Cooling system for liquid immersion cooling of electronic components

Abstract

Cooling system (1) for liquid immersion cooling of electronic components (2), comprising - a container (3) which can be filled internally with two-phase heat transfer fluid (4) in whose liquid phase electronic components (2) can be immersed, wherein the container (3) has a gas space (5) above the surface (41) of the liquid heat transfer fluid (4), - a heat exchanger device (6) in the gas space (5) of the container (3) for the formation of liquid heat transfer fluid (4), - a condenser unit (8) which is arranged outside the container (3), wherein the condenser unit (8) is connected to the gas space (5) of the container (3) by means of a fluid line (7) as supply line (71) and return line (72) for mass exchange of gaseous medium to the condenser unit (8) and condensed heat transfer fluid to the container (3), wherein the condenser unit (8) has an outlet (81) through which a residual gas phase can be discharged, characterized in that - that the fluid line (7) as supply line (71) and return line (72) of the condenser unit (8) is a single pipe with a suitable cross-sectional area or a double pipe which is connected to the container (3), and - that the fluid line (7, 71, 72) has a structured inner surface.

Description

[0001] The invention relates to a cooling system for liquid immersion cooling of electronic components according to the preamble of claim 1.

[0002] Liquid immersion cooling systems, such as two-phase immersion cooling systems, are an active cooling solution for electronic components that generate a significant amount of heat during operation. When the components are immersed in a two-phase heat transfer fluid, which typically has a low boiling point, the heat generated by the electronic component can evaporate the surrounding liquid heat transfer fluid, thus dissipating heat from the component. A condenser then liquefies the gaseous heat transfer fluid, which is subsequently returned to the reservoir for cooling.

[0003] From US patent 10,512,192 B2, a two-phase immersion cooling system with a cooling tank is known. A condensation chamber, in which the gaseous fluid produced during the cooling process is condensed, is connected to the liquid fluid in the cooling tank. A vapor diversion structure is arranged above the heat-generating electronic components, which are located within the cooling medium in the cooling tank. The evaporated fluid is directed by the vapor diversion structure into the condensation chamber for liquefaction. The condensation chamber is located entirely within the cooling tank.

[0004] In this context, a cooling system for computer components is known from US patent 10,477,726 B1. A heat-conducting, dielectric heat transfer fluid in liquid and gaseous phases is contained in a pressure-controlled vessel. This fluid has a boiling point below 80°C at atmospheric pressure. Computer components are arranged in the vessel and are at least partially immersed in the liquid phase of the heat transfer fluid. A condenser condenses the dielectric gas-phase fluid, which evaporates due to the heat generated by the computer components, back into a dielectric liquid-phase fluid. The internal pressure of the pressure-controlled vessel is reduced to as low as 650 hPa. By controlling the pressure in the vessel at which the system operates, the user can influence the temperature at which the dielectric fluid evaporates. This allows for increased cooling capacity.Operating a computer system inside a pressure-controlled container at an operating pressure that differs from the ambient pressure usually requires a structural adaptation of the system as a whole.

[0005] From US patent 2021 / 0153392 A1, a cooling system is known that includes a container which can be filled with a two-phase heat transfer fluid as a coolant, and in whose liquid phase electronic components can be immersed. The container has a gas space above the surface of the liquid heat transfer fluid. A separate external condenser is arranged above the container, configured to condense the vapor phase of the heat transfer fluid and return it as a liquid coolant to the container with the electronic components. The system includes return and supply lines that are connected to both the condenser and the container to form a heat exchange loop.The system also includes a collection vessel, which is positioned on the supply line and configured to collect the condensed liquid heat transfer fluid before the coolant is fed into the reservoir. This accumulator also provides reserve cooling capacity for the cooling system.

[0006] From publication EP 3 453 235 B1, a cooling system for immersion cooling of electronic components is known, comprising a pressure-tight tank configured to hold liquid heat transfer fluid, into which the electronic equipment is immersed. A vapor space is also present above the surface of the liquid heat transfer fluid. Outside the pressure-tight tank, a condenser is arranged, the condenser having an inlet connected to the vapor space by a riser pipe and configured to receive heat transfer fluid vapor. The condenser also features a tightly sealable vapor outlet for residual gases and a condensate outlet with a condensate return line to the tank. The condensate return line is configured to allow condensed heat transfer fluid to flow back from the condensate outlet to the tank.The tank may also already contain additional condenser tubes for liquefying gaseous heat transfer fluid.

[0007] The invention is based on the objective of further developing a cooling system for liquid immersion cooling of electronic components with respect to a heat exchanger device for the heat transfer fluid.

[0008] The invention is described by the features of claim 1. The further referenced claims relate to advantageous embodiments and further developments of the invention.

[0009] The invention includes a cooling system for liquid immersion cooling of electronic components. The cooling system comprises a container that can be filled internally with a two-phase heat transfer fluid, into the liquid phase of which electronic components can be immersed. The container has a gas space above the surface of the liquid heat transfer fluid. The cooling system also includes a heat exchanger within the gas space of the container for the formation of liquid heat transfer fluid. Furthermore, the cooling system includes a condenser unit located outside the container. The condenser unit is connected to the gas space of the container by means of a fluid line serving as both a supply and return line for mass exchange of gaseous medium to the condenser unit and condensed heat transfer fluid to the container. The condenser unit has an outlet through which any residual gas phase can be discharged.According to the invention, the fluid line, serving as the supply and return line of the condenser unit, is a single pipe with a suitable cross-section or a double pipe connected to the container.

[0010] The container can be designed to be pressure-tight. Advantageously, the container can be designed as a pressure vessel that can be operated under negative and / or positive pressure. By controlling the pressure within the container at which the cooling system operates, increased cooling capacity can be achieved.

[0011] The heat exchanger in the gas space preferably consists of at least one tube bundle comprising several heat exchanger tubes arranged relative to one another. A tube bundle can have several heat exchanger tubes arranged parallel to each other, with two end tube sheets. The arrangement of the tube bundles or the heat exchanger tubes in the vessel can be symmetrical or asymmetrical with respect to the vessel wall, or along inclined surfaces.

[0012] The supply and return lines of the condenser unit can also be a single pipe with a suitable cross-section, connected to the tank. This allows for mass transfer of both gaseous medium and condensed heat transfer fluid through this single pipe. A suitable pipe cross-section is dimensioned so that the gaseous and liquid media flowing in opposite directions within the same pipe do not impede each other's flow characteristics. Practical experience shows that, due to its wetting properties, condensed heat transfer fluid flows along the inner pipe wall towards the tank, while gaseous heat transfer fluid flows in the opposite direction towards the condenser in the region of the pipe's center.

[0013] Alternatively, the supply and return lines of the condenser unit can also be a double pipe connected to the tank. This allows for mass exchange of gaseous medium via an inner supply line and mass exchange of condensed heat transfer fluid via a return line surrounding the inner supply line. The cross-sectional area of ​​the supply and return lines is dimensioned to ensure that the gaseous and liquid media flowing in the respective lines can move with minimal resistance. Practical experience shows that, due to its smaller volume, condensed heat transfer fluid requires a smaller cross-sectional area in the outer casing of the return line than the cross-sectional area of ​​the inner supply line for gaseous heat transfer fluid.

[0014] The heat exchanger tubes are preferably finned tubes, manufactured from smooth tubes and subjected to a forming process. They are particularly suitable as components in highly efficient, compact, and extremely stable heat exchangers with a high heat transfer coefficient. The tube surfaces are optimized for the specific heat transfer requirements of the application. A wide selection of materials, including copper, copper alloys, steels, titanium, and titanium alloys, ensures that suitable material is available for various applications, particularly regarding durability and formability.

[0015] The two-phase heat transfer fluid, also known as refrigerant, is the outer fluid in the container, in whose liquid portion the electronic components are immersed. The inner fluid in the heat exchanger tubes is usually a single-phase heat transfer medium, such as process water, glycol, or thermal oil. However, a two-phase medium can also be used here in conjunction with a refrigeration circuit.

[0016] Inside the container, the electronic components are arranged in a suitable manner for cooling in a bath of liquid heat transfer fluid, which is cooled by evaporation of the liquid fluid. This allows the proportion of non-condensable gases to be effectively removed from the system before or during commissioning.

[0017] In the embodiment according to the invention, the computing components and immersion cooling devices as well as the associated power supplies, network connections, wiring connections and the like can be arranged in the container, which has an internal pressure that differs from the ambient pressure during operation.

[0018] In this context, it is also advantageous to combine power, water, vacuum and network connections in a bundle of cables to minimize penetrations into the container and to reduce the risk of leaks, especially when the system is operating under vacuum or overpressure.

[0019] In advantageous embodiments, the vessel is maintained during operation at a pressure as low as 200 hPa below ambient atmospheric pressure, which helps to lower the boiling point of the two-phase heat transfer fluid and thereby reduce the operating temperature of the computer chips and other components. In some particular embodiments, the pressure-controlled vessel can operate at an even lower pressure of up to 500 hPa below ambient pressure.

[0020] According to the invention, embodiments of the cooling system comprise a container designed to utilize a two-phase liquid immersion cooling system. The container includes a basin of dielectric cooling fluid, a heat exchanger, and an external condenser unit for condensing the dielectric fluid from the gaseous phase into a liquid. The condenser unit located outside the container is intended to condense as much of the remaining gaseous heat transfer fluid, which also contains certain amounts of air and water vapor, into liquid heat transfer fluid as possible. Ideally, the remaining heat transfer fluid is almost completely condensed from the gaseous phase, so that essentially only air and water vapor remain as the residual gaseous phase. The aim of separating the liquid heat transfer fluid is to keep the water vapor in the gaseous phase by means of a suitable cooling capacity of the system.This residual gas mixture is discharged from the cooling system via an outlet on the condenser unit.

[0021] Furthermore, devices for holding computer components and for distributing power from the power supply system to the devices and components located inside the container can be arranged. It is understood that a variety of specialized connections are used to operate a computer system within a container that is, for example, maintained under negative pressure. Some embodiments of the system according to the invention can use a number of fiber optic interfaces that enable connectivity within the container and to distribute the fibers to the various holding devices for the electronic components. Some embodiments of the container can include monitoring sensors for safe operation. These sensors can include temperature sensors, fluid level sensors, pressure sensors, position sensors, electrical sensors, and / or cameras to ensure and automate the operation of the system.

[0022] These systems can include, for example, pressure sensors inside the pressure-controlled vessel that monitor the pressure to ensure that no significant leaks are present. Similarly, gas sensors located on the outside of the pressure-controlled vessel can detect the presence of any dielectric vapor that may be escaping from the vessel.

[0023] In addition, the cooling system may advantageously include a control device designed to regulate the operation of the fluid circulation, for example as a function of the temperature of the two-phase heat transfer fluid, and the pressure conditions in the container.

[0024] Advantageously, a placement system can be installed to transport electronic components from the airlock to the operating position for replacement. Such a placement system can consist of robot arms or linear actuators. With a suitable design, the components can be replaced using a fully automated placement system. Alternatively, gloves can be positioned at suitable container openings to facilitate the exchange of electronic components from the airlock to the operating position. This allows for placement through manual access to the interior of the container.

[0025] According to the invention, the fluid line has a structured inner surface. In the case of a single pipe, the inner surface has rib-like, channel-like, porous structural features or protrusions by means of which the condensed heat transfer fluid is guided along the surface of the inner pipe to the tank inlet. In the case of a double pipe extending to the tank, the inner surface of the inner return pipe is designed to be rib-like, channel-like, porous, or with protrusions in order to guide the condensed heat transfer fluid in a controlled manner. In contrast, the inner surface of the outer pipe surrounding the return pipe, which guides the gaseous heat transfer fluid, can also be smooth.

[0026] In a particularly advantageous embodiment of the cooling system according to the invention, the structured inner surface of the fluid line can be a helically circumferential ribbed structure for guiding the condensed heat transfer fluid to the container. With a suitable rib pitch, the fluid is guided in a spiral motion along the inner pipe wall by gravity.

[0027] In an advantageous embodiment, the fluid line can be a single or double pipe running at an angle relative to the force of gravity. This allows condensed heat transfer fluid to flow back to the container, at least partially along the inner wall, due to gravity. In a single pipe, the condensed heat transfer fluid flows along the lower part of the inner wall, while the gaseous heat transfer fluid flows counter-currently along the upper part of the inner wall.

[0028] Advantageously, the inclination angle of the fluid line relative to the force of gravity can be at least 2°, preferably at least 5°, and particularly preferably at least 15°. Even such small inclination angles prevent condensed heat transfer fluid from flowing freely and uncontrollably through the inside of the pipe during its return to the vessel. In particular, with a single pipe, this prevents uncontrolled or turbulent flow that would disrupt the counterflow of the gaseous heat transfer fluid.

[0029] In a preferred embodiment of the invention, the supply lines, return lines, and / or the outlet can be individually or in combination closed or opened by valves. For suitable process control, individual valves are opened as needed to allow the passage of gaseous medium or liquid heat transfer fluid. The supply and discharge can be cyclical or continuous. In particular, the valve configuration at the outlet is designed to minimize or even eliminate the escape of heat transfer fluid from the cooling system.

[0030] In an advantageous embodiment of the invention, a collection container can be arranged downstream of the outlet, through which the residual gas phase can be discharged. This container ensures that no ambient air can enter the cooling system. The container can be an expandable elastic balloon or a bellows with variable volume.

[0031] Advantageously, a drying unit for separating water vapor from the gas phase can be arranged between the outlet and the collection tank. For example, the pressure in the entire cooling system changes during load changes. If necessary, ambient air or residual gas can be introduced into the cooling system via the drying unit through the collection tank to equalize the pressure. The water vapor is then chemically bound by the drying unit. Silica gel is suitable for such drying units.

[0032] In an advantageous embodiment of the invention, a vacuum pump can be arranged downstream of the outlet, through which the residual gas phase can be discharged. In this case, the residual gas phase consisting of water vapor and air can also exhibit a negative pressure at the outlet relative to the surroundings, since a vacuum pump always ensures an outward flow direction of the residual gas.

[0033] Advantageously, the heat exchanger and the condenser unit can share a common supply unit for a single-phase heat transfer medium for cooling. This ensures that both units operate at a uniform temperature level, which is suitable for the deposition process of the heat exchange fluid.

[0034] Advantageously, the quantity distribution of the single-phase heat transfer medium for cooling the heat exchanger unit and the condenser unit of the common supply unit can be achieved by means of active control of the volume flow of the single-phase heat transfer medium.

[0035] A multi-way valve, especially a three-way valve, is particularly suitable for actively controlling the flow rate. Alternatively, or in combination, a throttle or a frequency-controlled pump can also be integrated into the supply unit to regulate the flow rate. This allows the cooling capacities of the heat exchanger and the condenser unit to be appropriately coordinated and controlled via a single supply unit.

[0036] In an advantageous embodiment of the invention, a cooling device can be arranged at least partially on the fluid line. This can be a cooling tube or a cooling sleeve wound spirally around the fluid line. This effectively prevents the liquid fluid from reheating above its boiling point due to the warmer gaseous fluid flowing in the opposite direction. In particular, the temperature of the liquid fluid flowing along the inner wall of the fluid line is further reduced in this way.

[0037] Exemplary embodiments of the invention are explained in more detail with reference to the schematic drawings.

[0038] It shows: Fig. 1. A schematic view of a cooling system with a condenser unit and a pipe as a fluid line, and Fig. 2 Another schematic view of a cooling system with condenser unit and double piping as fluid line.

[0039] Corresponding parts are marked with the same reference symbols in all figures.

[0040] Fig. Figure 1 shows a schematic view of a cooling system 1 with a condenser unit 8 and a pipe 7 as a fluid line for liquid immersion cooling of electronic components 2. The cooling system 1 comprises a container 3, which is filled internally with a two-phase heat transfer fluid during operation. The two-phase heat transfer fluid constitutes the external fluid in the container 3, with a liquid heat transfer fluid component 4 in which the electronic components 2 are immersed and a gaseous heat transfer fluid component 5. A heat exchanger 6 is arranged in the gaseous component 5 of the container 3 to form liquid heat transfer fluid 4.

[0041] In this advantageous embodiment, the heat exchanger device 6 in the gas space 5 consists of tube bundles 61, each with several heat exchanger tubes arranged parallel to each other.

[0042] In the Fig. In the illustrated embodiment, the container 3 is slightly tapered in the area of ​​the liquid heat transfer fluid 4, with the container wall projecting inwards and only opening into the gas space 5. The shape of the container 3 is supported by a metal profile frame 31. The container 3 is therefore already enclosed by a stabilizing outer frame.

[0043] A condenser unit 8 is arranged outside the container 3, above it. The condenser unit 8 is connected to the gas space 5 of the container 3 by means of a fluid line 7, serving as a supply line 71 and a return line 72, for mass exchange of gaseous medium and condensed heat transfer fluid between the container 3 and the condenser unit 8. In the Fig. In the variant shown in Figure 1, the fluid line 7 is designed as a single pipe with a suitable cross-sectional area, serving as the supply line 71 and return line 72 of the condenser unit 8.

[0044] To regulate the mass transfer, a valve 700 is optionally installed in the fluid line 7. A gaseous mixture of heat transfer fluid, air, and water vapor is cyclically or continuously drawn off from the container 3 via the valve 700. Liquid heat transfer fluid is returned to the container 3 via the same valve 700.

[0045] In Fig. In the illustrated embodiment, a cooling device 73 is arranged on the fluid line 7. In this embodiment, the cooling device 73 is a cooling sleeve through which a coolant flows during operation to further cool the outside of the fluid line 7 and thus the liquid fluid flowing on the inside. In particular, the liquid fluid in contact with the inner wall of the fluid line 7 is thus effectively kept below its boiling point.

[0046] The residual gas phase can be routed via a feed line 91 with valve 910 to a collection container 9, which can be designed as a volume-expandable bellows to generate a vacuum. If, during operation, the valve 910 to the collection container 9 is closed, the residual gas can be discharged via the discharge line 92 of the collection container 9 when the valve 920 is open.

[0047] To further remove water vapor, a drying unit 11 is arranged between outlet 81 and collection container 9 to remove water vapor from the gas phase. Depending on the pressure, the residual gas phase can be discharged directly into the environment.

[0048] Alternatively, the residual gas phase can also be discharged via a vacuum pump 10. For this purpose, the outlet 81 is connected to a vacuum pump 10 via a supply line 101, which regulates the residual gas flow to the outside via a discharge line 102 of the vacuum pump 10 using a valve control 1010.

[0049] Fig. Figure 2 shows a schematic view of a cooling system 1 with a condenser unit 8 and a double pipe 7 as a fluid line for liquid immersion cooling of electronic components 2. As an alternative to the embodiment according to Fig.The double pipe serves as a supply line 71 for gaseous medium to the condenser unit 8 and as a return line 72 for condensed heat transfer fluid from the condenser unit 8, which is connected to the tank 3. Mass transfer of the gaseous medium occurs via the inner supply line 71. Mass transfer of the condensed heat transfer fluid occurs via a return line 72 that surrounds the inner supply line 71. The inner supply line 71 can be slightly longer than the surrounding return line 72 at its entry into the condenser unit 8. In this way, during operation of the system, the condensed heat transfer fluid flows exclusively into the return line 72 and not unintentionally into the supply line 71, which projects into the condenser unit 8.

[0050] The supply line 71 can be individually or in combination closed or opened by a valve 710, and the return line 72 can be closed or opened by a further valve 720. For appropriate process control, individual valves are opened as needed to direct gaseous medium or liquid heat transfer fluid. Reference symbol list 1 Cooling system 2 electronic component 3 containers 31 metal profile frames 4 liquid heat transfer fluid 41 Surface area of ​​the liquid fluid in the container 5 gaseous heat transfer fluid, gas space 6 Heat exchanger unit 61 tube bundles 7 Fluid line 700 Valve of the fluid line 71 Supply line 710 Valve of the supply line 72 Return line 720 Return line valve 73 Cooling unit 8 capacitor units 81 Outlet 810 Exhaust valve 9 collection containers, bellows 91 Feed line Collection container 910 Valve of the feed line collection tank 92 Drain line Collection container 920 Valve of the drain line, collection tank 10 Vacuum pump 101 Vacuum pump supply line 1010 Valve of the vacuum pump supply line 102 Vacuum pump discharge line 11 drying unit

Claims

[1] Cooling system (1) for liquid immersion cooling of electronic components (2), comprising - a container (3) which can be filled internally with two-phase heat transfer fluid (4) in whose liquid phase electronic components (2) can be immersed, wherein the container (3) has a gas space (5) above the surface (41) of the liquid heat transfer fluid (4), - a heat exchanger device (6) in the gas space (5) of the container (3) for the formation of liquid heat transfer fluid (4), - a condenser unit (8) which is arranged outside the container (3), wherein the condenser unit (8) is connected to the gas space (5) of the container (3) by means of a fluid line (7) as supply line (71) and return line (72) for mass exchange of gaseous medium to the condenser unit (8) and condensed heat transfer fluid to the container (3), wherein the condenser unit (8) has an outlet (81) through which a residual gas phase can be discharged, characterized by , - that the fluid line (7) as supply line (71) and return line (72) of the condenser unit (8) is a single pipe with a suitable cross-sectional area or a double pipe which is connected to the container (3), and - that the fluid line (7, 71, 72) has a structured inner surface. [2] Cooling system (1) according to claim 1, characterized by, that the structured inner surface of the fluid line (7, 71, 72) is a helically circumferential ribbing. [3] Cooling system (1) according to one of claims 1 to 2, characterized by , that the fluid line (7, 71,72) is a pipe or double pipe running at an angle to the effect of gravity. [4] Cooling system (1) according to claim 3, characterized by , that the inclination angle of the fluid line (7, 71,72) relative to the force of gravity is at least 2°. [5] Cooling system (1) according to any one of claims 1 to 4, characterized by , that the supply line (71), return line (72) and / or the outlet (81) can be closed or opened individually or in combination by valves (700, 710, 720, 810). [6] Cooling system (1) according to any one of claims 1 to 5, characterized by , that a collection container (9) is arranged downstream of the outlet (81), through which the residual gas phase can be discharged. [7] Cooling system (1) according to claim 6, characterized by , that a drying unit (11) for separating water vapor from the gas phase is arranged between outlet (81) and collection container (9). [8] Cooling system (1) according to any one of claims 1 to 5, characterized by , that a vacuum pump (10) is arranged downstream at the outlet (81), via which the residual gas phase can be removed. [9] Cooling system (1) according to any one of claims 1 to 8, characterized by , that the heat exchanger unit (6) and the condenser unit (8) have a common supply unit for a single-phase heat transfer medium for cooling. [10] Cooling system (1) according to claim 9, characterized by , that the quantity distribution of the single-phase heat transfer medium for cooling the heat exchanger unit (6) and the condenser unit (8) of the common supply unit is carried out by means of an active control of the volume flow of the single-phase heat transfer medium. [11] Cooling system (1) according to any one of claims 1 to 10, characterized by , that a cooling device (73) is arranged at least partially on the fluid line (7).

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