Active 2-phase mist stream cooling system

Abstract

To provide an active two-phase mist stream cooling system.SOLUTION: A cooling system 10 includes: a channel 115 surrounding a heat source; a coolant droplet introducer 112 for vaporizing a coolant droplet as a coolant gas in a channel by heat generated by the heat source in order to introduce the coolant droplet into the channel; a compressor 102 for pumping air containing the coolant gas from a channel subspace to a condenser subspace; and a condenser 107 for condensing the coolant gas into coolant droplets or a coolant liquid. The coolant liquid is introduced into a coolant droplet introducer or being introduced therefor.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This application relates to a cooling system, and more particularly, to an active 2-phase mist-stream cooling system.

Background Art

[0002] By comparing passive and active, single-phase and two-phase, it is possible to classify conventional cooling systems. Among single-phase cooling, the systems can be classified by air cooling and liquid cooling. Typical examples of cooling systems for electronic devices range from single-phase cooling systems such as passive and / or active air cooling, active water cooling, etc., to two-phase cooling systems such as vapor-chamber heat-spreaders and two-phase liquid immersion cooling. By utilizing the potential latent heat absorption / release during the gas-liquid phase change, two-phase liquid immersion cooling can achieve extremely high heat dissipation rates.

[0003] However, the downsides of two-phase immersion cooling systems include difficulties during installation, problems with vapor containment during operation, complexity during maintenance, and potential interactions between electronic components including cables and the cooling fluid.

[0004] Therefore, there is a need to improve the prior art.

Summary of the Invention

[0005] Therefore, the main objective of this application is to provide an active 2-phase mist-stream cooling system to improve the drawbacks of the prior art.

[0006] One embodiment of this application discloses a cooling system, the cooling system comprising: a channel encompassing a heat source; a coolant-droplets introducer configured to introduce coolant droplets into the channel, the coolant droplets vaporizing as coolant gas in the channel by heat generated by the heat source; a compressor configured to pump an air from a channel subspace to a condenser subspace, the air containing the coolant gas; and a condenser configured to condense the coolant gas into coolant droplets or coolant liquid. The coolant liquid is introduced into or for the coolant-droplets introducer.

[0007] These and other objectives of the present invention will undoubtedly become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments illustrated in various figures and drawings. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram illustrates the relationship between vapor pressure and temperature for various coolants. [Figure 2] This is a schematic diagram of a cooling system according to one embodiment of this application. [Figure 3] This is a schematic diagram of a cooling system according to one embodiment of this application. [Figure 4]A schematic diagram of a condenser according to one embodiment of this application is shown. [Modes for carrying out the invention]

[0009] All the drawbacks of two-phase immersion cooling systems would disappear if the structure of "immersion of coolant liquid into a body" were modified to "immersion in a stream of moving coolant mist." "Coolant mist" refers to airborne coolant droplets suspended in a gaseous transport medium, i.e., a collection of tiny drops of coolant, and the transport medium flows at a suitable high speed to form a stream of moving coolant mist.

[0010] In this invention, an active two-phase mist-stream cooling system is introduced, in which a stream or mist-stream (for example, shown by 114 below) containing a gas transport medium into which a mist of suspended coolant droplets is injected is forced into (by active pushing or sucking) heat generating regions (for example, shown by 115 below), where heat is absorbed as latent vaporization heat as the coolant droplets are infused within the mist-stream vaporize. The coolant vapor, carried by the same gas transport medium and resulting, is then forced into (by active pushing or sucking) a condenser (for example, shown by 107 below), where the coolant vapor condenses back into a liquid phase, releasing heat (as latent condensation heat) during the condensation process.

[0011] In this application, unless otherwise specified, the term “air” may be used interchangeably with the term “gas transport medium,” and both terms may refer to, but are not limited to, air in the atmosphere or any other suitable gaseous medium, in which microscopic coolant droplets may be suspended in an airborne manner to form a mist stream.

[0012] Unless otherwise specified, the term “coolant” in this invention generally refers to a substance selected to have a vapor pressure A at a boiling point (mk)°C, i.e., k°C below an upper bound m°C of the device operating temperature range. For example, in one embodiment relating to smartphone processor cooling, the upper bound of the processor operating temperature range is typically 85°C, i.e., m ≈ 85. Assuming a target k of 30°C, when methanol is used as the coolant, a pressure of 0.7 [ATM] (532 [mmHg]) would have a boiling point of approximately 55°C, according to Figure 1.

[0013] The coolant in the cooling system of the present invention may be selected not only according to its chemical or physical properties but also according to practical requirements. Coolant gas or coolant vapor refers to a coolant that is vaporized in gaseous form / gas phase.

[0014] Figure 2 is a schematic diagram of a cooling system 10 according to one embodiment of this application. The cooling system 10 includes a coolant (selected according to specific requirements), a channel 115 encompassing a heat source 140, a coolant-droplets introducer 112, a compressor 102, a condenser 107, a pressure regulating valve 109, and a heat remover 105. The coolant-droplets introducer 112 may be similar to a mistifier or humidifier, and may include a MEMS-fabricated air pumping device, where MEMS is a Micro-Electro-Mechanical System. The coolant droplet inlet 112 is configured to introduce coolant droplets into the channel 115. By absorbing heat generated by / from the heat source 120, the coolant droplets will vaporize as coolant gas (coolant in a gaseous state / gas phase) in the channel 115. It should be noted that coolant droplets refer to the coolant in a liquid state / liquid phase, while coolant gas refers to the coolant in a gaseous state / gas phase.

[0015] The compressor 102 (which may include an air pumping device manufactured using MEMS) is configured to pump / suck air from a channel subspace (also indicated as 115) into a condenser subspace (also indicated as 107). The air pumped / sucked into the condenser subspace 107 consists of / contains a coolant gas. The compressor 102 is also configured to maintain an air pressure difference between the channel subspace 115 and the condenser subspace 107, such that the air pressure in the channel subspace 115 is lower than the air pressure in the condenser subspace 107. That is, the maintained air pressure difference may be thought of as the lower pressure in the channel 115 and the higher pressure in the condenser 107. In one embodiment, the air pressure in the condenser subspace 107 may be maintained at 1.05 ATM, and the air pressure in the channel subspace 115 may be maintained at 0.8 ATM, but is not limited to these.

[0016] The condenser 107 is configured to condense the coolant gas back into coolant droplets or coolant liquid, that is, to condense the gaseous coolant into a liquid coolant. The coolant droplets or coolant liquid (coolant in liquid phase) from the condenser 107 are led to and / or introduced into the coolant-droplets introducer 112.

[0017] Assume that compressor 102 can generate a pressure difference of 0.25 ATM from its inlet to its outlet; that is, compressor 102 can reduce the pressure in channel 115 to 0.8 ATM, while increasing the pressure in condenser 107 to 1.05 ATM. Such a pressure difference causes the coolant to evaporate at a lower boiling power in channel 115 and condense at a higher dew point in condenser 107. In this case, a system of asymmetrical liquid-gas phase transition points (or an asymmetrical pair of boiling point and dew point) is generated.

[0018] In a cooling system 10 having asymmetrical liquid-gas phase transition points, it should be noted that even if the temperature of the channel 115 and the condenser 107 is the same, evaporation (in the channel subspace 115) and condensation (in the condenser subspace 107) occur due to the pressure difference, absorbing and releasing latent heat while maintaining a nearly constant temperature.

[0019] A pressure regulating valve 109 (which may include a MEMS-fabricated venting device) is configured to regulate the pressure difference between the pressure corresponding to the channel subspace 115 (after the pressure regulating valve 109) and the pressure corresponding to the condenser subspace 107 (before the pressure regulating valve 109), such that the pressure after the pressure regulating valve 109 (corresponding to the channel subspace 115) is lower than the pressure before the pressure regulating valve 109 (corresponding to the condenser subspace 107). In one embodiment, to prevent undesirable evaporation of the coolant liquid, the pressure regulating valve 109 may be located much closer to the inlet of the channel 115 than to the condenser 107.

[0020] Since condensation from gas to liquid is a heat release process, the heat remover 105 is configured to remove the heat released by the condenser 107. In one embodiment, the heat remover 105 may be, or may include, an air movement device such as a fan or blower (which may also be manufactured using MEMS). In other embodiments, the heat remover 105 may be, or may include, a chilling device or chiller.

[0021] In addition, conduit 108 is configured to connect a mixture of air and condensed coolant liquid between the condenser 107 and the pressure regulating valve 109. The mixture of air and coolant vapor injected into the condenser 107 by the compressor 102 will be separated into air and coolant liquid by a condensation process inside the condenser 107. After passing through the pressure regulating valve 109, the pressure drops to the level of the channel subspace 115. The air will pass through air conduit 120, while the coolant liquid will pass through another coolant conduit 110. Optionally, an insulation sleeve 111 may be used to prevent the coolant from evaporating.

[0022] In one embodiment, the coolant-droplets introducer 112 may include a reservoir part and a mister part. The reservoir part is used to store coolant liquid from another coolant conduit 110. The mister part may be functionally and structurally the same as or similar to the print head of an injection printer. The mister part may inject microscopic coolant droplets into the airflow carried by conduit 120 toward channel 115. These airborne coolant droplets and airflow are infused together to form a mist-stream 114, which is then injected from the coolant droplet inlet 112 into the channel 115.

[0023] In the operation of the system 10 described above, it should be noted that as long as the coolant droplets in the mist stream do not completely evaporate in the channel partial space 115, the temperature in the channel partial space 115 can remain below or near the boiling point for potential heat absorption of vaporization.

[0024] In other words, when the coolant droplet introducer 112 provides sufficient coolant droplets, the temperature of the channel 115 may be maintained so as not to be higher than a specific level (corresponding to the boiling point of the coolant at low air pressure), or may be maintained within a specific range (such as within 5 °C). The heat generated by the heat source may be absorbed as potential heat of evaporation in the channel 115 and released as potential heat condensation in the condenser 107.

[0025] It should be noted that the effect of "the temperature remaining below or near the boiling point in the partial space 115" is achieved by potential heat absorption of vaporization, meaning that a very uniform temperature is obtained throughout the partial space 115.

[0026] Compared with two-phase immersion cooling systems, the coolant droplets forming such a mist stream are liquid, so the main feature of two-phase liquid immersion cooling, which utilizes the potential heat absorption during the phase change between liquid and gas to achieve a high heat exchange rate, is retained or inherited.

[0027] On the other hand, by replacing the "body of liquid" with a "stream of mist", the effective viscosity of the coolant is also significantly reduced compared with two-phase immersion cooling systems. This clearly lower viscosity creates new advantages over the original liquid form, that is, as long as the droplets are much smaller than their small spatial dimensions, the moving mist tends to penetrate through extremely small cracks and gaps and into any small space.

[0028] In addition, by replacing "liquid masses" with "streams of mist," there are no longer any "liquid tanks" that tend to spill and / or leak throughout the entire space, and all problems related to the two-phase immersion cooling system, such as installation, operation, or maintenance, become far more "manageable" and "solvable."

[0029] By combining these factors, the "mist stream" of this low-viscosity coolant opens up new possibilities for use in one of the most challenging cooling needs in 3D packaged ICs, such as cooling between multiple silicon layers within a single IC. This means that not only are computing units such as CPUs / GPUs / NPUs / TPUs (Central / Graphics / Neural network / Tensor Processing Units) heat sources, but TSVs (through silicon vias) can also be part of the heat source.

[0030] Figure 3 is a schematic diagram of a cooling system 20 according to one embodiment of the present invention. The cooling system 20 is similar to the cooling system 10. Unlike the cooling system 10, the cooling system 20 employs multiple coolant droplet inlets 112 to distribute the cooling resources (i.e., coolant droplets) more uniformly than the cooling system 10, thereby preventing the droplets from completely evaporating in some areas of the channel 115 and preventing the temperature from rising far above the boiling point.

[0031] It should be noted that the condenser 107 shown in Figures 2 and 3 resembles a radiator, but is not limited to these. The structure, shape, and type of the condenser 107 are not limited. For example, the condenser 107 shown in Figure 4 may include a tube having a repeating pattern of S-shaped curves. Furthermore, the diameter of the tube within the condenser 107 may gradually narrow from the inlet to the outlet.

[0032] The following describes some of the main differences between this invention and conventional (active) cooling systems. First, this invention achieves a high heat dissipation rate by utilizing the potential heat of the phase change between the liquid and gas phases. Second, this invention establishes an asymmetric pair of boiling points in channel 115 and dew points in condenser 107 by generating different pressures inside subspaces 115 and 107. The asymmetric pair is established because the decrease in pressure in channel 115 lowers the boiling point in channel 115, resulting in the vaporization of coolant droplets within channel 115. Conversely, the increase in pressure in condenser 107 raises the dew point in condenser 107, thereby causing the coolant gas to condense into coolant droplets or coolant liquid within condenser 107. In other words, the pressure difference created by the compressor 102 causes the boiling point of the coolant in the channel 115 to be lower than the dew point temperature of the coolant in the condenser.

[0033] In addition, this invention utilizes a gaseous transport medium to move coolant droplets (in liquid phase) within the channels of the cooling system, thereby enabling the coolant droplets (in liquid phase) to penetrate through and / or into any small openings / gaps. Furthermore, this invention does not rely solely on the coolant (liquid) as in the case of a two-phase immersion cooling system, but uses the atomization of the coolant droplet inlet 112 to generate a mist stream 114 or a mixture of air and liquid, thereby the coolant-infused mist-stream having a viscosity close to (as low as) the gaseous transport medium and a heat dissipation rate close to (as high as) the immersion liquid cooling.

[0034] In summary, this application proposes an active two-phase mist cooling system. The cooling system utilizes a coolant droplet inlet to form a mist stream and injects this mist stream into a channel surrounding a heat source, and uses a compressor to establish a pressure difference between the channel and a condenser. Asymmetric boiling and dew points are established (at the same temperature). The heat from the heat source is absorbed as latent heat of vaporization and released as latent heat of condensation, while at the same time it is possible to maintain the temperature in the channel surrounding the heat source within a specific (narrow) range.

[0035] Those skilled in the art will readily understand that numerous modifications and changes to the device and method are possible while maintaining the teachings of the present invention. Accordingly, the above disclosure should be construed as being limited only by the boundaries of the appended claims.

Claims

1. A cooling system, wherein the cooling system is A channel surrounding the heat source, A coolant droplet inlet configured to introduce coolant droplets into the channel, wherein the coolant droplets vaporize as a coolant gas in the channel due to the heat generated by the heat source, A compressor configured to pump air from a channel subspace to a condenser subspace, wherein the air includes the coolant gas, A condenser configured to condense the coolant gas into a coolant liquid, The coolant liquid is introduced into the coolant droplet inlet, The airflow from the condenser is transported toward the channel by passing through an air conduit, and the coolant liquid from the condenser is transported toward the channel by passing through a coolant conduit different from the air conduit. Cooling system.

2. The cooling system according to claim 1, wherein the coolant droplet inlet is configured to inject together the coolant droplets generated from the coolant liquid carried through the coolant conduit and the airflow carried through the air conduit to form a mist stream injected into the channel.

3. The cooling system according to claim 1, comprising a pressure regulating valve configured to adjust the pressure difference between the pressure corresponding to the channel subspace and the pressure corresponding to the condenser subspace.

4. The cooling system according to claim 1, further comprising a heat remover configured to remove the heat released by the condenser.

5. The cooling system according to claim 4, wherein the heat remover includes an air transfer device.

6. The cooling system according to claim 4, wherein the heat remover includes a cooling device.

7. The aforementioned coolant droplet inlet is Including the reservoir section and the misting section, The reservoir portion is configured to store the coolant liquid that is transported through the coolant conduit, The cooling system according to claim 1, wherein the misting portion is configured to inject the coolant droplets into the airflow carried through the air conduit.

8. The cooling system according to claim 1, comprising forming a mist stream and injecting the mist stream from the coolant droplet inlet into the channel.

9. The cooling system according to claim 8, wherein the mist stream includes a gas transport medium into which the suspended coolant droplets are injected.

10. The cooling system according to claim 1, wherein the compressor maintains a pressure difference between the channel subspace and the condenser subspace.

11. The cooling system according to claim 10, wherein the compressor maintains the pressure difference such that the boiling point of the coolant in the channel is lower than the dew point temperature of the coolant in the condenser.

12. The cooling system according to claim 1, wherein the heat source includes through-silicon vias (TSVs) in an integrated circuit (IC) package.

13. The temperature of the channel is maintained so as not to exceed a certain level or within a certain range. The cooling system according to claim 1, wherein the aforementioned specific level corresponds to the boiling point of the coolant at the pressure in the channel.

14. The cooling system according to claim 1, wherein the condenser includes a tube having a repeating pattern of S-shaped curves.

15. The cooling system according to claim 14, wherein the diameter of the tube in the condenser gradually narrows from the inlet to the outlet.

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