Electrohydrodynamic pump for pumping dielectric fluid

Abstract

The invention describes, inter alia, an EHD pump comprising at least a first electrode (200) and at least a second electrode (210). The first electrode includes a first grid (202), the second electrode includes a second grid (212), each of the first and second grids having grid openings formed by bridges (204, 214), where the second grid is asymmetric with respect to the first grid and has a different size with respect to the first grid.

Description

Technical Field

[0001] This disclosure relates to a pump for pumping dielectric fluid. Background Technology

[0002] Different technologies can be used to pump fluids, typically some type of pump. One pumping technology used for pumping fluids is called an electrohydrodynamic (EHD) pump. EHD pumps use an electric field to move the dielectric fluid. The moving fluid can often be used as a coolant in a thermal loop to dissipate heat generated by heat-generating components, such as electrical components. EHD pumps have very few parts and no moving parts. These characteristics make EHD pumps attractive in applications where system simplicity and robustness are paramount.

[0003] For example, WO 2017 / 127017 describes a circulating system using an EHD pump in a closed-loop system.

[0004] Technologies that could benefit from systems using EHD pumps to circulate fluids include satellites (such as communications satellites), which are approaching the technological limits of existing airborne thermal management systems. These satellites have increasing power dissipation requirements to meet the growing demands of broadcasting, broadband multimedia, and mobile communications services. Micro, nano, or “CubeSats” require low-mass heat dissipation from electronic components (on-chip satellites) and typically necessitate more compact thermal management systems to maintain high performance.

[0005] Technology that can benefit from systems based on using EHD pumps to circulate fluids also includes other heat-generating electronic devices (such as battery modules for automobiles, heavy equipment, peak shaving, and energy storage). It can also be used in applications such as electronic devices connected to radiators, finned radiators with forced or natural air convection cooling, and, moreover, in telecommunications equipment.

[0006] Active cooling systems that utilize forced flow of fluid can be used to improve cooling efficiency. Electrohydrodynamic (EHD) pumps can then be used, in which ionized particles or molecules interact with an electric field and power the flow of the dielectric fluid.

[0007] Although EHD pumps are known, there is still a need for improved EHD pumps. Summary of the Invention

[0008] The purpose of this invention is to provide an improved EHD pump.

[0009] This purpose and / or other purposes are achieved, at least in part, by the EHD pump as set forth in the appended claims.

[0010] As the inventors have recognized, an improved capacity of the EHD pump can be obtained by providing an EHD pump with collectors and emitters formed as a grid and by making the grid asymmetric.

[0011] According to the present invention, an EHD pump is provided. The EHD pump includes at least a first electrode and at least a second electrode. The first electrode includes a first grid, and the second electrode includes a second grid. Each of the first and second grids has a grid opening formed by bridging members, such that each of the first and second grids has at least one grid opening, said at least one grid opening being defined by bridging members on all sides of said grid opening, wherein the second grid is asymmetrical relative to the first grid, and the second grid has a grid opening size different from the size of the grid opening of the first grid. Thus, an EHD pump with a grid-like collector and emitter and improved performance can be provided. The EHD pump will be formed in a rigid and robust manner simultaneously because cables are provided to form the grids for both the emitter and collector.

[0012] According to one embodiment, the second grid has a different number of grid openings relative to the number of grid openings in the first grid. This allows for an easily achievable asymmetric grid configuration. Specifically, the second grid can have fewer grid openings than the first grid. For example, the second grid can be given only a single grid opening.

[0013] According to one embodiment, at least one electrode (e.g., an emitter electrode) may be provided with a mesh that extends (thickens) in the flow direction, such that the height (depth) of the bridging element seen in the flow direction is greater than the width seen in a direction orthogonal to the flow direction.

[0014] According to one embodiment, at least one of the first and second grids has at least one rectangular grid opening. Specifically, all grid openings can be rectangular grid openings. This results in an EHD pump that is easy to manufacture yet robust.

[0015] According to one embodiment, at least one bridging member has a protrusion on the side facing the grid opening. This provides additional asymmetry that can increase the flow capacity of the EHD pump. Furthermore, multiple protrusions can be provided. For example, at least one bridging member has multiple protrusions on the side facing the grid opening.

[0016] According to one embodiment, at least one mesh surface is provided with a thin film coating and / or surface modification. This can further improve the flow capacity of the EHD pump. Attached Figure Description

[0017] The invention will now be described in more detail by way of non-limiting example and with reference to the accompanying drawings, in which: - Figure 1 This is a view showing the pumping mechanism in the EHD pump. - Figure 2 This is a view of the asymmetric configuration of the pumping mechanism in the EHD pump according to the first embodiment. - Figure 3 This is a view of the asymmetric configuration of the pumping mechanism in the EHD pump according to the second embodiment. - Figure 4 This is a view of the asymmetric configuration of the pumping mechanism in the EHD pump according to the third embodiment, and - Figure 5 This is a view of the asymmetric configuration of the pumping mechanism in the EHD pump according to the fourth embodiment. Detailed Implementation

[0018] The invention will now be described more fully with reference to the accompanying drawings, in which certain embodiments of the invention are illustrated. However, the invention can 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 the disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. For example, the same or similar components in different embodiments may be interchanged between different embodiments. Some components may be omitted in different embodiments. Throughout the specification, the same numbers refer to the same elements. Furthermore, some well-known components may be omitted in the description so as not to obscure the content of this disclosure. For example, many conventional components commonly used in EHD pumps are not described. Such components may generally include, but are not limited to: - A spacer member that separates the emitter and collector to maintain them at a defined distance. The spacer member can be a non-conductive material, such as an insulator formed of ceramic or plastic materials; - Housing. The housing can surround the EHD pump body and can be made of plastic or metal materials; - A fixing structure that holds the pumping components in place; - Electrical connection assembly, which is used to connect the EHD pump to the drive circuit used to operate the EHD pump.

[0019] Other parts may also exist, depending entirely on the type of implementation.

[0020] It should be understood that features in different embodiments may be used in combination, and that no feature in an embodiment is required unless explicitly stated otherwise. Therefore, those skilled in the art may choose features and dimensions that they deem advantageous for a particular implementation.

[0021] exist Figure 1The image shows an EHD pump 100 as described in WO 2017 / 127017. The EHD pump 100 includes a first electrode or emitter 110, which includes a bridging member 111 and a connector 112 forming a mesh that allows fluid to flow through the emitter 110. The mesh can be formed by cables joined together, forming mesh openings with cables on all sides of the mesh openings. The emitter 110 can have a lateral extension in a plane perpendicular to the intended flow direction. Figure 1 In this configuration, the second electrode or collector 120 includes a bridging element 121 and a connector 122 arranged in a grid similar to that described with reference to the emitter 110. Therefore, the collector 120 can have a laterally extending extension in a plane perpendicular to the flow direction, such that the emitter 110 and the collector 120 are parallel to each other at a distance d. Thus, a first electrode can be present; and a second electrode biased from the first electrode in the downstream direction of the circulating fluid flow, the first and second electrodes being connectable to a voltage source V.

[0022] therefore, Figure 1 The structure of an EHD pump comprises two spaced-apart grids. The term "grid" here can generally refer to any structure including bridging elements joined together, such as, for example, a fence, mesh, or honeycomb structure. Bridging elements and joints define open areas of the grid that allow fluid to flow through; these open areas can also be referred to as grid openings. Therefore, the grid will have at least one grid opening defined by bridging elements on all sides of the grid opening. Bridging elements can typically be formed of cables, and the grid can then be referred to as a wire grid. An EHD pump can enhance the flow of dielectric fluid in a defined flow direction. The term "direction of flow" or "flow direction" generally refers to the primary direction of the net fluid flow resulting through the EHD pump during its operation. These terms can also be referred to as "intended flow direction."

[0023] Examples of fluids (i.e., liquids and gases) that can be pumped by example embodiments include, for example, dielectrics (e.g., acetone, alcohols, helium, nitrogen, esters) and fluorocarbon-based fluids (e.g., Fluorinert™ Novec™ or Opteon™).

[0024] The two grids of the EHD pump form the first electrode and the second electrode, respectively. The first electrode can also be called the "emitter" or "emitter electrode", and the second electrode can be called the "collector" or "collector electrode".

[0025] The first and / or second electrodes may comprise materials with relatively good electron emission capabilities and that are chemically stable or inert relative to the pumped fluid. Furthermore, the materials may possess relatively high heat resistance. Examples of such materials include, for instance, Pt, Ni, Ru, Rh, Pd, W, stainless steel, and any combination or alloy thereof.

[0026] The first electrode may include bridging elements and connectors forming a mesh structure. Furthermore, at least a portion of at least one bridging element may have a maximum height in a direction parallel to the flow direction and a maximum dimension in a direction orthogonal to the flow direction, wherein the maximum height may be greater than the maximum dimension.

[0027] By forming a grid of bridging elements with a relatively large height relative to their scale, the grid can be relatively rigid in terms of its ability to bear loads in the height direction of the bridging elements or in the direction of flow. This provides relatively rigid electrodes that are not easily bent or deformed, especially in the direction of flow, and thus reduces the risk of, for example, device short circuits. Furthermore, a relatively rigid and stable grid can still have a relatively large open area, which can provide relatively low flow resistance satisfied by the fluid passing through the grid. Further, relatively high and narrow bridging elements can reduce the amount of material required to form a relatively stable and rigid grid, which can reduce both the weight and cost of the device. By using a relatively rigid grid, the need for additional support structures can be reduced, and a relatively defined and constant spacing between the first and second electrodes can be achieved. The spacing can be, for example, in the range of 10-4000 pm, and more preferably in the range of 500-2000 pm. Due to its relatively large height, the bridging element also provides a relatively large contact surface between the grid structure and the passing fluid, which can facilitate any interaction between the electrodes and the fluid, such as material diffusion and / or the injection of ions or electrons.

[0028] The distance d or spacing between the first and second electrodes can be varied in order to control the intensity of the electric field induced between the electrodes.

[0029] Although Figure 1 While EHD pumps can meet many needs, there is always a desire to improve their performance. As has been found, improved flow can be provided in EHD pumps by providing both the first and second electrodes as a grid, wherein the grids of the first and second electrodes are asymmetrical relative to each other.

[0030] exist Figure 2 In the first exemplary embodiment, this asymmetric configuration of the first and second electrodes is shown. Figure 2In one embodiment, a first electrode 200 is provided as an emitter. Additionally, a second electrode 210 is provided as a collector. The first electrode 200 includes a first grid 202, and the second electrode 210 also includes a grid, a second grid 212. Therefore, both the first electrode 200 and the second electrode 210 include grids 202 and 212, but the grid 202 of the first electrode 200 has a different configuration than the grid 212 of the second electrode.

[0031] exist Figure 2 In an exemplary embodiment, the first grid 202 has a plurality of grid openings defined by the bridging member 204, which are combined with the above Figure 1 The description is the same. The second grid 212 has only a single grid opening defined by this bridging element 214. Improved flow in the pumping mechanism of the EHD pump can be achieved by configuring the grids 202, 212 asymmetrically, for example by having different numbers of grid openings, different types of grids (e.g., different sizes and / or shapes of the grid openings, or different sizes of the grids themselves). Figure 2 In an exemplary embodiment, the grid openings are rectangular. However, depending on the implementation, one or both of the grids may have other shapes (e.g., hexagonal).

[0032] According to one embodiment, at least one electrode (e.g., an emitter electrode) may be provided with a grid that extends (is thicker) in the flow direction, such that the height (depth) of the bridging element seen in the flow direction is greater than the width seen in a direction orthogonal to the flow direction. This configuration can improve the properties of the electric field in terms of corona discharge, a potential mechanism for accelerating the fluid between electrodes. In such an embodiment, the bridging elements will have different specifications in different grids 202 and 212. In other words, the height and / or width of the bridging elements between electrode grids 202, 212 can be different. In this configuration with bridging elements of different sizes in their respective grids 202, 212, the number and / or shape of the openings can also be different for their respective grids 202, 212.

[0033] This improvement can stem from the asymmetry of the electric bilayer formed in the surrounding fluid, preventing the accumulation of oppositely charged particles on the grid surface. The asymmetry also alters the electric field in the fluid, which can improve pump performance. Furthermore, the asymmetry makes the EHD pump more tolerant of particles and bubbles present in the fluid, as it can typically form larger openings while still maintaining performance. Figure 3 In the second exemplary embodiment, another asymmetric configuration of the first and second electrodes is shown. Figure 3In one embodiment, a first electrode 300 is provided as an emitter. Additionally, a second electrode 310 is provided as a collector. The first electrode 300 includes a first grid 302, and the second electrode 310 also includes a grid, a second grid 312. Figure 3 In an exemplary embodiment, the first mesh 302 has as described above. Figure 1 The description describes multiple mesh openings defined by bridging elements. The second mesh 312 has fewer mesh openings defined by such bridging elements, in this case only two.

[0034] exist Figure 4 In the third exemplary embodiment, yet another asymmetric configuration of the first and second electrodes is shown. Figure 4 In one embodiment, a first electrode 400 is provided as an emitter. Additionally, a second electrode 410 is provided as a collector. The first electrode 400 includes a first grid 402, and the second electrode 410 also includes a grid, a second grid 412. Figure 4 In an exemplary embodiment, the first mesh 402 has as described above. Figure 1 The description describes a plurality of mesh openings (typically at least 10 or more, for example at least 20) defined by bridging elements. The second mesh 412 also has a plurality of mesh openings defined by such bridging elements, but fewer mesh openings than the first mesh.

[0035] exist Figure 5 In the fourth exemplary embodiment, another asymmetric configuration of the first and second electrodes is shown. Figure 5 In one embodiment, a first electrode 500 is provided as a collector. Additionally, a second electrode 510 is provided as an emitter. The first electrode 500 includes a first grid 502, and the second electrode 510 also includes a grid, a second grid 512. Figure 5 In an exemplary embodiment, the first mesh 502 has as described above. Figure 1 and Figure 2 The description refers to multiple mesh openings defined by bridging elements. The second mesh 512 (the emitter in this configuration) in this example only has... Figure 2The diagram shows a single grid opening, and also includes at least one, and preferably multiple, protrusions 516 formed on at least one bridging member 514. The protrusions 516 facilitate flow in the pumping mechanism of the EHD pump because the electric field strength is locally higher at the narrow tips of the protrusions. The tips of the protrusions may be triangular in shape. The tips may point away from the bridging member 514, such that the tips are away from the bridging member and point towards the grid opening. According to some embodiments, multiple protrusions 516 are formed on at least one bridging member 514. According to one embodiment, the multiple protrusions 516 can be formed by forming a bridging member with a serrated side facing the grid opening. The emitter tip protrudes towards the collector grid opening.

[0036] The surfaces of the asymmetric emitter and collector grids, as described herein, can be coated. Surface coating of the emitter and / or collector grids can be advantageous. To modify performance and durability, the surface can be coated or the surface structure can be made to have a specific structure. For example, the surface can be coated with platinum, rhenium, ruthenium, lead, tungsten, or alloys and combinations of these materials. In another embodiment or as a supplement, the surface structure can be endowed with a specific structure. For example, the surface structure can be provided with microstructures (microneedles, micropyramids, other structures) produced by, for example, electroplating, sandblasting, acid treatment, heat treatment, roll impact, additive manufacturing, laser ablation, stamping, etc. Surface microstructures and / or coatings can further enhance pump performance by forming surfaces that more readily emit or absorb electrons. Coatings or modified surfaces can also be advantageous in terms of lifetime enhancement.

[0037] As described in this article, multiple EHD pumps can also be connected in series to increase or even increase the flow rate. Then, the distance between the EHD pumps should be at least equal to the distance between the grids of a single pump. Typically, the distance between two EHD pumps arranged in series can be 3 to 5 times the distance between the grids of a single pump.

[0038] Using an EHD pump with a grid structure for both the emitter and current collector, and an asymmetric configuration with two grids, can provide improved flow capacity while retaining the advantages offered by the emitter and current collector of the grid shape in the EHD pump. For example, a taller / thicker current collector is advantageous for capturing and neutralizing more charged particles in the fluid as it passes through. This is because it has a larger contact area with the fluid. This can allow for a higher pump pressure rise at higher flow rates because if the liquid is not sufficiently neutralized at each current collector, the charge will drift from one electrode pair to the next, providing a reverse pumping effect before the next emitter, where the electric field is locally reversed. The emitter generally does not benefit from height / thickness in any similar way, so the emitter is best kept shorter / thinner relative to the current collector.

[0039] Furthermore, due to the enhanced unidirectionality of the EHD pumping effect, asymmetry is advantageous in the sense of emitter grids decorated with sharp tips or edges and collectors with only flat or blunt surfaces.

[0040] Furthermore, by allowing for mesh asymmetry, larger openings can be permitted, allowing bubbles and particles to pass through more easily. When mechanical stability and electric field shape are taken into account, mesh asymmetry can further facilitate the construction of even larger mesh openings.

Claims

1. An EHD pump comprising at least a first electrode (200) and at least a second electrode (210), the first electrode comprising a first grid (202) and the second electrode comprising a second grid (212), each of the first grid and the second grid having a grid opening formed by bridging members (204, 214), such that each of the first grid and the second grid has at least one grid opening, the at least one grid opening being defined by bridging members on all sides of the grid opening, wherein the second grid is asymmetrical relative to the first grid, and the second grid (212) has a grid opening size different from the size of the grid opening of the first grid (202).

2. The EHD pump according to claim 1, wherein the second grid (212) has a grid opening shape that is different from the grid opening of the first grid (202).

3. The EHD pump according to claim 1 or 2, wherein the second grid (212) has a different number of grid openings than the number of grid openings of the first grid (202).

4. The EHD pump of claim 3, wherein the second grid (212, 412) has fewer grid openings than the first grid (202, 402).

5. The EHD pump according to claim 4, wherein one of the first grid (202) and the second grid (212) has only a single grid opening.

6. The EHD pump according to any one of claims 1 to 5, wherein at least one of the first grid (202) and the second grid (212) has at least one rectangular grid opening.

7. The EHD pump according to any one of claims 1 to 6, wherein at least one bridging member (514) has a protrusion (516) on the side facing the grid opening.

8. The EHD pump of claim 7, wherein the at least one bridging member has a plurality of protrusions (516) on the side facing the grid opening.

9. The EHD pump according to any one of claims 1 to 8, wherein at least one of the grids (202, 212) is elongated in the flow direction such that the height seen in the flow direction is greater than the width seen in a direction orthogonal to the flow direction.

10. The EHD pump according to any one of claims 1 to 9, wherein at least one of the grids (202, 212) has a surface provided with a thin film coating and / or surface modification.

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