Cooling device

Abstract

This cooling device comprises: a heat sink having multiple fins; and plasma actuators provided in flowpaths between the fins. Electrodes of the plasma actuators are offset from each other in the flowpath direction and the flows induced thereby are more intense toward the flowpath center than near the fins so that large amounts of air are introduced in the flowpaths and cooling efficiency is improved.

Description

[Technical Field]

[0001] The present invention relates to cooling devices, and more particularly to heat sinks with plasma actuators. [Background technology]

[0002] 2. Description of the Related Art A power conversion device such as a converter includes electronic components that generate heat, such as semiconductors, capacitors, and coils, and a heat sink is attached to cool these electronic components.

[0003] In recent years, there has been a demand for smaller and more powerful power conversion devices. When electronic components are densely arranged and made smaller, the density of heat-generating elements within the power conversion device increases. In addition, the amount of heat generated by the heat-generating elements increases as the power increases, so it is necessary to improve the performance of the heat sinks that cool these elements.

[0004] The cooling performance of a heat sink generally depends on its volume (heat capacity), material (thermal conductivity), and surface area (heat transfer area) depending on its shape. Therefore, if the heat sink itself is enlarged to improve its cooling performance, the entire power conversion device will become larger, making it difficult to miniaturize the power conversion device.

[0005] Patent document 1 discloses that by forming the fins of a heat sink in a desired shape relative to the direction of airflow, the airflow can be disturbed over the entire area from the base to the tip of the fin, preventing the airflow from stagnating and improving the heat dissipation performance of the heat sink. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2009-290004 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the heat sink in Patent Document 1 has fins that disrupt the airflow, resulting in large pressure loss, and in order to fully utilize the cooling performance of the heat sink, the airflow needs to be made stronger, requiring a large fan, making it difficult to miniaturize the power conversion device by improving the cooling efficiency of the heat sink.

[0008] The present invention has been made in consideration of the problems associated with the prior art, and its object is to provide a cooling device with high cooling efficiency that allows for miniaturization of power conversion devices and the like. [Means for solving the problem]

[0009] As a result of extensive research into achieving the above-mentioned objective, the inventor discovered that by generating an induced flow in the center of a flow path of a heat sink formed by multiple fins, a large amount of air can be introduced into the flow path, thereby achieving the above-mentioned objective, and thereby completed the present invention.

[0010] That is, the cooling device of the present invention comprises a heat sink having a flow path formed between adjacent fins; The device has a dielectric layer, a first electrode and a second electrode provided on the dielectric layer, and a power source that applies a voltage between the first electrode and the second electrode. and a plasma actuator. The plasma actuator is provided at a distance from the fins that form the flow path, The first electrode and the second electrode The electrodes are arranged offset in the flow path direction, and an induced flow that flows in the flow path direction is generated in the center between adjacent fins. [Effects of the Invention]

[0011] According to the present invention, an induced flow is generated in the center of the flow path of the heat sink, which allows a large amount of air to be introduced into the flow path, thereby providing a cooling device with high cooling efficiency that can reduce the size of the power conversion device. [Brief explanation of the drawings]

[0012] [Figure 1]FIG. 1 is a perspective view showing an example of a heat sink that can be used in the present invention. [Figure 2] 10 is a cross-sectional view showing an example of a plasma actuator provided in a flow path of a heat sink. FIG. [Figure 3] FIG. 10 is a cross-sectional view showing another example of a plasma actuator provided in a flow path of a heat sink. [Figure 4] FIG. 10 is a cross-sectional view showing an example of a state in which a plasma actuator is arranged in a flow path of a heat sink. [Figure 5] FIG. 10 is a cross-sectional view showing another example of a state in which a plasma actuator is arranged in a flow path of a heat sink. [Figure 6] FIG. 1 is a cross-sectional view showing an example of a plasma actuator in which the electric lines of force generated between electrodes are stronger in the center of the flow path. [Figure 7] 7 is a diagram showing an example of electric lines of force generated between the electrodes of the plasma actuator of FIG. 6. FIG. [Figure 8] 10A and 10B are diagrams illustrating the flow of an induced flow when multiple plasma actuators are arranged in a flow path. DETAILED DESCRIPTION OF THE INVENTION

[0013] The cooling device of the present invention will now be described in detail. The cooling device of the present invention comprises: a heat sink having flow paths formed between adjacent fins; and a plasma actuator.

[0014] The heat sink shown in Figure 1 is a heat sink in which multiple flat fins are arranged in parallel and erected on a base plate, and a support plate (not shown) is provided on the top of the fins, which, together with the base plate, forms a flow path through which air flows between the fins.

[0015] In the plasma actuator of the present invention provided in the above-mentioned flow path, a plurality of electrodes are provided offset in the flow path direction, so that the electric field generated between these electrodes is biased in the flow path direction.

[0016] Therefore, when an AC voltage is applied between the electrodes and an atmospheric pressure barrier discharge is generated, the positive ions or electrons of the low-temperature plasma are accelerated in one direction by the electric field biased in the flow path direction, and these ions or electrons collide with surrounding air molecules, generating an induced flow in the flow path direction (the X-axis direction in Figure 1).

[0017] Furthermore, in the cooling device of the present invention, the induced flow generated by the plasma actuator flows between adjacent fins rather than near the fins, i.e., toward the center of the flow path (the center in the Y-axis direction in Figure 1), so there is less friction between the induced flow and the fins and the flow rate of the induced flow is less likely to decrease, thereby increasing the suction force that draws air outside the flow path into the flow path.

[0018] In other words, the air in the flow path downstream of the plasma actuator is pushed out by the induced flow, and air is drawn into the flow path upstream, increasing the amount of air flowing in the flow path and improving heat transfer from the fins to the air, thereby improving cooling efficiency. Therefore, the cooling device of the present invention does not require a large fan, making it possible to reduce the size of power conversion equipment and the like.

[0019] In the present invention, the "center of the flow path" refers to an area away from the fins, and does not mean the center line of the flow path, and the point where the induced flow is strongest may be shifted from the center line of the flow path.

[0020] Examples of plasma actuators that generate an induced flow in the center between adjacent fins include a plasma actuator installed in the center of the flow path, and a plasma actuator in which electrodes are arranged on the fins that form the flow path so that the electric field lines generated between the electrodes are stronger in the center of the flow path.

[0021] First, the plasma actuator provided in the center of the flow path will be described. The plasma actuator provided in the center of the flow path has, for example, a dielectric layer, an upstream electrode, and a downstream electrode, as shown in Figure 2, where the upstream electrode is exposed on the surface of the dielectric layer and the downstream electrode is contained within the dielectric layer, and the downstream electrode is provided offset from the upstream electrode in the in-plane direction of the dielectric layer.

[0022] Therefore, when an AC voltage is applied to the plasma actuator, an atmospheric pressure barrier discharge occurs on the surface where the upstream electrode is exposed, and the electric field generated between the offset electrodes is biased in the direction of the flow path. This electric field tends to accelerate positive ions or electrons from the upstream electrode toward the downstream electrode in the in-plane direction of the dielectric layer, generating an induced flow in one direction.

[0023] By placing this plasma actuator at a distance from the fins that make up the flow path and parallel to the fins so that the induced flow faces the flow path direction (X-axis direction), the induced flow can be generated in the center of the flow path.

[0024] Furthermore, the plasma actuator provided in the center of the flow path can be not only one that generates an induced flow on one side as shown in FIG. 2, but also one that generates an induced flow on both sides.

[0025] For example, as shown in Figure 3, by providing upstream electrodes exposed from the dielectric layer on both the front and back surfaces of the dielectric layer and providing downstream electrodes embedded in the dielectric layer at positions offset from these upstream electrodes, induced flows are generated on both sides of the plasma actuator, thereby improving the suction force that draws air into the flow path.

[0026] It is preferable that the length of the plasma actuator in the flow path direction is shorter than the length of the flow path. As the length of the plasma actuator increases, the generated induced flow experiences friction with the surface of the plasma actuator, and the flow velocity of the induced flow slows as it moves away from the point where the induced flow is generated, which tends to reduce the suction force that draws air into the flow path.

[0027] The depth of the plasma actuator in the height direction (Z-axis direction) of the flow path may be the same as the height of the flow path or may be shorter than the height of the flow path, but if it is the same as the height of the flow path, an induced flow can be generated throughout the entire height of the flow path, thereby increasing the suction force that draws air into the flow path.

[0028] The thickness of the plasma actuator is preferably 20% or less of the flow path width, that is, the distance between adjacent fins in the Y-axis direction. By making the thickness of the plasma actuator 20% or less of the width of the flow path, the plasma actuator is less likely to obstruct the flow of air within the flow path, and the increase in pressure loss caused by the plasma actuator is suppressed, improving cooling efficiency.

[0029] Furthermore, the distance between the surface of the plasma actuator and the surface of the fin is preferably 10 mm or less. If the distance between the surface of the plasma actuator where the induced flow is generated and the fin is too great, the area where the induced flow is generated becomes small relative to the width of the flow path, and the suction force that draws air into the flow path tends to decrease. Here, the "surface of the plasma actuator" refers to the surface on which the induced flow occurs.

[0030] The plasma actuator may be arranged upright on the base plate of the heat sink, as shown in Figure 4, or may be arranged upright on a support plate separate from the heat sink, as shown in Figure 5, and inserted between the fins and placed within the flow path.

[0031] When the plasma actuator is provided upright on the base plate of the heat sink, the plasma actuator itself can function as part of the heat sink, improving cooling efficiency.

[0032] Furthermore, by inserting a plasma actuator standing on a support plate into the flow path, a plasma actuator can be attached to a general comb-shaped heat sink, and commercially available heat sinks can be used, thereby reducing costs.

[0033] Furthermore, an example of a plasma actuator in which electrodes are arranged so that the electric field lines are stronger in the center of the flow path is a plasma actuator formed by a first electrode provided on a fin on one side that constitutes the flow path, a second electrode provided on a fin on one side downstream of this first electrode, and a third electrode provided on a fin on the other side.

[0034] As shown in Figure 6, in this plasma actuator, a first electrode provided on one fin is exposed from the dielectric layer, and a second electrode provided on the same fin on the same side as the first electrode and a third electrode provided on the fin on the other side are covered by the dielectric layer.

[0035] Since the potentials of the second electrode and the third electrode are of opposite polarity to that of the first electrode, an atmospheric pressure barrier discharge occurs between the first electrode and the second electrode or the third electrode, generating low-temperature plasma.

[0036] This low-temperature plasma is accelerated by the electric field formed between the electrodes, generating an induced flow. By adjusting the positions of the second and third electrodes relative to the first electrode and the potentials of the second and third electrodes so that the electric field is directed toward the center of the flow path, an induced flow can be generated in the center of the flow path, thereby reducing pressure loss caused by the plasma actuator.

[0037] FIG. 7 shows an example of electric lines of force formed between the first electrode and the second and third electrodes when the second and third electrodes have the same potential.

[0038] As shown in Figure 7, by providing a third electrode of the same polarity as the second electrode on the other fin, which is different from the fin on which the first and second electrodes are provided, the electric field lines are pulled toward the third electrode and directed toward the center of the flow path, thereby generating an induced flow in the center of the flow path.

[0039] As shown in Figure 8, the cooling device of the present invention can be provided with a plasma actuator on the fin that generates an induced flow near the fin, in addition to the plasma actuator that generates an induced flow in the center of the flow path.

[0040] The induced flow generated by the plasma actuator not only slows down as it moves downstream due to friction with the fins, but also forms a boundary layer with a slow flow rate on the surface of the fins, reducing heat transfer from the fins to the air.

[0041] By providing a plasma actuator that generates an induced flow near the fin, the induced flow can be re-accelerated and the generation of a boundary layer can be suppressed, thereby preventing a decrease in cooling efficiency due to the boundary layer.

[0042] The configuration of the plasma actuator that generates an induced flow near the fin is the same as the plasma actuator shown in FIG. 2, except that the plasma actuator is provided on the fin.

[0043] The plasma actuator that generates an induced flow near the fin is preferably provided downstream in the induced flow direction from the plasma actuator that generates an induced flow in the center of the flow path rather than near the fin.

[0044] As the induced flow generated by the plasma actuator that generates an induced flow in the center of the flow path moves downstream, the difference in speed between the center of the flow path and the vicinity of the fin causes the induced flow to spread from the center of the flow path throughout the entire flow path and move toward the vicinity of the fin.

[0045] As shown in Figure 8, a plasma actuator that generates an induced flow near the fin is provided downstream, accelerating the flow near the fin, which causes the airflow to flow throughout the entire flow path, improving cooling efficiency.

[0046] Note that Figure 8 shows one plasma actuator that generates an induced flow in the center of the flow path rather than near the fins, and one plasma actuator that generates an induced flow near the fins, but it is also possible to provide multiple of these plasma actuators depending on the flow path length. Furthermore, the positions of the plasma actuators provided in adjacent flow paths separated by fins may be the same or different between the adjacent flow paths.

[0047] The cooling device of the present invention can include a fan that sends a main flow through the flow path in the same direction as the induced flow. By sending the main flow to the heat sink with the fan, in combination with the plasma actuator, the amount of air introduced into the flow path increases, improving cooling efficiency.

[0048] The cooling device of the present invention has been described with reference to an example in which the fins of the heat sink are flat fins, but as long as a flow path is formed, the fins are not limited to flat fins and offset fins or pin fins may also be used. [Explanation of symbols]

[0049] 1 heat sink 11 Base Plate 12 Finn 13 Support plate 14 Flow path 2 Plasma Actuator 2a Plasma actuator that generates an induced flow in the center of the flow channel 2b Plasma actuator that generates an induced flow near the fin 21 Upstream electrode 22 Downstream electrode 23 Dielectric layer 24 1st electrode 24e Charge on the first electrode 25 2nd electrode 25e Charge on the second electrode 26 3rd electrode 26e Charge on the third electrode 27 Plasma 28 Induced flow 3 AC power supply 4 Fans 41 Mainstream 5 Heating element

Claims

1. a heat sink having flow paths formed between adjacent fins; A cooling device comprising: a plasma actuator having a dielectric layer, a first electrode and a second side electrode provided on the dielectric layer, and a power supply that applies a voltage between the first electrode and the second electrode, a cooling device characterized in that the plasma actuator is provided at a distance from the fins that form the flow path, the first electrode and the second electrode are arranged offset in the flow path direction, and an induced flow that flows in the flow path direction is generated in the center between adjacent fins.

2. 2. The cooling device according to claim 1, wherein the length of the plasma actuator in the flow path direction is shorter than the length of the flow path.

3. 3. The cooling device according to claim 2, wherein the thickness of the plasma actuator is 20% or less of the width between the fins.

4. 4. The cooling device according to claim 2, wherein the distance between the surface of the plasma actuator and the surface of the fin is 10 mm or less.

5. 5. The cooling device according to claim 2, wherein the plasma actuator is provided upright on a base plate of the heat sink.

6. 6. The cooling device according to claim 2, wherein the plasma actuator is provided upright on a support member and inserted between the fins.

7. A cooling device comprising: a heat sink having a flow path formed between adjacent fins; and a plasma actuator, the plasma actuator includes a first electrode provided on one of the fins and exposed from a dielectric layer, and a second electrode and a third electrode provided downstream in the flow path direction from the first electrode and covered with a dielectric layer; the second electrode is provided on the same one of the fins as the first electrode; the third electrode is provided on the other fin, the second electrode and the third electrode have potentials of opposite polarity to the first electrode; A cooling device characterized in that an induced flow that flows in the flow path direction is generated in the center between the adjacent fins.

8. 8. The cooling device according to claim 7, wherein the second electrode and the third electrode have the same potential and are arranged at the same position in the flow path direction.

9. The cooling device according to any one of claims 1 to 8, further comprising a plasma actuator provided on the fin to generate an induced flow in the vicinity of the fin, in addition to the plasma actuator that generates an induced flow in the center between the adjacent fins.

10. 10. The cooling device according to claim 9, wherein the plasma actuator provided on the fin to generate an induced flow in the vicinity of the fin is provided downstream in the induced flow direction of the plasma actuator that generates an induced flow in the center portion between the adjacent fins.

11. Further, it has a fan, 11. The cooling device according to claim 1, wherein the fan causes an airflow in the same direction as the induced flow through the flow path.

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