Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
2003-10-09
2004-12-07
Cygan, Michael (Department: 2855)
Measuring and testing
With fluid pressure
Leakage
C073S049100, C073S049500, C340S605000
Reexamination Certificate
active
06826948
ABSTRACT:
TECHNICAL FIELD
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
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
16
a
,
16
b
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
16
a
. Heated fluid exiting cold plate
16
through outlet pipe
16
b
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.
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
16
a
,
18
a
,
20
a
,
22
a
of each device
16
,
18
,
20
,
22
is coupled to the outlet
16
b
,
18
b
,
20
b
,
22
b
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.
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. 4,870,477 and 5,086,829, which pertain to leak detection for liquid circulation cooling systems.
SUMMARY OF THE INVENTION
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.
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Bhatti Mohinder Singh
Enzinna Donald John
Reyzin Ilya
Cygan Michael
Delphi Technologies Inc.
Griffin Patrick M.
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