Pulsating heat pipe heat sink

Abstract

The invention relates to a pulsating heat pipe heat sink (10; 10a) comprising: a housing (12) in which at least one channel (14) for an evaporable cooling medium is formed; an evaporator region (20) for arranging at least one heat-generating component or the like; and a condenser region (22) arranged at a distance from the evaporator region (20), wherein the at least one channel (14) has a channel longitudinal axis (30), with channel cross-sections (A) formed perpendicularly to the channel longitudinal axis (30), and with at least one channel section (31) arranged in the evaporator region (20) and / or in the condenser region (22), in the region of which channel section the channel cross-sections (A) vary as viewed in the direction of the channel longitudinal axis (30).

Description

[0001] R.411591

[0002] - 1 -

[0003] Description

[0004] title

[0005] Pulsating Heat Pipe Heatsink

[0006] Technical field

[0007] The invention relates to a pulsating heat pipe heat sink which is characterized by particularly good thermal behavior, especially during startup.

[0008] State of the art

[0009] Pulsating heat pipe heat sinks, often referred to simply as heat sinks, are known in the art in a wide variety of designs and geometries. They serve to cool a heat-generating component or assembly to ensure its functionality during operation. The heat-generating component or assembly is arranged in thermally conductive contact with a heat sink housing. Within the housing, a vaporizable cooling medium is arranged in a channel. This medium evaporates in an evaporator section, where the component is also located, and then flows into a condenser section, where it condenses again before flowing back to the evaporator section.

[0010] A pulsating heat pipe heat sink with the features of the preamble of claim 1 is known from CN 207124843 U. The heat sink known from the aforementioned document has channel sections whose cross-sections vary when viewed in the direction of the channel's longitudinal axes. Crucially, the cross-sections in the aforementioned channel section are symmetrical to the channel's longitudinal axis, i.e., when viewed circumferentially around the channel's longitudinal axis, they change uniformly with a round basic cross-section. R.411591

[0011] - 2 -

[0012] Another cooling element with the features of the preamble of claim 1 is known from EP 3 754281 B1. The cross-sectional changes of the channel therein are scale-like, with the channel having a round basic shape. It is also known from this document that an increased flow rate of the cooling medium can be achieved by changing the channel cross-sections.

[0013] Disclosure of the invention

[0014] The pulsating heat pipe heat sink according to the invention, with the features of claim 1, has the advantage that it provides alternative channel cross-sections to promote or direct the evaporable cooling medium in a preferred direction. Depending on the design of the heat sink, either with a closed or continuous channel, or with end sections closed at the ends of the channel, improved heat transfer into the cooling medium is also promoted, either alternatively or additionally.

[0015] In light of the above explanations, a pulsating heat pipe heat sink according to the invention, comprising the features of claim 1, therefore has a housing in which at least one channel for an evaporable cooling medium is formed. Furthermore, an evaporator section for arranging at least one heat-generating component or the like is provided, as well as a condenser section arranged at a distance from the evaporator section. The at least one channel has a longitudinal axis with channel cross-sections formed perpendicular to the longitudinal axis. Furthermore, in at least one channel section arranged in the evaporator section and / or in the condenser section, the channel cross-sections change in the direction of the longitudinal axis. It is essential to the invention that the channel cross-sections in the channel section are asymmetrical with respect to the longitudinal axis.

[0016] Advantageous embodiments of the pulsating heat pipe heat sink according to the invention are listed in the dependent claims. R.411591

[0017] - 3 -

[0018] Depending on the specific application or design of the heat sink, various geometries of the channel section with changing channel cross-sections are conceivable, falling under the basic concept of the invention. These are explained below:

[0019] In a first basic variant, the cross-section of the channel, at least in the channel section, can be essentially rectangular with two channel sidewalls, a channel base, and a channel roof, whereby the changing channel cross-sections are formed in the area of ​​a channel sidewall and / or in the area of ​​the channel base or in the area of ​​the channel roof. Such a design of the channel is particularly applicable to channels formed by machining processes and to multi-part housings, where the channel is closed by a cover element of the housing.

[0020] Alternatively, it is also conceivable that the cross-section of the channel, at least in the channel section, is essentially rectangular with two channel walls, a channel base, and a channel roof, whereby the changing channel cross-sections are formed in the area of ​​the two channel walls or in the area of ​​the channel base and the channel roof. In contrast to the last proposal, a change in geometry now occurs in both channel walls or in the channel base and the channel roof opposite the channel base. The effect of the changing channel cross-sections is therefore greater in the last case than in the first.

[0021] In yet another alternative embodiment of the channel cross-section, the channel section is at least substantially circular, with the changing channel cross-sections forming a circular segment of the channel. Such a channel embodiment is preferably used, for example, in a heat sink manufactured using an additive process.

[0022] Regardless of the three basic geometries of the cross-sectional areas of the channel in the channel section mentioned above, it is specifically intended that the channel section, viewed in the direction of the channel's longitudinal axis, has an R.411591

[0023] - 4 - comprises a first section and a second section preferably immediately adjoining the first section, and that the distance between the channel side wall or channel bottom or channel ceiling, viewed in the direction of the channel longitudinal axis, preferably increases linearly in the first section and decreases linearly in the second section, the two sections having different lengths viewed in the direction of the channel longitudinal axis. The geometry of the sections described so far causes different pressure differences to be achieved in one or the other flow direction of the cooling medium, depending on the flow direction, thus favoring the aforementioned preferred flow direction of the cooling medium.

[0024] Further developing the last proposal, it may also be provided that a third section without a change in cross-section is arranged before the first section or after the second section or between the first and the second section.

[0025] It is also possible to provide for several periodically repeating first, second, and, if necessary, third sections within the channel. In other words, this means that the geometry of the changing channel cross-sections repeats periodically to promote or enhance the effect of the preferred flow direction of the cooling medium.

[0026] In an alternative embodiment, it may also be provided that, in the case of channel cross-sections changing on opposite channel side walls or on the channel base and on the channel ceiling, the geometries formed on the opposite channel side walls or on the channel base and on the channel ceiling are arranged with an offset to each other in the longitudinal axis of the channel, or that the geometries are formed differently.

[0027] A reduction in flow resistance for the cooling medium can be achieved by rounding the transition areas between the individual sections in the channel section. R.411591

[0028] - 5 -

[0029] The flow characteristics of the cooling medium can be further influenced by incorporating additional additive or subtractive structural elements in the first, second, and / or third sections of the channel. These are structural elements that do not necessarily arise from the normal manufacturing process of the channel, for example, in the form of roughness, but rather from additional processing steps, such as laser beam processing or targeted material deposition using additive manufacturing.

[0030] As mentioned above, there are also two fundamentally different types of channel construction: In the first variant, at least one channel is designed as a closed or endless channel. Alternatively, it is also conceivable that at least one channel is designed as a channel closed at opposite ends.

[0031] A meandering design of the at least one channel is preferred, in which the at least one channel has several parallel, straight first channel sections and arcuate second channel sections or return sections connecting the first channel sections, and in that only some of the first channel sections are provided with the channel sections in the evaporator section and / or in the condenser section.

[0032] Alternatively, all channel areas in the evaporator area and / or in the condenser area can also be designed with the channel sections.

[0033] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments of the invention and from the drawings.

[0034] Brief description of the drawings

[0035] Fig. 1 and R.411591

[0036] - 6 -

[0037] Fig. 2 shows sections through differently designed pulsating heat pipe heat sinks.

[0038] Fig. 3 and

[0039] Fig. 4 shows channel sections with changing channel cross-sections,

[0040] Fig. 5 shows an enlargement of a channel section with a changing geometry in longitudinal section.

[0041] Figs. 6 and 7 each show longitudinal sections through further channel sections with changing channel cross-sections and

[0042] Fig. 8 shows a section of the canal in which additional structural elements are formed in the area of ​​the canal wall.

[0043] Embodiments of the invention

[0044] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0045] The pulsating heat pipe heat sink 10 shown in Fig. 1, hereinafter referred to simply as heat sink 10, serves to cool at least one heat-generating component or a corresponding assembly not shown in the figures. The at least one component can be, for example, a power IC or similar component, but this is not a limitation.

[0046] The cuboid-shaped heat sink 10 with a rectangular base in the exemplary embodiment has a housing 12, which is preferably multi-part, comprising a housing base element and a housing cover. Alternatively, it is also conceivable to manufacture the housing 12 using an additive manufacturing process. In any case, however, the housing 12 consists of R.411591

[0047] - 7 - made of a material with good thermal conductivity, such as steel or aluminum or corresponding alloys.

[0048] Inside the housing 12, an endless channel 14 is formed for a vaporizable cooling medium (not shown) in the exemplary embodiment. The channel 14 can be filled with the cooling medium via a supply channel 16, which opens laterally onto the housing 12 and can be sealed in a medium-tight manner (not shown).

[0049] The housing 12 or the heat sink 10 has an evaporator area 20, which in the exemplary embodiment is square and defined by a boundary 19, and a rectangular condenser area 22, defined by a boundary 21, on the right-hand side in the plane of Fig. 1. In the condenser area 22, the heat sink 10 can, for example, be provided with cooling fins or similar measures to enhance the cooling effect.

[0050] At least one heat-generating component is thermally connected to the housing 12 in the evaporator section 20. During operation, this component heats the cooling medium located in the channel 14 in the evaporator section 20 above its boiling point, causing evaporation or vapor bubble formation of the cooling medium. Due to pressure differences in the channel 14, the cooling medium flows into the condenser section 22, where it is cooled to a temperature below its condensation temperature before flowing back into the evaporator section 20.

[0051] In the illustrated embodiment, at least one channel 14 is meandering and has first channel sections 24 arranged parallel to each other, which are connected on opposite sides by an arc-shaped second channel section 25. The two outermost first channel sections 24 are connected to each other via a return section 26, into which the supply channel 16 also opens via a branch 28. R.411591

[0052] - 8 -

[0053] With the exception of the two outermost first channel sections 24, which are connected to the return section 26, all first channel sections 24, or at least those operatively connected to the evaporator section 20 and the condenser section 22, are configured in the region of channel sections 31 with channel cross-sections A that change in the direction of a longitudinal channel axis 30 (which are oriented perpendicular to the longitudinal channel axis 30) and are only shown in Figures 3 and 4. In the embodiment shown in Figure 1, the geometry of the changing channel cross-sections A is identical in each direction of the channel 14, so that a preferred flow direction of the cooling medium is established according to arrows 32.

[0054] The cooling element 10a shown in Fig. 2 differs from the cooling element 10 essentially in that the channel cross-sectional areas A vary in the first channel sections 24a. Furthermore, the first channel sections 24a do not have continuously varying channel cross-sectional areas A; rather, the area between the evaporator section 20 and the condenser section 22 is partially free of varying channel cross-sectional areas A. However, a preferred flow direction of the cooling medium is achieved here as well, as indicated by arrows 23.

[0055] It should also be noted that, for example with reference to Fig. 1, in the case of the heat sink 10, depending on the arrangement of the geometries of successive channel cross-sections A of the first channel regions 24, i.e., whether the geometries of the first channel regions 24 are repeated or designed in opposite directions, a preferred or no preferred flow direction of the cooling medium is established. In the latter case, only improved heat transfer to / from the cooling medium takes place in the evaporator region 20 or in the condenser region 22.

[0056] Figures 3 and 4 show different modifications of the channel cross-sections A in the direction of the channel longitudinal axis 30 in the first channel sections 24, 24a in the channel segments 31. It is essential that the basic shape or cross-section of the channel 14 is formed either by the channel 14 having, as shown in Figure 1, two opposing channel side walls 34, 36, and a channel base 38.

[0057] - 9 - and has a channel roof running parallel to the channel base 38 and to the plane of Fig. 1, and therefore not visible. In other words, this means that the basic cross-section of the channel 14 is rectangular or square. Alternatively, the basic cross-section of the channel 14 can also be circular.

[0058] The channel cross-section according to Fig. 3 (cf. Fig. 5) is characterized by the fact that it is only formed with geometric changes in the area of ​​one of the channel side walls 34, 36 or in the area of ​​the channel base 38 or the channel roof. These changes comprise two sections 41, 42 that are directly adjacent to one another in the direction of the channel's longitudinal axis 30 and repeat regularly or periodically. As can best be seen from Fig. 5, the first section 41, which is straight in cross-section, has a length h that is greater than the length l2 of the second section 42. This results in different inclinations of the corresponding channel side wall 34, 36 or the channel base 38, and thus of the changing channel cross-section A, which lead to different pressure increases in one of the two directions of the channel's longitudinal axis 30. The period length P of the two sections 41, 42 is h + l2.It is also mentioned that the transitions between sections 41 and 42 may be provided with rounding 40 (Fig. 3).

[0059] Starting from a straight line 44 running parallel to the longitudinal axis 30 of the channel, an amplitude a of the two sections 41, 42 is obtained. The width w of the channel cross-section A denotes the mean diameter of the channel cross-section A. It is essential that the amplitude a is between 0.05 and 10 times the width w. The period length P of the two sections 41, 42 can be between 0.1 times the channel width w and 0.25 times the total length of the channel 14.

[0060] The channel cross-section shown in Fig. 4 is characterized by the fact that, viewed on both sides of the channel's longitudinal axis 30, first sections 41 and second sections 42 are arranged, but these are offset from each other by a factor b in the direction of the channel's longitudinal axis 30. R.411591

[0061] - 10 -

[0062] The channel cross-sections A described so far according to Figs. 3 to 5 are all characterized by the fact that the change in the channel cross-sections A in the direction of the channel longitudinal axis 30 is asymmetrical to the channel longitudinal axis 30.

[0063] Figure 6 shows another channel section 31. This is similar to the channel section 31 according to Figure 3 with the two sections 41, 42, however, a third section 46 follows the second section 42, in which the cross-section of the channel section 31 is constant.

[0064] Fig. 7 shows a channel section 31, which is composed of a total of four sections 51 to 54, each of which has different inclinations or tilts in relation to the longitudinal axis 30 of the channel.

[0065] Figure 8 shows that a channel section 31, comprising the two sections 41 and 42, has additional structural elements 60 in the form of recesses in the area of ​​the channel walls. These can be produced, for example, by means of a laser cutting device or similar, but in any case by a separate manufacturing step. The structural elements 60 can support the formation of the vapor phase of the cooling medium and also promote the development of a preferred flow direction of the cooling medium.

[0066] It is also mentioned that the structural elements 60 can be produced not only by a subtractive manufacturing process, but also, for example, by additive manufacturing or by protrusions on the channel walls.

[0067] Finally, it is mentioned that instead of a self-contained channel 14, it may also be provided that the channel 14 - as is known from the prior art - can be designed as a closed channel 14 at opposite end regions.

[0068] The heat sink 10, 10a described so far, or the channel cross-sections A described so far, and their arrangement and orientation in the heat sink 10, 10a, can be modified or adapted in a variety of ways without deviating from the inventive concept. This is particularly relevant with regard to R.411591

[0069] - 11 - on Fig. 4, it is conceivable that instead of an offset b, the geometries on the two opposite sides of the longitudinal channel axis 30 could be designed fundamentally differently, so that they are asymmetrical to the longitudinal channel axis 30.

Claims

R.411591 - 12 - Claims 1. Pulsating Heat Pipe cooling element (10; 10a), comprising a housing (12) in which at least one channel (14) for an evaporable cooling medium is formed, comprising an evaporator area (20) for arranging at least one heat-generating component or the like, comprising a condenser area (22) arranged at a distance from the evaporator area (20), wherein the at least one channel (14) has a longitudinal channel axis (30), with channel cross-sections (A) formed perpendicular to the longitudinal channel axis (30), and comprising at least one channel section (31) arranged in the evaporator area (20) and / or in the condenser area (22), in the area of ​​which the channel cross-sections (A) change in the direction of the longitudinal channel axis (30), characterized in that the channel cross-sections (A) in the channel section (31) are formed asymmetrically to the longitudinal channel axis (30).

2. Cooling element according to claim 1, characterized in that the cross-section of the channel (14) is formed at least substantially rectangularly in the channel section (31) with two channel side walls (34, 36), a channel base (38) and a channel ceiling, and that the changing channel cross-sections (A) are formed in the area of ​​a single channel side wall (34, 36) and / or in the area of ​​the channel base (38) or in the area of ​​the channel ceiling.

3. Cooling element according to claim 1, characterized in that the cross-section of the channel (14) is at least substantially rectangular in the channel section (31) with two channel side walls (34, R.411591 - 13 - 36), a channel base (38) and a channel ceiling, and that the changing channel cross-sections (A) are formed in the area of ​​the two channel side walls (34, 36) or in the area of ​​the channel base (38) and the channel ceiling.

4. Cooling element according to claim 1, characterized in that the cross-section of the channel (14) is at least substantially round in the channel section (31), and that the changing channel cross-sections (A) are formed in the area of ​​a circular segment of the cross-section of the channel (14).

5. Cooling sink according to one of claims 2 to 4, characterized in that the channel section (31) has a first section (41) and a second section (42) preferably directly adjoining the first section (41) when viewed in the direction of the channel longitudinal axis (30), and the channel cross-section (A) preferably increases linearly in the first section (41) and preferably decreases linearly in the second section (42) when viewed in the direction of the channel longitudinal axis (30), wherein the two sections (41, 42) have different lengths (h, l2) when viewed in the direction of the channel longitudinal axis (30).

6. Cooling element according to claim 5, characterized in that a third section (46) is arranged before the first section (41) or after the second section (42) or between the first and the second section (41 , 42) without changing the channel cross-section (A).

7. Cooling element according to claim 5 or 6, characterized in that several periodically repeating first and second and optionally third sections (41 , 42, 46) are formed in the channel section (31).

8. Heat sink according to one of claims 5 to 7, characterized in that, R.411591 - 14 - that, in the case of channel cross-sections (A) changing on opposite channel side walls (34, 36) or on the channel bottom (38) and on the channel ceiling, the geometries formed on the opposite channel side walls (34, 36) or on the channel bottom (38) and on the channel ceiling are arranged with an offset (b) in the longitudinal axis (30) of the channel, or that the geometries are formed differently.

9. Cooling sink according to one of claims 5 to 8, characterized in that transition areas between the sections (41, 42) are formed with radii (40).

10. Heat sink according to one of claims 5 to 9, characterized in that additional additive or subtractive structural elements (60) are formed in the area of ​​the first sections (41) and / or the second sections (42) and / or the third sections (46).

11. Cooling sink according to one of claims 1 to 10, characterized in that the at least one channel (14) is designed as a closed or endless channel (14).

12. Heat sink according to one of claims 1 to 10, characterized in that the at least one channel (14) is designed as a channel (14) closed at opposite end sections.

13. Cooling sink according to one of claims 1 to 12, characterized in that the at least one channel (14) has several parallel, straight first channel sections (24a) and arcuate second channel sections (25) or return sections (26) connecting the first channel sections (24a), and that in the evaporator section (20) and / or in the condenser section (22) only some of the first channel sections (24a) are provided with the channel sections (31). R.411591 - 15 - 14. Cooling sink according to one of claims 1 to 12, characterized in that the at least one channel (14) has several parallel, straight first channel sections (24) and arcuate second channel sections (25) or return sections (26) connecting the first channel sections (24), and that in the evaporator section (20) and / or in the condenser section (22) all first channel sections (24) are provided with the channel sections (31).

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