Server system

Abstract

A server system according to the present disclosure comprises: a rack group in which a plurality of racks for accommodating a heating element to be cooled by a refrigerant are arranged side by side in a horizontal first direction; heat exchange units that are provided in a state of respectively corresponding to the racks and exchange heat between the refrigerant and air above the racks; and a duct that forms, above the plurality of heat exchange units, a discharge flow path which extends in the horizontal first direction and is for discharging the air that has exchanged heat in the heat exchange units toward the horizontal first direction.

Description

Server System

[0001] This application claims priority to Japanese Patent Application No. 2023-206792, filed on December 7, 2023, the contents of which are incorporated herein by reference.

[0002] In a system provided with a heat generating element, it is necessary to remove the heat generated by the heat generating element. For example, Patent Document 1 discloses a cooling device that receives heat from the heat generating element to be cooled and naturally circulates a refrigerant.

[0003] Furthermore, for example, in data centers, a large number of racks housing servers are installed in a server room. Chips such as CPUs and GPUs installed in the servers generate heat during operation. Servers may malfunction if their temperature exceeds a certain range. For this reason, it is necessary to cool the server room. One cooling method for server rooms is the air-cooling method, which uses air conditioners to cool and circulate the air inside the server room.

[0004] JP 2015-06414 A

[0005] However, when server racks are densely packed into the limited space of a server room, air cooling requires a lot of energy. Therefore, building a system that can efficiently remove heat has been a challenge. Furthermore, when servers generate a lot of heat, air cooling may not have enough cooling capacity.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a server system that can efficiently dissipate heat. The present disclosure has been made to solve the above-mentioned problems, and aims to provide a server system that can adjust cooling capacity according to the amount of heat generated.

[0007] In order to solve the above problems, the server system of the present disclosure comprises a group of racks configured by arranging multiple racks in a horizontal first direction, each rack housing a heat generating element cooled by a refrigerant, a heat exchange unit provided corresponding to each rack and performing heat exchange between the refrigerant and air above each rack, and a duct extending in the horizontal first direction above the multiple heat exchange units to form an exhaust flow path for discharging the air that has exchanged heat in each of the heat exchange units toward the horizontal first direction.

[0008] A server system according to the present disclosure includes a rack that accommodates a heat generating element that is cooled by a refrigerant, a heat exchange unit that is provided corresponding to the rack and that exchanges heat between the refrigerant and air above the rack, a duct that forms an exhaust flow path above the heat exchange unit for discharging air that has exchanged heat in the heat exchange unit, a cooling component that is attached to the heat generating element and through which the refrigerant can flow and that cools the heat generating element by exchanging heat with the refrigerant, an air-cooling fan that blows air to the heat exchange unit to cool the heat exchange unit, a refrigerant cooler that cools the refrigerant by exchanging heat with a second refrigerant, and the heat exchange unit and the cooling component are provided, and the refrigerant a refrigerant circulation flow path having: a natural circulation flow path that naturally circulates the refrigerant by thermal convection; a forced circulation flow path that bypasses a portion of the natural circulation flow path and forcibly circulates the refrigerant without relying on thermal convection; and a refrigerant cooling flow path that bypasses a portion of the natural circulation flow path and is provided with the refrigerant cooler; and a switching mechanism that is provided in the refrigerant circulation flow path and is capable of switching the flow path of the refrigerant between a flow path in which the refrigerant passes through the forced circulation flow path and a flow path in which the refrigerant does not pass through the forced circulation flow path, and is also capable of switching the flow path of the refrigerant between a flow path in which the refrigerant passes through the refrigerant cooling flow path and a flow path in which the refrigerant does not pass through the refrigerant cooling flow path.

[0009] The server system according to the present disclosure comprises a group of racks configured by arranging a plurality of racks, each housing a heat generating element, in a first horizontal direction; a cooling fan provided in each of the racks for supplying air to the heat generating element and discharging the air that has passed through the heat generating element outside the rack; and a duct extending in the first horizontal direction above the group of racks to form an exhaust flow path for discharging the air exhausted from the rack by the cooling fan in the first horizontal direction.

[0010] The server system of the present disclosure can efficiently exhaust heat and adjust the cooling capacity according to the amount of heat generated.

[0011] 1 is a view of a server system according to a first embodiment of the present disclosure, viewed from the width direction; FIG. 2 is a view of a server group and a duct according to a first embodiment of the present disclosure, viewed from above; FIG. 3 is a perspective view showing the general shapes of a server group and a duct according to the first embodiment of the present disclosure; FIG. 4 is a view of a rack, a heat exchanger, and a refrigerant circulation channel according to the first embodiment of the present disclosure; FIG. 5 is a view of a heat exchanger according to a first embodiment of the present disclosure, viewed from the depth direction; FIG. 6 is a view of a heat exchanger according to a second embodiment of the present disclosure, viewed from the depth direction; FIG. 7 is a view of a heat exchanger according to a second embodiment of the present disclosure, viewed from the width direction; FIG. 8 is a view of a heat exchanger according to a third embodiment of the present disclosure, viewed from the depth direction; FIG. 9 is a view of a heat exchanger according to a third embodiment of the present disclosure, viewed from the width direction; FIG. 10 is a view of a rack, a heat exchanger, and a refrigerant circulation channel according to a fourth embodiment of the present disclosure; FIG. 11 is a view of a rack, a heat exchanger, and a refrigerant circulation channel according to a fifth embodiment of the present disclosure; FIG. 12 is a view for explaining operation switching of a server system according to a fifth embodiment of the present disclosure; FIG. 13 is a view of a server system according to a sixth embodiment of the present disclosure, viewed from the width direction; FIG. 14 is a view of a server system according to a seventh embodiment of the present disclosure, viewed from the depth direction; FIG. 15 is a view of a server system according to an eighth embodiment of the present disclosure, viewed from the depth direction; FIG. 16 is a view of a server system according to a ninth embodiment of the present disclosure, viewed from the depth direction; 16A and 16B are views of a server system according to a tenth embodiment of the present disclosure as viewed from the width direction, and a view of a server system according to an eleventh embodiment of the present disclosure as viewed from above.

[0012] First Embodiment (Configuration of Server System) A server system 1 according to a first embodiment of the present disclosure will be described below with reference to Figures 1 to 5. As shown in Figure 1, the server system 1 includes a server center 2, a group of racks 10, a heat exchanger 20, a filter 3, a duct 30, a support material 4 (see Figure 5), a cooling component 5 (see Figure 4), and a refrigerant circulation channel 40 (see Figure 4).

[0013] (Server Center) A server room 2a is provided on each floor of the server center 2. Each server room 2a houses various devices and equipment that make up the server system 1, such as rack groups 10, heat exchange units 20, filters 3, ducts 30, support materials 4, cooling components 5, and refrigerant circulation channels 40.

[0014] 1 to 3, the rack group 10 is made up of a plurality of racks 11. Each rack 11 is formed in a rectangular parallelepiped shape and extends in the up-down direction Dv.

[0015] In the following description, the depth direction Dd of the rack 11 will be simply referred to as the depth direction Dd, and the width direction Dw of the rack 11 will be simply referred to as the width direction Dw. The depth direction Dd and the width direction Dw are both horizontal directions and are perpendicular to each other. In the following description, the depth direction Dd will be referred to as the horizontal first direction D1, and the width direction Dw will be referred to as the horizontal second direction D2. In other words, the horizontal first direction D1 and the horizontal second direction D2 are perpendicular to each other.

[0016] The rack group 10 is configured by arranging a plurality of racks 11 side by side in a first horizontal direction D1 (depth direction Dd). The rack group 10 is also arranged side by side in a second horizontal direction D2 (width direction Dw).

[0017] As shown in FIG. 4 , the rack 11 accommodates multiple servers 12. The multiple servers 12 are arranged at intervals in the vertical direction Dv within the rack 11. Each server 12 includes a board 13 and a heating element 14. The heating element 14 is a chip such as a CPU or GPU mounted on the board 13. While only one heating element 14 is illustrated on each board 13, multiple heating elements 14 may be provided. For example, multiple heating elements 14 may be provided on each board 13, lined up in the horizontal second direction D2 (width direction Dw). The heating elements 14 generate heat during operation. The heating elements 14 are cooled by a refrigerant R circulating through a refrigerant circulation channel 40, which will be described later. In this embodiment, the refrigerant R is, for example, water. The type of refrigerant R can be changed as appropriate. The refrigerant R may be, for example, a hydrofluoroolefin (HFO) (e.g., R1233zd) having a low global warming potential (GWP) and ozone depletion potential (ODP). Alternatively, the refrigerant R may be a refrigerant that does not fall under the category of perfluoroalkyl substances and polyfluoroalkyl substances (PFAS).

[0018] 4 and 5, the heat exchange unit 20 is provided corresponding to each rack 11. In this embodiment, the heat exchange unit 20 is disposed directly above the rack 11. That is, the heat exchange unit 20 is provided above the rack 11 at a position overlapping with the rack 11 in the up-down direction Dv. The heat exchange unit 20 is provided in a refrigerant circulation flow path 40 (described later), and is supplied with the refrigerant R after cooling the heat-generating element 14. The heat exchange unit 20 is a so-called radiator. The heat exchange unit 20 exchanges heat between the refrigerant R and air A above each rack 11, and dissipates the heat of the refrigerant R.

[0019] The heat exchange unit 20 is formed in a linear shape that extends downward from one side in the horizontal second direction D2 to the other side in the horizontal second direction D2 when viewed from the horizontal first direction D1. The heat exchange unit 20 has a supply header 21 to which the refrigerant R is supplied, a discharge header 22 that discharges the refrigerant R, and a heat dissipation unit 23 that connects the supply header 21 and the discharge header 22.

[0020] The supply header 21 is a tubular member extending in the horizontal first direction D1. The discharge header 22 is provided at a position spaced apart from the supply header 21 on the other side in the horizontal second direction D2 and below the supply header 21. The discharge header 22 is a tubular member extending in the horizontal first direction D1. The discharge header 22 is formed with a smaller diameter than the supply header 21.

[0021] The heat dissipation section 23 is formed in a cylindrical shape extending in the horizontal second direction D2 from the supply header 21 toward the discharge header 22. The heat dissipation section 23 connects the supply header 21 and the discharge header 22. The heat dissipation section 23 is formed so that its diameter gradually decreases toward the discharge header 22. The shape of the heat dissipation section 23 can be modified as appropriate. The heat dissipation section 23 may be formed in a cylindrical or rectangular column shape with a uniform thickness. The heat dissipation section 23 dissipates heat from the refrigerant R to the outside air. Multiple heat dissipation sections 23 are arranged in parallel in the horizontal first direction D1. Each heat dissipation section 23 also has fins 24 formed to protrude in a flange-like shape from its outer circumferential surface. Multiple fins 24 are arranged in parallel in the axial direction of the heat dissipation section 23 (the horizontal second direction D2).

[0022] (Filter) As shown in FIGS. 1 to 3 , the server room 2a is provided with an air inlet 2b for introducing cooling outside air into the server room 2a. The air inlet 2b is provided on one side of the group of servers 12 in the horizontal first direction D1. The air inlet 2b extends in the horizontal second direction D2 and is formed across the entire area of ​​the group of servers 12. The filter 3 is attached within this air inlet 2b. The filter 3 is disposed upstream of the group of racks 10 in the flow direction of air A caused by the intake fan 70. The filter 3 allows air A to flow through it. The filter 3 is provided so as to be detachable and divided into multiple pieces in the horizontal second direction D2. The filter 3 captures dust and other particles contained in the air A.

[0023] (Duct) The duct 30 is provided above a plurality of heat exchange units 20 corresponding to one rack group 10. The duct 30 extends in the horizontal first direction D1 and forms an exhaust flow path S for exhausting the air A that has exchanged heat in each heat exchange unit 20 in the horizontal first direction D1. A plurality of ducts 30 are provided side by side in the horizontal second direction D2. In this embodiment, the same number of ducts 30 as the number of rack groups 10 are provided.

[0024] The duct 30 has an internal duct 31 located within the server center 2 (an example of a building), and an external duct 32 that communicates with the internal duct 31 and has at least a portion located outside the server center 2 (an example of a building).

[0025] The internal duct 31 is supported on the ceiling of the server room 2a by support members (not shown). The internal duct 31 has a horizontal duct 33 extending in a first horizontal direction D1. The horizontal duct 33 forms a horizontal discharge flow path SH of the discharge flow path S that extends in the first horizontal direction D1. The horizontal duct 33 opens downward. Air A that has exchanged heat with the refrigerant R in the heat exchange unit 20 is introduced into the duct 30 from the downward opening of the horizontal duct 33. The horizontal duct 33 has an upper plate 34, side plates 35, end plates 36, and a partition plate 37.

[0026] The upper plate 34 extends along a horizontal plane and in the horizontal first direction D1. The side plates 35 are provided on both ends of the upper plate 34 in the horizontal second direction D2 and extend downward from the upper plate 34. The side plates 35 extend in the horizontal first direction D1. Adjacent ducts 30 share the side plate 35. However, the side plate 35 does not have to be shared by adjacent ducts 30. The side plate 35 may be provided individually for each duct 30.

[0027] The end plate 36 is provided at one end of the upper plate 34 in the horizontal first direction D1. The end plate 36 extends downward from the upper plate 34. The end plate 36 connects the side plates 35 that face each other in the width direction Dw. A plurality of partition plates 37 are provided in the horizontal duct 33 at intervals in the horizontal first direction D1. The partition plates 37 are arranged below the upper plate 34 at intervals, and define horizontal discharge flow paths SH in the horizontal first direction D1. A heat exchange unit 20 is arranged in each of the multiple spaces defined by the multiple partition plates 37. In this embodiment, the entirety of each heat exchange unit 20 is disposed in the horizontal duct 33.

[0028] The external duct 32 extends upward from the other end of the horizontal duct 33 in the horizontal first direction D1. The external duct 32 is formed in a cylindrical shape extending upward along the wall surface of the server center 2. The external duct 32 forms a vertical discharge flow path SV of the discharge flow path S that extends in the up-down direction Dv. The external duct 32 is attached to the wall surface of the server center 2. The upper end of the external duct 32 is curved and opens downward.

[0029] (Support Material) The support material 4 is provided in the duct 30 and connects the heat exchange unit 20 and the duct 30. The support material 4 supports the duct 30 from below. The support material 4 is provided on each of the supply header 21 and the discharge header 22. Hereinafter, the support material 4 provided on the supply header 21 will be referred to as the supply-side support material 4a, and the support material 4 provided on the discharge header 22 will be referred to as the discharge-side support material 4b. The supply-side support material 4a extends from the supply header 21 to one side in the horizontal second direction D2 and is connected to the side plate 35. The discharge-side support material 4b extends from the discharge header 22 to the other side in the horizontal second direction D2 and is connected to the side plate 35.

[0030] (Cooling Component) The cooling component 5 is attached to the heating element 14 and allows the refrigerant R to flow through it. The refrigerant R cools the heating element 14 by exchanging heat with the refrigerant R. The cooling component 5 is, for example, a cold plate, and the refrigerant R is supplied from a refrigerant circulation flow path 40, which will be described later. In the cooling component 5, the refrigerant R boils when exposed to the heat of the heating element 14.

[0031] (Refrigerant Circulation Flow Path) The refrigerant circulation flow path 40 is provided with the heat exchange unit 20 and the cooling component 5, and has a natural circulation flow path 41 that naturally circulates the refrigerant R by thermal convection. The natural circulation flow path 41 has a discharge pipe 42, a first header 43, a supply side connecting pipe 44, a discharge side connecting pipe 45, a second header 46, and a supply pipe 47. A discharge pipe 42 is provided for each cooling component 5. The discharge pipe 42 extends from the top surface of the cooling component 5. The refrigerant R that has exchanged heat with the heating element 14 is discharged from the cooling component 5 to the discharge pipe 42. The multiple discharge pipes 42 are connected to the first header 43.

[0032] The first header 43 joins the refrigerant R flowing through each discharge pipe 42. The first header 43 extends upward. The first header 43 is connected to the supply-side connecting pipe 44. The first header 43 has a flange 43a at its upper end that protrudes radially outward.

[0033] The supply-side connecting pipe 44 extends upward and is connected to the supply header 21 of the heat exchange unit 20. The supply-side connecting pipe 44 has a flange 44a at its lower end that protrudes radially outward. The flange 44a of the supply-side connecting pipe 44 is fixed in an overlapping state to the flange 43a of the first header 43. The refrigerant R flowing through the first header 43 is supplied to the supply header 21 of the heat exchange unit 20 via the supply-side connecting pipe 44. The refrigerant R then dissipates heat in the heat dissipation unit 23 and is sent to the discharge header 22. A discharge-side connecting pipe 45 is provided to the discharge header 22.

[0034] The discharge side connecting pipe 45 extends downward from the discharge header 22. The discharge side connecting pipe 45 has a flange 45a at its lower end that protrudes radially outward. A second header 46 is connected to the discharge side connecting pipe 45.

[0035] The second header 46 extends downward from the discharge side connecting pipe 45. The second header 46 has a flange 46a at its upper end that protrudes radially outward. The flange 45a of the discharge side connecting pipe 45 is fixed in an overlapping state to the flange 46a of the second header 46. The refrigerant R discharged from the discharge header 22 is sent to the second header 46 via the discharge side connecting pipe 45. The second header 46 is provided with supply pipes 47 in the same number as the cooling components 5.

[0036] The supply pipes 47 extend from the second headers 46 and connect the corresponding cooling components 5 to the second headers 46. The supply pipes 47 are connected to the cooling components 5 below the discharge pipes 42. The multiple supply pipes 47 distribute and supply the refrigerant R flowing through the second headers 46 to each cooling component 5.

[0037] (Cooling Mechanism of Heat-Generating Element) Next, the cooling mechanism of the heat-generating element 14 in the server system 1 will be described. When the server 12 is operating and the heat-generating element 14 generates heat, the refrigerant R in the cooling component 5 is heated. The heated refrigerant R has a lower density than the refrigerant R before heating and rises. In this way, the refrigerant R naturally circulates within the refrigerant circulation flow path 40 due to thermal convection caused by the heat of the heat-generating element 14. In this embodiment, the refrigerant R boils and vaporizes within the cooling component 5. The vaporized refrigerant R flows through the discharge pipe 42 into the first header 43. The refrigerant R is then supplied to the heat exchanger 20. In the heat exchanger 20, heat exchange occurs between the refrigerant R and the surrounding air A. As a result, the refrigerant R is cooled and liquefied.

[0038] Meanwhile, the air A around the heat exchange unit 20 is heated. As the air A around the heat exchange unit 20 is heated, an upward flow is generated around the heat exchange unit 20. This upward flow generated around the heat exchange unit 20 causes the air A that has absorbed heat from the refrigerant R in the heat exchange unit 20 to be introduced into the upper duct 30. The air A passes through the exhaust flow path S and is exhausted outside the server center 2 (outside the server room 2a). In this way, the heat of the heating element 14 is discharged outside the server center 2 (outside the server room 2a).

[0039] After being cooled in the heat exchange unit 20, the refrigerant R is supplied in a liquid state to the cooling component 5 through the second header 46 and the supply pipe 47. In the cooling component 5, heat exchange occurs again between the refrigerant R supplied from the supply pipe 47 and the heating elements 14. In this way, the refrigerant R flows through the refrigerant circulation flow path 40 to cool the heating elements 14, and the heat of the heating elements 14 can be discharged outside the server center 2 (outside the server room 2a) through the duct 30.

[0040] (Operational Effects) The server system 1 of this embodiment can exhibit the following operational effects. In this embodiment, the server system 1 includes a rack group 10, a heat exchanger 20, and a duct 30. The rack group 10 is configured by arranging a plurality of racks 11, each accommodating a heat-generating element 14 cooled by a refrigerant R, side by side in a first horizontal direction D1. A heat exchanger 20 is provided corresponding to each rack 11, and exchanges heat between the refrigerant R and air A above each rack 11. The duct 30 forms a discharge flow path S that extends in the first horizontal direction D1 above the heat exchanger units 20 and discharges the air A that has exchanged heat in each heat exchanger unit 20 toward the first horizontal direction D1.

[0041] The heat of the heating element 14 is absorbed by the refrigerant R. The refrigerant R that has absorbed the heat of the heating element 14 is sent to the heat exchange unit 20. The heat exchange unit 20 exchanges heat between the refrigerant R and the air A surrounding the heat exchange unit 20. In this way, the heat of the heating element 14 transferred via the refrigerant R is discharged to the outside air in the heat exchange unit 20. The duct 30 can collectively discharge the air A that has absorbed the exhaust heat from the multiple heat exchange units 20 that belong to the corresponding rack group 10. Therefore, with the above configuration, heat can be discharged efficiently.

[0042] Second Embodiment (Configuration of Server System) A server system 201 according to a second embodiment of the present disclosure will be described below with reference to Figures 6 and 7. Configurations similar to those in the above-described embodiments will be denoted by the same names and reference numerals, and descriptions thereof will be omitted as appropriate. As shown in Figures 6 and 7, the server system 201 includes a support material 4, similar to the server system 1 of the first embodiment.

[0043] (Supporting Materials) Of the supporting materials 4, a plurality of supply-side supporting materials 4 a are provided along the supply header 21, and a plurality of discharge-side supporting materials 4 b are provided along the discharge header 22. In this embodiment, the entire heat exchange unit 20 is disposed within the duct 30.

[0044] Insertion holes 38 into which the support materials 4 are inserted are formed in the side plates 35. Of the insertion holes 38, the insertion holes 38 into which the supply-side support material 4a is inserted are referred to as supply-side insertion holes 38a, and the insertion holes 38 into which the discharge-side support material 4b is inserted are referred to as discharge-side insertion holes 38b. The supply-side insertion holes 38a are provided above the discharge-side insertion holes 38b.

[0045] (Effects) The server system 201 of this embodiment can achieve the following effects. In this embodiment, the server system 201 further includes a support material 4 that connects the heat exchanger 20 and the duct 30. The entire heat exchanger 20 is disposed inside the duct 30. The duct 30 is formed with an insertion hole 38 into which the support material 4 is inserted.

[0046] By simply inserting the support material 4 into the insertion hole 38, at least a portion of the heat exchanger 20 can be easily disposed within the duct 30. This makes it easier for the air A whose heat has been exhausted from the heat exchanger 20 to be guided into the duct 30. Therefore, with the above configuration, heat can be exhausted even more efficiently.

[0047] In the present embodiment, the entire heat exchange unit 20 is disposed inside the duct 30, but this is not limiting. Only a part of the heat exchange unit 20 may be disposed inside the duct 30.

[0048] Third Embodiment (Configuration of Server System) A server system 301 according to a third embodiment of the present disclosure will be described below with reference to FIGS. 8 and 9 . Configurations similar to those in the above-described embodiments will be denoted by the same names and reference numerals, and descriptions thereof will be omitted as appropriate. As shown in FIGS. 8 and 9 , the server system 301 further includes an elastic member 6. The elastic member 6 is disposed within the duct 30. The elastic member 6 is designed to be elastically deformable. Examples of the elastic member 6 include rubber. In this embodiment, the entire heat exchange unit 20 is disposed within the duct 30.

[0049] (Elastic Member) The elastic member 6 is provided to fill the gap between the heat exchange unit 20 and the duct 30. The elastic member 6 is provided on each of the supply header 21 and the discharge header 22. Of the elastic members 6, the elastic member 6 provided on the supply header 21 is referred to as the supply-side elastic member 6a, and the elastic member 6 provided on the discharge header 22 is referred to as the discharge-side elastic member 6b.

[0050] The supply-side elastic member 6a extends in the horizontal first direction D1 along the supply header 21. Both ends of the supply-side elastic member 6a are in close contact with the partition plate 37. The supply-side elastic member 6a is pressed against the outer peripheral surface of the supply header 21 and the side plate 35 of the duct 30, and is in close contact with the side plate 35 of the duct 30 and the outer peripheral surface of the supply header 21. The discharge-side elastic member 6b extends in the horizontal first direction D1 along the discharge header 22. Both ends of the discharge-side elastic member 6b are in close contact with the partition plate 37. The discharge-side elastic member 6b is pressed against the outer peripheral surface of the discharge header 22 and the side plate 35 of the duct 30, and is in close contact with the side plate 35 of the duct 30 and the outer peripheral surface of the discharge header 22.

[0051] (Effects) The server system 301 of this embodiment can achieve the following effects.

[0052] In this embodiment, the server system 301 is further provided with an elastically deformable elastic member 6 that is disposed within the duct 30. The entire heat exchange unit 20 is disposed within the duct 30. The elastic member 6 is provided so as to fill the gap between the heat exchange unit 20 and the duct 30.

[0053] By disposing the elastic member 6 in close contact with the heat exchanger 20 and the duct 30, it is possible to prevent the air A whose heat has been discharged from the heat exchanger 20 from leaking out of the duct 30. Therefore, with the above-described configuration, it is possible to discharge heat more efficiently.

[0054] In the present embodiment, the entire heat exchange unit 20 is disposed inside the duct 30, but this is not limiting. Only a part of the heat exchange unit 20 may be disposed inside the duct 30.

[0055] In the present embodiment, the elastic members 6 are provided at both ends of the heat exchange unit 20 in the second horizontal direction D2 (width direction Dw), but this is not limiting. The elastic members 6 may be provided so as to cover the entire periphery of the heat exchange unit 20 in the horizontal direction.

[0056] Fourth Embodiment (Configuration of Server System) A server system 401 according to a fourth embodiment of the present disclosure will be described below with reference to FIG. 10 . Components similar to those in the above-described embodiments are designated by the same names and reference numerals, and descriptions thereof will be omitted as appropriate. Note that FIG. 10 illustrates only one of the ducts 30 constituting one group of ducts 30. Also, only one of the rack groups 10 is illustrated as a representative, and only one of the racks 11 constituting one rack group 10 is illustrated as a representative. While only one heating element 14 is illustrated on each board 13, multiple heating elements 14 are provided on each board 13 at the same height in the horizontal second direction D2 (width direction Dw). Multiple cooling components 5 are attached to each heating element 14 and provided at the same height in the horizontal second direction D2 (width direction Dw). Note that the number of heating elements 14 and cooling components 5 can be changed as appropriate. For example, each board 13 may be provided with only one heating element 14 and one cooling component 5. As shown in FIG.

[0057] The second duct 39 is provided so as to be connectable to the horizontal duct 33 from below. The second duct 39 is in communication with the horizontal duct 33. The second duct 39 is formed in a rectangular cylindrical shape extending in the up-down direction Dv.

[0058] The heat exchanger 20 is surrounded by a second duct 39. The heat exchanger 20 is provided integrally with the second duct 39. The heat exchanger 20 and the second duct 39 are connected by, for example, a support material 4. The support material 4 is provided so as to fill the gap between the heat exchanger 20 and the second duct 39. The gap between the heat exchanger 20 and the second duct 39 may be filled by, for example, the elastic member 6 described above. Hereinafter, the integrated heat exchanger 20 and the second duct 39 will be referred to as a heat exchange unit U. In this embodiment, the supply-side connecting pipe 44 and the discharge-side connecting pipe 45 are included in the heat exchanger unit U.

[0059] The heat exchange unit 20 and the second duct 39 integrated together (heat exchange unit U) is provided directly above the rack 11. That is, the heat exchange unit 20 and the second duct 39 integrated together (heat exchange unit U) is provided above the rack 11 at a position overlapping with the rack 11 in the up-down direction Dv.

[0060] In this embodiment, the first header 43 and the second header 46 are housed in the rack 11. The first header 43 extends in the vertical direction Dv. The upper end of the first header 43 protrudes above the rack 11. The upper end of the second header 46 protrudes above the rack 11. Both the first header 43 and the second header 46 are supported on the rack 11 by support members (not shown).

[0061] The heat exchange unit U is placed on the upper ends of the first header 43 and the second header 46. The flange 44a of the supply side connecting pipe 44 is fixed to the flange 43a of the first header 43, and the flange 45a of the discharge side connecting pipe 45 is fixed to the flange 46a of the second header 46. In this manner, the heat exchange unit U is fixed to the first header 43 and the second header 46.

[0062] In this embodiment, the server system 401 further includes a refrigerant pump 7 and a switching mechanism 60. In addition to the natural circulation flow path 41 described above, the refrigerant circulation flow path 40 includes a branching portion 48 and a forced circulation flow path 49. The branching portion 48 is provided at the upstream end of the natural circulation flow path 41.

[0063] (Forced Circulation Flow Path) The forced circulation flow path 49 branches off from the branching portion 48 and is provided to bypass a portion of the natural circulation flow path 41. The upstream end of the forced circulation flow path 49 is connected to the branching portion 48, and the downstream end of the forced circulation flow path 49 is connected to the downstream end of the second header 46. The forced circulation flow path 49 is provided with a refrigerant pump 7. The refrigerant pump 7 pumps the refrigerant R. The forced circulation flow path 49 forcibly circulates the refrigerant R without relying on thermal convection by the pumping force of the refrigerant pump 7. Note that the power for the forced circulation flow path 49 to forcibly circulate the refrigerant R without relying on thermal convection may be supplied from a power source other than the refrigerant pump 7.

[0064] (Switching Mechanism) The switching mechanism 60 is provided in the refrigerant circulation flow path 40. The switching mechanism 60 is capable of switching the flow path of the refrigerant R between a flow path in which the refrigerant R passes through the forced circulation flow path 49 and a flow path in which the refrigerant R does not pass through the forced circulation flow path 49.

[0065] The switching mechanism 60 of this embodiment has a first valve 61 and a second valve 62. The first valve 61 is provided in the second header 46 downstream of the branching portion 48 and upstream of all of the supply pipes 47. The second valve 62 is provided in the forced circulation flow path 49 downstream of the branching portion 48.

[0066] By opening the first valve 61 and closing the second valve 62, the flow path of the refrigerant R can be a flow path in which the refrigerant R does not pass through the forced circulation flow path 49 (natural circulation). On the other hand, by closing the first valve 61 and opening the second valve 62, the flow path of the refrigerant R can be a flow path in which the refrigerant R passes through the forced circulation flow path 49 (forced circulation). By driving the refrigerant pump 7 in this state, the refrigerant R can be forced to circulate.

[0067] (Effects) The server system 401 of this embodiment can achieve the following effects. In this embodiment, the duct 30 has a horizontal duct 33 and a second duct 39. The horizontal duct 33 extends in the horizontal first direction D1. The second duct 39 is connectable to the horizontal duct 33 from below and communicates with the horizontal duct 33. The heat exchanger 20 is surrounded by the second duct 39 and is provided integrally with the second duct 39. The integrated body of the heat exchanger 20 and the second duct 39 (heat exchange unit U) is provided above the rack 11 in a position overlapping with the rack 11 in the up-down direction Dv.

[0068] The load of the heat exchange unit 20 can be directly borne by the rack 11. This improves stability. Furthermore, the heat exchange unit 20, the second duct 39, and the rack 11 can be assembled as a set, which makes installation easier.

[0069] In this embodiment, the server system 401 includes a cooling component 5, a refrigerant pump 7, a refrigerant circulation channel 40, and a switching mechanism 60. The cooling component 5 is attached to the heat generating element 14 and allows refrigerant R to flow therethrough, cooling the heat generating element 14 by exchanging heat with the refrigerant R. The refrigerant pump 7 pumps the refrigerant R. The refrigerant circulation channel 40 has a natural circulation channel 41 and a forced circulation channel 49. The natural circulation channel 41 is provided with the heat exchanger 20 and the cooling component 5, and causes the refrigerant R to circulate naturally by thermal convection. The forced circulation channel 49 bypasses a portion of the natural circulation channel 41. The refrigerant pump 7 is provided in the forced circulation channel 49. The forced circulation channel 49 forcibly circulates the refrigerant R by the pumping force of the refrigerant pump 7, without relying on thermal convection. The switching mechanism 60 is provided in the refrigerant circulation channel 40. The switching mechanism 60 can switch the flow path of the refrigerant R between a flow path in which the refrigerant R passes through the forced circulation flow path 49 and a flow path in which the refrigerant R does not pass through the forced circulation flow path 49 .

[0070] When the amount of heat generated is small, the flow path of the refrigerant R can be switched to a flow path in which the refrigerant R does not pass through the forced circulation flow path 49, thereby allowing the refrigerant R to circulate naturally only by thermal convection due to the heat of the heating element 14. When the amount of heat generated is large, the flow path of the refrigerant R can be switched to a flow path in which the refrigerant R passes through the forced circulation flow path 49, thereby allowing the refrigerant R to circulate forcibly without relying on thermal convection. This allows the refrigerant R to circulate smoothly, thereby improving the cooling capacity.

[0071] In this way, depending on the amount of heat generated, the circulation of the refrigerant R can be switched between natural circulation using only thermal convection and forced circulation using the refrigerant pump 7 without using thermal convection. This makes it possible to efficiently cool the heat generating element 14.

[0072] Fifth Embodiment (Configuration of Server System) A server system 501 according to a fifth embodiment of the present disclosure will be described below with reference to FIGS. 11 and 12 . Components similar to those in the above-described embodiments are designated by the same names and reference numerals, and descriptions thereof will be omitted as appropriate. Note that FIG. 11 illustrates only one of the ducts 30 constituting one group of ducts 30. Also, only one of the rack groups 10 is illustrated as a representative, and only one of the racks 11 constituting one rack group 10 is illustrated as a representative. While only one heating element 14 is illustrated on each board 13, multiple heating elements 14 are provided on each board 13 at the same height in the horizontal second direction D2 (width direction Dw). Multiple cooling components 5 are attached to each heating element 14 and provided at the same height in the horizontal second direction D2 (width direction Dw). Note that the number of heating elements 14 and cooling components 5 can be changed as appropriate. For example, each board 13 may be provided with only one heating element 14 and one cooling component 5. Also in this embodiment, the heat exchange unit 20 and the second duct 39 are connected by, for example, the support material 4. The support material 4 is provided so as to fill the gap between the heat exchange unit 20 and the second duct 39. The gap between the heat exchange unit 20 and the second duct 39 may also be filled by, for example, the elastic member 6 described above. As shown in Figures 11 and 12, the refrigerant circulation channel 40 has the natural circulation channel 41 described above, the forced circulation channel 49, and the refrigerant cooling channel 50.

[0073] (Refrigerant Cooling Flow Path) The refrigerant cooling flow path 50 branches off from the forced circulation flow path 49 and bypasses a portion of the natural circulation flow path 41. The upstream end of the refrigerant cooling flow path 50 is connected to the forced circulation flow path 49 between the second valve 62 and the refrigerant pump 7, and the downstream end of the refrigerant cooling flow path 50 is connected to the downstream end of the first header 43. The refrigerant cooling flow path 50 is provided with a refrigerant cooler 9, which will be described later. The server system 501 also includes an air-cooled fan 8, a refrigerant cooler 9, and a second refrigerant pump 56.

[0074] (Air-cooling fan) The air-cooling fan 8 blows air onto the heat exchanger 20 to cool it. The air-cooling fan 8 is disposed above the heat exchanger 20 in the second duct 39. The air-cooling fan 8 is desirably provided in a position close to the heat dissipation section 23 of the heat exchanger 20. The air-cooling fan 8 draws in air A from below and blows it toward the horizontal duct 33 above.

[0075] (Refrigerant Cooler) The refrigerant cooler 9 is provided in the refrigerant cooling flow path 50. The refrigerant cooler 9 is disposed below the refrigerant pump 7. In addition to the refrigerant R circulating through the refrigerant circulation flow path 40, the refrigerant cooler 9 is supplied with a second refrigerant R2 supplied from a second refrigerant flow path 55 separate from the refrigerant circulation flow path 40. The refrigerant cooler 9 cools the refrigerant R by exchanging heat with the second refrigerant R2. The second refrigerant R2 is, for example, water. Note that the second refrigerant R2 is not limited to water and can be selected as appropriate. In addition, the second refrigerant flow path 55 is provided with a second refrigerant pump 56 that pumps the second refrigerant R2.

[0076] (Switching mechanism) The switching mechanism 60 can switch the flow path of the refrigerant R between a flow path in which the refrigerant R passes through the forced circulation flow path 49 and a flow path in which the refrigerant R does not pass through the forced circulation flow path 49. Furthermore, the switching mechanism 60 can switch the flow path of the refrigerant R between a flow path in which the refrigerant R passes through the refrigerant cooling flow path 50 and a flow path in which the refrigerant R does not pass through the refrigerant cooling flow path 50.

[0077] The switching mechanism 60 of this embodiment has a first valve 61, a second valve 62, a third valve 63, and a fourth valve 64. The third valve 63 is provided upstream of the refrigerant cooling flow path 50. The fourth valve 64 is provided downstream of the first header 43 in the natural circulation flow path 41. The fourth valve 64 is provided downstream of all of the discharge pipes 42 in the first header 43. In this embodiment, by switching the first valve 61, the second valve 62, the third valve 63, and the fourth valve 64, the flow path of the refrigerant R can be selectively switched depending on the heat generation amount.

[0078] An example of switching the circulation of the refrigerant R will be described below with reference to Figure 12. When the heat generation amount per heating element 14 (hereinafter referred to as heating element heat generation amount) is between 0 W and 500 W (first heating element threshold) and the total heat generation amount per rack 11 (hereinafter referred to as total heat generation amount) is between 0 kW and 15 kW (first rack threshold) (first condition C1), the first valve 61 and the fourth valve 64 are opened, and the second valve 62 and the third valve 63 are closed. In this case, the refrigerant R can be naturally circulated only by thermal convection caused by the heat of the heating elements 14.

[0079] When the heat generation amount of the heating elements is between 500 W (first heating element threshold) and 1500 W (second heating element threshold) and the total heat generation amount is between 0 kW and 15 kW (first rack threshold) (second condition C2), the second valve 62 and the fourth valve 64 are opened, and the first valve 61 and the third valve 63 are closed. In this state, the refrigerant pump 7 is driven. This causes the refrigerant pump 7 to pump the refrigerant R, forcing it to circulate.

[0080] When the heat generation amount of the heat generating elements is between 0 W and 500 W (first heat generating element threshold) and the total heat generation amount is between 15 kW (first rack threshold) and 50 kW (second rack threshold) (third condition C3), the first valve 61 and the fourth valve 64 are opened, and the second valve 62 and the third valve 63 are closed. Furthermore, the air-cooling fan 8 is driven. This allows the refrigerant R to be cooled by the air-cooling fan 8 while naturally circulating solely by thermal convection caused by the heat of the heat generating elements 14.

[0081] When the heat generation amount of the heat generating elements is between 500 W (first heat generating element threshold) and 1500 W (second heat generating element threshold) and the total heat generation amount is between 15 kW (first rack threshold) and 50 kW (second rack threshold) (fourth condition C4), the second valve 62 and the fourth valve 64 are opened, and the first valve 61 and the third valve 63 are closed. In this state, the refrigerant pump 7 is driven. Furthermore, the air-cooled fan 8 is driven. As a result, the refrigerant R is pressurized by the refrigerant pump 7, forcibly circulating the refrigerant R, while the air-cooled fan 8 cools the refrigerant R.

[0082] When the heat generation amount of the heat generating element is between 0 W and 1500 W (second heat generating element threshold) and the total heat generation amount per rack 11 is between 50 kW (second rack threshold) and 100 kW (third rack threshold) (fifth condition C5), the first valve 61, the second valve 62, and the fourth valve 64 are closed, and the third valve 63 is opened. In this state, the refrigerant pump 7 and the second refrigerant pump 56 are driven. This allows the refrigerant R to be pressurized by the refrigerant pump 7, forcibly circulating the refrigerant R, while the refrigerant R is cooled by the second refrigerant R2.

[0083] Although specific values ​​are shown as examples for the first and second heating element thresholds and the first to third rack thresholds, they are not limited to these. The first and second heating element thresholds and the first to third rack thresholds can be changed as appropriate. For example, the first rack threshold may be 12 kW, and the second rack threshold may be 25 kW.

[0084] (Effects) The server system 501 of this embodiment can achieve the following effects. In this embodiment, the server system 501 further includes a cooling component 5, an air-cooled fan 8, a refrigerant pump 7, a refrigerant cooler 9, a refrigerant circulation channel 40, and a switching mechanism 60. The cooling component 5 is attached to the heat-generating element 14, allows refrigerant R to flow through, and cools the heat-generating element 14 by heat exchange with the refrigerant R. The refrigerant pump 7 pressurizes the refrigerant R. The air-cooled fan 8 blows air through the heat exchange unit 20 to cool the heat exchange unit 20. The refrigerant cooler 9 cools the refrigerant R by heat exchange with the second refrigerant R2. The refrigerant circulation channel 40 includes a natural circulation channel 41, a forced circulation channel 49, and a refrigerant cooling channel 50. The heat exchange unit 20 and the cooling component 5 are provided in the natural circulation channel 41, and the natural circulation channel 41 naturally circulates the refrigerant R by thermal convection. The forced circulation flow path 49 bypasses a portion of the natural circulation flow path 41, and is provided with a refrigerant pump 7. The forced circulation flow path 49 forcibly circulates the refrigerant R by the pumping force of the refrigerant pump 7 without relying on thermal convection. The refrigerant cooling flow path 50 bypasses a portion of the natural circulation flow path 41, and is provided with a refrigerant cooler 9. The switching mechanism 60 can switch the flow path of the refrigerant R between a flow path in which the refrigerant R includes the forced circulation flow path 49 and a flow path in which the refrigerant R does not include the forced circulation flow path 49. Furthermore, the switching mechanism 60 can switch the flow path of the refrigerant R between a flow path in which the refrigerant R passes through the refrigerant cooling flow path 50 and a flow path in which the refrigerant R does not pass through the refrigerant cooling flow path 50.

[0085] When the heat generation amount is small, the flow path of the refrigerant R can be switched to a flow path in which the refrigerant R does not pass through the forced circulation flow path 49 and the refrigerant cooler 9, allowing the refrigerant R to circulate naturally only through thermal convection caused by the heat of the heating element 14. When the heat generation amount is large, the flow path of the refrigerant R can be switched to a flow path in which the refrigerant R passes through the forced circulation flow path 49 and the refrigerant pump 7 is driven, allowing the refrigerant R to be forcedly circulated without relying on thermal convection. This allows the refrigerant R to circulate smoothly, improving cooling capacity. Driving the air-cooling fan 8 also air-cools the heat exchange unit 20, improving cooling capacity. Switching the flow path of the refrigerant R to a flow path in which the refrigerant R passes through the refrigerant cooling flow path 50 and driving the refrigerant cooler 9 cools the refrigerant R, improving cooling capacity. Note that the power for the forced circulation flow path 49 to forcibly circulate the refrigerant R without relying on thermal convection may be supplied from a power source other than the refrigerant pump 7. In this way, it is possible to appropriately switch between an operation using natural circulation of the refrigerant R, an operation in which the refrigerant R is forcibly circulated without relying on thermal convection, and an operation in which the cooling capacity is improved by driving the air-cooling fan 8 and the refrigerant cooler 9. Furthermore, it is possible to appropriately combine an operation in which the refrigerant R is forcibly circulated without relying on thermal convection with the driving of the air-cooling fan 8 and the refrigerant cooler 9. Thus, according to this embodiment, the cooling capacity can be adjusted according to the amount of heat generated.

[0086] Sixth Embodiment (Configuration of Server System) A server system 601 according to a sixth embodiment of the present disclosure will be described below with reference to FIG. 13 . Components similar to those in the previously described embodiments are designated by the same names and reference numerals, and descriptions thereof will be omitted as appropriate. As shown in FIG. 13 , the server system 601 includes an intake fan 70 and a filter 3. The intake fan 70 generates a flow of air A in a horizontal first direction D1 and introduces the air A into the rack group 10. The intake fan 70 is provided for each rack group 10, and is provided on one side of each rack group 10 in the horizontal first direction D1. The filter 3 is disposed upstream of the rack group 10 in the flow direction of the air A caused by the intake fan 70. The filter 3 allows the air A to flow through. The filter 3 captures dust and other particles contained in the air A.

[0087] (Effects) The server system 601 of this embodiment can achieve the following effects. In this embodiment, the server system 601 further includes an introduction fan 70 and a filter 3. The introduction fan 70 generates a flow of air A in the horizontal first direction D1 and introduces the air A into the rack group 10. The filter 3 is disposed upstream of the rack group 10 in the flow direction of the air A caused by the introduction fan 70.

[0088] The filter 3 can remove dust particles and the like from the air A supplied to the rack 11. Furthermore, the intake fan 70 can compensate for the pressure loss of the air A passing through the filter 3. This makes it possible to effectively introduce the air A into the rack group 10. Therefore, with the above configuration, heat can be discharged even more efficiently.

[0089] Seventh Embodiment (Configuration of Server System) A server system 701 according to a seventh embodiment of the present disclosure will be described below with reference to FIG. 14 . Components similar to those in the above-described embodiments are designated by the same names and reference numerals, and descriptions thereof will be omitted as appropriate. Note that FIG. 14 representatively illustrates only one of the ducts 30 constituting one group of ducts 30. Also, only some of the rack groups 10 are representatively illustrated, and only one of the racks 11 constituting one rack group 10 is representatively illustrated. While only one heating element 14 is illustrated on each board 13, multiple heating elements 14 are provided on each board 13 at the same height in the horizontal first direction D1 (depth direction Dd). Multiple cooling components 5 are attached to each heating element 14 and provided at the same height in the horizontal first direction D1 (depth direction Dd). Note that the number of heating elements 14 and cooling components 5 can be changed as appropriate. For example, each board 13 may be provided with only one heating element 14 and one cooling component 5. As shown in Fig. 14, a pair of heat exchange units 20 are provided for each corresponding rack 11. The two heat exchange units 20 constituting a pair are arranged in a V-shape when viewed from the horizontal first direction D1 so that the discharge header 22 is positioned below the supply header 21. In this embodiment, the pair of two heat exchange units 20 arranged in a V-shape is provided directly above the rack 11.

[0090] The supply-side connecting pipes 44 extend downward from each of the two supply headers 21 and merge with the first header 43. The discharge-side connecting pipes 45 extend downward from each of the two discharge headers 22 and merge with the second header 46.

[0091] (Effects) The server system 701 of this embodiment can achieve the following effects. In this embodiment, the heat exchange units 20 are provided in pairs for each corresponding rack 11. The two heat exchange units 20 constituting one pair are arranged in a V-shape when viewed from the first horizontal direction D1 so that the discharge header 22 is positioned below the supply header 21.

[0092] This improves the heat exchange efficiency per rack 11. Therefore, with the above configuration, heat can be discharged more efficiently.

[0093] In the above embodiment, each of the two heat exchange units 20 has a discharge header 22, but this is not limited to this. The two heat exchange units 20 may share one discharge header 22.

[0094] Eighth Embodiment (Configuration of Server System) A server system 801 according to an eighth embodiment of the present disclosure will be described below with reference to FIG. 15 . Components similar to those in the above-described embodiments are designated by the same names and reference numerals, and descriptions thereof will be omitted as appropriate. Note that FIG. 15 representatively illustrates only one of the ducts 30 constituting one group of ducts 30. Also, only some of the rack groups 10 are representatively illustrated, and only one of the racks 11 constituting one rack group 10 is representatively illustrated. While only one heating element 14 is illustrated on each board 13, multiple heating elements 14 are provided on each board 13 at the same height in the horizontal first direction D1 (depth direction Dd). Multiple cooling components 5 are attached to each heating element 14 and provided at the same height in the horizontal first direction D1 (depth direction Dd). Note that the number of heating elements 14 and cooling components 5 can be changed as appropriate. For example, each board 13 may be provided with only one heating element 14 and one cooling component 5. As shown in Fig. 15 , the two heat exchange units 20 arranged in a V-shape extend in the horizontal second direction D2 from near one end of the corresponding rack 11 in the horizontal second direction D2 to near one end of the adjacent rack 11 in the horizontal second direction D2 from the other side of the corresponding rack 11 in the horizontal second direction D2.

[0095] In this embodiment, of the two heat exchange units 20 arranged in a V-shape, the heat exchange unit 20 on one side in the horizontal second direction D2 is arranged directly above the rack 11, and the heat exchange unit 20 on the other side in the horizontal second direction D2 is arranged directly above the aisle between the racks 11.

[0096] Also in this embodiment, similarly to the seventh embodiment, the supply-side connecting pipes 44 extend downward from each of the two supply headers 21 and merge with the first header 43. Furthermore, the discharge-side connecting pipes 45 extend downward from each of the two discharge headers 22 and merge with the second header 46.

[0097] (Effects) The server system 801 of this embodiment can achieve the following effects: In this embodiment, the two heat exchange units 20 arranged in a V-shape extend in the horizontal second direction D2 from near one end of the corresponding rack 11 in the horizontal second direction D2 to near one end of the adjacent rack 11 in the horizontal second direction D2 from the other side of the corresponding rack 11 in the horizontal second direction D2.

[0098] This allows the heat exchange unit 20 to be longer in the horizontal second direction D2, thereby further improving the heat exchange efficiency per rack 11. Therefore, with the above configuration, heat can be discharged more efficiently.

[0099] Ninth Embodiment (Configuration of Server System) A server system 901 according to a ninth embodiment of the present disclosure will be described below with reference to FIG. 16 . Components similar to those in the above-described embodiments are designated by the same names and reference numerals, and descriptions thereof will be omitted as appropriate. Note that FIG. 16 representatively illustrates only one of the ducts 30 constituting one group of ducts 30. Also, only some of the rack groups 10 are representatively illustrated, and only one of the racks 11 constituting one rack group 10 is representatively illustrated. While only one heating element 14 is illustrated on each board 13, multiple heating elements 14 are provided on each board 13 at the same height in the horizontal first direction D1 (depth direction Dd). Multiple cooling components 5 are attached to each heating element 14 and provided at the same height in the horizontal first direction D1 (depth direction Dd). Note that the number of heating elements 14 and cooling components 5 can be changed as appropriate. For example, each board 13 may be provided with only one heating element 14 and one cooling component 5. As shown in Fig. 16, a hot line HL or a cool line CL is provided between adjacent rack groups 10 in the horizontal second direction D2. The hot lines HL and the cool lines CL are provided alternately. The hot lines HL and the cool lines CL extend in the horizontal first direction D1 along the rack groups 10. A duct 30 is provided above each hot line HL.

[0100] In this embodiment, the heat exchange units 20 are provided in pairs above each hot line HL and below each duct 30. The two heat exchange units 20 constituting one pair are arranged in a V-shape when viewed from the horizontal first direction D1 so that the discharge header 22 is positioned below the supply header 21.

[0101] The supply-side connecting pipes 44 extend downward from each of the two supply headers 21. The discharge-side connecting pipes 45 extend downward from each of the two discharge headers 22.

[0102] The supply-side connecting pipe 44 belonging to the heat exchanger 20 on one side in the horizontal second direction D2 merges with the first header 43 belonging to the rack 11 on one side in the horizontal second direction D2. The supply-side connecting pipe 44 belonging to the heat exchanger 20 on the other side in the horizontal second direction D2 merges with the first header 43 belonging to the rack 11 on the other side in the horizontal second direction D2. Furthermore, the discharge-side connecting pipe 45 belonging to the heat exchanger 20 on one side in the horizontal second direction D2 merges with the second header 46 belonging to the rack 11 on one side in the horizontal second direction D2. The discharge-side connecting pipe 45 belonging to the heat exchanger 20 on the other side in the horizontal second direction D2 merges with the second header 46 belonging to the rack 11 on the other side in the horizontal second direction D2.

[0103] (Cooling Fan) The server system 901 further includes a cooling fan 75. The cooling fan 75 is provided in each rack 11 to supply air A to the heat generating element 14 and exhaust the air A that has passed through the heat generating element 14 to the outside of the rack 11. The cooling fan 75 is a fan for cooling the heat generating element 14, such as a CPU or GPU, that is pre-installed in the server 12. The cooling fan 75 is provided, for example, so as to sandwich the heat generating element 14 in the horizontal second direction D2. The cooling fan 75 blows air A from the cool line CL to the hot line HL. Air A is blown into the hot line HL from both sides in the horizontal second direction D2, and the air A is guided to the duct 30 above. The duct 30 then exhausts the air A exhausted from the rack 11 through the exhaust flow path S in the horizontal first direction D1.

[0104] (Effects) The server system 901 of this embodiment can achieve the following effects. In this embodiment, the server system 901 further includes a cooling fan 75 that is provided in each rack 11 and supplies air A to the heating elements 14 and exhausts the air A that has passed through the heating elements 14 to the outside of the rack 11. The duct 30 exhausts the air A exhausted from the rack 11 in the first horizontal direction D1 through the exhaust flow path S.

[0105] This allows the air A to be supplied to the heat exchange section 20 as well by utilizing the cooling fan 75 provided to directly cool the heat generating element 14 .

[0106] Tenth Embodiment (Configuration of Server System) A server system 1001 according to a tenth embodiment of the present disclosure will be described below with reference to FIG. 17 . Configurations similar to those of the above-described embodiments will be denoted by the same names and reference numerals, and descriptions thereof will be omitted as appropriate. As shown in FIG. 17 , a plurality of server centers 2 (an example of a building) (for example, two in the illustrated example) are provided. The external duct 32 belonging to one server center 2 is disposed opposite the external duct 32 belonging to another server center 2 in the horizontal first direction D1. The number of server centers 2 can be changed as appropriate.

[0107] (Effects) The server system 1001 of this embodiment can achieve the following effects: In this embodiment, the external duct 32 belonging to one server center 2 is arranged opposite the external duct 32 belonging to another server center 2.

[0108] As a result, a portion of the external duct 32 is shielded by the server center 2. Therefore, it is possible to prevent an object heading toward the server center 2 from colliding with the external duct 32.

[0109] Eleventh Embodiment (Configuration of Server System) A server system 1101 according to an eleventh embodiment of the present disclosure will be described below with reference to FIG. 18 . Configurations similar to those of the above-described embodiments will be denoted by the same names and reference numerals, and descriptions thereof will be omitted as appropriate. As shown in FIG. 18 , multiple server centers 2 (an example of a building) are provided. In the illustrated example, four server centers 2 are provided in a ring shape. The number of server centers 2 can be changed as appropriate.

[0110] The external ducts 32 belonging to each server center 2 are provided in the gap between adjacent server centers 2. Specifically, the external ducts 32 belonging to one server center 2 (hereinafter referred to as the first server center 2) are exposed to the outside of the first server center 2 from an end portion on the other side of the first server center 2 in the horizontal first direction D1. Furthermore, the external ducts 32 belonging to the first server center 2 face an end portion on one side of the horizontal first direction D1 of another server center 2 (hereinafter referred to as the second server center 2) located on the other side of the first server center 2 in the horizontal first direction D1. The multiple server centers 2 are arranged in a ring shape, with the arrangement of the first server center 2 and the second server center 2 repeated.

[0111] (Operational Effects) The server system 1101 of this embodiment can achieve the following operational effects: In this embodiment, the external duct 32 belonging to each server center 2 is provided in the gap between adjacent server centers 2 .

[0112] As a result, a portion of the external duct 32 is shielded by the building, which prevents an object heading toward the building from colliding with the external duct 32.

[0113] (Other Embodiments) Although the embodiments of the present disclosure have been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope of the gist of the present disclosure. Note that, in the above embodiment, the rack 11 is formed in a rectangular parallelepiped shape, but this is not limiting. The shape of the rack 11 can be changed as appropriate.

[0114] In the above embodiment, the first horizontal direction D1 and the second horizontal direction D2 are perpendicular to each other, but this is not limiting. The angle formed between the first horizontal direction D1 and the second horizontal direction D2 may be greater than or less than 90 degrees.

[0115] In the above embodiment, the depth direction Dd of the rack 11 is the horizontal first direction D1, the width direction Dw of the rack 11 is the horizontal second direction D2, and the duct 30 extends in the depth direction Dd of the rack 11, but this is not limited to this. The depth direction Dd of the rack 11 may be the horizontal second direction D2, the width direction Dw of the rack 11 is the horizontal first direction D1, and the duct 30 may extend in the width direction Dw of the rack 11.

[0116] In the above embodiment, the heat exchanger 20 includes the supply header 21, the discharge header 22, and the heat dissipation section 23. However, the configuration of the heat exchanger 20 is not limited to this. The configuration of the heat exchanger 20 can be changed as appropriate.

[0117] For example, in the first embodiment and other embodiments described above, the number of ducts 30 provided is the same as the number of rack groups 10, but this is not limited to this. The number of ducts 30 provided can be changed as appropriate. For example, one duct 30 extending in the horizontal second direction D2 may cover multiple rack groups 10 (for example, all of the rack groups 10).

[0118] In the above embodiment, the air A is introduced into the duct 30 from the downward opening of the horizontal duct 33, but this is not limited to this. The position of the opening through which the air A is introduced into the horizontal duct 33 may be changed as appropriate. For example, an opening may be formed in the end plate 36 or the side plate 35 of the horizontal duct 33.

[0119] In the above embodiment, the refrigerant R boils and vaporizes in the cooling component 5, but this is not limiting. The refrigerant R may circulate through the refrigerant circulation flow path 40 as a liquid without boiling in the cooling component 5.

[0120] In the above embodiment, the server center 2 is used as an example of a building, but the building is not limited to this. The building may be a server room 2a in the server center 2.

[0121] <Additional Notes> The server systems 1, 201, 301, 401, 501, 601, 701, 801, 901, 1001, and 1101 described in the respective embodiments can be understood, for example, as follows.

[0122] (1) The server systems 1, 201, 301, 401, 501, 601, 701, 801, 901, 1001, and 1101 according to the first aspect include a group of racks 10 each configured by arranging a plurality of racks 11 in a horizontal first direction D1, each rack 11 housing a heat generating element 14 cooled by a refrigerant R, a heat exchange unit 20 arranged corresponding to each rack 11 and performing heat exchange between the refrigerant R and air A above each rack 11, and a duct 30 extending in the horizontal first direction D1 above the plurality of heat exchange units 20 to form an exhaust flow path S for discharging the air A that has undergone heat exchange in each heat exchange unit 20 toward the horizontal first direction D1.

[0123] The heat of the heating elements 14 is absorbed by the refrigerant R. The refrigerant R that has absorbed the heat of the heating elements 14 is sent to the heat exchange unit 20. The heat exchange unit 20 exchanges heat between the refrigerant R and the air A surrounding the heat exchange unit 20. In this way, the heat of the heating elements 14 that has been transferred via the refrigerant R is discharged to the outside air in the heat exchange unit 20. The duct 30 can collectively discharge the air A that has absorbed the exhaust heat from the multiple heat exchange units 20 that belong to the corresponding rack group 10.

[0124] (2) The server system 201 of the second aspect is the server system 201 of (1), further comprising a support material 4 connecting the heat exchange unit 20 and the duct 30, wherein at least a portion of the heat exchange unit 20 is disposed within the duct 30, and the duct 30 may have an insertion hole 38 formed therein into which the support material 4 is inserted.

[0125] By simply inserting the support material 4 into the insertion hole 38, at least a portion of the heat exchange unit 20 can be easily disposed within the duct 30. This makes it easier for the air A that has lost heat from the heat exchange unit 20 to be guided into the duct 30.

[0126] (3) The server system 301 of a third aspect is the server system 301 of (1) or (2), further including an elastic member 6 that is disposed in the duct 30 and is elastically deformable, wherein at least a portion of the heat exchange unit 20 is disposed in the duct 30, and the elastic member 6 may be provided so as to fill a gap between the heat exchange unit 20 and the duct 30. An example of the elastic member 6 is a rubber material.

[0127] By disposing the elastic member 6 in close contact with the heat exchanger 20 and the duct 30 , it is possible to prevent the air A whose heat has been exhausted from the heat exchanger 20 from leaking out of the duct 30 .

[0128] (4) A fourth aspect of the server system 401 is a server system 401 of any one of (1) to (3), wherein the duct 30 has a horizontal duct 33 extending in the horizontal first direction D1 and a second duct 39 that is connectable to the horizontal duct 33 from below and communicates with the horizontal duct 33, the heat exchange unit 20 is surrounded by the second duct 39 and is formed integrally with the second duct 39, and the integrated unit of the heat exchange unit 20 and the second duct 39 may be formed above the rack 11 in a position that overlaps with the rack 11 in the vertical direction Dv.

[0129] The load of the heat exchanger 20 can be directly borne by the rack 11 side.

[0130] (5) The server system 401 of the fifth aspect may be any one of the server systems 401 of (1) to (4), and may further include: a cooling component 5 that is attached to the heat generating element 14, allows the refrigerant R to flow through, and cools the heat generating element 14 by exchanging heat with the refrigerant R; a refrigerant circulation flow path 40 that is provided with the heat exchange unit 20 and the cooling component 5 and has: a natural circulation flow path 41 that naturally circulates the refrigerant R by thermal convection; and a forced circulation flow path 49 that bypasses a portion of the natural circulation flow path 41 and forcibly circulates the refrigerant R without relying on thermal convection; and a switching mechanism 60 that is provided in the refrigerant circulation flow path 40 and can switch the flow path of the refrigerant R between a flow path through which the refrigerant R passes through the forced circulation flow path 49 and a flow path through which the refrigerant R does not pass through the forced circulation flow path 49.

[0131] When the amount of heat generated is small, the flow path of the refrigerant R can be switched to a flow path in which the refrigerant R does not pass through the forced circulation flow path 49, thereby allowing the refrigerant R to circulate naturally only by thermal convection due to the heat of the heating element 14. When the amount of heat generated is large, the flow path of the refrigerant R can be switched to a flow path in which the refrigerant R passes through the forced circulation flow path 49, thereby allowing the refrigerant R to circulate forcibly without relying on thermal convection. This allows the refrigerant R to circulate smoothly, thereby improving the cooling capacity.

[0132] (6) A server system 501 of a sixth aspect is the server system 501 of any one of (1) to (4), and further includes a cooling component 5 that is attached to the heat generating element 14 and allows the refrigerant R to flow therethrough and cools the heat generating element 14 by heat exchange with the refrigerant R, an air-cooling fan 8 that blows air to the heat exchange unit 20 to cool the heat exchange unit 20, a refrigerant cooler 9 that cools the refrigerant R by heat exchange with a second refrigerant R2, the heat exchange unit 20 and the cooling component 5 are provided with a natural circulation flow path 41 that naturally circulates the refrigerant R by thermal convection, and a cooling element 5 that bypasses a part of the natural circulation flow path 41 and cools the refrigerant R by heat exchange with a second refrigerant R2. The system may further include a refrigerant circulation flow path (40) having a forced circulation flow path (49) that forcibly circulates the refrigerant without relying on convection, and a refrigerant cooling flow path (50) that bypasses a portion of the natural circulation flow path (41) and is provided with the refrigerant cooler (9); and a switching mechanism (60) that is provided in the refrigerant circulation flow path (40) and is capable of switching the flow path of the refrigerant R between a flow path in which the refrigerant R passes through the forced circulation flow path (49) and a flow path in which the refrigerant R does not pass through the forced circulation flow path (49), and is capable of switching the flow path of the refrigerant R between a flow path in which the refrigerant R passes through the refrigerant cooling flow path (50) and a flow path in which the refrigerant R does not pass through the refrigerant cooling flow path (50).

[0133] When the heat generation amount is small, the flow path of the refrigerant R can be switched to a flow path in which the refrigerant R does not pass through the forced circulation flow path 49 and the refrigerant cooler 9, allowing the refrigerant R to circulate naturally only through thermal convection caused by the heat of the heating element 14. When the heat generation amount is large, the flow path of the refrigerant R can be switched to a flow path in which the refrigerant R passes through the forced circulation flow path 49, allowing the refrigerant R to circulate forcibly without relying on thermal convection. This allows the refrigerant R to circulate smoothly, improving cooling capacity. Furthermore, by driving the air-cooling fan 8, the heat exchange unit 20 can be air-cooled, improving cooling capacity. Furthermore, by switching the flow path of the refrigerant R to a flow path in which the refrigerant R passes through the refrigerant cooling flow path 50 and driving the refrigerant cooler 9, the refrigerant R can be cooled, improving cooling capacity. In this way, it is possible to appropriately switch between operation by natural circulation of the refrigerant R, operation in which the refrigerant R is forcedly circulated without relying on thermal convection, and operation in which the air-cooling fan 8 and the refrigerant cooler 9 are driven. Furthermore, the operation of forcibly circulating the refrigerant R without relying on thermal convection and the driving of the air-cooling fan 8 and the refrigerant cooler 9 can be appropriately combined.

[0134] (7) The server system 601 of the seventh aspect may be any one of the server systems 601 of (1) to (6), and may further include an intake fan 70 that generates a flow of air A in the horizontal first direction D1 and introduces the air A into the rack group 10, and a filter 3 that is arranged upstream of the rack group 10 in the flow direction of the air A caused by the intake fan 70 and allows the air A to flow through.

[0135] The filter 3 can remove dust particles and the like from the air A supplied to the rack 11. Furthermore, the intake fan 70 can compensate for the pressure loss of the air A passing through the filter 3. Therefore, the air A can be efficiently introduced into the rack group 10.

[0136] (8) The server system 701 of the eighth aspect is any one of the server systems 701 of (1) to (7), in which the heat exchange units 20 are provided in pairs for each corresponding rack 11, and the heat exchange units 20 have a supply header 21 to which the refrigerant R is supplied, a discharge header 22 that discharges the refrigerant R, and a heat dissipation unit 23 that connects the supply header 21 and the discharge header 22 and dissipates the heat of the refrigerant R to the outside air, and the two heat exchange units 20 that make up the pair may each be arranged in a V-shape when viewed from the horizontal first direction D1 so that the discharge header 22 is positioned lower than the supply header 21.

[0137] This makes it possible to improve the heat exchange efficiency per rack 11 .

[0138] (9) A ninth aspect of the server system 801 is the server system 801 of (8), in which the rack group 10 is arranged in a row in a horizontal second direction D2 that intersects the horizontal first direction D1, and the two heat exchange units 20 arranged in a V-shape may extend in the horizontal second direction D2 from near one end of the corresponding rack 11 in the horizontal second direction D2 to near one end of the adjacent rack 11 in the horizontal second direction D2 from the other side of the corresponding rack 11 in the horizontal second direction D2.

[0139] This allows the heat exchange section 20 to be longer in the horizontal second direction D2, thereby further improving the heat exchange efficiency per rack 11.

[0140] (10) The server system 901 of the tenth aspect is any one of the server systems 901 of (1) to (9), and further includes a cooling fan 75 provided in each of the racks 11 to supply air A to the heating element 14 and discharge the air A that has passed through the heating element 14 outside the rack 11, and the discharge flow path S of the duct 30 may discharge the air A discharged from the rack 11 by the cooling fan 75 toward the horizontal first direction D1.

[0141] This allows the air A to be supplied to the heat exchange section 20 as well by utilizing the cooling fan 75 provided to directly cool the heat generating element 14 .

[0142] (11) A server system 501 according to an eleventh aspect includes racks 11 accommodating heat-generating elements 14 cooled by a refrigerant R, heat exchange units 20 provided corresponding to the racks 11 and configured to exchange heat between the refrigerant R and air A above the racks 11, a duct 30 configured to form an exhaust flow path S above the heat exchange units 20 for discharging the air A that has undergone heat exchange in the heat exchange units 20, a cooling component 5 attached to the heat-generating elements 14 and allowing the refrigerant R to flow therethrough, and cooling the heat-generating elements 14 by heat exchange with the refrigerant R, an air-cooling fan 8 configured to blow air to the heat exchange units 20 to cool the heat exchange units 20, a refrigerant cooler 9 configured to exchange heat between the refrigerant R and a second refrigerant R2 for cooling, and the heat exchange units 20 and the cooling component 5. a refrigerant circulation flow path (40) having a natural circulation flow path (41) that is provided in the refrigerant circulation flow path (40) and that allows the refrigerant R to circulate naturally by thermal convection, a forced circulation flow path (49) that bypasses a portion of the natural circulation flow path (41) and allows the refrigerant R to forcibly circulate without relying on thermal convection, and a refrigerant cooling flow path (50) that bypasses a portion of the natural circulation flow path (41) and is provided with the refrigerant cooler (9); and a switching mechanism (60) that is provided in the refrigerant circulation flow path (40) and is capable of switching the flow path of the refrigerant R between a flow path in which the refrigerant R passes through the forced circulation flow path (49) and a flow path in which the refrigerant R does not pass through the forced circulation flow path (49), and is also capable of switching the flow path of the refrigerant R between a flow path in which the refrigerant R passes through the refrigerant cooling flow path (50) and a flow path in which the refrigerant R does not pass through the refrigerant cooling flow path (50).

[0143] (12) A server system 901 according to the twelfth aspect includes a group of racks 10 configured by arranging a plurality of racks 11, each housing a heating element 14, in a horizontal first direction D1, a cooling fan 75 provided in each of the racks 11 to supply air A to the heating element 14 and discharge the air A that has passed through the heating element 14 outside the rack 11, and a duct 30 extending in the horizontal first direction D1 above the group of racks 10 to form a discharge flow path S for discharging the air A discharged from the rack 11 by the cooling fan 75 toward the horizontal first direction D1.

[0144] (13) The server system 1001 of a thirteenth aspect is the server system 1001 of any one of (1) to (12), further including a building that houses the duct 30, the duct 30 having an internal duct 31 arranged within the building and an external duct 32 that communicates with the internal duct 31 and has at least a portion arranged outside the building, and a plurality of the buildings may be provided, and the external duct 32 belonging to one of the buildings may be arranged opposite the external duct 32 belonging to another of the buildings. Examples of the building include a server center 2 and a server room 2a.

[0145] As a result, a portion of the external duct 32 is shielded by the building, which prevents an object heading toward the building from colliding with the external duct 32.

[0146] (14) A server system 1101 of a fourteenth aspect is the server system 1101 of any one of (1) to (12), further including a building that houses the duct 30, the duct 30 having an internal duct 31 arranged within the building and an external duct 32 that communicates with the internal duct 31 and has at least a portion arranged outside the building, the server system 1101 may include a plurality of buildings, and the external duct 32 belonging to each building may be arranged in a gap between adjacent buildings. Examples of the building include a server center 2 and a server room 2a.

[0147] As a result, a portion of the external duct 32 is shielded by the building, which prevents an object heading toward the building from colliding with the external duct 32.

[0148] The server system of the present disclosure can efficiently exhaust heat and adjust the cooling capacity according to the amount of heat generated.

[0149] REFERENCE SIGNS LIST 1...Server system 2...Server center (building) 2a...Server room 2b...Air inlet 3...Filter 4...Support material 4a...Supply side support material 4b...Discharge side support material 5...Cooling component 6...Elastic member 6a...Supply side elastic member 6b...Discharge side elastic member 7...Refrigerant pump 8...Air-cooled fan 9...Refrigerant cooler 10...Rack group 11...Rack 12...Server 13...Board 14...Heat generating element 20...Heat exchange section 21...Supply header 22...Discharge header 23...Heat dissipation section 24...Fin 30...Duct 31...Internal duct 32...External duct 33...Horizontal duct 34...Upper plate 35...Side plate 36...End plate 36...Partition plate 38...Insertion hole 38a...Supply side insertion hole 38b...Discharge side insertion hole 39...Second duct 40...Refrigerant circulation flow path DESCRIPTION OF SYMBOLS 41...Natural circulation flow path 42...Discharge pipe 43...First header 43a...Flange 44...Supply side connecting pipe 44a...Flange 45...Discharge side connecting pipe 45a...Flange 46...Second header 46a...Flange 47...Supply pipe 48...Branch portion 49...Forced circulation flow path 50...Refrigerant cooling flow path 55...Second refrigerant flow path 56...Second refrigerant pump 60...Switching mechanism 61...First valve 62...Second valve 63...Third valve 64...Fourth valve 70...Inlet fan 75...Cooling fan 201...Server system 301...Server system 401...Server system 501...Server system 601...Server system 701...Server system 801...Server system 901...Server system 1001...Server system 1101...Server system A...Air Dv...Vertical direction Dd...Depth direction Dw: Width direction D1: First horizontal direction D2: Second horizontal direction HL: Hot line CL: Cool line R: Refrigerant R2: Second refrigerant S: Discharge flow path SH: Horizontal discharge flow path SV: Vertical discharge flow path U: Heat exchange unit

Claims

1. A server system comprising: a group of racks arranged in a first horizontal direction, each rack housing a heat generating element cooled by a refrigerant; a heat exchange unit provided corresponding to each of the racks and exchanging heat between the refrigerant and air above each of the racks; and a duct extending in the first horizontal direction above the heat exchange units to form an exhaust flow path for discharging air that has been heat exchanged in each of the heat exchange units, toward the first horizontal direction.

2. The server system according to claim 1, further comprising a support material connecting the heat exchange unit and the duct, at least a portion of the heat exchange unit being disposed within the duct, and an insertion hole into which the support material is inserted being formed in the duct.

3. The server system according to claim 1 or 2, further comprising an elastic member disposed within the duct and capable of elastic deformation, at least a portion of the heat exchange unit being disposed within the duct, and the elastic member being arranged to fill a gap between the heat exchange unit and the duct.

4. A server system as described in claim 1 or 2, wherein the duct comprises a horizontal duct extending in the first horizontal direction, and a second duct that is connectable to the horizontal duct from below and communicates with the horizontal duct, the heat exchange unit is surrounded by the second duct and is integral with the second duct, and the integrated unit of the heat exchange unit and the second duct is provided above the rack in a position that overlaps with the rack in the vertical direction.

5. A server system as described in claim 1 or 2, further comprising: a cooling component attached to the heat generating element and allowing the refrigerant to flow therethrough, for cooling the heat generating element by exchanging heat with the refrigerant; a refrigerant circulation flow path in which the heat exchange unit and the cooling component are provided, the refrigerant having a natural circulation flow path for naturally circulating the refrigerant by thermal convection, and a forced circulation flow path that bypasses a portion of the natural circulation flow path and forcibly circulates the refrigerant without relying on thermal convection; and a switching mechanism provided in the refrigerant circulation flow path, capable of switching the flow path of the refrigerant between a flow path in which the refrigerant passes through the forced circulation flow path and a flow path in which the refrigerant does not pass through the forced circulation flow path.

6. A server system as claimed in claim 1 or 2, further comprising: a cooling component attached to the heat generating element, allowing the refrigerant to flow therethrough, and cooling the heat generating element by heat exchange with the refrigerant; an air-cooled fan that blows air through the heat exchanging section to cool the heat exchanging section; a refrigerant cooler that cools the refrigerant by heat exchange with a second refrigerant; a refrigerant circulation flow path in which the heat exchanging section and the cooling component are provided, the refrigerant having: a natural circulation flow path that naturally circulates the refrigerant by thermal convection, a forced circulation flow path that bypasses a portion of the natural circulation flow path and forcibly circulates the refrigerant without using thermal convection, and a refrigerant cooling flow path that bypasses a portion of the natural circulation flow path and is provided with the refrigerant cooler; and a switching mechanism that is provided in the refrigerant circulation flow path and is capable of switching the flow path of the refrigerant between a flow path in which the refrigerant passes through the forced circulation flow path and a flow path in which the refrigerant does not pass through the forced circulation flow path, and is capable of switching the flow path of the refrigerant between a flow path in which the refrigerant passes through the refrigerant cooling flow path and a flow path in which the refrigerant does not pass through the refrigerant cooling flow path.

7. The server system according to claim 1 or 2, further comprising: an intake fan that generates an air flow in the first horizontal direction and introduces air into the group of racks; and a filter through which air can flow, the filter being positioned upstream of the group of racks in the direction of the air flow caused by the intake fan.

8. A server system as described in claim 1 or 2, wherein the heat exchange units are provided in a set of two for each corresponding rack, the heat exchange units having: a supply header to which the refrigerant is supplied, a discharge header which discharges the refrigerant, and a heat dissipation unit which connects the supply header and the discharge header and dissipates heat of the refrigerant to the outside air, and the two heat exchange units constituting the set are each arranged in a V shape when viewed from the first horizontal direction so that the discharge header is located lower than the supply header.

9. The server system described in claim 8, wherein the rack group is arranged in a row in a horizontal second direction intersecting the horizontal first direction, and the two heat exchange units arranged in a V-shape extend in the horizontal second direction from near one end of the corresponding rack in the horizontal second direction to near one end of the rack adjacent to the corresponding rack from the other side of the horizontal second direction in the horizontal second direction.

10. A server system as described in claim 1 or 2, further comprising a cooling fan provided in each of the racks to supply air to the heat generating element and exhaust air that has passed through the heat generating element outside the rack, and the exhaust flow path of the duct exhausts the air exhausted from the rack by the cooling fan in the first horizontal direction.

11. A refrigerant circulation flow path having: a rack for accommodating a heat generating element to be cooled by a refrigerant; a heat exchange unit provided corresponding to said rack and for exchanging heat between said refrigerant and air above said rack; a duct above said heat exchange unit forming an exhaust flow path for discharging air that has undergone heat exchange in said heat exchange unit; a cooling component attached to said heat generating element and allowing said refrigerant to flow therethrough and for cooling said heat generating element by heat exchange with said refrigerant; an air-cooled fan for blowing air to said heat exchange unit to cool said heat exchange unit; a refrigerant cooler for cooling said refrigerant by heat exchange with a second refrigerant; a switching mechanism that is provided in the refrigerant circulation flow path and is capable of switching the flow path of the refrigerant between a flow path in which the refrigerant passes through the forced circulation flow path and a flow path in which the refrigerant does not pass through the forced circulation flow path, and is also capable of switching the flow path of the refrigerant between a flow path in which the refrigerant passes through the refrigerant cooling flow path and a flow path in which the refrigerant does not pass through the refrigerant cooling flow path.

12. A server system comprising: a group of racks configured by arranging multiple racks in a horizontal first direction, each rack housing a heat generating element; a cooling fan provided in each of the racks for supplying air to the heat generating element and discharging air that has passed through the heat generating element outside the rack; and a duct extending in the horizontal first direction above the group of racks and forming an exhaust flow path for discharging air exhausted from the rack by the cooling fan toward the horizontal first direction.

13. A server system as described in any one of claims 1, 11 and 12, further comprising a building in which the duct is housed, the duct having an internal duct arranged within the building, and an external duct communicating with the internal duct and at least a portion of which is arranged outside the building, wherein a plurality of the buildings are provided, and the external duct belonging to one of the buildings is arranged opposite the external duct belonging to the other of the buildings.

14. A server system as described in any one of claims 1, 11 and 12, further comprising a building in which the duct is housed, the duct having an internal duct arranged within the building, and an external duct communicating with the internal duct and at least a portion of which is arranged outside the building, wherein a plurality of the buildings are provided, and the external duct belonging to each of the buildings is provided in the gap between adjacent buildings.

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