Abstract:
A system and method for cooling a series of heat generating devices arrayed sequentially in the axis of flow for a cooling medium. An inlet manifold contains a stepped chamber whereby cool air is apportioned to several chambers, each chamber containing a heat generating device. An outlet manifold contains a similar stepped chamber whereby heated air is exhausted from the heat generating device. In an embodiment of a disk array, each chamber may hold one or more disk drives. Further, the manifold system may also serve as a mounting bracket for the disk drives.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     a. Field of the Invention  
         [0002]     The present invention pertains generally to forced air cooling systems and specifically to cooling systems containing several heat generating items in the primary axis of airflow.  
         [0003]     b. Description of the Background  
         [0004]     Space constraints of mechanical layouts of electronics systems have forced many devices in a small volume. One such problem exists in arrays of disk drives where some designs place many disk drives in a grid pattern inside an enclosure. In such a system, the airflow of the enclosure is such that the air must flow across several disk drives before exiting the enclosure. As the air flows through the enclosure, each device heats the air flowing past, causing the last device in line to be subject to air heated by the prior devices and suffer marginal cooling.  
         [0005]     Each heat generating device must be cooled to a nominal temperature to maintain its performance standards and useful life. Some devices, such as disk drives, have known performance or longevity degradation at higher temperatures. A key to overall system performance is keeping each device properly cooled. Ideally, each device would be cooled to the same temperature, as the device at the highest temperature is generally more prone to failure.  
         [0006]     In prior systems of disk based storage systems, many disk drives may be aligned along the front of the enclosure. When air is drawn through the enclosure from the front to the rear, each disk drive may be cooled without effecting the cooling of another disk drive.  
         [0007]     In more advanced systems, several disk drives may be arrayed along the axis of the cooling stream. In such systems, the heat of an upstream disk drive may add heat to the airflow, subsequently raising the temperature of downstream disk drives. An additional constraint is the height of the enclosure is desired to be kept to a minimum to allow more enclosures to be placed in a given rack.  
         [0008]     It would therefore be advantageous to provide a system and method whereby several heat generating devices may be sequentially aligned in an airflow axis while keeping the temperature of each device in the nominal operating range. It would be further advantageous if such a system were compact and simple to implement.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention overcomes the disadvantages and limitations of previous solutions by providing a system and method for cooling a series of heat generating devices arrayed sequentially in the axis of flow for a cooling medium. An inlet manifold contains a stepped chamber whereby cool air is apportioned to several chambers, each chamber containing a heat generating device. An outlet manifold contains a similar stepped chamber whereby heated air is exhausted from the heat generating device.  
         [0010]     In an embodiment of a disk array, each chamber may hold one or more disk drives. Further, the manifold system may also serve as a mounting bracket for the disk drives.  
         [0011]     An embodiment of the present invention may include a cooling system for system comprising a plurality of heat generating devices comprising: the plurality of heat generating devices substantially disposed along an array axis; an inlet having an inlet wall, an inlet axis of flow substantially parallel to the inlet wall, and an inlet edge; an outlet having an outlet wall, an outlet axis of flow substantially parallel to outlet wall, and an outlet edge; a first fin comprising a first edge that is disposed between the inlet wall and the inlet edge of the inlet, when the inlet is projected along the inlet axis, the first fin being further disposed between the plurality of heat generating devices; and a second fin comprising a first edge that is disposed between the inlet wall and the first edge of the first fin, when the inlet is projected along the inlet axis, the second fin being further disposed between the plurality of heat generating devices downstream from the first fin.  
         [0012]     Another embodiment of the present invention may include a disk drive storage system comprising: an enclosure having a first face; a plurality of disk drives disposed along an array axis substantially perpendicular to the first face; an inlet having an inlet wall, an inlet axis of flow substantially parallel to the inlet wall, and an inlet edge; an outlet having an outlet wall, an outlet axis of flow substantially parallel to outlet wall, and an outlet edge; a first fin comprising a first edge that is disposed between the inlet wall and the inlet edge when the inlet is projected along the inlet axis, the first fin being further disposed between the plurality of disk drives; and a second fin comprising a first edge that is disposed between the inlet wall and the first edge of the first fin, when the inlet is projected along the inlet axis, the second fin being further disposed between the plurality of disk drives downstream from the first fin.  
         [0013]     The advantages of the present invention are that multiple heat generating devices may be mounted in a compact package and cooled effectively. When the manifold system serves as a mounting bracket and heat sink for the heat generating devices, effective cooling is combined with lower overall system cost. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     In the drawings,  
         [0015]      FIG. 1  is a cross-sectional illustration of an embodiment of the present invention showing a cooling system for a disk drive storage system.  
         [0016]      FIG. 2  is a cross-sectional illustration of an embodiment of the present invention showing a cooling system having a pressurized interior.  
         [0017]      FIG. 3  is a semi-exploded perspective illustration of an embodiment of the present invention showing a disk storage system with a single piece manifold cooling system.  
         [0018]      FIG. 4  is a semi-exploded perspective illustration of an embodiment of the present invention showing a disk storage system comprised of several manifolds.  
         [0019]      FIG. 5  is a cross-sectional illustration of an embodiment of the present invention showing intake and exhaust axes that are not parallel with the line of heat generating devices. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]      FIG. 1  illustrates an embodiment  100  of the present invention showing a cooling system for a disk drive storage system. The disk drives  102 ,  104 ,  106 , and  108  are mounted downstream from an inlet  110 . The inlet  110  has an inlet wall  112  and a inlet edge  114 . Several diverter fins  116 ,  118 , and  120  direct airflow around the disk drives and to the outlet  111 . The outlet  111  has a outlet wall  113  and an outlet edge  115 . Airflow is propelled by a fan  122 , which exhausts into the power supply  124 .  
         [0021]     The airflow paths  126 ,  128 ,  130 , and  132  show the airflow through the embodiment  100 . As the air enters the inlet  110 , a portion is diverted across disk drive  102  by airflow path  126 . Similarly, airflow path  132  shows some air that passes a portion of disk drives  102 ,  104 , and  106  before passing across disk drive  108 . Airflow path  132  may be partially heated when passing over disk drives  102 ,  104 , and  106 , but because only a small portion of the three upstream disk drives are in its path, only a mild heating effect may take place.  
         [0022]     The airflow paths  126 ,  128 ,  130 , and  132  illustrate how an incoming airstream is broken into separate airstreams directed toward each heat generating device. After performing the primary cooling function of the specific device, the airflow paths are reunited and exhausted from the cavity. The primary benefit of splitting the incoming airstream is that cooling air may be directed at each specific heat generating device, with a minimum of pre-heating by other upstream heat generating devices.  
         [0023]     In order to split the incoming airstream for each heat generating device, the diverter fins  116 ,  118 , and  120  are positioned such that the upper lips or edges of the diverter fins are inside the projected area of the inlet. Further, the downstream fins are within the projected area of the inlet and any upstream fins.  
         [0024]     For example, the inlet  110  is comprised of the inlet wall  112  and the inlet edge  114 . The inlet axis is parallel to the inlet wall  112 , and the inlet projects an area along the axis, as shown by the inlet distance  134 . The first fin  116  is projected at a height  136  through the inlet  110 . Similarly, the second fin  118  projects a height  138  and the third fin  120  projects a height  140 . Each downstream fin is within the projected area of the inlet, masked by any upstream fin. In this manner, an incoming airstream may be split and diverted across a specific heat generating device. In the embodiment  100 , the heat generating devices are the disk drives  102 ,  104 ,  106 , and  108 .  
         [0025]     The inlet edge  114  in embodiment  100  is the highest projected edge of the lower portion of the inlet  110 . In other embodiments, the inlet edge  114  may be formed from a wall that is straight or curved, depending on various design factors. For example, a curved duct may be used to convey cool air from one portion of an enclosure to the area near the heat generating devices. In such an embodiment, the uppermost portion of the lower portion of the ductwork would comprise the inlet edge  114 , defining the inlet distance  134  with the inlet wall  112 . The presence of a straight and discrete edge  114  does not limit the invention to the precise embodiment shown.  
         [0026]     Further, the use of terminology as ‘upper’ and ‘lower’ in this application are merely for description purposes and are not meant to limit the invention. The terms ‘upper’ and ‘lower’ are used only to describe the relative position of a particular feature on the particular figure. For example, an inverted version of embodiment  100 , where the inlet is nearest to the lower portion of the embodiment and the outlet near the upper portion is within the scope of the present invention.  
         [0027]     In other embodiments, one or more heat generating devices may be present between the diverter fins. For example, in a disk drive storage system, two or more disk drives may be placed between a pair of diverter fins.  
         [0028]     The fan  122  may be located downstream from the heat generating devices. In some embodiments, a power supply  124  may be located downstream from the heat generating devices. In embodiment  100 , the fan  122  pulls air from the heat generating devices and pushes air into the power supply  124 . In other embodiments, the fan  122  may be located downstream from the power supply  124 . Various configurations may be contemplated by those skilled in the arts while keeping within the spirit and intent of the present invention.  
         [0029]      FIG. 2  illustrates an embodiment  200  of the present invention showing a cooling system having a pressurized interior. The enclosure  202  contains disk drives  204 ,  206 , and  208 .  
         [0030]     The inlet  210  is comprised of an inlet wall  212  and the inlet edge  214 . The inlet edge  214  is the point of least constriction nearest the opening of the chamber  215  containing the heat generating devices. In some embodiments, the ductwork transmitting the airflow into the chamber  215  may have narrow passages prior to entering the chamber  215 . However, the inlet edge  214  is the narrowest point immediately prior to entering the chamber  215  that is opposite the inlet wall  212 .  
         [0031]     The fan  216  provides a positive pressure to the chamber  215 . The exhaust of the fan  216  proceeds through a duct  217  to the chamber  215 .  
         [0032]     Between the various disk drives are diverter fins  218  and  224 . The diverter fin  218  has curved lips  220  and  222  on the upstream and downstream ends, respectively. Similarly, diverter fin  224  has curved lips  226  and  228 . The upstream lips  220  and  226  are designed to split the incoming airflow into separate streams to cool the various disk drives. Similarly, the downsteam lips  222  and  228  are designed to join the streams. Various shapes and sizes of diverter fins may be used by those skilled in the art while maintaining within the spirit and intention of the present invention. In some embodiments, the diverter fins may be identical in size and shape while in other embodiments the fins may be of various heights and shapes.  
         [0033]     The airflow exits the enclosure  202  through the outlet  232 , which is defined by the outlet wall  234  and the outlet edge  236 . Similar to the inlet edge  214 , the outlet edge  236  is the narrowest edge immediately downstream from the chamber  215 . Subsequent ductwork does not effect the position of the outlet edge.  
         [0034]     The power supply  230  is cooled by the air that evacuates the chamber  215 . The power supply may be more tolerant of higher heat than the disk drives  204 ,  206 , and  208  and may therefore withstand the preheated air and less cooling. In embodiments where a power supply is less tolerant than the other heat generating devices, the power supply may be placed upstream from the other heat generating devices.  
         [0035]      FIG. 3  illustrates an embodiment  300  of the present invention showing a disk storage system with a single piece manifold cooling system. The manifold  302  comprises an inlet  304  that has a sloped intake chamber, illustrated by the difference in the inlet height  306  and the height  308 . Many separate chambers  310  are provided to direct airflow from the inlet  304  near the heat generating devices and out the exit  312 .  
         [0036]     The manifold  302  is placed over the backplane  314  to which are attached various disk drives  316 . The disk drives  316  may be engaged directly onto the backplane  314  through a connector. The connector alone or additional mechanical supports may be used to mechanically attach the disk drives  316  to the backplane  314 .  
         [0037]      FIG. 4  illustrates an embodiment  400  of the present invention showing a disk storage system comprised of several manifolds. Each manifold  402 ,  404 , and  406  contains multiple disk drives and serves both as a mechanical support as well as an airflow management device.  
         [0038]     For example, manifold  402  contains disk drives  408 ,  410 , and  412 . Each disk drive may be mounted on standoffs  414 . Fins  416  and  418  are positioned inside the manifold  402  to divert airflow from the inlet  420  and to the outlet  422 . The inlet  420  has the inlet wall  424  and the inlet edge  426 . Similarly, the outlet  422  has the outlet wall  428  and outlet edge  430 .  
         [0039]     The outer cover  432 , shown removed from the assembly, seals manifold  402 . The manifolds  404  and  406  may have a similar cover or may be positioned against each other to form a sealed chamber. In some embodiments, a gasket or other sealing material may be used to create an airtight seal around the chamber enclosing the disk drives, while in other embodiments only a loose fit without an airtight seal may be used.  
         [0040]     The embodiment  400  uses several manifolds that, when stacked together, create a rectangular array of disk drives. Each disk drive is mounted to a manifold and may be connected to a backplane using a cabled connection. The manifold  402  may have the standoffs  414  molded or formed into the manifold  402 . In some cases, the standoffs  414  may be separate mechanical parts. The manifolds  402 ,  404 , and  406  may be held together by fasteners or other mechanisms including snap fit, external mechanisms, or any mechanical engagement. In some embodiments, a single manifold may be removable without having to disturb the neighboring manifolds. Those skilled in the arts may contemplate many different embodiments while keeping within the spirit and intention of the present invention.  
         [0041]     In some embodiments, the manifold  402  may be a thermally conductive material. In such an embodiment, the disk drives  408 ,  410 , and  412  may be mounted using thermally conductive adhesive or in some other manner so as to conduct as much heat from the disk drives to the manifold  402  as possible. In such an embodiment, the manifold  402  may act as a heat sink and dissipate heat into the airstream in addition to the convection of the disk drives themselves.  
         [0042]      FIG. 5  illustrates an embodiment  500  of the present invention showing intake and exhaust axes that are not parallel with the line of heat generating devices. The manifold  502  contains disk drives  504 ,  506 , and  508 . Airflow is from the inlet  510 , through the chamber  511 , and out through the outlet  512 .  
         [0043]     The inlet  510  has an inlet wall  514  and an inlet edge  516 . The inlet height  522  is shown projected along the inlet axis defined by the inlet wall  514 . The first fin  518  has a projected height  524 . Likewise, the second fin  520  has a projected height  526 .  
         [0044]     Similarly, the outlet  512  has an outlet wall  527  and an outlet edge  529 . The outlet height  528  is shown projected along the outlet axis defined by the outlet wall  527 . The second fin  520  has a projected height  530 . Similarly, the first fin  518  has a projected height  532 .  
         [0045]     The embodiment  500  illustrates an embodiment where the inlet axis, an axis defined by the heat generating devices, and the outlet axis are not parallel. In both the inlet and outlet portions of the manifold  502 , the fins  518  and  520  split the incoming and outgoing airflow based on the position of the edges as projected along the incoming and outgoing axes. Various geometries of the fins  518  and  520 , inlet wall  514 , and outlet wall  527  are possible while keeping within the spirit and intent of the present invention.  
         [0046]     In the preceding embodiments, the cooling medium was referred to as air. In other embodiments, various cooling media may be used, including water, glycol, or other liquids, suspensions, or fluid mixtures. Additionally, various gasses may be used in place of air to perform the cooling function.  
         [0047]     The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiment was chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.