JP2018124978A - Liquid immersion cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate operation of a cooling system.SOLUTION: A liquid immersion cooler includes: a refrigerant tank that stores a silicone oil-based insulating refrigerant in which an electronic device is immersed; a circulation passage for the silicone oil-based insulating refrigerant between the refrigerant tank and a refrigerant cooler; and a pump disposed in the circulation passage to circulate the silicone oil-based insulating refrigerant between the refrigerant tank and the refrigerant cooler. A temperature of the silicone oil-based insulating refrigerant is equal to or more than 0°C. A flash point of the silicone oil-based insulating refrigerant is equal to or more than 250°C.SELECTED DRAWING: Figure 1

Description

  The invention disclosed herein relates to an immersion cooling apparatus.

  Conventionally, a cooling system for an electronic device using a fluorocarbon coolant is known (Japanese Patent Laid-Open No. 2016-46431).

JP 2016-46431 A

Fluorine-based insulating refrigerants such as fluorocarbon-based coolants used in Patent Document 1 are generally highly permeable and erode seal materials used in axial flow pumps and the like, causing refrigerant leakage There is a possibility to make it. This limits the pumps that can be used. In addition, the density of the fluorine-based insulating refrigerant used in the cooling system with a proven track record is as high as, for example, about 1.8 g / cm ^3, and the weight of the entire cooling system becomes very heavy, and the installation floor of the cooling system The load capacity of the must be increased. Furthermore, since the fluorine-based insulating refrigerant is likely to evaporate, replenishment thereof may be required, or a structure that suppresses evaporation may be required, resulting in an increase in cost. Further, the fluorine-based insulating refrigerant itself is expensive. As described above, there are various matters to be considered in the operation of the cooling system using the fluorine-based insulating refrigerant. These are all due to the nature of the refrigerant.

  In one aspect, it is an object of the immersion cooling device disclosed herein to facilitate the operation of a cooling system.

  The immersion cooling device disclosed in the present specification includes a refrigerant tank that stores a silicone oil-based insulating refrigerant that immerses an electronic device, and the silicone oil-based insulating refrigerant that is provided between the refrigerant tank and the refrigerant cooling device. And a pump that is disposed in the circulation path and circulates the silicone oil-based insulating refrigerant between the refrigerant tank and the refrigerant cooling device.

  According to the immersion cooling apparatus disclosed in this specification, the operation of the cooling system can be facilitated.

FIG. 1 is a system configuration diagram illustrating an immersion cooling system in which the immersion cooling apparatus according to the embodiment is incorporated. FIG. 2 is a table showing the characteristics of the refrigerant liquid used in the immersion cooling apparatus of the embodiment together with the characteristics of the refrigerant liquid of the comparative example. FIG. 3 (A) is an explanatory view showing an eye pattern example of a refrigerant used in the immersion cooling apparatus of the embodiment, and FIGS. 3 (B) to 3 (E) are shown together with an eye pattern example of a comparative example. FIG. FIG. 4 is a table summarizing the kinematic viscosities and flow rates of the refrigerant liquid used in the immersion cooling apparatus of the embodiment and the refrigerant liquid of the comparative example. FIG. 5 is a graph showing the relationship between the temperature and flow rate of the refrigerant liquid used in the immersion cooling apparatus of the embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, in the drawings, the dimensions, ratios, and the like of each part may not be shown so as to completely match the actual ones. Further, depending on the drawings, components that are actually present may be omitted for convenience of explanation, or dimensions may be exaggerated from the actual drawing.

(Embodiment)
First, a schematic configuration of an immersion cooling system 10 including the immersion cooling device 12 according to the embodiment will be described with reference to FIG. FIG. 1 is a system configuration diagram illustrating an immersion cooling system in which the immersion cooling apparatus according to the embodiment is incorporated.

(Immersion cooling system)
As shown in FIG. 1, the immersion cooling system 10 according to the embodiment includes an immersion cooling device 12 and a refrigerant cooling device 40. The immersion cooling device 12 includes a refrigerant tank 20 as will be described in detail later, and includes a circulation path 16 that connects between the refrigerant tank 20 and the refrigerant cooling device 40.

(Immersion cooling device)
As shown in FIG. 2, the immersion cooling device 12 includes a refrigerant tank 20. The refrigerant tank 20 is a container that houses a silicone oil-based insulating refrigerant (hereinafter referred to as a refrigerant liquid) 14. In the refrigerant tank 20, an electronic device 32 as a cooling object is accommodated. The electronic device 32 is immersed in the refrigerant liquid 14 in the refrigerant tank 20.

  The electronic device 32 is, for example, a server having a printed circuit board on which a plurality of electronic components are mounted, and a housing that houses the printed circuit board. A cable 34 is electrically connected to the printed circuit board of the electronic device 32.

  The refrigerant tank 20 includes a refrigerant tank main body portion 22 whose upper edge is open, and a refrigerant tank lid portion 26 provided at the upper edge portion of the refrigerant tank main body portion 22 so as to be opened and closed. A cable outlet 24 is formed on the outer peripheral wall of the refrigerant tank body 22. The cable 34 connected to the electronic device 32 is led out of the refrigerant tank 20 through the cable outlet 24. In an immersion cooling apparatus using a fluorine-based insulating refrigerant that has a proven track record, the refrigerant tank may be an airtight container in consideration of the fact that the fluorine-based insulating refrigerant easily evaporates. The refrigerant tank 20 is not required to be in a strictly airtight state. This is because the refrigerant liquid 14 used in the present embodiment has a smaller evaporation amount than the fluorine-based insulating refrigerant.

  The refrigerant tank 14 stores (stores) the refrigerant liquid 14. The refrigerant liquid 14 is accommodated in the refrigerant tank body 22 so as not to leak from the connection port 24. The refrigerant liquid 14 has electrical insulation and thermal conductivity. In the present embodiment, a barrel silicone fluid M-20E (hereinafter referred to as “M-20E”) manufactured by Matsumura Oil Co., Ltd. is used. Since the refrigerant liquid 14 has electrical insulation, it can be used for applications in which the electronic device 32 is immersed and cooled. The refrigerant liquid 14 will be described in detail later.

  The refrigerant tank lid part 26 is attached to the upper end part of the refrigerant tank main body part 22 via a hinge part 28. When the refrigerant tank lid part 26 rotates about the hinge part 28 with respect to the refrigerant tank body part 22, the opening provided at the upper edge of the refrigerant tank body part 22 is opened and closed.

  A refrigerant cooling device 40 is connected to the refrigerant tank 20 via the circulation path 16. The circulation path 16 circulates the refrigerant liquid 14 between the refrigerant tank 20 and the refrigerant cooling device 40. For this reason, the circulation path 16 is formed by piping or the like through which the refrigerant liquid 14 flows. The circulation path 16 is provided with a pump 17. When the pump 17 is driven, the refrigerant liquid 14 is circulated between the refrigerant tank 20 and the refrigerant cooling device 40. In addition, the arrow a shown in FIG.

  The pump 17 in the present embodiment is an axial flow pump, but other generally used stretching pumps and mixed flow pumps may be used. That is, in this embodiment, the selection range of the pump is wide, and an appropriate pump can be employed according to the performance required for the immersion cooling system 10. In contrast, when a fluorine-based insulating refrigerant is used, the selection range of the pump is narrowed. This is because the permeability of the fluorine-based insulating refrigerant is high, and if a pump provided with a sealing material in the refrigerant liquid circulation region is employed, the sealing material may be eroded and refrigerant leakage may occur. For this reason, when using a fluorine-type insulating refrigerant | coolant as a refrigerant | coolant liquid, use of the pump which does not have the possibility of erosion of sealing materials, such as a magnet pump and a can pump, for example is recommended. However, these pumps have a problem that the driving force is weaker than that of an axial flow pump or the like and it is difficult to obtain a unit time flow rate of the refrigerant liquid. With the immersion cooling device 12 of the present embodiment, the pump selection range is wide without being limited by pump selection due to the nature of the refrigerant liquid.

(Refrigerant cooling device)
The refrigerant cooling device 40 is, for example, a refrigerator that cools the refrigerant liquid 14 using a refrigeration cycle. The electronic device 32 is cooled by heat exchange between the refrigerant liquid 14 cooled by the refrigerant cooling device 40 and the electronic device 32.

  Specifically, the refrigerant cooling device 40 includes a condenser 42 and a heat exchanger 44. The condenser 42 and the heat exchanger 44 are connected to each other via the refrigerant circulation path 46. The refrigerant circulation path 46 is formed by, for example, a pipe or the like through which the refrigerant flows. Note that the arrow b shown in FIG. 1 indicates the circulation direction of the refrigerant.

  The refrigerant circulation path 46 is provided with a compressor (compressor) 48. The compressor 48 compresses the refrigerant in the gas phase that flows from the heat exchanger 44 to the condenser 42. The condenser 42 has a cooling fan (not shown) that cools the refrigerant in the gas phase compressed by the compressor 48. The refrigerant is condensed by cooling the gas-phase refrigerant with the cooling fan.

  The refrigerant circulation path 46 is provided with an expansion valve 49. The expansion valve 49 expands and depressurizes the liquid-phase refrigerant flowing from the condenser 42 to the heat exchanger 44. The heat exchanger 44 exchanges heat between the liquid-phase refrigerant decompressed by the expansion valve 49 and the refrigerant liquid 14 flowing through the circulation path 16 to vaporize the refrigerant. Thereby, the latent heat of vaporization of the refrigerant is taken away from the refrigerant liquid 14, and the refrigerant liquid 14 is cooled.

  The refrigerant evaporated in the heat exchanger 44 is compressed by the compressor 48 and then condensed in the condenser 42 described above. Thus, the refrigerant liquid 14 is cooled by circulating the refrigerant through the compressor 48, the condenser 42, the expansion valve 49, and the heat exchanger 44.

  The refrigerant cooling device 40 may have another configuration as long as it can cool the refrigerant liquid 14.

  The above is the schematic configuration of the immersion cooling system 10 of the present embodiment. Here, the refrigerant liquid 14 used in the present embodiment will be described in detail. The refrigerant liquid 14 in the present embodiment is a silicone oil-based insulating refrigerant. It is desirable that the temperature of the refrigerant liquid 14 in the refrigerant tank 20 be 0 ° C. or higher when the immersion cooling system 10 is operated. Note that when the immersion cooling system 10 is actually operated, the temperature of the refrigerant liquid 14 is managed so that the operation guarantee temperature of the electronic device 32 can be realized. For example, when the operation guarantee temperature of the electronic device 32 is set in the range of 5 ° C. to 40 ° C., the electronic device 32 is appropriately controlled by managing the temperature of the refrigerant liquid 14 in the range of 0 ° C. to 40 ° C. It can be operated in a moderate temperature environment.

  Here, selection of the refrigerant liquid 14 will be described in comparison with a comparative example. A comparative example is a fluorine-based insulating refrigerant that has been used in an immersion cooling system. Specifically, it is Fluorinert FC-3283 (hereinafter referred to as “FC-3283”) manufactured by 3M. Moreover, let vegetable oil A and vegetable oil B be a comparative example as a vegetable oil type insulating refrigerant. The vegetable oil-based insulating refrigerant is advantageous compared to the fluorine-based insulating refrigerant in terms of permeability, and therefore, the selection range of the pump is wide like the silicone oil-based insulating refrigerant.

Referring to the table shown in FIG. 2, the density of FC-3283 is 1.83 g / cm ³ and is very heavy. For this reason, when FC-3283 is adopted as the refrigerant liquid, it is necessary to increase the load resistance of the installation floor of the cooling system, and the operation cost increases. On the other hand, the density of M-20E is 0.96 g / cm ³ , which is lighter than FC-3283. The density of the vegetable oil A is 0.86 g / cm ^3, a density 0.921 g / cm ³ of the vegetable oil B, also these vegetable oil based insulating refrigerant than FC-3283 in terms of mass It is advantageous.

  Further, when paying attention to the heat transfer coefficient at 25 ° C. within the operation guarantee temperature of the electronic device 32, the vegetable oil A is 0.132 w / m · K, and the vegetable oil B is 0.176 w / m · K. It can be said that there is no big difference with 0.149 w / m · K of M-20E. FC-3283 was 0.067 w / m · K.

  Next, focusing on the kinematic viscosity at 25 ° C., which is within the operation guarantee temperature of the electronic device 32, M-20E was 20 cSt, vegetable oil A was 5.1 cSt, and vegetable oil B was 34.81 cSt. These values are both higher than FC-3283's kinematic viscosity at 25 ° C. of 0.8 cSt. In the case of FC-3283, there is a limit to the selection range of the pump. For example, when a magnet pump is employed, the driving force is small, so that the kinematic viscosity is small, which is convenient in terms of securing a necessary flow rate. In M-20E, vegetable oil A, and vegetable oil B, if the kinematic viscosity is low, the flow rate is easily improved. However, M-20E, vegetable oil A, and vegetable oil B have room to select a pump having a large driving force, and it is possible to ensure a necessary flow rate. Therefore, even if M-20E, vegetable oil A, and vegetable oil B have a kinematic viscosity higher than FC-3283, a required flow volume can be ensured.

  In the above consideration, any of M-20E, vegetable oil A, and vegetable oil B can be candidates for the refrigerant liquid.

  Next, referring to FIGS. 3A to 3E, the transmission waveforms (eye patterns) when each refrigerant liquid is also used are compared. FIGS. 3A to 3E are examples of eye patterns acquired using an electronic device that performs transmission at a certain frequency. FIG. 3A shows an eye pattern example in the air. FIG. 3B shows an eye pattern example in a state where an electronic device is immersed in M-20E. FIG. 3C shows an eye pattern example in a state where an electronic device is immersed in the vegetable oil A. FIG. 3D is an eye pattern example in a state where an electronic device is immersed in the vegetable oil B. FIG. 3E illustrates an eye pattern example in a state where an electronic device is immersed in FC-3283.

  When FC-3283 is used, an eye pattern almost similar to that in air can be obtained. In addition, even when M-20E is used, the rate of change is about 5% as compared with the case in the air, and the performance of the electronic device can be secured. On the other hand, vegetable oil A and vegetable oil B have a large rate of change and a decrease in the performance of the electronic device. Based on these evaluations, vegetable oil A and vegetable oil B are difficult to employ as refrigerant liquids.

  Therefore, in this embodiment, M-20E which is a silicone oil-based insulating refrigerant is used as the refrigerant liquid 14.

  Next, the temperature of the silicone oil-based insulating refrigerant will be considered. Referring to FIG. 4, the kinematic viscosity of FC-3283 at 25 ° C. was 0.8 cSt, and the flow rate in an apparatus equipped with a certain pump (magnet pump) was 100 L / min. When the same apparatus was used and the refrigerant liquid was changed to M-20E, the kinematic viscosity at 0 ° C. was 36.0 cSt, and the flow rate was 86 L / min. The kinematic viscosity at 20 ° C. was 21.9 cSt, and the flow rate was 91 L / min. Furthermore, the kinematic viscosity at 40 ° C. was 14.5 cSt, and the flow rate was 96 L / min.

  The electronic device 32 can operate at −5 ° C. to 50 ° C., but the electronic device 32 requiring high reliability has a practical range of 0 ° C. to 40 ° C. Therefore, the temperature of the refrigerant liquid 14 in the present embodiment is managed at 0 ° C. to 40 ° C. in order to keep the guaranteed operating temperature of the electronic device 32. It can be seen that M-20E in such a temperature range can secure a flow rate substantially similar to that of FC-3283, although a slight decrease in the flow rate is seen compared to FC-3283. Moreover, since all of these comparisons were performed using a magnet pump having a small driving force, if an axial flow pump or the like having a large driving force is employed when M-20E is employed, it is equivalent to FC-3283. It is possible to ensure the flow rate of

  FIG. 5 is a graph showing the relationship between the temperature and the flow rate of M-20E. The temperature range of this graph includes the temperature range listed in the table shown in FIG. Referring to FIG. 5, it can be seen that the rate of decrease in the flow rate increases when the temperature range is lower than 0 ° C. When the flow rate decreases due to the nature of the refrigerant liquid 14, the output of the pump 17 can be improved so as to compensate for the decrease. However, when the output of the pump 17 is improved, the energy consumption required for driving the pump increases accordingly. Thus, it is desirable to operate the immersion cooling system 10 by setting the temperature of the refrigerant liquid 14 to 0 ° C. or higher also from the viewpoint of ensuring the flow rate efficiently.

  Thus, if it is M-20E, the operation of the immersion cooling system 10 can be facilitated.

  Here, a large amount of the silicone oil-based insulating refrigerant is stored in the refrigerant tank 20. For this reason, from the viewpoint of ensuring safety, it is required that ignition is difficult. It can be said that the higher the flash point of the refrigerant liquid is, the harder it is to ignite and the safer it is. However, in consideration of the environment where the immersion cooling system 10 is installed, it is usually safe if the flash point is 250 ° C or higher. It is thought that sex can be secured. M-20E of this embodiment has a flash point of 268 ° C., which satisfies this condition. According to the law concerning fire fighting in Japan, articles with a flash point of 250 ° C. or higher are not designated as dangerous goods and are classified as flammable liquids. Therefore, if a silicone oil-based insulating refrigerant having a flash point of 250 ° C. or higher is adopted, it can be easily replaced with a water-cooled electronic device that has already been installed. It becomes easy to obtain.

  Based on the above consideration, in the present embodiment, a silicone oil-based insulating refrigerant having a flash point of 250 ° C. or higher is adopted and operated at 0 ° C. or higher.

  The silicone oil-based insulating refrigerant can be diverted from an immersion cooling system in which a fluorine-based insulating refrigerant has been used. That is, the immersion cooling system can be operated by filling a silicone oil-based insulating refrigerant having a strong bond between atoms instead of the fluorine-based insulating refrigerant. That is, the silicone oil-based insulating refrigerant is highly versatile to the immersion cooling device.

  According to the immersion cooling device 12 of this embodiment, since the weight of the immersion cooling system 10 can be reduced by adopting the silicone oil-based insulating refrigerant as the refrigerant liquid, the installation becomes easy. Moreover, the selection range of a pump becomes wide. As a result, the degree of freedom in design increases. Further, since the silicone oil-based insulating refrigerant does not easily evaporate, high airtightness is not necessary for the refrigerant tank 20 and the like. In addition, the silicone oil-based insulating refrigerant is cheaper than the fluorine-based insulating refrigerant, and can reduce the system introduction and running costs. For these reasons, the immersion cooling device 12 of the present embodiment can facilitate the operation of the immersion cooling system 10.

  In the above description, M-20E has been described as an example of the silicone oil-based insulating refrigerant, but other silicone oil-based insulating refrigerant may be used.

  Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and various modifications, within the scope of the gist of the present invention described in the claims, It can be changed.

DESCRIPTION OF SYMBOLS 10 Immersion cooling system 12 Immersion cooling apparatus 14 Refrigerant liquid 16 Circulation path 17 Pump 20 Refrigerant tank 32 Electronic device 40 Refrigerant cooling apparatus

Claims (1)

A refrigerant tank for storing a silicone oil-based insulating refrigerant that immerses the electronic device;
A circulation path of the silicone oil-based insulating refrigerant provided between the refrigerant tank and the refrigerant cooling device;
A pump that is disposed in the circulation path and circulates the silicone oil-based insulating refrigerant between the refrigerant tank and the refrigerant cooling device;
The change rate of the eye pattern of the transmission waveform when the electronic device is immersed in the silicone oil-based insulating refrigerant with respect to the eye pattern of the transmission waveform of the electronic device in the air. Is a silicone oil-based insulating refrigerant that falls within a predetermined range,
The refrigerant cooling device is an immersion cooling device including a condenser and a heat exchanger connected via a second circulation path.

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