Cooling system

Abstract

A cooling system according to the present disclosure comprises: a circulation system in which a refrigerant for cooling a heat-generating element flows; and a pressure-reduction unit connected to the circulation system. The circulation system comprises: a cooling unit that is attached to the heat-generating element and removes heat from the heat-generating element by boiling the refrigerant; a heat-exchange unit that is provided at a position higher than the cooling unit and condenses a gaseous refrigerant; a gas line that guides the refrigerant evaporated by the cooling unit to the heat-exchange unit; and a liquid line that guides the refrigerant condensed by the heat-exchange unit to the cooling unit. The pressure-reduction unit decompresses the circulation system by removing the gas from the inside of the circulation system.

Description

Cooling system

[0001] This application claims priority to Japanese Patent Application No. 2024-020310, filed February 14, 2024, the contents of which are incorporated herein by reference.

[0002] In recent years, energy consumption in data centers has been increasing. In server cooling systems, it is important to reduce power consumption as much as possible. For example, Patent Document 1 discloses a cooling device that cools electronic devices (heat sources) such as CPUs installed in servers. This cooling device includes an evaporator that removes heat from the heat source using the latent heat of vaporization of a liquid. A low-boiling-point refrigerant such as R134a or R1233zd is used as the liquid that cools the heat source.

[0003] Patent No. 6079343

[0004] However, in consideration of recent regulations on PFAS (fluorinated organic compounds), it is possible that these refrigerants may become unusable in the future. Therefore, there is a need to develop a cooling system that can provide sufficient cooling performance even when using a refrigerant that does not fall under the category of PFAS and is not subject to usage restrictions.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a cooling system that can improve cooling efficiency.

[0006] In order to solve the above problems, the cooling system of the present disclosure comprises a circulation system through which a refrigerant for cooling a heat-generating element circulates, and a pressure reduction unit connected to the circulation system, wherein the circulation system comprises a cooling unit attached to the heat-generating element and removing heat from the heat-generating element by boiling the refrigerant, a heat exchange unit located at a higher position than the cooling unit and condensing the gaseous refrigerant, a gas line leading the refrigerant evaporated in the cooling unit to the heat exchange unit, and a liquid line leading the refrigerant condensed in the heat exchange unit to the cooling unit, and the pressure reduction unit reduces the pressure in the circulation system by removing gas from within the circulation system.

[0007] According to the cooling system of the present disclosure, the cooling efficiency can be improved.

[0008] FIG. 1 is a configuration diagram of a cooling system according to a first embodiment of the present disclosure. FIG. 2 is a functional block diagram of a control device according to a first embodiment of the present disclosure. FIG. 3 is a flowchart showing the procedure of a basic operation of a cooling system according to a first embodiment of the present disclosure. FIG. 4 is a flowchart showing the procedure of an operation to remove non-condensable gas from a circulation system according to a first embodiment of the present disclosure. FIG. 5 is a flowchart showing the procedure of an operation to forcibly circulate a refrigerant according to a first embodiment of the present disclosure. FIG. 6 is a flowchart showing the procedure of an operation to open a pressure reducing unit to the atmosphere according to a first embodiment of the present disclosure. FIG. 7 is a flowchart showing the procedure of an operation to return a refrigerant from the pressure reducing unit to the circulation system according to a first embodiment of the present disclosure. FIG. 8 is a configuration diagram of a cooling system according to a second embodiment of the present disclosure. FIG. 9 is a configuration diagram of a cooling system according to a third embodiment of the present disclosure. FIG. 10 is a configuration diagram of a cooling system according to a fourth embodiment of the present disclosure. FIG. 11 is a hardware configuration diagram according to an embodiment of the present disclosure.

[0009] First Embodiment (Configuration of Cooling System) A cooling system 1 according to a first embodiment of the present disclosure will be described below with reference to FIGS. 1 to 7 . As shown in FIG. 1 , the cooling system 1 includes a server rack 2, a server 3, a distribution system 20, a pressure reducing unit 30, a switching mechanism 40, a distribution system temperature sensor 4, a distribution system pressure sensor 5, a heat generation temperature sensor 6, a pressure reducing unit pressure sensor 7, a level sensor 8, a refrigerant return line 9, a refrigerant return valve 9a, a refrigerant return pump 9b, a power supply unit 10, a duct 11, and a control device 12. Note that FIG. 1 schematically illustrates each component of the cooling system 1. Hereinafter, the vertical direction may be simply referred to as the "vertical direction Dv." The upper side is denoted by the symbol "Dvu," and the lower side is denoted by the symbol "Dvd."

[0010] (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 houses devices that constitute the cooling system 1 inside. In addition to the servers 3, the server rack 2 houses, for example, a refrigerant tank 25 (described later), a forced circulation pump 28, a pressure reduction unit 33, a power supply unit 10, and the like.

[0011] (Server) A plurality of servers 3 are housed in the server rack 2. Each server 3 has a casing 3a, a server board 3b, and a heating element 3c. The casing 3a is a box-shaped enclosure extending horizontally. The casing 3a is inserted horizontally into the server rack 2. The casing 3a houses the server board 3b and the heating element 3c. The server board 3b extends horizontally.

[0012] (Heat-generating element) The heat-generating element 3c is an electronic component mounted on the server board 3b. The heat-generating element 3c is, for example, a chip such as a CPU or GPU installed on the server board 3b. The heat-generating element 3c generates heat during operation. The heat-generating element 3c has a temperature range in which it can operate most efficiently. The cooling system 1 cools each heat-generating element 3c to this temperature range in which it can operate most efficiently.

[0013] (Circulation System) A refrigerant R for cooling the heat generating element 3 c flows through the circulation system 20. In this embodiment, the refrigerant R is water. The circulation system 20 includes a cooling unit 21, a heat exchange unit 22, a gas line 23, a liquid line 24, a refrigerant tank 25, a second cooling unit 26, a forced circulation line 27, and a forced circulation pump 28.

[0014] (Cooling Unit) The cooling unit 21 is attached to the heating element 3c. A refrigerant R is supplied to the cooling unit 21. A flow path through which the refrigerant R flows is formed inside the cooling unit 21. The cooling unit 21 removes heat from the heating element 3c by boiling the refrigerant R. This cools the heating element 3c. The cooling unit 21 of this embodiment is a box-shaped cold plate formed so that the refrigerant R can flow inside.

[0015] (Heat Exchange Unit) The heat exchange unit 22 is provided at a higher position than the cooling unit 21. The refrigerant R that has been boiled and vaporized by the cooling unit 21 is supplied to the heat exchange unit 22. The heat exchange unit 22 condenses the gaseous refrigerant R. The heat exchange unit 22 of this embodiment performs heat exchange between the refrigerant R and the air outside the heat exchange unit 22, thereby removing heat from the refrigerant R and condensing the refrigerant R.

[0016] (Gas Line) The gas line 23 guides the refrigerant R evaporated in the cooling section 21 to the heat exchange section 22. The gas line 23 extends upward from the upper wall of the cooling section 21 and is connected to the upper part of the heat exchange section 22.

[0017] (Liquid Line) The liquid line 24 guides the refrigerant R condensed in the heat exchange unit 22 to the cooling unit 21. The liquid line 24 extends downward from the lower part of the heat exchange unit 22 and is connected to the cooling unit 21. The connection between the liquid line 24 and the cooling unit 21 is located lower than the connection between the gas line 23 and the cooling unit 21.

[0018] (Refrigerant Tank) The refrigerant tank 25 is provided on the liquid line 24. The refrigerant tank 25 stores the liquid refrigerant R that has passed through the heat exchange unit 22.

[0019] (Second Cooling Unit) The second cooling unit 26 is provided in the refrigerant tank 25. The second cooling unit 26 cools the refrigerant R. In this embodiment, the second cooling unit 26 is ice placed in the refrigerant tank 25. Note that the second cooling unit 26 may be any cooling unit as long as it is capable of cooling the refrigerant R. The second cooling unit 26 may be, for example, a cooler driven by an external power source (not shown).

[0020] (Forced Circulation Line) The forced circulation line 27 branches off from the liquid line 24 and returns the refrigerant R to the cooling unit 21. In this embodiment, the upstream end of the forced circulation line 27 is connected to the refrigerant tank 25. The downstream end of the forced circulation line 27 is located downstream of the refrigerant tank 25 in the liquid line 24, and is connected between the refrigerant tank 25 and the cooling unit 21.

[0021] (Forced Circulation Pump) The forced circulation pump 28 is provided in the forced circulation line 27 and is a pump capable of pressure-feeding the refrigerant R to the cooling unit 21. The forced circulation pump 28 pressure-feeds the liquid refrigerant R stored in the refrigerant tank 25 to the cooling unit 21. The forced circulation pump 28 is driven by power supplied from an external power source (not shown) and the power supply unit 10, which will be described later.

[0022] (Decompression Section) The decompression section 30 is connected to the flow system 20, and reduces the pressure of the flow system 20 by removing gas from the flow system 20. The decompression section 30 includes a gas removal line 31, a gas removal valve 32, and a decompression unit 33.

[0023] (Gas removal line) The gas removal line 31 is connected to the circulation system 20 and is a line for removing gas from the circulation system 20. The gas removal line 31 is connected to the highest position in the circulation system 20. In other words, the pressure reduction section 30 is connected to the highest position in the circulation system 20. In the present embodiment, the gas removal line 31 is connected to the highest position in the heat exchange section 22.

[0024] (Gas Vent Valve) The gas vent valve 32 is provided in the gas vent line 31 and is a valve that can open and close the gas vent line 31 .

[0025] (Decompression Unit) The decompression unit 33 is housed in the server rack 2. The decompression unit 33 has an ejector 34, a drive pump 35, a drive fluid supply line 36, a drive fluid return line 37, a drive fluid tank 38, an atmosphere release line 39, and an atmosphere release valve 39a.

[0026] (Ejector) The ejector 34 is connected to the downstream end of the gas removal line 31. The driving fluid L is supplied to the ejector 34 from an external source. The ejector 34 sucks gas from the gas removal line 31 by the flow of the driving fluid L circulating inside the ejector 34. In this embodiment, the driving fluid L is water, the same as the refrigerant R. The ejector 34 has a supply unit 34a, a discharge unit 34b, and a suction unit 34c. The supply unit 34a is supplied with the driving fluid L from a driving fluid supply line 36 (described later). The discharge unit 34b communicates with the supply unit 34a and discharges the driving fluid L that has passed through the ejector 34 to a driving fluid return line 37 (described later). The suction unit 34c is provided at the connection between the supply unit 34a and the discharge unit 34b and is communicated with both the supply unit 34a and the discharge unit 34b. The downstream end of the gas removal line 31 is connected to the suction unit 34c. The gas in the gas removal line 31 is drawn into the suction section 34c by the flow of the driving fluid L from the supply section 34a to the discharge section 34b. The gas drawn into the suction section 34c is discharged together with the driving fluid L from the discharge section 34b.

[0027] (Drive Pump) The drive pump 35 pumps the drive fluid L and supplies the drive fluid L to the ejector 34. In this embodiment, the forced circulation pump 28 also functions as the drive pump 35. That is, one pump functions as both the forced circulation pump 28 and the drive pump 35.

[0028] (Drive Fluid Supply Line) The drive fluid supply line 36 guides the drive fluid L from the drive pump 35 to the ejector 34. In this embodiment, the drive fluid supply line 36 connects the forced circulation line 27 downstream of the forced circulation pump 28 (drive pump 35) to a supply unit 34a of the ejector 34.

[0029] (Driving Fluid Return Line) The driving fluid return line 37 returns the driving fluid L discharged from the ejector 34 to the driving pump 35. In this embodiment, the driving fluid return line 37 connects the discharge portion 34b of the ejector 34 to a part of the forced circulation line 27 upstream of the forced circulation pump 28 (driving pump 35).

[0030] (Drive Fluid Tank) The drive fluid tank 38 is provided on the drive fluid return line 37. The drive fluid tank 38 is a tank capable of storing the drive fluid L.

[0031] (Atmospheric Release Line) The atmospheric release line 39 is provided on the upper part of the driving fluid tank 38. The atmospheric release line 39 is a pipe that connects the inside and outside of the driving fluid tank 38.

[0032] (Atmospheric Release Valve) The atmospheric release valve 39 a is provided in the atmospheric release line 39 and is a valve that can open and close the atmospheric release line 39 .

[0033] (Switching Mechanism) The switching mechanism 40 is a mechanism that can switch the flow path of the refrigerant R between a flow path in which the refrigerant R does not pass through the forced circulation line 27 and a flow path in which the refrigerant R passes through the forced circulation line 27. In the present embodiment, the switching mechanism 40 can also switch the connection between the decompression unit 33 and the distribution system 20. The switching mechanism 40 has a first valve 41, a second valve 42, a third valve 43, a fourth valve 44, and a fifth valve 45.

[0034] The first valve 41 is provided in the liquid line 24 downstream of the refrigerant tank 25 and between the refrigerant tank 25 and the cooling unit 21. The first valve 41 is a valve that can open and close the liquid line 24. The second valve 42 is provided in the forced circulation line 27 downstream of the refrigerant tank 25 and upstream of the connection between the driving fluid return line 37 and the forced circulation line 27. The second valve 42 is a valve that can open and close the forced circulation line 27. The third valve 43 is provided in the forced circulation line 27 downstream of the connection between the driving fluid supply line 36 and the forced circulation line 27. The third valve 43 is a valve that can open and close the forced circulation line 27.

[0035] The fourth valve 44 is provided in the driving fluid supply line 36 and is capable of opening and closing the driving fluid supply line 36. The fifth valve 45 is provided in the driving fluid return line 37 downstream of the driving fluid tank 38. The fifth valve 45 is a valve that is capable of opening and closing the driving fluid return line 37.

[0036] (Circulation System Temperature Sensor) The circulation system temperature sensor 4 measures the temperature inside the circulation system 20. The circulation system temperature sensor 4 is provided in the gas vent line 31 near the connection with the heat exchanger 22. The circulation system temperature sensor 4 is also provided in the gas vent line 31 upstream of the gas vent valve 32.

[0037] (Circulation System Pressure Sensor) The circulation system pressure sensor 5 measures the pressure inside the circulation system 20. The circulation system pressure sensor 5 is provided in the gas vent line 31 near the connection with the heat exchange unit 22. The circulation system pressure sensor 5 is also provided in the gas vent line 31 upstream of the gas vent valve 32.

[0038] (Heat generating temperature sensor) The heat generating temperature sensor 6 is connected to the heat generating element 3c and measures the temperature of the heat generating element 3c.

[0039] (Decompression Section Pressure Sensor) The decompression section pressure sensor 7 measures the pressure inside the decompression section 30. The decompression section pressure sensor 7 is provided in the driving fluid tank 38.

[0040] (Level Sensor) The level sensor 8 is provided in the upper part of the driving fluid tank 38. The level sensor 8 comes into contact with the liquid surface of the fluid stored in the driving fluid L, thereby detecting that the fluid has accumulated in the driving fluid tank 38 up to the height of the level sensor 8. The level sensor 8 is provided below the atmosphere vent line 39.

[0041] (Refrigerant Return Line) The refrigerant return line 9 connects the driving fluid tank 38 and the refrigerant tank 25. The refrigerant return line 9 is a pipe that returns the refrigerant R that has entered the driving fluid tank 38 into the refrigerant tank 25.

[0042] (Refrigerant Return Valve) The refrigerant return valve 9 a is provided in the refrigerant return line 9 and is a valve that can open and close the refrigerant return line 9 .

[0043] (Refrigerant Return Pump) The refrigerant return pump 9b is provided upstream of the refrigerant return valve 9a in the refrigerant return line 9. The refrigerant return pump 9b pumps the refrigerant R mixed in the driving fluid tank 38 into the refrigerant tank 25.

[0044] (Power Supply Unit) The power supply unit 10 generates power using, for example, a Peltier element or the like, by utilizing the temperature difference between the heating element 3c and the cooling unit 21. The power supply unit 10 supplies power to the forced circulation pump .

[0045] (Duct) The duct 11 discharges air around the heat exchange unit 22 upward. The duct 11 has a lower opening 11a, an upper opening 11b, and a cylindrical portion 11c. The lower opening 11a houses the heat exchange unit 22 and opens downward. The upper opening 11b is located higher than the lower opening 11a and opens upward. The cylindrical portion 11c connects the lower opening 11a and the upper opening 11b. The cylindrical portion 11c extends in the vertical direction Dv and connects the lower opening 11a and the upper opening 11b.

[0046] 2, the control device 12 includes functional units, such as a pressure reduction control unit 50, a forced circulation control unit 60, an atmosphere release control unit 70, and a refrigerant return control unit 80. The control device 12 can be operated by an operator.

[0047] (Depressurization Control Unit) The depressurization control unit 50 controls the depressurization unit 30. The depressurization control unit 50 includes a circulation system temperature acquisition unit 51, a circulation system pressure acquisition unit 52, a saturation pressure calculation unit 53, a circulation system pressure determination unit 54, and a depressurization operation unit 55.

[0048] (Distribution System Temperature Acquisition Unit) The distribution system temperature acquisition unit 51 acquires the temperature measured by the distribution system temperature sensor 4 .

[0049] (Distribution System Pressure Acquisition Unit) The distribution system pressure acquisition unit 52 acquires the pressure measured by the distribution system pressure sensor 5 .

[0050] (Saturation Pressure Calculation Unit) The saturation pressure calculation unit 53 calculates the saturation pressure in the flow system 20 from the temperature measured by the flow system temperature sensor 4 .

[0051] (Circulation System Pressure Determination Unit) The circulation system pressure determination unit 54 determines whether the pressure measured by the circulation system pressure sensor 5 is higher than the saturation pressure of the refrigerant R in the circulation system 20 calculated by the saturation pressure calculation unit 53 .

[0052] (Pressure reduction operation unit) The pressure reduction operation unit 55 causes the pressure reduction unit 30 to remove gas from the circulation system 20 and reduce the pressure in the circulation system 20. For example, when the pressure measured by the circulation system pressure sensor 5 is higher than the saturation pressure of the refrigerant R in the circulation system 20 calculated by the saturation pressure calculation unit 53, the pressure reduction operation unit 55 causes the pressure reduction unit 30 to reduce the pressure in the circulation system 20.

[0053] (Forced Circulation Control Unit) The forced circulation control unit 60 forcibly circulates the refrigerant R within the circulation system 20. The forced circulation control unit 60 has a heat generation temperature acquisition unit 61, a heat generation temperature determination unit 62, a forced circulation operation unit 63, and a flow rate adjustment unit 64.

[0054] (Heat Generation Temperature Acquisition Unit) The heat generation temperature acquisition unit 61 acquires the temperature measured by the heat generation temperature sensor 6 .

[0055] (Heat Generation Temperature Determining Unit) The heat generation temperature determining unit 62 determines whether the temperature measured by the heat generation temperature sensor 6 is higher than a predetermined temperature.

[0056] (Forced Circulation Operation Unit) The forced circulation operation unit 63 operates the switching mechanism 40 and the forced circulation pump 28 to forcibly circulate the refrigerant R within the distribution system 20. For example, when the temperature measured by the heat generation temperature sensor 6 is higher than a predetermined temperature, the forced circulation operation unit 63 causes the switching mechanism 40 to switch the flow path of the refrigerant R to a flow path in which at least a portion of the refrigerant R passes through the forced circulation line 27, and operates the forced circulation pump 28.

[0057] (Flow Rate Adjustment Unit) The flow rate adjustment unit 64 controls the rotation speed of the forced circulation pump 28 and adjusts the flow rate of the refrigerant R by the forced circulation pump 28 .

[0058] (Atmosphere Release Control Unit) The atmosphere release control unit 70 controls the release of the pressure reduction unit 30 to the atmosphere. The atmosphere release control unit 70 has a pressure reduction unit internal pressure acquisition unit 71, a pressure reduction unit internal pressure determination unit 72, and an atmosphere release operation unit 73.

[0059] (Decompression Unit Internal Pressure Acquisition Unit) The decompression unit internal pressure acquisition unit 71 acquires the pressure inside the decompression unit 30 measured by the decompression unit pressure sensor 7 .

[0060] (Decompression Unit Internal Pressure Determination Unit) The decompression unit internal pressure determination unit 72 determines whether the pressure inside the decompression unit 30 measured by the decompression unit pressure sensor 7 is higher than a predetermined pressure.

[0061] (Atmosphere release operation unit) The atmosphere release operation unit 73 operates the atmosphere release valve 39a to open the pressure reduction unit 30 to the atmosphere. For example, when the pressure inside the pressure reduction unit 30 measured by the pressure reduction unit pressure sensor 7 is higher than a predetermined pressure, the atmosphere release operation unit 73 operates the atmosphere release valve 39a to open the atmosphere release line 39.

[0062] (Refrigerant Return Control Unit) The refrigerant return control unit 80 controls the operation of returning the refrigerant R from the pressure reducing unit 30 to the distribution system 20. The refrigerant return control unit 80 has a liquid level detection information acquisition unit 81 and a refrigerant return operation unit 82.

[0063] (Liquid Level Detection Information Acquisition Unit) The liquid level detection information acquisition unit 81 acquires information on the liquid level of the fluid stored in the driving fluid tank 38 detected by the level sensor 8 .

[0064] (Refrigerant return operation unit) When the liquid level detection information acquisition unit 81 acquires information that the level sensor 8 has detected the liquid level, for example, the refrigerant return operation unit 82 operates the refrigerant return valve 9a to open the refrigerant return line 9 and operates the refrigerant return pump 9b to return the refrigerant R that has mixed in the pressure reduction unit 30 from the tank of driving fluid L to the refrigerant tank 25.

[0065] (Basic Operation of Cooling System) The basic operation of the cooling system 1 according to this embodiment will be described with reference to the flow chart in FIG. 3 . First, the decompression operation unit 55 operates the decompression unit 30 in advance (step S1). In step S1, the decompression operation unit 55 operates the gas vent valve 32 to open the gas vent line 31. Then, the decompression operation unit 55 operates the drive pump 35. This causes gas to be vented from the circulation system 20, and the circulation system 20 is depressurized. Thereafter, the decompression operation unit 55 operates the gas vent valve 32 to close the gas vent line 31. Then, the decompression operation unit 55 stops the drive pump 35. Note that the time for which the decompression operation unit 55 operates the drive pump 35 can be changed as appropriate. For example, the decompression operation unit 55 may operate the decompression unit 30 only for a moment.

[0066] After step S1, the heating element 3c is operated (step S2). In step S2, the refrigerant R in the cooling unit 21 boils due to the heat of the heating element 3c. Because the pressure in the circulation system 20 is reduced, the boiling point of the refrigerant R is lower than before the pressure is reduced. Therefore, the refrigerant R boils faster than before the pressure is reduced. As the refrigerant R boils, gaseous refrigerant R is generated. At this time, the heat of vaporization of the refrigerant R is removed from the heating element 3c. This cools the heating element 3c. The gaseous refrigerant R is supplied to the heat exchange unit 22 through a gas line 23 provided above the cooling unit 21. In the heat exchange unit 22, heat exchange occurs between the outside air and the refrigerant R. This cools and condenses the refrigerant R. The condensed refrigerant R passes through a liquid line 24 and is stored in the refrigerant tank 25. The refrigerant R stored in the refrigerant tank 25 is supplied again to the cooling unit 21 through the liquid line 24. In this way, the refrigerant R naturally circulates within the circulation system 20 solely by natural convection caused by the heat of the heating element 3c. In step S2, the first valve 41 opens the liquid line 24, and the second valve 42 and the third valve 43 close the forced circulation line 27. With the above procedure, the basic operation of the cooling system 1 is completed.

[0067] The order of steps S1 and S2 may be adjusted as appropriate. For example, the pressure reduction operation unit 55 may operate the pressure reduction unit 30 while the refrigerant R is circulating in the distribution system 20.

[0068] The cooling system 1 can perform operations other than the basic operations described above. Operations other than the basic operations will be described below.

[0069] (Operation of Removing Non-condensable Gas) Non-condensable gas may be mixed into the circulation system 20. The non-condensable gas increases the pressure inside the circulation system 20. When the pressure inside the circulation system 20 increases, the boiling point of the refrigerant R increases, making it difficult for the refrigerant R to evaporate. For this reason, it is preferable to remove the non-condensable gas from the circulation system 20. The procedure for removing the non-condensable gas from the circulation system 20 will be described below with reference to the flow chart in FIG. 4.

[0070] First, the circulation system temperature acquisition unit 51 acquires the temperature measured by the circulation system temperature sensor 4 (step S10). After step S10, the circulation system pressure acquisition unit 52 acquires the pressure measured by the circulation system pressure sensor 5 (step S11). The timing at which step S11 is started can be changed as appropriate. For example, steps S10 and S11 may be performed simultaneously. After step S11, the saturation pressure calculation unit 53 calculates the saturation pressure in the circulation system 20 from the temperature measured by the circulation system temperature sensor 4 (step S12).

[0071] After step S12, the circulation system pressure determination unit 54 determines whether the pressure measured by the circulation system pressure sensor 5 is higher than the saturation pressure of the refrigerant R in the circulation system 20 calculated by the saturation pressure calculation unit 53 (step S13).

[0072] If the pressure measured by the circulation system pressure sensor 5 is higher than the saturation pressure of the refrigerant R in the circulation system 20 calculated by the saturation pressure calculation unit 53 (step S13; YES), it means that non-condensable gas has been mixed into the circulation system 20 to an extent that it prevents the refrigerant R from boiling. In this case (step S13; YES), the pressure reduction operation unit 55 operates the pressure reduction unit 30 (step S14). In step S14, the pressure reduction unit 30 removes gas from the circulation system 20. As a result, the non-condensable gas is removed from the circulation system 20, and the pressure in the circulation system 20 decreases. Thereafter, the pressure reduction operation unit 55 stops the operation of the pressure reduction unit 30, and this flow ends.

[0073] On the other hand, if the pressure measured by the flow system pressure sensor 5 is not higher than the saturation pressure of the refrigerant R in the flow system 20 calculated by the saturation pressure calculation unit 53 (step S13; NO), it is unlikely that non-condensable gas has been mixed into the flow system 20 to an extent that it would prevent the refrigerant R from boiling. In this case (step S13; NO), this flow ends without going through step S14. The operation of removing the non-condensable gas is completed through the above procedure.

[0074] The series of steps from S10 to S14 may be started by the operator at any timing, or may be performed automatically at regular intervals. Also, the operator may omit steps S10 to S13 from the series of steps from S10 to S14 and execute step S14 at any timing.

[0075] (Forced Circulation Operation) Furthermore, if the temperature of the heating element 3c exceeds a criterion (for example, between 70°C and 120°C), dryout occurs in the cooling unit 21. This causes an insufficient supply of refrigerant R to the cooling unit 21, and the cooling system 1 is unable to sufficiently cool the heating element 3c. To prepare for such a situation, the cooling system 1 is provided with a function to forcibly circulate the refrigerant R. The procedure for forcibly circulating the refrigerant R will be described below with reference to the flow chart in FIG. 5 .

[0076] First, the heat generation temperature acquisition unit 61 acquires the temperature measured by the heat generation temperature sensor 6 (step S20). After step S20, the heat generation temperature determination unit 62 determines whether the temperature measured by the heat generation temperature sensor 6 is higher than a predetermined temperature (step S21). This predetermined temperature can be set as appropriate. For example, the predetermined temperature is set as a criterion. If the temperature measured by the heat generation temperature sensor 6 is higher than the predetermined temperature (step S21; YES), the forced circulation operation unit 63 causes the switching mechanism 40 to switch the flow path of the refrigerant R to a flow path through which at least a portion of the refrigerant R passes through the forced circulation line 27 and activates the forced circulation pump 28 (step S22). In step S22, for example, the first valve 41 closes the liquid line 24, and the second valve 42 and the third valve 43 open the forced circulation line 27. As a result, all of the refrigerant R circulating within the distribution system 20 passes through the forced circulation line 27. The refrigerant R passing through the forced circulation line 27 is pumped by the forced circulation pump 28. The refrigerant R is forced to circulate within the circulation system 20 by the pumping force of the forced circulation pump 28 in addition to natural convection caused by the heat of the heating element 3c. As a result, a larger amount of refrigerant R is supplied to the cooling unit 21 per unit time, the shortage of refrigerant R supplied to the cooling unit 21 is resolved, and this flow ends. In step S22, the fourth valve 44 closes the driving fluid supply line 36, and the fifth valve 45 closes the driving fluid return line 37.

[0077] On the other hand, if the temperature measured by the heat generation temperature sensor 6 is not higher than the predetermined temperature (step S21; NO), step S22 is skipped and this flow ends. With the above procedure, the forced circulation operation ends.

[0078] Furthermore, among the flow paths of the refrigerant R, a flow path through which the refrigerant R passes through the forced circulation line 27 is referred to as a forced circulation flow path, and a flow path through which the refrigerant R does not pass through the forced circulation line 27 is referred to as a natural circulation flow path. In step 22, the first valve 41 opens the liquid line 24, and the cooling system 1 may use both the forced circulation flow path and the natural circulation flow path. In this case, the flow rate adjustment unit 64 may adjust the rotation speed of the forced circulation pump 28 to minimize the power consumption of the forced circulation pump 28.

[0079] Furthermore, the worker may omit steps S20 to S21 from the series of steps S20 to S22 and execute step S22 at any timing.

[0080] In this embodiment, both the refrigerant R and the driving fluid L are water. Therefore, for example, the pressure reducing unit 30 may be operated while the refrigerant R is being forcibly circulated within the distribution system 20 (step S22). In this case, the fourth valve 44 opens the driving fluid supply line 36, and the fifth valve 45 opens the driving fluid return line 37. The forced circulation pump 28 also functions as the drive pump 35, and circulates the driving fluid L within the pressure reducing unit 33.

[0081] (Opening of pressure reducing unit to atmosphere) Every time the pressure reducing unit 30 is operated, it releases gas from the circulation system 20, causing an increase in internal pressure. For this reason, the cooling system 1 is provided with a function to open the pressure reducing unit 30 to the atmosphere. The procedure for opening the pressure reducing unit 30 to the atmosphere will be described below with reference to the flow chart in FIG. 6 .

[0082] First, the pressure reduction unit internal pressure acquisition unit 71 acquires the pressure in the pressure reduction unit 30 measured by the pressure reduction unit pressure sensor 7 (step S30). After step S31, the pressure reduction unit internal pressure determination unit 72 determines whether the pressure in the pressure reduction unit 30 measured by the pressure reduction unit pressure sensor 7 is higher than a predetermined pressure (step S31). This predetermined pressure can be set as appropriate. The predetermined pressure may be, for example, the design pressure of the pressure reduction unit 30. If the pressure in the pressure reduction unit 30 measured by the pressure reduction unit pressure sensor 7 is higher than the predetermined pressure (step S31; YES), the atmosphere release operation unit 73 operates the atmosphere release valve 39a to open the atmosphere release line 39 (step S32). This reduces the pressure in the pressure reduction unit 30, and this flow ends.

[0083] On the other hand, if the pressure inside the pressure reducing section 30 measured by the pressure reducing section pressure sensor 7 is not higher than the predetermined pressure (step S31; NO), step S32 is omitted and this flow ends. With the above procedure, the operation of opening the pressure reducing section 30 to the atmosphere is completed.

[0084] Furthermore, the worker may omit steps S30 to S31 from the series of steps S30 to S32 and execute step S32 at any timing.

[0085] (Refrigerant Return Operation) When the pressure reduction unit 30 removes gas from the distribution system 20, the refrigerant R may be sucked into the pressure reduction unit 30. The refrigerant R sucked into the pressure reduction unit 30 is stored in the driving fluid tank 38. Meanwhile, the amount of refrigerant R in the distribution system 20 decreases. For this reason, the cooling system 1 has a function of returning the refrigerant R from the pressure reduction unit 30 to the distribution system 20. The operation of returning the refrigerant R from the pressure reduction unit 30 to the distribution system 20 will be described below with reference to the flow in FIG. 7 .

[0086] First, the liquid level detection information acquisition unit 81 acquires information indicating that the level sensor 8 has detected the liquid level of the fluid stored in the driving fluid tank 38 (step S40). After step S40, the refrigerant return operation unit 82 operates the refrigerant return valve 9a to open the refrigerant return line 9 and activates the refrigerant return pump 9b (step S41). As a result, the refrigerant R that has entered the pressure reduction unit 30 is returned from the driving fluid tank 38 to the refrigerant tank 25. This completes the refrigerant return operation.

[0087] Furthermore, the worker may omit step S40 from the series of steps S40 to S41 and execute step S41 at any timing.

[0088] (Operations and Effects) According to the cooling system 1 of this embodiment, the following operations and effects can be achieved.

[0089] In this embodiment, the cooling system 1 includes a circulation system 20 and a pressure reduction unit 30. A refrigerant R for cooling the heat-generating element 3c flows through the circulation system 20. The circulation system 20 includes a cooling unit 21, a heat exchange unit 22, a gas line 23, and a liquid line 24. The cooling unit 21 is attached to the heat-generating element 3c and removes heat from the heat-generating element 3c by boiling the refrigerant R. The heat exchange unit 22 is provided at a higher position than the cooling unit 21 and condenses the gaseous refrigerant R. The gas line 23 guides the refrigerant R evaporated in the cooling unit 21 to the heat exchange unit 22. The pressure reduction unit 30 is connected to the circulation system 20. The pressure reduction unit 30 reduces the pressure of the circulation system 20 by removing gas from within the circulation system 20.

[0090] According to the above configuration, the cooling system 1 can reduce the pressure within the distribution system 20 and create a low-pressure state below atmospheric pressure. This lowers the boiling point of the refrigerant R. Therefore, the cooling system 1 can boil the refrigerant R in the cooling unit 21 at a lower temperature than before the pressure reduction. Therefore, the cooling system 1 can efficiently cool the heat-generating element 3c. Therefore, even if a liquid with a high boiling point at atmospheric pressure, such as water, that does not fall under the PFAS category, is used as the refrigerant R, as in this embodiment, the cooling system 1 can efficiently cool the heat-generating element 3c. Furthermore, because the distribution system 20 is under negative pressure, even if the distribution system 20 is damaged, air is drawn into the distribution system 20. This flow of drawn air prevents the refrigerant R from leaking to the outside. Therefore, the cooling system 1 can prevent leaked refrigerant R from flowing toward the server 3. Furthermore, even if non-condensable gases are mixed into the distribution system 20, the decompression unit 30 can remove the non-condensable gases.

[0091] In this embodiment, the pressure reducing unit 30 is connected to the highest position in the distribution system 20 .

[0092] When non-condensable gas is mixed in the circulation system 20, the non-condensable gas tends to accumulate in the upper part of the circulation system 20. According to the above configuration, the pressure reducing section 30 can efficiently remove the non-condensable gas that has accumulated in the upper part of the circulation system 20.

[0093] In this embodiment, the pressure reducing unit 30 includes a gas vent line 31, an ejector 34, a drive pump 35, a drive fluid supply line 36, a drive fluid return line 37, and a drive fluid tank 38. The gas vent line 31 is connected to the circulation system 20 and is a pipe that vents gas from the circulation system 20. The ejector 34 is connected to the gas vent line 31 and sucks gas from the gas vent line 31 by the flow of drive fluid L circulating therethrough. The drive pump 35 supplies the drive fluid L to the ejector 34. The drive fluid supply line 36 guides the drive fluid L from the drive pump 35 to the ejector 34. The drive fluid return line 37 returns the drive fluid L discharged from the ejector 34 to the drive pump 35. The drive fluid tank 38 is provided on the drive fluid return line 37 and can store the drive fluid L.

[0094] According to the above configuration, the configuration of the pressure reducing section 30 can be simplified.

[0095] In this embodiment, the cooling system 1 further includes a circulation system temperature sensor 4, a circulation system pressure sensor 5, and a pressure reduction control unit 50. The circulation system temperature sensor 4 measures the temperature in the circulation system 20. The circulation system pressure sensor 5 measures the pressure in the circulation system 20. The pressure reduction control unit 50 controls the pressure reduction unit 30. The pressure reduction control unit 50 includes a circulation system temperature acquisition unit 51, a circulation system pressure acquisition unit 52, a saturation pressure calculation unit 53, and a pressure reduction operation unit 55. The circulation system temperature acquisition unit 51 acquires the temperature measured by the circulation system temperature sensor 4. The circulation system pressure acquisition unit 52 acquires the pressure measured by the circulation system pressure sensor 5. The saturation pressure calculation unit 53 calculates the saturation pressure in the circulation system 20 from the temperature measured by the circulation system temperature sensor 4. When the pressure measured by the circulation system pressure sensor 5 is higher than the saturation pressure of the refrigerant R in the circulation system 20 calculated by the saturation pressure calculation unit 53, the pressure reduction operation unit 55 causes the pressure reduction unit 30 to reduce the pressure in the circulation system 20.

[0096] When the pressure in the circulation system 20 is higher than the saturation pressure of the refrigerant R, non-condensable gas is present in the circulation system 20. According to the above configuration, when the pressure in the circulation system 20 is higher than the saturation pressure of the refrigerant R, the decompression unit 30 decompresses the circulation system 20. Therefore, the decompression unit 30 can immediately remove the non-condensable gas that has entered the circulation system 20.

[0097] In this embodiment, the circulation system 20 includes a forced circulation line 27 and a forced circulation pump 28. The forced circulation line 27 branches off from the liquid line 24 and returns the refrigerant R to the cooling unit 21. The forced circulation pump 28 is provided in the forced circulation line 27 and can pump the refrigerant R to the cooling unit 21. The cooling system 1 further includes a switching mechanism 40. The switching mechanism 40 can switch the flow path of the refrigerant R between a flow path in which the refrigerant R does not pass through the forced circulation line 27 and a flow path in which the refrigerant R passes through the forced circulation line 27.

[0098] This allows the cooling system 1 to appropriately select between a method of naturally circulating the refrigerant R within the circulation system 20 using only the heat of the heating element 3c, and a method of forcibly circulating the refrigerant R within the circulation system 20 using the pumping force of the forced circulation pump 28.

[0099] In this embodiment, the cooling system 1 further includes a heat generation temperature sensor 6 and a forced circulation control unit 60. The heat generation temperature sensor 6 measures the temperature of the heat generating element 3c. The forced circulation control unit 60 forcibly circulates the refrigerant R within the circulation system 20. The forced circulation control unit 60 includes a heat generation temperature acquisition unit 61 and a forced circulation operation unit 63. The heat generation temperature acquisition unit 61 acquires the temperature measured by the heat generation temperature sensor 6. If the temperature measured by the heat generation temperature sensor 6 is higher than a predetermined temperature, the forced circulation operation unit 63 causes the switching mechanism 40 to switch the flow path of the refrigerant R to a flow path in which at least a portion of the refrigerant R passes through the forced circulation line 27, and operates the forced circulation pump 28.

[0100] As a result, when the temperature of the heat generating element 3c is high, the cooling system 1 can increase the amount of refrigerant R supplied to the cooling unit 21 by the forced circulation pump 28.

[0101] In this embodiment, the cooling system 1 further includes a power supply unit 10. The power supply unit 10 generates electricity using the temperature difference between the heating element 3c and the cooling unit 21, and supplies the electricity to the forced circulation pump .

[0102] As a result, the cooling system 1 can cover part of the power required to drive the forced circulation pump 28 with energy obtained from the temperature difference between the heating element 3c and the cooling unit 21. This allows for a reduction in the energy required to operate the cooling system 1.

[0103] In this embodiment, the heat exchange unit 22 removes heat from the refrigerant R by performing heat exchange between the refrigerant R and air outside the heat exchange unit 22. The cooling system 1 further includes a duct 11. The duct 11 has a lower opening 11a that opens downward and an upper opening 11b that opens upward. The heat exchange unit 22 is disposed inside the lower opening 11a. The duct 11 discharges air around the heat exchange unit 22 upward.

[0104] As a result, the air around the heat exchanger 22 is heated by the heat exchanger 22. This generates an upward flow in the duct 11. This upward flow supplies air to the heat exchanger 22. Therefore, the heat exchanger 22 can air-cool the refrigerant R efficiently.

[0105] In this embodiment, the cooling system 1 includes a second cooling unit 26 disposed in the refrigerant tank 25. The second cooling unit 26 cools the refrigerant R.

[0106] As a result, for example, when non-condensable gas is mixed in the refrigerant R, the non-condensable gas can be easily separated from the refrigerant R by cooling the refrigerant R with the second cooling unit 26. Therefore, the cooling system 1 can efficiently remove the non-condensable gas from the distribution system 20.

[0107] In this embodiment, the forced circulation pump 28 also functions as a drive pump 35 and circulates the drive fluid L within the decompression unit 33 .

[0108] This allows one pump to function as both the forced circulation pump 28 and the drive pump 35, thereby reducing the installation space for the cooling system 1.

[0109] Second Embodiment A cooling system 201 according to a second embodiment of the present disclosure will be described below with reference to FIG. 8 . Configurations common to the above-described embodiments will be designated by the same names and reference numerals, and descriptions thereof will be omitted as appropriate. As shown in FIG. 8 , a server rack 2 can accommodate multiple servers 3 therein. A plurality of servers 3 are accommodated in the server rack 2, lined up in the vertical direction Dv. A plurality of heating elements 3c are provided on the server boards 3b, extending in the horizontal direction. For simplification, FIG. 8 illustrates a case in which one heating element 3c is provided for each server board 3b. The number of heating elements 3c provided on one server board 3b can be changed as appropriate.

[0110] There are provided a plurality of cooling units 21. The cooling units 21 are attached to the plurality of heat generating elements 3c, respectively.

[0111] The gas line 23 includes one main gas line 23a extending from the heat exchange unit 22 and gas branch lines 23b branching from the main gas line 23a. The number of the gas branch lines 23b is the same as the number of the cooling units 21. The gas branch lines 23b are connected to the corresponding cooling units 21.

[0112] The liquid line 24 has one main liquid line 24a extending from the heat exchange unit 22 and branch liquid lines 24b branching from the main liquid line 24a. The branch liquid lines 24b are provided in the same number as the cooling units 21. The branch liquid lines 24b are connected to the corresponding cooling units 21. In this embodiment, the first valve 41 is provided in the main liquid line 24a.

[0113] The number of power supply units 10 provided is the same as the number of cooling units 21. The power supply units 10 are capable of supplying power to the forced circulation pump 28 (drive pump 35).

[0114] (Operations and Effects) According to the cooling system 201 of this embodiment, in addition to the same operations and effects as those of the first embodiment, the following operations and effects can be achieved.

[0115] In this embodiment, the flow system 20 has a plurality of cooling units 21 .

[0116] This can improve the cooling efficiency of the circulation system 20. For example, by attaching one heat generating element 3 c to each of the plurality of cooling units 21, the cooling system 201 can cool the plurality of heat generating elements 3 c with one circulation system 20.

[0117] Third Embodiment A cooling system 301 according to a third embodiment of the present disclosure will be described below with reference to Fig. 9 . Configurations common to the above-described embodiments will be designated by the same names and reference numerals, and descriptions thereof will be omitted as appropriate. As shown in Fig. 9 , in this embodiment, a plurality of circulation systems 20 are provided. Only one decompression unit 30 is provided for each of the plurality of circulation systems 20. This single decompression unit 30 decompresses each of the plurality of circulation systems 20 by removing gas from each of the plurality of circulation systems 20.

[0118] The gas removal line 31 has one gas removal main line 31a extending from the decompression unit 33 and gas removal branch lines 31b branching from the gas removal main line 31a. The number of gas removal branch lines 31b provided is the same as the number of circulation systems 20. The gas removal branch lines 31b are connected to the corresponding circulation systems 20.

[0119] In this embodiment, the decompression unit 33 is installed outside the server rack 2. In addition, the drive pump 35 in this embodiment is a pump separate from the forced circulation pump 28. The drive fluid supply line 36 and the drive fluid return line 37 are directly connected to the drive pump 35.

[0120] (Operations and Effects) According to the cooling system 301 of this embodiment, in addition to the same operations and effects as those of the first embodiment, the following operations and effects can be achieved.

[0121] In this embodiment, a plurality of circulation systems 20 are provided. The decompression unit 30 decompresses each of the plurality of circulation systems 20 by removing gas from each of the circulation systems 20.

[0122] As a result, the cooling system 301 can depressurize a plurality of circulation systems 20 with one depressurization unit 30 .

[0123] Fourth Embodiment A cooling system 401 according to a fourth embodiment of the present disclosure will be described below with reference to FIG. 9 . Components common to the above-described embodiments will be designated by the same names and reference numerals, and descriptions thereof will be omitted as appropriate. As shown in FIG. 9 , in this embodiment, similar to the third embodiment, a plurality of circulation systems 20 are provided, and only one pressure reducing unit 30 is provided for each of the plurality of circulation systems 20. Furthermore, similar to the second embodiment, each circulation system 20 has a plurality of cooling units 21. Furthermore, a plurality of power supply units 10 are provided, the same number as the cooling units 21.

[0124] (Operations and Effects) According to the cooling system 401 of this embodiment, it is possible to achieve the same operations and effects as those of the first to third embodiments.

[0125] (Hardware Configuration) The control device 12 of the above-described embodiments is implemented in a computer as shown in Fig. 11. Fig. 11 is an example of a schematic block diagram showing the configuration of a computer in which the control device 12 according to each embodiment is implemented. The computer 1100 includes a processor 1110, a main memory 1120, a storage 1130, and an interface 1140.

[0126] The operation of each functional unit of the control device 12 is stored in the form of a program in the storage 1130. The processor 1110 reads the program from the storage 1130, loads it into the main memory 1120, and executes the above-described processing in accordance with the program. The processor 1110 also allocates a storage area in the main memory 1120 in accordance with the program.

[0127] The program may be for realizing some of the functions to be performed by the computer 1100. For example, the program may be combined with other programs already stored in the storage 1130 or other programs implemented in other devices to perform the functions. Furthermore, the computer 1100 may include a custom large-scale integrated circuit (LSI) such as a programmable logic device (PLD) in addition to or instead of the above configuration. Examples of PLDs include programmable array logic (PAL), generic array logic (GAL), complex programmable logic device (CPLD), and field programmable gate array (FPGA). In this case, some or all of the functions realized by the processor 1110 may be realized by the integrated circuit.

[0128] 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. Furthermore, when this program is distributed to computer 1100 via a communication line, computer 1100 that receives the program may load the program into main memory 1120 and execute the above-mentioned processing. Storage 1130 may also be a non-transitory tangible storage medium.

[0129] The program may also be a program for realizing part of the above-described functions. Furthermore, the program may be a so-called differential file (differential program) that realizes the above-described functions in combination with another program already stored in storage 1130.

[0130] While the embodiments of the present disclosure have been described above in detail with reference to the drawings, the specific configuration is not limited to the embodiments, and design changes and the like are also included within the scope of the present disclosure. Note that, although the refrigerant R is water in the above embodiments, it is not limited to this.

[0131] In the above embodiment, the cooling unit 21 is a box-shaped cold plate formed so that the refrigerant R can flow therethrough, but the present invention is not limited to this. The cooling unit 21 may be any container that can be attached to the heating element 3c and that can boil the refrigerant R using the heat of the heating element 3c.

[0132] In the above embodiment, the decompression section 30 includes the gas removal line 31, the gas removal valve 32, and the decompression unit 33. However, the present invention is not limited to this. The decompression section 30 may be configured to remove gas from the circulation system 20 and reduce the pressure in the circulation system 20. For example, the decompression section 30 may be configured with the gas removal line 31 and a pump that sucks gas from the circulation system 20 via the gas removal line 31.

[0133] In the above embodiment, the driving fluid L is water, which is the same as the refrigerant R, but this is not limiting. The driving fluid L may be a fluid other than water, such as air.

[0134] In the above embodiment, the pressure reducing unit 30 is connected to the highest position in the flow system 20, but this is not limiting. The pressure reducing unit 30 may be connected to the gas line 23 or the liquid line 24 in the flow system 20.

[0135] <Additional Notes> The cooling systems 1, 201, 301, and 401 described in the respective embodiments can be understood, for example, as follows.

[0136] (1) A cooling system 1, 201, 301, 401 according to a first aspect includes a circulation system 20 through which a refrigerant R for cooling a heat-generating element 3 c flows, and a pressure reducing unit 30 connected to the circulation system 20. The circulation system 20 includes a cooling unit 21 attached to the heat-generating element 3 c and configured to remove heat from the heat-generating element 3 c by boiling the refrigerant R, a heat exchange unit 22 provided at a position higher than the cooling unit 21 and configured to condense the gaseous refrigerant R, a gas line 23 leading the refrigerant R evaporated in the cooling unit 21 to the heat exchange unit 22, and a liquid line 24 leading the refrigerant R condensed in the heat exchange unit 22 to the cooling unit 21. The pressure reducing unit 30 reduces the pressure of the circulation system 20 by removing gas from the circulation system 20. An example of the refrigerant R is a refrigerant that does not fall under the PFAS category, such as water.

[0137] According to the above configuration, the cooling systems 1, 201, 301, and 401 can reduce the pressure inside the circulation system 20 and place it in a low-pressure state below atmospheric pressure. This lowers the boiling point of the refrigerant R. As a result, the cooling system 1 can boil the refrigerant R in the cooling unit 21 at a lower temperature than before the pressure reduction. This allows the cooling system 1 to efficiently cool the heat-generating element 3c. Furthermore, because the pressure inside the circulation system 20 is negative, even if the circulation system 20 is damaged, air is drawn into the circulation system 20. This flow of drawn air prevents the refrigerant R from leaking to the outside. Furthermore, even if non-condensable gases are mixed into the circulation system 20, the pressure reduction unit 30 can remove the non-condensable gases.

[0138] (2) The cooling systems 1, 201, 301, and 401 of the second aspect are the cooling systems 1, 201, 301, and 401 of (1), and the pressure reducing section 30 may be connected to the highest position in the circulation system 20.

[0139] When non-condensable gas is mixed in the circulation system 20, the non-condensable gas tends to accumulate in the upper part of the circulation system 20. According to the above configuration, the pressure reducing section 30 can efficiently remove the non-condensable gas that has accumulated in the upper part of the circulation system 20.

[0140] (3) The cooling system 1, 201, 301, 401 of a third aspect may be the cooling system 1, 201, 301, 401 of (1) or (2), in which the pressure reducing unit 30 may include: a gas vent line 31 connected to the circulation system 20 and venting gas from the circulation system 20; an ejector 34 connected to the gas vent line 31 and sucking gas from the gas vent line 31 by the flow of driving fluid L circulating therethrough; a drive pump 35 supplying the driving fluid L to the ejector 34; a driving fluid supply line 36 directing the driving fluid L from the drive pump 35 to the ejector 34; a driving fluid return line 37 returning the driving fluid L discharged from the ejector 34 to the drive pump 35; and a driving fluid tank 38 provided on the driving fluid return line 37 and capable of storing the driving fluid L. Examples of the driving fluid L include water and air.

[0141] According to the above configuration, the configuration of the pressure reducing section 30 can be simplified.

[0142] (4) The cooling system 1, 201, 301, 401 of a fourth aspect is the cooling system 1, 201, 301, 401 of any one of (1) to (3), and further includes a circulation system temperature sensor 4 that measures the temperature in the circulation system 20, a circulation system pressure sensor 5 that measures the pressure in the circulation system 20, and a pressure reduction control unit 50 that controls the pressure reduction unit 30. The pressure reduction control unit 50 may include a circulation system temperature acquisition unit 51 that acquires the temperature measured by the circulation system temperature sensor 4, a circulation system pressure acquisition unit 52 that acquires the pressure measured by the circulation system pressure sensor 5, a saturation pressure calculation unit 53 that calculates the saturation pressure in the circulation system 20 from the temperature measured by the circulation system temperature sensor 4, and a pressure reduction operation unit 55 that causes the pressure reduction unit 30 to reduce the pressure in the circulation system 20 when the pressure measured by the circulation system pressure sensor 5 is higher than the saturation pressure of the refrigerant R in the circulation system 20 calculated by the saturation pressure calculation unit 53.

[0143] When the pressure in the circulation system 20 is higher than the saturation pressure of the refrigerant R, non-condensable gas is present in the circulation system 20. According to the above configuration, when the pressure in the circulation system 20 is higher than the saturation pressure of the refrigerant R, the decompression unit 30 decompresses the circulation system 20. Therefore, the decompression unit 30 can immediately remove the non-condensable gas that has entered the circulation system 20.

[0144] (5) A fifth aspect of the cooling system 1, 201, 301, 401 is a cooling system 1, 201, 301, 401 of any one of (1) to (4), wherein the circulation system 20 comprises a forced circulation line 27 that branches off from the liquid line 24 and returns the refrigerant R to the cooling section 21, and a forced circulation pump 28 that is provided in the forced circulation line 27 and is capable of pumping the refrigerant R to the cooling section 21, and may further comprise a switching mechanism 40 that can switch the flow path of the refrigerant R between a flow path in which the refrigerant R does not pass through the forced circulation line 27 and a flow path in which the refrigerant R passes through the forced circulation line 27.

[0145] As a result, the cooling systems 1, 201, 301, and 401 can appropriately select between a method of naturally circulating the refrigerant R within the circulation system 20 using only the heat of the heating element 3c, and a method of forcibly circulating the refrigerant R within the circulation system 20 using the pumping force of the forced circulation pump 28.

[0146] (6) The cooling system 1, 201, 301, 401 of a fifth aspect is the cooling system 1, 201, 301, 401 of (5), and further includes a heat generation temperature sensor 6 that measures the temperature of the heat generating element 3c, and a forced circulation control unit 60 that forcibly circulates the refrigerant R within the circulation system 20, and the forced circulation control unit 60 may include a heat generation temperature acquisition unit 61 that acquires the temperature measured by the heat generation temperature sensor 6, and a forced circulation operation unit 63 that, when the temperature measured by the heat generation temperature sensor 6 is higher than a predetermined temperature, causes the switching mechanism 40 to switch the flow path of the refrigerant R to a flow path through which at least a portion of the refrigerant R passes through the forced circulation line 27, and operates the forced circulation pump 28.

[0147] As a result, in the cooling systems 1, 201, 301, and 401, when the temperature of the heat generating element 3c is high, the forced circulation pump 28 can increase the amount of refrigerant R supplied to the cooling unit 21.

[0148] (7) The cooling system 1, 201, 301, 401 of the seventh aspect may be the cooling system 1, 201, 301, 401 of (5) or (6), and may further include a power supply unit 10 that generates electricity using the temperature difference between the heating element 3c and the cooling unit 21 and supplies power to the forced circulation pump 28.

[0149] As a result, the cooling systems 1, 201, 301, and 401 can cover part of the power required to drive the forced circulation pump 28 with energy obtained from the temperature difference between the heating element 3c and the cooling section 21.

[0150] (8) The cooling system 1, 201, 301, 401 of the eighth aspect is any one of the cooling systems 1, 201, 301, 401 of (1) to (7), wherein the heat exchange unit 22 removes heat from the refrigerant R by performing heat exchange between the refrigerant R and the air outside the heat exchange unit 22, and the heat exchange unit 22 is disposed inside and has a lower opening 11a that opens downward and an upper opening 11b that opens upward, and may further include a duct 11 that discharges the air around the heat exchange unit 22 upward.

[0151] As a result, the air around the heat exchanger 22 is heated by the heat exchanger 22. This generates an upward flow in the duct 11. This upward flow supplies air to the heat exchanger 22. Therefore, the heat exchanger 22 can air-cool the refrigerant R efficiently.

[0152] (9) The cooling system 201, 401 of a ninth aspect is the cooling system 201, 401 of any one of (1) to (8), in which the circulation system 20 may have a plurality of the cooling units 21.

[0153] This can improve the cooling efficiency of the circulation system 20. For example, by attaching one heat generating element 3 c to each of the plurality of cooling units 21, the cooling systems 201, 401 can cool the plurality of heat generating elements 3 c with one circulation system 20.

[0154] (10) The cooling system 301, 401 of the tenth aspect is any one of the cooling systems 301, 401 of (1) to (9), in which a plurality of the circulation systems 20 are provided, and the pressure reduction section 30 may reduce the pressure of each of the circulation systems 20 by removing gas from each of the plurality of circulation systems 20.

[0155] As a result, the cooling systems 301 and 401 can depressurize a plurality of circulation systems 20 with one depressurization unit 30 .

[0156] According to the cooling system of the present disclosure, the cooling efficiency can be improved.

[0157] DESCRIPTION OF SYMBOLS 1...Cooling system 2...Server rack 3...Server 3a...Casing 3b...Server board 3c...Heat generating element 4...Circulation system temperature sensor 5...Circulation system pressure sensor 6...Heat generating temperature sensor 7...Decompression section pressure sensor 8...Level sensor 9...Refrigerant return line 9a...Refrigerant return valve 9b...Refrigerant return pump 10...Power supply section 11...Duct 11a...Lower opening 11b...Upper opening 11c...Cylinder section 12...Control device 20...Circulation system 21...Cooling section 22...Heat exchange section 23...Gas line 23a...Gas main line 23b...Gas branch line 24...Liquid line 24a...Liquid main line 24b...Liquid branch line 25...Refrigerant tank 26...Second cooling section 27...Forced circulation line 28...Forced circulation pump 30...Decompression section 31...Gas removal line 31a...Gas removal main line 31b...Gas removal branch line 32...Gas removal valve 33...Decompression unit 34...Ejector 34a...Supply section 34b...Discharge section 34c...Suction section 35...Drive pump 36...Drive fluid supply line 37...Drive fluid return line 38...Drive fluid tank 39...Atmospheric release line 39a...Atmospheric release valve 40...Switching mechanism 41...First valve 42...Second valve 43...Third valve 44...Fourth valve 45...Fifth valve 50...Decompression control section 51...Circulation system temperature acquisition section 52...Circulation system pressure acquisition section 53...Saturation pressure calculation section 54...Circulation system pressure determination section 55...Decompression operation section 60...Forced circulation control section 61...Heat generation temperature acquisition section 62...Heat generation temperature determination section 63...Forced circulation operation section 64...Flow rate adjustment section 70...Atmospheric release control section 71...Pressure acquisition section within decompression section 72: Pressure reducing section internal pressure determination section 73: Atmospheric release operation section 80: Refrigerant return control section 81: Liquid level detection information acquisition section 82: Refrigerant return operation section Dv: Up and down direction R: Refrigerant L: Driving fluid 201: Cooling system 301: Cooling system 401: Cooling system 1100: Computer 1110: Processor 1120: Main memory 1130: Storage 1140: Interface

Claims

1. A cooling system comprising: a circulation system through which a refrigerant for cooling a heat-generating element circulates; and a pressure reducing unit connected to the circulation system, wherein the circulation system comprises: a cooling unit attached to the heat-generating element and removing heat from the heat-generating element by boiling the refrigerant; a heat exchange unit located higher than the cooling unit and condensing the gaseous refrigerant; a gas line leading the refrigerant evaporated in the cooling unit to the heat exchange unit; and a liquid line leading the refrigerant condensed in the heat exchange unit to the cooling unit, wherein the pressure reducing unit reduces the pressure of the circulation system by removing gas from within the circulation system.

2. The cooling system according to claim 1, wherein the pressure reducing section is connected to the highest position in the circulation system.

3. The cooling system of claim 1 or 2, wherein the pressure reducing section comprises: a gas vent line connected to the circulation system for venting gas from the circulation system; an ejector connected to the gas vent line for sucking gas from the gas vent line by the flow of driving fluid circulating therethrough; a drive pump for supplying the driving fluid to the ejector; a drive fluid supply line for guiding the driving fluid from the drive pump to the ejector; a drive fluid return line for returning the driving fluid discharged from the ejector to the drive pump; and a drive fluid tank provided in the drive fluid return line for storing the driving fluid.

4. The cooling system according to claim 1 or 2, further comprising: a distribution system temperature sensor that measures the temperature in the distribution system; a distribution system pressure sensor that measures the pressure in the distribution system; and a pressure reduction control unit that controls the pressure reduction unit, wherein the pressure reduction control unit comprises: a distribution system temperature acquisition unit that acquires the temperature measured by the distribution system temperature sensor; a distribution system pressure acquisition unit that acquires the pressure measured by the distribution system pressure sensor; a saturation pressure calculation unit that calculates the saturation pressure in the distribution system from the temperature measured by the distribution system temperature sensor; and a pressure reduction operation unit that causes the pressure reduction unit to reduce the pressure in the distribution system when the pressure measured by the distribution system pressure sensor is higher than the saturation pressure of the refrigerant in the distribution system calculated by the saturation pressure calculation unit.

5. A cooling system as described in claim 1 or 2, wherein the circulation system comprises: a forced circulation line branching off from the liquid line and returning the refrigerant to the cooling section; and a forced circulation pump provided on the forced circulation line and capable of pumping the refrigerant to the cooling section; and further comprising a switching mechanism capable of switching the flow path of the refrigerant between a flow path in which the refrigerant does not pass through the forced circulation line and a flow path in which the refrigerant passes through the forced circulation line.

6. A cooling system as described in claim 5, further comprising: a heat generation temperature sensor that measures the temperature of the heat generating element; and a forced circulation control unit that forcibly circulates the refrigerant within the circulation system, wherein the forced circulation control unit comprises: a heat generation temperature acquisition unit that acquires the temperature measured by the heat generation temperature sensor; and a forced circulation operation unit that, when the temperature measured by the heat generation temperature sensor is higher than a predetermined temperature, causes the switching mechanism to switch the flow path of the refrigerant to a flow path in which at least a portion of the refrigerant passes through the forced circulation line, and operates the forced circulation pump.

7. The cooling system according to claim 5, further comprising a power supply unit that generates electricity using the temperature difference between the heating element and the cooling unit and supplies power to the forced circulation pump.

8. A cooling system as claimed in claim 1 or 2, wherein the heat exchange unit removes heat from the refrigerant by exchanging heat between the refrigerant and air outside the heat exchange unit, the heat exchange unit is disposed inside the heat exchange unit, the heat exchange unit has a lower opening that opens downward and an upper opening that opens upward, and the system further comprises a duct that discharges air around the heat exchange unit upward.

9. The cooling system according to claim 1 or 2, wherein the circulation system has a plurality of the cooling units.

10. The cooling system according to claim 1 or 2, wherein a plurality of the circulation systems are provided, and the pressure reducing unit reduces the pressure in each of the plurality of circulation systems by removing gas from each of the circulation systems.

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