Patent Publication Number: US-2012039036-A1

Title: Thermal bus bar for a blade enclosure

Description:
BACKGROUND 
     Many datacenters are now populated with computer blades mounted in blade enclosures. A computer blade is defined as a device that accesses power and connections to other blades and devices through a shared infrastructure or enclosure. The computer blade may be rack mounted into the enclosure. A computer blade may also be defined as a device that provides power and connectivity to other blades and devices through the shared infrastructure or enclosure. A computer blade can fulfill a number of different functions. There are blade servers, Input/Output (I/O) blades, memory blades, power supply blades, I/O interconnect blades, and the like. As the computer blades have increased in power density, cooling the blades has become a challenge. 
     Blades are typically cooled by drawing ambient air through the blade enclosure to remove the heat generated by the components mounted on the blades. This solution requires the ambient air to be conditioned to a specific temperature and humidity. Without conditioning, the components may be subject to insufficient cooling, humidity damage, or contamination. Conditioning the air can use a significant portion of the energy required by the datacenter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is an isometric view of a blade enclosure  100  in an example embodiment of the invention. 
         FIG. 1B  is a cut-away side view of blade enclosure  100  in an example embodiment of the invention. 
         FIG. 2A  is an isometric view of cooling assembly  106  with the top cover of cooling base  120  removed, in an example embodiment of the invention. 
         FIG. 2B  is a top view of cooling assembly  106  with the top cover of cooling base  120  removed, in an example embodiment of the invention. 
         FIG. 3  is a diagram of the cooling pathways in cooling assembly  106  in one example embodiment of the invention. 
         FIG. 4A  is a diagram of the cooling pathways in cooling assembly  106  in another example embodiment of the invention. 
         FIG. 4B  is a diagram showing the temperature gradient of the TBB from  FIG. 4A  in an example embodiment of the invention. 
         FIG. 5  is an isometric view of a blade in an example embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1-5 , and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific examples described below, but only by the claims and their equivalents. 
       FIG. 1A  is an isometric view of a blade enclosure  100  in an example embodiment of the invention. Blade enclosure  100  comprises left and right side panels  102 , top panel  104 , and cooling assembly  106 . The front face of blade enclosure  100  has a first column of smaller openings or slots  112  in the center of the front face and a left and right column ( 108  and  110 ) of larger openings or slots on either side of the column of smaller openings or slots. Cooling assembly  106  is located in the bottom of blade enclosure  100  and has a thermal bus bar (TBB) extending up through the middle of blade enclosure (see  FIG. 2 ). In one example embodiment of the invention, the column of smaller slots  112  are configured to receive power supply blades and the two columns of larger slots are configured to receive a plurality of different types of computer blades. 
       FIG. 1A  shows the slots with a horizontal orientation, but in other example embodiments the slots may be oriented vertically.  FIG. 1A  shows the center column of smaller slots  112  configured to receive power supply blades, but in other example embodiments the power supply slots may be the same size as the blade slots, or may be distributed in the enclosure as a number of rows. In one example embodiment of the invention, blade enclosure is symmetrical and the back face of the blade enclosure is a mirror image of the front face (i.e. three columns of slots). In other example embodiments of the invention the slot configuration on the back face may be different than the slot configuration on the front face. 
       FIG. 1B  is a cut-away side view of blade enclosure  100  in an example embodiment of the invention. Blade enclosure  100  comprises top panel  104 , a plurality of slots on the front face  132 , a plurality of slots on the back face  130 , and cooling assembly  106 . Cooling assembly  106  comprises cooling base  120  and thermal bus bar (TBB)  122 . Cooling base is located in the bottom section of blade enclosure  100 . TBB  122  attaches to the top side of cooling base  120  and extends up through the middle of blade enclosure  100 . 
     TBB  122  provides cooling to blades inserted into the slots on the front and back face of blade enclosure  100 . Blade  124  is shown positioned to be installed/inserted along axis X into one of the plurality of slots on the front side  132  of blade enclosure  100 . Once inserted, the back end  126  of blade  124  will be in thermal contact with surface  128  on the front side of the TBB  122 . Other blades (not shown) may be inserted into the slots on the back face of blade enclosure  100 . Once inserted, the back end of the blade would make thermal contact with the back face of TBB  122 . 
       FIG. 2A  is an isometric view of cooling assembly  106  with the top cover of cooling base  120  removed, in an example embodiment of the invention. TBB  122  is a generally rectangular part positioned perpendicular with, and positioned in the middle of, the top of cooling base  120 . TBB  122  is filled with a number of fluid channels that allow cooling fluid to be pumped from cooling base  120 , up and around the TBB  122 , and then back into cooling base  120  (see  FIG. 3 ). Cooling base  120  is generally a rectangular enclosure that holds the piping, pumps and heat exchanger for TBB  122 . 
       FIG. 2B  is a top view of cooling assembly  106  with the top cover of cooling base  120  removed, in an example embodiment of the invention. Cooling assembly comprises TBB  122 , a plurality of TBB pumps  252 , a heat exchanger  244 , and a heat exchanger pump  246 . A plurality of pipes couple the different elements in cooling assembly together, but are not shown for clarity. A first fluid system is fully contained within cooling assembly  106 . The first fluid cooling system runs from a TBB fluid inlet  248 , up through the fluid channels in the TBB  122 , out of the TBB fluid outlet  250 , through the heat exchange  244 , to pumps  252 , and then back to the TBB fluid inlet  248 . The first fluid system is configured to cool the TBB  122 , thereby cooling blades in thermal contact with the TBB  122 . The first fluid cooling system dumps the heat from the TBB into heat exchanger  244 . In some example embodiments of the invention, the plurality of TBB pumps  252  may be redundantly configured to provide circulation through the first fluid system even after one or more of the pumps have failed. 
     The second fluid cooling system runs from external cooling system inlet  242  to heat exchanger pump  246 , through heat exchanger  244 , and then to external cooling system exit  240 . In operation, the external cooling system inlet  242  and external cooling system exit  240  will be coupled to an external fluid cooling system that provides cooled fluid to the external cooling system inlet  242  and removes the heated fluid from the external cooling system exit  240 . In some example embodiments of the invention, heat exchanger pump  246  may be located external to blade enclosure  100 . In some example embodiments of the invention, the first and second cooling systems may be combined into only one fluid cooling system. 
       FIG. 3  is a diagram of the cooling pathways in cooling assembly  106  in one example embodiment of the invention.  FIG. 3  shows a plurality of input cooling channels  350  that go up the TBB  122 , interleaved with a plurality of return cooling channels  352  that go back down TBB  122 . In operation, cooled fluid is pumped up the cooling channels  350  and back down the return cooling channels  352 . As the cooled fluid travels around TBB  122 , heat is removed from any blades in thermal contact with TBB  122 . The heated fluid exits the TBB and flows through the heat exchanger (represented by crossed arrows  354  and  356 ). Heat from the blades is transferred to an externally cooled fluid in the heat exchanger, and then the cooled fluid is returned to the TBB  122 . Fluid cooled externally flows into cooling assembly  106  (represented by arrow  356 ), through heat exchanger, and then exits cooling assembly  106 . As the externally cooled fluid passes through the heat exchanger, the heat from the blades is transferred to the externally cooled fluid, and then flows out of cooling assembly  106 . 
     In one example embodiment of the invention, the input cooling channels  350  are interleaved with the return cooling channels  352 . By interleaving the input cooling channels with the return cooling channels, the temperature gradient across TBB  122  remains fairly constant.  FIG. 4A  is a diagram of the cooling pathways in cooling assembly  106  in another example embodiment of the invention.  FIG. 4A  shows all the input cooling channels  460  going up one side of TBB  122  and all the return cooling channels  462  going down the other side of TBB  122 . This will produce an uneven temperature gradient across TBB  122 . 
       FIG. 4B  is a diagram showing the temperature gradient of the TBB from  FIG. 4A  in an example embodiment of the invention. On the bottom right side (area  464 ) where the cool fluid first enters the TBB  122  the temperature gradient is the largest. This area  464  would provide the highest level of cooling in the blade enclosure. As the cooling fluid travels up the right side of TBB  122 , and then down the left side of TBB  122 , the fluid is warmed up as it removes heat from any blades in thermal contact with TBB  122 . Once the cooling fluid reaches the lower left side of TBB  122  (area  466 ) the fluid is the warmest and the thermal gradient is the smallest. This area  466  on the TBB  122  would provide the least amount of cooling for the blade enclosure. 
     In other example embodiments, the cooling channels in TBB  122  may be arranged in other configurations, for example having channels that flow across the TBB (instead of up and down). These channels may be configured to provide uniform cooling across the TBB, or may be configured to create zones of higher and lower cooling areas across TBB  122 . 
       FIG. 5  is an isometric view of a blade  580  in an example embodiment of the invention. Blade  580  comprises printed circuit (PC) board  582 , heat transfer plate  584 , component  586 , and a plurality of heat pipes  588 . Heat transfer plate  584  is a generally rectangular plate mounted at the back end of PC board  582 . Heat transfer plate has a front side  590  and a back side (not shown). Heat transfer plate is mounted perpendicular with the top surface of PC board  582 . Component  586  is mounted to the top surface of PC board  582 . The hot ends of the plurality of heat pipes  588  are positioned on top of component  586 . The cool ends of the plurality of heat pipes  588  are coupled to heat transfer plate  584 . In some example embodiments of the invention, electrical signals and power signals from blade  580  may connect to blade enclosure  100  through the back end of blade  580 , but these connections are not show for clarity. 
     When blade  580  is inserted into one of the plurality of blade slots in the front face of blade enclosure  100 , the back side of the heat transfer plate  584  will make thermal contact with the front face  128  of TBB  122 . During operation, heat generated by component  586  will be transferred into the hot side of the plurality of heat pipes  588 . The heat pipes will transfer the heat into heat transfer plate  584 . The heat from the heat transfer plate will be transferred into the TBB. The cooled fluid circulating inside the TBB will remove the heat from the TBB thereby cooling blade  580 . In other example embodiments of the invention, heat from component  586  may be transferred to heat transfer plate  584  using other methods instead of, or in addition too, the plurality of heat pipes. Blade  580  may comprise other element that have been removed for clarity, for example the blade sides, the blade end cover, locking devices, additional components, and the like.