Cooling device

Abstract

To provide a cooling device that can increase cooling efficiency and reduce power consumption of an airflow generating device.SOLUTION: A cooling device according to the present invention includes a heat sink having multiple flow paths formed between fins erected on a base plate, and an airflow generating device that causes airflow to flow through the flow paths. The fins that form the multiple flow paths include fins with multiple through holes that connect adjacent flow paths, and the airflow generating device generates airflows with different flow velocities at least between adjacent flow paths, and the airflow passes through the through holes in the fins. This makes it possible to provide a cooling device that can achieve both improved cooling efficiency and reduced power consumption of the airflow generating device.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cooling device, and more particularly to a cooling device including a heat sink and an airflow generating device that generates an airflow through a flow path in the heat sink. [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 power conversion devices with higher power output. When electronic components are densely packed together to reduce size, 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 the performance of the heat sinks that cool these elements also needs to be improved.

[0004] Patent Document 1 discloses a cooling device in which an airflow generating device such as a plasma actuator is provided on a heat sink, and induced flows are intermittently generated, which cause vortices on the surface of the fins to thin the thermal boundary layer formed near the surface of the heat sink, thereby increasing cooling efficiency and reducing power consumption by the airflow generating device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-158718 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the device described in Patent Document 1, the fins that form the flow paths of the heat sink are formed from flat plates, and each flow path is independent, so in order to increase the cooling efficiency for each flow path, the airflow generating devices provided in each flow path must be driven in the same way, and there are limits to reducing the power consumption of the airflow generating devices.

[0007] The present invention has been made in consideration of the problems associated with the prior art, and its purpose is to provide a cooling device that can improve cooling efficiency and further reduce the power consumption of the airflow generating device. [Means for solving the problem]

[0008] As a result of extensive research into achieving the above-mentioned object, the inventors discovered that the above-mentioned object can be achieved by providing through holes in the fins that form the flow paths to connect adjacent flow paths and by creating a difference in the flow speed of the airflow between the adjacent flow paths, and thus completed the present invention.

[0009] That is, the cooling device of the present invention comprises a heat sink having a plurality of flow paths formed between fins erected on a base plate, and an airflow generating device that causes airflow to flow within the flow paths. The fins forming the plurality of flow paths include fins having a plurality of through holes connecting adjacent flow paths, The airflow generating device is characterized in that it generates airflows whose flow velocities differ at least between adjacent flow paths. [Effects of the Invention]

[0010] According to the present invention, through holes are provided in the fins that form the flow paths to connect adjacent flow paths, and a difference is made in the flow speed of the airflow flowing between the adjacent flow paths so that the airflow passes through the through holes in the fins, thereby providing a cooling device that can achieve both improved cooling efficiency and reduced power consumption by the airflow generating device. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view showing an example of a cooling device of the present invention. [Figure 2] FIG. 1 is a schematic diagram of a plasma actuator. [Figure 3] FIG. 3 is a diagram illustrating the flow of air in the cooling device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The cooling device of the present invention will now be described in detail. As shown in FIG. 1, the cooling device of the present invention comprises a heat sink 2 and an airflow generating device 1, and optionally a fan for generating a main airflow.

[0013] The heat sink has a plurality of fins 21 standing on one main surface of a base plate 23, and a plurality of flow paths 24 formed between the fins. A heat generating element 5 (object to be cooled) is in contact with the other main surface of the base plate.

[0014] 1, the X-axis direction is the length direction of the flow channel and the direction of the airflow, the Y-axis direction is the width direction of the flow channel, and the Z-axis direction is the height direction of the flow channel.

[0015] The airflow generating device 1 causes an airflow to flow in the same direction as the main airflow in the longitudinal direction (X-axis direction) of the flow path, thereby suppressing the development of a thermal boundary layer 3 formed near the surface of the fin 21 and promoting heat dissipation from the heat sink 2.

[0016] The airflow generating device may be any device capable of generating an airflow for each flow path, and may be, for example, a plasma actuator or a micropump.

[0017] 2, the plasma actuator 1 has a covered electrode 12 and an exposed electrode 11 separated by a dielectric 13, which are offset in the in-plane direction of the main surface of the dielectric. A voltage is applied between the electrodes to cause a barrier discharge, generating an induced flow 15 in the in-plane direction of the main surface of the dielectric 13.

[0018] The above-mentioned plasma actuator has no moving parts and is thin, so it can be installed flush with the fin. It generates an induced flow along the surface of the fin and also generates the induced flow over the entire height of the fin (Z-axis direction), which can suppress the development of the thermal boundary layer and make it thinner, making it suitable for use.

[0019] In the cooling device of the present invention, the flow speed of the airflow through each flow path is not the same, and the flow speed of the airflow through at least one adjacent flow path is different, so a pressure difference occurs between the adjacent flow paths.

[0020] Furthermore, since multiple through holes are formed in the fins of the heat sink, the pressure difference between adjacent flow paths causes an airflow to pass through the through holes from the flow path with a faster airflow velocity to the flow path with a slower airflow velocity.

[0021] The airflow that passes through this through hole intersects with the thermal boundary layer formed near the surface of the fin and penetrates through the thermal boundary layer on the fin surface, thereby diffusing the thermal boundary layer with high efficiency and dramatically improving cooling efficiency.

[0022] In other words, the cooling device described in Patent Document 1, which is formed from flat plates and generates vortices in independent flow paths, can suppress the development of the above-mentioned thermal boundary layer and make it thinner, but the flow of the vortex is restricted by the fins and cannot penetrate the thermal boundary layer on the fin surface, so the thermal boundary layer cannot be eliminated.

[0023] As shown in Figure 3, in the cooling device of the present invention, at the location where the through hole 22 is formed, the air flow that passes through the through hole penetrates the thermal boundary layer 3, partially eliminating the thermal boundary layer 3 that inhibits heat transfer, resulting in a portion immediately downstream of the through hole 22 where the cooling efficiency is significantly high, thereby improving the cooling efficiency.

[0024] In addition, the plasma actuator can generate an induced flow not only within the flow path in which the plasma actuator is installed, but also in adjacent flow paths, thereby maximizing the cooling efficiency improvement effect of the plasma actuator and reducing the power consumption of the plasma actuator.

[0025] Methods for changing the flow rate of airflow in adjacent flow paths include providing a plasma actuator in only one of the adjacent flow paths, changing the output of adjacent plasma actuators provided in the adjacent flow paths, burst driving (intermittent driving) the plasma actuators to stagger the drive timing of adjacent plasma actuators, and a combination of these methods.

[0026] In the present invention, "the flow velocity of the airflow is different between adjacent flow paths" means that the flow velocity of the airflow flowing through a certain flow path may be different from the flow velocity of the airflow flowing through one of the flow paths adjacent to that flow path, and may be the same as the flow velocity of the airflow flowing through the flow path on the other side, and does not necessarily mean that the flow velocity of the airflow is different from the flow velocity of the airflow flowing through the flow paths on both sides adjacent to that flow path.

[0027] For example, if a plasma actuator is provided in only one of the adjacent flow paths, it is not necessary to provide a plasma actuator in every other flow path; there may be two flow paths without a plasma actuator between the flow paths with a plasma actuator.

[0028] As described above, by providing a flow path that does not have a plasma actuator, the number of plasma actuators in the entire cooling device can be reduced, which reduces the power consumption of the plasma actuators and also reduces costs.

[0029] In addition, by burst driving the plasma actuator, an induced flow is generated when the drive is on and stops when the drive is off, which creates a pressure difference in the direction of the induced flow, causing a flow in the opposite direction to the induced flow and generating a vortex.

[0030] As shown in Figure 3, this vortex flow oscillates in the Y-axis direction while hitting the fins 21 on both sides that form the flow path, not only thinning the thermal boundary layer 3 on both sides of the flow path that occurs near the fins 21, but also repeatedly changing the magnitude relationship of the pressure difference between adjacent flow paths.As a result, air flows back and forth between adjacent flow paths through the through holes 22 in the fins, partially eliminating the thermal boundary layer 3, thereby improving cooling performance.

[0031] In addition, since no power is consumed when the drive is off, power consumption can be reduced compared to when the drive is continuously driven.

[0032] The burst drive is performed by periodically switching on and off the AC voltage applied between the electrodes of the plasma actuator using a control device.

[0033] The fins may be made of punched metal or the like as long as they have a plurality of through holes, but are preferably made of lotus-shaped porous metal in which the diameters and positions of the through holes are irregular.

[0034] Lotus-type porous metal is a metal material produced by the melt solidification method. Molten metal is poured into a mold with a cooled bottom and a temperature gradient, and solidified in one direction. As the molten metal solidifies, the supersaturated gas bubbles that precipitate are aligned in one direction, forming a porous metal material with numerous cylindrical pores that extend in the same direction as the solidification.

[0035] By cutting this lotus-type porous metal in a direction perpendicular to the solidification direction, i.e., by cutting the cylindrical holes into ring slices, it is possible to produce fins with multiple through-holes connecting adjacent flow channels.

[0036] Fins made of lotus-type porous metal have not only large through holes that allow airflow between adjacent flow paths, but also fine holes, which increases the surface area of ​​the fins, improving cooling efficiency and reducing weight.

[0037] The fins preferably have a porosity of 50 to 70% and an average diameter of the through holes of 0.8 to 1.2 mm.

[0038] The plasma actuator is preferably provided on the upstream side of the flow path. By positioning the plasma actuator upstream of the flow path, the induced flow can be directly applied to the surface of the fin, thinning the thermal boundary layer near the surface of the fin and improving the cooling effect.

[0039] If the diameter of the through holes in the fin is larger on the downstream side than on the upstream side, the movement of airflow to adjacent flow paths on the upstream side is suppressed, reducing the deceleration of the airflow on the downstream side, and allowing airflow to move back and forth between adjacent flow paths even on the downstream side where the flow velocity is slower, thereby maintaining cooling performance all the way to the downstream area.

[0040] Furthermore, if the fins are straight fins, pressure loss is reduced, the deceleration of the main airflow downstream is reduced, and the airflow can move between adjacent flow paths without significantly opposing the flow of the main airflow, thereby improving cooling performance.

[0041] The cooling device of the present invention can have a fan that directs the main airflow through the flow path. By providing a fan, the flow rate of the airflow can be increased, and the control of the induced flow by the plasma actuator can be effectively controlled so that the airflow moves back and forth between adjacent flow paths, thereby improving cooling performance.

[0042] The fan may be either a push type provided on the upstream side of the flow path or a pull type provided on the downstream side.

[0043] In the case of a push-type fan, if the fins on both ends of the heat sink in the direction of arrangement of the flow paths are formed of flat plates without through holes, it is possible to prevent the main airflow from escaping outside the heat sink.

[0044] In addition, in the case of a pull-type fan, the fins at both ends of the flow path have through holes, so that unheated airflow that is the same as the inlet can be introduced from outside the heat sink not only through the inlet upstream of the flow path, but also through the through holes in the fins at both ends of the flow path. [Example]

[0045] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0046] A heater was attached to the base plate of a heat sink with a plasma actuator at the upstream end of the flow path, and the heat sink was heated while a main airflow with a velocity of 1.4 m / s at the flow path inlet was passed from the upstream side of the heat sink. The thermal resistance was measured by changing the fin, the driving method of the plasma actuator, and the number of flow paths with plasma actuators. The measurement results are shown in Table 1. When plasma actuators were provided in all flow paths, a difference was made in the output of the plasma actuators between adjacent flow paths.

[0047] [Table 1]

[0048] The cooling device with fins made of lotus-type porous copper has a cooling performance multiplier of 1.25, which is better than the 1.1 of the cooling device with fins made of flat copper plates. This shows that by forming the fins from lotus-type porous metal material, the surface area of ​​the fins is increased, thereby improving cooling performance.

[0049] Furthermore, for a cooling device with fins formed from lotus-type porous copper, cooling performance is improved when the plasma actuators are driven in bursts on all channels rather than continuously on all channels, and when every other channel is burst driven rather than continuously driven on every other channel. This shows that the airflow passing through the through holes in the fins increases, improving cooling performance, and that the number of plasma actuators can be reduced, thereby reducing power consumption by the plasma actuators. [Explanation of symbols]

[0050] 1. Airflow generating device (plasma actuator) 11 Exposed electrode 12 Coated electrode 13 Dielectrics 14 AC power supply 15 Induced flow 2 heat sinks 21 Finn 22 Through hole 23 Base Plate 24 flow paths 3 Temperature boundary layer 4 Main airflow 5 Heating element

Claims

1. a heat sink having fins standing on a base plate and a plurality of flow paths formed between the fins; an airflow generating device that causes an airflow to flow in the flow path, the fins forming the plurality of flow paths include fins having a plurality of through holes connecting adjacent flow paths, A cooling apparatus characterized in that the airflow generating device generates airflows whose flow velocities differ at least between adjacent flow paths.

2. 2. The cooling system according to claim 1, wherein the airflow generating device is a plasma actuator.

3. 3. The cooling device according to claim 2, wherein the plasma actuator is provided upstream of the flow path.

4. 3. The cooling device according to claim 2, wherein the plasma actuator is provided in one of the adjacent flow paths.

5. The plasma actuator performs burst driving, 3. The cooling device according to claim 2, wherein adjacent plasma actuators have different drive timings.

6. 2. The cooling device according to claim 1, wherein the fins are formed of a lotus-type porous metal.

7. 2. The cooling device according to claim 1, wherein the diameter of the through holes in the fins is larger on the downstream side than on the upstream side.

8. 2. The cooling device according to claim 1, wherein the fins are straight fins.

9. 2. The cooling device according to claim 1, further comprising a fan for directing a main airflow through said flow path.

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