Abstract:
An improved air-cooling system for high performance, high density electronic equipment comprises, in one embodiment, a single fan having a radial impeller, a baffle having an inlet portion to efficiently direct air into the fan intake, and a two-tiered outlet plenum to direct one airflow specifically at the highest heat-generating components and another airflow at all components. The air-cooling system is designed to provide maximum cooling for a low-height, high heat-generating electronics module such as a server. By using only a single fan that is matched to the low resistance airflow characteristics of the baffle, the air-cooling system offers significant advantages over multi-fan systems. Also described are a computer server and methods of making heat-dissipation equipment.

Description:
DIVISIONAL APPLICATION  
       [0001]     The present application is a divisional of application U.S. Ser. No. 09/896,869, filed on Jun. 29, 2001, which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD  
       [0002]     The subject matter relates generally to heat dissipation in electronic apparatus. More particularly, the subject matter relates to an improved air-cooling system for high density electronic equipment.  
       BACKGROUND INFORMATION  
       [0003]     Computer networks, such as the Internet, utilize high performance computer systems called “servers”. Servers typically have high performance processors and contain hardware and software capable of handling large amounts of data. Servers provide a large number of computer users with access to large stores of information. For example, servers are used to host web sites that can be accessed by many computers via the Internet.  
         [0004]     One or more server components are often housed within a server housing or “server rack”. Server racks are typically box-like structures or cabinets that contain a number of removable electronic modules or electronic trays (“e-trays”). Each e-tray can be a different server, or each e-tray can hold one or more components of a server. Server components can include electronic modules, for example, for processors, disk drives (such as floppy disk drives, hard drives, compact disk (CD) drives, and digital video disk (DVD) drives), random access memory (RAM), network interfaces and controllers, SCSI (small computer systems interface) bus controllers, video controllers, parallel and serial ports, power supplies, and so forth.  
         [0005]     There is an ever increasing demand by computer users for higher performance levels in computer equipment, such as servers. Because such equipment operates at higher and higher power levels, there is, as a direct consequence, an ever accelerating requirement to dissipate the thermal energy or heat produced by the equipment.  
         [0006]     For example, a server having dual high-performance processors, such as processors from the Intel® 64-bit Itanium™ family of processors (available from Intel Corporation, Santa Clara, Calif., U.S.A.), can produce a significant amount of heat, which can be in the order of several hundred watts of heat. To compound the problem, when a server at this performance level is packaged in an industry-standard “1U” height server (i.e. only 1.75 inches (4.445 cm) in height), heat dissipation can become a significant concern. If the heat is not adequately dissipated, the server equipment could be damaged, or the processors could be automatically throttled down to operate at a slower speed than their nominal rating.  
         [0007]     Many air-cooled systems have been used to cool electronics equipment, including computer equipment, in the past. In the past, relatively high performance electronic equipment generally required larger, more complex, and more powerful cooling solutions, as well as a corresponding increase in the size of the equipment cabinet or other type of equipment housing.  
         [0008]     For example, high performance computer equipment required an increase in the cabinet height to accommodate axial fans having larger propellers, as well as a greater number of axial fans per chassis. It is not unusual to see a half-dozen or more axial-type fans deployed on a single high performance chassis.  
         [0009]     These fans, and their associated airflow ducting, can consume an enormous amount of real estate on the chassis. They also contribute substantially to the cost, complexity, size, and height of the computer system, not to mention the additional noise that they produce due to the fact they typically run at high RPM, e.g. exceeding 10,000 RPM.  
         [0010]     Floor space for server racks is expensive, and it is desirable to pack as much computer performance into as small a space as possible. However, for the reasons set forth above, this can create significant heat dissipation problems.  
         [0011]     For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a significant need in the art for improved air-cooling systems for high performance electronic equipment that do not suffer the disadvantages of the prior art air-cooling systems, and for associated methods of making heat dissipation apparatus for high performance, high density electronic equipment. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a perspective view of an air-cooled electronics tray, in accordance with one embodiment of the subject matter;  
         [0013]      FIG. 2  is a top view of the air-cooled electronics tray illustrated in  FIG. 1 ;  
         [0014]      FIG. 3  is a cross-sectional view, taken along dashed line  30  of  FIG. 2 , of the air-cooled electronics tray illustrated in  FIG. 2 ;  
         [0015]      FIG. 4  is a cross-sectional view, taken along dashed line  40  of  FIG. 2 , of the air-cooled electronics tray illustrated in  FIG. 2 ;  
         [0016]      FIG. 5  is an exploded perspective view of the baffle and radial fan illustrated in  FIG. 2 ;  
         [0017]      FIG. 6  is a more detailed wireframe perspective view of the baffle members and the radial fan illustrated in  FIG. 5 ;  
         [0018]      FIG. 7  is a simplified perspective view of the air-cooled electronics tray illustrated in  FIG. 1 , showing the outlet portion of the baffle as viewed from the exit sides of the exit plenums;  
         [0019]      FIG. 8  is a rear perspective view of a baffle member shown in  FIG. 5 ;  
         [0020]      FIG. 9  is a top view of an air-cooled electronics tray having a different baffle, in accordance with another embodiment of the subject matter;  
         [0021]      FIG. 10  is a perspective view of the inlet portion of the baffle of the air-cooled electronics tray illustrated in  FIG. 9 ;  
         [0022]      FIG. 11  is a cross-sectional view, taken along dashed line  70  of  FIG. 10 , of the baffle illustrated in  FIG. 10 ; and  
         [0023]      FIG. 12  is a flow diagram illustrating a method of making heat dissipation apparatus for cooling an electronic assembly or other type of electronic chassis, in accordance with one embodiment of the subject matter. 
     
    
     DETAILED DESCRIPTION  
       [0024]     In the following detailed description of embodiments of the inventive subject matter, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific preferred embodiments in which the inventive subject matter may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the inventive subject matter, and it is to be understood that other embodiments may be utilized and that mechanical, compositional, structural, electrical, and procedural changes may be made without departing from the spirit and scope of the inventive subject matter. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the inventive subject matter is defined only by the appended claims.  
         [0025]     The subject matter provides a solution to the need to efficiently and quietly dissipate heat that is generated by high performance electronic equipment, and to do so in a manner that is relatively simple and inexpensive, and that does not increase chassis height or consume an undue amount of chassis real estate. Various embodiments are illustrated and described herein.  
         [0026]      FIG. 1  is a perspective view of an air-cooled electronics tray  1 , in accordance with one embodiment of the subject matter. Electronics tray (“e-tray”)  1  comprises a chassis that includes side panels  2  and  3 , front panel  4 , rear panel  5 , top panel  26  ( FIG. 3 ), and bottom panel  28  ( FIG. 3 ). In one embodiment, e-tray is approximately 1.75″ (4.445 cm) high, 17″ (43 cm) wide, and 24″ (61 cm) deep. A 1U-type chassis is a standard 1.75″ (4.445 cm) in height.  
         [0027]     E-tray  1  includes electronic apparatus in the form of electronic components, such as hard drive  7 , memory boards  8 , printed circuit board (PCB)  13 , and mezzanine board  14 . PCB  13  and mezzanine board  14  can include any number of electronic devices, including integrated circuits (IC&#39;s) and discrete devices. The IC&#39;s can include memory chips, chipsets, and one or more processor chips.  
         [0028]     In one embodiment, e-tray  1  comprises a pair of high performance 64-bit processors from the Intel® Itanium™ family of processors. These processors typically can operate at 1 Gigahertz clock speeds or higher. However, any type of high performance processor(s) could be used on e-tray  1 . Further, more than two or fewer than two processors could be used. As used herein, “processor” means any type of computational circuit, such as but not limited to a microprocessor, a microcontroller, a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a graphics processor, a digital signal processor, a communications processor, an application specific integrated circuit (ASIC), or any other type of processor or processing circuit.  
         [0029]     At least one set of heat sink fins  12  or other type of thermal interface arrangement, such as a heat pipe or heat spreader, is provided to conduct heat from devices that produce high levels of heat. Fins  12  conduct heat directly from the heat-generating devices to ambient air surrounding the devices. However, unless the chassis includes a mechanism for ridding itself of this increase in ambient heat, heat will build up to an undesirable level within the chassis, impacting the performance and life of electronic components on the chassis.  
         [0030]     Thus e-tray  1  comprises heat-dissipation apparatus. In one embodiment, the heat-dissipation apparatus comprises a fan indicated generally by reference number  11 , and an arrangement of baffles. Fan  11  includes a motor housing  18  ( FIG. 3 ) and a radial impeller  17 . Radial impeller  17  can be of the “squirrel cage” variety, and its individual vanes or blades can be either forward-curved or reverse-curved relative to the direction of spin. Radial impeller  17  is coupled to an inner wall  16  that, in turn, is coupled to fan motor shaft  19  ( FIG. 3 ).  
         [0031]     In one embodiment, fan  11  is a high-output radial impeller fan producing approximately 70 cubic feet (6.5 cubic meters) per minute. Radial fans generally run at much lower RPM (e.g. only 2800 RPM) than axial fans (typically greater than 10,000 RPM). This also significantly increases the lifespan of a radial fan over an axial fan running at much higher RPM. However, the subject matter is not to be construed as limited to the use of a radial impeller fan, and any other type of fan that can generate comparable airflow within the geometrical constraints of the chassis can be used.  
         [0032]     Fan  11  draws in outside air through a grill  6  in front panel  4 . Grill  6  can serve as an electromagnetic interference (EMI) grid. Alternatively, a separate EMI grid (not shown) can be employed in conjunction with grill  6 .  
         [0033]     A baffle, indicated generally by reference number  100 , directs air into fan  11  and from there out to the electronic components on PCB  13  and on mezzanine  14  that require cooling. As seen better in  FIG. 2 , baffle  100  comprises an inlet portion, generally indicated by reference number  10 , and an outlet portion, generally indicated by reference number  20 . Although baffle  100  is described as comprising an inlet portion  10  and an outlet portion, baffle  100  can be implemented in any appropriate number of physical elements, including separate inlet and outlet baffles, a single integrated baffle structure having inlet and outlet portions, and so forth. Baffle  100  can be made of any suitable material, such as molded plastic, fiberglass, or metal.  
         [0034]     Referring once again to  FIG. 1 , fan  11  pumps air into outlet portion  20 , indicated generally by reference number  20 . Outlet portion  20  comprises two exit plenums  21  and  22 . Exit plenums  21  and  22  are formed, in one embodiment, such that their cross-sectional areas increase with increasing distance from fan  11 , in a shape that is somewhat analogous to a nautilus shell. This shape minimizes back pressure and turbulence within exit plenums  21  and  22 , enabling them to conduct air more efficiently.  
         [0035]     In the embodiment shown in  FIG. 1 , a first portion of the air being pumped by fan  11  goes into exit plenum  21 , and a second portion of the air goes into exit plenum  22 . This is seen more clearly in  FIG. 3  to be discussed below.  
         [0036]     Continuing with  FIG. 1 , the portion of the air going through exit plenum  21  emanates from its air outlet in the direction indicated by arrows  23  and flows through heat sink fins  12  of the processor packages ( 33 - 34 ,  FIG. 5 ), carrying away heated ambient air and exiting the chassis through holes in rear panel  5  in the direction indicated by arrows  25 . The air leaving exit plenum  21  is thus directed at chassis components that are generating a relatively large amount of heat.  
         [0037]     Similarly, the portion of the air going through exit plenum  22  emanates from its air outlet in the direction indicated by arrows  24  and flows over memory boards  8  and over other heat-generating components on mezzanine  14  and on PCB  13 , carrying away heated ambient air and exiting the chassis through holes in rear panel  5  in the direction indicated by arrows  25 .  
         [0038]     Baffle  100  and fan  11  are individually available from Torrington Research Company, Torrington, Conn., U.S.A., whose URL is WWW.TRC1.com.  
         [0039]      FIG. 2  is a top view of the air-cooled electronics tray  1  illustrated in  FIG. 1 . As mentioned earlier, baffle  100  comprises an inlet portion  10  and an outlet portion  20 . If one follows a geometrical line (such as dashed line  30 ) from grill  6  inward to PCB  13  and mezzanine  14 , it is seen that inlet portion  10  and outlet portion  20  overlap to a certain extent, due to the particular geometry of inlet portion  10  and outlet portion  20 . However, in other embodiments of a baffle, there may be no overlap, depending upon the particular geometry of the baffle.  
         [0040]     The shape of exit plenums  21  and  22  of outlet portion  20  can be seen in  FIG. 2 . Exit plenum  21  directs air through its end section  29  at heat sink fins  12  of the processors (not shown, but positioned beneath heat sink fins  12 ). Thus exit plenum  21  directs approximately half of the output of fan  11  at chassis components that are generating a significant amount of heat.  
         [0041]     Exit plenum  22  directs air through an end section having a width that is equivalent to the width of the chassis minus the width of the end section  29  of exit plenum  21 . Exit plenum  22  directs approximately half of the output of fan  11  at chassis components that are positioned between exit plenum  22  and rear panel  5 . This includes, for example, memory boards  8  and mezzanine board  14 , as well as to some extent the chassis components that are positioned between exit plenum  21  and rear panel  5 , because the air exiting from exit plenums  21  and  22  mixes together before it exits through vent holes in rear panel  5 .  
         [0042]      FIG. 3  is a cross-sectional view, taken along dashed line  30  of  FIG. 2 , of the air-cooled electronics tray  1  illustrated in  FIG. 2 . Dashed line  30  passes through the center of fan motor shaft  19  and the motor housing  18  of fan  11 . One end of fan motor shaft  19  is coupled to a motor (not shown for simplicity of illustration) within fan motor housing  18 , and the other end of fan motor shaft  19  is coupled to inner wall  16  of radial impeller. Inner wall  16  is, in turn, coupled to a base member  31 , to which a plurality of vanes or blades  32  are attached to form radial impeller  17 .  
         [0043]     Seen in  FIG. 3  are steps  41  and  42  of inlet portion  10  of baffle  100 . A first portion of the incoming airflow, represented by arrows  15 , passes through grill  6  straight into opening  45  ( FIG. 1 ) of fan  11  ( FIG. 1 ), while other portions of the incoming airflow move through grill  6  and then upward over one or both steps  41  and  42  before entering opening  45 . A portion  38  of baffle  100  can make contact with top panel  26  to prevent air from recirculating from the exit of baffle  100  back to opening  45 .  
         [0044]     Also seen in  FIG. 3  is exit plenum  21 . As explained above, and seen more clearly in  FIG. 3 , exit plenum  21  receives air from the upper portion of radial impeller  17 . Exit plenum  22  is not viewable in  FIG. 3 ; however, a static chamber  35  can be seen (also seen in  FIGS. 5, 6 , and  8 ). Static chamber  35  does not conduct air; however, it can be used, for example, to house cables or other chassis components that do not generate significant amounts of heat.  
         [0045]     Heat sink fin  12  is affixed to a processor package ( 34 ,  FIG. 7 ) situated on PCB  13 . Air exiting from both exit plenums  21  and  22  (seen in  FIG. 1 ) blows through the segment of PCB  13  to which the processor packages are mounted.  
         [0046]      FIG. 4  is a cross-sectional view, taken along dashed line  40  of  FIG. 2 , of the air-cooled electronics tray  1  illustrated in  FIG. 2 . Dashed line  40  passes through the center of fan motor shaft  19  and the motor housing  18  of fan  11 .  
         [0047]     Also seen in  FIG. 4  are steps  41  and  42  of inlet portion MMM of baffle  100 .  
         [0048]     In addition, the upper ends of heat sink fins  12  can be seen.  
         [0049]      FIG. 5  is an exploded perspective view of the baffle  100  and radial fan  17  illustrated in  FIG. 2 . Baffle  100  can be formed in a dual-element configuration that includes a first baffle member  51  and a second baffle member  52 . Baffle members  51  and  52 , when assembled in an orientation along dashed line  103 , together form baffle  100 , and they surround fan  11 .  
         [0050]     Baffle member  51  includes inlet step  41 , opening  45 , and exit plenum  21 . Baffle member  52  includes inlet step  42 , opening  46 , and exit plenum  22 . Openings  45  and  46  can have the same diameters. Baffle member  52  also includes a static chamber segment  27  that has several static chambers  35 . Static chambers  35  do not conduct airflow. Static chambers  35  prevent recirculation of air back to the inlet of fan  11 , and they can be used for storing miscellaneous chassis components.  
         [0051]      FIG. 6  is a more detailed wireframe perspective view of the baffle members  51  and  52  and of radial fan  11  illustrated in  FIG. 5 . The exterior “skins” of exit plenum  21  of baffle member  51  and of static chamber segment  27  of baffle member  52  have been removed to show the interior detail. Chamber  36  within baffle member  52  does not conduct airflow and can be sealed. This area can serve as a support for exit plenum  21  of baffle member  51 , when baffle members  51  and  52  are assembled into baffle  100 .  
         [0052]      FIG. 7  is a simplified perspective view of the air-cooled electronics tray  1  illustrated in  FIG. 1 , showing the outlet portion of baffle  100  as viewed from the exit sides of exit plenums  21  and  22 .  
         [0053]     As described earlier, exit plenum  21  directs air through its end section at heat sink fins  12  of processor packages  33  and  34 . Exit plenum  22  directs air through an end section having a width that is equivalent to the width of the chassis minus the width of the end section of exit plenum  21 . Exit plenum  22  directs approximately half of the output of fan  11  at chassis components that are positioned anywhere between exit plenum  22  and the rear edge  9  of the chassis, because the air exiting from exit plenums  21  and  22  mixes together before it exits through vent holes in rear panel  5  ( FIG. 1 ).  
         [0054]      FIG. 8  is a rear perspective view of baffle member  52  shown in  FIG. 5 . This view is from essentially the same perspective as the exit plenum  22  is depicted in  FIG. 7 . Baffle member  52  includes an opening  37  in exit plenum  22 . Also seen in  FIG. 8  are several static chambers  35  of static chamber segment  27 .  
         [0055]      FIG. 9  is a top view of an air-cooled electronics tray  101  having a different baffle  60 , in accordance with another embodiment of the subject matter. In the embodiment shown in  FIG. 9 , all elements of the electronics tray  101  can be substantially similar to those depicted in  FIGS. 1 and 2  except for baffle  60 .  
         [0056]     Baffle  60  directs air, represented by arrows  71 , into opening  68 , through fan  11 , and out an exit plenum in the direction indicated by arrows  72  towards chassis components requiring cooling. Baffle  60  will now be described in greater detail regarding  FIG. 10  immediately below.  
         [0057]      FIG. 10  is a perspective view of the inlet portion of baffle  60  of the air-cooled electronics tray  101  illustrated in  FIG. 9 . Baffle  60  comprises a pair of substantially vertical sides  61  and  62 , and it further comprises a bottom in the form of a raised platform  67 . A back wall  63  extends along the back of platform  67 . Side  61 , side  62 , back wall  63 , platform  67 , and the top panel  26  ( FIG. 3 ) form a box-like intake plenum that bounds the air that is drawn in by fan  11 . Sides  61  and  62 , back wall  63 , and top panel  26  may be planar. Airflow  72  is prevented from being recirculated back to fan  11  by this structure.  
         [0058]     Platform  67  comprises a large opening  68  juxtaposed to the intake of fan  11 . Opening  68  has a rounded lip  69  in one embodiment.  
         [0059]     The approach area  64  to baffle  60  comprises an angled ramp  65 . Ramp  65  can have a step  66  around its outer periphery. Ramp  65  is formed in an arc about one side of opening  68 . Ramp  65  decreases the cross-sectional area of the intake plenum in relation to the distance from the opening  68 .  
         [0060]     In operation, air is drawn into the approach area  64  of baffle  60 , and it flows in the direction of arrows  71  over step  66 , up ramp  66  onto platform  67 , through opening  68 , and into the intake of fan  11 .  
         [0061]     As seen in  FIG. 1 , the periphery of grill  6  in front panel  4  ( FIG. 1 ) bounds a relatively small cross-sectional area through which all of the intake air must pass. To minimize the amount of work that fan  11  must perform, it is desirable to minimize the length of the region of narrowing cross-section that runs from grill  6  to platform  67 . By providing an angled ramp  65 , the region of narrowing cross-section is kept to a minimum, and intake air is efficiently funneled into the intake of fan  11 .  
         [0062]     Employing a relatively short region of small cross-section improves air intake performance over a non-ramped inlet to the baffle, in part because it offers less overall resistance to incoming airflow, and in part because back-pressure, vortices, eddys, and other undesirable airflow disturbances are minimized through the use of a short angled ramp  65 , as opposed to a long, non-angled intake region or a rectangular intake region.  
         [0063]     In addition, an angled ramp  65  also enables EMI containment in the form of a grill or mesh to be positioned in the area of greatest cross-sectional area, not in a region of small cross-sectional area. Sufficient EMI containment can thus be provided while concurrently minimizing its effect on air flowing into the intake of fan  11 .  
         [0064]     Baffle  60  can be made of any suitable material, such as molded plastic, fiberglass, or metal.  
         [0065]      FIG. 11  is a cross-sectional view, taken along dashed line  70  of  FIG. 10 , of the baffle  60  illustrated in  FIG. 10 . The profile of angled ramp  65  can clearly be seen in  FIG. 11 , as can the lip  69  around opening  68  ( FIG. 10 ) of platform  67  of baffle  60 . Radial impeller  17  comprises a plurality of blades or vanes  32  that are coupled to base member  31  of radial impeller  17 .  
         [0066]      FIG. 12  is a flow diagram illustrating a method of making heat dissipation apparatus for cooling an electronic assembly or other type of electronic chassis, in accordance with one embodiment of the subject matter. The method begins at  200 .  
         [0067]     In  202 , a chassis having a plurality of heat-generating components (e.g. IC&#39;s and/or discrete devices such as resistors, capacitors, and inductors) is provided. In one embodiment, a computer server is provided. In another embodiment, a 1U e-tray is provided that can be any type of electronic equipment, including a computer component. The chassis can be relatively low in height; e.g. in one embodiment the width-to-height ratio of the chassis is approximately 9 or greater. However, embodiments of the subject matter also perform well for width-to-height ratios that are less than 9, i.e. for chassis that are relatively high such as, without limitation, 4U or 7U chassis. The geometry of the fan and of the inlet and outlet portions of the baffle can be appropriately adjusted.  
         [0068]     While the embodiment shown in the figures is a server that is positioned in a horizontal rack, the subject matter can also be used in vertical-type racks. For example, the exit plenums of the outlet portion of the baffle could be arranged side-by-side vertically rather than double-tiered horizontally.  
         [0069]     In  204 , a fan is mounted on the chassis. The fan can be of any type, such as a radial impeller fan, an axial impeller fan, or any other suitable type. In one embodiment, a single radial impeller fan is used to quietly, efficiently, cost-effectively, and reliably cool an entire server chassis or e-tray of the 1U form factor. However, in other embodiments, more than one fan can be used.  
         [0070]     In  206 , a baffle is mounted on the chassis. In one embodiment, the baffle is constructed as one unit encompassing both an inlet baffle and an outlet baffle. In such an embodiment, the baffle has an inlet coupled to the fan and an outlet that is directed at the electronic components of the chassis. In another embodiment, as discussed earlier, separate inlet and outlet baffles can be utilized, and in such an embodiment the inlet baffle is coupled to the fan and directs air into the fan intake, and the outlet baffle directs air at the electronic components of the chassis.  
         [0071]     Still referring to  206 , the outlet can include a first portion that is directed to electronic components that are generating a relatively large amount of heat, and a second portion that is directed at an area of the chassis that does not necessarily include such high heat generating components. Various alternatives are possible. For example, in one embodiment, the second portion can direct air towards electronic components over the entire chassis, or it could direct air only towards all electronic components except for those covered by the first portion, or it could direct air at a subset of the remaining electronic components, leaving a portion of the electronic components (e.g. low heat generating components) that are not covered by either the first or second portions. In  208 , the method ends.  
         [0072]     The operations described above with respect to the method illustrated in  FIG. 12  can be performed in a different order from that described herein. Also, it should be understood that although an “End” block is shown for the method, it may be continuously performed.  
         [0073]     The subject matter provides for heat-dissipation apparatus for high density electronic equipment, which in one embodiment comprises a relatively low-height server, such as a 1U server. In one embodiment, the ratio of width to height of the server is approximately 9 or greater; however, other width-to-height ratios are possible.  
         [0074]     In one embodiment, a single fan, such as a radial impeller fan, is coupled to an inlet baffle, or to an inlet portion of a baffle, that provides efficient air flow into the fan, and to an outlet baffle, or to an outlet portion of a baffle, that directs a relatively high volume of air over heat-generating components on a chassis of the electronic equipment. This air-cooling arrangement is highly efficient and is capable of cooling a 1U server housing a pair of high-performance 64-bit processors, such as processors from Intel&#39;s Itanium™ family of processors.  
         [0075]     Other embodiments described herein include an electronic apparatus that includes a heat-dissipation apparatus essentially as described above; an inlet baffle having a cross-sectional area that increases with the distance from a fan inlet to which it is coupled and further having a ramp to the fan inlet; and methods of making an air-cooled chassis.  
         [0076]     Various embodiments of the subject matter enable high density electronic apparatus to operate reliably and quietly within its thermal performance specifications.  
         [0077]     As shown herein, the subject matter can be implemented in a number of different embodiments. Other embodiments will be readily apparent to those of ordinary skill in the art. The elements, materials, geometries, dimensions, and sequence of operations can all be varied to suit the particular requirements of the electronic apparatus with which various implementations of the subject matter may be used.  
         [0078]     The subject matter should not be construed as restricted to servers or 1U servers, and it may find application in any type of electronic assembly. For example, it can be used for telecommunications equipment, power industry equipment, industrial equipment, radio and television broadcasting equipment, aerospace and military equipment, maritime equipment, automotive equipment, and personal entertainment equipment (e.g., televisions, radios, stereos, tape and compact disc players, video cassette recorders, MP3 (Motion Picture Experts Group, Audio Layer 3) players, etc.), and the like. Thus, as used herein, the terms “server” or “electronic assembly” are intended to mean any type of electronic assembly structure.  
         [0079]     The terms “top”, “bottom”, “front”, and “back” are to be understood as relative terms, and it should be understood that the scope of the subject matter includes corresponding elements in structures that may be inverted, turned end-for-end, mirrored, or rotated through 90 degrees or through any other angle, relative to those shown in the figures and described herein.  
         [0080]     The above-described choice of materials, geometry, structure, and assembly operations can all be varied by one of ordinary skill in the art to optimize heat dissipation in electronic assemblies. The particular implementation of the subject matter is very flexible in terms of the orientation, size, number, and composition of its constituent elements. Various embodiments of the subject matter can be implemented using any one or more of various geometrical and functional arrangements of radial or axial fans, inlet and/or outlet baffles or ducts, and combinations thereof, to achieve the advantages of the subject matter.  
         [0081]     The figures are merely representational and are not drawn to scale. Certain proportions thereof may be exaggerated, while others may be minimized.  FIGS. 1-8  are intended to illustrate various implementations of the subject matter that can be understood and appropriately carried out by those of ordinary skill in the art.  
         [0082]     Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the subject matter. Therefore, it is manifestly intended that embodiments of the subject matter be limited only by the claims and the equivalents thereof.