Fluid Immersion Cooling System and Method for Cooling an Electronic System

Abstract

The present invention provides a fluid immersion cooling system, which includes a fluid tank containing a layer of two-phase coolant fluid and one or more layers of single-phase coolant fluid. The two-phase and single-phase coolant fluids are immiscible with each other, and the two-phase coolant fluid has a lower boiling point and a higher density than the single-phase coolant fluid. The substrate of an electronic system is immersed in the tank such that the high-heat generating components are at least immersed in the layer of two-phase coolant fluid. Heat from the components dissipates into the two-phase coolant fluid to generate vapor bubbles of the two-phase coolant fluid. The vapor bubbles rise to the layer of single-phase coolant fluid located above the layer of two-phase coolant. The vapor bubbles condense into droplets of two-phase coolant. The droplets fall into the layer of two-phase coolant.

Description

Technical Field

[0001] The present invention relates to fluid immersion cooling of electronic systems. Background Art

[0002] Electronic systems, such as information technology equipment (e.g., computers, routers, packet switches, cell circuits), generate heat during operation. Cooling systems have been developed to prevent overheating of electronic systems. A simple cooling system involves using a cooling fan to blow air towards the heat-generating components of an electronic system. A more complex method is to immerse an electronic system in a coolant fluid (e.g., a fluorinated fluid), such as a two-phase fluid immersion cooling system. In a conventional two-phase fluid immersion cooling system, the thermal energy generated by the electronic system converts the two-phase coolant into vapor, which rises and is collected via a condenser unit. A condenser unit is a device that converts vapor into liquid, and the liquid then falls back into the two-phase coolant, thus completing the cooling cycle.

[0003] Conventional two-phase fluid immersion cooling systems exhibit excellent power, but also have some drawbacks. First, there is a risk of vapor leakage into the environment. Leakage is particularly a concern because the vaporized two-phase coolant is considered to have a global warming potential (GWP). Second, the bellows required for vapor balance in a conventional two-phase fluid immersion cooling system occupy too much space. Third, due to the high likelihood of leakage, the manufacturing and operating costs of conventional two-phase fluid immersion cooling systems are relatively high. Summary of the Invention

[0004] The present invention provides a fluid immersion cooling system, which includes: a fluid tank housing a component of an electronic system; a layer of two-phase coolant fluid in the fluid tank, with the component of the electronic system at least immersed in this layer of two-phase coolant fluid in the fluid tank; a layer of a first single-phase coolant fluid in the fluid tank, the first single-phase coolant fluid and the two-phase coolant fluid being immiscible, and this layer of first single-phase coolant fluid being above this layer of two-phase coolant fluid. Wherein the two-phase coolant fluid has a higher density and a lower boiling point than the first single-phase coolant fluid.

[0005] In one embodiment, the first single-phase coolant fluid includes a dielectric oil.

[0006] In one embodiment, the two-phase coolant fluid includes a fluorine-containing compound.

[0007] In one embodiment, the fluid immersion cooling system further includes a cooler unit, connected to an outlet and an inlet of the fluid tank, and the cooler unit is configured to cool the first single-phase coolant fluid.

[0008] In one embodiment, the cooler unit includes a pump and a heat exchanger. The pump is configured to drive the circulation of a first single-phase coolant fluid, and the heat exchanger is configured to cool the first single-phase coolant fluid.

[0009] In one embodiment, the fluid immersion cooling system further includes: a condenser disposed above the layer of the first single-phase coolant fluid. The condenser is configured to collect and condense a plurality of vapor bubbles of the two-phase coolant fluid that are not confined to the layer of the first single-phase coolant fluid.

[0010] In one embodiment, the component of the electronic system is a central processing unit.

[0011] In one embodiment, the fluid immersion cooling system further includes a layer of a second single-phase coolant fluid in the fluid sump. The second single-phase coolant fluid, the first single-phase coolant fluid, and the two-phase coolant fluid are immiscible with each other. The layer of the second single-phase coolant fluid is above the layer of the first single-phase coolant fluid. The two-phase coolant fluid has a higher density and a lower boiling point than the second single-phase coolant fluid.

[0012] The present invention provides a method for cooling an electronic system. The method includes the following steps: immersing a component of an electronic system in a layer of a two-phase coolant fluid in a fluid sump; dissipating the thermal energy of the electronic system component into the two-phase coolant fluid to generate a plurality of vapor bubbles of the two-phase coolant fluid; condensing the vapor bubbles into a plurality of droplets of the two-phase coolant fluid in a layer of a single-phase coolant fluid, the layer of the single-phase coolant fluid being above the layer of the two-phase coolant fluid in the fluid sump, wherein the two-phase coolant fluid and the single-phase coolant fluid are immiscible with each other; receiving the droplets of the two-phase coolant fluid from the layer of the single-phase coolant fluid into the layer of the two-phase coolant fluid in the fluid sump. The two-phase coolant fluid has a higher density and a lower boiling point than the single-phase coolant fluid.

[0013] In one embodiment, the method for cooling an electronic system further includes: collecting the vapor bubbles of the two-phase coolant fluid that are not confined to the layer of the single-phase coolant fluid and condensing them in a condenser unit, the condenser unit being disposed above the layer of the single-phase coolant fluid.

[0014] In one embodiment, the two-phase coolant fluid includes a fluorine-containing compound.

[0015] In one embodiment, the single-phase coolant fluid includes a dielectric oil.

[0016] In one embodiment, the method for cooling an electronic system further includes: cooling the single-phase coolant fluid with a cooler unit outside the fluid sump.

[0017] In one embodiment, cooling the single-phase coolant fluid with a cooler unit outside the fluid reservoir includes recirculating the single-phase coolant fluid through a heat exchanger outside the fluid reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Shown is a schematic diagram of a fluid immersion cooling system according to an embodiment of the present invention.

[0019] Figure 2 Shown is as Figure 1 the operation flowchart of a fluid immersion cooling system according to an embodiment of the present invention.

[0020] Figure 3 Shown is as Figure 1 the schematic diagram of a fluid immersion cooling system according to an embodiment of the present invention.

[0021] Figure 4 Shown is a schematic diagram of a fluid reservoir containing multiple layers of coolant fluid in an embodiment of the present invention.

[0022] Figure 5 Shown is the flowchart of a method for cooling an electronic system according to an embodiment of the present invention.

[0023] The same reference numerals used in different drawings denote the same or similar elements. The drawings are not drawn to scale.

[0024] Wherein, reference numerals:

[0025] 100: Fluid immersion cooling system

[0026] 101: Substrate

[0027] 102: Electronic device

[0028] 103: Vapor bubble

[0029] 104: Droplet

[0030] 105: Boundary

[0031] 106: Arrow

[0032] 107: Arrow

[0033] 110: Coolant fluid

[0034] 120: Coolant fluid

[0035] 140: Reservoir

[0036] 141: Condenser unit

[0037] 142: Inlet

[0038] 143: Outlet

[0039] 161: Biphase coolant fluid layer

[0040] 162: Single-phase coolant fluid layer

[0041] 162-1 to 162-n: Single-phase coolant fluid layer

[0042] 201 to 208: Steps

[0043] 301 to 305: Steps

[0044] D1: Depth

[0045] D2: Depth Detailed implementation manner

[0046] The present invention provides many specific details, such as examples of devices, components and methods, to facilitate a thorough understanding of the embodiments of the present invention. However, those with ordinary knowledge in the technical field to which the present invention pertains should be able to understand that the present invention can still be implemented in the absence of one or more specific details. In other cases, well-known details are not shown or described to avoid obscuring the gist of the present invention.

[0047] Figure 1 Shown is a schematic diagram of a fluid immersion cooling system 100 according to an embodiment of the present invention. The fluid immersion cooling system 100 includes a fluid tank 140 containing a layer of biphase coolant fluid 110 and a layer of single-phase coolant fluid 120. The coolant fluids 110 and 120 are both non-conductive. The coolant fluids 110 and 120 are immiscible with each other, and the liquid density of the coolant fluid 110 is higher than that of the coolant fluid 120. Therefore, there is a separated fluid layer of the coolant fluids 110 and 120 in the tank 140. The layer of the coolant fluid 110 is located at the bottom of the tank 140, and the layer of the coolant fluid layer 120 is above the layer of the coolant fluid layer 110.

[0048] The coolant fluid 110 is a "biphase" fluid with a relatively low boiling point, which can be in the range of 40 °C to 80 °C. The operating ambient temperature of the coolant fluid 110 can be equal to or close to its boiling point. The coolant fluid 110 has a lower boiling point but a higher density than the coolant fluid 120. The coolant fluid 110 preferably has as low a viscosity as possible and a dielectric constant as close to 1 (vacuum value) as possible. The coolant fluid 110 can be a fluorinated fluid. For example, the coolant fluid 110 can be 3M TM Fluorinert TM electronic liquid, such as the product FC-3284 that can be purchased from 3M Company. Other suitable biphase coolant fluids can also be used.

[0049] The coolant fluid 120 is a "single-phase" fluid that has a relatively high boiling point, which can be higher than 80 °C. The coolant fluid 120 has a higher boiling point but a lower density than the coolant fluid 110. The operating ambient temperature of the coolant fluid 120 is lower than the boiling point of the coolant fluid 110. The coolant fluid 120 preferably has as high a viscosity as possible and a dielectric constant as close as possible to 1 (vacuum value). The relatively high viscosity advantageously allows better confinement of the vapor bubbles rising from the coolant fluid 110. The coolant fluid 120 may include dielectric oil. For example, the coolant fluid 120 can be ElectroCool available from Engineered Fluids Co., Ltd. TM Coolant. Other suitable single-phase coolant fluids can also be used.

[0050] As Figure 1 shown, a plurality of substrates 101 including the electronic device 102 are placed in the tank 140. The substrate 101 may include a printed circuit board or other electronic system substrates, such as information technology (IT) equipment. A hot spot, taking the electronic device 102 as an example, is an area or component that generates a large amount of heat energy. The electronic device 102 can be a central processing unit (CPU), a graphics processing unit (GPU), a power transistor, a field programmable gate array (FPGA), etc. In one embodiment, the hot spot is at least completely immersed in the coolant fluid 110, and the rest of the substrate 101 is immersed in the coolant fluid 120. As Figure 1 shown in the example, in the tank 140, the depth of the coolant fluid 110 is D1, and the depth of the coolant fluid 120 is D2. The depth D1 can be much shallower than the depth D2 to save the relatively expensive coolant fluid 110 and better prevent the vapor of the coolant fluid 110 from escaping through the coolant fluid 120. The dashed line represents the boundary 105 between the coolant fluid 110 and the coolant fluid 120.

[0051] The substrate 101, which is part of the electronic system, can be electrically interconnected through a motherboard, wires, etc. These interconnecting elements are not shown for the sake of clarity of illustration. When the electronic system operates, the electronic device 102 is powered on and generates heat energy. The heat energy from the electronic device 102 immersed in the coolant fluid 110 and other areas of the substrate 101 causes the coolant fluid 110 to vaporize, thereby generating vapor bubbles 103 of the coolant fluid 110. The vapor bubbles 103 (shown as white circles) rise and pass through the boundary 105 into the layer of the coolant fluid 120. The coolant fluid 120 prevents the vapor bubbles 103 from leaking. The higher the viscosity of the coolant fluid 120, the better the confinement of the vapor bubbles 103. In addition to preventing leakage, the coolant fluid 120 saves the relatively expensive coolant fluid 110.

[0052] In the layer of coolant fluid 120, vapor bubbles 103 condense into droplets 104 of coolant fluid 110. Droplets 104 (shown as small black circles) eventually fall down and cross boundary 105 into the layer of coolant fluid 110, completing the cooling cycle.

[0053] The tank 140 may be an open container and does not necessarily need to be sealed. The tank 140 may have a configuration for receiving wiring and piping and a device for facilitating introduction into the substrate 101. The fluid immersion cooling system 100 may optionally include a condenser unit 141 configured to collect vapor bubbles 103 escaping through the layer of coolant fluid 120. The condenser unit 141 may be positioned directly above the coolant fluid 120 in the tank 140 to capture the escaping vapor bubbles 103.

[0054] The tank 140 may optionally include an inlet 142 and an outlet 143 as an additional cooling mechanism. A chiller unit (not shown) may supply cold coolant fluid 120 to the tank 140 through the inlet 142 (see arrow 106). The hot coolant fluid 120 may flow out of the tank 140 through the outlet 143 (see arrow 107) to be cooled by the condenser unit 141. The condenser unit 141 is a device configured to cool hot coolant.

[0055] FIG. 1 is an operation flow chart of a fluid immersion cooling system 100 according to an embodiment of the present invention. Figure 2 In the example shown, boundary 105 separates operations occurring in a layer of two-phase coolant fluid 110 (below boundary 105) from operations occurring in a layer of single-phase coolant fluid 120 (above boundary 105).

[0056] like Figure 2 In the example shown, the electronic system is placed in a container 140, which contains a layer of coolant fluid 110 and a layer of coolant fluid 120 (see Figure 1 ). Heat from the electronic system is dissipated to ( Figure 2 , 201) and vaporize ( Figure 2 , 202) as described above, the coolant fluid 110 is a two-phase fluid. The vaporization results in the formation of the coolant fluid 110 ( Figure 2 , 203) of vapor bubbles. The vapor bubbles rise across the boundary 105 ( Figure 2 , 204) and enters the layer of coolant fluid 120 which is a single-phase fluid as described above ( Figure 2 , 205). In the layer of coolant fluid 120, the vapor bubbles condense into droplets of coolant fluid 110 ( Figure 2 , 206). In the coolant fluid 120, the droplets fall toward the layer of coolant fluid 110 ( Figure 2, 207). The droplet crosses the boundary 105 and falls into the layer of the coolant fluid 110 ( Figure 2 , 208).

[0057] In an experiment, a graduated cylinder was filled with 3M TM FC-3284 Fluorinert TM electronic liquid as the bottom-layer two-phase coolant fluid, and GRC dielectric oil was used as the upper-layer single-phase coolant fluid. The GRC dielectric oil is available from Green Revolution Cooling. Compared with the two-phase coolant fluid, the single-phase coolant fluid has a lower density and a higher viscosity. The boiling point of the two-phase coolant fluid is about 50 °C. The single-phase coolant fluid has a higher boiling point that was not reached during the experiment.

[0058] In this experiment, the graduated cylinder simulated a fluid reservoir. To simulate a cooler device, a metal reservoir filled with ice could be placed on top of the graduated cylinder in the layer of the single-phase coolant fluid. The bottom of the graduated cylinder was heated to simulate a hot spot. During the experiment, it was observed that heating the bottom of the graduated cylinder caused vapor bubbles of the two-phase coolant fluid that rose into the single-phase coolant fluid. As Figure 2 described in the flowchart of, the vapor bubbles condensed into droplets in the single-phase coolant fluid, and the droplets fell back into the two-phase coolant fluid. No leakage was observed during the experiment. The vapor bubbles were easily confined to condense in the single-phase coolant fluid layer without escaping steam.

[0059] As Figure 3 shown is a schematic diagram of a fluid immersion cooling system 100 according to an embodiment of the present invention. As Figure 3 shown in the example, the fluid immersion cooling system 100 includes a cooler unit that includes a manifold 153, one or more pumps 151, and a heat exchanger 152 (e.g., a plate heat exchanger (PHE)) connected in series with the pump 151. The pump 151 can be arranged on the hot side of the pipeline between the reservoir 140 and the heat exchanger 152 (as Figure 3 shown), the cold side, or both sides of the pipeline between the reservoir 140 and the heat exchanger 152 (see Figure 3 , the additional pump 151 is indicated by a dashed line).

[0060] During operation, the pump 151 drives the coolant fluid 120 (i.e., the single-phase coolant fluid) to circulate through the reservoir 140. The cold coolant fluid 120 enters the reservoir 140 through the inlet 142 (also see Figure 1 , 142) and the hot coolant fluid 120 leaves the reservoir 140 through the outlet 143. The manifold 153 promotes the cooling of the coolant fluid 120. The heat exchanger 152 uses an external cold water source (not shown) to further cool the coolant fluid 120.

[0061] It will be appreciated that, in accordance with the teachings of the present invention, two or more layers of coolant fluid may be used to cool an electronic system. The layers of coolant fluid may include a bottom two-phase coolant fluid layer and a plurality of single-phase coolant fluid layers located on top of the bottom two-phase coolant fluid layer. As Figure 4 shown in the example, the container 140 may be filled with a bottom two-phase coolant fluid layer 161 and upper single-phase coolant fluid layers 162 (i.e., 162-1, 162-2, 162-3, ..., 162-n). The single-phase coolant fluid layers 162 are the "upper" layers relative to the two-phase coolant fluid layer 161.

[0062] The properties of the two-phase and single-phase coolant fluids may be referred to the coolant fluids 110 and 120 as described above. More specifically, the two-phase coolant fluid layer 161 and the single-phase coolant fluid layers 162 are immiscible, and the two-phase coolant fluid layer 161 has a higher density, a lower viscosity, and a much lower boiling point than any of the single-phase coolant fluid layers 162. The single-phase coolant fluid layers 162 have different densities and are immiscible to allow different stratification levels above the two-phase coolant fluid layer 161 to have different viscosities to facilitate the condensation of the vapor bubbles of the two-phase coolant fluid layer 161.

[0063] Figure 5 Shown is a flowchart of a method for cooling an electronic system according to an embodiment of the present invention. In Figure 5 the example shown, an electronic system is placed in a fluid container having a bottom layer of a two-phase coolant fluid and an upper layer of one or more single-phase coolant fluids. The high-heat generating components of the electronic system are at least immersed in the bottom layer of the two-phase coolant fluid ( Figure 5 , 301). Heat from the components of the electronic system dissipates into the two-phase coolant fluid to generate vapor bubbles of the two-phase coolant fluid ( Figure 5 , 302). The vapor bubbles rise into the upper layer of at least one layer of the single-phase coolant fluid ( Figure 5 , 303). In the layer of the single-phase coolant fluid, the vapor bubbles condense into droplets of the two-phase coolant fluid ( Figure 5 , 304). The droplets fall towards the two-phase coolant fluid layer ( Figure 5 , 305).

[0064] A fluid immersion cooling system for cooling an electronic system has been disclosed herein. Although specific embodiments of the present invention have been provided, it should be understood that these embodiments are for illustrative purposes only and not for limitation. Many additional embodiments will be apparent to those of ordinary skill in the art to which the present invention pertains who refer to the present invention.

[0065] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention. However, these corresponding changes and modifications should all fall within the protection scope of the appended claims of the present invention.

Claims

1. A fluid immersion cooling system, characterized in that, Comprising: A fluid reservoir housing a component of an electronic system; A layer of a biphasic coolant fluid in the fluid reservoir, with the component of the electronic system at least immersed in the layer of the biphasic coolant fluid in the fluid reservoir; A layer of a first single-phase coolant fluid in the fluid reservoir, the first single-phase coolant fluid being immiscible with the biphasic coolant fluid, the layer of the first single-phase coolant fluid being above the layer of the biphasic coolant fluid, wherein the biphasic coolant fluid has a higher density and a lower boiling point than the first single-phase coolant fluid; And A layer of a second single-phase coolant fluid in the fluid reservoir, wherein the second single-phase coolant fluid, the first single-phase coolant fluid and the biphasic coolant fluid are immiscible with each other, wherein the layer of the second single-phase coolant fluid is above the layer of the first single-phase coolant fluid; wherein the biphasic coolant fluid has a higher density and a lower boiling point than the second single-phase coolant fluid.

2. The fluid immersion cooling system according to claim 1, wherein The first single-phase coolant fluid includes a dielectric oil.

3. The fluid immersion cooling system according to claim 1, wherein The biphasic coolant fluid includes a fluorine-containing compound.

4. The fluid immersion cooling system according to claim 1, wherein Further comprising: A cooler unit connected to an outlet and an inlet of the fluid reservoir, the cooler unit being configured to cool the first single-phase coolant fluid.

5. The fluid immersion cooling system according to claim 4, wherein The cooler unit includes: A pump configured to drive the circulation of the first single-phase coolant fluid; and A heat exchanger configured to cool the first single-phase coolant fluid.

6. The fluid immersion cooling system according to claim 1, wherein, Also included: A condenser disposed above the layer of the first single-phase coolant fluid, the condenser being configured to collect and condense a plurality of vapor bubbles of the biphasic coolant fluid not confined to the layer of the first single-phase coolant fluid.

7. The fluid immersion cooling system according to claim 1, wherein The component of the electronic system is a central processing unit.

8. A method for cooling an electronic system, characterized in that, The method includes the following steps: Immersing a component of an electronic system in a layer of a biphasic coolant fluid in a fluid reservoir; Dissipating the thermal energy of the electronic system component to the biphasic coolant fluid to generate a plurality of vapor bubbles of the biphasic coolant fluid; Condensing the vapor bubbles into a plurality of droplets of the biphasic coolant fluid in a layer of a first single-phase coolant fluid, the layer of the first single-phase coolant fluid being above the layer of the biphasic coolant fluid in the fluid reservoir, wherein the biphasic coolant fluid is immiscible with the first single-phase coolant fluid; Receiving the droplets of the biphasic coolant fluid from the layer of the first single-phase coolant fluid into the layer of the biphasic coolant fluid in the fluid reservoir, wherein the biphasic coolant fluid has a higher density and a lower boiling point than the first single-phase coolant fluid; And A layer of a second single-phase coolant fluid in the fluid reservoir, wherein the second single-phase coolant fluid, the first single-phase coolant fluid and the biphasic coolant fluid are immiscible with each other, wherein the layer of the second single-phase coolant fluid is above the layer of the first single-phase coolant fluid; wherein the biphasic coolant fluid has a higher density and a lower boiling point than the second single-phase coolant fluid.

9. The method for cooling an electronic system according to claim 8, wherein, Also included: Collecting the vapor bubbles of the biphasic coolant fluid not confined to the layer of the first single-phase coolant fluid and condensing them in a condenser unit disposed above the layer of the first single-phase coolant fluid.

10. The method for cooling an electronic system according to claim 8, wherein The biphasic coolant fluid includes a fluorine-containing compound.

11. The method for cooling an electronic system according to claim 8, wherein The first single-phase coolant fluid includes a dielectric oil.

12. The method for cooling an electronic system according to claim 8, wherein Also included is: Cooling the first single-phase coolant fluid by a cooler unit outside the fluid reservoir.

13. The method for cooling an electronic system according to claim 12, wherein Cooling the first single-phase coolant fluid by a cooler unit outside the fluid reservoir includes: Recycling the first single-phase coolant fluid through a heat exchanger outside the fluid reservoir.

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