Cooling method for computer system, and cooling system

Abstract

[Problem] To provide: an improved cooling method for liquid immersion cooling of a three-dimensionally complex computer system; and a cooling system. [Solution] A computer system including at least two heat-generating bodies is divided into a first segment, including at least one first heat-generating body, and a second segment, including at least one second heat-generating body, wherein the first segment is waterproofed by being covered with a waterproof coating film or a waterproof bag. The waterproofed first segment is cooled by being immersed in a liquid immersion tank in which a refrigerant circulates. The refrigerant in the liquid immersion tank is used to locally cool the first heat-generating body by means of a heat sink or a first cold plate. The unwaterproofed second segment includes a heat dissipation surface for transferring heat from the second heat-generating body to the outside. The heat dissipation surface is thermally connected to a heat conductive wall surface of the liquid immersion tank, and a heat sink structure is formed on a tank inner surface of the wall surface. The refrigerant circulating in the liquid immersion tank is used to forcibly cool the second heat-generating body.

Description

Method and system for cooling a computer system

[0001] The present invention relates to a method and system for cooling computer systems, and more particularly to a method and system for cooling computer systems that require high performance, stable operation, or low power consumption, and that generate a large amount of heat themselves, such as supercomputers, data centers, artificial intelligence (AI) processing systems, quantum computing systems, cryptographic processing systems, and blockchain processing systems, by immersing them in a coolant.

[0002] One of the biggest challenges determining the performance limits of computer-related equipment in recent years is power consumption, and the importance of research on power efficiency, especially for supercomputers, is already widely recognized. In other words, speed performance per watt (Flops / W) has become one of the indicators for evaluating supercomputers. Furthermore, it is said that more than 30% of the total power consumption of data centers is spent on cooling, and there is a growing demand for reducing power consumption by improving cooling efficiency. In addition, recent global warming and extreme heat waves caused by extreme weather events have made it impossible to cool data centers in the summer using conventional cooling methods, and improving the cooling capacity of existing systems has become an urgent matter. Moreover, the rapid growth of artificial intelligence processing, the increasing need for encryption processing, the surge in cryptocurrency mining processing, a major example of blockchain processing, and the development of the metaverse, which is predicted to grow rapidly in many areas, all necessitate a geometric increase in the processing power of data centers and computer systems, and the demand for increased cooling capacity has become very large.

[0003] For the cooling of supercomputers and data centers, air cooling and liquid cooling have conventionally been used. Liquid cooling generally has good cooling efficiency because it uses a liquid with significantly better heat transfer performance than air. In addition, liquid cooling includes immersion cooling and non-immersion cooling. As an example of immersion cooling, in "TSUBAME-KFC" built by the Tokyo Institute of Technology, an immersion cooling system using synthetic oil achieved 4.50 GFlops / W and won the first place in the "Supercomputer Green500 List" announced in November 2013 and June 2014.

[0004] On the other hand, an immersion cooling system using a fluorocarbon-based coolant instead of synthetic oil or mineral oil has been proposed. Specifically, it is an example using a fluorocarbon-based coolant (hydrofluoroether (HFE) compounds known as 3M's product names "Novec (3M's trademark. The same applies hereinafter) 7100", "Novec 7200", "Novec 7300") (for example, Patent Document 1, Patent Document 2).

[0005] In addition to these, since 2014, the present inventor has developed a new immersion cooling system that circulates a non-evaporative coolant mainly composed of a perfluoride in the open space of a cooling tank to directly cool electronic devices and a series of technologies around it (for example, Patent Document 3).

[0006] However, regarding PFAS (Perfluoroalkyl Substances and Polyfluoroalkyl Substances), which includes all of these fluorocarbon-based coolants, adverse effects on the human body, crops, and the natural environment have been pointed out since before. In December 2022, the world's largest manufacturer announced that it will completely stop production by the end of 2025, and in Europe, both production and use are expected to be prohibited by law within a few years. Therefore, there is a need for a new immersion cooling method that does not use any harmful compounds such as PFAS as a refrigerant, is more excellent in cooling capacity compared to immersion cooling methods that use PFAS as a refrigerant, and is cheaper and can be widely used around the world.

[0007] A prime example of a cooling method that does not use any harmful compounds such as PFAS as a refrigerant is one that can use ordinary water (tap water or industrial water) rather than pure water. Specifically, a cooling method has been proposed in which semiconductor chips mounted on a circuit board are placed in a flexible bag, the bag is immersed in a container filled with water as a cooling liquid, and the bag is contracted and deformed by the pressure difference between the inside and outside of the bag when the water is filled around the bag or when the pressure inside the bag is reduced, thereby making the bag adhere tightly to the semiconductor device (for example, Patent Document 4).

[0008] Furthermore, as another cooling method that utilizes water, natural water-cooled computers have been proposed, which use river, lake, seawater, or tap water as a cooling source to directly cool the computer. Specifically, this is a cooling method in which a computer with a parylene resin coating on its substrate surface is immersed in water. (For example, Non-Patent Document 1).

[0009] Furthermore, a method has been proposed in which the entire substrate is completely covered with an ultra-nano hydrophobic coating thin film using silicon compound nanoparticles to create an electronic device with excellent waterproof and moisture-resistant properties, and then cooled by immersing it in water (for example, Patent Document 5).

[0010] Another example of non-immersion cooling is a liquid cooling system for a computer system in which multiple electronic circuit boards (servers) are housed in individual racks within multiple racks. In this system, a cold plate is thermally connected to each semiconductor device on each electronic circuit board in each rack, and a coolant is circulated through piping that connects a Coolant Distribution Unit (CDU), which includes a heat exchanger and pump, to each cold plate for cooling. In this non-immersion liquid cooling system, the semiconductor devices, which are the main heat-generating elements, can be liquid-cooled, but other electronic components need to be air-cooled.

[0011] Japanese Patent Publication No. 2013-187251, Japanese Patent Publication No. 2012-527109, Japanese Patent No. 5853072, Japanese Patent No. 2804640, U.S. Patent No. 10717881. Fujiwara, Ikki et al., Information Processing Society of Japan Research Report, High-Performance Computing (HPC) "A First Step Towards a Direct Natural Water Cooled Computer", 2017-HPC-158(5), pp.1-5 (March 1, 2017). URL: http: / / research.nii.ac.jp / ~koibuchi / pdf / ikki-sighpc158.pdf

[0012] The cooling system disclosed in Non-Patent Document 1 employs a method in which the entire electronic component and electronic substrate are completely covered with a parylene thin film that does not conduct electricity and does not allow water to pass through, and the entire electronic component and electronic substrate covered with the parylene thin film are immersed in water or seawater, and the equipment is cooled using the low temperature of the water or seawater that comes into contact with the entire parylene thin film.

[0013] Similarly, the cooling system disclosed in Patent Document 5 also employs a method in which the entire electronic component and electronic substrate are completely covered with an ultra-nano hydrophobic coating thin film made of silicon compound nanoparticles that do not conduct electricity and do not allow water to pass through, and the entire electronic component and electronic substrate covered with the hydrophobic coating thin film is immersed in water, and the equipment is cooled using the low temperature of the water that comes into contact with the entire hydrophobic coating thin film.

[0014] On the other hand, the water-cooling method disclosed in Patent Document 4 involves placing the semiconductor device in a flexible bag and immersing it in a refrigerant such as water to achieve cooling.

[0015] Computer systems used in supercomputers and data centers generally include an electronic circuit board, various electronic components mounted on the circuit board (CPU (Central Processing Unit) and / or GPU (Graphics Processing Unit, General Purpose Graphics Processing Unit (GPGPU)), high-speed memory, chipset, power supply-related components such as FETs (field-effect transistors), electrolytic capacitors, network units, bus switch units, SSDs (Solid State Drives), etc.), and a PSU (Power Supply Unit) for supplying power to the electronic components.

[0016] However, modern computer systems have complex three-dimensional structures due to the complex shapes of the electronic circuit boards on which various electronic components and PSUs are mounted. Therefore, establishing a technology to coat these complex three-dimensional computer systems with a flawless, perfect thin film is expected to involve considerable technical difficulties.

[0017] Furthermore, in methods of cooling computer systems by enclosing them in a flexible bag and immersing them in a coolant such as water, it is desirable to ensure that the outer surface of the computer system and the inner surface of the bag are in close contact with as little gap as possible, thereby improving heat transfer from the computer system to the surrounding coolant. However, as the three-dimensional structure of computer systems becomes more complex, it is expected that meeting this requirement will become technically more difficult.

[0018] In a non-immersion liquid cooling system, piping is required to distribute the refrigerant from the refrigerant distribution unit to each rack, to distribute it to each electronic circuit board within the rack, and further to distribute it to the individual heat-generating components (such as CPUs or GPUs) on each electronic circuit board. However, the repeated distribution of refrigerant limits the flow rate of the refrigerant through each cold plate due to the constraints on pipe diameter and increased pressure loss, which in turn limits the cooling capacity of the heat-generating components.

[0019] Accordingly, the object of the present invention is to solve the problems of the prior art described above and to provide an improved cooling method and cooling system for immersion cooling of increasingly complex three-dimensional computer systems.

[0020] Another object of the present invention is to provide a cooling method and cooling system for a computer system that can solve the problems of reduced refrigerant flow rate per heat source and limitations in cooling capacity when distributing refrigerant through piping.

[0021] To solve the above problems, according to one aspect of the present invention, a method for cooling a computer system, comprising: dividing a computer system including two or more heat-generating elements into a first segment including one or more first heat-generating elements and a second segment including one or more second heat-generating elements; waterproofing the first segment by covering it with a waterproof film or waterproof bag; electrically connecting the waterproofed first segment and the unwaterproofed second segment, wherein the waterproofed first segment is one or more first A method for cooling a computer system is provided, comprising a second segment, which is not waterproofed and includes one or more heat sinks or first cold plates thermally connected to a heating element, a heat dissipation surface for transferring heat from one or more second heating elements to the outside, the heat dissipation surface of the second segment thermally connected to a heat-conductive wall of an immersion tank, a heat sink structure formed on the inner surface of the heat-conductive wall of the tank, a refrigerant flowing through a circulation channel connecting a heat exchanger, a first pump, and an immersion tank by piping, and immersing a waterproofed first segment in the refrigerant in the immersion tank.

[0022] In a preferred embodiment of the above cooling method, the heat sink structure includes a plurality of heat sink blocks thermally connected to the inner surface of the tank, and the heat sink blocks may include a base block and a fin region.

[0023] In a preferred embodiment of the above cooling method, the heat sink structure includes a plurality of heat sink blocks thermally connected to the inner surface of the tank, and the heat sink blocks may include microchannels formed within the heat sink blocks.

[0024] In a preferred embodiment of the above cooling method, the heat sink structure may include an uneven surface formed on the inner surface of the tank.

[0025] In a preferred embodiment of the above cooling method, the immersion tank may include a guide wall positioned opposite the heat sink structure, and a passage for flowing a portion of the coolant may be formed between the heat sink structure and the guide wall.

[0026] In a preferred embodiment of the above cooling method, a portion of the refrigerant in the immersion tank may be circulated into the first cold plate by a second pump fluidly connected to one or more first cold plates.

[0027] In a preferred embodiment of the above cooling method, a portion of the refrigerant may be forcibly sent by a third pump toward a heat sink structure formed on the inner surface of the tank.

[0028] In a preferred embodiment of the above cooling method, a third pump may be used to forcibly send a portion of the refrigerant into the passage formed between the heat sink structure and the guide wall.

[0029] In a preferred embodiment of the above cooling method, the first segment may include an electronic substrate on which various electronic components are mounted, and the one or more first heat-generating elements may include one or more GPUs, including a CPU or GPGPU. The second segment may include a power supply unit (PSU), and the second heat-generating elements may include one or more voltage converters or power semiconductors.

[0030] Furthermore, in a preferred embodiment of the above cooling method, the refrigerant is water, and the second or third pump may be a submersible pump.

[0031] Furthermore, in a preferred embodiment of the above cooling method, the power terminals of the first segment which are waterproofed and the power terminals of the second segment which are not waterproofed may be electrically connected via a conductive path, and the conductive path may be a busbar or an electrical cable.

[0032] Furthermore, in a preferred embodiment of the above cooling method, the immersion tank is formed by a bottom wall, one or more side walls, and one or more partition walls that are lower in height than one or more side walls, and the refrigerant that exceeds the partition walls is allowed to flow out of the immersion tank. One or more partition walls may be placed inside the immersion tank to form a drain section.

[0033] Furthermore, in a preferred embodiment of the above cooling method, the immersion tank is divided into two or more immersion sections by one or more partitions located within the immersion tank, and the refrigerant is introduced into the immersion tank from refrigerant inlets provided in each of the two or more immersion sections, and the refrigerant that has passed over the partitions is drained out of the immersion tank from a refrigerant outlet provided in a drain section.

[0034] In a preferred embodiment of the above cooling method, the second pump may adjust the flow rate or flow rate of the refrigerant passing through the first cold plate according to the temperature of one or more first heating elements.

[0035] In a preferred embodiment of the above cooling method, part or all of the heat sink or the first cold plate may be disposed inside or outside a waterproof coating or waterproof bag.

[0036] In a preferred embodiment of the above cooling method, when a waterproof coating or waterproof bag has an opening with an area larger than the area of ​​the first heating element, and a part or all of the heat sink or first cold plate is disposed on the outside of the waterproof coating or waterproof bag, the area surrounding the opening of the waterproof coating or waterproof bag and at least one surface of the heat sink or first cold plate may be connected in a watertight manner, and the surface of the first heating element and at least one surface of the heat sink or first cold plate may be thermally connected through the opening of the waterproof coating or waterproof bag.

[0037] According to another aspect of the present invention, a method for cooling a computer system is provided, comprising: dividing a computer system including two or more heat-generating elements into a first segment including one or more first heat-generating elements and a second segment including one or more second heat-generating elements; waterproofing the first segment by covering it with a waterproof film or waterproof bag; cooling the waterproofed first segment by immersing it in a liquid immersion tank through which a refrigerant flowing in a circulation path flows; locally cooling one or more first heat-generating elements using one or more heat sinks or a first cold plate with the refrigerant in the liquid immersion tank; and forcibly cooling one or more second heat-generating elements using the refrigerant flowing in the liquid immersion tank by thermally connecting the heat-dissipating surfaces for transferring heat from one or more second heat-generating elements of the unwaterproofed second segment to the heat-conductive wall surface of the liquid immersion tank, and forming a heat sink structure on the inner surface of the heat-conductive wall surface of the tank.

[0038] Furthermore, in a preferred embodiment of the above cooling method, one or more first heating elements may be locally forced-cooled by one or more first cold plates to which a pump is fluidly connected, using the refrigerant in the immersion tank.

[0039] In yet another aspect of the present invention, a cooling system is provided which includes a computer system, an immersion tank, a heat exchanger, a first pump, and piping that constitutes a refrigerant circulation path connecting the heat exchanger, the first pump, and the immersion tank. The computer system may include a first segment which is waterproofed by covering with a waterproof film or waterproof bag and includes one or more first heating elements and one or more heat sinks or first cold plates thermally connected to the one or more first heating elements; a second segment which is not waterproofed and includes one or more second heating elements and a heat dissipation surface for transferring heat from the one or more second heating elements to the outside; and a conductive path which electrically connects the first segment and the second segment. The immersion tank includes a heat-conducting wall to which the heat dissipation surface of the second segment is thermally connected, and a heat sink structure may be formed on the inner surface of the heat-conducting wall. The first segment may be immersed in the refrigerant in the immersion tank. The heat dissipation surface of the second segment may be thermally connected to the heat-conducting wall of the immersion tank.

[0040] In a preferred embodiment of the cooling system described above, the immersion tank may include a guide wall positioned opposite the heat sink structure, and a passage may be formed between the heat sink structure and the guide wall for flowing a portion of the coolant.

[0041] Furthermore, in a preferred embodiment of the cooling system described above, the cooling system includes a second pump which is fluidly connected to one or more first cold plates and may circulate a portion of the refrigerant in the immersion tank into the first cold plates.

[0042] Furthermore, in a preferred embodiment of the cooling system, the cooling system may include a third pump, which may forcibly deliver a portion of the refrigerant toward a heat sink structure formed on the inner surface of the tank.

[0043] In a preferred embodiment of the cooling system described above, the cooling system may include a third pump which may forcibly deliver a portion of the coolant into a passage formed between the heat sink structure and the guide wall.

[0044] A computer system including two or more heat generating bodies is divided into a first segment including one or more first heat generating bodies and a second segment including one or more second heat generating bodies. The first segment is waterproofed and immersed in a liquid immersion tank through which a refrigerant (preferably water) flows for cooling. And, using the refrigerant in the liquid immersion tank, the first heat generating body is locally cooled by a heat sink or a first cold plate. On the other hand, the second segment cools the second heat generating body without waterproofing by thermally connecting the heat radiating surface of the second segment to the heat conductive wall surface of the liquid immersion tank and by forming a heat sink structure on the inner surface of the tank of the heat conductive wall surface, using the refrigerant flowing through the liquid immersion tank. That is, different cooling requirements (liquid immersion cooling for the former and non-liquid immersion forced cooling in which the heat conductive wall surface of the liquid immersion tank functions as a cold plate with a heat sink structure formed on the inner surface of the tank for the latter) are applied to the first segment and the second segment while using a single refrigerant, and a computer system with improved cooling capacity can be constructed. For example, the computer system can be divided into a segment including a first heat generating body with a relatively large heat generation amount and being relatively easy to waterproof, and a segment including a second heat generating body with a relatively small heat generation amount and being relatively difficult to waterproof for cooling. In particular, since a heat sink structure is formed on the inner surface of the tank of the heat conductive wall surface, the heat conductive wall surface of the liquid immersion tank functions as a cold plate with enhanced cooling performance, and the non-liquid immersion forced cooling performance can be further improved. In this way, even when the three-dimensional complexity of the computer system further progresses, the computer system can be segmented into, for example, a part having a relatively planar structure and being easy to perform stable waterproofing, and a part having a relatively three-dimensional structure and being difficult to perform stable waterproofing, and different cooling requirements can be applied while using a single refrigerant.

[0045] When the immersion tank includes a guide wall disposed opposite to the heat sink structure and a passage for flowing a part of the refrigerant is formed between the heat sink structure and the guide wall, the refrigerant flowing through the passage strongly takes heat from the heat sink structure. As a result, the cooling requirement applied to the second segment (non-immersion forced cooling that functions as a cold plate with a heat sink structure formed on the inner surface of the tank) can be further enhanced.

[0046] Further, when the first heat generating body is locally forced-cooled by the first cold plate to which the second pump is fluid-connected using the refrigerant in the immersion tank, compared with the case of local cooling by the heat sink, more enhanced cooling requirements, that is, immersion cooling and local forced cooling, can be applied to the first segment.

[0047] Similarly, when configured to forcibly send a part of the refrigerant toward the heat sink structure formed on the inner surface of the tank by the third pump, or when configured to forcibly send a part of the refrigerant to the passage formed between the heat sink structure and the guide wall by the third pump, more enhanced cooling requirements, that is, non-immersion forced cooling including the action of forcibly taking heat from the heat sink structure by a part of the refrigerant, can be applied to the second segment.

[0048] Furthermore, as described above, the problems in the non-immersion liquid cooling system including the conventional cold plate, that is, the problem that the flow rate of the refrigerant flowing through each cold plate is limited due to the restriction of the pipe diameter and the increase in pressure loss in the pipe path from the refrigerant distribution unit to each cold plate, and the cooling capacity of the heat generating body is limited, can be solved. In particular, since a rich refrigerant flowing in the immersion tank is used and configured to flow the refrigerant to each cold plate by a pump, the flow rate and cooling capacity of the refrigerant for cooling each heat generating body can be sufficiently ensured.

[0049] The above-described objects and advantages of the present invention and other objects and advantages will be more clearly understood through the description of the following embodiments. However, the embodiments described below are illustrative, and the present invention is not limited thereto.

[0050] This is an explanatory diagram showing an example of a refrigerant circulation path in the overall configuration of a cooling system. This is an explanatory diagram showing an example of a second segment that is not waterproofed being provided in the overall configuration of a cooling system. This is a perspective view showing an example of a cooling system. This is a partial perspective view showing an example of a cooling system. This is a partial perspective view showing an example of a cooling system. This is a partial cross-sectional view showing an example of a second segment that is not waterproofed and an immersion tank. This is a partial cross-sectional view showing the inner surface of an immersion tank in an example of an immersion tank. This is a partial cross-sectional view showing another example of a second segment that is not waterproofed and an immersion tank. This is a partial cross-sectional view showing the inner surface of an immersion tank in another example of an immersion tank. This is a diagram showing an example of a waterproofed first segment. This is a partial cross-sectional view showing an example of a waterproofed first segment. This is a diagram showing another example of a waterproofed first segment. This is a partial cross-sectional view showing yet another example of a waterproofed first segment. This is a diagram showing yet another example of a waterproofed first segment. This is a diagram showing yet another example of a waterproofed first segment.

[0051] Hereinafter, several preferred embodiments of the computer system cooling method and cooling system according to the present invention will be described in detail with reference to the drawings.

[0052] Referring to Figures 1 to 7, the cooling system 1 includes a computer system 30, an immersion tank 11, a heat exchanger 15, a first pump 13, and piping PP that constitutes a refrigerant circulation path connecting the heat exchanger 15, the first pump 13, and the immersion tank 11.

[0053] The computer system 30 includes a first segment 100 that is waterproofed by covering it with a waterproof film or waterproof bag 41, a second segment 33 that is not waterproofed, and a conductive path 35 that electrically connects the first segment 100 and the second segment 33.

[0054] The first segment 100 includes one or more first heating elements 312. The first segment 100 may include one or more heat sinks or first cold plates 25 thermally connected to each of the first heating elements 312. The second segment 33 includes one or more second heating elements 332.

[0055] The refrigerant circulation path, composed of PP piping, specifically includes a route starting from the refrigerant inlet 15a of the heat exchanger 15, and continuing through piping P1, the pump 13's suction port 13a, the outlet 13b, piping P2, T-joint T1, piping P3, P4, the refrigerant inlets 11a, 11a of the immersion tank 11, the refrigerant outlets 11b, 11b, piping P5, P6, T-joint T2, and finally reaching the refrigerant outlet 15b of the heat exchanger 15. For illustrative purposes, in Figures 1 and 2, arrows indicating the direction of refrigerant flow are added next to the circulation path, and white arrows indicating the flow of refrigerant within the immersion tank 11 are added. The piping and T-joints may be located at the bottom of the rack 17, along with the pump 13 and the heat exchanger 15.

[0056] The first segment 100 is immersed in the refrigerant 12 in the immersion tank 11. A heat sink (not shown) may be provided on the first segment 100, or a cold plate 25 and a second pump 28 may be provided on the first segment 100. The second pump 28 may be fluidly connected to the cold plate 25 through a manifold 26. The second pump 28 may be a submersible pump and may draw in a portion of the refrigerant 12 in the immersion tank 11 and circulate it through the cold plate 25.

[0057] Generally, a computer system can be divided into an electronic circuit board portion, which consists of one or more CPUs or GPUs and various other electronic components mounted on a substrate, and a PSU portion, which includes one or more voltage converters or power semiconductors. The electronic circuit board corresponds to a first segment separated from the computer system, and the PSU corresponds to a second segment separated from the computer system. The CPU, GPU, voltage converter, and power semiconductor are merely examples, but the CPU or GPU corresponds to a first heat source, and the PSU substrate on which the voltage converter or power semiconductor is mounted within the PSU enclosure corresponds to a second heat source.

[0058] In one embodiment of the electronic circuit board 100 corresponding to the first segment, as shown in Figure 7, four CPUs or GPUs are mounted in a single row on one side of the circuit board (PCB) 311, and the back surface of a cold plate is thermally connected to each CPU or GPU. The upper part of the electronic circuit board 100 is provided with DC voltage input terminals 32a and 32b to which conductive paths 35 are electrically connected, and a connector terminal 36 to which a communication network cable 37 is connected.

[0059] The electronic circuit board 100 should be waterproofed except for the DC voltage input terminals 32a and 32b and the connector terminal 36. A detailed explanation of the waterproofing treatment will be given later. The electronic circuit board 100 shown in the figure has a shape in which heating elements of the same shape are arranged in a line on the board, and therefore has a relatively planar and simple structure, making it easy to apply stable waterproofing treatment to this part. Since the electronic circuit board 100 is waterproofed, it can be cooled by immersing it in a liquid immersion tank 11 filled with ordinary water. In the example shown (Figure 3), a total of 16 electronic circuit boards 100, 8 on each side, can be immersed in the liquid immersion tank 11 for cooling.

[0060] The PSU 33, which corresponds to the second segment, includes a plurality of PSU components 332 inside a rectangular parallelepiped housing, as shown in Figures 3, 5, and 6A. One side of the housing is provided with DC voltage output terminals 34a and 34b, a connector terminal 36, and a power plug (not shown). In the illustrated example, the plurality of PSU components 332 inside the housing may include a PSU substrate, capacitors mounted on the PSU substrate, one or more voltage converters or power semiconductors, etc. At least one of these plurality of PSU components 332, typically one or more voltage converters or power semiconductors, corresponds to the second heat source. The internal structure of the housing of the PSU 33 is more three-dimensional and complex than that of the electronic circuit board 100. Therefore, it is expected that waterproofing all of these plurality of PSU components will be considerably difficult. Therefore, a heat sink 335 may be installed on another side of the housing (the side facing the side wall 112 of the immersion tank 11), and the heat sink 335 may form a heat dissipation surface for transferring heat from the PSU component 332, which is not waterproofed, to the outside. Then, as shown in Figure 6A, the heat sink 335 may be thermally connected to the outer wall surface of the side wall 112 of the immersion tank 11.

[0061] In addition, as shown in Figures 6A and 6B, a plurality of heat sink blocks 115, each including a base block and a fin region, may be thermally connected to the inner surface of the immersion tank 11 to form a heat sink structure. The positional relationship between the heat sink blocks 115 and the heat dissipation plates 335 is not particularly limited, but for example, as shown in Figure 6B, the connection surface between the inner surface of the immersion tank 11 and each heat sink block 115 may be determined to overlap, in part or in whole, with the connection surface between the outer surface of the side wall 112 and each heat dissipation plate 336 via the side wall 112. The immersion tank 11 may include a guide wall 117 positioned opposite the plurality of heat sink blocks 115, and a passage for a portion of the coolant may be formed between the heat sink blocks 115 and the guide wall 117. The left and right edges of the guide wall 117 may be connected to the left and right side walls of the four side walls 112. On the other hand, the upper and lower edges of the guide wall 117 may be open. In Figure 6B, for illustrative purposes, only the upper and lower edges of the guide wall 117 are shown as dashed lines.

[0062] When the refrigerant 12 (preferably water) flows through the immersion tank 11, the refrigerant 12 passes through the fin region of the heat sink block 115, which is thermally connected to the inner surface of the immersion tank 11. If a guide wall 117 is installed, a portion of the refrigerant 12 enters the passage from the lower edge side of the guide wall 117, passes through the fin region of the heat sink block 115, and exits from the upper edge side of the guide wall 117. The refrigerant 12 flowing in this manner powerfully removes heat from the heat-conducting wall surface of the immersion tank 11. The wall surface (side wall 112) of the immersion tank 11 functions as a powerful cold plate for the PSU 33, thereby forcibly cooling the PSU component 332 without immersion. The heat sink 335 may preferably be an aluminum plate or a copper plate having excellent heat conductivity. When the heat sink 335 and the outer wall surface of the side wall 112 are thermally connected, a heat transfer layer 337 made of thermal grease may be interposed, or it may not be necessary to interpose the heat transfer layer 337. Furthermore, the heat sink block 115 may be made of aluminum or copper, and when it is thermally connected to the inner surface of the immersion tank 11, a heat transfer layer (not shown) made of thermal grease may be interposed, or it may not be necessary to interpose a heat transfer layer. As will be described later, the side wall 112 of the immersion tank 11 may preferably be formed from an aluminum plate or a copper plate, but when the heat sink plate 335 of the PSU 33 and the side wall 112 of the immersion tank 11 are made of different metals, a non-metallic spacer (not shown) and a heat transfer layer 337 may be interposed between the heat sink plate 335 and the outer wall surface of the side wall 112 to avoid corrosion due to contact between dissimilar metals. Similarly, when the heat sink block 115 and the side wall 112 of the immersion tank 11 are made of different metals, a non-metallic spacer (not shown) and a heat transfer layer (not shown) may be interposed between the heat sink block 115 and the side wall 112.

[0063] Referring to Figure 6B, a plurality of pumps 19 may be installed in the immersion tank 11, and each pump 19 may be configured to forcibly deliver a portion of the refrigerant toward the fin region of each heat sink block 115 provided on the inner surface of the immersion tank 11. If the immersion tank 11 includes a guide wall 117, each pump 19 may be positioned in a passage formed between the heat sink block 115 and the guide wall 117. Each pump 19 may be a submersible pump having one or more inlets for drawing in a portion of the refrigerant and one or more outlets for discharging the refrigerant in a predetermined direction. If the immersion tank 11 includes a guide wall 117, the pumps 19 may be installed such that the inlets of the pumps 19 are located near the lower edge of the guide wall 117 and the outlets of the pumps 19 are located inside the passage. As the refrigerant discharged from the pumps 19 passes through the fin region, it forcibly removes heat from the heat sink block 115. This allows for the application of a more enhanced non-immersion forced cooling system to the PSU 33, which is installed on the outer surface of the side wall 112 of the immersion tank 11, including the forced heat removal effect by the heat sink block 115. Furthermore, the guide wall 117 has the effect of restricting the flow of refrigerant discharged from the pump 19 into the passage, thus contributing to an improvement in the cooling efficiency of the PSU 33.

[0064] The heat sink block shown in Figures 6A and 6B, in which a fin region is formed on the surface of the base block, is just one example, and the heat sink structure formed on the inner surface of the immersion tank 11 is not limited to this. The heat sink structure may have a configuration in which, for example, a large number of pins are provided on the surface of the base block, or a large number of grooves are formed, thereby forming grid-like or arbitrary patterned microchannels within the heat sink block.

[0065] Figures 6C and 6D show an example of a heat sink structure that does not use a heat sink block. The heat sink structure may have a configuration in which an uneven structure 116 is formed on the inner surface of the immersion tank 11. The uneven structure 116 can be formed by performing various mechanical or chemical treatments on one surface of an aluminum plate or copper plate that will constitute the side wall 112 of the immersion tank 11. The mechanical or chemical treatment may be, for example, grinding, laser irradiation, blasting, etching, plating, or a combination thereof. The positional relationship between the uneven structure 116 and the heat sink 335 is not particularly limited, but for example, as shown in Figure 6D, the area on the inner surface of the immersion tank 11 in which the uneven structure 116 is formed may be determined so that it partially or completely overlaps the connection surface between the outer wall surface of the side wall 112 and each heat sink 336 via the side wall 112. The immersion tank 11 may include a guide wall 117 positioned opposite the uneven structure 116 on the inner surface of the tank, and a passage for a portion of the refrigerant may be formed between the uneven structure 116 and the guide wall 117. The left and right edges of the guide wall 117 may be connected to the left and right side walls of the four side walls 112. On the other hand, the upper and lower edges of the guide wall 117 may be open. In Figure 6D, only the upper and lower edges of the guide wall 117 are drawn with dashed lines.

[0066] Referring to Figure 6D, multiple pumps 19 may be installed in the immersion tank 11, and each pump 19 may be configured to forcibly deliver a portion of the refrigerant toward the uneven structure 116 provided on the inner surface of the immersion tank 11. If the immersion tank 11 includes a guide wall 117, each pump 19 may be positioned in a passage formed between the uneven structure 116 and the guide wall 117. Alternatively, the pumps 19 may be installed such that their inlet is located near the lower edge of the guide wall 117 and their outlet is located inside the passage. As the refrigerant discharged from the pumps 19 passes through the uneven structure 116, it forcibly removes heat from the uneven structure 116. This allows for a more enhanced non-immersion forced cooling, including the forced heat removal effect by the uneven structure 116, to be applied to the PSU 33 installed on the outer wall surface of the side wall 112 of the immersion tank 11. The guide wall 117 has the effect of restricting the flow of refrigerant discharged from the pump 19 into the passage, and contributes to improving the cooling efficiency of the PSU 33, as in the example shown in Figure 6B.

[0067] Figures 6B and 6D show a configuration in which the immersion tank 11 includes a guide wall 117 and the pump 19 is positioned in the passage. While this configuration offers more advantages, it should be noted that the use of the guide wall 117 and the pump 19 is optional. In addition to the example where the lower end of the guide wall 117 is open, the lower end of the guide wall 117 may be closed by another wall. In this case, the pump 19 is preferably positioned such that its intake port is outside the closed lower edge of the guide wall 117 or its vicinity, and its discharge port is inside the closed lower edge. Even with this configuration, each pump 19 can forcibly deliver a portion of the refrigerant toward the heat sink block 115 or uneven structure 116 provided on the inner surface of the immersion tank 11.

[0068] Referring to Figures 3 and 5, regarding the electrical connection between the electronic circuit boards 100 and the PSUs 33, in the illustrated example, the DC voltage output terminals of the four PSUs 33 are connected in parallel, and the four PSUs 33 are assigned to the four electronic circuit boards 100 that are immersed in the refrigerant in the immersion tank 11. Power is supplied to the 16 electronic circuit boards 100 from the 16 PSUs 33 arranged around the immersion tank 11. Note that the number of electronic circuit boards 100 and the number of PSUs 33 included in the computer system 30 are arbitrary and are not limited to the illustrated example.

[0069] The DC voltage input terminal 32a of the electronic circuit board 331 and the DC voltage output terminal 34a of the PSU 33, and the DC voltage input terminal 32b and the DC voltage output terminal 34b are electrically connected via busbars 35. However, for the sake of illustration, in Figure 6, the busbar 35 is shown for one of the DC voltage output terminals 34a of the PSU 33, but the busbar 35 for the other DC voltage output terminal 34b is omitted from the illustration. Electrical cables may be used instead of busbars. Busbars or electrical cables correspond to conductive paths.

[0070] A heat exchanger 15 for cooling the refrigerant circulating in the circulation path may be, for example, a plate heat exchanger. Cooled external refrigerant is supplied to the cooling refrigerant inlet 15c of the heat exchanger 15 from a chiller (not shown) or from groundwater, well water, river water, industrial water, etc. Heat exchange takes place with the refrigerant 12 to be cooled within the heat exchanger 15, and the heated refrigerant is discharged from the cooling refrigerant outlet 15d and returned to the chiller (not shown). The cooling refrigerant path can be configured using piping. However, for the sake of illustration, the cooling refrigerant path is omitted in Figure 1, and arrows indicating the direction of flow of the cooling refrigerant are added to the cooling refrigerant inlet 15c and cooling refrigerant outlet 15d of the heat exchanger 15.

[0071] As shown in Figure 1, the immersion tank 11 may be formed by a bottom wall 111, one or more side walls 112, and one or more partition walls 113 that are lower in height than one or more side walls, and the refrigerant 12 that exceeds the partition walls 113 may be allowed to flow out of the immersion tank 11. One or more partition walls 113 may be arranged inside the immersion tank 11 to form a drain section. For example, the immersion tank 11 may be divided into two immersion sections by two partition walls 113 arranged inside the immersion tank, and the refrigerant 12 flowing through the piping PP may flow into the immersion tank from a refrigerant inlet 11a provided in each of the two immersion sections, and the refrigerant that exceeds the partition walls 113 may flow out of the piping PP outside the immersion tank from a refrigerant outlet 11b provided in the drain section. The appropriate performance of the pump 13 and heat exchanger 15 and the diameter of the piping PP may be specified considering the flow velocity or flow rate of the refrigerant flowing near the surface of the waterproofed first segment.

[0072] At least the side walls 112 of the immersion tank 11 may be formed from an aluminum plate or a copper plate having high thermal conductivity. For example, if the bottom wall 111 is formed from a stainless steel plate, the side walls 112 can be watertightly fixed to the bottom wall 111 using corner connecting members made of acrylic resin or polycarbonate to avoid galvanic corrosion.

[0073] Next, with reference to Figures 7 to 14, we will describe in more detail an example and other examples of a waterproofed first segment, i.e., a waterproofed electronic circuit board.

[0074] Referring to Figures 7 and 8, an example of a waterproof electronic circuit board 100 is provided, in which the electronic circuit board, which includes a substrate (PCB) 311 and a plurality of heating elements 312 mounted on the substrate 311, is covered with a waterproof bag 41. The waterproof electronic circuit board 100 may further include a plurality of cold plates 25 and a submersible pump 28. The cold plates 25 may include a fluid inlet 27 and a fluid outlet 29 provided in the main body. Fluid channels (microchannels) may be formed inside the main body of the cold plates 25. The channels may be formed to increase the surface area in contact with the fluid, for example, by forming a mesh-like hole, a zigzag-shaped hole, or a space in which a number of fins or pins are arranged at predetermined intervals inside the main body.

[0075] In the illustrated example, all of the multiple cold plates 25 may be arranged on the outside of the waterproof bag 41, and at least one surface (e.g., the back surface) of the body of each of the multiple cold plates 25 may be thermally connected to each of the multiple heating elements 312. In this case, an opening 45 with an area larger than the area of ​​the heating elements 312 may be formed in the waterproof bag 41, and the area surrounding the opening 45 and the back surface of the body of the cold plate 25 may be watertightly connected via a bonding layer 51.

[0076] Alternatively, the waterproofed electronic circuit board 100 may include multiple heat sinks (not shown) instead of multiple cold plates 25. A heat sink typically includes a body made of a plate-shaped or disc-shaped metal block. A fin area may or may not be formed on the surface of the heat sink body. The fin area may be provided with a number of plate-shaped fins rising from the surface of the body. All of the multiple heat sinks may be disposed outside the waterproof bag 41, and at least one surface (e.g., the back surface) of each of the multiple heat sink bodies may be thermally connected to each of the multiple heat elements 312. In this case, an opening 45 with an area larger than the area of ​​the heat elements 312 may be formed in the waterproof bag 41, and the area surrounding the opening 45 and the back surface of the heat sink body may be watertightly connected via a bonding layer 51. The following description of the bonding layer 51 also applies when heat sinks are used instead of cold plates.

[0077] The bonding layer 51 is formed by using a dissimilar material bonding film, double-sided adhesive tape, or watertight packing to connect the back surface of the cold plate 25 to the outer surface of the waterproof bag. The dissimilar material bonding film, double-sided adhesive tape, or watertight packing forming the bonding layer 51 may have an opening similar in shape to the opening 45.

[0078] As an example of a dissimilar material bonding film that forms the bonding layer 51, the "MetaSeal" series (Fujimori Kogyou's product name) manufactured by Fujimori Kogyou Co., Ltd. can be used. Since this dissimilar material bonding film is formed into a film of uniform thickness, it can be sandwiched between the back surface of the cold plate 25 and the outer surface of the waterproof bag 41 and heat-pressed to form a bonding layer that joins the cold plate 25 and the waterproof bag 41. A heat press or an iron-type heater can be used for heat-pressing, and the bonding process between the cold plate 25 and the waterproof bag 41 can be completed easily and in a short time (a few seconds or more). The method for forming the bonding layer 51 is not limited to heat-pressing, and various methods such as pressurization, ultrasound, electromagnetic waves, and light irradiation may be used.

[0079] By forming the bonding layer 51 from a dissimilar material bonding film, it is possible to achieve surface bonding between the back surface of the cold plate 25 and the outer surface of the waterproof bag 41 with a uniform film thickness and no variation in adhesive strength.

[0080] Another example of a dissimilar material bonding film that forms the bonding layer is "WelQuick" (Resonac Corporation's product name), manufactured by Resonac Corporation. This dissimilar material bonding film utilizes the solid-liquid phase change of the film material, allowing the bonding process to be completed in a short time (a few seconds), and also enabling peeling and re-bonding by reheating after bonding. Therefore, it is easy to recover waterproof electronic circuit boards from cooling systems after a certain period of use and peel the cold plates 25 from the waterproof bags 41, resulting in high resource recyclability.

[0081] Here, the dissimilar material bonding film can preferably be a sheet or film that has been pre-formed into shape and then cut. However, it is not limited to this, and for example, if a certain environment is in place that allows for appropriate control of various conditions, including the film thickness and shape, the bonding layer 51 formed from the dissimilar material bonding film can be obtained starting from a liquid or gel-like adhesive material. Specifically, as an example, first, a mold is placed on the surface of a cold plate and filled with a liquid or gel-like adhesive material to form a coating of adhesive material of a desired shape and volume on the surface of the cold plate. Next, with the coating of adhesive material in contact with the back surface of the cold plate and the outer surface of the waterproof bag, the coating of adhesive material can be solidified by methods such as heating and pressing, pressurizing, ultrasonic waves, electromagnetic waves, or light irradiation. In this way, a bonding layer formed from a dissimilar material bonding film can be obtained starting from a liquid or gel-like adhesive material.

[0082] Alternatively, the bonding layer may be formed from double-sided adhesive tape. For example, a high-strength acrylic foam tape (for example, 3M's product name "3M VHB Tape") can be cut to the desired size and shape to prepare double-sided adhesive tape for the bonding layer. A bonding layer can be formed to join the cold plate and the waterproof bag by pressing one side of the double-sided adhesive tape against the back surface of the cold plate 25 or the outer surface of the waterproof bag, and then pressing the other side of the double-sided adhesive tape against the outer surface of the waterproof bag or the back surface of the cold plate. The use of double-sided adhesive tape has the advantage that it does not require heat treatment, making it easy to form the bonding layer. When using double-sided adhesive tape, it is preferable to arrange the cut tape so that the bonding layer forms a continuous and closed band surrounding the opening 45 of the bag 41.

[0083] Alternatively, the bonding layer may be formed by a watertight packing. As an example, various types of rubber packings, in the form of a continuous and closed strip or line (typically an O-ring), can be used. The watertight packing is placed between the back surface of the cold plate and the outer surface of the waterproof bag so as to surround the opening 45 of the bag 41. The cold plate is then fixed to the substrate by screwing or the like. In this fixed state, the watertight packing elastically deforms, applying appropriate surface pressure in a strip or line to the area surrounding the opening 45 of the bag 41, and can maintain a watertight seal on both sides of the surrounding area.

[0084] In the illustrated example, the manifold 26 may be positioned outside the waterproof bag 41. The inlet of the manifold 26 may be fluidly connected to the outlet of the submersible pump 28, and each outlet of the manifold 26 may be fluidly connected to each fluid inlet 27 of the multiple cold plates 25.

[0085] The submersible pump 28 is intended to draw in a portion of the refrigerant from the immersion tank 11 and forcibly send the refrigerant toward the manifold 26. The refrigerant distributed by the manifold 26 is intended to pass through the fluid inlet 27, through the flow path formed in the body of the cold plate 25, and exit into the immersion tank 11 through the fluid outlet 29.

[0086] The waterproof bag 41 may be made of a film of a synthetic resin (e.g., polyethylene, polypropylene, polyester, etc.) that has water resistance and heat resistance to relatively low temperatures (e.g., 100°C or higher) and can maintain watertightness. In the illustrated example, the top of the waterproof bag 41 does not need to be airtight (airtight / watertight), and it is sufficient that at least the portion immersed in the refrigerant is airtight. In this case, when the cooling system 1 is in operation, the relatively flexible waterproof bag 41 is pressed by the liquid pressure of the surrounding refrigerant, allowing the inner surface of the waterproof bag 41 to come into contact with both sides of the substrate 311 and the various electronic components 38 mounted on the substrate to a certain extent.

[0087] The immersion tank 11 contains a sufficient amount of refrigerant to immerse the waterproofed electronic circuit board 100. The refrigerant can be ordinary water (tap water, industrial water, or seawater, etc.). The piping PP connected to the immersion tank 11 provides a passage for discharging the refrigerant heated in the immersion tank 11 and returning the refrigerant cooled by the heat exchanger 15 to the immersion tank 11. When the waterproofed electronic circuit board 100 is immersed in the refrigerant, the refrigerant flowing over its surface cools the entire waterproofed electronic device 100. If the waterproofed electronic circuit board 100 further includes a cold plate 25 and a submersible pump 28, the refrigerant forced to pass through a flow path formed within the body of the cold plate 25 locally and powerfully removes heat from the heating element 312.

[0088] On the other hand, if the waterproofed electronic circuit board 100 includes a heat sink (not shown) instead of a cold plate 25 and a submersible pump 28, the coolant passing over the surface of the heat sink locally removes heat from the heat-generating element 321. When the amount of heat generated from the heat-generating element 321 is relatively small, the cooling performance can sometimes be satisfied by immersion cooling of the entire electronic device and localized cooling of the heat-generating element by the heat sink. This is also true for other examples of waterproofed electronic devices described below.

[0089] Figure 9 shows another example of a waterproof electronic device. This waterproof electronic circuit board differs from the waterproof electronic circuit board 100 shown in Figures 7 and 8 in that, in the waterproof electronic circuit board 110, a submersible pump 28 is connected to each fluid inlet 27 of the multiple cold plates 25 without the use of a manifold. This example has many advantages when a submersible pump 28 is connected to each of the multiple cold plates 25. For example, the temperature of each heating element can be detected, and the flow rate or flow rate of the refrigerant drawn in and discharged from each submersible pump can be adjusted according to the detected temperature. In other words, the flow rate or flow rate of the fluid passing through the inside of the cold plates can be controlled individually. This makes it possible to perform appropriate temperature control according to the heat generated by the heating elements in an electronic circuit board containing multiple heating elements.

[0090] Figures 10 and 11 show yet another example of a waterproof electronic circuit board. This waterproof electronic circuit board differs from the waterproof electronic circuit board 100 shown in Figures 7 and 8 in that, in the waterproof electronic device 200, all of the multiple cold plates 25 are arranged inside the waterproof bag 41, the waterproof bag 41 does not have openings for thermal connection, and the openings of the fluid outlets 29 of the cold plates 25 are arranged outside the waterproof bag 41. In order to arrange the openings of the fluid outlets 29 of the cold plates 25 outside the waterproof bag 41, the fluid outlets 29, which are made of pipes, for example, need to pass through a penetration formed in the waterproof bag 41. In this case, it is advisable to configure the device so that watertightness is maintained by providing a sealing material or other appropriate treatment at the penetration.

[0091] Figure 12 shows yet another example of a waterproofed electronic circuit board. This waterproofed electronic circuit board differs from the waterproofed electronic circuit board shown in Figure 11 in that, in the waterproofed electronic circuit board 210, each of the multiple submersible pumps 28 is fluidly connected to each of the multiple cold plates 25's fluid inlets 27 without the use of a manifold.

[0092] Figure 13 shows yet another example of a waterproofed electronic circuit board. This waterproofed electronic circuit board differs from the waterproofed electronic device 200 shown in Figure 10 in that, in the waterproofed electronic device 300, the fluid outlet 29 of one of the adjacent cold plates 25 (four cold plates in the illustrated example) is fluidly connected to the fluid inlet 27 of the other cold plate via connecting piping 24, and a single submersible pump 28 is fluidly connected to the fluid inlet 27 of the cold plate located at the bottom, without the use of a manifold. In other words, the multiple cold plates 25 are connected via connecting piping 24, and the refrigerant is forcibly circulated by the submersible pump 28.

[0093] Figure 14 shows yet another example of a waterproof electronic circuit board. This waterproof electronic circuit board differs from the waterproof electronic device 300 shown in Figure 13 in that, in the waterproof electronic device 310, at least one surface of the body of one cold plate 25 is thermally connected to multiple heating elements (four heating elements in the illustrated example). In other words, multiple cold plates in the example of Figure 13 may be integrated to form a single cold plate.

[0094] The above describes an example of a cooling system and several examples of waterproofed electronic circuit boards with reference to the drawings, but further modifications can be made to the details of the components. For example, as a specific example of waterproofing an electronic circuit board, an example of covering it with a waterproof bag was shown, but other specific examples of waterproofing electronic devices include, firstly, covering the electronic device with a parylene thin film that does not conduct electricity and does not allow water to pass through (see, for example, Ikki Fujiwara et al., Information Processing Society of Japan Research Report High Performance Computing (HPC) "A First Step Towards a Direct Natural Water Cooled Computer" 2017-HPC-158(5), pp.1-5 (March 1, 2017). URL: http: / / research.nii.ac.jp / ~koibuchi / pdf / ikki-sighpc158.pdf). Secondly, covering the electronic device with an ultra-nanohydrophobic coating thin film using silicon compound nanoparticles that does not conduct electricity and does not allow water to pass through (see, for example, U.S. Patent No. 1,0717881). Electronic devices with a relatively flat structure are easier to waterproof.

[0095] Furthermore, instead of a network communication cable, a waterproof electronic circuit board may contain a wireless communication unit (not shown) within the waterproof bag 41, which enables wireless communication between the waterproof electronic circuit board and the outside.

[0096] On the other hand, the PSU does not have to include a heat sink. In this case, at least one surface of the PSU component itself may form a heat dissipation surface for transferring heat from the PSU component to the outside. Furthermore, the PSU may further include a cooling fan, which may additionally cool part or all of the PSU component inside the enclosure.

[0097] Furthermore, the PSU is not limited to being installed on the outer wall side of the immersion tank's side wall. For example, an upper open compartment for installing the PSU may be formed on the inner wall side of the immersion tank's side wall. The upper open compartment may be surrounded at its bottom and perimeter by an aluminum or copper plate and may be formed to be watertight to prevent refrigerant from entering the interior of the upper open compartment. The PSU may be installed within the upper open compartment such that its heat dissipation surface is thermally connected to the inner wall surface of the upper open compartment. Even with this configuration, the inner wall surface of the upper open compartment functions as a heat-conducting wall surface of the immersion tank, and the PSU component can be forcibly cooled using the refrigerant circulating within the immersion tank.

[0098] The present invention can be widely applied to techniques for cooling computer systems containing two or more heating elements by immersing them in conductive or non-conductive refrigerants such as ordinary water, tap water, or seawater.

[0099] 1 Cooling System 11 Immersion Tank 111 Bottom Wall 112 Side Wall 113 Partition Wall 115 Heat Sink Block (Heat Sink Structure) 116 Uneven Structure (Heat Sink Structure) 117 Guide Wall 11a Refrigerant Inlet 11b Refrigerant Outlet 12 Refrigerant 13 Pump (First Pump) 13a Inlet 13b Outlet 15 Heat Exchanger 15a Refrigerant Inlet to be Cooled 15b Refrigerant Outlet to be Cooled 15c Cooling Refrigerant Inlet 15d Cooling Refrigerant Outlet 17 Rack 19 Submersible Pump (Third Pump) PP, P1, P2, P3, P4, P5, P6 Piping T1, T2 T-pipe 24 Connecting Piping 25 Cold Plate (First Cold Plate) 26 Manifold 27 Fluid Inlet 28 Submersible pump (second pump) 29 Fluid outlet 30 Computer system 100, 110, 200, 210, 300, 310 Waterproof electronic circuit board (first segment) 311 Circuit board (PCB) 312 Heating element (first heating element) 32a, 32b DC voltage input terminal 33 PSU (second segment) 332 PSU component (second heating element) 335 Heat sink 337 Heat transfer layer 34a, 34b DC voltage output terminal 35 Busbar (conductive path) 36 Connector terminal 37 Network communication cable 38 Electronic component 41 Waterproof bag 45 Opening 51 Bonding layer

Claims

1. A computer system including two or more heat-generating elements is divided into a first segment including one or more first heat-generating elements and a second segment including one or more second heat-generating elements; the first segment is waterproofed by covering it with a waterproof film or waterproof bag; the waterproofed first segment and the unwaterproofed second segment are electrically connected; the waterproofed first segment includes one or more heat sinks or first cold plates thermally connected to the one or more first heat-generating elements; the unwaterproofed second segment includes a heat-dissipating surface for transferring heat from the one or more second heat-generating elements to the outside; the heat-dissipating surface of the second segment is thermally connected to a heat-conductive wall of an immersion tank, a heat sink structure is formed on the inner surface of the heat-conductive wall of the tank; a refrigerant is circulated through a circulation channel connecting a heat exchanger, a first pump, and the immersion tank by piping; and the waterproofed first segment is immersed in the refrigerant in the immersion tank. Methods for cooling computer systems.

2. The method for cooling a computer system according to claim 1, wherein the heat sink structure includes a plurality of heat sink blocks thermally connected to the inner surface of the tank, and the heat sink blocks include a base block and a fin region.

3. The method for cooling a computer system according to claim 1, wherein the heat sink structure includes a plurality of heat sink blocks thermally connected to the inner surface of the tank, and the heat sink blocks include microchannels formed within the heat sink blocks.

4. The method for cooling a computer system according to claim 1, wherein the heat sink structure includes an uneven structure formed on the inner surface of the tank.

5. The method for cooling a computer system according to claim 1, wherein the immersion tank includes a guide wall positioned opposite the heat sink structure, and a passage for flowing a portion of the refrigerant is formed between the heat sink structure and the guide wall.

6. A method for cooling a computer system according to claim 1, wherein a portion of the refrigerant in the immersion tank is circulated into the first cold plates by a second pump fluidly connected to one or more first cold plates.

7. A method for cooling a computer system according to claim 1, wherein a third pump forcibly delivers a portion of the refrigerant toward the heat sink structure formed on the inner surface of the tank.

8. The method for cooling a computer system according to claim 5, wherein a third pump is used to forcibly deliver a portion of the refrigerant into a passage formed between the heat sink structure and the guide wall.

9. The cooling method according to claim 1, wherein the first segment includes an electronic substrate on which various electronic components are mounted, and the one or more first heating elements include one or more GPUs (Graphics Processing Units) including a CPU (Central Processing Unit) or a GPGPU (General Purpose Graphics Processing Unit), and the second segment includes a Power Supply Unit (PSU), and the one or more second heating elements include one or more voltage converters or power semiconductors.

10. The cooling method according to claim 1, wherein the refrigerant is water and the second pump is a submersible pump.

11. The cooling method according to claim 7, wherein the refrigerant is water and the third pump is a submersible pump.

12. The cooling method according to claim 1, wherein the power terminals of the first segment which are waterproofed and the power terminals of the second segment which are not waterproofed are electrically connected via a conductive path.

13. The cooling method according to claim 1, wherein the immersion tank is formed by a bottom wall, one or more side walls, and one or more partition walls that are lower in height than the one or more side walls, and the refrigerant that exceeds the partition walls is allowed to flow out of the immersion tank.

14. The cooling method according to claim 11, wherein one or more partitions are arranged in the immersion tank to form a drain section.

15. The cooling method according to claim 14, wherein the immersion tank is divided into two or more immersion sections by one or more partitions arranged within the immersion tank, the refrigerant is introduced into the immersion tank from a refrigerant inlet provided in each of the two or more immersion sections, and the refrigerant that has passed the partitions is drained out of the immersion tank from a refrigerant outlet provided in the drain section.

16. The cooling method according to claim 1, wherein the second pump adjusts the flow rate or flow rate of the refrigerant passing through the first cold plate according to the temperature of the one or more first heating elements.

17. The cooling method according to claim 1, wherein part or all of the heat sink or the first cold plate is disposed inside the waterproof coating or the waterproof bag, or outside the waterproof coating or the waterproof bag.

18. The cooling method according to claim 17, wherein an opening is formed in the waterproof coating or waterproof bag having an area larger than the area of ​​the first heating element, and when part or all of the heat sink or the first cold plate is disposed on the outside of the waterproof coating or waterproof bag, the area surrounding the opening of the waterproof coating or waterproof bag is watertightly connected to at least one surface of the heat sink or the first cold plate, and the surface of the first heating element and the at least one surface of the heat sink or the first cold plate are thermally connected through the opening of the waterproof coating or waterproof bag.

19. A method for cooling a computer system comprising: dividing a computer system including two or more heat-generating elements into a first segment including one or more first heat-generating elements and a second segment including one or more second heat-generating elements; waterproofing the first segment by covering it with a waterproof coating or waterproof bag; cooling the waterproofed first segment by immersing it in a liquid immersion tank through which a refrigerant flowing in a circulation path flows, and locally cooling the one or more first heat-generating elements using one or more heat sinks or a first cold plate with the refrigerant in the liquid immersion tank; and forcibly cooling the one or more second heat-generating elements using the refrigerant flowing in the liquid immersion tank by thermally connecting the heat-dissipating surface of the unwaterproofed second segment for transferring heat from the one or more second heat-generating elements to the outside to a heat-conductive wall surface of the liquid immersion tank, and forming a heat sink structure on the inner surface of the heat-conductive wall surface of the tank.

20. The method for cooling a computer system according to claim 19, wherein the refrigerant in the immersion tank is used to locally force-cool the one or more first heating elements by the one or more first cold plates to which the pump is fluid-connected.

21. A computer system, an immersion tank, a heat exchanger, a first pump, and piping constituting a refrigerant circulation path connecting the heat exchanger, the first pump, and the immersion tank, wherein the computer system includes: a first segment, which is waterproofed by covering with a waterproof film or waterproof bag, and includes one or more first heating elements and one or more heat sinks or first cold plates thermally connected to the one or more first heating elements; a second segment, which is not waterproofed, and includes one or more second heating elements and a heat dissipation surface for transferring heat from the one or more second heating elements to the outside; and a conductive path electrically connecting the first segment and the second segment, wherein the immersion tank includes a heat-conducting wall to which the heat dissipation surface of the second segment is thermally connected, and a heat sink structure is formed on the inner surface of the heat-conducting wall. A cooling system for a computer system, which immerses the first segment in the refrigerant in the immersion tank.

22. The cooling system for a computer system according to claim 21, wherein the immersion tank includes a guide wall positioned opposite the heat sink structure, and a passage for flowing a portion of the refrigerant is formed between the heat sink structure and the guide wall.

23. The cooling system according to claim 21, wherein the cooling system includes a second pump, the second pump being fluidly connected to one or more first cold plates, and circulating a portion of the refrigerant in the immersion tank into the first cold plates.

24. The cooling system according to claim 21, wherein the cooling system includes a third pump, the third pump forcibly delivers a portion of the refrigerant toward the heat sink structure formed on the inner surface of the tank.

25. The cooling system according to claim 22, wherein the cooling system includes a third pump, the third pump forcibly delivers a portion of the refrigerant into a passage formed between the heat sink structure and the guide wall.

26. The cooling system according to claim 23, wherein the refrigerant is water and the second pump is a submersible pump.

27. The cooling system according to claim 24, wherein the refrigerant is water and the third pump is a submersible pump.

28. The cooling system according to claim 21, wherein the first segment includes an electronic substrate on which various electronic components are mounted, and the one or more first heating elements include one or more GPUs (Graphics Processing Units) including a CPU (Central Processing Unit) or a GPGPU (General Purpose Graphics Processing Unit), and the second segment includes a Power Supply Unit (PSU), and the one or more second heating elements include one or more voltage converters or power semiconductors.

29. The cooling system according to claim 21, wherein the conductive path is a busbar or an electrical cable.

30. The cooling system according to claim 21, wherein the immersion tank is formed by a bottom wall, one or more side walls, and one or more partition walls that are lower in height than the one or more side walls, and the refrigerant that has passed the partition walls is allowed to flow out of the immersion tank.

31. The cooling system according to claim 30, wherein one or more partitions are arranged in the immersion tank to form a drain section.

32. The cooling system according to claim 31, wherein the immersion tank is divided into two or more immersion sections by one or more partitions arranged within the immersion tank, the refrigerant is introduced into the immersion tank from a refrigerant inlet provided in each of the two or more immersion sections, and the refrigerant that has passed the partitions is drained out of the immersion tank from a refrigerant outlet provided in the drain section.

33. The cooling system according to claim 23, wherein the second pump adjusts the flow rate or flow rate of the refrigerant passing through the first cold plate according to the temperature of the one or more first heating elements.

34. The cooling system according to claim 21, wherein part or all of the heat sink or the first cold plate is disposed inside the waterproof coating or the waterproof bag, or outside the waterproof coating or the waterproof bag.

35. The cooling system according to claim 34, wherein the waterproof coating or waterproof bag has an opening with an area larger than the area of ​​the first heating element, and when part or all of the heat sink or the first cold plate is disposed outside the waterproof coating or waterproof bag, the area surrounding the opening of the waterproof coating or waterproof bag is watertightly connected to at least one surface of the heat sink or the first cold plate, and the surface of the first heating element and the at least one surface of the heat sink or the first cold plate are thermally connected through the opening of the waterproof coating or waterproof bag.

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