EP4310429A1 - Integratable passive heat dissipation - Google Patents

Abstract

The invention relates to a device for heat removal with at least one additively manufactured two-phase cooling device and a manufacturing method for such a device. The device for heat removal includes at least one additively manufactured three-dimensional two-phase cooling device, which is formed from electrically insulating material.

Description

The invention relates to a device for heat dissipation with at least one additively manufactured two-phase cooling device and a manufacturing method for such a device.

In the highly current development field of electrical systems such as electric motors, generators, battery cells, but also control cabinets or in data centers, several hotspots are emerging in different places. These are often difficult to reach due to a compact design to save space. However, the hotspots must be effectively cooled to ensure safe operation. Simple metallic heat sinks or fan cooling systems are unsuitable for this. Work is underway to dissipate heat through smaller channels, which place high demands on the production of such heat dissipation devices.

Copper pipes and heat pipes are preferred for highly effective heat dissipation. Heat pipes can be designed as pulsating heat pipes in which gas and liquid phases alternate and transport the heat away through several turns. However, such heat dissipation devices made of copper pipes and heat pipes are not suitable for dissipating the amounts of heat from the compact systems described for structural or design reasons. Due to the difficulty of access, they have to be guided around other components. But copper pipes cannot simply be bent multiple times. This creates material weak points that reduce longevity. There can also be bottlenecks for the coolant inside the pipe if the windings are too tight or if the copper pipes are bent, which in turn makes heat dissipation inefficient.

In areas such as electromobility but also converters, several cooling circuits or heat exchanger systems are installed for efficient heat dissipation. However, the limited installation space also represents a challenge here, so restrictions must be made with regard to the design. State-of-the-art solutions in limited installation space only allow a certain amount of heat dissipation.

Based on the prior art described above, the invention is based on the object of providing an improved heat removal device for hard-to-reach places to be heat-removed in compact structures.

This task is solved by the features of independent patent claim 1. Claim 13 specifies a manufacturing process for a device according to the invention.

Advantages and refinements of the invention, which can be used individually or in combination with one another, are the subject of the subclaims.

The heat dissipation device according to the invention comprises at least one additively manufactured three-dimensional two-phase cooling device, which is made of electrically insulating material.

Such a device initially has the advantage that it is a passive cooling device. This has, among other things, The advantage, in contrast to active cooling devices such as fans or pumped cooling water circuits, is that no active operation of the device is necessary after the device has been installed for cooling purposes.

The electrically insulating material has, among other things, the advantage that it electrically insulates the device from other components, particularly when used in electrically sensitive areas such as control cabinets. Furthermore, the Device also insensitive to alternating electromagnetic fields.

The heat removal device according to the invention is particularly advantageously integrated, i.e. H. If necessary, it can also be directly structurally connected to the component to be cooled.

The additively manufactured three-dimensional two-phase cooling device has the particular advantage of being able to be adapted specifically to the designs of the components to be cooled or to the designs of the entire system in which the locations to be cooled are located. For example, additive manufacturing eliminates a bending step of a pipe carrying coolant, which overcomes the described disadvantages of pipe bending. In contrast to two-dimensional, planar cooling devices, the three-dimensional structure has the advantage of increased stability. The three-dimensional two-phase cooling device can reach hard-to-reach places similar to an octopus arm.

Additive manufacturing generally allows a very individual design of the device. Several two-phase cooling devices can also be designed in the form of three-dimensional arms that reach hotspots at very different locations. The device can be ideally adapted to the entire system.

Non-electrically conductive materials include insulators such as ceramics, plastics, polymers but also naturally occurring organic materials such as rubber.

Two-phase cooling or two-phase cooling devices are understood to mean all cooling processes and cooling devices that are based on the functional principle that a working medium, ie a refrigerant, evaporates at the point to be cooled and, after this heat has been dissipated, is led to another point and boils there again. This type of heat transfer uses the enthalpy of vaporization of the working medium to ensure a high heat flux density. Examples of such two-phase cooling devices are heat pipes, thermosyphons or heat pipes, the basic functionality of which is known. The work equipment known from the prior art also comes into question.

In an advantageous embodiment of the invention, the cooling device is in particular a heat pipe. The embodiment of the device with a pulsating heat pipe is particularly preferred. The terms pulsating heat pipe and oscillating heat pipe are used in the literature. Alternatively, a version as a thermosiphon would also be possible.

A heat pipe is a heat exchanger that allows a high heat flux density using the enthalpy of vaporization of a fluid. In this way, large amounts of heat can be transferred to a small cross-sectional area. For this purpose, a heat pipe includes at least one steam channel and a condensate channel, which leads condensed fluid back to the evaporator, the so-called wick principle. The process is therefore independent of the location. The liquid flow takes place through capillaries and can be significantly improved using porous structures within the channels.

With the pulsating heat pipe, the fluid does not flow back using the wick principle, but instead comprises several turns of thin channels that are only partially filled with liquid. As a result, working fluid in the channel is alternately in liquid and gaseous form. The vapor segments are expanded at the point to be cooled, and the liquid segments are expanded on the condenser side. The basic functionality of heat pipes and pulsating heat pipes is known. So far, only planar pulsating heat pipes are known, in which the several turns lie in one plane.

In an advantageous embodiment of the invention, the two-phase cooling device comprises thermoplastics or thermosets. These materials can be used particularly well for additive manufacturing processes. In a particularly advantageous embodiment of the invention, the thermoplastics or thermosets additionally contain sand, carbon fibers and/or glass fibers. This embodiment has the advantage that the strength as well as the temperature resistance of the two-phase cooling device is increased. The listed materials are also of particular advantage for the three-dimensional design of the two-phase cooling device. The two-phase cooling device acts as a dimensionally stable octopus arm to access the component to be cooled and is also adapted to its structural environment.

Thermoplastics are preferably processed using fused deposition modeling (FDM) or selective laser sintering (SLS), thermosets are preferably processed using stereolithography (SLA) or digital light processing technology (DLP).

In a further advantageous embodiment of the invention, the device, in particular the two-phase cooling device, comprises a polymer, in particular acrylonitrile-butadiene-styrene copolymer (ABS), polycaprolactam (polyamide 6, PA6 for short), polyetherimides (PEI) or a palladium-doped liquid crystal polymer (LCP).

In a particularly advantageous embodiment of the invention, the device has a two-phase cooling device with a large number of channels. The channels can be individual heat pipes or a large number of turns of a pulsating heat pipe. Preferred numbers are 3 to 20 channels. The channels are not planar, but are arranged in such a way that the three-dimensionality of the cooling device is created, the so-called octopus arm. The cross section through this arm, i.e. through the two-phase cooling, can also vary in shape and size and be adapted to the available space and application. The individual channels preferably have diameters between 1 mm and 2 mm. In particular, the channels have a porous filling.

In a special embodiment of the invention, the device for heat dissipation, in particular the two-phase cooling device, is covered with a protective layer. The protective layer can be hermetically sealed. The protective layer is designed in particular in such a way that it acts against the diffusion of oxygen into the cooling channel or channels. The protective layer can be very thin, but for its purpose it should have a layer thickness greater than 0.5 µm. Suitable materials for the protective layer are materials that are effective against the indiffusion of oxygen. A special embodiment could also have a metallic protective layer.

In a further advantageous embodiment of the device, at least one heat input surface and/or at least one heat dissipation surface is included, which have a high thermal conductivity. High thermal conductivity means a thermal conductivity of more than 100 W/(m K), preferably more than 200 W/(m K), in particular more than 300 W/(m K) or particularly preferably more than 400 W/ (m K). The heat input surface and the heat dissipation surface serve to input heat from the point to be cooled into the device or to dissipate heat to the environment or another cooling device from the two-phase cooling device. The heat input surface or heat dissipation surface can serve in particular as a contact surface to the component to be dissipated or to the environment.

The heat input surface and/or heat dissipation surface can comprise metal or plastic; the surfaces expediently have a high thermal conductivity. Also one Designing the inlet and outlet surface from a polymer composite or comprising a polymer composite can be particularly advantageous since this can be additively manufactured in the same manufacturing step with the two-phase cooling device. Alternatively, the heat input and heat dissipation surfaces can comprise an inlay, in particular an inlay made of metal and/or a ceramic, which is pressed into the structure of the two-phase cooling device, glued in or welded to the structure.

The device for heat dissipation can comprise several two-phase cooling devices, which have the same structure in terms of the heat dissipation principle, but are different in terms of shape, namely adapted to the respective hotspot to be dissipated and its surroundings: For example, one embodiment of the device comprises at least two heat input surfaces, which are thermally connected to a common heat dissipation surface via a two-phase cooling device. Alternatively, an exemplary embodiment of the device comprises two heat dissipation surfaces, each of which is thermally connected to a common heat input surface via a two-phase cooling device.

In particular, a device for heat dissipation can be designed in such a way that it has a large number of two-phase cooling devices in the shape of an octopus arm, which penetrate a complex, structurally sealed apparatus up to the respective hotspots. Multiple heat dissipation surfaces are an advantage for efficient heat dissipation.

The method according to the invention for producing a device for heat dissipation according to the invention comprises an additive manufacturing method for the two-phase cooling device.

In particular, the additively manufactured two-phase cooling device is subsequently coated with a protective layer. The protective layer is created in particular by means of one of the Process Electroplating metallization, sputter deposition, chemical vapor deposition or thermal spraying.

In an advantageous embodiment of the invention, both a two-phase cooling device and a heat input surface and/or heat dissipation surface are produced using additive manufacturing in the same manufacturing step. This increases the efficiency of the manufacturing process.

For example, an additive manufacturing process of the following examples can be used in the manufacturing process: material extrusion, stereolithography, selective laser sintering, binder jetting, film lamination or direct laser deposition.

Depending on the geometry to be produced, the processes can also be used with other processes, e.g. B. gluing, welding or surface treatment processes can be combined.

The materials to be printed are usually thermoplastics, as in fused deposition modeling (FDM) or selective laser sintering (SLS), or thermosets, as in stereolithography (SLA) or digital light processing technology (DLP). Other materials can also be added to increase strength or temperature resistance, such as sand, carbon fibers or glass fibers. A subsequent coating with a protective layer larger than 0.5 µm can be used to make the system vacuum-tight.

Various methods are available for depositing the protective layer. A chemical process that can be used on polymers such as acrylonitrile-butadiene-styrene copolymer (ABS), polycaprolactam (polyamide 6, PA6 for short), polyetherimides (PEI), palladium-doped liquid crystal polymers (LCP) is galvanic metallization on a roughened surface. The roughening can e.g. B. using chromosulfuric acid pickling. Alternative procedures, which also work for Ceramic protective layers that are suitable include sputter deposition, chemical vapor deposition or thermal spraying.

Figur 1:

eine Batteriekühlung mit Heatpipes 1,

Figur 2:

einen Motor 22 mit gebogenen Heatpipes 1,

Figur 3:

eine pulsierende Heatpipe schematisch,

Figur 4:

mehrere Hotspots werden gekühlt und zentral abgeführt 3,

Figur 5:

eine Wärmeabführfläche 3 mit Inlay,

Figur 6:

mehreren individuell gestalteten Wärmeeintragsflächen 2,

Figur 7:

eine Ausführung, bei der die Wärme jedes Hotspots einzeln abgeführt wird,

Figur 8:

eine Schnittansicht der Kanalführung 10 innerhalb der Kunststoffrohre 1 längs,

Figur 9:

eine Schnittansicht der Kanalführung 10 innerhalb der Kunststoffrohre 1 mit poröser Kanalfüllung 12 längs,

Figur 10:

eine Schnittansicht der Kanalführung 10 quer,

Figur 11:

eine Schnittansicht der Kanalführung 10 quer mit anderer Querschnittsform,

Figur 12:

eine Schnittansicht der Kanalführung 10 innerhalb der Kunststoffohre 1 quer mit dreieckiger Querschnittsform des Rohrs 1 und

Figur 13:

eine Schnittansicht der Kanalführung 10 quer mit individuell angepasster Querschnittsform an einen baulich freien Zugangsbereich für maximalen Wärmeabtransport.

Further features, properties and advantages of the present invention emerge from the following description with reference to the accompanying ones Figures 1 to 13 . It shows schematically:

Figure 1:

battery cooling with heat pipes 1,

Figure 2:

a motor 22 with curved heat pipes 1,

Figure 3:

a pulsating heat pipe schematic,

Figure 4:

several hotspots are cooled and drained centrally 3,

Figure 5:

a heat dissipation surface 3 with inlay,

Figure 6:

several individually designed heat input surfaces 2,

Figure 7:

a version in which the heat from each hotspot is dissipated individually,

Figure 8:

a longitudinal sectional view of the channel guide 10 within the plastic pipes 1,

Figure 9:

a longitudinal sectional view of the channel guide 10 within the plastic pipes 1 with porous channel filling 12,

Figure 10:

a cross-sectional view of the channel guide 10,

Figure 11:

a cross-sectional view of the channel guide 10 with a different cross-sectional shape,

Figure 12:

a cross-sectional view of the channel guide 10 within the plastic pipes 1 with a triangular cross-sectional shape of the pipe 1 and

Figure 13:

a cross-sectional view of the channel guide 10 with an individually adapted cross-sectional shape to a structurally free access area for maximum heat dissipation.

In the exemplary embodiments and figures, identical or identically acting elements can each be provided with the same reference numerals. The elements shown and their size ratios In principle, each element should not be viewed as true to scale; rather, individual elements may be shown with relatively larger dimensions for better display and/or understanding.

The Figures 1 and 2 each show an application example for an embodiment of the cooling device according to the invention. In the Figure 1 A block with battery cells 21 is shown schematically, which is coupled to a large common heat input surface 2 via thermal connecting elements. From this heat input surface 2, several heat pipes 1 lead to a heat dissipation surface 3. This is preferably connected to a heat sink. For example, this is an air heat sink with cooling fins. Alternatively, heat can be dissipated via water cooling. The heat input surface 2 and the heat dissipation surface 3 preferably have metal inlays for increasing the heat input and heat output.

Figure 2 shows an alternative application, an electric motor 22. This has various curved heat pipes 1, which run along the outside of the motor housing, being thermally coupled to the motor 22 at different points, preferably via heat input surfaces 2 (not explicitly shown).

In Figure 3 The basic functional principle of the pulsating heat pipe 1 is also outlined, the cooling channel 10 of which forms a closed cooling system in several turns. The heat pipe channel 10 can be filled with porous material 12, for example. The heat removal Q takes place from the hot side h to the cold side c. While only planar pulsating heat pipes are known in the prior art, the present invention specifies a three-dimensional pulsating heat pipe 1 whose channels 10 are not arranged in a plane but in a bundle. This bundle can have different cross-sectional shapes, which are in the Figures 10 to 13 are shown. In the Figures 8 and 9 Longitudinal sections through the bundle are shown, but there are no planar design of the pulsating heat pipe should suggest.

The Figure 4 first shows a large planar heat dissipation surface 3, which can have a heat sink, which z. B. dissipates heat Q via water or metal inlays. Alternatively, coupling to an air heat sink with cooling fins is possible. Several two-phase cooling devices 1 lead from this common large execution area 3: The three two-phase cooling devices 1 shown have, for example, different diameters and correspondingly different numbers of cooling channels 10. This can be an adaptation to a design and/or to the amount of heat Q to be dissipated. All cooling device arms 1 each end in a heat input surface 2, which can be adapted to the component to be cooled for the most efficient heat connection possible. For example, one heat input surface 2 can be designed to be very small and compact, while a larger contact surface 2 is available for another hotspot to be cooled.

The Figure 5 shows a comparable image of a common heat dissipation surface 3 with different cooling device arms 1 to three different heat input surfaces 2. A metallic inlay is shown on the heat transfer surface 3. This can be a metal foil, for example. These embodiments allow multiple hotspots to be cooled at different locations. Through additive manufacturing, a heat pipe arm 1 can be individually adapted to the system and integrated into it. The heat Q is then dissipated centrally to water or air cooling 3.

Figure 6 shows a third view of the same embodiment, in which it is clearly visible how different the size and shapes of the cooling arms 1 and the heat input surfaces 2 can be.

In Figure 7 An alternative embodiment of the device according to the invention for cooling hotspots is shown. Here too, several cooling arms 1 with different heat input surfaces 2 are shown. The cooling arms each have their own heat discharge surface 3. Depending on the orientation in a control cabinet or engine compartment, the heat Q can be dissipated at different locations or via different systems.

The Figures 8 to 13 each show cross sections through the channel guide 10 within the heat pipe octopus arms 1: Figures 8 and 9 each show a longitudinal section, in which it is shown that the cooling channels 10 can have different diameters or can be filled with porous material 12.

The Figures 10 to 13 show how individually the cross section of the cooling arms 1 can be designed in order to be able to install as many cooling channels 10 as possible in a given space.

Although the invention has been illustrated and described in detail by the exemplary embodiments shown, the invention is not limited by the examples disclosed.

Reference symbols

1

Heat pipe

2

Heat input

3

Heat dissipation via heat sinks, e.g. water, metal inlays, air heat sinks with fins

10

Channel for pulsating heat pipe

11

Metal lid

12

Canal with porous filling

21

Battery cell (simulator)

22

electric motor

H

Hot side, evaporator

c

Cold side, condenser

Q

Heat Inside the pipe: alternating liquid and vapor phases
The condenser or cold side can have a heat pipe valve

Claims (15)

Device for heat dissipation, comprising at least one additively manufactured three-dimensional two-phase cooling device (1), which is made of electrically insulating material. Device according to claim 1, wherein the two-phase cooling device (1) is in particular a heat pipe, in particular a pulsating heat pipe. Device according to claim 1 or 2, wherein the two-phase cooling device (1) comprises thermoplastics or thermosets. Device according to one of the preceding claims, wherein the two-phase cooling device (1) comprises a polymer, in particular acrylonitrile-butadiene-styrene copolymer (ABS), polycaprolactam (PA6), polyetherimides (PEI) or a palladium-doped liquid crystal polymer (LCP). Device according to one of the preceding claims, wherein the two-phase cooling device has a plurality of channels. Device according to one of the preceding claims, wherein the two-phase cooling device (1) is covered with a protective layer. Device according to one of the preceding claims, comprising at least one heat input surface (2) and/or at least one heat dissipation surface (3). Device according to the preceding claim 7, wherein the heat input surface (2) and/or heat dissipation surface (3) comprise a metal or a plastic with high thermal conductivity. Device according to the preceding claim 8, wherein heat input surface (2) and/or heat dissipation surface (3)
include a polymer composite with high thermal conductivity, which was additively manufactured in the same manufacturing step with the heat pipe. Device according to claim 8, wherein the heat input surface (2) and/or heat dissipation surface (3) comprise an inlay made of metal and/or ceramic, which is pressed, glued or welded into the structure. Device according to one of the preceding claims 7 to 10, comprising at least two heat input surfaces (2), each of which is thermally connected to a common heat dissipation surface (3) via a two-phase cooling device (1). Device according to one of the preceding claims 7 to 10, comprising at least two heat dissipation surfaces (3), each of which is thermally connected to a common heat input surface (2) via a two-phase cooling device (1). Method for producing a device according to one of the preceding claims, in which the two-phase cooling device (1) is produced by means of additive manufacturing. Method according to claim 13, in which both the two-phase cooling device (1) and the heat input surface (2) and/or heat dissipation surface (3) are produced by means of additive manufacturing in the same manufacturing step. Method according to one of claims 12 or 13, in which one of the additive manufacturing processes material extrusion, stereolithography, selective laser sintering, binder jetting, film lamination or direct laser deposition is used.

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