Heat exchange – With impeller or conveyor moving exchange material – Mechanical gas pump
Reexamination Certificate
2001-08-06
2003-12-09
Flanigan, Allen (Department: 3743)
Heat exchange
With impeller or conveyor moving exchange material
Mechanical gas pump
C165S080300, C361S697000
Reexamination Certificate
active
06659169
ABSTRACT:
FIELD OF THE INVENTION
The invention covered by this application is related to devices intended for cooling electronic devices by removing heat by a flow of gas, in particular, air flow, said flow being produced by a blower.
BACKGROUND OF THE INVENTION
The most widespread devices are the ones that comprise a heat exchanger represented by a heat sink, on one surface of which an electronic device (for instance, semiconductor device or computer processor) is installed, while another surface is made in the form of heat dissipating surface. The airflow is produced by a blower (axial fans may serve as a blower).
There are known devices of this type—see, for example, U.S. Pat. No. 5,867,365 “CPU heat sink assembly” published on Feb. 2, 1999 (priority date—Jun. 10, 1997), Int.Cl. H05K 7/20, and U.S. Pat. No. 5,661,638 “High performance spiral heat sink” published on Aug. 26, 1997 (priority date—Nov. 3, 1995), Int.Cl. H05K 7/20.
The design of the device described in U.S. Pat. No. 5,867,365 comprises an axial fan that produces a flow passing by heat exchanging channels of the heat sink. The majority of inlets to heat exchanging channels are located just opposite the axial fan's impeller with a certain number of said channels being placed radially in relation to fan axle.
U.S. Pat. No. 5,661,638 also involves the application of an axial fan. Specific embodiment of device claimed in said patent involves such placement of heat exchanging channels of the heat sink that they are located centrally-symmetrically about the fan axle. To increase the heat exchange area, the heat exchanging channels are made of spiral-like shape and bent backwards in the direction of blower rotation. In this case the fan is installed in a recess made in the heat sink body.
In the above-mentioned designs, the axial fan produces sufficiently high air pressure. However, due to the weak airflow in the area adjacent to fan axle, the conditions for cooling the central part of the heat sink located underneath the fan are unfavorable. In this case non-uniform cooling of the heat sink and electronic device (in our case, processor) will take place. Besides, the energy of airflow outgoing from fan impeller in the axial direction is expended on deceleration and turn in motion before this airflow enters the heat exchanging channels. This fact decreases the speed of airflow passing by the heat exchanging channels, which, in its turn, doesn't allow to obtain good conditions for heat exchange process.
Centrifugal blowers are used much more rarely in the cooling device designs for the purpose of producing airflow.
Specifically, U.S. Pat. No. 5,838,066 “Miniaturized cooling fan type heat sink for semiconductor device” published on Nov. 17, 1998 (priority date—Dec. 16, 1996), Int.Cl. H05K 7/20 offers a design employing a centrifugal blower that is installed to the side of the heat sink. In one particular embodiment of this invention the cooling airflow passes by rectilinear heat exchanging channels of the heat sink.
However, placement of centrifugal blower to the side of the heat sink increases device size. This is so because such location of centrifugal blower leads to insufficient coordination between the direction of channel inlets and direction of airflow supplied from the blower. The loss in airflow energy results in the reduction of airflow motion speed in heat exchanging channels and in the decline of heat exchange efficiency. A portion of energy is also expended on friction against the casing, in which the blower is enclosed.
The closest analogue to the invention being claimed is an invention described in the patent of Japan No 8-195456 entitled “Cooler for electronic apparatus” (priority date—Jan. 17, 1995; application for patent published on Jul. 30, 1996; Int.Cl. H01L 023/467).
Device design comprises a centrifugal fan enclosed in the casing and installed above the heat exchanging channels that are made divergent. Another heat sink surface is made so that the possibility of thermal contact with an electronic device is provided for. The inlet of the centrifugal fan faces the heat sink. The fan produces an airflow that passes by heat exchanging channels and then gets sucked into the inlet of the centrifugal fan.
Since the centrifugal fan operates by suction, there is an area in the central part of the heat sink that is poorly blown around by the airflow (which could be seen from the Fig. presented in the published patent). Therefore, cooling of the heat sink's central part, which is the hottest, is performed ineffectively. This disadvantage results in the uneven cooling of the heat sink. To avoid uneven cooling of the heat sink, one has to raise the fan power. In addition, the device is of quite considerable height because the centrifugal fan is placed above the heat sink.
SUMMARY OF THE INVENTION
The engineering problem to be solved with the help of the invention being claimed herein is the development of a cooler for electronic devices that ensures more uniform cooling of electronic devices due to more effective cooling of the central part of the heat exchange element and the reduction of cooling device size.
Two options of addressing this problem are being claimed.
The essence of the invention in conformity with the first option consists in the following.
A cooler for electronic devices comprises a heat exchange element (i.e. heat sink) with divergent heat exchanging channels made on its one side, while its other side is made so that a possibility of thermal contact with an electronic device is provided for, and a centrifugal blower installed on the heat exchange element in such a way that it provides for the passing of cooling flow by heat exchanging channels.
The centrifugal blower is installed in the center of symmetry of heat exchanging channels. It supplies cooling flow (for instance, airflow) to the central part of heat exchange element. Since the blower impeller is located right opposite the inlets of said heat exchanging channels, the cooling flow is then supplied to channel inlets and as it moves by said channels it cools the heat exchange element down.
Since the centrifugal blower is installed at the same level as the heat exchanging channels are, the size of the device in height is reduced and the cooling flow is directed into the heat exchanging channels without energy expenditures on turning the flow (from axial direction to the radial direction). The latter is explained by the fact that flow turn is effected owing to the properties of centrifugal blower design.
The above-mentioned specific features of the device claimed herein provide for a special cooling pattern, which is characterized by the fact that the hottest part of the heat exchange element (namely, its central part) gets cooled first, and, as compared to the above-described prototype, the entire cooling process proceeds more evenly and without losses that are caused in said prototype by flow turn and friction when the cooling flow (going from the impeller) enters the heat exchanging channels. As a consequence, when using the invention being claimed one would need a blower of lesser power and size.
It is advisable that centrifugal blower be equipped with an impeller of drum type. In this case the impeller has wide enough suction hole that makes it possible to produce a powerful enough flow to cool the central part of the heat exchange element well. Besides, for a given blower capacity, a centrifugal blower with a drum-type impeller has minimal size and rotational speed as compared to centrifugal blowers with an impeller of other type.
For the purpose of increasing heat exchange area, the heat exchanging channels can be made in the form of rows of profiled elements. In particular, these elements can me made in the form of needles.
As a particular embodiment of the invention, the heat exchanging channels may be made spiral-like and bent in the direction of centrifugal blower rotation. This will provide for the prolonged contact between the airflow and heat exchange element surface.
In addition, the heat exchanging channels may be made
Askhatov Nil
Fedoseyev Lev A.
Fedosov Yuriy Igorevich
Lopatinsky Edward
Advanced Rotary Systems LLC
Flanigan Allen
Frishauf Holtz Goodman & Chick P.C.
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