation.
Referring now to FIGS. 4 and 5 an alternate embodiment is shown
having a casing 50 with a flange 51 connected to a plate 52 by
means of screws 53. An integrated circuit chip 54 receives power
from wires 55 through cable 56 and electrical connector 57. A
flanged portion 63 of a spacing ring 61 is connected to plate 52 by
screws 62. The plate 52 must have good heat transfer properties and
could be made of silver or copper. A liquid coolant inlet 64 for
fluid such as water has a line 65 connected to it for supplying the
coolant to a cavity 67. Gas impacters 68 are inserted into the
cavity 67 through retaining ring 61. The gas impacters 68 have a
line 69 for supplying a gas such as air to a hot surface 71 of
plate 52.
In operation the electric power is supplied to chip 54 on lines 55.
The surface 71 becomes heated and a liquid coolant is supplied to
cavity 67 by line 65.
A gas such as air is simultaneously inserted by pulsating or steady
flow into cavity 67 through line 69 and gas jet impacters 68. This
aids in dissipating the liquid film on hot surface 71. The vapors
formed pass through porous membrane 72 which is connected to ring
61. The membrane 72 passes only gas and water vapor and is
impervious to water. The vapor and gas are passed through membrane
72 as shown by the arrows are then wasted to the atmosphere.
An alternative system available to those of skill in the art would
be to trap the vapor and gas passed through membrane 72 and to
recirculate and form a closed loop cycle from the embodiment of
FIGS. 4 and 5.
There has therefore been shown a superior heat extraction and
cooling system that is applicable to high heat flux devices,
components, parts, mounting boards, printed circuit boards, and
equipment. The system provides a method whereby the enthalpy and
heat evaporization of coolants are more effectively utilized and
controlled than in previously used devices. It provides an external
pumping source to provide liquid coolant to the hot surface from
which heat is to be extracted without relying on the capillary
action of any material to provide liquid pumping. Consequently,
this invention is independent of position orientation and is not
affected by gravity or other acceleration effects. The invention
can operate as a closed loop or open loop system. In one embodiment
the coolant is brought into direct and intimate contact with the
surface or surfaces from which heat is to be extracted thus
eliminating intermediate metal, mounting, and bonding thermal
resistances. It operates at a relatively low temperature level,
consistent with component part material temperature limits for a
given heat flux density. The entire surface area is utilized for
heat extraction. This invention will eliminate the adverse effect
of localized film boiling by the constant supply of liquid coolant
as it is evaporated and by gas jet impaction. It will enhance the
rate of vaporization and hence the heat extraction rate by
incorporating gas jet impaction directed through the coolant liquid
and at the surface from which heat is to be extracted.
It will be understood that various changes in the details,
materials, steps and arrangements of parts, which have been herein
described and illustrated in order to explain the nature of the
invention, may be made by those skilled in the art within the
principle and scope of the invention as expressed in the appended
claims.
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