Abstract:
A reconfigurable airflow director for modular blade chassis. The airflow director includes multiple duct channels having adjustable inlets and/or outlets. The airflow director may be reconfigured to adjust the amount of airflow across selected blades and selected zones on an individual blade. In one embodiment, snap-in airflow blockers are employed to block all or a portion of selected inlets or outlets to adjust the airflow through corresponding duct channels. In one embodiment, adjustable inlet vanes are employed to increase or decrease the size of adjacent inlets. In one embodiment, the airflow director is formed from multiple airflow director modules, each including an outer shell having multiple ribs extending therefrom to form multiple airflow channels, wherein the airflow director modules are stacked together to form a plurality of duct channels. Modular fan assemblies including multiple hot-swappable fans are employed to push and/or draw airflow through the duct channels of the airflow director.

Description:
FIELD OF THE INVENTION 
   The field of invention relates generally to computer and telecommunications equipment, and, more specifically but not exclusively relates to a reconfigurable airflow director for computer and telecommunication equipment chassis. 
   BACKGROUND INFORMATION 
   The Advanced Telecommunications Architecture (ATCA) (also referred to as Advanced TCA) standard defines an open switch fabric based platform delivering an industry standard high performance, fault tolerant, and scalable solution for next generation telecommunications and data center equipment. The development of the ATCA standard is being carried out within the PCI Industrial Computer Manufacturers Group (PICMG). 
   The Advanced TCA 3.0 base specification defines the physical and electrical characteristics of an off-the-shelf, modular chassis based on switch fabric connections between hot-swappable blades. This specification defines the frame (rack) and shelf (chassis) form factors, core backplane fabric connectivity, power, cooling, management interfaces, and the electromechanical specification of the ATCA-compliant boards. The electromechanical specification is based on the existing IEC60297 EuroCard form factor, and enables equipment from different vendors to be incorporated in a modular fashion and be guaranteed to operate. The ATCA 3.0 base specification also defines a power budget of 200 Watts (W) per board, enabling high performance servers with multi-processor architectures and multi gigabytes of on-board memory. 
   Although the ATCA standard is a step in the right direction with respect to providing standardized telecom and computer component interfaces and interoperability, several of its design aspects are limiting. Notably, the 200 W power dissipation per board slot places a restriction on how much heat can be generated by a board, while not defining the location of the heat sources. (It is noted the 200 W limit applies to boards occupying a single slot. Higher power dissipations are allowed for boards occupying multiple slots, e.g., a front board occupying two slots is limited to 400 W). In order to meet ever increasing bandwidth demand, equipment capabilities need to increase, requiring faster processors, among other board component improvements. When considering identical semiconductor fabrication processes, there is a direct relationship between speed and power consumption—the faster the processor speed, the greater the power consumption of the processor, and thus the greater the amount of heat that must be dissipated by an ATCA board hosting the processor. In view of the rigid board and shelf form factors defined by the ATCA base specification, this leads to problems in achieving sufficient cooling for high-power components such as processors, since the majority of the 200 W will be consumed by such components. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified: 
       FIG. 1  is a schematic diagram of an exemplary airflow pattern defined by the ATCA (Advanced Telecommunication Architecture) standard for cooling ATCA boards; 
       FIG. 2  is an isometric view of a reconfigurable airflow director that may be adjusted to selectively vary airflow across ATCA boards, according to one embodiment of the invention; 
       FIG. 3   a  is a front isometric view of an airflow director module used to form the airflow director of  FIG. 2 ; 
       FIG. 3   b  is a rear isometric view of the airflow director module of  FIG. 3   b;    
       FIG. 4   a  is an isometric view of a pair of airflow director modules; 
       FIG. 4   b  is a close-up isometric view illustrating details of a coupling mechanism used to couple a airflow director modules together; 
       FIGS. 5   a  and  5   b  are isometric views of an airflow director module and a pair of snap-in blockers that are used to block selected portions of an air director inlets; 
       FIGS. 6   a  and  6   b  are front isometric views of an airflow director module including adjustable inlet vanes that may be repositioned to vary airflow across selected portions of an ATCA board; 
       FIG. 6   c  is a rear isometric view of the airflow director module of  FIGS. 6   a  and  6   b;    
       FIGS. 7   a  and  7   b  are isometric views of selected portions of an ATCA chassis in which the airflow director of  FIG. 1  may be implemented, wherein the embodiment of  FIG. 7   a  shows a configuration including a first set of hot-swappable fans used to draw air through the airflow director and the embodiment of  FIG. 7   b  further includes a second set of hot-swappable fans used to push air through the airflow director; 
       FIG. 7   c  is an isometric view of an ATCA chassis corresponding to the embodiment of  FIG. 7   b.    
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Embodiments of apparatus and methods for enhancing cooling in computer and telecommunication equipment chassis are described herein. In the following description, numerous specific details are set forth, such as implementations corresponding to the ATCA standard, to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention. 
   Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
   In the following paragraphs, exemplary embodiments of the invention are described within a use context targeted to ATCA equipment installations. However, this does not limit the use of the principles and teachings disclosed herein to ATCA equipment. Rather, the following embodiments are merely illustrative of one possible type of installation. In general, the principles and teachings are applicable to various types of modular electronic equipment, including, but not limited to, telecommunications equipment and computer equipment. 
   The majority of equipment installed in central office and data centers today is air cooled due to simplicity, relatively low cost, ease of implementation, and reliability. This trend is likely to continue into the future for the same reasons. Accordingly, the thermal guidelines defined in the ATCA specification apply to air cooling; other cooling methods are permissible, but are not covered in the specification. In general, Boards, Shelves, and Frames may be either cooled by natural convection, without the assistance of fans or blowers, or cooled by forced convection with the assistance of fans or blowers. The choice is left to the end-user requirements. 
   An airflow path used as an example in the ACTA PICMG 3.0 Short Form Specification (January, 2003) is shown in  FIG. 1 . Air enters a Shelf  100  at in air inlet  102  at the lower front into a bottom plenum  104  and turns 90 degrees upward. Airflow across the bottom edge of a Front Board  106  and a rear transition module (RTM)  108  is evenly distributed. As the air passes across the hot components on Front Board  106  and RTM  108 , heat is carried away by forced convection. The air exits the subrack at the top, is drawn into an upper plenum  110 , turns 90 degrees, and is exhausted out the rear of Shelf  100  by fans  112 . In addition to the illustrated configuration, other airflow paths and cooling methods are allowed under the ACTA standard. 
   The standard cooling configuration shown in  FIG. 1  has several drawbacks. Notably, it assumes that cooling requirements for all boards are substantially equal, wherein the airflows across all boards are approximately equal. Furthermore, it does not consider “hot spots” on individual boards, but rather again using an average airflow approach. In contrast, the power consumption (and thus heat generation) within a typical ATCA chassis is uneven, with certain types of boards producing more heat that other types of boards. Furthermore, in many boards only a few components, such as processors, produce the majority of heat for the board. These components may become overheated if not provided with adequate airflow. 
   In accordance with aspects of the embodiments described herein, enhanced cooling is facilitated through use of a reconfigurable airflow director that can be selectively configured to supply higher airflow to high-power components and boards, while providing lower airflow to low-power components and boards. In view of the modular design concept advanced by the ACTA and other standards, the airflow director may be included as part of a modular ducting apparatus that may be used in a standard ACTA rack. 
   An overall view of a reconfigurable airflow director  200 , according to one embodiment, is shown in  FIG. 2 . The airflow director comprises an assembly formed by coupling a plurality of airflow director modules  202  together, further details of which are shown in  FIGS. 3   a - b  and  4   a - b . Each airflow director module includes multiple airflow channels via which air is redirected from an inlet side to an outlet side of the airflow director. In the illustrated embodiment, each of airflow director modules  202  includes three airflow channels  204 ,  206 , and  208 . However, this is merely exemplary, as other numbers of airflow channels may be employed. Upon being coupled together, each airflow channel becomes a duct channel. Thus, airflow director  202  contains a multitude of duct channels  210  that are used to selectively direct air more effectively to various areas of an ATCA chassis in which the air director is installed. The various duct channels can be selectively blocked (either partially or completely) to reduce airflow across components receiving airflow from those duct channels. This enables airflow across selected boards, and even across zones on selected boards to be varied to more efficiently use the airflow produced by fans that are used to draw and/or push air through the various duct channels of the airflow director. 
   In one embodiment, there is a set of duct channels for each respective slot in the chassis in which the airflow director is installed. For example, one ATCA chassis form factor provides 14 slots for up to 14 single-width ATCA boards. Accordingly, the embodiment of airflow director  202  in  FIG. 2  includes 14 sets of duct channels  210 , formed by coupling together 14 airflow director modules  202 . 
   Details of one embodiment of airflow director module  202  are shown in  FIGS. 3   a - b ,  4   a - b , and  5   a - b . The airflow director module comprises an outer shell  300  having a plurality of internal ribs that are used to form the airflow channels. In one embodiment, the outer shell is substantially rectangular in configuration. In the embodiment of  FIG. 3   a , the internal ribs include ribs  302 ,  304 , and  306 . The ribs will generally have a curvilinear shape to redirect airflow received at inlets  308 ,  310 , and  312  and exiting at outlets  314 ,  316 , and  318 . 
   Details of a coupling mechanism used for coupling airflow director modules  202  together are shown in  FIGS. 4   a  and  4   b . Each airflow director module  202  includes four engagement tabs  400  that are configured to engage four mating tab recesses  402 . Each engagement tab  400  includes a protrusion  404  that engages a respective mating tab recess  402  upon coupling a pair of airflow director modules  202  together. 
   As discussed above, embodiments of airflow director  200  may provide a mechanism for selectively blocking all or a portion of selected duct channels. In one embodiment, airflow director  200  includes multiple slots  500  disposed in the various inlets and outlets of the duct channels, as shown in  FIGS. 5   a  and  5   b . The slots generally may be configured to server multiple purposes. In one respect, the slots provide a stiffening function, increasing the strength of the individual airflow director modules  202  and thus the assembled airflow director  200 . 
   In another respect, the slots on the outlet side of the airflow director may be configured to generate turbulence in the airflow exiting the slots, thus enhancing heat transfer via turbulent forced-convection airflow. In addition to the slots, other means may be used to generate turbulence in the airflow exiting the airflow director outlets. For example, bumps or the like may be formed in the sidewall of an airflow director module. 
   Another purpose of slots  500  is to provide an engagement means via which snap-in airflow blockers may be installed. For example,  FIGS. 5   a  and  5   b  respectively show exemplary snap-in airflow blockers  502  and  506  before and after installation in an airflow director module  202 . The snap-in airflow blocker  502  includes one or more engagement tabs  504  at each end of the airflow blocker that engage respective slots in the airflow director module using a snapping action. 
   Generally, the width of a snap-in airflow blocker may vary, depending on the portion of an inlet or outlet that the blocker is designed to block. For example, a snap-in blocker may be used to block a portion of an inlet or outlet spanning one or more slots. For example, snap-in blocker  502  is configured to block the entirety of inlet  310 , while single-slot snap-in block  506  is configured to block a single slot. In addition, the width and number of slots shown in the Figures herein are merely exemplary. In general, the slots may be evenly-spaced, or have variable spacing. Furthermore, all or a portion of a given inlet or outlet may include a single opening with no slots. 
   Depending on the particular cooling requirements for a system, various slots  500  may be selectively blocked using appropriately-sized snap-in airflow blockers. In general, snap-in airflow blockers will be used to block inlets when air is pushed into the air director inlets. When air is drawn into the inlets (e.g., using fans located at the top of a chassis), the snap-in airflow blockers may be installed so that selected portions of the inlets or outlets are blocked. 
   Under an alternative airflow-adjustment technique, one or more of the airflow director modules includes adjustable inlet vanes. For example, details of an airflow director module  202 A including adjustable inlet vanes  600  and  602 . Each inlet vane is pivotally coupled to a respective rib  604  and  606  via a pivot  608 . In one embodiment, a pair of opposing stub shafts are formed in an inlet vane to provide the pivot axes, where the opposing stub shafts engage mating recesses in the rib to which the inlet vane is pivotally coupled. In another embodiment, a shaft is inserted through holes formed in the inlet van and the rib. 
   In general, various schemes may be used to enable an inlet vane to be repositioned. In the illustrated embodiment of  FIGS. 6   a - c , multiple detents  610  are formed in outer shell  300 A. A mating protrusion is formed in one (as illustrated) or both (not shown) sides of each inlet vane. The protrusion, inlet vane, and pivot are configured to allow an inlet vane to be repositioned to engage a selected detent  610 . In general, an airflow director module that employs adjustable inlet vanes may or may not include slots that are analogous to slots  500  (which in this instance would be used for stiffening purposes). 
   As shown in  FIG. 6C , a cavity  612  is formed in the backside of outer shell  300 A, such that a rib  614  is formed between the back of outside shell  300 A and a shelf  616  formed in the front-side of the shell. It is noted that a similar configuration may be employed for airflow director module  202 . 
   In general, airflow director modules  202  and  202 A may be formed of a suitable plastic or metal. In one embodiment, a plastic airflow director module is formed using an injection molding process, as is known in the art. Other plastic molding techniques may also be employed, such as, but not limited to, vacuum forming and roto-molding. Metal airflow director modules may generally be formed using conventional metal forming techniques, such as casting and forging, for example. 
   Exemplary implementations of airflow director  200  for an ATCA chassis are shown in  FIGS. 7   a - c . For purposes of clarity, selected portions of the ATCA chassis has been removed n  FIGS. 7   a  and  7   b . A substantially complete chassis is shown in  FIG. 7   c.    
     FIG. 7   a  illustrates the airflow for an ATCA chassis configuration that includes a plurality of axial fans  700  located toward the outlet of a top plenum  702  (see  FIG. 7   c ). This configuration is referred to as a “draw-through” configuration, as air is drawn through the various duct channels of airflow director  200  by creating a slight vacuum on the outlet side of the airflow director. In one embodiment, axial fans  700  are part of a modular fan assembly that includes multiple “hot-swappable” fans, meaning a failed fan may be replaced without removing power to the other fans. 
   In  FIGS. 7   b  and  7   c , an additional set of axial fans  701  are located toward the lower front of an ATCA chassis  710  to push air into the inlet side of airflow director  200 . This configuration is referred to as a “push-through” configuration, as air is pushed into the inlet side of airflow director  200  by axial fans  701 . It is noted that a combination of a push-through and draw-through configuration exist when both axial fans  700  and  701  are installed. In one embodiment, axial fans  701  are part of a modular fan assembly that includes multiple hot-swappable fans. 
   In addition to the axial fans depicted in the figures herein, other types of fans may be used. For example, one or more centrifugal fans may employed in place of or in addition to axial-type fans. 
   The ATCA chassis  710  includes top and bottom slot guides  704  and  706  used to guide the installation of an ATCA front board  708 . In general, multiple ATCA front boards will be installed in a given ATCA chassis under a typical ATCA installation. For clarity, only a single ATCA front board is depicted in  FIGS. 7   a - c . Furthermore, the ATCA front boards will be coupled to a backplane, which is also not shown in  FIGS. 7   a - c  for clarity. Additionally, typically one or more RTMs (also not shown) will be coupled to the backplane. 
   As illustrated in  FIGS. 7   a  and  7   b , airflow channels  204  and  206  are used to direct airflow over the ATCA front boards, while airflow channels  208  are used to direct airflow over the RTMs. Accordingly, it may be desired to block all or a portion of an inlet  312  (see, e.g.,  FIG. 3   a ) for slots that do not employ an RTM when pushing air through the various inlets, such as illustrated by the push-through configurations of  FIGS. 7   b  and  7   c . For implementations in which air is drawn through the airflow director, such as illustrated by the draw-through configuration of  FIG. 7   a , all or a portion of an outlet  318  may be blocked for a slot without an RTM. Similarly, it may be advantageous to block all or a portion of inlets  308  and  310  for an empty front-board slot (i.e., an empty slot that is configured to receive an ATCA front board) for push-through configurations, while blocking all or a portion of outlets  314  and  316  for draw-through configurations. 
   Similar types of adjustments can be produced when using an airflow director that includes one or more of airflow director modules  202 A shown in  FIGS. 6   a - c . In this instance, the inlet vanes  600  and  602  may be adjusted to redirect the airflow in a desired manner. In general, the adjustment of the inlet vanes will be similar for both push-through and draw-through configurations. 
   In one embodiment, airflow director  200  comprises an assembly module that may be easily removed, readjusted, and re-installed in an ATCA chassis. For example, the airflow director may be installed in a shelf coupled to the lower portion of the ATCA chassis. Under one embodiment, a side panel  712  of ATCA chassis  710  is used to function as a cover plate for the first airflow director module  202  in the airflow director assembly, thereby forming duct channels in this first airflow director module. 
   In addition, one or more filter elements may be placed at the inlet and/or outlet sides of the airflow director. Such filter elements are not shown in the Figures herein for clarity. 
   In addition to the exemplary ATCA chassis implementations discussed above and illustrated in the Figures herein, the general principles and teachings of the foregoing embodiments may be implemented for various types of cooling systems that are designed to direct airflow over one or more circuit boards. A non-exhaustive list of exemplary implementations include computer servers (e.g., blade servers), medical equipment (e.g., ultrasound machines), and telecommunication equipment (e.g., switches, routers, etc.). 
   The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. 
   These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.