Pulsating heat pipe heat sink

Abstract

The invention relates to a pulsating heat pipe heat sink (10; 10a to 10h) comprising: within a housing (20), at least one meandering channel (24; 24a; 24b; 75, 76) for a cooling medium, wherein the cooling medium serves to cool a component (1) located in an evaporator region (12), wherein the at least one channel (24; 24a; 24b; 75, 76) has a plurality of first channel portions (44; 44b; 44c; 44e to 44h; 46; 46b) arranged parallel to one another, and arcuate second channel portions (48; 48e; 50) or return portions (56; 61 to 66) which connect the first channel portions (44; 44b; 44c; 44e to 44h; 46; 46b).

Description

[0001] R.404738

[0002] - 1 -

[0003] Description

[0004] Pulsating Heat Pipe Heatsink

[0005] Technical field

[0006] The invention relates to a pulsating heat pipe heat sink for cooling heat-generating components, in particular electronic components in a control unit, which is characterized by particularly good cooling properties or a particularly good response behavior.

[0007] State of the art

[0008] Conventional pulsating heat pipe heat sinks are characterized by having at least one channel for an evaporating cooling medium, which features a multitude of parallel first channel sections connected to arc-shaped second channel sections to create a meandering form. Crucially, the symmetrical arrangement and design of the first channel sections relative to the heat input point ("hot spot") means that, at least initially, there is no preferred direction for the evaporating cooling medium. This results in a delayed response and, if this persists during operation, suboptimal cooling performance.

[0009] Disclosure of the invention

[0010] The pulsating heat pipe heat sink according to the invention, with the features of claim 1, has the advantage that a preferred flow direction of the cooling medium is formed in the at least one channel, which thereby enables particularly effective cooling of at least one component to be cooled, and in particular also an accelerated response time at the start of operation. R.404738

[0011] - 2 -

[0012] The invention is based on the idea of ​​achieving different lengths of the first channel sections relative to the heat input point ("hot spot") by breaking the symmetry of the arrangement of the first channel sections. This results in different pressure conditions in the two theoretically possible flow directions for the evaporating cooling medium. Due to these different pressure conditions, a preferred flow direction of the medium in the cooling element is created. The possibility of these different pressure conditions in the flow of the medium arises because the ratio of vapor phase to fluid of the medium is not uniform or fixed along the entire length of the at least one channel. More vapor is produced in the evaporator area ("hot spot"), and its proportion increases. In the condenser area, the vapor condenses, and the proportion of the liquid phase (fluid) increases.However, steam and fluid have different flow resistances due to their different densities and internal friction. Furthermore, the coefficient of friction is also temperature-dependent; that is, a colder fluid has a higher viscosity and therefore a higher flow resistance. Consequently, the pressure drop for the medium with higher flow resistance is greater for long channels, while it is lower for shorter distances. Therefore, the energetically more favorable state for this medium is to flow over the shortest possible distances between zones of higher concentration and zones of lower concentration. This means that the different lengths of the initial channel sections, or the symmetry breaking, result in additional or different flow paths for the medium, which amplifies this effect. This leads to particular problems at startup or...At the start of operation, this results in a preferred flow direction of the cooling medium despite small pressure differences.

[0013] In light of the above explanations, a pulsating heat pipe heat sink according to the invention therefore has at least one meandering channel for a cooling medium arranged within a housing to create asymmetrical flow conditions. The cooling medium serves to cool a component arranged in an evaporator area, wherein the at least one channel R.404738

[0014] - 3 - comprising several first channel sections arranged parallel to each other and arc-shaped second channel sections or return sections connecting the first channel sections. Furthermore, a first straight line running perpendicular to the first channel sections in the plane of the at least one channel and a second straight line running parallel to the first channel sections are present. It is essential that the at least one channel is designed or arranged at least asymmetrically with respect to the second straight line.

[0015] Advantageous further developments of the heat pipe cooling body according to the invention are listed in the dependent claims.

[0016] With regard to the generally described inventive concept, there are different constructive or geometric arrangements and designs of the at least one channel for guiding the cooling medium, which are described below:

[0017] A first preferred embodiment provides that the two straight lines intersect at a point of intersection that is located centrally in the evaporator area.

[0018] It may also be provided that the first canal sections have different lengths, and that additional canal sections, in particular meandering ones, are arranged laterally next to shortened first canal sections.

[0019] Further developing the last proposal, it may be provided that the additional channel sections are arranged at least essentially in a capacitor area of ​​the channel.

[0020] Another embodiment of the heat sink provides for two first channel sections, spaced apart from each other by at least one first channel section. The two aforementioned first channel sections are connected to each other by a return section running perpendicular to the first channel sections. R.404738

[0021] - 4 -

[0022] A further development of the most recent proposal envisages that several return sections are provided, between which a different number of initial channel sections are arranged.

[0023] In principle, it is also possible that at least one channel is connected to a supply channel for the cooling medium, and that at least one channel is designed as a self-contained closed channel.

[0024] Alternatively, it can be provided that the at least one channel is connected to a supply channel for the cooling medium, and that the at least one channel is designed as a channel closed at its ends.

[0025] It can also be advantageous to provide two separate channels that are fluidically isolated from each other. This allows, for example, the use of different cooling media and / or different channel geometries to influence the evaporation and flow behavior of the cooling medium.

[0026] However, in the latter proposal, it is also possible that the two channels have an identical geometry and are arranged parallel to each other in a direction running in the direction of the first straight line.

[0027] 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.

[0028] Brief description of the drawings

[0029] Fig. 1 shows a section through a first embodiment of a heat exchanger for cooling components,

[0030] Fig. 2 shows a cross-section in the plane 11-11 of Fig. 1 and

[0031] Fig. 3 to R.404738

[0032] - 5 -

[0033] Fig. 10 shows geometrically modified designs of a channel used to guide cooling medium in section, in comparison to Fig. 1.

[0034] Embodiments of the invention

[0035] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0036] The pulsating heat pipe heat sink 10 shown in Figures 1 and 2, hereinafter referred to simply as heat sink 10, serves to cool at least one electronic component 1, visible only in Figure 2, or a component that dissipates heat during operation. The component 1 can be, for example, a power IC or similar. The component 1 is thermally connected to the heat sink 10 at an evaporator area 12 of the heat sink 10 in a manner known per se and therefore not shown. The thermally conductive connection can be made, for example, via a thermally conductive adhesive or by direct mechanical connection to the heat sink 10. The centrally arranged evaporator area 12 is characterized in the figures by an exemplary rectangular or square boundary 13.

[0037] A cooling medium (not shown) in the form of a vaporizable liquid is arranged within the heat sink 10. The cooling medium, which is vaporized by the heat of the component 1 to be cooled, flows within the heat sink 10 from the evaporator section 12 towards a condenser section 14. There, the cooling medium is cooled to its condensation temperature by transferring heat to a colder heat sink or by other means, for example, by cooling fins or similar elements connected to the heat sink 10. It then flows back towards the evaporator section 12. The area in which the cooling of the cooling medium takes place is marked in the figures by the frame-like boundary 15. The operating principle of a heat sink 10 described so far is known from the prior art and is therefore not explained in further detail.

[0038] The heat sink 10 consists, purely by way of example, of two components 16, 18, which are at least partially connected to each other, such that the R.404738

[0039] - 6 -

[0040] The cooling medium contained in the cooling element 10 cannot escape from the cooling element 10. The two components 16 and 18 form a housing 20 for the cooling element 10. A channel 24 for the cooling medium is formed in the first component 16. The channel 24 can be formed, for example, by a machining process in the first metal component 16, by primary forming, or in any other manner known from the prior art.

[0041] Channel 24 is closed by the second component 18, which forms a cover element 26. The heat sink 10 can be attached to a support component or similar (not shown) by means of four through-openings 28, which are exemplified in corner areas of the housing 20.

[0042] Channel 24 can be filled with the cooling medium via a supply channel 36 opening laterally on an outer surface of the first component 16. The supply channel 36 can be sealed tightly by means not shown to prevent the cooling medium from escaping the housing 20.

[0043] The supply channel 36 has a branch 38, which subdivides the channel 24 into two channel sections 40 and 42. Both channel sections 40 and 42 are meandering and closed off on the side opposite the branch 38 in the area of ​​end sections 37 and 39. The two channel sections 40 and 42 each have several parallel first channel sections 44 and 46, which are connected to each other by semicircular or arc-shaped second channel sections 48 and 50.

[0044] Furthermore, it can be seen from the illustration in Fig. 1 that both channel areas 40, 42 each have, by way of example, seven first channel sections 44, 46. Fig. 1 also shows a first straight line 51, which runs perpendicular to the first channel sections 44, 46. A second straight line 52 runs perpendicular to the first straight line 51 and parallel to the first channel sections 44, 46. In the illustration in Fig. 1, the intersection point 55 of the two straight lines 51, 52 lies at the intersection of the diagonals of the rectangular evaporator area 12.

[0045] Furthermore, it can be seen from Fig. 1 that the second channel sections 48 of the first R.404738 are arranged on the right in the plane of Fig. 1.

[0046] - 7 -

[0047] The first channel section 40 is offset to the right relative to the second channel section 50 of the second channel section 42. Conversely, the second channel section 50 of the second channel section 42, located on the left side of the plane of Fig. 1, is offset to the left relative to the second channel section 48 of the first channel section 40. This arrangement and configuration of the first channel sections 44, 46 and the second channel sections 48, 50 results in the channel 24, or rather the first channel sections 44, 46 of the channel 24, being asymmetrically arranged with respect to the second line 52, i.e., they cannot be reflected across the second line 52 without breaking symmetry. Furthermore, there is no symmetry with respect to the first line 51, nor is there point symmetry with respect to the intersection point 55 of lines 51 and 52.

[0048] The heat sink 10a shown in Fig. 3 differs from the heat sink 10 according to Fig. 1 essentially in that the channel 24a is designed as a self-contained channel 24a. For this purpose, the two end sections 37, 39, visible in Fig. 1 for the heat sink 10, are connected to each other by a return section 56 running perpendicular to the first channel sections 44, 46. The return section 56, which is typically arranged perpendicular to the first channel sections 44, 46 on the side facing away from the supply channel 36, laterally comprises four second channel sections 50. Otherwise, the geometry of the channel 24a corresponds to that of the channel 24, so that, in the case of the heat sink 10a, the channel 24a also exhibits no symmetry with respect to the lines 51 and 52, nor any point symmetry.

[0049] The heat sink 10b shown in Fig. 4 is characterized essentially by two additional short meandering sections 58, 59, which are arranged in the condenser section 14 on opposite sides and at different distances from the first straight line 51 and the second straight line 52. Furthermore, it can be seen that in the evaporator section 12, on one side of the second straight line 52, there are three first channel sections 44b, and on the other side of the second straight line 52, there are four first channel sections 46b. The closed channel 24b thus exhibits no symmetry with respect to the lines 51 and 52, nor any point symmetry. R.404738

[0050] - 8 -

[0051] The heat sink 10c shown in Fig. 5 has two return sections 61, 62, each extending laterally to a second channel section 50. The arrangement of the return sections 61, 62 in the heat sink 10c is chosen to minimize the distance to the first channel sections 44c and to minimize the length of the return sections 61, 62.

[0052] In contrast to the heat sink 10c, the heat sink 10d of Fig. 6 has several return sections 63 to 66 of different lengths, which are nested inside each other.

[0053] The heat sink 10e shown in Fig. 7 is characterized by having first channel sections 44e of different lengths Li to L3. Two first channel sections 44e arranged directly next to each other are connected to each other by means of a second channel section 48e. In the evaporator area 12, two second channel sections 48e can also be seen directly opposite each other, with a gap 68 between them. Although the arrangement of shortened first channel sections 44e can, in principle, be at any position, the arrangement of gaps 68 between adjacent second channel sections 48e in the evaporator area 12 should be avoided, if possible, to prevent hot spots.

[0054] Figure 8 shows, using the heat sink 10f as an example, that five shortened first channel sections 44f form a free area laterally next to the supply channel 36, in the area of ​​which a further channel section 69, here in a meandering shape, is arranged. Crucially, in addition to the continued symmetry break with the second straight line 52, the further channel section 69 does not reduce or eliminate the preferred flow direction of the cooling medium caused or promoted by the symmetry break, and the preferred flow direction is further supported by the additional slight pressure drop in the channel section 69.

[0055] Figure 9 shows a heat sink 10g, which, similar to the heat sink 10f according to Figure 8, has shortened first channel sections 44g, next to which further identically designed channel sections 71, 72 are arranged laterally in the condenser area 14. However, here too an R.404738

[0056] - 9 -

[0057] There is a symmetry breaking with the second straight line 52, since the further canal section 71 has a greater distance to the second straight line 52 than the further canal section 72.

[0058] Finally, Fig. 10 shows a cooling element 10h with two separate, self-contained channels 75, 76, each connected on the same side to a supply channel 77, 78. The supply channels 77, 78 are connected laterally to the first channel sections 44h by meandering channel sections 80, 81. Here, too, there is no symmetry with respect to the second line 52, since although the two channels 75, 76 have exactly the same geometry or shape, they are arranged parallel to each other in the direction of the first line 51. In addition to the fact that the first channel sections 44h of each channel 75, 76 extend only over a portion of the evaporator area 12, the desired preferred flow direction of the cooling medium is created by the increased flow resistance of the additional channel sections 80, 81.

[0059] The heat sinks 10, 10a to 10h described so far can be modified or adapted in various ways without deviating from the inventive concept. This concept consists of achieving a preferred flow direction of the evaporating cooling medium by breaking the symmetry of the second straight line 52, which runs parallel to the first channel sections. Geometric elements of the individual heat sinks 10, 10a to 10h can also be combined with one another without deviating from the inventive concept. Furthermore, it is also possible to arrange the geometries shown and described asymmetrically or offset relative to a heat source and the heat sink in the condenser area 14.

Claims

R.404738 - 10 - Claims 1. Pulsating heat pipe heat sink (10; 10a to 10h), with at least one meandering channel (24; 24a; 24b; 75, 76) arranged within a housing (20) for a cooling medium, wherein the cooling medium serves to cool a component (1) arranged in an evaporator area (12), wherein the at least one channel (24; 24a; 24b; 75, 76) connects several parallel first channel sections (44; 44b; 44c; 44e to 44h; 46; 46b) and arc-shaped second channel sections (48; 48e; 50) or return sections (56; 61 to 66) connecting the first channel sections (44; 44b; 44c; 44e to 44h; 46; 46b). exhibits, and with a first straight line (51) running in the plane of the at least one channel (24; 24a; 24b; 75, 76) perpendicular to the first channel sections (44; 44b; 44c; 44e to 44h; 46; 46b) and a second straight line (52) running parallel to the first channel sections (44; 44b; 44c; 44e to 44h; 46; 46b), wherein the at least one channel (24; 24a; 24b;75, 76) is formed at least asymmetrically to the second line (52).; 2. Cooling element according to claim 1, characterized in that the two straight lines (51, 52) intersect at an intersection point (55) which is arranged centrally in the evaporator area (12).

3. Cooling element according to claim 1 or 2, characterized in that the first channel sections (44g; 46b) have different lengths, and that additional channel sections (58, 59; 71 , 72), in particular meandering, are arranged laterally next to shortened first channel sections (44g; 46b).

4. Heat sink according to claim 3, characterized in that R.404738 - 11 - that the additional channel sections (58, 59; 71 , 72) are arranged at least substantially in a capacitor area (14) of the channel (24b).

5. Cooling sink according to one of claims 1 to 4, characterized in that two first channel sections (44c; 46), which are spaced apart from each other by at least one first channel section (44c; 46), are connected to each other by a return section (56; 61 to 66) extending perpendicular to the first channel sections (44c; 46).

6. Cooling element according to claim 5 characterized in that several return sections (56; 61 to 66) are provided, between which a different number of first channel sections (44c; 46) are arranged.

7. Cooling element according to one of claims 1 to 6, characterized in that the at least one channel (24a; 24b; 75, 76) is connected to a supply channel (36; 77, 78) for the cooling medium, and that the at least one channel (24a; 24b; 75, 76) is designed as a self-contained channel (24a; 24b; 75, 76).

8. Cooling element according to one of claims 1 to 6, characterized in that it has at least one channel (44) connected to a supply channel (35) for the cooling medium, and that the at least one channel (44) is designed as a channel (44) closed at end sections (37, 39).

9. Cooling sink according to one of claims 1 to 8, characterized in that two separate channels (75, 76) are provided that are fluidically separated from each other.

10. Heat sink according to claim 9, R.404738 - 12 - characterized in that the two channels (75, 76) have an identical geometry and are arranged parallel in a direction extending in the direction of the first straight line (51).