Abstract:
A gas distribution unit for use in a rack, that holds rack-mounted equipment that produces heat during operation, includes a housing defining a cavity, an exhaust port in a top wall of the housing, and at least one intake port configured to provide fluid communication between the cavity and a volume of gas external to the housing, the at least one intake port being at least partially laterally displaced relative to the exhaust port, the housing being configured to be disposed in and coupled to the rack and to direct gas from the cavity substantially directly upward through the exhaust port when coupled to the rack, and at least one fan coupled to and disposed within the housing and configured to draw gas through the at least one intake port, and to force the drawn-in gas out of the gas distribution unit through the exhaust port.

Description:
This application is a division of application Ser. No. 10/121,313, filed Apr. 12, 2002, now U.S. Pat. No. 6,668,565. 

   FIELD OF THE INVENTION 
   The invention relates to cooling of rack-mounted devices. 
   BACKGROUND OF THE INVENTION 
   Each year in the communications and information technology industries, more equipment is arranged to be housed in rackmount enclosures. Equipment housed in these rackmount enclosures produces heat, in large part due to the number of transistors in this equipment. Moore&#39;s Law regarding transistors has held true since Intel® chairman Gordon Moore first proposed this law in 1965: the number of transistors on a micro chip will double every 18 months. The number of transistors is proportional to the thermal load each chip produces, and these chips are prevalent in rack-mounted equipment. Furthermore, operational system advances have allowed more chips to be used in multiprocessing applications, making each server produce even more heat. Thus, technological advances in chip design result in more heat being produced than in prior rack-mounted devices. Heat is undesirable as it affects performance and reliability of the rack-mounted components, e.g., including causing complete failures, and affects the useful life of the components. Often, the heat produced by the rack-mounted components is not evenly distributed in the rack. Unevenly distributed loads in the rack result in uneven heat production, or “hot spots.” 
   SUMMARY OF THE INVENTION 
   In general, in an aspect, the invention provides a gas distribution unit for use in a rack that holds rack-mounted equipment that produces heat during operation. The gas distribution unit includes a housing defining a cavity, an exhaust port in a top wall of the housing, and at least one intake port configured to provide fluid communication between the cavity and a volume of gas external to the housing, the at least one intake port being at least partially laterally displaced relative to the exhaust port, the housing being configured to be disposed in and coupled to the rack and to direct gas from the cavity substantially directly upward through the exhaust port when coupled to the rack, and at least one fan coupled to and disposed within the housing and configured to draw gas through the at least one intake port, and to force the drawn-in gas out of the gas distribution unit through the exhaust port. 
   Implementations of the invention may include one or more of the following features. The exhaust port is defined adjacent a front edge of the housing. The housing has a curved transition between a bottom wall and a front side wall. The gas distribution unit further includes a plenum boot connected to the housing enclosing the at least one intake hole. The boot comprises a flexible material. An end of the boot that is displaced from the housing is configured to be attached to a surface defining a cool-gas port that provides access to a source of cool gas, the displaced end of the boot being configured to surround a perimeter of the cool-gas port. 
   Implementations of the invention may also include one or more of the following features. The housing is configured to be mounted into the rack such that a front wall of the housing is disposed adjacent to a front wall of the rack. The housing includes an interior wall that divides the cavity into a plurality of sub-cavities, and wherein the at least one fan includes at least one fan disposed within each sub-cavity. The gas distribution unit further includes multiple power inputs and a fail-over module electrically coupling the power inputs to the fans, the fail-over module being configured to disconnect a first of the power inputs from a first fan and connect a second of the power inputs to the first fan in response to a loss of power on the first power input. The at least one intake port includes at least one intake port for each sub-cavity, each intake port being associated with a corresponding fan, and wherein the fans each include a ring of fan blades configured and disposed to surround a perimeter of the corresponding intake port, each fan being configured to rotate the ring to draw gas through the corresponding intake port into an interior of the fan and to force the drawn-in gas radially outward through the ring. The gas distribution unit further includes a filter apparatus coupled to the housing and configured to filter gas drawn into the at least one intake port by the at least one fan. 
   In general, in another aspect, the invention provides a modular gas distribution unit for use in a rack that holds rack-mounted equipment that produce heat during operation, the rack-mounted equipment having corresponding fronts. The gas distribution unit includes in combination a housing, a fan connected to the housing and configured to draw gas from a first region external to the housing and force the gas from the first region into a second region internal to the housing, means for directing the gas forced into the second region upward adjacent the fronts of the rack-mounted equipment, and means for guiding cool gas from a source of the cool gas to the first region, the means for guiding being configured to guide the cool gas for adjustable distances to accommodate different separations between the means for directing and the source of cool gas. 
   Implementations of the invention may include one or more of the following features. The means for guiding includes a plenum comprising a flexible material. The means for directing includes an interior wall of the housing dividing a cavity, defined by the housing, into sub-cavities, the gas distribution unit further including at least another fan, with at least one fan disposed in each sub-cavity. The gas distribution unit further includes a redundant power distribution system coupled to provide power to the fans from multiple power sources, and to switch which power source provides power to a particular fan if the power source coupled to the particular fan fails. The gas distribution unit further includes a fan selector configured to control at least one of which combination of the fans will receive power and at which speed at least one of the fans will operate. The gas distribution unit further includes a filter apparatus coupled to the housing and configured and disposed to filter the cool gas. 
   In general, in another aspect, the invention provides a method of cooling equipment modules disposed in a rack of equipment modules, the modules being disposed above one another in the rack, the modules including fans to draw gas from fronts of the modules through the modules and to expel the gas from backs of the modules, the modules having corresponding fronts. The method includes drawing gas from a bottom region near a bottom of the rack, guiding the gas from the bottom region to a lower front region disposed below the fronts of the modules, and forcing the gas upward from the lower front region into an upper front region adjacent the fronts of the modules while inhibiting the gas from being initially forced into portions of the rack other than the upper front region. 
   Implementations of the invention may include one or more of the following features. The inhibiting comprises forcing the gas from the lower front region into the upper front region through an exhaust port configured to guide the gas into the upper front region. The guiding comprises inhibiting gas flow using a flexible plenum coupled to a surface defining an opening that provides access to cool gas, the drawing and forcing comprising drawing and forcing the cool gas. The method further includes filtering the gas drawn from the bottom region. 
   Various aspects of the invention may provide one or more of the following advantages. Higher volumes of colder air can be delivered to rack-mounted components than in other solutions. Reliability of rack-mounted components, e.g., servers, can be increased and hot spots reduced compared to previous designs. More components can be loaded into a rack without loss of reliability. Existing racks can be retrofitted to provide better cooling of rack-mounted components. A compact, high throughput, modular apparatus with few moving parts can be provided to new or existing racks to cool rack-mounted components. Electrical and mechanical failures of a rack-cooling apparatus are guarded against, e.g., with electrical and mechanical redundancy. Cooled air, and/or cooler-than ambient air, can be provided directly to rack-mounted equipment. The invention reduces/minimizes mixing of conditioned air with ambient air and may provide filtration. Variable amounts of cooling may be provided in response to variations of temperature and power consumption of rack-mounted components. 
   These and other advantages of the invention, along with the invention itself, will be more fully understood after a review of the following figures, detailed description, and claims. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  is a perspective view of a rack-mounted equipment system. 
       FIG. 2  is a bottom perspective view of a top, a bottom, and two fans of an air distribution unit of the system shown in FIG.  1 . 
       FIG. 3  is a top perspective view of the bottom and the two fans shown in FIG.  2 . 
       FIG. 4  is a block flow diagram of a process of cooling equipment mounted in the system shown in  FIG. 1  using the air distribution unit shown in  FIGS. 2-3 . 
       FIG. 5  is a simplified side view of the air distribution unit shown in  FIG. 2 , as assembled and disposed as shown in  FIG. 1 , and cross sections of two floors shown in FIG.  1 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   At least some embodiments of the invention provide techniques for cooling rack-mounted equipment. Embodiments of the invention include a modular, self-contained unit for cooling rack-mounted equipment where the unit has multiple fans for drawing air in through at least one input port and forcing the air out at least one exhaust port. The exhaust port is disposed at one end of the unit and directs the forced air upward such that cool air can be forced upward along an end of an enclosed rack of equipment. An exemplary unit has two fans, two input ports, and two exhaust ports. The input ports are designed to mate with the fans to permit the fans to draw air, e.g., from around the rack, from the space beneath the rack, or through an opening in a floor on which the rack rests. Using this unit in a room with an elevated floor under which cool air is provided, the unit can draw cool air in the input ports and force the cool air out of the exhaust ports upward toward the rack-mounted equipment. The dual fans provide mechanical redundancy such that if one fan fails, air will still flow as long as the other fan still operates. Electrical circuitry for driving the fans is also redundant to guard against downtime due to electrical failures. Other embodiments are within the scope of the invention. 
   Referring to  FIG. 1 , rack-mounted equipment system  10  includes a rack  12 , multiple rack-mounted components  14 , and a gas (e.g., air) distribution unit  16 . The rack  12  includes a vented rear  13  and the components  14  may include fans configured to blow air from the components  14  out through the vented rear  13  of the rack  12 . The rack  12  rests upon and is supported by a raised floor  18  disposed above a sub-floor  20 . An air-conditioning unit (not shown) provides cold air (e.g., about 55-60° F.) between the floor  18  and the sub-floor  20 . 
   Referring also to  FIG. 5 , a filter box  8  and a plenum boot  22  of the air distribution unit  16  connect other portions of the air distribution unit  16  to the floor  18  to draw and filter air from beneath the unit  16 , including cool air from beneath the raised floor  18 . The filter box  8  includes a removable filter  9  configured to filter particles from the air that may be harmful to the rack-mounted equipment  14 . The boot  22  is removably coupled (e.g., with hook-and-loop fasteners) to the filter box  8  and is made of a flexible material such as nylon, rubber, or cloth, providing an adjustable length for the boot  22 . The boot  22  is configured to have an expansive spring-force to make the boot  22  self-expanding, e.g., to couple to the floor  18 . The boot  22  provides for guided fluid communication between the air distribution unit  16  and a region between the floors  18  and  20 . The boot  22  provides a passageway for cool air that flows from between the floors  18 ,  20  through one or more openings in the raised floor  18 , and one or more openings in the bottom of the rack  12 . The boot  22  surrounds the opening(s) in the surface to which the boot  22  is attached (e.g., the bottom of the rack  12  or the floor  18 ). A gland plate at the bottom of the rack  12  can be removed to provide access to the floor  18 . Cool air can pass through, and be guided by, the boot  22  to the filter box  8  of the air distribution unit  16 . The boot  22  can be removed such that the bottom of the boot  22  is above the bottom of the rack  12 , allowing ambient air near the bottom of the rack  12  to be drawn into the boot  22  or directly into the filter box  8 . 
   Referring to  FIGS. 2-3 , the air distribution unit  16  includes a top or cover  24 , a bottom  26 , and two fans  28 ,  30 . The bottom  26  is configured to mount to the rack, e.g., with tabs  21  that fit into mating receptacles on vertical rails  23  in the rack  12 , such that the unit  16  is rack mountable. The tabs  21  may be adjusted to various locations on a back wall of the bottom  26  such that the location of the unit  16  in the rack  12  is adjustable (e.g., vertically within the rack  12 ). Alternatively, or additionally, to being rack mountable, the bottom  26  may be configured to rest upon trays  25  disposed within the rack  12  that are mounted to the rails  23  in the rack  12 . The top  24  fits over and screws into the bottom  26  to cover the bottom  26  except for a grated end section  27 . The top  24  and the bottom  26  are made of appropriate materials such as metal, plastic, or wood. The top  24  includes holes for attaching, e.g., screwing, the fans  28 ,  30  to the top  24 . The top  24  further includes electrical lines for conveying power and electrical connectors for connecting to the fans  28 ,  30  to transfer power to the fans  28 ,  30 . 
   The bottom  26  includes a dividing wall  29  that separates an interior chamber of the unit  16  into two smaller chambers  31 ,  33 . The fans  28 ,  30  are mounted to the top  24 , the top  24  is connected to the bottom  26 , and the fans  28 ,  30  are configured for radially outward air flow from the fans  28 ,  30 . With this arrangement, the only, or at least primary, opening in the chambers  31 ,  33  for air is an exhaust port  35  that is divided into two. An end  41  of the bottom  26  is curved to direct air flowing from the fans  28 ,  30  to the exhaust port  35  outwards from the interior of the unit  16  through and perpendicularly away from a plane of the top  24  and the grate  27 . The bottom  26  also includes two openings or input ports  32 ,  34  for permitting air to flow through the bottom  26  into the unit  16 , and more particularly into the fans  28 ,  30 . 
   The fans  28 ,  30  are configured to be mounted to the top  24 , e.g., with screws, in alignment with the input ports  32 ,  34  in the bottom  26  when the top  24  is connected to the bottom  26 , e.g., by fastening the top  24  and bottom  26  together. The fans  28 ,  30  are also configured to receive air flowing through the input ports  32 ,  34 . Further, the fans  28 ,  30  are configured to rotate about respective hubs  36 ,  38  that include internal motors (not shown), fixed top portions  40 ,  42  that mount to the top  24 , and rotating lower portions  44 ,  46  that can rotate relative to the top portions  40 ,  42 . The motors are configured to rotate the lower portions  44 ,  46  in a clockwise direction when viewed from above as in FIG.  3 . The fans  28 ,  30  may be, e.g., model R2E220 fans made by EBM of Farmington, Conn. (although numerous other fans including fans made by other manufacturers are acceptable and can be used as the fans  28 ,  30 , including to replace the R2E220 fans). The fans  28 ,  30  can have multiple speeds of operation to thereby force air (or other gases) out of the exhaust port  35 . 
   Rings  58  of fins or blades  48  of the fans  28 ,  30  are angled relative to a radial direction of the fans  28 ,  30  such that rotation of the rings  58  by the motors will draw air through the input ports  32 ,  34  into internal regions  50 ,  52 , of the fans  28 ,  30 , that are in fluid communication with the input ports  32 ,  34 . The rotation of the fans  28 ,  30  will force the drawn-in air out of the fans  28 ,  30  from the internal regions  50 ,  52 , as indicated by arrows  54 ,  56 , radially outward into the chambers  31 ,  33 . Preferably, the internal regions  50 ,  52  span areas at least as large as areas spanned by the input ports  32 ,  34  such that air will flow only (or substantially only) into the unit  16  through the input ports  32 ,  34 . 
   To supply power to the fans  28 ,  30 , the bottom  26  includes two power ports  102 ,  104 , connected to two switches  112 ,  114 , via fail-over circuitry  110 . The power ports  102 ,  104  are configured to receive power cord connectors, e.g., standard three-prong connectors, or other connectors as appropriate for the power being supplied. The fail-over circuitry  110  is configured to connect the port  102  to both of the switches  112 ,  114  in a normal mode. The circuitry  110  is further configured to detect a failure in power supply from the port  102  and, in response to the detected failure, couple the port  104  to the switches  112 ,  114 , in a fail-over mode. The circuitry  110  is further configured to provide independent fusing of the fans  28 ,  30 , such that if one of the fans  28 ,  30  fails, then only the other of the fans  28 ,  30  will receive operating power. The circuitry  110  also provides independent thermal protection of the fans  28 ,  30 . If the winding of either of the fans  28 ,  30  gets too hot, then the circuitry  110  will shut that fan  28 ,  30  off. An indication can be provided showing that either or both of the fans  28 ,  30  have been shut off. The switches  112 ,  114  are coupled through lines running up the dividing wall  29 , through connectors to the cover  24 , through lines running along the cover  24 , and through connectors to the fans  28 ,  30 . The connectors can be, for example, quick-disconnect connectors. 
   The switches  112 ,  114  include respective buttons for selecting which, or both, of the fans  28 ,  30  will operate when the unit  10  is powered up. Pressing on the buttons will actuate/de-actuate the respective switches  112 ,  114 . Actuating the switches  112 ,  114  causes the switches  112 ,  114  to close, coupling the fail-over circuitry  110  to the fans  28 ,  30 , and de-actuating the switches  112 ,  114  causes the switches  112 ,  114  to open, producing a break in the coupling of the circuitry  110  to the fans  28 ,  30 . The buttons, or separate selectors, may provide for selecting speed settings for either or both of the fans  28 ,  30  as appropriate. 
   Referring to  FIGS. 1-3 , assembly and placement of the air distribution unit  16  is relatively simple, can be performed quickly, and facilitates disassembly for repair or replacement of parts. The fans  28 ,  30  are screwed to the top  24 , connecting the fans  28 ,  30  to the connectors for transferring power. The top  24 , with the mounted fans  28 ,  30  is aligned with respect to the bottom  26  and snapped to the bottom  26 , coupling corresponding electrical connectors on the top  24  and bottom  26  for transferring power to the fans  28 ,  30 . The filter box  8  is secured, e.g., with screws, to the bottom  26 . The filter box  8  can be unscrewed from the bottom  26 , the top  24  can be unsnapped from the bottom  26 , and the fans  28 ,  30  unscrewed from the top  24  as desired to repair or replace the fans  28 ,  30 , clean the unit  16 , or make any other adjustments or repairs desired. Alternatively, the unit  16  can be assembled such that the unit  16  is not easily disassembled, helping to improve reliability of, and inhibit tampering with, the unit  16 . 
   The unit  16  is placed in the rack  12 , connected to one or more sources of power, and arranged to draw air as desired. The unit  16  is put in the rack  12 , e.g., by being mounted to the rack  12  (e.g., by inserting the tabs  21  in the rails  23 ) or rested on one of the trays  25  in the rack  12 . The height of the unit  16  relative to the floor of the rack  12  may be adjusted by selecting which tab locations to use to mount the unit  16  to the rack  12  if multiple locations are provided. Power cords are connected to the power ports  102 ,  104 , preferably to couple an AC power source (e.g., a wall socket or an Uninterruptible Power Supply outlet) to the port  102 , and to couple a battery to the port  104 . The filter box  8  is connected to the boot  22  with the boot  22  surrounding the perimeter of the filter box  8  to facilitate drawing cool air from between the floors  18 ,  20  into the air distribution unit  16 . The boot  22  is connected to the bottom of the rack  12 , or to the floor  18 , surrounding a hole providing access to the area between the floors  18 ,  20 . Alternatively, the boot  22  can be removed to permit drawing of air from below the rack  12  (that will be cooler than ambient air higher up) into the air distribution unit  16 . 
   In operation, referring to  FIG. 4 , with further reference to  FIGS. 1-3 , a process  70  for cooling the rack-mounted components  14  using the air distribution unit  16  includes the stages shown. The process  70 , however, is exemplary only and not limiting. The process  70  can be altered, e.g., by having stages added, removed, or rearranged. 
   At stage  72 , the air distribution unit  16  is installed in the rack  12 . The air distribution unit  16  is placed at the bottom of the rack  12 , e.g., by mounting the unit  16  to the rack  12  or placing the unit  16  on one of the trays  25  in the rack  12  (preferably the bottom-most mounting position or tray  25  of the rack  12 ). Power cords are connected to the air distribution unit  16  to provide power to the fans  28 ,  30 . A user presses the buttons  112 ,  114  as desired to select one or both of the fans  28 ,  30  to receive power and at which speed each fan  28 ,  30  should operate (if the fan  28  and/or the fan  30  is configured for multiple-speed operation). A front door  90  of the rack  12  may be closed to provide a bounded channel  92  between the door  90  and the rack-mounted equipment  14 . The door  90  may, however, not be closed or not be present. Preferably, the fans  28 ,  30  blow air at a sufficient speed such that the blown air remains substantially in an air curtain approximately the size of the channel  92 , with little loss of blown air to the environment around the rack  12 . 
   At stage  74 , the air distribution unit  16  is powered on to produce a flow of cool air into the rack  12 . The fans  28 ,  30  turn, thereby drawing cool air from between the raised floor  18  and the sub-floor  20  into the air distribution unit  16 , and more particularly into the internal regions  50 ,  52  of the fans  28 ,  30 . The cool air is forced by the fans  28 ,  30  from the internal regions  50 ,  52  into the chambers  31 ,  33 . The cool air is pushed from the closed chambers  31 ,  33  out of the unit  16  through the exhaust port  35  upward, away from the bottom  26  through and away from the top  24 . The expelled cool air is blown up the channel  92  along fronts of the rack-mounted components. 
   At stage  76 , the cool air in the channel  92  is drawn through the rack-mounted components  14 . Fans at the rears of the components blow air from the components  14  out the vented back  13  of the rack  12 . This draws the cool air from the channel  92  into and through the components  14 , cooling the components  14 , and in particular, transistors of the components  14 . 
   Other embodiments are within the scope and spirit of the appended claims. For example, only one fan, or more than two fans, may be used in the unit  16 . A single power source can be coupled to the unit  16 . Air could be forced upward at the backs of the equipment  14 . Also, the unit  16  may pump air of varying temperatures, including hot air. The distribution unit  16  may be configured to distribute various types of gases in addition to air, with changes to the materials noted above being made as appropriate. Further, a controller can be provided in the distribution unit  16  to regulate fan speed. The controller can be coupled to temperature and/or power monitors that provide information regarding temperature and power consumption, respectively, of the rack-mounted components  14 . In response to the monitored temperature and/or power consumption, the controller could control the speed of the fans  28 ,  30  to help compensate for temperature and/or power consumption variations to thereby help maintain the temperature of the components within a desired temperature range. Also, a wire-management device, such as a bracket, may be provided below the unit  16 , e.g., to reduce or limit spring forces produced by bending wires to fit in the rack  12  beneath the unit  16 . Thus, any such spring forces will not force the unit  16  undesirably, e.g., out of the rack  12  if there is no front door on the rack  12 .