U.S. patent application number 11/005256 was filed with the patent office on 2005-05-05 for leak detection apparatus for a liquid circulation cooling system.
This patent application is currently assigned to DELPHI TECHNOLOGIES, INC.. Invention is credited to Bhatti, Mohinder Singh.
Application Number | 20050092070 11/005256 |
Document ID | / |
Family ID | 33477232 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050092070 |
Kind Code |
A1 |
Bhatti, Mohinder Singh |
May 5, 2005 |
Leak detection apparatus for a liquid circulation cooling
system
Abstract
A leak detection apparatus includes one or more detection
devices that envelope the various pipe joints of a liquid
circulation cooling system. In one approach, the detection devices
include a pair of conductors separated by a wicking material
impregnated with a crystalline salt that provides a low resistance
electrical path between the conductors in the presence of a leak.
In another approach, the detection devices include a pair of
dissimilar metal mesh electrodes separated by an
electrolyte-impregnated wicking material to form a water-activated
battery that energizes an alarm in the presence of a leak. In
either case, the electrodes and wicking material may be encased
with a water-activated sealing material that hardens in the
presence of a leak to contain the leakage.
Inventors: |
Bhatti, Mohinder Singh;
(Amherst, NY) |
Correspondence
Address: |
Patrick M. Griffin
DELPHI TECHNOLOGIES, INC.
P.O. Box 5052
Mail Code: 480-410-202
Troy
MI
48007-5052
US
|
Assignee: |
DELPHI TECHNOLOGIES, INC.
|
Family ID: |
33477232 |
Appl. No.: |
11/005256 |
Filed: |
December 6, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11005256 |
Dec 6, 2004 |
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10684069 |
Oct 9, 2003 |
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6826948 |
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Current U.S.
Class: |
73/40 |
Current CPC
Class: |
G01M 3/045 20130101;
G01M 3/188 20130101 |
Class at
Publication: |
073/040 |
International
Class: |
G01M 003/04 |
Claims
1. Leak detection apparatus for a liquid cooling system having
coolant pipes and at least one pipe joint, comprising: a wicking
material applied to an exterior periphery of said pipe; an
electrical detector including first and second spaced electrodes
formed of different metals and disposed on said wicking material; a
crystalline electrolyte activating agent impregnated into said
wicking material that is operative when leaked coolant soaks into
said wicking material for forming a coolant activated battery that
produces an electrical voltage and current flow between said first
and second electrodes when coolant leaks into said wicking
material; circuitry coupled to said electrical detector for
indicating the presence of a coolant leak when said electrical
voltage and current flow are produced; and a superincumbent layer
of material surrounding said electrical detector and wicking
material that is operative on contact with said leaked coolant for
hardening to form a seal that contains said leaked coolant; wherein
said coolant is water, and said superincumbent layer comprising at
least one of hydrophobic polyurethane form or resin, epoxy resin,
sodium-polyacrylate gel, and simple plaster-of-paris.
2. (canceled)
3. (canceled)
4. Leak detection apparatus for a liquid cooling system having
coolant pipes and at least one pipe joint, comprising: a wicking
material applied to an exterior periphery of said pipe; an
electrical detector including first and second spaced electrodes
disposed on said wicking material, said first and second electrodes
being in the form of plates oriented substantially perpendicular to
a longitudinal axis of said coolant pipe, with a portion of said
wicking material being disposed between said first and second
electrodes; an activating agent impregnated into said wicking
material that is operative when leaked coolant soaks into said
wicking material for altering an electrical parameter of said
electrical detector; circuitry coupled to said electrical detector
for indicating the presence of a coolant leak in response to said
altering of said electrical parameter; and a dye material
impregnated into said wicking material that is operative when
leaked coolant soaks into said wicking material for dying said
wicking material or provide a visual indicator of the leaked
coolant.
5. The leak detection apparatus of claim 1, further comprising: an
upper and lower strip of porous fabric covering said first and
second spaced electrodes to protect and insulate said first and
second spaced electrodes from said pipe.
Description
TECHNICAL FIELD
[0001] The present invention is directed to liquid circulation
cooling systems for electronic devices and the like, and more
particularly to apparatus for detecting, locating and isolating
coolant leaks at the pipe joints of such systems.
BACKGROUND OF THE INVENTION
[0002] Liquid cooling is finding increased application in the
electronics industry due to the limited heat dissipation capability
of forced air cooling systems and the desire to minimize cooling
system noise levels. FIG. 1 depicts a liquid cooling system 10 for
one or more heat producing electronic devices 12. The device 12 is
typically mounted on a circuit board 14, and its upper surface is
secured to a cold plate 16 of cooling system 10 by thermal paste,
thermal interface material or other means so that heat generated by
the device 12 is conducted to the cold plate 16. The cold plate 16
is provided with inlet and outlet pipes 16a, 16b through which a
liquid coolant such as water or a water-glycol solution is
circulated. The coolant is stored in a tank or reservoir 18, and a
pump 20 draws coolant out of tank 18 for delivery to the cold plate
inlet pipe 16a. Heated fluid exiting cold plate 16 through outlet
pipe 16b is supplied to a heat exchanger 22 before being returned
to the tank 18. A cooling fan 24 driven by electric motor 26 forces
ambient air through the heat exchanger 22, so that the heat
transferred from device 12 to the fluid in cold plate 16 is
subsequently transferred from the fluid in heat exchanger 22 to
circumambient air.
[0003] The potential for fluid leaks is a significant concern,
particularly in electronic systems where the leaked fluid can
damage various electronic devices and potentially create a risk of
electrocution or fire. As in any liquid (single phase or
multi-phase fluid) circulation system, the most likely sources of
leakage in the system 10 are the pipe joints. In the system of FIG.
1, for example, the inlet 16a, 18a, 20a, 22a of each device 16, 18,
20, 22 is coupled to the outlet 16b, 18b, 20b, 22b of another
device by a connecting pipe 28, 30, 32, 34, and there is a pipe
joint at each such coupling. In the system of FIG. 1, the
connecting pipes 28, 30, 32, 34 have an inside diameter that
matches the outside diameter of the inlet or outlet pipe to which
it is coupled, and a clamp 36 prevents the pipes from becoming
uncoupled. Other possible coupling configurations are depicted in
FIGS. 2-4, described herein. Although the coupled pipes can be
soldered or otherwise sealed to prevent fluid leakage, the
possibility of fluid leakage remains due to sealing defects or
imperfections that occur over time.
[0004] Various systems have been devised to address the
aforementioned leakage concerns, most of which include one or more
leak detection devices and an alarm or other warning device to
alert an operator upon detection of leakage. The detection device
typically takes the form of a pair of electrodes separated by an
absorbent material that is insulative in the absence of fluid but
which dissolves or becomes conductive in the presence of fluid. A
circuit responsive to the resistance between the electrodes
activates the alarm when a change in resistance indicative of fluid
leakage is detected. See, for example, the U.S. Pat. Nos.
4,922,232; 4,974,739; 5,172,730; 5,176,025; and 5,918,267 which
pertain to leak detection in pipelines, and the U.S. Pat. Nos.
4,870,447 and 5,086,829, which pertain to leak detection for liquid
circulation cooling systems.
SUMMARY OF THE INVENTION
[0005] The present invention is directed to an improved leak
detection apparatus that is particularly suited to liquid
circulation cooling systems having pipe joints, including detection
devices that envelope the various pipe joints of the cooling
system. According to a first embodiment, the detection devices
comprise a pair of conductors separated by a wicking material
impregnated with a crystalline salt that provides a low resistance
electrical path between the conductors in the presence of a leak.
According to a second embodiment, the detection devices comprise a
pair of dissimilar metal mesh electrodes separated by an
electrolyte-impregnated wicking material to form a water-activated
battery that energizes an alarm in the presence of a leak. Both
embodiments optionally are encased with a water-activated sealing
material that hardens in the presence of a leak to contain the
leakage.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The present invention will now be described, by way of
example, with reference to the accompanying drawings, in which:
[0007] FIG. 1 is a diagram of a Prior Art liquid circulation
cooling system for electronic devices.
[0008] FIG. 2 depicts a leak detection and containment device for a
pipe joint of the system of FIG. 1, including a pair of radially
displaced conductor sleeves.
[0009] FIGS. 3 and 4 depict a leak detection and containment device
for a pipe joint of the system of FIG. 1, including a pair of
laterally displaced conductor bands. The device of FIG. 3 is
depicted in the context of a butt-type pipe joint with an internal
sleeve, and the device of FIG. 4 is depicted in the context of a
barb-type pipe joint.
[0010] FIGS. 5A and 5B depict a patch-type leak detection and
containment device according to this invention. FIG. 5A depicts a
plan view, while FIG. 5B depicts a cross-sectional view taken along
line I-I in FIG. 5A.
[0011] FIG. 6 depicts a leak detection circuit used in connection
with the leak detection and containment devices of FIGS. 2, 3, 4
and 5A-5B.
[0012] FIGS. 7A and 7B depict a wrap-type leak detection device
according to this invention including a water-activated battery and
alarm. FIG. 7A depicts an exploded view of the water-activated
battery, and FIG. 7B depicts the water-activated battery of FIG. 7A
as applied to a pipe joint of the system of FIG. 1.
[0013] FIGS. 8A and 8B depict a block-type leak detection device
according to this invention including a water-activated battery and
alarm. FIG. 8A depicts an exploded view of the water-activated
battery and a pipe joint, and
[0014] FIG. 8B depicts the water-activated battery of FIG. 7A as
applied to the depicted pipe joint.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] The present invention is described in the context of a
circulated water cooling system generally of the type designated by
the reference numeral 10 in FIG. 1. However, it will be appreciated
by those skilled in the art that the embodiments described herein
are also applicable to other types of circulated liquid cooling
systems, and also to systems with stagnant fluid as in
pool-boiling.
[0016] The embodiments depicted in FIGS. 2 and 3 are particularly
applicable to cooling system pipe joints of the abutment type in
which two similarly sized pipes 40 and 42 separated by a small gap
43 are joined by an internal sleeve 44 having an outside diameter
equal to or slightly larger than the inside diameter of the pipes
40 and 42. Although not depicted in FIGS. 2-3, the sleeve 44 or the
pipes 40, 42 may be coated with a sealing material that is
compressed between the sleeve 44 and the pipes 40, 42 to prevent
leakage of fluid circulated therethrough.
[0017] Referring particularly to FIG. 2, the reference numeral 50
designates a leak detection and containment apparatus where the
electrodes are defined by the radially spaced metal screens 52 and
54. The screens 52 and 54 may be formed of copper or aluminum for
example, and are coupled to an external circuit such as depicted in
FIG. 6 by the external conductors 56 and 58, respectively. The
screens 52 and 54 are separated from the pipes 40, 42 and from each
other by intervening layers of a wicking material 60 that absorbs
coolant that may ooze from the pipe joint and acts to soak up and
hold the oozing coolant until the joint can be repaired. The
wicking material 60, which may be formed of felt for example, is
preferably impregnated with a crystalline salt such as
sodium-bicarbonate or sodium-chloride. When dry, the wicking
material 60 is insulative in nature to establish a high-resistance
electrical path between the screens 52 and 54; when moistened by
leaking coolant at the pipe joint, the crystalline salt dissolves,
forming a highly ionic low-resistance electrical path between the
screens 52 and 54. In systems where the coolant itself is highly
conductive, impregnation of the wicking material with crystalline
salt can be omitted. If desired, the wicking material 60 can
additionally be impregnated with a dry dye material such as cobalt
chloride that is dissolved by leaking coolant; in such event, the
dye produces a visible stain on the detection apparatus 50,
allowing a user to visually identify the location of a detected
leak. Optionally the screens 52, 54 and wicking material 60 are
enveloped by a superincumbent layer of sealing material 62 designed
to harden and seal the leak on contact with the coolant. If the
coolant is water, for example, the sealing material may be a
water-activated material such as hydrophobic polyurethane foam or
resin, epoxy resin, sodium-polyacrylate gel, or simple
plaster-of-paris. The apparatus 50 is preferably manufactured in
the form of a rectangular strip that is wrapped around some or all
of the pipe joints of the cooling system 10, particularly those
joints located in proximity to sensitive electronic devices or
other electrical equipment where a leak would cause damage and/or
pose an electrical hazard.
[0018] Referring to FIG. 3, the reference numeral 70 designates a
leak detection and containment apparatus where the electrodes are
defined by the axially spaced metal bands 72 and 74. The bands 72
and 74 may be formed of copper or aluminum for example, and are
coupled to an external circuit such as depicted in FIG. 6 by the
external conductors 76 and 78, respectively. A sleeve of wicking
material 80 surrounds the pipes 40, 42 in the vicinity of the gap
43, and the bands 72 and 74 are secured to opposite axial ends of
the wicking material 80 as shown. As in the embodiment of FIG. 2,
the wicking material 80 separates the bands 72 and 74 from the
pipes 40, 42 and from each other; and additionally in this
embodiment, the bands 72, 74 serve as clamps to hold the wicking
material 80 in place. As discussed above, the wicking material 80
may be formed of felt for example, and is impregnated with a dry
dye material and crystalline salt to facilitate both visual and
electrical detection of coolant leakage. And as with the embodiment
of FIG. 2, the bands 72, 74 and wicking material 80 are optionally
enveloped by a superincumbent layer of sealing material 82 designed
to harden and seal the leak on contact with the coolant.
[0019] Referring to FIG. 4, the reference numeral 90 designates a
leak detection and containment apparatus essentially as shown in
FIG. 3, but as applied to a barb-type pipe joint between different
sized pipes 92 and 94. As in the embodiment of FIG. 3, a sleeve of
wicking material 96 surrounds the pipes 92, 94 in the vicinity of
the pipe joint, and metal bands 98 and 100 are secured to opposite
axial ends of the wicking material 96. Conductors 102 and 104
connect the bands 98 and 100 to an external circuit such as
depicted in FIG. 6. And as with the embodiments of FIGS. 2-3, the
bands 92, 94 and wicking material 96 are optionally enveloped by a
superincumbent layer of sealing material 106 designed to harden and
seal the leak on contact with the coolant.
[0020] Referring to FIGS. 5A-5B, the reference numeral 110
generally designates a patch-type version of the above-described
pipe joint leak detection devices that is particularly adapted for
detecting leaks from a flat surface in the liquid cooling loop of
cold plate 16. A sheet of metal foil tape 112 has a rectangular
central opening 112a covered by a sheet of wicking material 114
that is somewhat larger than the opening 112a so that the margins
of the wicking material 114 adhere to the foil tape 112. First and
second conductor bars 116, 118 are adhered to foil tape 112
oppositely about the wicking material 114, so that the electrical
resistance between conductor bars 116 and 118 is determined by the
combined resistance of the intervening wicking material 114 and the
marginal portions 112b, 112c of the foil tape 112. As the wicking
material 114 moistens due to a coolant leak, the combined
electrical resistance decreases, and a circuit such as depicted in
FIG. 6 coupled to the conductor bars 116, 118 via wires 120, 122
detects the resistance drop as an indication of coolant leakage. As
with the previously discussed embodiments, the wicking material 114
may be impregnated with dry dye and crystalline salts to facilitate
visual and electrical leak detection, and the apparatus may be
optionally enveloped by a superincumbent layer of sealing material
124 designed to harden and seal the leak on contact with the
coolant.
[0021] FIG. 6 depicts a leak detection circuit designed to
interface with the above-described leak detection devices,
designated in FIG. 6 by the detector 140. A power source such as
battery 142 is coupled to a relay coil 144 via a Darlington
transistor pair 146 comprising the individual transistors 148 and
150. When the Darlington pair 146 is conductive, the relay coil 144
is energized to activate a set of contacts 156 that in turn
activate an alarm to alert the operator that a coolant leak has
been detected. The resistor 154 and leak detector 140 couple the
base of transistor 148 to the positive terminal of battery 142,
while the pull-down resistor 152 couples the base of transistor 148
to the negative terminal of battery 142. The normal resistance of
detector 140 is relatively high so that the pull-down resistor 152
biases the Darlington pair 146 non-conductive. In the event of a
coolant leak, however, the resistance of detector 140 drops
precipitously, biasing the Darlington pair 146 conductive to
activate the alarm. Advantageously, the circuit elements 144-154
may be replicated to provide a detection circuit for each leak
detector present in a system 10.
[0022] FIGS. 7A-7B and 8A-8B depict leak detection devices having
an integral coolant-activated battery that interfaces directly to
an alarm device, thereby eliminating the need for remote resistance
detection circuitry and batteries that must be periodically
replaced.
[0023] FIGS. 7A-7B depict a detection apparatus 160 in the form of
an elongated strip that is intended to be wrapped around a pipe
joint as depicted in FIG. 7B. When the integral battery is
activated, an alarm 178 (such as a piezo-electric sounder) coupled
to the apparatus 160 via the wires 174 and 176 sounds to alert the
operator or user of the coolant leakage. Referring to FIG. 7A, the
apparatus 160 comprises first and second electrode strips 162 and
164 separated by a strip of wicking material 166, and upper and
lower strips of porous fabric 168, 170 covering the electrode
strips 162, 164. The porous fabric layers 168, 170 serve to protect
the respective electrode strips 162, 164, and also to insulate the
electrode strips 162, 164 from pipe 172, and from each other if the
wrapping results in any overlap. The electrode strips 162, 164 are
formed of a screen or mesh material so that leaked coolant soaks
into the wicking material 166, and the wicking material is
impregnated with crystalline electrolyte that is non-conductive in
its dry state. In the illustrated mechanization, one of the
electrode strips 162, 164 is formed of aluminum, while the other is
formed of copper, so that an aluminum-copper cell is activated in
the event of coolant leakage to produce an output voltage of
approximately 1.2 volts across lines 174, 176. The current produced
by the cell is proportional to the active area of the electrodes
162, 164, which increases as leaked coolant soaks into the wicking
material 166. Other electrode combinations such as copper and
magnesium are also possible.
[0024] FIGS. 8A-8B depict a detection apparatus 180 comprising
first and second blocks 182 and 184 that are clamped together about
a butt-joint of two equal diameter pipes 186, 188. As depicted in
FIG. 8A in respect to block 182, each of the blocks 182, 184
comprises a stack of plates that form one or more coolant activated
battery cells. The exterior periphery of the stack is covered by an
insulative layer 190, and each stack has a semi-cylindrical recess
that is complementary to the exterior periphery of the pipes 186,
188. A porous insulative layer is also applied to the pipes 186,
188 in the event that the pipes 186, 188 are conductive. Each
battery cell includes an aluminum plate 192, a layer of wicking
material 194 and a copper plate 196 in succession, and each cell is
separated by an insulator plate 198. The various aluminum plates
192 are electrically coupled by internal inter-connects, as are the
various copper plates 196. As shown in FIG. 8B, a pair of
conductors 200, 202 couple the battery cells of blocks 182 and 184
in parallel, and the wires 204, 206 couple the battery cells to the
alarm 208, which may be a piezoelectric sounder as mentioned above.
As with the embodiment of FIGS. 7A-7B, the wicking material 194 is
impregnated with crystalline electrolyte that is dissolved by
leaked coolant to activate the battery cells.
[0025] In summary, the present invention provides a reliable and
cost-effective means of quickly detecting and locating leaked
coolant in a liquid-circulated cooling system 10. While the
invention has been described in reference to the illustrated
embodiments, it will be understood that various modifications in
addition to those mentioned herein will occur to those skilled in
the art. For example, the size and shape of the detection apparatus
may be varied to suit a given application, materials other than
those mentioned herein may be used, and so forth. Additionally, it
is possible to apply two or more staged detection devices to a
single location; in such a mechanization, initial coolant leakage
is detected by a first detection device, and leakage detection by
the second and subsequent detection devices indicates the extent of
the leak. Also, the alarm circuitry may be effective to perform
auto-shutdown or other functions in response to detection of a
coolant leak. Moreover, the leak detection apparatus may be applied
as extensively in a system as desired, and need not be confined
solely to the pipe joints. Thus, it will be understood that devices
incorporating these and other modifications may fall within the
scope of this invention, which is defined by the appended
claims.
* * * * *