Abstract:
A data center is configured using alternating rows of racks containing heat-generating electronic devices and air conditioners. Fluid, such as water or a refrigerant, for the air conditioners is supplied through pluming below a raised floor, such as those commonly found in current data centers. Attached to this plumbing are standard fluid couplings configured to couple to either air conditioners or liquid cooling units. These air conditioners and liquid cooling units use the same fluid so that they may share the plumbing. As data center migrates to liquid-cooled racks, a fraction of the air conditioners are replaced with liquid conditioning units in such a way that the data center contains both air-cooled and liquid-cooled racks without substantial reduction in efficiency of the air-cooling system. Since the air conditioners and liquid conditioning units use the same couplings and the same fluid, no infrastructure change is required.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to the field of computer data centers, and more particularly to the field of cooling computer data centers. 
   BACKGROUND OF THE INVENTION 
   Densification in data centers is becoming so extreme that the power density of the systems in the center is growing at a rate unmatched by technology developments in data center heating, ventilation, and air-conditioning (HVAC) designs. Current servers and disk storage systems generate 10,000 to 20,000 watts per square meter of footprint. Telecommunication equipment may generate two to three times the heat of the servers and disk storage systems. Liquid-cooled computers could solve this heat transfer problem, however, there is reluctance by both end users and computer manufacturers to make the transition from air-cooled computers to liquid-cooled computers. Also, there currently is no easy way to transition from an air-cooled data center to a liquid-cooled data center without a major overhaul of the data center and substantial down time to retrofit the data center. 
   Computer designers are continuing to invent methods that extend the air-cooling limits of individual racks of computers (or other electronic heat-generating devices) that are air-cooled. However, these high heat capacity racks require extraordinary amounts of air to remove the heat dissipated by the racks, requiring expensive and large air handling equipment. 
   Many modern data centers utilize a system utilizing a raised floor configured as a supply air plenum. Large HVAC units take air from near the ceiling of the data center, chill the air, and blow the cold air into the plenum under the raised floor. Vents in the floor near the servers allow cold air to be pulled up from the plenum, through the rack and the now warm air is blown out the back of the rack where it rises to the ceiling and eventually is pulled in to the HVAC units to begin the cycle anew. However, this type of system is limited in that it can only handle power of about 1600 to 2100 watts per square meter, significantly under the heat generated by many current electronic systems. Thus, the data center must contain significant amounts of empty space in order to be capable of cooling the equipment. Also, use of the under floor plenum has difficulties in that airflow is often impeded by cabling and other obstructions residing in the plenum. Further, perforated tiles limit airflow from the plenum into the data center to approximately 6 cubic meters per minute, well below the 60 cubic meters per minute required by some server racks. Even the use of blowers to actively pull cold air from the plenum and direct it to the front of the rack is insufficient to cool many modern servers. Balancing the airflow throughout the data center is difficult, and often requires a substantial amount of trial and error experimentation. Finally, the airflow is somewhat inefficient in that there is a substantial amount of mixing of hot and cold air in the spaces above the servers and in the aisles, resulting in a loss of efficiency and capacity. 
   In an attempt to increase the efficiency of raised floor plenum designs, some designers incorporate a large number of sensors through out the data center in an attempt to maximize the efficiency of the data center cooling with either static or dynamic provisioning cooling based on environmental parameters using active dampers and other environmental controls. Others may use a high pressure cooling system in an attempt to increase the cooling capacity of the raised floor plenum design. However this technique still has all of the inefficiencies of any raised floor plenum design and only increases the power handling capacity of the data center to about 3200 watts per square meter, still below the requirements of densely packed servers or telecommunication devices. 
   In a desperate attempt to increase cooling capabilities of a data center, some designers use an entire second floor to house their computer room air-conditioners (CRAC&#39;s). While this allows the use of large numbers of CRAC&#39;s without use of expensive data center floor space, it effectively acts as a large under floor plenum and is subject to the same inefficiencies and limitations of the under floor plenum design. 
   Other designers include air coolers within the server racks. For example, a liquid to air heat exchanger may be included on the back of a server rack to cool the air exiting the rack to normal room temperature. However, the airflow of the heat exchanger fans must match the airflow of the server precisely to avoid reliability and operational issues within the server. Also by mounting the heat exchanger on the racks, serviceability of the racks is reduced and the fluid lines attached to the rack must be disconnected before the rack may be moved. This results in less flexibility due to the presence of the liquid line and may require plumbing changes to the area where the rack is being moved to. Also, this technique does not directly cool the heat generating integrated circuits, it is simply a heat exchanger which is not as efficient as direct liquid cooling of the integrated circuits. 
   Another possibility is the use of overhead cooling which may offer cooling densities in the order of 8600 watts per square meter. However such overhead devices require a high ceiling that also must be strong enough to support the coolers. Also, in such a design, there is no easy migration route from air-cooled to liquid-cooled servers, and some users are concerned about the possibility of leaks from the overhead coolers dripping onto, and possibly damaging, their servers. 
   SUMMARY OF THE INVENTION 
   A data center is configured using alternating rows of racks containing other heat-generating electronic devices and air conditioners. Fluid, such as water or a refrigerant, for the air conditioners is supplied through pluming below a raised floor, such as those commonly found in current data centers. Attached to this plumbing are standard fluid couplings configured to couple to either air conditioners or liquid cooling units. These air conditioners and liquid cooling units use the same fluid so that they may share the plumbing. As data center migrates to liquid-cooled racks, a fraction of the air conditioners are replaced with liquid conditioning units in such a way that the data center contains both air-cooled and liquid-cooled racks without substantial reduction in efficiency of the air-cooling system. Since the air conditioners and liquid conditioning units use the same couplings and the same fluid, no infrastructure change is required. 
   Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a data center including alternating air-cooled racks and air conditioners according to the present invention. 
       FIG. 2  is a side view of a data center including alternating liquid-cooled racks and liquid cooling units according to the present invention. 
       FIG. 3  is a top view of a data center including alternating air-cooled racks and air conditioners according to the present invention. 
       FIG. 4  is a top view of a data center, a fraction of which includes alternating air-cooled racks and air conditioners, while another fraction includes alternating liquid-cooled racks and liquid conditioning units according to the present invention. 
       FIG. 5  is a top view of a data center including alternating liquid-cooled racks and liquid conditioning units according to the present invention. 
       FIG. 6  is a top view of a data center including alternating air-cooled racks and air conditioners according to the present invention. 
       FIG. 7  is a flow chart of a method for configuring a data center with an upgradeable, modular cooling apparatus according to the present invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a side view of a data center including alternating air-cooled racks and 15 air conditioners according to the present invention. In this example embodiment of the present invention, a data center comprising a room  100  is built including a raised floor  104  and a foundation  102 . Optionally, the room may include a false ceiling  106  for separation of the return airflow. Within the room  100  are a first air conditioning unit  108 , a first rack  110 , a second air conditioning unit  112 , a second rack  114 , a 20 third air conditioning unit  116 , and a third rack  118 . Note that in a typical data center each of these servers and air conditioning units are actually a single unit within a column of units. For example, the first rack  110  represented in this illustration may be a single server within a column of racks. See  FIG. 3  for a top view of such a data center including three columns of racks and three columns of air conditioning units, one row of which is shown in  FIG. 1 . Airflow within the room  100  is shown by gray arrows labeled  130 . Notice that the false ceiling  106  separates the warm airflow exiting the third rack  118  as it circulates back to the input of the first air conditioner  108  for increased efficiency. Optionally, small walls  120  may be used to direct the airflow up over the false ceiling, instead of allowing it to circulate back to the air input of the third rack  118 . Likewise a small wall  120  is used to prevent the warm air returning from above the false ceiling  106  from bypassing the first air conditioner  108  and flowing directly into the air input of the first rack  110  without being properly cooled. 
   Underneath the raised floor  104  may be found the plumbing required by the air conditioning units. In this example embodiment of the present invention, a building chilled fluid supply is provided through chilled fluid supply pipes  122 , and returned to the main chiller through chilled fluid return pipes  124  contained within trenches  132  in the foundation  102 . This trench is optional, but provides a place for fluids to drain in the event of any leakage, and also by placing the chilled fluid supply pipes  122  and chilled fluid return pipes  124  in the trench, there is more room for cabling with less congestion. Each air conditioning unit is connected to these chilled fluid pipes through air conditioner pipes  126  which each include a fluid coupling  128 . Note that the configuration of these pipes and couplings may vary widely according to the needs of each individual data center. In many cases water will be used as the chilled fluid, however other fluids, such as a liquid refrigerant (which may undergo a phase change during the coolant cycle), may be used in its place within the scope of the present invention. 
   Also note that while three rack and air conditioner pairs are shown in this figure, any number of rack and air conditioner pairs may be used in a similar configuration within the scope of the present invention. Also, as mentioned above, each of the racks and air conditioners shown in  FIG. 1  may actually be a single server or rack of servers or air conditioner in a column of racks or air conditioners. In the context of this patent, the term “rack” is used as a generic term for any heat-generating electronic device configured in one or more racks. As noted in the background of the invention, telecommunications switching networks require large cooling capacity and may be configured in a manner similar to that shown in  FIG. 1  within the scope of the present invention. The term “rack” is understood to include such switching networks, data storage arrays, servers, or any other heat generating electronic devices within the scope of the present invention. Also, those of skill in the art will recognize that the optional raised floor may be used for cabling, providing humidity or any other functions in addition to containing plumbing connections. 
   Those of skill in the art will recognize that there are a very wide variety of ways to configure data centers to take advantage of the present invention. There are many different ways to configure air-cooled racks with air conditioners such that the air-cooled racks may be replaced with liquid-cooled racks and the air conditioners may be replaced with liquid conditioning units without disrupting the airflow of any remaining air-cooled racks and air conditioners within the scope of the present invention. The Figures shown in this disclosure are simply a variety of example embodiments of the present invention, not a complete set of the various ways of implementing the present invention. For example, two story data centers may be build such that the air flows left to right on the first floor then is ducted up to the second floor where if flows right to left before being ducted back down to the first floor, completing the cycle. 
     FIG. 2  is a side view of a data center including alternating liquid-cooled racks and liquid cooling units according to the present invention. In this example embodiment of the present invention, a data center comprising a room  200  is built including a raised floor  104  and a foundation  102 . Optionally the room may include a false ceiling  106  and small walls  120  as shown in  FIG. 1  even though they are not required for the liquid-cooled rack configuration shown in the present illustration. Within the room  200  are a first liquid conditioning unit  202 , a first rack  204 , a second liquid conditioning unit  206 , a second rack  208 , a third liquid conditioning unit  210 , and a third rack  212 . Note that in a typical data center each of these racks and liquid conditioning units are actually a single unit within a column of units. For example, the first rack  204  represented in this illustration may be a single server within a column of racks. See  FIG. 5  for a top view of such a data center including three columns of racks and three columns of liquid conditioning units, one row of which is shown in  FIG. 2 . The liquid conditioning units are connected with the racks through a pair of liquid supply pipes including a chilled liquid pipe  214  and a warm liquid pipe  216  used to return the now heated liquid from the servers to the liquid conditioning units. 
   Underneath the raised floor  104  may be found the plumbing required by the liquid conditioning units. In this example embodiment of the present invention, a building chilled fluid supply is provided through chilled fluid supply pipes  122 , and returned to the main chiller through chilled fluid return pipes  124  contained within trenches  132  in the foundation  102 . Each liquid conditioning unit is connected to these chilled fluid pipes through liquid conditioner pipes  126  which each include a fluid coupling  128 . Note that the configuration of these pipes and couplings may vary widely according to the needs of each individual data center. For example, some data centers may be configured with the fluid supply pipes overhead instead of under a raised floor. However, the fluid couplings  128  must be configured to couple to both air conditioners and liquid conditioning units so that an air conditioner may be replaced by a liquid conditioning unit simply by disconnecting the fluid couplings  128  from the air conditioner and connecting the same fluid couplings  128  to the liquid conditioning unit. In many cases water will be used as the chilled fluid, however other fluids, such as a liquid refrigerant (which may undergo a phase change during the coolant cycle), may be used in its place within the scope of the present invention. 
   Also note that while three rack and liquid conditioner pairs are shown in this figure, any number of rack and liquid conditioner pairs may be used in a similar configuration within the scope of the present invention. Also, as mentioned above, each of the racks and liquid conditioners shown in  FIG. 2  may actually be a single rack or liquid conditioner in a column of servers or air conditioners. In the context of this patent, the term “rack” is used as a generic term for any heat-generating electronic device configured in one or more racks. As noted in the background of the invention, telecommunications switching networks require large cooling capacity and may be configured in a manner similar to that shown in  FIG. 2  within the scope of the present invention. The term “rack” is understood to include such switching networks, data storage arrays, servers, or any other heat generating electronic devices within the scope of the present invention. 
     FIG. 3  is a top view of a data center including alternating air-cooled racks and air conditioners according to the present invention. In this example embodiment of the present invention, a data center containing 18 racks  302  and 18 air conditioning units  300  is built within a room  100 . Note that while this example embodiment uses a 1:1 ratio of racks to air conditioning units, depending on the capacity of the air conditioning units and the thermal needs of the racks, other ratios of racks to air conditioning units may be used within the scope of the present invention. As in  FIG. 1 , airflow is represented by gray arrows labeled  130 . Notice that the three pairs of racks and air conditioners shown in  FIG. 1  are now seen to be individual racks and air conditioners each within a column of six racks  302  or six air conditioners  300 . Air enters the first air conditioner  108  on the right hand side of this figure. Once the now-chilled air leaves the first air conditioner  108  it enters the air intake of the first rack  110 . When the heated air leaves the first server  110  it flows into the air intake of the second air conditioner  112 . Once the now-chilled air leaves the second air conditioner  112  it enters the air intake of the second rack  114 . When the heated air leaves the second rack  114  it flows into the air intake of the third air conditioner  116 . Once the now-chilled air leaves the third air conditioner  116  it enters the air intake of the third rack  118 . Upon exiting the third rack  118  the now-heated air is re-circulated to the air intakes of the first air conditioner  108 . 
     FIG. 4  is a top view of a data center, a fraction of which includes alternating air-cooled racks and air conditioners, while another fraction includes alternating liquid-cooled racks and liquid conditioning units according to the present invention. This example embodiment of the present invention illustrates the ease with which the air-cooled racks may be replaced with liquid-cooled racks without disruption of the airflow required by the air-cooled racks and without changes in the infrastructure of the data center. In this example embodiment of the present invention, each column of racks comprises three liquid-cooled racks and three air-cooled servers. Likewise, each column of conditioners comprises three liquid conditioning units and three air conditioning units. While this example embodiment shows the liquid-cooled and air-cooled racks in a 1:1 ratio, those of skill in the art will recognize that using the configuration of the present invention, any ratio of liquid-cooled to air-cooled racks may be used without disruption of the airflow required by the air-cooled racks as long as each row of servers and conditioners is either air or liquid cooled, but not a combination of both. Airflow between the air-cooled racks  302  and the air conditioners  300  is once again represented by gray arrows labeled  130 . Similarly, the connections between the liquid-cooled racks  404  and the liquid conditioning units  402  are shown as a chilled liquid pipe  214  and a warm liquid pipe  216  used to return the now-heated liquid from the liquid-cooled racks  404  to the liquid conditioning units  402 . 
     FIG. 5  is a top view of a data center including alternating liquid-cooled racks and liquid conditioning units according to the present invention. Once the entire data center is converted to liquid-cooled racks  404  and liquid conditioning units  402 , there is no longer any need for airflow within the data center, so none is shown in this example embodiment of the present invention. This example embodiment is similar to that shown in  FIG. 4  with the exception that all of the air-cooled racks and air conditioners have now been replaced with liquid-cooled racks  404  and their corresponding liquid conditioning units  402  in a seamless migration without any infrastructure changes needed. 
     FIG. 6  is a top view of a data center including alternating air-cooled racks and air conditioners according to the present invention. This example embodiment of the present invention is an alternate configuration to that shown in  FIGS. 1 and 3 . In this example embodiment, the airflow cycle assumes a circular path around the perimeter of the room  600  instead of forming a vertical circular path along the ceiling of the room  600 . Thus there is no longer any need for a false ceiling as shown in  FIG. 1 . However, to separate the airflows, it may be desirable to include some optional small walls  602  down the center of the data center. However, since at any given point along these optional small walls  602 , the air temperature is roughly the same on both sides of the walls, they are not really necessary for cooling efficiency. 
   Those of skill in the art will recognize that this configuration of the present invention also allows easy transition from air-cooled racks to liquid-cooled racks by replacing a row at a time from the outside of the data center working in to the center of the room, or by replacing a row at a time from the inside of the data center working out to the edges of the room. 
     FIG. 7  is a flow chart of a method for configuring a data center with an upgradeable, modular cooling apparatus according to the present invention. In a step  700 , a room is provided. In a step  702 , a chilled fluid supply pipe is provided within said room. In a step  704 , a chilled fluid return pipe is provided within said room In a step  706  a plurality of fluid couplings are attached to said chilled fluid supply pipe and said chilled fluid return pipe, wherein each of said fluid couplings is configured to connect to either an air conditioner or a liquid conditioning unit. In a step  708 , first and second air-cooled servers are provided. In a step  710 , first and second air conditioners are provided. In a step  712 , the first air-cooled server is configured such that chilled air exiting said first air conditioner enters air intakes of said first air-cooled server. In a step  714 , the second air conditioner is configured such that warm air exiting said first air-cooled server enters air intakes of said second air conditioner. In a step  716 , the second air-cooled server is configured such that chilled air exiting said second air conditioner enters air intakes of said second air-cooled server. In an optional step  718 , a third air-cooled server is provided. In an optional step  720 , a third air conditioner is provided. In an optional step  722 , the third air conditioner is configured such that warm air exiting said second air-cooled server enters air intakes of said third air conditioner. In an optional step  724 , the third air-cooled server is configured such that chilled air exiting said third air conditioner enters air intakes of said third air-cooled server. In an optional step  726 , a raised floor is provided. In an optional step  728 , a chilled fluid supply pipe is provided under said raised floor. In an optional step  730 , a chilled fluid return pipe is provided under said raised floor. In an optional step  732 , the air conditioners are coupled to said chilled fluid supply pipe and said chilled fluid return pipe. 
   The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.