Abstract:
A cooling unit which improves the cooling efficiency of a server rack and minimizes rise in the server room temperature. A cooling unit for a server rack housing a server with a heat source includes: a fan unit having an array of fans for discharging hot air generated by the heat source from the rack; and a radiator unit having an array of pipes for guiding coolant to remove heat from the hot air discharged from the rack by rotation of the fans; and a frame unit which integrally combines the fan unit and the radiator unit. The cooling unit constructs a back door from which the hot air inside the rack is discharged.

Description:
CLAIM OF PRIORITY 
       [0001]    The present application claims priority from Japanese patent application JP 2008-205804 filed on Aug. 8, 2008, the content of which is hereby incorporated by reference into this application. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a cooling unit, an electronic apparatus rack, a cooling system and construction methods thereof, and in particular, relates to a cooling panel for cooling a server rack with coolant, a cooling structure of the server rack, a server cooling system and a construction method thereof. 
       BACKGROUND OF THE INVENTION 
       [0003]    A conventional technique of cooling a server rack is for an example a rack cooling structure disclosed in JP-A No. 2004-63755 in which cold air sent from an air conditioning unit is supplied to an air supply port on a lower part of the rack to cool an apparatus inside the rack and the air heated by the apparatus and discharged from an exhaust port on an upper part of the rack is sent back to the air conditioning unit for circulation. 
         [0004]    Furthermore, JP-A No. 2006-93388 discloses a server rack cooling device in which cold air is supplied from a cooler unit through an exchangeable panel to a downflow unit detachably mounted on a front upper part of the inside of a server rack and the downflow unit forces cold air to flow downward to cool an electronic apparatus and waste heat from the cooler unit is discharged through an outdoor exhaust duct to the outside of the room. 
         [0005]    In both the techniques described in the above patent documents, the apparatus inside the rack is cooled by blowing cold air to it and it is important to deal with heated air (hot air) inside the rack. In the technique described in JP-A No. 2004-63755, heated air inside the rack is circulated through the air conditioning unit but the room temperature rises due to waste heat discharged from the server and the air conditioning unit. For this reason, an air conditioner for the room must be operated sufficiently to prevent the room temperature from going up. In this approach, the rack cooling efficiency is low and power consumption is unavoidably increased. 
         [0006]    In the technique described in JP-A No. 2006-93388, since hot air inside the rack is discharged through the outdoor exhaust duct to the outside of the room, the room temperature does not rise. 
         [0007]    However, in both the techniques, the apparatus inside the rack which has become hot is cooled by blowing cold air and the cooling efficiency is not high. Also in these techniques, cold air or hot air or exhaust air is led into the server rack, which necessitates considerable design change in the server rack inner structure and/or change in the location of the electronic apparatus inside the rack or its mounting structure. This leads to a rise in cost. 
         [0008]    Because of the need for such design change, these techniques can be applied only to new server rack models and it is difficult to apply the techniques to server racks already installed at customer sites. Therefore, customers who use old models still have no choice but to rely on the conventional cooling method in which the server room is cooled. 
       SUMMARY OF THE INVENTION 
       [0009]    An object of the present invention is to provide a cooling unit, an electronic apparatus rack, a rack door of the electronic apparatus rack and a cooling system in which improve the cooling efficiency by leading coolant into the cooling unit located in the electronic apparatus rack and a construction method thereof. 
         [0010]    Another object of the present invention is to provide a cooling unit which can be attached to an existing electronic apparatus rack and easily attached during operation of the apparatus. 
         [0011]    A further object of the present invention is to provide a cooling unit which can be easily attached to an exhaust ventilation side of an electronic apparatus rack depending on apparatus size. 
         [0012]    According to an aspect of the present invention, a cooling unit for cooling a rack housing an electronic apparatus with a heat source includes a fan unit having a plurality of fans for discharging hot air generated by the heat source from the rack, and a radiator unit having a plurality of pipes for guiding coolant to remove heat from the hot air discharged from the rack by rotation of the fans. The fan unit and the radiator unit are integrated into a structure. 
         [0013]    Preferably the cooling unit further includes a frame unit for holding and fixing the fan unit and the radiator unit integrally. The cooling unit constructs a door of the rack on an exhaust ventilation side thereof and the door has a mounting mechanism for attaching the door to the exhaust ventilation side of the rack in an openable and closable manner. 
         [0014]    According to another aspect of the invention, a rack door to be attached to a rack housing an electronic apparatus with a heat source includes a fan unit having an array of fans for discharging hot air generated by the heat source from the rack, a radiator unit having an array of pipes for guiding coolant to remove heat from the hot air discharged from the rack by rotation of the fans, and a mounting mechanism for attaching the door to an exhaust ventilation side of the rack preferably in an openable and closable manner. The fan unit and the radiator unit are integrally combined to construct the door. 
         [0015]    According to another aspect of the invention, an electronic apparatus rack housing an electronic apparatus with a heat source, includes: a cooling unit integrally holding and fixing a fan unit and a radiator unit, where the fan unit has a plurality of fans for discharging hot air generated by the heat source from the rack, and the radiator unit has an array of pipes for guiding coolant to remove heat from hot air discharged from the electronic apparatus by rotation of the fans. The cooling unit is attached to an exhaust ventilation side of the rack and coolant is circulated in the pipes to cool the electronic apparatus. 
         [0016]    According to another aspect of the invention, a cooling system for cooling a rack housing an electronic apparatus with a heat source includes: a frame unit attached on an exhaust ventilation side of the rack, where the frame unit integrally holds and fixes a fan unit and a radiator unit, the fan unit has an array of fans for discharging hot air generated by the heat source from the rack, and the radiator unit has an array of pipes for guiding coolant to remove heat from the hot air discharged from the electronic apparatus by rotation of the fans; hoses connected to the pipes for circulation of coolant; and a heat exchanger connected to the hoses. 
         [0017]    Preferably the heat exchanger is an AW (Air Water) heat exchanger or AC (Air Chiller) heat exchanger. 
         [0018]    According to another aspect of the invention, a method for constructing a cooling system for cooling a rack housing an electronic apparatus with a heat source includes the steps of: removing a first door fixed on a prescribed part of the rack housing an electronic apparatus; attaching a second door to the prescribed part in an openable and closable manner, where the second door integrally holds and fixes a fan unit having an array of fans for discharging hot air generated by the heat source from the rack, and a radiator unit having an array of pipes for guiding coolant to remove heat from the hot air discharged from the rack by rotation of the fans; attaching hoses for circulation of coolant to the pipes; and attaching a heat exchanger to the hoses. 
         [0019]    In the above method, preferably, the second door matched to the first door&#39;s size is prepared and attached. 
         [0020]    Furthermore, in the above method, preferably, when the electronic apparatus is in operation, the first door is removed and then the second door is attached. 
         [0021]    According to the present invention, by introducing coolant into a cooling unit installed for an electronic apparatus, a higher cooling efficiency is achieved in the cooling unit, electronic apparatus cooling structure and electronic apparatus cooling system. 
         [0022]    In addition, the cooling unit can be easily attached to an existing electronic apparatus rack, even when the electronic apparatus is in operation. Also the cooling unit matched to the size of the electronic apparatus can be easily attached on the exhaust ventilation side of the electronic apparatus. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is an exploded perspective view of the cooling structure for a server rack according to an embodiment of the present invention; 
           [0024]      FIG. 2  is an exploded perspective view of the structure of a cooling unit  1  according to the embodiment; 
           [0025]      FIG. 3  is a back view of the structure of a pipe assembly of a radiator unit  11  according to the embodiment; 
           [0026]      FIG. 4  is a front view of the structure of the radiator unit  11  according to the embodiment; 
           [0027]      FIG. 5  is a back view of the structure of the radiator unit  11  according to the embodiment; 
           [0028]      FIG. 6  is a back view of the structure of a frame unit  12  according to the embodiment; 
           [0029]      FIG. 7  is a back view of the structure of a fan unit  13  according to the embodiment; 
           [0030]      FIG. 8  is a perspective view of the internal structure of the cooling unit  1  according to the embodiment; 
           [0031]      FIG. 9  shows part of a pipe assembly  22  of the radiator unit  11  according to the embodiment; and 
           [0032]      FIG. 10  shows an example of a server rack cooling system configuration according to the embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]    Next, an embodiment of the present invention will be described referring to the accompanying drawings. 
         [0034]      FIG. 1  shows a server rack cooling structure. 
         [0035]    A cooling unit  1  is attached to the back of a server rack  9 . The server rack  9  houses plural blade servers  91 , for example, eight in total on its four shelves with two on each shelf. Each of the blade servers  91  is an electronic apparatus housing electronic components such as a CPU, memory, hard disk and power supply and blower fan where the power supply and memory are heat sources. In the server rack  9 , installed in a server room, the blower fan of each blade server takes in cooling air from ahead of the blade server or apparatus (direction indicated by arrow A) and discharges the air heated therein (hot air) through the back of the apparatus (exhaust ventilation side) to the outside of the apparatus (direction indicated by arrow B). 
         [0036]    The server rack  9  may have a conventional structure. Originally the conventional server rack  9  had a back door which can be opened and closed for maintenance of the servers, in place of the cooling unit  1 . In other words, an outstanding feature of the present invention may be that the back door of the conventional server rack is removed and replaced by a back door with a novel cooling unit  1 . If the server rack  9  is a new model, the cooling unit  1  according to this embodiment is an integral part thereof. 
         [0037]    The cooling unit  1  includes a radiator unit  11  for removing the heat from hot air discharged from the back of the rack; a fan unit  13  having many fans (for example,  36  fans or  12  rows by  3  columns) for forcibly discharging hot air; and a frame unit  12  to which the radiator unit  11  and fan unit  13  are integrally attached. That is, the integrally structured cooling unit  1  is constructed as a back door of the server rack  9 . Details of these units will be described later referring to  FIGS. 2 to 8 . 
         [0038]    The radiator unit  11  has an array of pipes through which coolant (for example, water) circulates. Hoses  81  and  82  through which coolant is passed are connected to ends of the pipes. In the hose  81 , the coolant which has not absorbed heat yet flows in the direction indicated by arrow C 1  and in the hose  82 , the coolant which has absorbed heat flows in the direction indicated by arrow C 2 . 
         [0039]    The structure of the cooling unit  1  will be described in detail referring to  FIGS. 2 to 8 . 
         [0040]    The frame unit  12  with the radiator unit  11  and fan unit  13  integrally attached thereto constructs a back door for cooling which is attached to the server rack  1  located on the right as viewed in  FIG. 2 . Here, a view taken from the right (server rack) side in  FIG. 2  is referred to as a front view (for example,  FIG. 4 ) and a view taken from the left side in  FIG. 2  is referred to as a back view ( FIGS. 5 ,  6 , and  7 ). 
         [0041]    For the sake of easy understanding, the structure of the frame unit  12  will be first described. 
         [0042]    As shown in  FIGS. 2 ,  6 , and  8 , the frame unit  12  includes a radiator unit housing frame  31  for housing and holding the radiator unit  11  and a fan frame housing frame  32  for housing and holding the fan unit  13 . 
         [0043]    The radiator unit housing frame  31  should have enough thickness W 1  to house the radiator unit  11  (thickness W 1 ′) and the fan frame housing frame  32  should have enough thickness W 2  to house the fan unit  13  (thickness W 2 ′). 
         [0044]    For example, the radiator unit housing frame  31  has four recesses  311  to align with engaging points  225  in frames  1101  and  1102  of the radiator unit  11 , and four screw holes  312  for fixing the radiator unit  11  with screws. The fan frame housing frame  32  has, for example, six screwing points  36  on the right and left for fixing the fan unit  13  with screws. 
         [0045]    Furthermore, the frame unit  12  includes hinges  35  to attach the back door, an integrated combination of the radiator unit  11  and fan unit  13 , to the back of the server rack  9  in an openable and closable manner. The back door attached to the server rack  9  can be opened and closed using a knob  37 . 
         [0046]    The frame unit  12  is provided with a typical lock mechanism (not shown) and service personnel for the server rack  9  is only allowed to unlock the lock mechanism and open the back door when necessary. 
         [0047]    Next, the structure of the radiator unit  11  will be described referring to  FIGS. 2 to 5  and  FIGS. 8 and 9 . 
         [0048]    As illustrated in  FIG. 2 , the radiator unit  11  has a protective panel  21  facing the server rack  9  and a pipe assembly  22  ( FIG. 3 ) located on the inside thereof which are fixed in the frames  1101  and  1102  of the radiator unit  11 . 
         [0049]    The protective panel  21 , intended to protect the pipe assembly  22 , is an aluminum plate with many slits on a surface thereof. The hot air discharged from the server rack  9  flows through the slits in the protective panel  21  to the pipe assembly  22 . 
         [0050]      FIGS. 3 to 5  show the structure of the pipe assembly of the radiator unit  11 . 
         [0051]      FIGS. 4 and 5  illustrate the pipe assembly fixed in the frames  1101  and  1102  of the radiator unit  11  (the protective panel  21  is not shown). 
         [0052]    The main component of the radiator unit  11  is the pipe assembly  22  as a cluster of folded pipes. The pipe assembly  22  includes a pair of lower pipes  221  for circulation of coolant, a pair of vertical pipes  2221  and  2222  which are connected to the lower pipes  221  and vertically disposed, upper pipes  2231  and  2232  connected to the vertical pipes  2221  and  2222 , and horizontal pipes  224  which are connected to the vertical pipes  2221  and  2222  respectively and zigzag-folded and disposed horizontally. 
         [0053]    The lower pipe  2211 , vertical pipe  2221 , and upper pipe  2231  are inflow pipes which allow coolant before heat absorption to flow in the direction indicated by arrow C 1 . The lower pipe  2212 , vertical pipe  2222 , and upper pipe  2232  are outflow pipes which allow coolant after heat absorption to flow in the direction indicated by arrow C 2 . The other ends of the lower pipes  221  are connected to a heat exchanger  86  through hoses ( FIG. 10 ). The coolant in the outflow pipe  2212  which has absorbed heat flows to the heat exchanger  86 , thereby constituting a cooling system with coolant circulation. 
         [0054]    The pipe assembly  22  is mainly constructed of horizontal pipes  224  as a cluster of pipes and it may be said that the horizontal pipes  224  produce a cooling effect. The horizontal pipes  224  are a pipe cluster having plural horizontal pipe sets  2241  to  224   n,  each set having three folded pipes. These horizontal pipe sets  2241  to  224   n  are disposed vertically along the vertical pipes  2221  and  2222  and the pipe ends of each horizontal pipe set are welded to the vertical pipes to construct the pipe assembly  22 . 
         [0055]    Next, the horizontal pipe sets as components of the pipe assembly  22  will be described referring to  FIG. 9 . 
         [0056]    The horizontal pipe set  224   n  has plural pipes  2240  passing through holes in many rectangular fins  231  in a row with neighboring U-folded ends of the pipes  2240  welded to each other, thereby constituting a single horizontal pipe. One end  22401  of the pipes  2240  is connected to the vertical pipe  2221  and another end  22402  is connected to the vertical pipe  2222 . The fins  231  are made of aluminum which is effective in heat radiation and hot air passes through slits  232  made between fins  231 . The identical rectangular fins  231 , which are penetrated by the pipes  224   n  and disposed at regular intervals, not only guide hot air toward a given direction but also support the pipes  224   n  securely. 
         [0057]    The pipe assembly  22  is fitted in the frames  1101  and  1102  by fixing clamps on appropriate points of the pipes (vertical pipes  222 *, upper pipes  223 *, horizontal pipes  224 *). 
         [0058]    An alternative approach is that the rightmost fin  2311  and leftmost fin  2312  shown in  FIG. 9  also serve as members of the frames  1101  and  1102 . If the leftmost and rightmost fins  2311  and  2312  construct the frames  1101  and  1102 , the entire pipe assembly  22  is sturdier. 
         [0059]    In  FIG. 3 , the fins  231  are omitted and in  FIGS. 4 and 5 , the fins  231  are represented by vertical lines. 
         [0060]    As illustrated in  FIGS. 4 and 5 , a lot of rectangular slits  232  are formed by the fins  231  of the pipe assembly  22  in the radiator unit  11 . The fins  231  guide hot air discharged from the server rack  9  toward the pipe assembly  22  by rotation of fans  43  and further guide the hot air passed through the pipe assembly  22  toward the fan unit  13 . The fins  231  and slits  232  thus form flow channels for hot air and increase the efficiency of heat absorption by coolant circulating in the pipe assembly  22 . 
         [0061]    Joints  261  and  262  are fixed to ends of the lower pipes  2211  and  2212  respectively. A hose  81  for circulation of coolant from the heat exchanger  86  ( FIG. 10 ) is connected to the joint  261  and a hose  82  which sends the coolant having absorbed heat to the heat exchanger  86  is connected to the joint  262 . An opening/closing lever  27  is provided on the joint  261  to control circulation of the coolant sent through the hose  81 . 
         [0062]    The length, width and thickness W 1 ′ of the radiator unit  11  are such that the radiator unit  11  fits in the radiator unit housing frame  31  of the frame unit  12 . 
         [0063]    Convex tabs  225  as hooks to be engaged with the recesses  311  of the frame unit  12  are provided, for example, at four places on the rim of the radiator unit  11 . These tabs  225  engage with the recesses  311  to fix the radiator unit  11  in the radiator unit housing frame  31  of the frame unit  12 . 
         [0064]      FIG. 8  illustrates the radiator unit  11  fixed in the frame unit  12 . In the figure, the protective panel  21  of the radiator unit  11  and the fins  231  of the pipe assembly  22  are omitted so that the inside of the pipe assembly  22  is visible. 
         [0065]    Next, the structure of the fan unit will be described. 
         [0066]    As illustrated in  FIGS. 2 and 7 , the fan unit  13  has an iron fan frame  41  which is divided into thirty-six boxes  42  (twelve rows by three columns), with a fan  43  placed in each box  42 . Alternatively the fan frame  41  may include an upper frame  42  and a lower frame  42  which are bonded to each other where eighteen boxes (six rows by three columns) are formed in each of the upper and lower frames. Plural screwing points  46  are provided on the rim of the fan frame  41  to screw the fan unit  13  on mounting points  36  of the frame unit  12 . The length, width and thickness W 2 ′ of the fan frame  41  are such that the fan frame  41  fits in the fan frame housing frame  32  of the frame unit  12 . The screwing points  36  and mounting points  46  are respectively joined by screwing. 
         [0067]    As the fans  43  rotate, hot air from the back of the server rack  9  is forced out. 
         [0068]    Power cords for power supply to the fans  43  are embedded inside the fan frame  41 , though invisible in the figure. 
         [0069]      FIG. 10  shows an example of a server rack cooling system configuration. 
         [0070]    In this example, two server racks  9  each having a cooling unit  1  are installed in a server room. The server room has a free-access floor  99  and hoses  81  and  82  for circulation of coolant are laid under the floor  99  with one end of each hose connected through a pump  85  to a heat exchanger  86  installed outdoors. The pump  85  is run to force coolant to circulate. 
         [0071]    The heat exchanger  86  is an AC (Air Chiller) heat exchanger or AW (Air Water) heat exchanger. If an AC heat exchanger as illustrated is employed, the pump  85  is installed midway on the hose  81  for circulation of coolant and coolant is forced to circulate by operation of the pump. The AC heat exchanger  86  releases the heat of the coolant in the direction indicated by arrows W by rotation of the fan. The AC heat exchanger is expected to produce a cooling effect which is strong enough to cool plural racks at a time. 
         [0072]    On the other hand, the AW heat exchanger can be installed in the same room where the server racks to be cooled are installed, though its cooling ability is slightly lower than that of the AC heat exchanger. Since the AW system eliminates the need for outdoor installation work, it is easier to introduce the cooling system than when the AC heat exchanger is employed. 
         [0073]    Whether it is the AC system or the AW system, a higher cooling efficiency is ensured than in the conventional server rack cooling system; therefore, electronic apparatuses or electronic components can be mounted densely in the rack. In addition, since both the AC system and AW system can use the same cooling unit  1 , even when the AW cooling system is initially employed, it can be easily replaced by the AC system later in order to increase the cooling capacity. Specifically, in this case, the AW heat exchanger  86  should be replaced by the AC heat exchanger. 
         [0074]    If another server rack  9  is added to the system shown in the figure, hoses  81 ′ and  82 ′ are connected to the new server rack and the other ends of the hoses are connected to the common hoses  81  and  82 . 
         [0075]    As explained so far, according to this embodiment, a cooling system with a higher cooling efficiency can be constructed by removing the back door of a conventional server rack and replacing it by a back door as a cooling unit according to this embodiment. In this case, since there is no need to change the arrangement of components mounted inside the conventional server rack, the cooling system can be constructed while the servers are in operation. 
         [0076]    Although the amount of generated heat depends on the server rack size and the number of servers housed in the rack, in this embodiment the size of the back door as a cooling unit can be freely changed depending on the size of the server rack to which it is attached. It is also possible to change the number of fans  43  in the fan unit  13  depending on the amount of heat generated by servers. Further, the AW system or AC system can be selected according to the amount of heat generated by servers inside the server rack or the number or capacity of servers installed in the server room. Also, even in the same cooling system, it is possible to cope with change in the number or capacity of servers by altering the heat exchanger capacity. 
         [0077]    The present invention is not limited to the above embodiment but it may be embodied in various other forms. 
         [0078]    For example, in the above embodiment, the cooling unit is used for the back door of the server rack, but it is not limited thereto. If an electronic apparatus rack is designed to discharge hot air inside it through its top surface or lateral surface, the cooling unit according to this embodiment can be attached to the top or lateral surface. If it is attached to the top surface and need not be openable, it may be attached in a fixed manner. 
         [0079]    In the above embodiment, the radiator unit  11  and the fan unit  13  are integrally fitted in the frame unit  12 . However, the frame unit  12  may not be a separate unit. For example, the fan frame  41  as the outer frame of the fan unit  13  may be a sturdy structure or a fan frame designed to hold and fix the fan unit instead of the frame unit. Also, if a sturdy frame-like structure for holding and fixing the radiator unit  11  is provided, the structure may be used as the frame unit  12 . 
         [0080]    The number of fans  43  in the fan unit  13  may be varied as needed. In the case of a large server rack, more fans may be needed and the fan unit  13  shown in  FIG. 7  may be larger. 
         [0081]    Also the arrangement and number of fans  43  in the fan unit  13  may be varied as needed. If four blade servers are mounted only on the two upper shelves of the server rack  9  shown in  FIG. 1 , the fan unit  13  need not have as many fans  43  as required to cover the whole back surface of the rack  9  but it may be sufficient that it has only as many fans  43  as required to cover the blade absorbers on the two upper shelves. 
         [0082]    In the above embodiment, the cooling unit is applied to server racks which house blade servers. However, it may also be applied to electronic apparatus racks housing electronic apparatuses with heat sources such as disk array devices housing may disk units or communication racks housing plural communication devices. 
         [0083]    From the viewpoint of cost, it is desirable to use water as coolant but another kind of coolant may also be used.