Immersion cooling system and removal method

Abstract

To provide a liquid immersion cooling system and a removal method, capable of highly efficiently removing impurities in a coolant.SOLUTION: A liquid immersion cooling system for cooling a heat generator provided to a substrate, comprises: a cooler main body including a casing which accommodates the substrate and the heat generator inside and also retains a coolant for cooling the heat generator; a circulation passage to which both ends are connected so as to communication state into the casing; a sorption part that is provided in the circulation passage and sorbs impurities from the coolant flowing in the circulation passage; a pump that makes the coolant pass through the circulation passage; and a control device that controls the pump. The control device comprises: a temperature drop detection part that detects drops in temperature of the coolant in the casing; and a pump driving part that drives the pump on the basis of the detection by the temperature drop detection part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an immersion cooling system and removal method. [Background technology]

[0002] Patent Document 1 discloses a method for recovering a refrigerant used in immersion cooling. In this refrigerant recovery method, the refrigerant is distilled in a distillation tank to separate less volatile contaminants from the refrigerant. The distilled refrigerant is then recovered in a circulation tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 10,773,192 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology described in Patent Document 1, impurities such as oil are continuously removed from the refrigerant during operation of the immersion cooling device to prevent the precipitation of impurities in the refrigerant. This causes impurities to continuously leach out from cables and other devices immersed in the refrigerant, accelerating their deterioration. Furthermore, continuous removal of impurities requires the continuous operation of pumps and other devices, which increases costs for electricity and other expenses. For this reason, there has been a demand for the development of a technology that can efficiently remove impurities from the refrigerant.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an immersion cooling system and a removal method that can efficiently remove impurities from a refrigerant. [Means for solving the problem]

[0006] In order to solve the above problems, the immersion cooling system according to the present disclosure is an immersion cooling system that cools a heat-generating element provided on a substrate, and includes: a cooling device main body having a casing that houses the substrate and the heat-generating element and stores a coolant for cooling the heat-generating element; a circulation flow path that is connected to the casing at both ends in communication; an adsorption unit that is provided in the circulation flow path and adsorbs impurities from the coolant circulating within the circulation flow path; a pump that circulates the coolant through the circulation flow path; and a control device that controls the pump, wherein the control device includes a temperature drop detection unit that detects a drop in the temperature of the coolant in the casing, and a pump drive unit that drives the pump based on detection by the temperature drop detection unit.

[0007] The removal method according to the present disclosure is a removal method for removing impurities from a coolant used in an immersion cooling system that cools a heat generating element provided on a substrate, the immersion cooling system comprising: a cooling device main body having a casing that houses the substrate and the heat generating element and stores the coolant; a circulation flow path that is connected to the casing at both ends; an adsorption section that is provided in the circulation flow path and adsorbs the impurities from the coolant circulating within the circulation flow path; and a pump that circulates the coolant through the circulation flow path, and includes the steps of detecting a decrease in temperature of the coolant in the casing; and driving the pump based on the detection of a decrease in temperature of the coolant in the casing. [Effects of the Invention]

[0008] According to the immersion cooling system and removal method of the present disclosure, impurities in the refrigerant can be efficiently removed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a configuration diagram of an immersion cooling system according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a functional block diagram of a control device according to the first embodiment of the present disclosure. [Figure 3]1 is a flowchart showing the flow of a removal method according to a first embodiment of the present disclosure. [Figure 4] 1 is a graph showing the temperature dependence of the solubility of impurities according to the first embodiment of the present disclosure. [Figure 5] 1 is a graph showing the adsorption capacity of an adsorbent according to a first embodiment of the present disclosure. [Figure 6] 4 is a graph showing a decrease in impurity concentration by driving a pump according to the first embodiment of the present disclosure. [Figure 7] FIG. 4 is a functional block diagram of a control device according to a first modified example of the first embodiment of the present disclosure. [Figure 8] 10 is a flowchart showing the flow of a removal method according to a first modified example of the first embodiment of the present disclosure. [Figure 9] FIG. 10 is a configuration diagram of an immersion cooling system according to a second modified example of the first embodiment of the present disclosure. [Figure 10] FIG. 10 is a functional block diagram of a control device according to a second modified example of the first embodiment of the present disclosure. [Figure 11] 10 is a flowchart showing the flow of a removal method according to a second modified example of the first embodiment of the present disclosure. [Figure 12] FIG. 10 is a configuration diagram of an immersion cooling system according to a second embodiment of the present disclosure. [Figure 13] FIG. 10 is a functional block diagram of a control device according to a second embodiment of the present disclosure. [Figure 14] 10 is a flowchart showing the flow of a removal method according to a second embodiment of the present disclosure. [Figure 15] FIG. 10 is a functional block diagram of a control device according to a modified example of the second embodiment of the present disclosure. [Figure 16] 10 is a flowchart showing the flow of a removal method according to a modified example of the second embodiment of the present disclosure. [Figure 17] FIG. 2 is a hardware configuration diagram illustrating the configuration of a computer according to each embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] First Embodiment (Liquid immersion cooling device) An immersion cooling system 10 and a removal method according to a first embodiment of the present disclosure will now be described with reference to FIGS. 1, an immersion cooling system 10 is used to cool electronic devices. In this embodiment, the immersion cooling system 10 is used in a server 1 that performs high-speed calculations.

[0011] The server 1 has a printed circuit board and electronic components such as CPU and GPU chips mounted on the printed circuit board. The CPU and GPU are components that handle high-speed calculations and are therefore subject to high loads. For this reason, the CPU and GPU generate heat at higher temperatures than other parts of the server 1.

[0012] Hereinafter, the printed circuit board of the server 1 may be simply referred to as the "board 2," and the chips such as the CPU and GPU may be referred to as the "heat generating element 3."

[0013] The substrate 2 is formed in a rectangular plate shape and is disposed vertically so as to extend in the vertical direction.

[0014] The heating element 3 is attached to the surface of the substrate 2. Therefore, in this embodiment, the heating element 3 is disposed vertically so as to extend in the vertical direction, similar to the substrate 2.

[0015] The heating element 3 is supplied with power from a power supply 4 external to the server 1. The power supply 4 is connected to the board 2 by a power cable 5. The heating element 3 is electrically connected to the power supply 4 via the power cable 5 and the board 2. The board 2 is also connected to an external device (not shown) by a communication cable 7. The communication cable 7 is, for example, a LAN cable. The server 1 communicates with the external device through the communication cable 7.

[0016] (Configuration of immersion cooling system) Next, the configuration of the immersion cooling system 10 will be described. The immersion cooling system 10 is an apparatus for cooling the heat-generating element 3 by immersing the substrate 2 and the heat-generating element 3 in a liquid-phase refrigerant R and causing heat exchange between the liquid-phase refrigerant R and the heat-generating element 3. The refrigerant R used in this immersion cooling system 10 is an insulating fluid. As shown in FIG. 1, the immersion cooling system 10 includes a cooling device 20, a circulation channel 11, an adsorption unit 12, a pump 13, and a control device 30.

[0017] (cooling device) The cooling device 20 includes a cooling device main body 21 and a condenser section 22. The cooling device main body 21 has a casing 23.

[0018] (Casing) The casing 23 accommodates the substrate 2 and the heating element 3 inside. A liquid-phase coolant R is stored in the lower inside portion of the casing 23. In this embodiment, the entire substrate 2 is immersed in the liquid-phase coolant R stored in the casing 23. In this embodiment, as an example, a case will be described in which the casing 23 has a lower casing 24, an upper casing 25, and a connecting wall 26.

[0019] The lower casing 24 is a container with a bottom that opens upward. The lower casing 24 is the portion of the casing 23 that stores the liquid phase refrigerant R. The upper casing 25 is provided above the lower casing 24. The upper casing 25 is a container with a bottom that opens downward. In this embodiment, the opening area of ​​the upper casing 25 is larger than the opening area of ​​the lower casing 24. The connecting wall 26 is formed to protrude horizontally outward from the opening of the lower casing 24. The connecting wall 26 connects the opening of the lower casing 24 and the opening of the upper casing 25.

[0020] A closed space is formed by the lower casing 24, the upper casing 25, and the connecting wall 26. The space inside this casing 23 accommodates the board 2, the power supply 4, the power cable 5, and the communication cable 7. The board 2 is disposed inside the lower casing 24. The board 2 is installed in a position floating above the bottom of the lower casing 24. The power supply 4 is installed on the connecting wall 26.

[0021] The heating element 3 is immersed in the liquid-phase refrigerant R stored in the casing 23. Therefore, while the heating element 3 is generating heat, heat is supplied from the heating element 3 to the liquid-phase refrigerant R, causing the temperature of the refrigerant R to rise. The temperature of the refrigerant R rises to its boiling point and becomes constant. After that, when the heating element 3 stops, the supply of heat from the heating element 3 to the refrigerant R inside the casing 23 stops. Then, the refrigerant R inside the casing 23 cools down by natural cooling. The temperature of the refrigerant R then drops to a predetermined temperature.

[0022] Furthermore, in addition to the liquid-phase refrigerant R stored in the lower casing 24, gas-phase refrigerant R also exists within the casing 23. This gas-phase refrigerant R condenses on the power source 4 and the power cable 5 and changes to a liquid phase. A portion of the power cable 5 is immersed in the refrigerant R within the casing 23. Furthermore, the cables inside the power source 4, the power cable 5, and the coatings of the communication cable 7 contain plasticizers. For this reason, this plasticizer may dissolve in the refrigerant R, and impurities such as the plasticizer may leach into the refrigerant R. The refrigerant R containing the eluted impurities is mixed into the refrigerant R stored within the casing 23 from the cables inside the power source 4, the power cable 5, and the communication cable 7. In this way, impurities become mixed into the refrigerant R within the casing 23.

[0023] For example, vinyl chloride is used for the coating of power cables. When vinyl chloride comes into contact with refrigerant R, oil components such as phthalate esters, which are plasticizers, are eluted into the refrigerant R. In other words, impurities in refrigerant R include oil components such as phthalate esters.

[0024] (Condenser) Condenser 22 is provided above the liquid level of refrigerant R in casing 23. Condenser 22 condenses evaporated refrigerant R in casing 23. Condenser 22 is attached to upper casing 25.

[0025] The condenser 22 of this embodiment is a water-cooled condenser. The condenser 22 has a plurality of heat transfer tubes 27. Cooling water W flows through the heat transfer tubes 27. The condenser 22 exchanges heat between the cooling water W and the gas-phase refrigerant R, condensing the refrigerant R.

[0026] (Circulation flow path) The circulation flow path 11 is provided outside the casing 23. The circulation flow path 11 is a pipe through which the refrigerant R flows. Both ends of the circulation flow path 11 are connected to the inside of the casing 23 in a communicating state. In this embodiment, both ends of the circulation flow path 11 are connected to a lower casing 24 of the casing 23. An adsorption unit 12 is provided in the circulation flow path 11.

[0027] (Adsorption part) The adsorption unit 12 adsorbs impurities from the refrigerant R circulating through the circulation flow path 11. In this embodiment, the adsorption unit 12 is an adsorption tower having an adsorbent 12a therein that adsorbs impurities. In this embodiment, the adsorbent 12a is activated carbon. The adsorbent 12a is provided in an amount necessary for the concentration of impurities in the refrigerant R, after the impurities have been adsorbed up to the upper limit of the adsorption capacity of the adsorbent 12a, to reach the solubility of the impurities in the refrigerant R after the temperature drop of the refrigerant R is completed. Note that "the impurity concentration reaches a target concentration, such as solubility" does not only mean that the impurity concentration and solubility exactly match, but also means that the impurity concentration and solubility are slightly different. A method for calculating the required amount of adsorbent 12a will be described in detail later.

[0028] (pump) The pump 13 is provided in the circulation flow path 11. The pump 13 pressure-feeds the refrigerant R in the circulation flow path 11 in one direction, causing the refrigerant R to circulate through the circulation flow path 11. In this embodiment, the pump 13 is disposed in the circulation flow path 11 upstream of the adsorption unit 12 in the flow direction of the refrigerant R. A control device 30 is connected to the pump 13.

[0029] (Control device) The control device 30 is a device that controls the driving of the pump 13 based on a decrease in temperature of the refrigerant R inside the casing 23. The control device 30 of this embodiment is connected to the heating element 3. As shown in FIG. 2 , the control device 30 includes a temperature decrease detection unit 31 and a pump driving unit 32.

[0030] (Temperature drop detection section) The temperature drop detection unit 31 detects a drop in the temperature of the refrigerant R inside the casing 23. In this embodiment, the temperature drop detection unit 31 detects the stop of the heating element 3, thereby detecting a drop in the temperature of the refrigerant R inside the casing 23.

[0031] (Pump drive unit) The pump driving unit 32 drives the pump 13 based on the detection by the temperature drop detection unit 31. In this embodiment, when the temperature drop detection unit 31 detects that the heating element 3 has stopped, the pump driving unit 32 drives the pump 13.

[0032] (Method for removing impurities) Incidentally, while the heating element 3 is generating heat, impurities dissolve from the power cable 5 and the like into the refrigerant R, and the impurities in the refrigerant R become saturated. The saturated state here includes not only the case where the concentration and solubility of the impurity exactly match, but also the case where the concentration and solubility of the impurity are slightly different. When the refrigerant R is cooled, the solubility of impurities in the refrigerant R decreases. As a result, impurities dissolved in the refrigerant R may precipitate due to the cooling of the refrigerant R. If impurities precipitate on the heating element 3 or substrate 2, which are the objects to be cooled, the precipitated impurities will hinder heat exchange between the refrigerant R and the heating element 3. For this reason, it is necessary to remove impurities to the extent that they do not precipitate on the heating element 3 or substrate 2 when the refrigerant R is cooled. A method for appropriately removing impurities from the refrigerant R will be described below with reference to FIG.

[0033] In this embodiment, the temperature drop detection unit 31 detects the stoppage of the heating element 3 (step S11), and thereby detects the drop in the temperature of the refrigerant R in the casing 23 (step S12).

[0034] Then, pump driving unit 32 drives pump 13 (step S13). When pump 13 drives, refrigerant R in casing 23 is drawn into circulation flow path 11. The refrigerant R drawn into circulation flow path 11 flows through circulation flow path 11 in the pumping direction of pump 13. As a result, refrigerant R circulates within a cycle of casing 23 and circulation flow path 11. While pump 13 is driving, refrigerant R passes through adsorbent 12a in adsorption unit 12. As refrigerant R passes through adsorbent 12a, impurities in refrigerant R are adsorbed by adsorbent 12a. In this way, impurities are removed from refrigerant R.

[0035] The flow rate and driving time of the pump 13 are set in the pump driving unit 32 before operation of the immersion cooling system 10. Setting the flow rate and driving time of the pump 13 will be described in detail later.

[0036] In step S13, pump 13 is driven until the concentration of impurities in refrigerant R in casing 23 reaches the solubility of the impurities after the temperature drop is completed. Thereafter, pump driving unit 32 stops pump 13 (step S14), and the removal of impurities from refrigerant R is completed.

[0037] (Calculation method for required amount of adsorbent) Next, a method for calculating the required amount of the adsorbent 12a will be described with reference to FIGS.

[0038] FIG. 4 is a graph showing the change in the solubility of impurities with temperature. The horizontal axis of FIG. 4 represents the refrigerant temperature [°C]. The horizontal axis of FIG. 4 represents the temperature of refrigerant R before cooling as t1 [°C], and the temperature of refrigerant R at the completion of cooling as t2 [°C]. The vertical axis of FIG. 4 represents the solubility of impurities [mg / L]. As shown in FIG. 4, the solubility of impurities in refrigerant R has a positive correlation with the temperature of refrigerant R. The data in FIG. 4 is obtained by a pre-test before the immersion cooling system 10 is put into operation.

[0039] Here, if the difference between the solubility of impurities at temperature t1 [°C] before cooling of refrigerant R and the solubility of impurities at temperature t2 [°C] when cooling of refrigerant R is completed (hereinafter referred to as removal target concentration d1 [mg / L]) is Y [mg / L], and the volume of refrigerant R in casing 23 is V [L], the amount of impurities to be removed α [mg] required to ensure that the concentration of impurities in refrigerant R reaches removal target concentration d1 [mg / L] is calculated using the following equation (1): α=Y·V…(1) The required amount of adsorbent 12a is calculated based on the value of α [mg] calculated by equation (1). Hereinafter, the calculation of the required amount of adsorbent 12a based on the value of α [mg] will be described with reference to FIG.

[0040] FIG. 5 is a graph showing the adsorption capacity of the adsorbent 12a. The horizontal axis of FIG. 5 represents the equilibrium concentration [mg / L] of the adsorbent dissolved in the solvent passing through the adsorbent 12a. The vertical axis of FIG. 5 represents the adsorption capacity [mg / g]. The adsorption capacity [mg / g] is the amount [mg] of the adsorbent adsorbed by 1 [g] of the adsorbent 12a. As shown in FIG. 5, the adsorption capacity [mg / g] has a positive correlation with the equilibrium concentration [mg / L] of the adsorbent dissolved in the solvent passing through the adsorbent 12a.

[0041] The graph in Fig. 5 is an adsorption isotherm obtained when the solvent is at temperature t2. Fig. 5 shows the adsorption capacity for various equilibrium concentrations [mg / L] of solutions that dissolve the adsorption target of the adsorbent 12a. The horizontal axis of Fig. 5 shows the target removal concentration d1 [mg / L]. The adsorption capacity X [mg / g] on the vertical axis of Fig. 5, which corresponds to the target removal concentration d1 [mg / L] on the horizontal axis of Fig. 5, is the adsorption capacity X [mg / g] for the impurities dissolved in the refrigerant R of this embodiment at temperature t2. 5. The data in FIG. 5, like the data in FIG. 4, is obtained by a pre-test before the immersion cooling system 10 is put into operation.

[0042] Here, if the required amount of adsorbent 12a is β [g], β [g] is calculated using the following formula (2) based on the amount of impurities removed α [mg] and the adsorption capacity X [mg / g]. β=α / X…(2)

[0043] In this way, the amount β [g] of adsorbent 12a required to bring the concentration of impurities in refrigerant R to the target removal concentration d1 [mg / L] can be calculated using simple equations (1) and (2) if the data in Figures 4 and 5 are obtained in advance.

[0044] (Pump flow rate and pump operating time settings) Next, the setting of the flow rate of the pump 13 and the driving time of the pump 13 will be described with reference to FIG. FIG. 6 is a graph showing the decrease in impurity concentration due to the operation of the pump 13. The horizontal axis of FIG. 6 shows the total amount of refrigerant R circulating through the adsorption section 12. The total amount of circulation is the product of the flow rate [L / min] of the pump 13 and the operation time [min] of the pump 13. The values ​​on the horizontal axis of FIG. 6 are normalized by dividing the total amount of circulation by the volume V1 [L] of the adsorbent 12a. The apparent density of the adsorbent 12a is expressed as ρ [g / cm 3 ], the volume V1 [L] of the adsorbent 12a is calculated by the following formula (3). V1=β / ρ / 1000…(3) 6 indicates the concentration of impurities in the refrigerant R [mg / L]. 6, like the data in FIGS. 4 and 5, is obtained by a pre-test before the immersion cooling system 10 is put into operation.

[0045] As shown in Fig. 6, as the total amount of circulating refrigerant R increases, the concentration of impurities in refrigerant R decreases and gradually approaches the removal target concentration d1 [mg / L]. Based on the data in Fig. 6, the flow rate of pump 13 and the drive time of pump 13 are set so that the concentration of impurities in refrigerant R reaches the removal target concentration d1 [mg / L].

[0046] (Action and effect) The immersion cooling system 10 of this embodiment provides the following advantageous effects. In this embodiment, the immersion cooling system 10 includes a circulation flow path 11, an adsorption unit 12, a pump 13, and a control device 30. The circulation flow path 11 is connected to the inside of a casing 23 with both ends communicating with each other. The adsorption unit 12 is provided in the circulation flow path 11 and adsorbs impurities from the refrigerant R circulating within the circulation flow path 11. The pump 13 circulates the refrigerant R through the circulation flow path 11. The control device 30 controls the pump 13. The control device 30 also includes a temperature drop detection unit 31 and a pump drive unit 32. The temperature drop detection unit 31 detects a drop in the temperature of the refrigerant R within the casing 23. The pump drive unit 32 drives the pump 13 based on the detection by the temperature drop detection unit 31.

[0047] This allows the immersion cooling system 10 to drive the pump 13 in accordance with the decrease in temperature of the refrigerant R in the casing 23. As a result, the refrigerant R in the casing 23 flows through the circulation flow path 11 and passes through the adsorption unit 12. The adsorption unit 12 adsorbs the impurities in the refrigerant R, thereby reducing the concentration of impurities in the refrigerant R in the casing 23. This suppresses the deposition of impurities due to the decrease in temperature of the refrigerant R in the casing 23. Furthermore, pump 13 is not driven except when the temperature of refrigerant R in casing 23 is decreasing, and refrigerant R in casing 23 is not supplied to adsorption unit 12. Therefore, except when the temperature of refrigerant R in casing 23 is decreasing, a decrease in the concentration of impurities in refrigerant R in casing 23 is suppressed, and the impurities in refrigerant R are maintained in a saturated state. Therefore, immersion cooling system 10 can suppress impurity precipitation due to a decrease in the temperature of refrigerant R, while also suppressing impurity elution from power cable 5 and the like immersed in refrigerant R. Therefore, immersion cooling system 10 can suppress deterioration of power cable 5 and the like. Furthermore, since there is no need to constantly drive pump 13, the power cost for operating pump 13 is reduced. Furthermore, because the operation of pump 13 is controlled by detecting a decrease in the temperature of refrigerant R, there is no need to provide multiple measuring instruments for optical transmittance, infrared spectroscopy, conductivity, etc. Furthermore, there is no need for a measuring instrument for measuring the impurity concentration in refrigerant R. This simplifies the operation control of immersion cooling system 10. In this way, the immersion cooling system 10 can efficiently remove impurities from the refrigerant R.

[0048] In this embodiment, the adsorption unit 12 has an adsorbent 12a that adsorbs impurities. The adsorbent 12a is provided in an amount necessary for the concentration of impurities in the refrigerant R, after the impurities have been adsorbed up to the upper limit of the adsorption capacity of the adsorbent 12a, to reach the solubility of the impurities in the refrigerant R after the temperature of the refrigerant R has been lowered.

[0049] As the pump 13 continues to supply the refrigerant R to the adsorbent 12a, the adsorbent 12a adsorbs impurities in the refrigerant R up to the upper limit of the adsorption amount. According to this embodiment, the immersion cooling system 10 can make the concentration of impurities in the refrigerant R reach the solubility of the impurities after the temperature of the refrigerant R in the casing 23 has been lowered, simply by driving the pump 13 until the upper limit of the adsorption amount of the adsorbent 12a is reached. This allows the immersion cooling system 10 to easily saturate the impurities in the refrigerant R even when the temperature of the refrigerant R is lowered. Therefore, the immersion cooling system 10 can easily and reliably prevent impurities from eluting from the power cable 5 or the like that is immersed in the refrigerant R.

[0050] In this embodiment, the temperature drop detection unit 31 detects the stoppage of the heating element 3. Furthermore, when the temperature drop detection unit 31 detects the stoppage of the heating element 3, the pump driving unit 32 drives the pump 13.

[0051] When the heating element 3 stops, heat is no longer supplied from the heating element 3 to the refrigerant R inside the casing 23, and the temperature of the refrigerant R drops. According to this embodiment, the temperature drop detection unit 31 can detect a temperature drop when the heating element 3 stops. This eliminates the need to provide a measuring instrument such as a temperature sensor to detect the temperature of the refrigerant R inside the casing 23. This further simplifies the operation control of the immersion cooling system 10.

[0052] <First Modification of First Embodiment> Next, a first modified example of the first embodiment will be described with reference to FIGS. As shown in FIG. 7, in an immersion cooling system 10A of this modified example, a control device 30A has a reservation stopping unit 31A, a temperature drop detection unit 32A, and a pump driving unit 33A.

[0053] The scheduled stop unit 31A stops the heating element 3 after a predetermined time has elapsed. The scheduled stop unit 31A sends a first reservation signal to the temperature drop detection unit 32A before stopping the heating element 3. The scheduled stop time for the heating element 3 may be set in the scheduled stop unit 31A every time the refrigerant R is cooled, or may be set when the immersion cooling system 10A is manufactured, or may be set when maintenance is performed on the immersion cooling system 10A.

[0054] Upon receiving the first reservation signal, the temperature drop detection unit 32A detects that the temperature of the refrigerant R in the casing 23 will drop in the future. When the temperature drop detection unit 32A receives the first reservation signal, the pump drive unit 33A drives the pump 13.

[0055] (Method for removing impurities) Next, the method for removing impurities according to this modified example will be described with reference to FIG. In this modification, first, the reservation stop unit 31A reserves the stop of the heating element 3 (step S11A). Then, the reservation stop unit 31A transmits a first reservation signal to the temperature drop detection unit 32A. Upon receiving the first reservation signal (step S12A), the temperature drop detection unit 32A detects a drop in the temperature of the refrigerant R in the casing 23 (step S13A).

[0056] Then, pump driving unit 33A drives pump 13 (step S14A). As a result, refrigerant R circulates within the cycle of casing 23 and circulation flow path 11, and impurities in refrigerant R are removed by adsorbent 12a. Thereafter, pump driving unit 33A stops pump 13 (step S15A), and the removal of impurities in refrigerant R is completed.

[0057] The removal of impurities is initiated before the temperature of refrigerant R is reduced. The removal of impurities may be completed while the temperature of refrigerant R is being reduced, but it is desirable that the removal of impurities be completed before the temperature of refrigerant R is reduced.

[0058] (Action and effect) The immersion cooling system 10A of this modified example provides the following advantageous effects. In this modified example, the control device 30A further includes a reservation stop unit 31A. The reservation stop unit 31A stops the heating element 3 after a predetermined time has elapsed, and sends a first reservation signal to the temperature drop detection unit 32A before the heating element 3 is stopped. By receiving the first reservation signal, the temperature drop detection unit 32A detects that the temperature of the refrigerant R in the casing 23 will drop in the future. When the temperature drop detection unit 32A receives the first reservation signal, the pump drive unit 33A drives the pump 13.

[0059] As a result, before the temperature of the refrigerant R drops, the immersion cooling system 10A can drive the pump 13 to remove impurities from the refrigerant R inside the casing 23. Therefore, the immersion cooling system 10A can more reliably suppress the precipitation of impurities due to a drop in the temperature of the refrigerant R.

[0060] The control device 30A of this modified example may use both a method in which the temperature drop detection unit 32A detects a stop of the invention, thereby detecting a drop in the temperature of the refrigerant R, and then drives the pump 13 (the method disclosed in the flow chart of FIG. 3), and a method in which the temperature drop detection unit 32A detects a drop in the temperature of the refrigerant R when it receives a first reservation signal (the method disclosed in the flow chart of FIG. 8). In this case, the user of the control device 30A can select which of the above methods to drive the pump 13.

[0061] <Second Modification of First Embodiment> Next, a second modified example of the first embodiment will be described with reference to FIGS. As shown in FIG. 9, the immersion cooling system 10B of this modified example further includes a heating element temperature sensor 6. The heating element temperature sensor 6 detects the temperature of the heating element 3 .

[0062] 10, in an immersion cooling system 10B of this modified example, a control device 30B is connected to the heat generating element 3. The control device 30B has a temperature drop detection unit 31B and a pump drive unit 32B.

[0063] The temperature drop detection unit 31B detects a drop in the temperature of the heating element 3 based on the detection result of the heating element temperature sensor 6. When the temperature drop detection unit 31B detects a drop in the temperature of the heating element 3, the pump driving unit 32B drives the pump 13.

[0064] (Method for removing impurities) Next, the method for removing impurities according to this modified example will be described with reference to FIG.

[0065] In this modification, temperature drop detection unit 31B detects a drop in temperature of heating element 3 based on the detection result of heating element temperature sensor 6 (step S11B). More specifically, heating element temperature sensor 6 detects the temperature of heating element 3 itself, thereby detecting a drop in temperature of heating element 3 itself. Heating element temperature sensor 6 then transmits a signal to temperature drop detection unit 31B. By receiving this signal from heating element temperature sensor 6, temperature drop detection unit 31B detects a drop in temperature of refrigerant R in casing 23 (step S12B).

[0066] Then, pump driving unit 32B drives pump 13 (step S13B). As a result, refrigerant R circulates within the cycle of casing 23 and circulation flow path 11, and impurities in refrigerant R are removed by adsorbent 12a. Thereafter, pump driving unit 32B stops pump 13 (step S14B), and the removal of impurities in refrigerant R is completed.

[0067] (Action and effect) The immersion cooling system 10B of this modified example provides the following advantageous effects. In this modification, the control device 30B further includes a heating element temperature sensor 6 that detects the temperature of the heating element 3. A temperature drop detection unit 31B detects a drop in the temperature of the heating element 3 based on the detection result of the heating element temperature sensor 6. When the temperature drop detection unit 31B detects a drop in the temperature of the heating element 3, the pump driving unit 32B drives the pump 13.

[0068] This allows temperature drop detection unit 31B to detect a temperature drop based on a drop in the temperature of heating element 3 itself. This allows temperature drop detection unit 31B to more accurately detect a future drop in the temperature of refrigerant R in casing 23. This improves the accuracy with which temperature drop detection unit 31B detects a drop in the temperature of refrigerant R in casing 23.

[0069] In the first embodiment, the casing 23 has the lower casing 24, the upper casing 25, and the connecting wall 26, and the opening area of ​​the upper casing 25 is larger than the opening area of ​​the lower casing 24. However, this is not limiting. For example, the opening area of ​​the upper casing 25 may be smaller than the opening area of ​​the lower casing 24. Furthermore, for example, the casing 23 may be a cubic container that does not have the connecting wall 26.

[0070] Second Embodiment An immersion cooling system 210 according to a second embodiment of the present disclosure will be described below with reference to Figures 12 to 14. Configurations similar to those in the first embodiment described above will be given the same names and reference numerals, and descriptions thereof will be omitted as appropriate. As shown in FIG. 12, the immersion cooling system 210 further includes a cooling section 40.

[0071] (cooling section) The cooling unit 40 cools the refrigerant R inside the casing 23. The cooling unit 40 includes, for example, a chiller 41 and a cooling tube 42.

[0072] The chiller 41 is provided outside the casing 23 . The cooling tube 42 is provided inside the lower casing 24. Both ends of the cooling tube 42 are connected in communication with the chiller 41. The cooling tube 42 and the chiller 41 form a cycle in which the second refrigerant R2 circulates.

[0073] The second refrigerant R2 exchanges heat with the liquid-phase refrigerant R inside the casing 23 via the cooling tubes 42, cooling the refrigerant R. After exchanging heat with the refrigerant R, the second refrigerant R2 moves to the chiller 41. In the chiller 41, the second refrigerant R2 dissipates heat and is cooled. The second refrigerant R2 cooled in the chiller 41 flows through the cooling tubes 42 again and exchanges heat with the liquid-phase refrigerant R inside the casing 23.

[0074] (Control device) As shown in FIG. 13, the control device 230 of this embodiment includes a temperature drop detection unit 231 and a pump drive unit 232.

[0075] The temperature drop detection unit 231 detects the operation of the cooling unit 40, thereby detecting a drop in the temperature of the refrigerant R in the casing 23. When the temperature drop detection unit 231 detects the operation of the cooling unit 40, the pump driving unit 232 drives the pump 13.

[0076] (Method for removing impurities) Next, the method for removing impurities according to this embodiment will be described with reference to FIG. In this embodiment, the temperature drop detection unit 231 detects the operation of the cooling unit 40 (step S21), and thereby detects a drop in the temperature of the refrigerant R in the casing 23 (step S22).

[0077] Then, pump driving unit 232 drives pump 13 (step S23). As a result, refrigerant R circulates within the cycle of casing 23 and circulation flow path 11, and impurities in refrigerant R are removed by adsorbent 12a. Thereafter, pump driving unit 232 stops pump 13 (step S24), and removal of impurities in refrigerant R is completed.

[0078] (Action and effect) The immersion cooling system 210 of this embodiment provides the following advantageous effects. In this embodiment, the immersion cooling system 210 includes a cooling unit 40 that cools the refrigerant R inside the casing 23.

[0079] This reduces the time required to cool the refrigerant R inside the casing 23. Therefore, the time required from stopping the heating element 3 to opening the casing 23 is reduced. Therefore, the maintainability of the immersion cooling system 210 can be improved.

[0080] In this embodiment, the temperature drop detection unit 231 detects the operation of the cooling unit 40. Furthermore, when the temperature drop detection unit 231 detects the operation of the cooling unit 40, the pump driving unit 232 drives the pump 13.

[0081] This allows the temperature drop detection unit 231 to detect a temperature drop by stopping the heating element 3. This eliminates the need to provide a measuring instrument such as a temperature sensor to detect the temperature of the refrigerant R inside the casing 23. This further simplifies the operation control of the immersion cooling system 210.

[0082] <Modification of the second embodiment> Next, a modified example of the second embodiment will be described with reference to FIGS. As shown in FIG. 15, in an immersion cooling system 210A of this modified example, a control device 230A has a scheduled operation unit 231A, a temperature drop detection unit 232A, and a pump drive unit 233A.

[0083] The scheduled operation unit 231A operates the cooling unit 40 after a predetermined time has elapsed. The scheduled operation unit 231A sends a second reservation signal to the temperature drop detection unit 232A before operating the cooling unit 40. The scheduled operation time for the cooling unit 40 may be set in the scheduled operation unit 231A every time the refrigerant R is cooled, or may be set when the immersion cooling system 210A is manufactured, or may be set when maintenance is performed on the immersion cooling system 210A.

[0084] Upon receiving the second reservation signal, the temperature drop detection unit 232A detects that the temperature of the refrigerant R in the casing 23 will drop in the future. When the temperature drop detection unit 232A receives the second reservation signal, the pump drive unit 233A drives the pump 13.

[0085] (Method for removing impurities) Next, the method for removing impurities according to this modification will be described with reference to FIG. In this modification, first, the scheduled operation unit 231A schedules the operation of the cooling unit 40 (step S21A). Then, a second reservation signal is transmitted from the scheduled operation unit 231A to the temperature drop detection unit 232A. Upon receiving the second reservation signal (step S22A), the temperature drop detection unit 232A detects a drop in the temperature of the refrigerant R in the casing 23 (step S23A).

[0086] Then, pump driving unit 233A drives pump 13 (step S24A). As a result, refrigerant R circulates within the cycle of casing 23 and circulation flow path 11, and impurities in refrigerant R are removed by adsorbent 12a. Thereafter, pump driving unit 233A stops pump 13 (step S25A), and the removal of impurities in refrigerant R is completed.

[0087] The removal of impurities is initiated before the temperature of refrigerant R is reduced. The removal of impurities may be completed while the temperature of refrigerant R is being reduced, but it is desirable that the removal of impurities be completed before the temperature of refrigerant R is reduced.

[0088] The control device 230A of this modification may use both a method in which the temperature drop detection unit 232A detects the operation of the cooling unit 40, thereby detecting a drop in the temperature of the refrigerant R, and then drive the pump 13 (the method disclosed in the flow of FIG. 14), and a method in which the temperature drop detection unit 232A detects a drop in the temperature of the refrigerant R by receiving a second reservation signal (the method disclosed in the flow of FIG. 16). In this case, the user of the control device 230A can select which of the above methods to drive the pump 13.

[0089] (Hardware configuration) The control devices 30, 30A, 230, and 230A of the above-described embodiments and modifications are implemented in a computer 1100. The computer 1100 includes a processor 1110, a main memory 1120, a storage 1130, and an interface 1140.

[0090] The operations of the above-mentioned processing units of the control devices 30, 30A, 30B, 230, and 230A are 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-mentioned processing in accordance with the program. The processor 1110 also allocates storage areas in the main memory 1120 corresponding to the above-mentioned storage units in accordance with the program.

[0091] 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 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 performed by the processor 1110 may be realized by the integrated circuit.

[0092] 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.

[0093] The program may also be for realizing part of the above-mentioned functions. Furthermore, the program may be a so-called differential file (differential program) that realizes the above-mentioned functions in combination with another program already stored in the storage 1130.

[0094] (Other embodiments) The above describes in detail the embodiments of the present disclosure with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present disclosure. For example, the cooling section 40 and control devices 230 and 230A of the second embodiment may be applied to the immersion cooling systems 10, 10A, and 10B of the first embodiment, and control of the pump 13 based on stopping the heating element 3 or detecting a drop in temperature of the heating element 3 itself may be used in combination with control of the pump 13 based on operation of the cooling section 40.

[0095] Although the adsorbent 12a in this embodiment is activated carbon, the adsorbent 12a is not limited to this and can be changed as appropriate depending on the impurities to be adsorbed.

[0096] In the above embodiment, a case has been described in which a temperature drop of the refrigerant R in the casing 23 is detected based on the stoppage of the heating element 3 or a detection of a temperature drop of the heating element 3 itself, or a case in which a temperature drop of the refrigerant R in the casing 23 is detected based on the operation of the cooling unit 40, but the present invention is not limited to this. For example, the immersion cooling systems 10, 10A, 10B, 210, and 210A may be equipped with a temperature sensor that detects the temperature of the refrigerant R in the casing 23. In this case, the temperature drop detection units 31, 32A, 31B, 231, and 232A can also detect a drop in the temperature of the refrigerant R in the casing 23 when the temperature of the refrigerant R in the casing 23 detected by the temperature sensor is lower than a predetermined temperature.

[0097] In the above embodiments, the immersion cooling systems 10, 10A, 10B, 210, and 210A do not require a measuring device for measuring the impurity concentration in the refrigerant R, but this is not limiting. The immersion cooling systems 10, 10A, 10B, 210, and 210A may include a measuring device for measuring the impurity concentration in the refrigerant R. In this case, the immersion cooling systems 10, 10A, 10B, 210, and 210A drive the pump 13 to remove impurities from the refrigerant R until the impurity concentration measured by the measuring device reaches the solubility of the impurities at the completion of cooling of the refrigerant R.

[0098] <Additional Notes> The immersion cooling systems 10, 10A, 10B, 210, and 210A and the removal methods described in the respective embodiments can be understood, for example, as follows.

[0099] (1) Immersion cooling systems 10, 10A, 10B, 210, and 210A according to a first aspect are immersion cooling systems 10, 10A, 10B, 210, and 210A that cool a heat generating element 3 provided on a substrate 2, and include a cooling device main body 21 that houses the substrate 2 and the heat generating element 3 inside and has a casing 23 in which a refrigerant R for cooling the heat generating element 3 is stored, a circulation flow path 11 that is connected to the casing 23 in a state where both ends are in communication with each other, and an adsorption unit that is provided in the circulation flow path 11 and adsorbs impurities from the refrigerant R circulating within the circulation flow path 11. 12, a pump 13 that circulates the refrigerant R through the circulation flow path 11, and control devices 30, 30A, 30B, 230, 230A that control the pump 13, and the control devices 30, 30A, 30B, 230, 230A each include a temperature drop detection unit 31, 32A, 31B, 231, 232A that detects a drop in the temperature of the refrigerant R in the casing 23, and a pump drive unit 32, 33A, 32B, 232, 233A that drives the pump 13 based on the detection by the temperature drop detection unit 31, 32A, 31B, 231, 232A.

[0100] As a result, the immersion cooling systems 10, 10A, 10B, 210, and 210A can drive the pump 13 in accordance with the decrease in temperature of the refrigerant R in the casing 23. As a result, the refrigerant R in the casing 23 flows through the circulation flow path 11 and passes through the adsorption unit 12. The adsorption unit 12 adsorbs the impurities in the refrigerant R, thereby reducing the concentration of impurities in the refrigerant R in the casing 23. This suppresses the deposition of impurities due to the decrease in temperature of the refrigerant R in the casing 23. Furthermore, pump 13 is not driven except when the temperature of refrigerant R in casing 23 drops, and refrigerant R in casing 23 is not supplied to adsorption section 12. Therefore, except when the temperature of refrigerant R in casing 23 drops, a decrease in the concentration of impurities in refrigerant R in casing 23 is suppressed, and the impurities in refrigerant R are maintained in a saturated state. Furthermore, the power cost for operating pump 13 is reduced. Furthermore, since the driving of the pump 13 is controlled by detecting a decrease in the temperature of the refrigerant R, there is no need to provide multiple measuring instruments for light transmission, infrared spectroscopy, conductivity, and the like.

[0101] (2) The second aspect of the immersion cooling system 10 is the immersion cooling system 10 of (1), wherein the temperature drop detection unit 31 detects the stoppage of the heating element 3, and when the temperature drop detection unit 31 detects the stoppage of the heating element 3, the pump drive unit 32 may drive the pump 13.

[0102] This allows the temperature drop detection unit 31 to detect a temperature drop by stopping the heating element 3. This eliminates the need to provide a measuring instrument such as a temperature sensor to detect the temperature of the refrigerant R inside the casing 23.

[0103] (3) The third aspect of the immersion cooling system 10A is the immersion cooling system 10A of (1) or (2), wherein the control device 30A is provided with a reservation stop unit 31A that stops the heating element 3 after a predetermined time has elapsed and sends a first reservation signal to the temperature drop detection unit 32A before the heating element 3 is stopped, and the temperature drop detection unit 32A detects that the temperature of the refrigerant R in the casing 23 will drop in the future by receiving the first reservation signal, and when the temperature drop detection unit 32A receives the first reservation signal, the pump drive unit 33A may drive the pump 13.

[0104] As a result, the immersion cooling system 10A can drive the pump 13 to remove impurities from the refrigerant R inside the casing 23 before the temperature of the refrigerant R drops.

[0105] (4) The fourth aspect of the immersion cooling system 10B is an immersion cooling system 10B of any one of (1) to (3), and includes a heating element temperature sensor 6 that detects the temperature of the heating element 3. The temperature drop detection unit 31B detects a drop in temperature of the heating element 3 based on the detection result of the heating element temperature sensor 6, and when the temperature drop detection unit 31B detects a drop in temperature of the heating element 3, the pump drive unit 32B may drive the pump 13.

[0106] This allows temperature drop detection unit 31B to detect a temperature drop based on a drop in the temperature of heating element 3 itself. This allows temperature drop detection unit 31B to more accurately detect a future drop in the temperature of refrigerant R in casing 23.

[0107] (5) The immersion cooling system 210, 210A of a fifth aspect may be the immersion cooling system 210, 210A of any one of (1) to (4), and may further include a cooling unit 40 that cools the refrigerant R in the casing 23.

[0108] This reduces the time required to cool the refrigerant R inside the casing 23. Therefore, the time required from stopping the heating element 3 to opening the casing 23 is reduced.

[0109] (6) The immersion cooling system 210 of the sixth aspect is the immersion cooling system 210 of (5), wherein the temperature drop detection unit 231 detects the operation of the cooling unit 40, and when the temperature drop detection unit 31 detects the operation of the cooling unit 40, the pump drive unit 232 may drive the pump 13.

[0110] According to this aspect, the temperature drop detection unit 231 can detect a temperature drop by operating the cooling unit 40. Therefore, there is no need to provide a measuring instrument such as a temperature sensor to detect the temperature of the refrigerant R inside the casing 23.

[0111] (7) The seventh aspect of the immersion cooling system 210A is the immersion cooling system 210A of (5) or (6), wherein the control device 230A operates the cooling unit 40 after a predetermined time has elapsed and includes a reservation operation unit 231A that transmits a second reservation signal to the temperature drop detection unit 232A before the cooling unit 40 operates, and the temperature drop detection unit 232A detects that the temperature of the refrigerant R in the casing 23 will decrease in the future upon receiving the second reservation signal, and when the temperature drop detection unit 232A receives the second reservation signal, the pump drive unit 233A may drive the pump 13.

[0112] This allows the immersion cooling system 210A to drive the pump 13 to remove impurities from the refrigerant R inside the casing 23 before the temperature of the refrigerant R drops.

[0113] (8) The removal method of the eighth aspect is a removal method for removing impurities from a refrigerant R used in an immersion cooling system 10, 10A, 10B, 210, 210A that cools a heat-generating element 3 provided on a substrate 2, and the immersion cooling system 10, 10A, 10B, 210, 210A includes a cooling device main body 21 having a casing 23 that accommodates the substrate 2 and the heat-generating element 3 and stores the refrigerant R, a circulation flow path 11 connected to the casing 23 at both ends in communication with each other, and a cooling device 21 for cooling the refrigerant R. The method includes an adsorption unit 12 provided in a circulation flow path 11 and adsorbing impurities from the refrigerant R circulating within the circulation flow path 11, and a pump 13 circulating the refrigerant R through the circulation flow path 11, and includes steps S12, S13A, S12B, S22, and S23A of detecting a decrease in the temperature of the refrigerant R within the casing 23, and steps S13, S14A, S13B, S23, and S24A of driving the pump 13 based on the detection of a decrease in the temperature of the refrigerant R within the casing 23. [Explanation of symbols]

[0114] DESCRIPTION OF SYMBOLS 1...Server 2...Circuit board 3...Heat generating element 4...Power supply 5...Power cable 6...Heat generating element temperature sensor 7...Communication cable 10...Immersion cooling system 11...Circulation flow path 12...Adsorption section 12a...Adsorbent 13...Pump 20...Cooling device 21...Cooling device main body 22...Condensation section 23...Casing 24...Lower casing 25...Upper casing 26...Connecting wall 27...Heat transfer tube 30...Control device 31...Temperature drop detection section 32...Pump drive section R...Refrigerant W...Cooling water 10A...Immersion cooling system 30A...Control device 31A...Scheduled stop section 32A...Temperature drop detection section 30B...Control device 31B...Temperature drop detection section 32B...Pump drive section 33A...Pump drive section 210...Immersion cooling system 40...Cooling section 41...Chiller 42...Cooling tube 230...Control device 231...Temperature drop detection unit 232...Pump drive unit R2...Second refrigerant 210A...Liquid immersion cooling system 230A...Control device 231A...Scheduled operation unit 232A...Temperature drop detection unit 233A...Pump drive unit 1100...Computer 1110...Processor 1120...Main memory 1130...Storage 1140...Interface

Claims

1. An immersion cooling system for cooling a heat generating element provided on a substrate, comprising: a cooling device body having a casing that houses the substrate and the heat generating element and stores a coolant for cooling the heat generating element; a circulation flow path having both ends connected in communication within the casing; an adsorption section provided in the circulation flow path and configured to adsorb impurities from the refrigerant flowing through the circulation flow path; a pump that circulates the coolant through the circulation flow path; a control device for controlling the pump; Equipped with The control device a temperature drop detection unit that detects a drop in the temperature of the refrigerant in the casing; a pump driving unit that drives the pump based on the detection by the temperature drop detection unit; An immersion cooling system comprising:

2. the temperature drop detection unit detects the stop of the heating element, The immersion cooling system according to claim 1 , wherein the pump driving unit drives the pump when the temperature drop detection unit detects that the heating element has stopped.

3. The control device a reservation stop unit that stops the heating element after a predetermined time has elapsed and transmits a first reservation signal to the temperature drop detection unit before the heating element is stopped; the temperature drop detection unit detects that the temperature of the refrigerant in the casing will drop in the future by receiving the first reservation signal; The immersion cooling system according to claim 1 , wherein the pump driving unit drives the pump when the temperature drop detection unit receives the first reservation signal.

4. a heating element temperature sensor for detecting the temperature of the heating element; the temperature drop detection unit detects a temperature drop of the heating element based on a detection result of the heating element temperature sensor; The immersion cooling system according to claim 1 , wherein the pump driving unit drives the pump when the temperature drop detection unit detects a temperature drop of the heat generating element.

5. The immersion cooling system according to claim 1 , further comprising a cooling unit that cools the coolant inside the casing.

6. the temperature drop detection unit detects operation of the cooling unit, The immersion cooling system according to claim 5 , wherein the pump driving unit drives the pump when the temperature drop detection unit detects that the cooling unit is operating.

7. The control device a reservation operation unit that operates the cooling unit after a predetermined time has elapsed and transmits a second reservation signal to the temperature drop detection unit before the cooling unit is operated; the temperature drop detection unit detects that the temperature of the refrigerant in the casing will drop in the future by receiving the second reservation signal; The immersion cooling system according to claim 5 , wherein the pump driving unit drives the pump when the temperature drop detection unit receives the second reservation signal.

8. 1. A method for removing impurities from a coolant used in an immersion cooling system that cools a heat generating element provided on a substrate, comprising: The immersion cooling system includes: a cooling device body having a casing that houses the substrate and the heat generating element and stores the coolant; a circulation flow path having both ends connected in communication within the casing; an adsorption section provided in the circulation flow path and configured to adsorb the impurities from the refrigerant flowing through the circulation flow path; a pump that circulates the coolant through the circulation flow path; Equipped with detecting a decrease in the temperature of the refrigerant in the casing; driving the pump based on detection of a decrease in the temperature of the refrigerant in the casing; A removal method including:

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