Cooling system

Abstract

To provide a cooling system capable of improving cooling efficiency.SOLUTION: A cooling system includes: a cooling unit having a plurality of cooling devices for cooling a heat-generating element, an intake port-side header for distributing a refrigerant to the cooling devices, and a discharge port-side header through which the refrigerant is discharged from each cooling device; a natural circulation unit having a natural circulation line which connects the discharge port-side header and the intake port-side header, and a first heat exchanger installed above the cooling unit partway along the natural circulation line; and a forced circulation unit having a forced circulation line which connects the discharge port-side header and the intake port-side header, a second heat exchanger which is provided partway along the forced circulation line and has a larger capacity than the first heat exchanger, and a pump which is provided in the forced circulation line and pumps the refrigerant from the discharge port-side header toward the intake port-side header.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to cooling systems. [Background technology]

[0002] For example, electronic devices such as computers and servers installed in a server room generate heat during operation. In order to cool such heat-generating devices, a cooling system such as that shown in Patent Document 1 has been devised. The cooling system of Patent Document 1 has two circulation mechanisms between an evaporator and a condenser: a natural circulation mechanism and a forced circulation mechanism for the refrigerant. These two circulation mechanisms can be switched between. The natural circulation mechanism uses heat generated by the heat-generating device to circulate the refrigerant naturally. In contrast, the forced circulation mechanism uses a pump to forcefully circulate the refrigerant. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-190553 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the cooling system described in Patent Document 1, a single condenser is used in common for both the natural circulation mechanism and the forced circulation mechanism to cool the refrigerant after heat exchange with the heat generating body. Therefore, when the cooling capacity of the condenser is insufficient for the amount of heat generated, the cooling efficiency of the heat generating body may decrease even if the natural circulation mechanism is switched to the forced circulation mechanism.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a cooling system capable of improving cooling efficiency. [Means for solving the problem]

[0006] In order to solve the above problems, the cooling system of the present disclosure comprises a cooling unit having a plurality of cooling devices that cool a heat generating element, an inlet side header that distributes refrigerant to the cooling devices, and an outlet side header through which the refrigerant is discharged from each of the cooling devices, a natural circulation section having a natural circulation line connecting the outlet side header and the inlet side header and a first heat exchanger installed midway on the natural circulation line and above the cooling units, a forced circulation line connecting the outlet side header and the inlet side header, a second heat exchanger installed midway on the forced circulation line and having a larger capacity than the first heat exchanger, and a forced circulation section installed in the forced circulation line and having a pump that pressure-feeds the refrigerant from the outlet side header toward the inlet side header.

[0007] The cooling system according to the present disclosure comprises a cooling unit having a plurality of cooling devices that cool a heat generating element, an inlet side header that distributes a refrigerant to the cooling devices, and an outlet side header through which the refrigerant is discharged from each of the cooling devices, a natural circulation section having a natural circulation line connecting the outlet side header and the inlet side header, and a first heat exchanger installed midway along the natural circulation line and above the cooling units, a forced circulation line connecting the natural circulation line downstream of the first heat exchanger and the inlet side header, and a forced circulation section provided in the forced circulation line and having a pump that pressure-feeds the refrigerant from the outlet side header to the inlet side header, wherein the natural circulation line is disposed above the plurality of cooling devices and has an introduction line that introduces the refrigerant that has undergone heat exchange in the first heat exchanger into the inlet side header, and the pump is disposed below the plurality of cooling devices.

[0008] The cooling system of the present disclosure comprises a cooling unit having a plurality of cooling devices that cool heat-generating elements, an inlet side header that distributes refrigerant to the cooling devices, and an outlet side header through which the refrigerant is discharged from each of the cooling devices, a natural circulation section having a natural circulation line connecting the outlet side header and the inlet side header and a first heat exchanger installed midway along the natural circulation line and above the cooling units, and a duct disposed above the first heat exchanger and extending in the vertical direction with an exhaust flow path therein that exhausts air from below upward. Effect of the Invention

[0009] According to the cooling system of the present disclosure, the cooling efficiency can be improved. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a cooling system according to a first embodiment of the present disclosure. [Diagram 2] 1 is a system diagram showing an overall configuration of a cooling system according to a first embodiment of the present disclosure. [Diagram 3] FIG. 2 is a perspective view of a first heat exchanger according to the first embodiment of the present disclosure. [Figure 4] FIG. 2 is a functional block diagram of a control unit according to the first embodiment of the present disclosure. [Diagram 5] FIG. 2 is a diagram showing a state in which a refrigerant circulation system according to the first embodiment of the present disclosure is switched to a natural circulation line. [Figure 6] 5 is a flowchart showing a procedure for switching a refrigerant distribution system according to the first embodiment of the present disclosure. [Figure 7] FIG. 4 is a diagram showing a state in which a refrigerant distribution system according to the first embodiment of the present disclosure is switched to a forced circulation line. [Figure 8] FIG. 2 is a system diagram showing an overall configuration of a cooling system according to a first modified example of the first embodiment of the present disclosure. [Figure 9] FIG. 11 is a perspective view of a first heat exchanger according to a second modified example of the first embodiment of the present disclosure. [Figure 10]FIG. 11 is a diagram showing a first heat exchanger according to a second modified example of the first embodiment of the present disclosure, as viewed from above. [Figure 11] FIG. 6 is a system diagram showing an overall configuration of a cooling system according to a second embodiment of the present disclosure. [Figure 12] FIG. 11 is a functional block diagram of a control unit according to a second embodiment of the present disclosure. [Figure 13] 10 is a flowchart showing a procedure for switching a refrigerant distribution system according to a second embodiment of the present disclosure. [Figure 14] FIG. 11 is a system diagram showing an overall configuration of a cooling system according to a first modified example of the second embodiment of the present disclosure. [Figure 15] FIG. 11 is a system diagram showing an overall configuration of a cooling system according to a second modified example of the second embodiment of the present disclosure. [Figure 16] FIG. 11 is a system diagram showing an overall configuration of a cooling system according to a third embodiment of the present disclosure. [Figure 17] FIG. 11 is a perspective view of a first heat exchanger according to a third embodiment of the present disclosure. [Figure 18] FIG. 2 is a hardware configuration diagram according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] First Embodiment (Cooling system configuration) Hereinafter, a cooling system 1 according to an embodiment of the present disclosure will be described with reference to FIGS. As shown in Figures 1 and 2, the cooling system 1 includes a server rack 2, a server 3, a cooling unit 10, a natural circulation section 20, a forced circulation section 30, a switching section 40, a reservoir section 50, a duct 60, a sensor 4, and a control unit 70. 1 and 2, each component of the cooling system 1 is illustrated in a schematic manner. Also, some components, such as piping through which a refrigerant R flows and a server rack 2, which will be described later, are omitted in FIGS. In the following description, the vertical up-down direction may be simply referred to as the "up-down direction Dv." The upper side is marked with the symbol "Dvu," and the lower side is marked with the symbol "Dvd."

[0012] (Server rack) The server rack 2 is a housing extending in the vertical direction Dv. The server rack 2 is installed in, for example, a data center. The server rack 2 can accommodate multiple servers 3 therein. In addition, other devices can be placed on a top plate 2a of the server rack 2.

[0013] (server) A plurality of servers 3 are accommodated in the server rack 2 and arranged in the vertical direction Dv. The server 3 includes a casing 3a, a server board 3b, and a heating element 3c. The casing 3a is a box-shaped housing extending horizontally. The casing 3a is inserted horizontally into the server rack 2. The casing 3a accommodates a server board 3b and a heating element 3c. The server board 3b extends horizontally.

[0014] (heating element) The heating element 3c is an electronic component mounted on the server board 3b. The heating element 3c is, for example, a chip such as a CPU or GPU mounted on the server board 3b. A plurality of heating elements 3c are provided on the server board 3b, extending in the horizontal direction. For simplification, FIG. 2 illustrates a case in which one heating element 3c is provided on each server board 3b. The number of heating elements 3c provided on one server board 3b can be changed as appropriate. These heating elements 3c generate heat during operation. The heating elements 3c have a temperature range in which they can operate most efficiently. The cooling system 1 cools each heating element 3c to the temperature range in which they can operate most efficiently.

[0015] (Cooling unit) The cooling unit 10 includes a cooling device 11 , an inlet side header 12 , an inlet side branch line 13 , a valve 14 , an outlet side header 15 , and an outlet side branch line 16 .

[0016] (cooling device) A plurality of cooling devices 11 are provided. The number of cooling devices 11 can be changed as appropriate. The cooling devices 11 are attached to the plurality of heat generating bodies 3c, respectively. The plurality of cooling devices 11 cool the attached heat generating bodies 3c. A refrigerant R is supplied to the cooling devices 11. Examples of the refrigerant R include refrigerants of HFC (Hydro Fluoro Carbon) and HFO (Hydro Fluoro Olefin) systems. A flow path through which the refrigerant R flows is formed inside the cooling device 11. The cooling device 11 cools the heat generating body 3c by exchanging heat between the refrigerant R flowing inside and the heat generating body 3c. The cooling device 11 of this embodiment is a box-shaped cold plate 11a formed so that the refrigerant R can flow inside.

[0017] (Inlet header) The inlet side header 12 distributes the refrigerant R to each cooling device 11. The inlet side header 12 extends in the vertical direction Dv. The inlet side header 12 is provided with a plurality of inlet side branch lines 13 for each cooling device 11. Each inlet side branch line 13 connects the inlet side header 12 to the cooling device 11. The branch line guides the refrigerant R distributed by the inlet side header 12 to the cooling device 11. In addition, each inlet side branch line 13 is provided with a valve 14. This valve 14 is, for example, a needle valve, and can open and close the inlet side branch line 13.

[0018] (Outlet header) The refrigerant R is discharged from each cooling device 11 to the outlet side header 15. The outlet side header 15 extends in the vertical direction Dv. The outlet side header 15 is provided with a plurality of outlet side branch lines 16 for each cooling device 11. Each outlet side branch line 16 connects the outlet side header 15 to each cooling device 11. The refrigerant R heated by heat exchange with the heating element 3c in each cooling device 11 merges in the outlet side header 15 via the outlet side branch lines 16.

[0019] (Natural Circulation Department) The natural circulation section 20 naturally circulates the refrigerant R by utilizing an upward flow generated by heating the refrigerant R with exhaust heat from the heating element 3c. The natural circulation section 20 has a natural circulation line 21, a first heat exchanger 22, a blower fan 23, and a relief valve 24. The natural circulation line 21 connects the outlet side header 15 and the inlet side header 12. The first heat exchanger 22 is installed midway along the natural circulation line 21 and above the cooling unit 10. Each component of the natural circulation section 20 will be described in detail below.

[0020] (Natural circulation line) The natural circulation line 21 has a first natural circulation line 21a, a second natural circulation line 21b, and an introduction line 21c. The first natural circulation line 21a connects the upper end of the outlet side header 15 and the first heat exchanger 22. The first natural circulation line 21a guides the refrigerant R from the outlet side header 15 to the first heat exchanger 22. In the first heat exchanger 22, heat exchange of the refrigerant R is performed. The second natural circulation line 21b extends downward from the first heat exchanger 22 and is connected to a tank 34 of the forced circulation section 30 described later.

[0021] (Introduction line) The introduction line 21c is a bypass line that bypasses the second natural circulation line 21b. The introduction line 21c is disposed above the multiple cooling devices 11. The refrigerant R that has undergone heat exchange in the first heat exchanger 22 is supplied to the introduction line 21c via the second natural circulation line 21b. The introduction line 21c introduces the refrigerant R that has undergone heat exchange in the first heat exchanger 22 into the inlet header 12.

[0022] (1st heat exchanger) The first heat exchanger 22 cools the refrigerant R that has exchanged heat with the heat generating element 3c in the cooling device 11. A flow path through which the refrigerant R can flow is formed inside the first heat exchanger 22. A blower fan 23 is installed near the first heat exchanger 22. The blower fan 23 blows air toward the first heat exchanger 22 and supplies air A to the first heat exchanger 22. The first heat exchanger 22 is an air-cooled radiator 25 that cools the refrigerant R by exchanging heat between the air A around the first heat exchanger 22 and the refrigerant R. The radiator 25 has a gap through which the air A can pass, for example.

[0023] As shown in FIG. 3, two first heat exchangers 22 are placed on the top plate 2a of the server rack 2. Each first heat exchanger 22 is formed in a flat plate shape. The first heat exchanger 22 has a supply section 25a to which the refrigerant R is supplied from the outlet side header 15, and a discharge section 25b that discharges the refrigerant R toward the inlet side header 12. The first heat exchanger 22 is installed at an incline with respect to the horizontal plane HL so that the supply section 25a is located above the discharge section 25b. More specifically, the two first heat exchangers 22 are arranged at an incline in a V-shape when viewed from the horizontal direction.

[0024] In addition, the first heat exchanger 22 is provided with a relief valve 24 for releasing gas inside the first heat exchanger 22 so that pressure exceeding the design pressure is not applied thereto.

[0025] (forced circulation section) The forced circulation unit 30 is provided separately from the natural circulation unit 20, and is a mechanism for circulating the refrigerant R without relying on heating of the refrigerant R by exhaust heat from the heating element 3c. The forced circulation unit 30 has a forced circulation line 31, a separate CDU (Coolant Distribution Unit) 32, a chiller device 33, a tank 34, and a pump 35. The forced circulation line 31 connects the outlet side header 15 and the inlet side header 12. The separate CDU 32 has a second heat exchanger 36, which is provided midway along the forced circulation line 31. The tank 34 and the pump 35 are provided downstream of the second heat exchanger 36 on the forced circulation line 31. Each component of the forced circulation unit 30 will be described in detail below.

[0026] (Forced circulation line) The forced circulation line 31 has a first forced circulation line 31a, a second forced circulation line 31b, and a third forced circulation line 31c. The first forced circulation line 31a connects the lower end of the outlet header 15 and the second heat exchanger 36. The first forced circulation line 31a guides the refrigerant R from the outlet header 15 to the second heat exchanger 36 described later. In the second heat exchanger 36, heat exchange of the refrigerant R is performed. The second forced circulation line 31b connects the second heat exchanger 36 and a tank 34 described later. The second forced circulation line 31b guides the refrigerant R that has undergone heat exchange in the second heat exchanger 36 to the tank 34. The refrigerant R is temporarily stored in the tank 34. The third forced circulation line 31c connects the tank 34 and the lower end of the inlet header 12. The third forced circulation line 31c guides the refrigerant R supplied to the tank 34 to the inlet header 12.

[0027] The third forced circulation line 31c has a plurality of pump lines 37 in which pumps 35 are arranged, and a junction line 38 in which the plurality of pump lines 37 join together. In this embodiment, two pump lines 37 are provided. Only one pump line 37 may be provided, or three or more pump lines 37 may be provided. Each pump line 37 extends from the tank 34 and is connected to one junction line 38. The junction line 38 connects the plurality of pump lines 37 to a lower end of the inlet header 12.

[0028] (Separate CDU) The separate CDU 32 is provided separately from the first heat exchanger 22, and is a mechanism for exchanging heat with the heating element 3c to cool the heated refrigerant R. The separate CDU 32 has a second heat exchanger 36 inside.

[0029] (Second heat exchanger) The second heat exchanger 36 is disposed on the lower Dvd with respect to the cooling unit 10. In particular, in this embodiment, the second heat exchanger 36 is disposed below the cooling unit 10. Note that the lower Dvd with respect to the cooling unit 10 is not limited to the case where it is disposed below the cooling unit 10, but also includes the case where it is disposed at approximately the same height in the up-down direction Dv as the lower part of the cooling unit 10.

[0030] The second heat exchanger 36 is supplied with the refrigerant R from the heating element 3c via the first forced circulation line 31a. The second heat exchanger 36 cools the refrigerant R by causing the refrigerant R to exchange heat. The second heat exchanger 36 has a larger capacity than the first heat exchanger 22. The second heat exchanger 36 of the present embodiment is a water-cooled plate-type heat exchanger that cools the refrigerant R by causing the refrigerant R to exchange heat with the cooling water W flowing inside.

[0031] The second heat exchanger 36 has a plurality of water-cooled plates 36a and valves 36b that are provided on the upstream side and downstream side of each water-cooled plate 36a and can block the flow of the refrigerant R. The plurality of water-cooled plates 36a are connected in parallel. The plurality of water-cooled plates 36a may be connected in series. The refrigerant R is supplied to the plurality of water-cooled plates 36a via the first forced circulation line 31a, and cooling water W is supplied from the outside. Each water-cooled plate 36a exchanges heat between the refrigerant R and the cooling water W. As a result, the refrigerant R is cooled, and the cooling water W is heated by the exhaust heat of the refrigerant R. The heated cooling water W is sent to the chiller device 33.

[0032] (Chiller unit) The chiller device 33 cools the refrigerant R that has undergone heat exchange in the second heat exchanger 36. The refrigerant R cooled in the chiller device 33 is supplied again to the second heat exchanger 36 and performs heat exchange with the refrigerant R.

[0033] (pump) The pump 35 pumps the refrigerant R from the outlet header 15 to the inlet header 12. The refrigerant R pumped by the pump 35 is distributed to each cooling device 11 from the inlet head and circulates in the cooling system 1. One pump 35 is provided for each pump line 37. In this embodiment, two pumps 35 are provided for one cooling unit 10. These two pumps 35 are provided below the cooling devices 11. For example, as shown in the figure, the pump 35 is accommodated in the lowest space in the server rack 2. The pump 35 in this embodiment is a geared pump that sucks in and pumps the refrigerant R by rotating an internal gear. The pump 35 may be a pump of another type, such as a screw pump.

[0034] (Switching section) The switching unit 40 is a mechanism that switches the circulation system 6 of the refrigerant R to at least one of the natural circulation line 21 and the forced circulation line 31. The circulation system 6 of the refrigerant R means a flow path through which the refrigerant R flows. This circulation system 6 includes the natural circulation line 21 and the forced circulation line 31. In other words, the switching unit 40 can switch so that the refrigerant R can flow through either the natural circulation line 21 or the forced circulation line 31, or through both the natural circulation line 21 and the forced circulation line 31.

[0035] The switching unit 40 includes a first switching valve 41, a second switching valve 42, a third switching valve 43, a fourth switching valve 44, a fifth switching valve 45, and a sixth switching valve 46. The first switching valve 41 is provided in the first natural circulation line 21a. The first switching valve 41 opens and closes the first natural circulation line 21a. The second switching valve 42 is provided at the lower end of the second natural circulation line 21b. The second switching valve 42 is located near the tank 34. The second switching valve 42 opens and closes the second natural circulation line 21b. The third switching valve 43 is provided in the introduction line 21c. The third switching valve 43 opens and closes the introduction line 21c.

[0036] The fourth switching valve 44 is provided in the first forced circulation line 31a. The fourth switching valve 44 opens and closes the first forced circulation line 31a. The fifth switching valve 45 is provided on the second forced circulation line 31b near the tank 34. The fifth switching valve 45 opens and closes the second forced circulation line 31b. The sixth changeover valve 46 is provided on the pump line 37 on the upstream side and downstream side of the pump 35. The sixth changeover valve 46 opens and closes the pump line 37.

[0037] (Reservoir section) The reservoir unit 50 is provided to absorb a change in volume caused by thermal expansion of the refrigerant R circulating within the cooling system 1. The reservoir unit 50 has a reservoir pipe 51 and a reservoir valve 52. The reservoir pipe 51 extends in the vertical direction Dv and connects the upper end and the lower end of the second natural circulation line 21b. The connection portion between the upper end of the reservoir pipe 51 and the second natural circulation line 21b is located above the introduction line 21c. The connection portion between the lower end of the reservoir pipe 51 and the second natural circulation line 21b is located above the tank 34 and below the second switching valve 42. The reservoir valves 52 are provided at the upper end and the lower end of the reservoir pipe 51. By operating either one of the reservoir valves 52 to open the reservoir pipe 51, a part of the refrigerant R can be recovered to absorb the volume change due to the thermal expansion of the refrigerant R.

[0038] (duct) The duct 60 is disposed above the first heat exchanger 22. The duct 60 extends in the vertical direction Dv. The duct 60 has an exhaust flow path 61 therein that discharges air A from below upward. An inlet opening 61a through which the air A is introduced is provided at the lower end of the exhaust flow path 61. An outlet opening 61b through which the air A that has flowed through the exhaust flow path 61 is discharged is provided at the upper end of the exhaust flow path 61.

[0039] The duct 60 has a duct introduction section 62, a duct main body 63, and a duct discharge section 64. The duct introduction section 62 introduces the air A below into the exhaust flow path 61. The duct introduction section 62 extends in the vertical direction Dv and is formed in a bell-mouth shape with a diameter that decreases toward the top. The duct main body 63 is formed in a cylindrical shape that extends upward from the upper end of the duct introduction section 62. The duct main body 63 and the duct introduction section 62 are in communication with each other. The duct discharge section 64 is provided at the upper end of the duct main body 63. The duct discharge section 64 is formed in a cylindrical shape that curves in the horizontal direction toward the top from the duct main body 63. The duct discharge section 64 is in communication with the duct main body 63. The duct introduction section 62, the duct main body 63, and the duct discharge section 64 form the exhaust flow path 61. The opening at the lower end of the duct body 63 serves as an inlet opening 61a of the exhaust passage 61. The opening at the upper end of the duct exhaust section 64 opens in the horizontal direction. The opening at the upper end of the duct exhaust section 64 serves as an outlet opening 61b of the exhaust passage 61.

[0040] (Sensor) The sensor 4 acquires the amount of heat generated by each server rack 2. The information on the amount of heat generated by each server rack 2 acquired by the sensor 4 is sent to the control unit 70. When the cooling system 1 is introduced into a server center as in this embodiment, an intelligent PDU (Power Distribution Unit), for example, is used as the sensor 4. This intelligent PDU acquires the total amount of heat generated by each server rack 2 by observing the current value for each server rack 2. The sensor 4 may obtain the amount of heat generated for each heating element 3c.

[0041] (Control Unit) The control unit 70 controls the operation of each component of the cooling system 1. As shown in FIG. 4, the control unit 70 has the following functional sections: a receiving section 71, a heat generation temperature determining section 72, and a control section 73. The receiving unit 71 receives the temperature information and the like transmitted from the sensor 4 . The heat generation temperature determination unit 72 determines, from the temperature information received by the receiving unit 71, whether or not the heat generation temperature of the heat generating element 3c is equal to or higher than a threshold value. The control unit 73 controls various devices that configure the cooling system 1. The control unit 73 also has a switching control unit 73a and a pump control unit 73b. The switching control unit 73a controls the switching unit 40 to switch the flow system 6 of the refrigerant R. The pump control unit 73b controls the pump 35.

[0042] (Cooling system operation procedure) An example of a method of operating the cooling system 1 according to this embodiment will be described. As shown in FIG. 5, the switching control unit 73a controls the switching unit 40 to switch the flow system 6 of the refrigerant R to the natural circulation line 21 in advance.

[0043] Fig. 5 shows a state in which the circulation system 6 of the refrigerant R is switched to the natural circulation line 21. In Fig. 5, the lines opened by the switching unit 40 are shown by solid lines, and the lines closed by the switching unit 40 are shown by dashed lines.

[0044] At this time, the switching control unit 73a opens the first switching valve 41, the second switching valve 42, and the third switching valve 43. This opens the natural circulation line 21, allowing the refrigerant R to flow through the natural circulation line 21. Furthermore, the switching control unit 73a closes the fourth switching valve 44, the fifth switching valve 45, and the sixth switching valve 46. This opens the forced circulation line 31, preventing the refrigerant R from flowing through the forced circulation line 31.

[0045] Thereafter, when the heating element 3c is operated, the heating element 3c generates heat, and heat exchange between the refrigerant R and the heating element 3c begins in the cooling device 11. As a result, the heating element 3c is cooled, and the refrigerant R is heated by the exhaust heat of the heating element 3c. When the refrigerant R is heated in the cooling device 11, it boils, and the density of the refrigerant R decreases. This phenomenon occurs in each cooling device 11. As a result, an upward flow is generated from the cooling unit 10 toward the first heat exchanger 22. Therefore, the refrigerant R that has exchanged heat with the heating element 3c in each cooling device 11 is sent to the first heat exchanger 22 through the first natural circulation line 21a.

[0046] Air A is supplied to the first heat exchanger 22 from a blower fan 23. The first heat exchanger 22 exchanges heat between the refrigerant R and the outside air A, and discharges heat from the refrigerant R to the air A. The air A heated by the exhaust heat of the cold is discharged to the outdoors through an exhaust passage 61 in a duct 60.

[0047] On the other hand, the refrigerant R is cooled in the first heat exchanger 22, and the density of the refrigerant R increases. As a result, the refrigerant R is distributed from the first heat exchanger 22 to each cooling device 11 through the second natural circulation line 21b and the introduction line 21c. In this way, the coolant R utilizes the exhaust heat of the heat generating element 3c to naturally circulate within the natural circulation section 20. As a result, the heat generating element 3c is always cooled while it is in operation.

[0048] Here, if the cooling capacity of the first heat exchanger 22 is insufficient for the amount of heat generated, the refrigerant R will be completely vaporized in the cooling device 11 while circulating in the natural circulation section 20, and will not be able to sufficiently cool the heat generating body 3c. To prevent such a situation, in this embodiment, the cooling system 1 has a function of switching the flow system 6 of the refrigerant R from the natural circulation line 21 to the forced circulation line 31 by the switching section 40.

[0049] (Distribution system switching procedure) Next, a procedure for switching the flow system 6 of the refrigerant R according to this embodiment will be described with reference to Figs. FIG. 6 is a flow chart showing a procedure for switching the refrigerant R distribution system 6. In FIG. Moreover, Fig. 7 shows a state in which the circulation system 6 of the refrigerant R is switched to the forced circulation line 31. In Fig. 7, the lines opened by the switching unit 40 are shown by solid lines, and the lines closed by the switching unit 40 are shown by dashed lines.

[0050] The temperature of the heating element 3c is constantly or periodically detected by the sensor 4. The sensor 4 periodically transmits the detected temperature to the control unit . As shown in Fig. 6, first, the receiving unit 71 receives the temperature of the heating element 3c (step S11). After step S11, the heat generation temperature determining unit 72 determines whether the temperature of the heating element 3c is equal to or higher than a threshold value (step S12). This threshold value is set in advance in the control unit 70. If the temperature of the heating element 3c is equal to or higher than the threshold value (step S12; YES), it means that the cooling capacity of the first heat exchanger 22 of the natural circulation section 20 is insufficient for the amount of heat generated.

[0051] For this reason, in the next step, it is necessary to switch so that the refrigerant R is cooled by the second heat exchanger 36, which has a larger capacity than the first heat exchanger 22. First, the switching control unit 73a controls the switching unit 40 to switch the circulation system 6 of the refrigerant R from the natural circulation line 21 to the forced circulation line 31, as shown in FIG. 7 (step S13). In step S13, the switching control unit 73a closes the first switching valve 41, the second switching valve 42, and the third switching valve 43 to block the natural circulation line 21. Furthermore, the switching control unit 73a opens the fourth switching valve 44, the fifth switching valve 45, and the sixth switching valve 46 to open the forced circulation line 31.

[0052] After step S13, the pump control unit 73b drives the pump 35 (step S14). This causes the forced circulation unit 30 to operate, the refrigerant R circulates within the forced circulation unit 30, and the refrigerant R is cooled by the second heat exchanger 36, which has a larger capacity than the first heat exchanger 22. Note that if the forced circulation line 31 has already been opened in step S12, steps S13 and S14 are omitted.

[0053] On the other hand, if the temperature of the heat generating body 3c is not equal to or higher than the threshold value (step S12; NO), the cooling capacity of the first heat exchanger 22 of the natural circulation section 20 is sufficient for the amount of heat generated.

[0054] Therefore, in the next step, in order to reduce the operating energy, it is necessary to switch from the second heat exchanger 36 having a large capacity to the first heat exchanger 22 having a small capacity to cool the refrigerant R. First, the pump control unit 73b stops the pump 35 (step S15). After step S15, the switching control unit 73a controls the switching unit 40 to switch the circulation system 6 of the refrigerant R from the forced circulation line 31 to the natural circulation line 21 (step S16). In step S16, the switching control unit 73a closes the fourth switching valve 44, the fifth switching valve 45, and the sixth switching valve 46 to block the forced circulation line 31. Furthermore, the switching control unit 73a opens the first switching valve 41, the second switching valve 42, and the third switching valve 43 to open the natural circulation line 21. Note that, if the natural circulation line 21 has already been opened in step S12, steps S15 and S16 are omitted.

[0055] Through the above-described procedure, switching is performed for the flow system 6 of the refrigerant R. This switching of the flow system 6 of the refrigerant R is performed every time the receiving unit 71 receives the temperature of the heating element 3c. In step S13, the natural circulation line 21 is blocked and the forced circulation line 31 is opened, but this is not limited to the above. In step S13, both the natural circulation line 21 and the forced circulation line 31 may be opened so that the refrigerant R flows through both the natural circulation line 21 and the forced circulation line 31. In this case, the refrigerant R can be cooled by both the first heat exchanger 22 and the second heat exchanger 36.

[0056] (Action and effect) The cooling system 1 of the present embodiment can achieve the following effects.

[0057] In this embodiment, the cooling system 1 includes a cooling unit 10, a natural circulation section 20, and a forced circulation section 30. The cooling unit 10 includes a plurality of cooling devices 11, an inlet side header 12, and an outlet side header 15. The plurality of cooling devices 11 cool the heat generating body 3c. The inlet side header 12 distributes the refrigerant R to the cooling devices 11. The refrigerant R is discharged from each cooling device 11 to the outlet side header 15. The natural circulation section 20 includes a natural circulation line 21 and a first heat exchanger 22. The natural circulation line 21 connects the outlet side header 15 and the inlet side header 12. The first heat exchanger 22 is installed midway along the natural circulation line 21 and above the cooling unit 10. The forced circulation section 30 includes a forced circulation line 31, a second heat exchanger 36, and a pump 35. The forced circulation line 31 connects the outlet side header 15 and the inlet side header 12. The second heat exchanger 36 is provided in the middle of the forced circulation line 31. The second heat exchanger 36 has a larger capacity than the first heat exchanger 22. The pump 35 is provided in the forced circulation line 31. The pump 35 pumps the refrigerant R from the outlet side header 15 to the inlet side header 12.

[0058] According to the above configuration, each cooling device 11 exchanges heat between the heating element 3c and the refrigerant R to cool the heating element 3c. Meanwhile, the refrigerant R is heated by the heat generated by the heating element 3c. This reduces the density of the refrigerant R, and the refrigerant R flows upward. The natural circulation section 20 utilizes this flow to naturally circulate the refrigerant R. In the natural circulation section 20, the refrigerant R that has exchanged heat with the heating element 3c is cooled in the first heat exchanger 22 and is supplied to the heating element 3c again. In addition, the forced circulation section 30 forcibly circulates the refrigerant R by the pumping force of the pump 35. In the forced circulation section 30, the refrigerant R pumped by the pump 35 exchanges heat with the heating element 3c, is cooled in the second heat exchanger 36, and is supplied to the heating element 3c again. In this way, the refrigerant R is cooled in the first heat exchanger 22 in the natural circulation section 20, and the refrigerant R is cooled in the second heat exchanger 36 in the forced circulation section 30. Since the capacity of the second heat exchanger 36 is larger than the capacity of the first heat exchanger 22, even if the cooling capacity of the first heat exchanger 22 of the natural circulation section 20 is insufficient, the refrigerant R can be sufficiently cooled in the second heat exchanger 36 by utilizing the forced circulation section 30. In this way, the heat generating element 3c can be cooled sufficiently regardless of the temperature range of the heat generating element 3c while being energy-efficient. Therefore, according to this embodiment, the cooling efficiency of the cooling system 1 can be improved while ensuring sufficient cooling capacity.

[0059] The cooling system 1 also includes a switching unit 40. The switching unit 40 switches the circulation system 6 of the refrigerant R to at least one of the natural circulation line 21 and the forced circulation line 31.

[0060] As a result, when the cooling capacity of the first heat exchanger 22 is sufficient to cool the heat generating body 3c, the circulation system 6 of the refrigerant R can be switched to only the natural circulation line 21. As a result, the refrigerant R that has exchanged heat with the heat generating body 3c can be cooled using only the first heat exchanger 22. Since only the first heat exchanger 22 is used, the amount of energy required to operate the cooling system 1 can be reduced. On the other hand, when the cooling capacity of the first heat exchanger 22 is insufficient for the amount of heat generated, the circulation system 6 of the refrigerant R can be switched to only the forced circulation line 31, or to both the natural circulation line 21 and the forced circulation line 31. As a result, the refrigerant R that has exchanged heat with the heat generating body 3c can be cooled using the second heat exchanger 36, which has a larger capacity than the first heat exchanger 22, so that the refrigerant R can be sufficiently cooled. In this way, the refrigerant R can be circulated by switching between the natural circulation line 21 and the forced circulation line 31 depending on the amount of heat generated. Therefore, according to this embodiment, the cooling efficiency of the cooling system 1 can be further improved.

[0061] In addition, the second heat exchanger 36 is disposed below the cooling unit 10 .

[0062] In the forced circulation section 30, the refrigerant R is circulated mainly by the pumping force of the pump 35. Therefore, the refrigerant R supplied to the second heat exchanger 36 is sent to the second heat exchanger 36 before being completely vaporized. As a result, the density of the refrigerant R supplied to the second heat exchanger 36 is higher than the density of the refrigerant R supplied to the first heat exchanger 22. Since the high-density refrigerant R tends to accumulate at the bottom, as in this embodiment, by disposing the second heat exchanger 36 below the cooling unit 10, the refrigerant R is easily supplied to the second heat exchanger 36. Therefore, the second heat exchanger 36 can cool the refrigerant R more efficiently, and the cooling efficiency of the cooling system 1 can be further improved.

[0063] The natural circulation line 21 also has an introduction line 21c that introduces the refrigerant R that has undergone heat exchange in the first heat exchanger 22 into the inlet header 12. The introduction line 21c is disposed above the multiple cooling devices 11. The pump 35 is disposed below the multiple cooling devices 11.

[0064] In this manner, in this embodiment, the introduction line 21c is disposed above the multiple cooling devices 11. This makes it possible to shorten the flow path length of the natural circulation section 20. This makes it possible to suppress pressure loss when the refrigerant R is naturally circulated. On the other hand, the pump 35 is supplied with the refrigerant R that has been cooled and has an increased density. The high-density refrigerant R tends to descend. For this reason, by disposing the pump 35 below the multiple cooling devices 11 as in this embodiment, the refrigerant R is more easily supplied to the pump 35. This allows the refrigerant R to be stably supplied from the pump 35 to each cooling device 11. This makes it easier for the refrigerant R to circulate in both the natural circulation section 20 and the forced circulation section 30, and the cooling efficiency of the cooling system 1 can be further improved.

[0065] Furthermore, the forced circulation section 30 has a plurality of pumps 35 in the forced circulation line 31 .

[0066] As a result, even if, for example, one of the multiple pumps 35 unexpectedly stops operating, the other pumps 35 can continue to circulate the refrigerant R. In this way, the forced circulation unit 30 can be provided with redundancy.

[0067] The cooling system 1 further includes a duct 60 disposed above the first heat exchanger 22. The duct 60 extends in the vertical direction Dv, and has an exhaust passage 61 therein for discharging the air A from below upward.

[0068] The air A around the first heat exchanger 22 is heated by utilizing the exhaust heat of the refrigerant R. The high-temperature air A heated by the first heat exchanger 22 is supplied into the duct 60. As a result, the air A inside the duct 60 becomes hotter and less dense than the air A outside the duct 60, causing a draft effect (chimney effect, draft phenomenon). This causes the air A to flow from the bottom to the top of the duct 60. This makes it easier for the air A to be supplied to the first heat exchanger 22, accelerating the cooling of the refrigerant R by the first heat exchanger 22. This makes it possible to improve the cooling capacity of the cooling system 1.

[0069] Furthermore, it is possible to reduce the conveying force of, for example, the blower fan 23 that blows air to the first heat exchanger, which is necessary to supply air A to the first heat exchanger 22. When the load on the heat generating element 3c is low, the amount of heat generated is small, so it is also possible to supply a sufficient amount of air A to the first heat exchanger 22 by the flow of air A due to the draft effect of the duct 60. In this case, the blower fan 23 can be stopped. In this way, the refrigerant R can be cooled with high energy efficiency, so the cooling efficiency of the cooling system 1 can be further improved.

[0070] Duct 60 also has a bell-mouth shaped duct introduction portion 62 that introduces air A from below into exhaust flow path 61 and narrows in diameter as it extends upward.

[0071] This allows the duct 60 to smoothly introduce the air A into the exhaust passage 61. Therefore, the pressure loss when the air A is introduced can be reduced.

[0072] Moreover, the first heat exchanger 22 is installed so that the supply portion 25a is located above the discharge portion 25b.

[0073] This allows the refrigerant R to flow smoothly from the supply part 25a to the discharge part 25b inside the first heat exchanger 22. Therefore, the refrigerant R can be efficiently circulated inside the natural circulation part 20, and the cooling efficiency of the cooling system 1 can be further improved.

[0074] Next, a modified example of the first embodiment will be described. The same components as those in the first embodiment will be denoted by the same reference numerals and names, and the description will be omitted as appropriate. The components not described below are assumed to be the same as those in the first embodiment.

[0075] <First Modification of First Embodiment> A first modified example of the first embodiment will be described with reference to FIG. The cooling system 1A of this modification includes a server rack 2, a server 3, a cooling unit 10, a natural circulation section 20A, a forced circulation section 30, a switching section 40, a reservoir section 50, a duct 60, a sensor 4, and a control unit 70. The natural circulation section 20A includes a natural circulation line 21A, a first heat exchanger 22, a blower fan 23, and a relief valve 24. The natural circulation line 21A includes a first natural circulation line 21a, a second natural circulation line 21b, and an introduction line 21Ac.

[0076] 8, the introduction line 21Ac is disposed below the multiple cooling devices 11. The connection portion between the introduction line 21Ac and the second natural circulation line 21b is located above the tank 34 and below the second switching valve 42 and the reservoir valve 52 of the lower Dvd. The connection portion between the introduction line 21Ac and the inlet side header 12 is located below the multiple cooling devices 11.

[0077] (Action and effect) The cooling system 1A of this modified example can achieve the following advantageous effects.

[0078] In this modification, the introduction line 21Ac is disposed below the multiple cooling devices 11. The inlet line 21Ac is supplied with the refrigerant R whose density has increased as a result of being cooled in the first heat exchanger 22. High-density refrigerant R tends to flow downward. For this reason, by arranging the inlet line 21Ac below the multiple cooling devices 11 as in this embodiment, the refrigerant R is easily supplied to the inlet line 21Ac. This allows for a stable supply of the refrigerant R from the inlet line 21Ac to each cooling device 11. This makes it easier to circulate the refrigerant R in the natural circulation section 20A, and further improves the cooling efficiency of the cooling system 1A.

[0079] <Second Modification of First Embodiment> Next, a second modified example of the first embodiment will be described with reference to FIGS. The cooling system 1B of this modification includes a server rack 2, a server 3, a cooling unit 10, a natural circulation section 20B, a forced circulation section 30, a switching section 40, a reservoir section 50, a duct 60, a sensor 4, and a control unit 70. The natural circulation section 20B includes a natural circulation line 21, a first heat exchanger 22B, a connection section 26, a blower fan 23, and a relief valve 24.

[0080] As shown in FIGS. 9 and 10, four first heat exchangers 22B are placed on the top plate 2a of the rack. 9 and 10, illustration of some components such as the natural circulation line 21 that passes the refrigerant R through each first heat exchanger 22B is omitted.

[0081] The four first heat exchangers 22B are arranged around the edge of the top plate 2a. The first heat exchangers 22B are provided on each edge of the top plate 2a. The first heat exchangers 22B in this modification are the same radiators 25 as in the first embodiment. Each of the first heat exchangers 22B has a supply section 25a and a discharge section 25b. Each of the first heat exchangers 22B is installed so that the supply section 25a is located above the discharge section 25b. The discharge section 25b is attached so as to be along the edge of the top plate 2a. A connection portion 26 is provided between two adjacent first heat exchangers 22B so as to fill the gap. Each connection portion 26 connects adjacent first heat exchangers 22B.

[0082] (Action and effect) The cooling system 1B of this modified example can achieve the following effects.

[0083] In this modified example, the multiple first heat exchangers 22B are arranged around the edge of the top plate 2a, with one first heat exchanger 22B provided on each edge of the top plate 2a. In this way, many first heat exchangers 22B can be mounted on the server rack 2 without impeding the flow of the air A.

[0084] <Second embodiment> Next, a second embodiment will be described with reference to Fig. 11 to Fig. 13. The same components as those in the above embodiment and the above modified example will be denoted by the same reference numerals and names, and the description thereof will be omitted as appropriate. The components not described below are assumed to be the same as those in the above embodiment and the above modified example.

[0085] (Cooling System) In this embodiment, the cooling system 101 includes a server rack 2, a server 3, a cooling unit 10, a natural circulation section 120, a forced circulation section 130, a switching section 140, a sensor 4, and a control unit 170.

[0086] (Server rack) The server rack 2 is a housing extending in the vertical direction Dv similar to the first embodiment (see FIG. 2).

[0087] (server) A plurality of servers 3 are accommodated in the server rack 2, lined up in the vertical direction Dv. Each server 3 has a casing 3a, a server board 3b, and a heating element 3c. The casing 3a is inserted horizontally into the server rack 2. The server board 3b and the heating element 3c are accommodated inside the casing 3a. The server board 3b extends in the horizontal direction. The heating element 3c is attached to the server board 3b in the same manner as in the first embodiment.

[0088] (Cooling unit) As shown in Fig. 11, the cooling unit 10 has a plurality of cooling devices 11, an inlet side header 12, and an outlet side header 15. The plurality of cooling devices 11 cool the heat generating body 3c. The cooling devices 11 in this embodiment are cold plates 11a similar to those in the first embodiment. The inlet side header 12 distributes the refrigerant R to the cooling devices 11. The refrigerant R is discharged from each cooling device 11 to the outlet side header 15.

[0089] (Natural Circulation Department) The natural circulation section 120 includes a natural circulation line 121, a first heat exchanger 22, a blower fan 23, and a header 27. The natural circulation line 121 connects the outlet header 15 and the inlet header 12. The first heat exchanger 22 is installed in the middle of the natural circulation line 121 and above the cooling unit 10. Furthermore, the header 27 is arranged in the middle of the natural circulation line 121, downstream and below the first heat exchanger 22. Each component of the natural circulation section 120 will be described in detail below.

[0090] The natural circulation line 121 has a first natural circulation line 121a, a second natural circulation line 121b, and an introduction line 121c. The first natural circulation line 121a connects the upper end of the outlet side header 15 and the first heat exchanger 22. The first natural circulation line 121a guides the refrigerant R from the outlet side header 15 to the first heat exchanger 22. In the first heat exchanger 22, heat exchange of the refrigerant R is performed. The second natural circulation line 121b extends downward from the first heat exchanger 22.

[0091] The introduction line 121c is a bypass line that bypasses the second natural circulation line 121b. The introduction line 121c is disposed downstream and below the header 27. The introduction line 121c is disposed above the multiple cooling devices 11. The refrigerant R that has undergone heat exchange in the first heat exchanger 22 is temporarily stored in the header 27 and then supplied to the introduction line 121c via the second natural circulation line 121b. The introduction line 121c introduces the refrigerant R that has undergone heat exchange in the first heat exchanger 22 into the inlet header 12.

[0092] The first heat exchanger 22 cools the refrigerant R that has exchanged heat with the heat generating element 3c in the cooling device 11. The cooling device 11 of this embodiment is an air-cooled radiator 25 similar to that of the first embodiment. The header 27 can temporarily store the refrigerant R cooled in the first heat exchanger 22.

[0093] (forced circulation section) The forced circulation unit 130 is a mechanism for circulating the refrigerant R without heating the refrigerant R with exhaust heat from the heating element 3c. The forced circulation unit 130 has a forced circulation line 131 and a pump 35. The forced circulation line 131 connects the natural circulation line 121 downstream of the first heat exchanger 22 to the inlet header 12. The pump 35 is provided on the forced circulation line 131 downstream of the second heat exchanger 36. Each component of the forced circulation unit 130 will be described in detail below.

[0094] The forced circulation line 131 connects the lower end of the second natural circulation line 121b and the lower end of the inlet side header 12. The forced circulation line 131 is supplied with the refrigerant R that has been cooled by the first heat exchanger 22 and then temporarily stored in the header 27. The forced circulation line 131 guides the cooled refrigerant R to the inlet side header 12.

[0095] The pump 35 pumps the refrigerant R from the outlet side header 15 toward the inlet side header 12. The refrigerant R pumped by the pump 35 is distributed to each cooling device 11 from the inlet side header and circulates within the cooling system 101. The pump 35 is disposed below the multiple cooling devices 11.

[0096] (Switching section) The switching unit 140 includes a first switching valve 141 and a second switching valve 142 . The first switching valve 141 is provided in the introduction line 121c. The first switching valve 141 opens and closes the introduction line 121c. The second changeover valve 142 is provided on the forced circulation line 131, between the pump 35 and the inlet header 12. The second changeover valve 142 opens and closes the forced circulation line 131.

[0097] (Sensor) As in the first embodiment, the sensor 4 acquires the amount of heat generated for each server rack 2. The sensor 4 may acquire the amount of heat generated for each heating element 3c.

[0098] (Control Unit) The control unit 170 controls the operation of each component of the cooling system 101 . As shown in FIG. 12, the control unit 170 has the following functional sections: a receiving section 171, a heat generation temperature determining section 172, and a control section 173. The receiving unit 171 receives the temperature information and the like transmitted from the sensor 4 . The heat generation temperature determination unit 172 determines, from the temperature information received by the receiving unit 171, whether or not the heat generation temperature of the heat generating element 3c is equal to or higher than a threshold value. The control unit 173 controls various devices that configure the cooling system 101. The control unit 173 also includes a switching control unit 173a and a pump control unit 173b. The switching control unit 173a controls the switching unit 140 to switch the circulation system 106 of the refrigerant R. The circulation system 106 is a flow path through which the refrigerant R flows, and includes a natural circulation line 121 and a forced circulation line 131. The pump control unit 173b controls the pump 35.

[0099] (Cooling system operation procedure) An example of a method of operating the cooling system 101 according to this embodiment will be described. The switching control unit 173a controls the switching unit 140 to switch the flow system 106 of the refrigerant R to the natural circulation line 121 in advance.

[0100] At this time, the switching control unit 173a opens the first switching valve 141. This opens the natural circulation line 121, allowing the refrigerant R to flow through the natural circulation line 121. Furthermore, the switching control unit 173a closes the second switching valve 142. This opens the forced circulation line 131, preventing the refrigerant R from flowing through the forced circulation line 131.

[0101] Thereafter, when the heating element 3c is operated, the heating element 3c generates heat, and heat exchange between the refrigerant R and the heating element 3c begins in the cooling device 11. As a result, the heating element 3c is cooled, and the refrigerant R is heated by the exhaust heat of the heating element 3c. When the refrigerant R is heated in the cooling device 11, it boils, and the density of the refrigerant R decreases. This phenomenon occurs in each cooling device 11. As a result, an upward flow is generated from the cooling unit 10 toward the first heat exchanger 22. Therefore, the refrigerant R that has exchanged heat with the heating element 3c in each cooling device 11 is sent to the first heat exchanger 22 through the first natural circulation line 121a.

[0102] Air A is supplied to the first heat exchanger 22 from a blower fan 23. The first heat exchanger 22 exchanges heat between the refrigerant R and the outside air A, and dissipates heat of the refrigerant R to the air A.

[0103] On the other hand, the refrigerant R is cooled in the first heat exchanger 22, and the density of the refrigerant R increases. As a result, the refrigerant R is distributed from the first heat exchanger 22 to each cooling device 11 through the second natural circulation line 121b and the introduction line 121c. In this way, the coolant R utilizes the exhaust heat of the heat generating element 3c to naturally circulate within the natural circulation portion 120. As a result, the heat generating element 3c is always cooled while the heat generating element 3c is in operation.

[0104] Here, if the cooling capacity of the first heat exchanger 22 is insufficient for the amount of heat generated, the refrigerant R will be completely vaporized in the cooling device 11 while circulating in the natural circulation section 120, and will not be able to sufficiently cool the heat generating body 3c. To prevent such a situation, in this embodiment, the cooling system 101 has a function of switching the flow system 106 of the refrigerant R from the natural circulation line 121 to the forced circulation line 131 by the switching section 140.

[0105] (Distribution system switching procedure) Next, a procedure for switching the flow system 106 of the refrigerant R according to this embodiment will be described with reference to FIG. FIG. 13 is a flow chart showing a procedure for switching the refrigerant R distribution system 106. In FIG.

[0106] The temperature of the heating element 3c is constantly or periodically detected by the sensor 4. The sensor 4 transmits the detected temperature to the control unit 170 periodically. As shown in Fig. 13, first, the receiving unit 171 receives the temperature of the heating element 3c (step S21). After step S21, the heat generation temperature determining unit 172 determines whether the temperature of the heating element 3c is equal to or higher than a threshold value (step S22). This threshold value is set in advance in the control unit 170. If the temperature of the heating element 3c is equal to or higher than the threshold value (step S22; YES), this means that the cooling capacity of the first heat exchanger 22 of the natural circulation unit 120 is insufficient for the amount of heat generated.

[0107] For this reason, in the next step, it is necessary to switch so that the refrigerant R is pumped by the pump 35 to increase the flow rate of the refrigerant R. First, the switching control unit 173a controls the switching unit 140 to switch the distribution system 106 of the refrigerant R from the natural circulation line 121 to the forced circulation line 131 as shown in FIG. 13 (step S23). In step S23, the switching control unit 173a closes the first switching valve 141 to block the natural circulation line 121. Furthermore, the switching control unit 173a opens the second switching valve 142 to open the forced circulation line 131.

[0108] After step S13, the pump control unit 173b drives the pump 35 (step S24). This causes the forced circulation unit 130 to operate, and the refrigerant R circulates inside the forced circulation unit 130, so that the refrigerant R is supplied from below to each cooling device 11. Note that if the forced circulation line 131 has already been opened in step S22, steps S23 and S24 are omitted.

[0109] On the other hand, if the temperature of the heat generating body 3c is not equal to or higher than the threshold value (step S22; NO), the cooling capacity of the first heat exchanger 22 of the natural circulation section 120 is sufficient for the amount of heat generated.

[0110] Therefore, in the next step, in order to reduce the operating energy, it is necessary to switch to circulating the refrigerant R in the natural circulation unit 120, which does not require the pump 35 to be operated. First, the pump control unit 173b stops the pump 35 (step S25). After step S25, the switching control unit 173a controls the switching unit 140 to switch the distribution system 106 of the refrigerant R from the forced circulation line 131 to the natural circulation line 121 (step S26). In step S26, the switching control unit 173a closes the second switching valve 142 to block the forced circulation line 131. Furthermore, the switching control unit 173a opens the first switching valve 141 to open the natural circulation line 121. Note that, if the natural circulation line 121 has already been opened in step S22, steps S25 and S26 are omitted.

[0111] Through the above-described procedure, switching is performed for the flow system 106 of the refrigerant R. This switching of the flow system 106 of the refrigerant R is performed every time the receiving unit 171 receives the temperature of the heating element 3c. In step S23, the natural circulation line 121 is closed and the forced circulation line 131 is opened, but this is not limited to the above. In step S23, both the natural circulation line 121 and the forced circulation line 131 may be opened so that the refrigerant R flows through both the natural circulation line 121 and the forced circulation line 131.

[0112] (Action and effect) The cooling system 101 of the present embodiment can achieve the following effects.

[0113] In this embodiment, the natural circulation line 121 has an introduction line 121c that introduces the refrigerant R that has undergone heat exchange in the first heat exchanger 22 into the inlet side header 12. The introduction line 121c is disposed above the multiple cooling devices 11. The pump 35 is disposed below the multiple cooling devices 11.

[0114] In this manner, in this embodiment, the introduction line 121c is disposed above the plurality of cooling devices 11. This makes it possible to shorten the flow path length of the natural circulation section 120. This makes it possible to suppress pressure loss when the refrigerant R is naturally circulated. On the other hand, the pump 35 is supplied with the refrigerant R that has been cooled and has an increased density. The high-density refrigerant R tends to descend. For this reason, by disposing the pump 35 below the multiple cooling devices 11 as in this embodiment, the refrigerant R is more easily supplied to the pump 35. This allows the refrigerant R to be stably supplied from the pump 35 to each cooling device 11. This makes it easier for the refrigerant R to circulate in both the natural circulation section 120 and the forced circulation section 130, and the cooling efficiency of the cooling system 101 can be further improved.

[0115] Next, a modified example of the second embodiment will be described. The same components as those in the second embodiment will be denoted by the same reference numerals and names, and the description will be omitted as appropriate. The components not described below are assumed to be the same as those in the second embodiment.

[0116] <First Modification of Second Embodiment> A first modified example of the second embodiment will be described with reference to FIG. The cooling system 101A of this modification includes a server rack 2, a server 3, a cooling unit 10, a natural circulation section 120, a forced circulation section 130, a switching section 140, a sensor 4, a control unit 170, and further includes a duct 60.

[0117] (duct) The duct 60 is disposed above the first heat exchanger 22. The duct 60 extends in the vertical direction Dv. The duct 60 has an exhaust flow path 61 therein that discharges air A from below upward. An inlet opening 61a through which the air A is introduced is provided at the lower end of the exhaust flow path 61. An outlet opening 61b through which the air A that has flowed through the exhaust flow path 61 is discharged is provided at the upper end of the exhaust flow path 61.

[0118] The duct 60 of this embodiment is formed in the same shape as that of the first embodiment. That is, the duct 60 has a duct inlet 62, a duct body 63, and a duct outlet 64. The duct inlet 62 extends in the vertical direction Dv and is formed in a bell-mouth shape with a diameter that decreases toward the top.

[0119] (Action and effect) The cooling system 101A of this modified example can achieve the following advantageous effects.

[0120] The cooling system 101A of this modification further includes a duct 60 disposed above the first heat exchanger 22. The duct 60 extends in the vertical direction Dv and has an exhaust passage 61 therein for discharging the air A from below upward.

[0121] The air A around the first heat exchanger 22 is heated by utilizing the exhaust heat of the refrigerant R. The high-temperature air A heated by the first heat exchanger 22 is supplied into the duct 60. As a result, the air A inside the duct 60 becomes hotter and less dense than the air A outside the duct 60, causing a draft effect (chimney effect, draft phenomenon). This causes the air A to flow from the bottom to the top of the duct 60. This makes it easier for the air A to be supplied to the first heat exchanger 22, accelerating the cooling of the refrigerant R by the first heat exchanger 22. This can improve the cooling efficiency of the cooling system 101A.

[0122] Furthermore, it is possible to reduce the conveying force of, for example, the blower fan 23 that blows air to the first heat exchanger, which is necessary to supply air A to the first heat exchanger 22. When the load on the heat generating element 3c is low, the amount of heat generated is small, so it is also possible to sufficiently supply air A to the first heat exchanger 22 by the flow of air A due to the draft effect of the duct 60. In this case, the blower fan 23 can be stopped. In this way, the refrigerant R can be cooled with high energy efficiency, so the cooling efficiency of the cooling system 101A can be further improved.

[0123] <Second Modification of Second Embodiment> Next, a second modified example of the second embodiment will be described with reference to FIG. 15, a cooling system 101B of this modification has a plurality of unit sections 5 and a duct 160. Each unit section 5 further includes a server rack 2, a server 3, a cooling unit 10, a natural circulation section 120, a forced circulation section 130, a switching section 140, a duct 160, a sensor 4, and a control unit 170. That is, in this modification, one cooling system 101B includes a plurality of cooling units 10, a plurality of natural circulation sections 120 provided for each cooling unit 10, and a plurality of forced circulation sections 130.

[0124] The duct 160 of this modified example is disposed above the multiple unit parts 5. The duct 160 extends in the up-down direction Dv. As in the first embodiment, the duct 160 has an exhaust flow path 161 therein that discharges air A from below upward. An inlet opening 161a through which the air A is introduced is provided at the lower end of the exhaust flow path 161. An outlet opening 161b through which the air A that has flowed through the exhaust flow path 161 is discharged is provided at the upper end of the exhaust flow path 161.

[0125] The duct 160 has a duct introduction section 162, a duct header section 163, and a duct discharge section 164. The duct introduction section 162 is disposed above each of the first heat exchangers 22, and introduces air A from below into the inside. The duct introduction section 162 of this modification is formed in a bell-mouth shape that extends in the vertical direction Dv and has a diameter that decreases toward the top, as in the first embodiment. The duct header section 163 connects the upper ends of the multiple duct introduction sections 162 to each other, and merges the air A introduced from each duct introduction section 162. The duct header section 163 is disposed to extend in the horizontal direction. The duct discharge section 164 extends upward from the duct header section 163, and discharges the air A merged by the duct header section 163 upward. The duct discharge section 164 is formed in a cylindrical shape with a uniform thickness.

[0126] In this modification, the duct introduction portions 162, the duct header portion 163, and the duct discharge portion 164 form an exhaust flow path 161. The openings at the lower ends of the duct introduction portions 162 serve as inlet openings 161a of the exhaust flow path 161. The openings at the upper ends of the duct discharge portions 164 serve as outlet openings 161b of the exhaust flow path 161.

[0127] (Action and effect) The cooling system 101B of this modified example can achieve the following effects.

[0128] In the cooling system 101B of this modification, one cooling system 101B includes a plurality of cooling units 10, a plurality of natural circulation sections 120 provided for each cooling unit 10, and a plurality of forced circulation sections 130. Furthermore, the duct 160 includes a duct introduction section 162, a duct header section 163, and a duct discharge section 164. The duct introduction section 162 is disposed above each of the plurality of first heat exchangers 22, and introduces air A from below into the inside. The duct header section 163 connects the upper ends of the plurality of duct introduction sections 162 to each other, and merges the air A introduced from each duct introduction section 162. The duct discharge section 164 extends upward from the duct header section 163, and discharges the air A merged by the duct header section 163 upward.

[0129] According to the above configuration, the air A heated by the multiple first heat exchangers 22 can be merged into one flow. This can accelerate the flow of the air A from the bottom to the top of the duct 160. This can enhance the draft effect of the duct 160. This makes it easier for the air A to be supplied to the first heat exchangers 22, and further promotes the cooling of the refrigerant R by the first heat exchangers 22. This can further improve the cooling efficiency of the cooling system 101B. Furthermore, space saving can be achieved.

[0130] <Third embodiment> Next, a third embodiment will be described with reference to Fig. 16 and Fig. 17. The same components as those in the above embodiment and the above modified example will be denoted by the same reference numerals and names, and the description thereof will be omitted as appropriate. The components not described below are assumed to be the same as those in the above embodiment and the above modified example.

[0131] (Cooling System) In this embodiment, the cooling system 201 includes a server rack 2, a server 3, a cooling unit 10, a natural circulation section 120, and a control unit 270.

[0132] (Server rack) The server rack 2 is a housing extending in the vertical direction Dv similar to the first embodiment (see FIG. 2).

[0133] (server) A plurality of servers 3 are accommodated in the server rack 2, lined up in the vertical direction Dv. Each server 3 has a casing 3a, a server board 3b, and a heating element 3c. The casing 3a is inserted horizontally into the server rack 2. The server board 3b and the heating element 3c are accommodated inside the casing 3a. The server board 3b extends in the horizontal direction. The heating element 3c is attached to the server board 3b in the same manner as in the first embodiment.

[0134] (Cooling unit) As shown in Fig. 16, the cooling unit 10 has a plurality of cooling devices 11, an inlet side header 12, and an outlet side header 15. The plurality of cooling devices 11 cool the heat generating body 3c. The cooling devices 11 in this embodiment are cold plates 11a similar to the first embodiment. The inlet side header 12 distributes the refrigerant R to the cooling devices 11. The refrigerant R is discharged from each cooling device 11 to the outlet side header 15.

[0135] (Natural Circulation Department) The natural circulation section 120 includes a natural circulation line 121, a first heat exchanger 22, a blower fan 23, a header 27, and a valve . The natural circulation line 121 connects the outlet header 15 and the inlet header 12. The first heat exchanger 22 is installed in the middle of the natural circulation line 121 and above the cooling unit 10. Furthermore, the header 27 is arranged in the middle of the natural circulation line 121, downstream and below the first heat exchanger 22. Each component of the natural circulation section 120 will be described in detail below.

[0136] The natural circulation line 121 has a first natural circulation line 121a, a second natural circulation line 121b, and an introduction line 121c. The first natural circulation line 121a connects the upper end of the outlet side header 15 and the first heat exchanger 22. The first natural circulation line 121a guides the refrigerant R from the outlet side header 15 to the first heat exchanger 22. In the first heat exchanger 22, heat exchange of the refrigerant R is performed. The second natural circulation line 121b extends downward from the first heat exchanger 22.

[0137] The introduction line 121c is a bypass line that bypasses the second natural circulation line 121b. The introduction line 121c is disposed downstream and below the header 27. The introduction line 121c is disposed above the multiple cooling devices 11. The refrigerant R that has undergone heat exchange in the first heat exchanger 22 is temporarily stored in the header 27 and then supplied to the introduction line 121c via the second natural circulation line 121b. The introduction line 121c introduces the refrigerant R that has undergone heat exchange in the first heat exchanger 22 into the inlet header 12.

[0138] The first heat exchanger 22 cools the refrigerant R that has exchanged heat with the heat generating element 3c in the cooling device 11. The cooling device 11 of this embodiment is an air-cooled radiator 25 similar to that of the first embodiment.

[0139] The first heat exchanger 22 is placed, for example, on the top plate 2a of the server rack 2. As shown in Fig. 17, the first heat exchanger 22 is formed in a flat plate shape. The first heat exchanger 22 has a supply section 25a to which the refrigerant R is supplied from the outlet side header 15, and a discharge section 25b that discharges the refrigerant R toward the inlet side header 12. The first heat exchanger 22 is installed at an angle with respect to the horizontal plane HL so that the supply section 25a is located above the discharge section 25b.

[0140] The header 27 can temporarily store the refrigerant R cooled in the first heat exchanger 22. The valve 28 is provided in the introduction line 121c. The valve 28 opens and closes the introduction line 121c.

[0141] (Control Unit) The control unit 270 controls the operation of each component of the cooling system 201. The control unit 270 controls the opening and closing of the valve 28, for example.

[0142] (Cooling system operation procedure) An example of a method of operating the cooling system 201 according to this embodiment will be described. The control unit 270 opens the valve 28 of the introduction line 121c in advance. This opens the natural circulation line 121, allowing the refrigerant R to flow through the natural circulation line 121.

[0143] Thereafter, when the heating element 3c is operated, the heating element 3c generates heat, and heat exchange between the refrigerant R and the heating element 3c begins in the cooling device 11. As a result, the heating element 3c is cooled, and the refrigerant R is heated by the exhaust heat of the heating element 3c. When the refrigerant R is heated in the cooling device 11, it boils, and the density of the refrigerant R decreases. This phenomenon occurs in each cooling device 11. As a result, an upward flow is generated from the cooling unit 10 toward the first heat exchanger 22. Therefore, the refrigerant R that has exchanged heat with the heating element 3c in each cooling device 11 is sent to the first heat exchanger 22 through the first natural circulation line 121a.

[0144] Air A is supplied to the first heat exchanger 22 from a blower fan 23. The first heat exchanger 22 exchanges heat between the refrigerant R and the outside air A, and discharges heat from the refrigerant R to the air A. The air A heated by the exhaust heat of the cold is discharged to the outdoors through an exhaust passage 61 in a duct 60.

[0145] On the other hand, the refrigerant R is cooled in the first heat exchanger 22, and the density of the refrigerant R increases. As a result, the refrigerant R is distributed from the first heat exchanger 22 to each cooling device 11 through the second natural circulation line 121b and the introduction line 121c. In this way, the coolant R utilizes the exhaust heat of the heat generating element 3c to naturally circulate within the natural circulation portion 120. As a result, the heat generating element 3c is always cooled while the heat generating element 3c is in operation.

[0146] (Action and effect) The cooling system 201 of the present embodiment can achieve the following effects.

[0147] In this embodiment, the cooling system 201 further includes a duct 60 disposed above the first heat exchanger 22. The duct 60 extends in the vertical direction Dv and has an exhaust passage 61 therein for discharging the air A from below upward.

[0148] The air A around the first heat exchanger 22 is heated by utilizing the exhaust heat of the refrigerant R. The high-temperature air A heated by the first heat exchanger 22 is supplied into the duct 60. As a result, the air A inside the duct 60 becomes hotter and less dense than the air A outside the duct 60, causing a draft effect (chimney effect, draft phenomenon). This causes the air A to flow from the bottom to the top of the duct 60. This makes it easier for the air A to be supplied to the first heat exchanger 22, accelerating the cooling of the refrigerant R by the first heat exchanger 22. This makes it possible to improve the cooling capacity of the cooling system 201.

[0149] Furthermore, it is possible to reduce the conveying force of, for example, the blower fan 23 that blows air to the first heat exchanger, which is necessary to supply air A to the first heat exchanger 22. When the load on the heat generating element 3c is low, the amount of heat generated is small, so it is also possible to sufficiently supply air A to the first heat exchanger 22 by the flow of air A due to the draft effect of the duct 60. In this case, the blower fan 23 can be stopped. In this way, the refrigerant R can be cooled with high energy efficiency, so the cooling efficiency of the cooling system 201 can be further improved.

[0150] Moreover, the first heat exchanger 22 is installed so that the supply portion 25a is located above the discharge portion 25b.

[0151] This allows the refrigerant R to flow smoothly from the supply part 25a to the discharge part 25b inside the first heat exchanger 22. Therefore, the refrigerant R can be efficiently circulated inside the natural circulation part 120, and the cooling efficiency of the cooling system 201 can be further improved.

[0152] (Hardware configuration) The control units 70, 170, 270 of the above embodiments are implemented in a computer as shown in Fig. 18. Fig. 18 is an example of a schematic block diagram showing the configuration of a computer in which the control units 70, 170, 270 according to each embodiment are implemented. The computer 1100 includes a processor 1110, a main memory 1120, a storage 1130, and an interface 1140.

[0153] The operation of each functional part of the control units 70, 170, and 27050 is stored in the form of a program in the storage 1130. The processor 1110 reads the program from the storage 1130, loads it in the main memory 1120, and executes the above-mentioned processing in accordance with the program. The processor 1110 also secures a storage area in the main memory 1120 in accordance with the program.

[0154] The program may be for realizing a part of the functions to be performed by the computer 1100. For example, the program may be for realizing the functions by combining with other programs already stored in the storage 1130 or by combining with other programs implemented in other devices. The computer 1100 may also include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions to be realized by the processor 1110 may be realized by the integrated circuit.

[0155] Examples of storage 1130 include a magnetic disk, a magneto-optical disk, and a semiconductor memory. Storage 1130 may be an internal medium directly connected to the bus of computer 1100, or an external medium connected to computer 1100 via interface 1140 or a communication line. In addition, when this program is distributed to computer 1100 via a communication line, computer 1100 that receives the program may load the program in main memory 1120 and execute the above-mentioned processing. Storage 1130 may be a non-transitory tangible storage medium.

[0156] The program may be for realizing part of the above-mentioned functions. Furthermore, the program may be a so-called difference file (difference program) that realizes the above-mentioned functions in combination with other programs already stored in the storage 1130.

[0157] (Other embodiments) Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to the embodiments, and design modifications and the like that do not depart from the gist of the present disclosure are also included. In addition, the above-described embodiments and modifications can be appropriately combined.

[0158] In the above embodiment, the heat generating element 3c to be cooled by the cooling system 1, 1A, 1B, 101, 101A, 101B, 201 is a chip such as a CPU or GPU mounted on the server 3, but is not limited thereto. The heat generating element 3c may be, for example, an electronic device mounted on a vehicle.

[0159] In the above embodiment, the cooling device 11 is the cold plate 11a, but is not limited to this. The cooling device 11 may be, for example, a container that stores an insulating refrigerant R and immerses the heating element 3c in the refrigerant R.

[0160] In the above embodiment, the first heat exchangers 22, 22B are air-cooled radiators 25 that perform heat exchange between the air A and the refrigerant R, but are not limited thereto. For example, the first heat exchangers 22, 22B may be water-cooled plate heat exchangers such as the second heat exchanger 36 that perform heat exchange between the cooling water and the refrigerant R.

[0161] In the above embodiment, the second heat exchanger 36 is a water-cooled plate 36a type heat exchanger, but is not limited to this. For example, the second heat exchanger 36 may be an air-cooled radiator that performs heat exchange between air and the refrigerant R, like the first heat exchangers 22 and 22B.

[0162] In the above embodiment, the switching units 40, 140 are operated by the control units 70, 170, 270, but the present invention is not limited to this. The switching units 40, 140 may be operated manually.

[0163] In the above embodiment, the shape of the duct 60, 160 has been described in detail, but the shape of the duct 60, 160 can be changed as appropriate. For example, the duct introduction part 62, 162 is formed in a bell-mouth shape extending in the vertical direction Dv and tapering upward, but is not limited to this. The duct introduction part 62, 162 may be formed in a cylindrical shape with a uniform thickness.

[0164] <Additional Notes> The cooling systems 1, 1A, 1B, 101, 101A, 101B, and 201 described in the respective embodiments can be understood, for example, as follows.

[0165] (1) The cooling system 1, 1A, 1B according to the first aspect includes a cooling unit 10 having a plurality of cooling devices 11 for cooling a heat generating body 3c, an inlet side header 12 for distributing a refrigerant R to the cooling devices 11, and an outlet side header 15 through which the refrigerant R is discharged from each of the cooling devices 11, natural circulation lines 21, 21A connecting the outlet side header 15 and the inlet side header 12, and a cooling unit 10 having a natural circulation line 21, 21A disposed midway between the natural circulation lines 21, 21A and above the cooling unit 10. The system is equipped with a natural circulation section 20, 20A, 20B having first heat exchangers 22, 22B, a forced circulation line 31 connecting the outlet side header 15 and the inlet side header 12, a second heat exchanger 36 provided midway along the forced circulation line 31 and having a larger capacity than the first heat exchangers 22, 22B, and a forced circulation section 30 provided on the forced circulation line 31 and having a pump 35 for pressure-feeding the refrigerant R from the outlet side header 15 toward the inlet side header 12.

[0166] According to the above configuration, each cooling device 11 exchanges heat between the heat generating element 3c and the refrigerant R to cool the heat generating element 3c. Meanwhile, the refrigerant R is heated by the heat generated by the heat generating element 3c. This reduces the density of the refrigerant R, and the refrigerant R flows upward. The natural circulation parts 20, 20A, and 20B utilize this flow to naturally circulate the refrigerant R. In the natural circulation parts 20, 20A, and 20B, the refrigerant R that has exchanged heat with the heat generating element 3c is cooled in the first heat exchanger 22 and 22B and is supplied to the heat generating element 3c again. In addition, the forced circulation part 30 forcibly circulates the refrigerant R by the pumping force of the pump 35. In the forced circulation part 30, the refrigerant R that has been pumped by the pump 35 exchanges heat with the heat generating element 3c, is cooled in the second heat exchanger 36, and is supplied to the heat generating element 3c again. In this way, in the natural circulation sections 20, 20A, 20B, the refrigerant R is cooled in the first heat exchangers 22, 22B, and in the forced circulation sections 30, 130, the refrigerant R is cooled in the second heat exchanger 36. Since the capacity of the second heat exchanger 36 is larger than the capacity of the first heat exchangers 22, 22B, the refrigerant R can be sufficiently cooled in the second heat exchanger 36 by utilizing the forced circulation section 30, even if the cooling capacity of the first heat exchangers 22, 22B of the natural circulation sections 20, 20A, 20B is insufficient.

[0167] (2) The cooling system 1, 1A, 1B of the second aspect may be the cooling system 1, 1A, 1B of the first aspect, and may be provided with a switching unit 40 that switches the circulation system of the refrigerant R to at least one of the natural circulation lines 21, 21A and the forced circulation line 31.

[0168] As a result, when the cooling capacity of the first heat exchangers 22 and 22B is sufficient to cool the heat generating body 3c, the circulation system of the refrigerant R can be switched only to the natural circulation lines 21 and 21A. As a result, the refrigerant R that has exchanged heat with the heat generating body 3c can be cooled using only the first heat exchangers 22 and 22B. Since only the first heat exchangers 22 and 22B are used, the amount of energy required to operate the cooling systems 1, 1A, and 1B can be reduced. On the other hand, when the cooling capacity of the first heat exchangers 22 and 22B is insufficient for the amount of heat generated, the circulation system of the refrigerant R can be switched only to the forced circulation line 31, or to both the natural circulation lines 21 and 21A and the forced circulation line 31. As a result, the refrigerant R that has exchanged heat with the heat generating body 3c can be cooled using the second heat exchanger 36, which has a larger capacity than the first heat exchangers 22 and 22B, so that the refrigerant R can be sufficiently cooled.

[0169] (3) The cooling system 1, 1A, 1B of a third aspect is the cooling system 1, 1A, 1B of the first or second aspect, and the second heat exchanger 36 may be disposed below the cooling unit 10.

[0170] In the forced circulation section 30, the refrigerant R is circulated mainly by the pumping force of the pump 35. Therefore, the refrigerant R supplied to the second heat exchanger 36 is sent to the second heat exchanger 36 before being completely vaporized. As a result, the density of the refrigerant R supplied to the second heat exchanger 36 becomes higher than the density of the refrigerant R supplied to the first heat exchangers 22, 22B. Since the high-density refrigerant R tends to accumulate at the bottom, by disposing the second heat exchanger 36 below the cooling unit 10 as in this embodiment, the refrigerant R is easily supplied to the second heat exchanger 36.

[0171] (4) A fourth aspect of the cooling system 1, 1B is a cooling system 1, 1B of any one of the first to third aspects, wherein the natural circulation line 21 is arranged above the multiple cooling devices 11 and has an inlet line 21c that introduces the refrigerant R that has undergone heat exchange in the first heat exchanger 22 into the inlet side header 12, and the pump 35 may be arranged below the multiple cooling devices 11.

[0172] In this embodiment, the introduction line 21c is disposed above the plurality of cooling devices 11. This makes it possible to shorten the flow path length of the natural circulation section 20. This makes it possible to suppress pressure loss when the refrigerant R is naturally circulated. On the other hand, the pump 35 is supplied with the refrigerant R that has been cooled and has an increased density. The refrigerant R with a high density tends to descend. For this reason, by disposing the pump 35 below the multiple cooling devices 11 as in this embodiment, the refrigerant R is easily supplied to the pump 35. This allows the refrigerant R to be stably supplied from the pump 35 to each cooling device 11.

[0173] (5) The cooling system 1, 1A, 1B of a fifth aspect may be the cooling system 1, 1A, 1B of any one of the first to fourth aspects, and may further include a duct 60 arranged above the first heat exchanger 22, 22B, extending in the vertical direction Dv and having an exhaust passage 61 therein for discharging air A from below upward.

[0174] The air A around the first heat exchangers 22 and 22B is heated by utilizing the exhaust heat of the refrigerant R. The high-temperature air A heated by the first heat exchangers 22 and 22B is supplied into the duct 60. As a result, the air A inside the duct 60 becomes hotter and less dense than the air A outside the duct 60, and a draft effect (chimney effect, draft phenomenon) occurs. This causes the air A to flow from the bottom to the top of the duct 60. This makes it easier for the air A to be supplied to the first heat exchangers 22 and 22B, and promotes the cooling of the refrigerant R by the first heat exchangers 22 and 22B. Furthermore, it is possible to reduce the conveying force of, for example, the blower fan 23 that blows air to the first heat exchanger, which is necessary to supply the air A to the first heat exchangers 22 and 22B.

[0175] (6) A sixth aspect of the cooling system 1, 1A, 1B is a cooling system 1, 1A, 1B of any one of the first to fifth aspects, wherein the first heat exchanger 22, 22B has a supply section 25a to which the refrigerant R is supplied from the outlet side header 15, and a discharge section 25b that discharges the refrigerant R toward the inlet side header 12, and the first heat exchanger 22, 22B may be installed so that the supply section 25a is positioned above the discharge section 25b.

[0176] This allows the refrigerant R to flow smoothly through the first heat exchangers 22, 22B from the supply portion 25a toward the discharge portion 25b.

[0177] (7) The cooling system 101, 101A, 101B according to the seventh aspect includes a cooling unit 10 having a plurality of cooling devices 11 for cooling a heat generating body 3c, an inlet side header 12 for distributing a refrigerant R to the cooling devices 11, and an outlet side header 15 through which the refrigerant R is discharged from each of the cooling devices 11, a natural circulation section 120 having a natural circulation line 121 connecting the outlet side header 15 and the inlet side header 12, and a first heat exchanger 22 installed in the middle of the natural circulation lines 21, 21A, 121 and above the cooling unit 10, and a second heat exchanger 23 installed in front of the natural circulation line 121. The system is equipped with a forced circulation line 131 connecting the downstream side of the first heat exchanger 22 and the inlet side header 12, and a forced circulation section 130 having a pump 35 provided on the forced circulation line 131 and pressure-feeding the refrigerant R from the outlet side header 15 toward the inlet side header 12, wherein the natural circulation line 121 is positioned above the multiple cooling devices 11 and has an introduction line 121c that introduces the refrigerant R that has undergone heat exchange in the first heat exchanger 22 into the inlet side header 12, and the pump 35 is positioned below the multiple cooling devices 11.

[0178] (8) The cooling systems 101, 101A, 101B according to the eighth aspect may be the cooling systems 101, 101A, 101B according to the seventh aspect, and may further include a duct 60, 160 disposed above the first heat exchanger 22 and extending in the vertical direction Dv and having an exhaust passage 61, 161 therein for discharging the air A from below upward.

[0179] (9) The cooling system 101B of the ninth aspect is the cooling system 101B of the eighth aspect, and includes a plurality of the cooling units 10, a plurality of the natural circulation sections 120 provided for each of the cooling units 10, and a plurality of the forced circulation sections 130, and the duct 160 may have a duct inlet section 162 arranged above each of the plurality of first heat exchangers 22 and introducing air A into the interior from below, a duct header section 163 connecting the upper ends of the plurality of duct inlets 162 and joining the air A introduced from each of the duct inlets 162, and a duct discharge section 164 extending upward from the duct header section 163 and discharging the air A joined by the duct header section 163 upward.

[0180] According to the above configuration, the air A heated by the multiple first heat exchangers 22 can be merged into one flow. This makes it possible to accelerate the flow of the air A from the lower part to the upper part of the duct 160. Furthermore, space saving can be achieved.

[0181] (10) A cooling system 201 according to a tenth aspect includes a cooling unit 10 having a plurality of cooling devices 11 for cooling a heat generating element 3c, an inlet side header 12 for distributing refrigerant R to the cooling devices 11, and an outlet side header 15 through which the refrigerant R is discharged from each of the cooling devices 11, a natural circulation section 120 having a natural circulation line 121 connecting the outlet side header 15 and the inlet side header 12 and a first heat exchanger 22 installed midway along the natural circulation line 121 and above the cooling unit 10, and a duct 60 disposed above the first heat exchanger 22 and extending in a vertical direction Dv, and having an exhaust passage 61 therein for discharging air A from below upward.

[0182] (11) A cooling system 201 according to an eleventh aspect is the cooling system 201 according to the tenth aspect, wherein the first heat exchanger 22, 22B has a supply section 25a to which the refrigerant R is supplied from the outlet side header 15, and a discharge section 25b that discharges the refrigerant R toward the inlet side header 12, and the first heat exchanger 22 may be installed so that the supply section 25a is positioned above the discharge section 25b. [Explanation of symbols]

[0183] 1...Cooling system 2...Server rack 2a...Top plate 3...Server 3a...Casing 3b...Server board 3c...Heater 4...Sensor 6...Circulation system 10...Cooling unit 11...Cooling device 11a...Cold plate 12...Inlet header 13...Inlet branch line 14...Valve 15...Outlet header 16...Outlet branch line 20...Natural circulation section 21...Natural circulation line 21a...First natural circulation line 21b...Second natural circulation line 21c...Inlet line 22...First heat exchanger 23...Blower fan 24...Relief valve 25...Radiator 25a...Supply section 25b...Exhaust section 30...Forced circulation section 31...Forced circulation line 31a...First forced circulation line 31b...Second forced circulation line 31c...Third forced circulation line 32...Separate CDU 33...Chiller device 34...Tank 35...Pump 36...Second heat exchanger 36a...Water-cooled plate 36b...Valve 37...Pump line 38...Confluence line 40...Switching section 41...First switching valve 42...Second switching valve 43...Third switching valve 44...Fourth switching valve 45...Fifth switching valve 46...Sixth switching valve 50...Reservoir section 51...Reservoir pipe 52...Reservoir valve 60...Duct 61...Exhaust flow path 61a...Inlet opening 61b...Outlet opening 62...Duct introduction section 63...Duct body 64...Duct exhaust section 70...Control unit 71...Receiver 72...Heat generation temperature determination section 73...Control section 73a...Switching control section 73b...Pump control section A...Air Dv...Up-down direction Dvu...Upper side Dvd...Lower side HL...Horizontal surface R…Refrigerant W…Cooling water 1A...Cooling system 20A...Natural circulation section 21A...Natural circulation line 21Ac...Inlet line 1B...cooling system 20B...natural circulation section 22B...first heat exchanger 26...connection section 101...cooling system 120...natural circulation section 121...natural circulation line 121a...first natural circulation line 121b...second natural circulation line 121c...introduction line 27...header 130...forced circulation section 131...forced circulation line 140...switching section 141...first switching valve 142...second switching valve 170...control unit 171...receiving section 172...heat generation temperature determination section 173...control section 173a...switching control section 173b...pump control section 101A…Cooling system 101B: Cooling system 5: Unit section 106: Flow system 160: Duct 161: Exhaust flow path 161a: Inlet opening 161b: Outlet opening 162: Duct introduction section 163: Duct header section 164: Duct discharge section 201...cooling system 28...valve 270...control unit 1100... computer 1110... processor 1120... main memory 1130... storage 1140... interface

Claims

1. a cooling unit including a plurality of cooling devices for cooling a heat generating body, an inlet header for distributing a refrigerant to the cooling devices, and an outlet header through which the refrigerant is discharged from each of the cooling devices; a natural circulation section including a natural circulation line connecting the outlet side header and the inlet side header, and a first heat exchanger installed midway along the natural circulation line and above the cooling unit; a forced circulation section including a forced circulation line connecting the outlet side header and the inlet side header, a second heat exchanger provided in the forced circulation line and having a capacity larger than that of the first heat exchanger, and a pump provided in the forced circulation line for pressure-feeding the refrigerant from the outlet side header to the inlet side header; A cooling system comprising:

2. The cooling system according to claim 1 , further comprising a switching unit that switches the refrigerant circulation system to at least one of the natural circulation line and the forced circulation line.

3. The cooling system according to claim 1 or 2, wherein the second heat exchanger is disposed below the cooling unit.

4. the natural circulation line is disposed above the plurality of cooling devices and includes an introduction line through which the refrigerant that has undergone heat exchange in the first heat exchanger is introduced into the inlet header, The cooling system according to claim 1 or 2, wherein the pump is disposed below the plurality of cooling devices.

5. The cooling system according to claim 1 or 2, further comprising a duct arranged above the first heat exchanger, extending in the vertical direction and having an exhaust passage therein for discharging air from below upward.

6. The first heat exchanger is a supply section to which the refrigerant is supplied from the outlet header; a discharge portion that discharges the refrigerant toward the inlet header; having The cooling system according to claim 1 or 2, wherein the first heat exchanger is disposed so that the supply portion is located above the discharge portion.

7. a cooling unit including a plurality of cooling devices for cooling a heat generating body, an inlet header for distributing a refrigerant to the cooling devices, and an outlet header through which the refrigerant is discharged from each of the cooling devices; a natural circulation section including a natural circulation line connecting the outlet side header and the inlet side header, and a first heat exchanger installed midway along the natural circulation line and above the cooling unit; a forced circulation line connecting a downstream side of the first heat exchanger of the natural circulation line and the inlet header, and a forced circulation unit including a pump provided in the forced circulation line and configured to pump the refrigerant from the outlet header to the inlet header; Equipped with the natural circulation line is disposed above the plurality of cooling devices and includes an introduction line through which the refrigerant that has undergone heat exchange in the first heat exchanger is introduced into the inlet header, The cooling system, wherein the pump is disposed below the plurality of cooling devices.

8. The cooling system according to claim 7 , further comprising a duct disposed above the first heat exchanger, extending in the vertical direction and having an exhaust passage therein for discharging air from below upward.

9. A plurality of the cooling units; A plurality of the natural circulation sections and a plurality of the forced circulation sections provided for each cooling unit; Equipped with The duct is a duct introduction portion disposed above each of the first heat exchangers and introducing air into the inside from below; a duct header portion that connects upper ends of the plurality of duct introduction portions to each other and joins the air introduced from each of the duct introduction portions; a duct discharge portion extending upward from the duct header portion and discharging the air joined by the duct header portion upward; The cooling system of claim 8 , comprising:

10. a cooling unit including a plurality of cooling devices for cooling a heat generating body, an inlet header for distributing a refrigerant to the cooling devices, and an outlet header through which the refrigerant is discharged from each of the cooling devices; a natural circulation section including a natural circulation line connecting the outlet side header and the inlet side header, and a first heat exchanger installed midway along the natural circulation line and above the cooling unit; a duct disposed above the first heat exchanger and extending in a vertical direction and having an exhaust passage therein for discharging air from below upward; A cooling system comprising:

11. The first heat exchanger is a supply section to which the refrigerant is supplied from the outlet header; a discharge portion that discharges the refrigerant toward the inlet header; having The cooling system according to claim 10 , wherein the first heat exchanger is disposed so that the supply portion is located above the discharge portion.

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