1. Field of the Invention
The present invention relates generally to a device for preventing backflow in a cooling system, and more particularly, to a fan check valve having a plurality of flaps, wherein the flaps control airflow in a single direction.
2. Background Information
Enclosed electronic systems, which run on continuous operation, generally employ a system for cooling the enclosure. Most cooling systems typically employ some type of fan or blower. Many cooling systems employ redundant fans that are arranged in parallel. This arrangement is used to guard against catastrophic loss of cooling flow in the event of a single fan device failure. One problem with this type fan configuration is that when one fan fails, the pressure difference across the surviving fan pushes air backwards through the failed fan. This reduces the delivered flow rate that would otherwise be available from the surviving fan(s), a significant fraction of the overall fan output.
To prevent back flow, the normal practice is to add a flap-type device on the exhaust side of the fans. Prior flapper designs include swinging door flaps, multiple slat vanes, and helical vanes for tubeaxial fans. However, prior art designs consume valuable packaging space and may fail to operate properly in situations where the exhaust flow must turn at any angle to the axially discharging flow, as would be encountered for example in the tightly confined chassis space within a server rack drawer. Under these conditions, transverse flow from surviving fan(s) can prevent the flaps from properly sealing a failed fan if the flow traversing the failed fan re-opens the flaps in shear.
Therefore, it would be desirable to provide a device that prevents backflow in a cooling system. The device must overcome problems associated with prior art designs.
It is, therefore, a principle object of this invention to provide a device for preventing backflow in a cooling system.
It is another object of the invention to provide a device for preventing backflow in a cooling system that solves the above mentioned problems.
These and other objects of the present invention are accomplished by the device for preventing backflow in a cooling system disclosed herein.
In an exemplary aspect of this invention, a check valve for an exhaust device is formed from a thin flexible plate. A plurality of flaps is formed in the thin flexible plate. The flaps are arranged in a vertical manner to form at least one column of flaps. One or more stoppers are coupled to a back side of the thin flexible plate. The stopper prevents the plurality of flaps from moving towards the stopper when the pressure reverses in fan fail mode. The backstop function of the stopper may be provided by a bar member, a separate metal or plastic grid attached to the fan, or integral to the chassis, either of which additionally serves as a safety finger guard.
The foregoing and other objectives, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiment of the invention, as illustrated in the accompanying drawings.
The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein like reference numerals indicate like components, and:
The invention will now be described in more detail by way of example with reference to the embodiments shown in the accompanying figures. It should be kept in mind that the following described embodiments are only presented by way of example and should not be construed as limiting the inventive concept to any particular physical configuration.
Further, if used and unless otherwise stated, the terms “upper,” “lower,” “front,” “back,” “over,” “under,” and similar such terms are not to be construed as limiting the invention to a particular orientation. Instead, these terms are used only on a relative basis.
With reference now to the figures, and in particular with reference to
The flaps 14 may be formed in a plurality of different configurations. In accordance with one embodiment, the flaps 14 are formed in a column 20. The fan valve 10 may have one or more columns 20. In the embodiment depicted in
The flaps 14 are designed to align their opening angle with the preferred flow turning direction. In normal operation, each flap 14 independently self-aligns with the flow direction to minimize aerodynamic drag. Minimization of aerodynamic drag is a critical performance consideration, because excess drag requires higher fan speeds, higher acoustic levels, and generally reduces the overall availability of cooling flow. This self alignment is made possible by the tapered cut in each flap 14 wherein each flap's construction allows the connection to behave as a low-bending-force hinge. If the hinge is not thin enough, the flap will not properly align and the resulting angle of incidence with respect to oncoming flow will lead to high drag force and pressure losses which diminish the output of the fan. A higher degree of self-alignment is possible with the flexible material, as compared to fixed solid vane designs.
However, due to curvature of flowstreams over the span of the flap chord, a finite degree of non-alignment is present, which will induce a turning moment of the airstream in the direction of the flapper opening angle. The overall orientation of the flapper assembly thus also functions to turn the airflow in a preferential direction with respect to the initial discharge axis, similar to a set of airflow turning vanes formed by a cascade of flat plates.
The embodiment of the flaps 14 does not rely on the action of gravity for flap 14 closure and therefore may be operated in any direction with respect to gravity. This is a significant advantage over heavy pivoted solid flap designs which rely on gravity to assist closure.
One or more stoppers 22 will be coupled to the plate 12. The stoppers 22 are used to prevent each flap 14 from moving in a direction towards the fan 26. The backstop function of the stopper 22 may be provided by a bar member 22a, a separate metal or plastic grid attached to the fan, or integral to the chassis, either of which additionally serves as a safety finger guard, tab members, or any other mechanism designed to prevent the flaps 14 from moving in a direction towards the stopper 22.
In accordance with one embodiment of the present invention, the stopper 22 is a bar member 22a. Each column 20 of flaps 14 will have a bar member 22a which will run the length of the column 20. The bar 22a is used to prevent the flaps 14 from moving in a direction towards the bar member 22a. Thus, the flaps 14 can only move in a direction away from the bar 22a. Since the flaps 14 can only move away from the bar 22a, backflow through the fan valve 10 is prevented.
A plurality of holes 24 are formed on the plate 12. The holes 24 are used for mounting the fan valve 10 on a fan 26 (
Referring now to
The fan valve 10 is mounted to the exhaust side 28 of the exhaust device 26. The exhaust device 26 is typically used in parallel with other exhaust devices 26 to circulate air and cool electrical components inside an enclosure 40 (
Referring now to
As shown in
It should be understood, however, that the invention is not necessarily limited to the specific process, arrangement, materials and components shown and described above, but may be susceptible to numerous variations within the scope of the invention.
It will be apparent to one skilled in the art that the manner of making and using the claimed invention has been adequately disclosed in the above-written description of the preferred embodiments taken together with the drawings.
It will be understood that the above description of the preferred embodiments of the present invention are susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.