Pulsating heat pipe heat sink

Abstract

The invention relates to a pulsating heat pipe heat sink (10; 10a to 10e) comprising: a housing (12) in which at least one meandering channel (14) for conveying an evaporable cooling medium is disposed; an evaporator region (20; 20b; 20c) which can be thermoconductively connected, at least indirectly, to a heat-generating component; and a condenser region (30) for condensing the cooling medium; wherein the at least one channel (14) has a plurality of first channel portions (35; 35a; 35c; 35d; 35e, 38; 38a; 38b; 38c) which are arranged parallel to one another and are connected to one another by arcuate second channel portions (36) or by return portions (44).

Description

[0001] R.409178

[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 cooling behavior with regard to a preferred flow direction of a cooling medium in a channel, especially also in the start-up case of the heat sink.

[0008] State of the art

[0009] Pulsating heat pipe heat sinks, hereinafter referred to simply as heat sinks, are known in various forms from the prior art. They serve to cool at least one heat-generating component that is thermally connected to the heat sink in an evaporator section of the heat sink housing. For this purpose, at least one externally sealed channel for a vaporizable cooling medium is formed in the heat sink housing. Under the influence of the heat generated by the component, the cooling medium evaporates, forming vapor bubbles, and enters a condenser section of the housing, where it is cooled to a temperature below its condensation temperature. This allows the condensed cooling medium to flow back towards the evaporator section and evaporate again.The known pulsating heat pipe heat sinks typically feature a multitude of parallel first channel sections, which are connected to each other by means of arc-shaped second channel sections or a return section. This results in an overall meandering channel shape. The first channel sections also typically contain R.409178 both within and outside the evaporator area.

[0010] - 2 - always the same length, which may only be reduced due to, for example, the aforementioned return channel.

[0011] Disclosure of the invention

[0012] The pulsating heat pipe heat sink according to the invention, with the features of claim 1, has the advantage that, due to the special geometric design of the first channel sections in the evaporator area, it promotes a defined flow direction of the cooling medium, particularly during startup. This enables a particularly good response time and / or rapid cooling of the components to be cooled.

[0013] The invention is based on the idea of ​​promoting a specific flow direction of the cooling medium by extending the first channel sections that traverse the evaporator area, thereby achieving a locally stronger cooling of the cooling medium. The extension of these inner first channel sections according to the invention particularly reduces hot spots in the evaporator area, which can occur when there is no preferred flow direction of the cooling medium. In such cases, flow reversals of the cooling medium often occur. In other words, the geometric design of the inner first channel sections reduces the probability of a flow reversal of the cooling medium.

[0014] In light of the above explanations, a pulsating heat pipe heat sink according to the invention, having the features of claim 1, therefore comprises a housing in which at least one meandering channel for an evaporable cooling medium is arranged. The heat sink has an evaporator section which can be connected, at least indirectly, to a heat-generating component via thermal conductivity. Furthermore, a condenser section for condensing the cooling medium is provided at a distance from the evaporator section, wherein the at least one channel has several first channel sections arranged parallel to one another. The first channel sections are connected to each other with arcuate second channel sections or with a return section, wherein inner first channel sections are provided which traverse the evaporator section and terminate outside the evaporator section in R.409178.

[0015] - 3 -

[0016] protrude towards the condenser area. Furthermore, outer first channel sections are provided that run outside the evaporator area, wherein at least some of the inner first channel sections, which are connected to each other by means of the second channel sections, are extended compared to the outer first channel sections, which are connected to each other by second channel sections.

[0017] According to the invention, the length of a first channel section is understood to be the length extending in the direction of the longitudinal axis of the first channel section between the second channel sections arranged on both sides of the first channel section.

[0018] Advantageous further developments of the Pulsating Heat Pipe cooling body according to the invention are listed in the dependent claims.

[0019] Based on the basic geometry of the channel described above, with inner and outer first channel sections of varying lengths, the inventive concept makes it possible to realize a wide variety of channel geometries depending on the application, which, with regard to the respective application, enable targeted control of the temperature profile or the heat dissipation of a component.

[0020] In a first advantageous embodiment, the length of the inner first channel sections in the evaporator area increases in a direction perpendicular to the first channel sections. This means that, for example, the length of the first channel sections always increases linearly by the same amount in this direction, or that, for example, two immediately adjacent first inner channel sections have the same length, followed, in the same direction, by an inner first channel section of greater length. Such a staggered length of the inner first channel sections enables varying degrees of cooling or heat dissipation from the component, depending on the flow direction of the cooling medium.This can be explained by the fact that this arrangement leads to a greater cooling of the cooling medium in the longer channel sections at the condenser, so that the cooling medium flowing back to the heat source R.409178.

[0021] - 4 - is cooler and the heat source can then cool down more significantly. This prevents a strong temperature gradient from developing in the heat source. On the other hand, even with channel sections of equal length, large temperature differences within them create a strong pressure gradient between the individual channel sections, acting against the current flow direction of the cooling medium. This pressure can cause a random reversal of the flow direction, which, at the moment of the changeover (flow velocity is briefly very low or zero), leads to a short-term, undesirable temperature increase in the heat source.

[0022] Alternatively, it is also conceivable that the length of the inner first channel sections in the evaporator area, in a direction perpendicular to the first channel sections, has a maximum in a central section of the evaporator area and decreases towards the outer regions of the evaporator area. Such a geometric design of the first channel sections results in identical temperature distributions in the evaporator area in both possible flow directions of the cooling medium, and thus identical cooling effects are achieved regardless of the flow direction of the cooling medium.

[0023] It is also possible, regardless of the geometric design of the inner first channel sections, that the length of the outer first channel sections differs at least on one side of the evaporator area.

[0024] Further developing the last proposal, it is specifically intended that the length of the outer first channel sections decreases in a direction away from the evaporator area.

[0025] As an alternative to different lengths of the outer first channel sections, it may also be useful for the length of the outer first channel sections to be the same, except in the area of ​​a return section.

[0026] Furthermore, the cooling characteristics of the heat sink can be influenced by the position of the evaporator area relative to the at least one channel or the housing of the heat sink. In a first variant, it is provided that the evaporator area and the at least one channel R.409178

[0027] - 5 - are arranged at least substantially centrally to the housing. Alternatively, it may also be provided that the at least one channel is arranged centrally to the housing and the evaporator area is arranged laterally offset from the center.

[0028] To achieve the greatest possible extension of the inner first channel sections within a given installation space or housing size, the second channel sections of the inner first channel sections can also be designed, at least partially, as loops or meanders. These loops or meanders thus represent the extensions of the inner first channel sections.

[0029] With a view to achieving the most compact design or arrangement of the first channel sections, it is planned that only a single feedback section is provided, which connects the two outermost first channel sections in the capacitor area.

[0030] The invention described so far will be further described below using a channel arranged in a plane as an example. However, the invention can, in principle, also be applied to channels or channel sections arranged in three dimensions without deviating from the inventive concept.

[0031] 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.

[0032] Brief description of the drawings

[0033] Figures 1 to 6 show simplified sectional views of differently designed channels in a pulsating heat pipe heat sink for cooling at least one heat-generating component. R.409178

[0034] - 6 -

[0035] Embodiments of the invention

[0036] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0037] 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 assembly not shown in the figures, for example, a power IC or similar part. The heat sink 10 has a housing 12, which is typically formed or assembled from at least two components. At least one channel 14 is formed within the housing 12 for guiding a vaporizable cooling medium, which is also not shown. Through holes 16 formed in the corner regions of the housing 12 serve to attach the housing 12 to a support assembly, which is not shown.

[0038] In the illustrated embodiment, the housing 12 is cuboid in shape with a rectangular base and a height perpendicular to the plane of Fig. 1. The channel 14 formed inside the housing 12 can be filled with the cooling medium via a supply channel 18 opening laterally into the housing 12. Furthermore, the supply channel 18 is sealed tightly (not shown) to prevent the cooling medium from escaping the housing 12.

[0039] The housing 12 or the heat sink 10 has an evaporator area 20, which in the exemplary embodiment is square and is bounded by an outer border 22. In the evaporator area 20, the aforementioned at least one heat-generating component or assembly is thermally connected to the upper or lower surface of the housing 12 in a plane parallel to the plane of Fig. 1. The connection can be made, for example, by a thermally conductive adhesive or by a mechanical fastening in a manner known per se.

[0040] The evaporator area 20 is surrounded by a frame-shaped intermediate area 26, which is in turn surrounded by a condenser area 30, which is in turn surrounded by a condenser area 30, which is bounded by a rim 28. R.409178

[0041] - 7 - is. The evaporator section 20 is characterized by the fact that, during operation of the at least one heat-generating component, the cooling medium evaporates by exceeding its boiling point, forming vapor bubbles, or the existing small bubbles grow due to evaporation of the cooling medium on the inner bubble surface and are transported towards the condenser section 30 as a result of pressure differences in the channel 14. The condenser section 30 is characterized by the fact that the cooling medium cools to a temperature that corresponds at most to the condensation temperature of the cooling medium, and the bubble size in the condenser section 30 shrinks due to condensation of the vapor phase on the inner bubble surface. Subsequently, the cooling medium with the smaller bubbles flows back into the evaporator section 20.The intermediate zone 26 is characterized by the presence of mixed forms of liquid and gaseous components of the cooling medium, and due to the adiabatic conditions, neither evaporation nor condensation of the cooling medium occurs.

[0042] Furthermore, it can be seen that the evaporator area 20 of the heat sink 10 has the same distance a, b to the opposite side edges 32, 34 of the housing 12, i.e., that the evaporator area 20 is arranged centrally to the housing 12. The intermediate area 26 and the condenser area 30 also have the same distances to the side edges 32, 34, but are rectangular in shape.

[0043] Channel 14 has, by way of example, seven inner first channel sections 35 traversing the evaporator section 20, each of which is straight and arranged parallel to one another. Immediately adjacent inner first channel sections 35 are connected to each other by means of arc-shaped or semicircular second channel sections 36. Outside the evaporator section 20, channel 14 has four outer first channel sections 38 on the upper side in the plane of Fig. 1 and three outer first channel sections 38 on the lower side in the plane of Fig. 1. The outer first channel sections 38 either traverse the intermediate section 26 and project into the condenser section 30, or they are arranged exclusively in the condenser section 20. Furthermore, it can be seen that the two opposing outer first channel sections 35 are arranged in a manner that...

[0044] - 8 -

[0045] Channel sections 38 are interconnected by means of a return section 40, which is connected to the supply channel 18 via a branch 42. The other outer first channel sections 38, arranged directly adjacent to each other, are connected to each other by arc-shaped or semicircular second channel sections 44. The second channel sections 44 can also be partially omitted if the channel 14 is configured in a so-called "open loop" variant.

[0046] The design and arrangement of the first channel sections 35 and 38, as well as the second channel sections 36 and 44 and the return section 40, as described so far, forms a meandering channel 14 for the cooling medium.

[0047] In addition, Fig. 1 shows a first straight line 45, which runs perpendicular to the first channel sections 35 and 38. A second straight line 46, on the other hand, runs parallel to the first channel sections 35 and 38. An intersection point 48 of the two lines 45 and 46 lies at the centroid or at the diagonal intersection of the evaporator area 20. Furthermore, it can be seen from Fig. 1 that the first channel sections 35 have different lengths L when viewed in the direction of the second straight line 46. In particular, it can be seen that the inner first channel sections 35, located near the intersection point 48 or in the center of the evaporator area 20, have the greatest length L, which decreases towards the outer first channel sections 38. It is also particularly evident that the inner first channel sections 35 extend at least substantially across the entire width of the heat sink 10 or up to the perimeter 28 of the condenser area 38.In contrast, the outer first channel sections 38 have a shorter length I than the inner first channel sections 35. However, the outer first channel sections 38 can also have different lengths I. In the illustrated embodiment, the length I of the outer first channel sections 38 decreases in a direction extending towards the side edges 32 of the housing 12.

[0048] The heat sink 10a shown in Fig. 2 differs from the heat sink 10 essentially in that the length L of the inner first R.409178

[0049] - 9 -

[0050] Channel sections 35a, viewed in the direction of the first straight line 45, increase steadily from one side of the evaporator area 20 to the other side of the evaporator area 20. Here too, the inner first channel sections 35a are longer than the outer first channel sections 38a.

[0051] The heat sink 10b shown in Fig. 3 has the same channel geometry as the heat sink 10a. However, the evaporator section 20b is not arranged centrally to the housing 12, but rather offset to the left and upwards in the plane of Fig. 3. Because the evaporator section 20b is not located in the center of the heat sink 10b, the heat sink 10b has more outer first channel sections 38b on its lower side (in the plane of the drawing) than on its upper side. Furthermore, the length of the outer first channel sections 38b at the bottom of Fig. 3 decreases in a direction away from the evaporator section 20b. This results in the overall system being cooler in the direction of arrow 50, and the occurrence of flow reversal of the cooling medium is less frequent.

[0052] In the cooling element 10c according to Fig. 4, the evaporator section 20c is also not centered, but slightly offset upwards in the plane of the drawing in Fig. 1. Furthermore, it can be seen that the upper inner first channel sections 35c are shorter than the lower inner first channel sections 35c. The upper inner first channel sections 35c are therefore even shorter than the outer first channel sections 38c. However, at least the lower inner first channel sections 35c are longer than the outer first channel sections 38c. As with the cooling element 10b according to Fig. 3, this results in the overall system being cooler in the direction of arrow 50, and the occurrence of flow reversal of the cooling medium is less frequent.

[0053] In the heat sink 10d shown in Fig. 5, the two inner first channel sections 35d arranged on either side of the intersection point 48 are designed with loop-shaped extensions 51 to 53 as second channel sections 36 in order to lengthen the inner first channel sections 35d for improved cooling. The length of the outer first channel sections 38 is at least partially the same. R.409178

[0054] - 10 -

[0055] Finally, Fig. 6 shows a heat sink 10e, which differs from the heat sink 10d according to Fig. 5 in that the second channel sections 36 or extensions of the inner first channel sections 35e are formed in the form of meanders 54 to 57, which also serve to improve the cooling of the first channel sections 35e.

[0056] The channel geometries of the heat sinks 10, 10a to 10e described so far can be modified or adapted in various ways without deviating from the inventive concept. In particular, it is also mentioned that the channel 14 is not limited to a planar channel 14 lying in the plane of the figures, but can also be designed as a 3-dimensional channel 14.

Claims

R.409178 - 11 - Claims 1. Pulsating heat pipe heat sink (10; 10a to 10e), comprising a housing (12) in which at least one meandering channel (14) for guiding an evaporable cooling medium is arranged, comprising an evaporator section (20; 20b; 20c) which is at least indirectly thermally connectable to a heat-generating component, comprising a condenser section (30) for condensing the cooling medium, wherein the at least one channel (14) has several first channel sections (35; 35a; 35c; 35d; 35e, 38; 38a; 38b; 38c) arranged parallel to each other, which are connected to each other by arcuate second channel sections (36) or by return sections (44), comprising inner first channel sections (35; 35a; 35c; 35d; 35e) which define the evaporator section (20; 20b; 20c) traverse and extend outside the evaporator area (20; 20b; 20c) towards the condenser area (30), and with outer first channel sections (38; 38a; 38b; 38c) which extend outside the evaporator area (20; 20b;20c), wherein at least some of the inner first canal segments (35; 35a; 35c; 35d; 35e) have a length (L) greater than a length (I) of outer first canal segments (38; 38a; 38b; 38c) connected to second canal segments (36).; 2. Cooling element according to claim 1, characterized in that the length (L) of the inner first channel sections (35a) in the evaporator area (20) increases in a direction perpendicular to the first channel sections (35a).

3. Cooling element according to claim 1, characterized in that the length (L) of the inner first channel sections (35) in the evaporator area (20) is in a direction perpendicular to the first channel sections (35, 38) in a central region of the R.409178 - 12 - The evaporator area (20) has a maximum and decreases towards the edge areas of the evaporator area (20).

4. Cooling sink according to one of claims 1 to 3, characterized in that the length (I) of the outer first channel sections (38; 38a; 38b) is different at least on one side of the evaporator area (20; 20b).

5. Cooling element according to claim 4, characterized in that the length of the outer first channel sections (38b) decreases in a direction away from the evaporator area (20b).

6. Heat sink according to one of claims 1 to 3, characterized in that the length of at least a part of the outer first channel sections (38) is the same, except in the area of ​​a return section (40).

7. Cooling element according to one of claims 1 to 6, characterized in that the evaporator area (20) and the at least one channel (14), with the exception of the return section (40), are arranged at least substantially centrally to the housing (12).

8. Cooling sink according to one of claims 1 to 6, characterized in that the at least one channel (14), with the exception of the return section (40), is arranged centrally to the housing (12) and the evaporator area (20b) is arranged laterally offset to the center of the housing (12).

9. Cooling sink according to one of claims 1 to 8, characterized in that the inner first channel sections (35d; 35e) are at least partially extended in the form of loops (51 to 53) or meanders (54 to 57). R.409178 - 13 - 10. Heat sink according to one of claims 1 to 9, characterized in that a single return section (40) is provided, which connects the two outermost first channel sections (38; 38a; 38b; 38c) outside the evaporator area (20; 20b) connects to each other.

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