Passive cooling apparatus for cooling immersion fluid, power conversion apparatus including shape memory alloy heat engine, and related systems

Abstract

A passive fluid cooling system is provided, the passive fluid cooling system comprising: a submerged cooling tank, the submerged cooling tank comprising a volume of fluid; and a shape memory alloy (SMA) heat engine including a plurality of wheels and an SMA wire coupled to the plurality of wheels. A portion of the SMA wire is in contact with a volume of fluid and transitions from a relaxed state to a tensioned state when a temperature of the volume of fluid exceeds a transition temperature of the SMA wire. Tensioning of the SMA wire causes the plurality of wheels to rotate and cause movement in the volume of fluid, and causes a temperature reduction of the volume of fluid.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit and priority of U.S. Provisional Application No. 63 / 504,904, filed May 30, 2023, entitled “Passive Cooling Apparatus for Cooling of Immersion Fluid and Power Conversion Equipment Including a Shape-Memory Alloy Heat Engine and Related Systems,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates generally to submerged fluids, and more specifically to the cooling of submerged fluids. Background Technology

[0004] The most common method for cooling information technology (IT) equipment, such as devices in data centers and power conversion equipment, is forced air. Using air as a coolant typically requires components such as fans, duct systems, heated ventilation, and air conditioning (HVAC) systems, which can consume significant space and electricity and often increase costs.

[0005] An alternative to using air to cool equipment is immersion cooling, which is more energy-efficient and space-saving. Immersion cooling involves submerging system components in a fluid that ideally has a high thermal absorption coefficient and low thermal resistance. Furthermore, this process typically requires the use of fluids that will not damage IT components or degrade system functionality. For safety reasons, these fluids need to be "dielectric," meaning they are non-conductive. Currently, dielectric fluids used for immersion cooling generally fall into two categories: oils (synthetic, mineral, biological) and engineered fluids.

[0006] Immersion cooling methods involve submerging components and / or equipment in a dielectric fluid. Heat generated by the IT components is absorbed by the fluid, which is then pumped and circulated throughout the housing, chassis, or tank to aid in heat removal. This method requires further pumping of hot oil / fluid to be cooled by an auxiliary air-liquid or liquid-liquid heat exchanger, and the cooled oil / fluid is pumped back into the immersion bath. Some methods involve a fully enclosed IT chassis containing the dielectric fluid, and therefore typically require less fluid. Other methods involve fully enclosed IT tanks / immersion tanks. The tank provides containment of the dielectric fluid and is typically designed to house IT components that would otherwise be rack-mounted. Because immersion tanks accommodate virtually all types of IT components, there is no need to replace the immersion tank for IT upgrades. This makes immersion tanks extremely attractive in terms of flexibility and cost compared to chassis methods. While immersion cooling is available, further improvements are needed. Summary of the Invention

[0007] Some embodiments of the present invention provide a passive fluid cooling system comprising: an immersion cooling tank containing a volume of fluid; and a shape memory alloy (SMA) heat engine including a plurality of wheels and SMA wires connected to the wheels. A portion of the SMA wire is in contact with the volume of fluid, and when the temperature of the fluid exceeds the transition temperature of the SMA wire, the portion of the SMA wire transitions from a relaxed state to a taut state. The tautness of the SMA wire causes the wheels to rotate and induce motion within the volume of fluid, resulting in a decrease in the temperature of the fluid.

[0008] In another implementation, multiple wheels can remain in motion until the temperature of a certain volume of fluid drops below the transition temperature of the SMA wire.

[0009] In some other embodiments, the plurality of wheels may include a first pulley and a second pulley, wherein the first pulley is larger than the second pulley, and wherein the second pulley is immersed in a volume of fluid.

[0010] In some embodiments, the multiple wheels may include a first blade and a second blade, wherein the first blade is larger than the second blade, and wherein the second blade is exposed in a volume of fluid.

[0011] In another embodiment, the SMA may include nitinol.

[0012] In some other implementations, the fluid velocity inside the immersion cooler tank and the air velocity above the external radiator caused by the SMA heat engine can increase the heat transfer capacity of the passive cooling system.

[0013] In some implementations, the SMA heat engine can draw power from the temperature difference between the inside and outside of the immersion cooling tank.

[0014] In another implementation, the SMA heat engine can generate flow rates in the submerged cooling tank without requiring additional external power.

[0015] In yet another embodiment, the fluid may be thermally conductive and electrically insulating.

[0016] In some embodiments, the immersion cooling tank may further include electronic components positioned within the immersion cooling tank, and the cooled volume of fluid may cool the electronic components positioned within the immersion cooling tank.

[0017] It also provides related heat engines. Attached Figure Description

[0018] FIG. 1A This is a diagram illustrating an immersion tank comprising multiple fluid cooling channels according to some embodiments of the present invention.

[0019] FIG. 1B This is a diagram illustrating one of a plurality of fins according to some embodiments of the present invention.

[0020] FIG. 2A This is a cross-sectional view illustrating an immersion tank including components and a coolant and having fins, according to some embodiments of the present invention.

[0021] FIG. 2B yes FIG. 2A A perspective view of the system, illustrating a three-dimensional representation of a tank and its components according to some embodiments of the present invention.

[0022] FIG. 3A to FIG. 3C These are diagrams illustrating velocity contour plots, temperature contour plots, and velocity vector plots, respectively, illustrating various aspects of cooling using immersion fluid according to some embodiments of the present invention.

[0023] FIG. 4A This is a diagram illustrating an immersion tank with a hollow fluid cooling channel according to some embodiments of the present invention.

[0024] FIG. 4B It is a embodiment of the concept of the present invention having FIG. 4A The diagram shows a cross-sectional view of the immersion tank with a hollow channel.

[0025] FIG. 4C yes FIG. 4B A three-dimensional view of a cross-section, showing a tank and its components according to some embodiments of the invention.

[0026] FIG. 5A to FIG. 5C are graphs illustrating velocity contour plots, temperature contour plots, and velocity vector plots for embodiments in accordance with the present inventive concept. FIG. 4A to FIG. 4C

[0027] FIG. 6A and FIG. 6B are graphs illustrating flat external channels with connecting fins in accordance with some embodiments of the present inventive concept.

[0028] FIG. 7 are graphs illustrating heat engines in accordance with some embodiments of the present inventive concept.

[0029] FIG. 8 and FIG. 9 are graphs illustrating passive immersion cooling systems including SMA heat engines in accordance with some embodiments of the present inventive concept.

[0030] FIG. 10 and FIG. 11 are graphs illustrating alternative embodiments of passive immersion cooling systems including SMA heat engines in accordance with some embodiments of the present inventive concept. DETAILED DESCRIPTION

[0031] The present inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which illustrative embodiments of the inventive concept are shown. The inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like reference numerals refer to like elements throughout. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Similarly, as used herein, the word "or" is intended to encompass inclusive and exclusive "or" conditions. In other words, A or B or C includes any or all combinations of the following alternative sets as appropriate for a given use: A alone; B alone; C alone; A and B only; A and C only; B and C only; and A, B, and C.

[0032] ​The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the inventive concept. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well. It will also be understood that the terms “comprising” and / or “including” as used in this specification specify the presence of the set forth features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0033] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which the inventive concept pertains. It will also be understood that, unless expressly defined herein, terms such as those defined in common dictionaries shall be interpreted as having the same meaning as they have in the relevant field and in the context of this specification, and shall not be interpreted as having an idealized or overly formal meaning.

[0034] Reference will now be made in detail to various exemplary and alternative exemplary embodiments, as well as the accompanying drawings. Each exemplary embodiment is provided by way of explanation rather than limitation. It will be apparent to those skilled in the art that modifications and variations may be made without departing from the scope or spirit of this disclosure and the claims. For example, a feature illustrated or described as part of an embodiment may be used in combination with another embodiment to produce yet another embodiment. Therefore, this disclosure is intended to include modifications and variations that fall within the scope of the appended claims and their equivalents.

[0035] As discussed above, power conversion devices and electronic components typically use fan cooling, which uses forced air delivered by a fan to a heat sink to dissipate heat generated by the components. More recently, immersion-cooled electronics use active components to cool the fluid, thereby cooling the immersion electronics. The immersion fluid is typically pumped through an immersion container and then to a heat exchanger to remove heat from the fluid. However, the fluid usually has to be pumped around, and heat exchangers must be used to remove heat from the liquid.

[0036] Accordingly, some embodiments of the inventive concept provide a passive fluid cooling apparatus that cools the immersion fluid without the need for additional equipment, such as a heat exchanger. As will be discussed below, embodiments of the inventive concept take advantage of the fact that when the temperature of a fluid, such as a dielectric, in a tank increases, the density of the fluid decreases. Accordingly, the heated fluid rises to the top of the tank and is cooled by circulating the fluid through an external tube (fluid cooling channel). This external arrangement of the tube allows for dissipation of heat without the use of any fans or pumps, which significantly increases the power usage effectiveness and efficiency of the immersion electronic assembly, as will be discussed below with respect to the drawings.

[0037] Referring first to FIG. 1A and FIG. 1B An immersion tank 100 and a plurality of fluid cooling channels 110 according to some embodiments of the inventive concept will be discussed. As FIG. 1A illustrated in , the immersion tank 100 is provided with a plurality of fluid cooling channels 110 attached to the immersion tank 100. As used herein, "immersion cooling" is an information technology (IT) cooling practice by which IT components including complete servers and storage devices as well as power equipment and other electronics are immersed in a thermally conductive but electrically insulating dielectric liquid or coolant. Traditionally, heat is removed from the system by circulating a relatively cool liquid into direct contact with the hot components and then circulating the now heated liquid through a cold heat exchanger. Unlike many other applications, water cannot be used for cooling as traditional water is electrically conductive and would damage the electronic components. Fluids suitable for immersion cooling have electrically insulating properties to ensure that they can be safely in contact with live electronic components.

[0038] The immersion cooling tank 100 is a tank in which electronic components are housed and filled with a dielectric liquid, where the electronic components are immersed in the dielectric liquid. Accordingly, various electronic components can share the same liquid. As used herein, a liquid or fluid can include any liquid, fluid, oil, etc. that can be safely used to cool electronic equipment. The immersion cooling tank is completely sealed and can typically be opened from the top to service the IT equipment therein.

[0039] Unlike traditional immersion cooling systems, embodiments of the inventive concept include one or more tubes 110 attached to the tank 100 that allow the fluid in the tank 100 to be circulated such that the fluid is cooled. An embodiment of a finned tube (fluid cooling channel) 110 according to some embodiments of the inventive concept is illustrated, for example, in FIG. 1B As illustrated therein, the tube 110 is provided with a plurality of fins attached to the outside of the tube 110. Embodiments are not limited to FIG. 1A and FIG. 1BThe specific number of fins shown. The external arrangement of tube 110 on tank 100 allows for heat dissipation from the liquid without the use of any fans or pumps, which significantly increases the power utilization effectiveness and efficiency of the submersible electronic components.

[0040] In particular, such as FIG. 1A and FIG. 1B As illustrated, pipe 110 is attached to both the top and bottom of tank 100. When the temperature of the fluid inside the tank, such as a dielectric, rises, the fluid density decreases, causing the less dense fluid to rise to the top of tank 100. The fluid at the top of tank 100 is filtered / circulated through pipe 110 and re-enters tank 100 at the bottom. The movement of the fluid through external pipe 110 lowers its temperature, allowing it to continue cooling the components positioned within the tank.

[0041] Now refer to FIG. 2A As illustrated in the cross-sectional view of tank 100, components 130 and 135 are immersed in coolant / fluid 120, such as a dielectric liquid. As used herein, "component" means any electrical component that can generate heat and is typically cooled in a conventional manner. For example, components discussed herein may include uninterruptible power supplies (UPS), such as single-phase and three-phase UPSs, motor drives, or any other power conversion devices. Although... FIG. 2A Only two components 130 and 135 in can 100 are shown in the illustration, but the embodiments of the present invention are not limited to this configuration. A single component or more than two components may be positioned in can 100 without departing from the scope of the present invention.

[0042] The heat associated with components 130 and 135 is transferred to the surrounding dielectric fluid (coolant 120). The temperature used in immersion cooling is determined by the highest temperature at which the immersed device can operate reliably. For servers, this temperature range may be between 15°C and 65°C (59°F to 149°F), but may extend to 75°C. The heat transferred to the coolant increases the temperature of the coolant 120 near component 120, which causes a decrease in the density of the coolant 120. The coolant 120 rises due to the resulting buoyancy. The rising coolant 120 in the tank causes a circulating flow through the external pipe 110. The heat in the fluid is absorbed by the fins ( FIG. 1B With the help of the fins, heat is transferred to the surrounding air, which increases the area available for heat transfer.

[0043] FIG. 2B yes FIG. 2A A three-dimensional view of the cross-section of tank 100. FIG. 2B The diagram illustrates the x, y, and z dimensions of tank 100. This allows for a more accurate depiction of the positioning of parts and other components.

[0044] FIG. 3A to FIG. 3C are velocity contour plots, temperature contour plots, and velocity vector plots, respectively, illustrating aspects of the inventive concept. FIG. 3C The vector plots illustrate the induced circulation flow within the tank and through the tube.

[0045] Although the fluid cooling channels 110 are shown in FIG. 1A to FIG. 2B as having a fin configuration, embodiments of the inventive concept are not limited to this configuration. For example, any type or shape can be used for the fluid cooling channels without departing from the scope of the inventive concept. Thus, any embodiment in which one or more cooling channels are attached to the immersion tank can be used. The fluid cooling channels can be, for example, radial disks with holes, fractal designs, etc. Further, the fluid cooling channels can have one or a combination of the following cross-sections: circular, rectangular, racetrack-shaped, etc. In FIG. 4A to FIG. 4C examples of various embodiments of fluid cooling channels are illustrated. Embodiments are not limited to those illustrated in these figures, and these figures are provided as examples only.

[0046] With particular reference to FIG. 4A to FIG. 4C , these figures illustrate a hollow channel embodiment for fluid cooling channels according to some embodiments of the inventive concept. As FIG. 4A illustrated in, an external flat channel 115 is formed in or attached to the side of the tank 100. In these embodiments, the passageway inside the flat channel 156 directs fluid to expel heat to the surrounding air. The circulation flow in the tank 100 and the external channel 115 is the same or similar to the circulation flow in the tank and tube as discussed above.

[0047] FIG. 5A to FIG. 5C are graphs illustrating velocity contour plots, temperature contour plots, and velocity vector plots, respectively, for embodiments of the inventive concept according to some embodiments of the inventive concept. FIG. 4A to FIG. 4C

[0048] FIG. 6A and FIG. 6B are a graph and a perspective cross-sectional view, respectively, of an embodiment including a flat channel and connecting fins. As FIG. 6A illustrated in , the flat channel 115 has fins 116 (aluminum plates) connected to each other to increase surface area, thereby enhancing heat transfer, as shown in FIG. 3A to FIG. 3C and FIG. 5A to FIG. 5C . Further, FIG. 6B a baffle 170 is illustrated for replacing fluid or removing / adding components.

[0049] In some embodiments, the tank itself can be made to include features that direct less dense fluids into the fluid cooling channels as discussed herein. For example, in some embodiments, a portion of the top of the tank can be angled downward to facilitate the entry of fluid into the fluid cooling channels. In addition, additional features such as baffles can be installed inside the tank 100 to help direct the flow of heated coolant 120, thereby enhancing the effectiveness of the tank 100. These baffles can be integral parts of the tank 100 structure or can be installed separately. These baffles can be custom configured depending on the components or equipment being cooled. The equipment being installed can also have separate features that help direct the coolant 120 to improve cooling efficiency.

[0050] As discussed above, conventional immersion-cooled electronic equipment uses active elements to cool the fluid, and thereby cool the immersed electronics. The immersion fluid is typically pumped through the immersion vessel (tank) and then to a heat exchanger to remove heat from the fluid. Embodiments of the present inventive concept provide a passive fluid-cooled device that reduces the power consumption of immersion-cooled equipment and expands the possible installation location options for IT equipment.

[0051] In particular, immersion cooling reduces energy consumption by eliminating air-cooling infrastructure, including onboard server fans, CRACs, A / C compressors, air circulation fans, necessary ductwork, air handlers, and other active auxiliary systems such as dehumidifiers. As discussed above, embodiments of the present inventive concept replace these conventional systems with liquid immersion technology with a passive cooling system for the fluid in the tank. Thus, embodiments of the present inventive concept do not require fans to circulate dielectric liquid nor do they require a heat exchanger to cool the liquid.

[0052] As discussed above with respect to FIGS. 1-3, FIG. 6A In passive immersion cooling, electronic components or other heat-generating components are immersed in a dielectric fluid coolant. The components heat the fluid during operation, and this heat causes a flow in the immersion vessel (tank). In some embodiments, the induced flow circulates the hot fluid through an external heat sink where the hot fluid releases heat to the atmosphere, as shown for example in FIG. 2A However, because the motion of both the coolant and the air is by natural circulation, the amount of heat that can be removed by the device can be limited by the naturally induced flow inside the tank.

[0053] Accordingly, some embodiments of the inventive concept use shape memory alloys (SMAs) to create a fluid mover that draws power from temperature differences and does not require an external power source to operate. Accordingly, these embodiments induce flow rates in passive immersion cooling systems that typically have high temperature gradients due to local heating from the components being cooled and relatively low induced flow rates. The use of SMA fluid movers as discussed herein increases the flow of coolant in the vessel and thereby increases the capacity and performance of the system as will be discussed below with respect to FIG. 8 to FIG. 11 Further discussed below.

[0054] As discussed above, passive immersion cooling systems typically include a passive immersion tank 100 that includes a fluid 120, e.g., a dielectric fluid, that absorbs heat from electronic components 120, 130 and dissipates the heat to the external environment due to buoyancy forces generated inside the tank driving circulation. According to embodiments discussed herein, a fluid mover can be used to further stimulate the movement of the fluid. For example, FIG. 7 FIG. illustrates a SMA heat engine according to some embodiments of the inventive concept.

[0055] FIG. 7 FIG. illustrates a SMA, e.g., a Nitinol, heat engine 845. Nitinol is a metal alloy that can “remember” or change shape based on temperature. As illustrated, a loop of, e.g., Nitinol wire 850, is disposed on a first pulley / wheel 860 and a second pulley / wheel 865. The wheels 860, 865 are free to rotate. An applicable property of SMA wire is a change in shape, i.e., straightening, when heated above a transition temperature. In particular, when the wire 850 is heated, the wire 850 transitions from a relaxed state to a taut state. The smaller wheel 865 of this engine 845 is immersed in a hot fluid 870 (immersion fluid) that is hotter than the transition temperature of the SMA wire 850, while the larger wheel 865 is outside the tank in air that is below the transition temperature. Accordingly, this configuration will cause the wheels 860, 865 of the engine to rotate. As long as the liquid 870 is above the transition temperature of the SMA and the air is below the temperature of the SMA, the wheels of the engine will rotate. FIG. 7 The wire 850 is shown in a taut position.

[0056] It will be appreciated that the wire 850 is discussed herein as a Nitinol wire, however embodiments of the inventive concept are not so limited. For example, the wire 850 can be any type of SMA without departing from the scope of the inventive concept.

[0057] FIG. 8 FIG. illustrates a passive immersion cooling system including FIG. 7 the heat engine 845 of FIG.

[0058] FIG. 7The SMA heat engine 845 is used to move the fluid 870 so that the fluid 870 heated by the components 900 can be more rapidly cooled. FIG. 9 An embodiment is illustrated in which the vanes 1090 are attached to the SMA engine to provide pumping action inside the tank and air flow over the external radiator. As illustrated, the vanes 1090 can move up and down, as indicated by the dashed lines. However, it will be understood that embodiments of the inventive concept are not limited to this configuration.

[0059] Furthermore, although FIG. 8 and FIG. 9 The positioning of the engine 845 / 1090 at the upper corner of the tank is illustrated, but embodiments of the inventive concept are not limited thereto. For example, as FIG. 10 and FIG. 11 As shown in Figs. 11-13, the engine 1145 / 1290 can be positioned in different locations, and there can be more than one engine 1145 / 1290, without departing from the scope of the inventive concept.

[0060] The increase in fluid velocity inside the tank and air velocity over the external radiator caused by the SMA engine according to embodiments discussed herein enhances the heat transfer capability of the immersion cooling system. These advantages can be achieved without increasing external power.

[0061] As briefly discussed herein, some embodiments of the inventive concept use a shape memory alloy (SMA) engine to improve the function of a passive immersion cooling system to provide pumping action inside the tank. As discussed above, the SMA engine can be driven by heat dissipated by components in the tank.

[0062] In the drawings and specification, there have been disclosed exemplary embodiments of the inventive subject matter. Although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the inventive subject matter being defined by the following claims.

Claims

1. A passive fluid cooling system comprising: a submerged cooling tank comprising a volume of fluid; and a shape memory alloy (SMA) heat engine comprising a plurality of wheels and shape memory alloy wire coupled to the plurality of wheels, wherein a portion of the shape memory alloy wire is in contact with the volume of fluid and a portion of the shape memory alloy wire transitions from a relaxed state to a tensioned state when a temperature of the volume of fluid exceeds a transition temperature of the shape memory alloy wire; and wherein tensioning of the shape memory alloy wire causes the plurality of wheels to rotate and induce motion in the volume of fluid and causes a decrease in the temperature of the volume of fluid.

2. The system of claim 1, wherein, The plurality of wheels maintain motion until the temperature of the volume of fluid decreases below the transition temperature of the shape memory alloy wire.

3. The system of claim 1, wherein, The plurality of wheels comprise a first pulley and a second pulley, wherein the first pulley is larger than the second pulley, and wherein the second pulley is submerged in the volume of fluid.

4. The system of claim 1, wherein, The plurality of wheels comprise a first blade and a second blade, wherein the first blade is larger than the second blade, and wherein the second blade is submerged in the volume of fluid.

5. The system of claim 1, wherein, The shape memory alloy comprises Nitinol.

6. The system of claim 1, wherein, Fluid velocity inside the submerged cooling tank and air velocity above an external heat sink induced by the shape memory alloy heat engine increases a heat transfer capability of the passive cooling system.

7. The system of claim 1, wherein, The shape memory alloy heat engine draws power from a temperature difference between an inside and an outside of the submerged cooling tank.

8. The system of claim 1, wherein, The shape memory alloy heat engine induces flow rate in the submerged cooling tank without an increase in external power.

9. The system of claim 1, wherein, The fluid is thermally conductive and electrically insulating.

10. The system of claim 1, wherein, The submerged cooling tank further comprises an electronic component positioned in the submerged cooling tank, and wherein the volume of fluid being cooled cools the electronic component positioned in the submerged cooling tank.

11. A shape memory alloy (SMA) heat engine for use with a passive cooling system, the shape memory alloy heat engine comprising: a plurality of wheels and shape memory alloy wire coupled to the plurality of wheels, wherein a portion of the shape memory alloy wire is in contact with a volume of fluid and a portion of the shape memory alloy wire transitions from a relaxed state to a tensioned state when a temperature of the volume of fluid exceeds a transition temperature of the shape memory alloy wire; and wherein tensioning of the shape memory alloy wire causes the plurality of wheels to rotate and induce motion in the volume of fluid and causes a decrease in the temperature of the volume of fluid.

12. The engine of claim 11, wherein, The plurality of wheels maintain motion until the temperature of the volume of fluid decreases below the transition temperature of the shape memory alloy wire.

13. The engine of claim 11, wherein, The plurality of wheels comprise a first pulley and a second pulley, wherein the first pulley is larger than the second pulley, and wherein the second pulley is submerged in the volume of fluid.

14. The engine of claim 11, wherein, The plurality of wheels includes a first blade and a second blade, wherein the first blade is larger than the second blade, and wherein the second blade is submerged in the volume of fluid.

15. The engine of claim 11, wherein, The shape memory alloy includes nitinol.

16. The engine of claim 11, wherein, Fluid velocity inside the submersion cooling tank and air velocity above the external heat sink caused by the shape memory alloy heat engine increase the heat transfer capability of the passive cooling system.

17. The engine of claim 11, wherein, The shape memory alloy heat engine draws power from the temperature difference between the inside and outside of the submersion cooling tank.

18. The engine of claim 11, wherein, The shape memory alloy heat engine causes flow velocity in the submersion cooling tank without increasing external power.

19. The engine of claim 11, wherein, The fluid is thermally conductive and electrically insulating.

20. The engine of claim 11, wherein, The submersion cooling tank also includes electronic components positioned in the submersion cooling tank, and wherein the volume of fluid being cooled cools the electronic components positioned in the submersion cooling tank.

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