DE102023123601A1 - heat exchanger - Google Patents

Abstract

Heat exchanger, in particular as a battery cooling device for an electric battery module of an electric drive on an electric vehicle, wherein the heat exchanger has a cooling circuit for circulating a tempering fluid, wherein the cooling circuit is formed between two plates partially connected to one another by roll cladding, wherein the plates are materially connected in bonded areas and are expanded in unconnected hollow areas to form the cooling circuit, wherein flow elements around which flow occurs on all sides are formed by the bonded areas, which influence a flow of the tempering fluid through the cooling circuit.

Description

The invention relates to a heat exchanger, in particular as a battery cooling device for an electric battery module of an electric drive on an electric vehicle, wherein the heat exchanger has a cooling circuit for circulating a tempering fluid, wherein the cooling circuit is formed between two plates that are connected to one another in regions by roll cladding, wherein the plates are materially connected in bonded regions and are expanded in non-connected hollow regions to form the cooling circuit, wherein flow elements around which the fluid flows on all sides are formed by the bonded regions, which influence a flow of the tempering fluid through the cooling circuit.

An electric vehicle includes, among other things, an electric machine as a drive source, which is electrically connected to electric battery modules as storage means. In drive mode, the electric machine converts electrical energy into mechanical energy to drive the electric vehicle. The electric battery modules, which are also simply referred to as batteries or accumulators, are usually cooled with a battery cooling device.

The EP 3 625 824 A1 relates to a heat sink comprising a substantially planar solid plate provided with a plurality of fluid flow channels, the plurality of fluid flow channels being configured to conduct a coolant from an inlet to an outlet of the plate, the plurality of channels comprising at least two main channels interconnected by at least a plurality of bridging channels which do not branch further between their respective attachment points to the main channels, the bridging channels having a cross-section which locally increases in the flow direction, and the bridging channels having a cross-section which locally decreases in the flow direction downstream of the local cross-sectional increase.

The US 11 583 929 B2 discloses a method of manufacturing a cold plate in which a fluid circuit is formed on a build surface in layers of a build material. The fluid circuit comprises a plurality of peripheral walls, each of the plurality of peripheral walls at least partially defining a primary channel, one of the peripheral walls being longitudinally formed to include openings configured to allow excess build material to pass therethrough. A central wall of the fluid circuit at least partially defines the primary channel and a plurality of secondary channels in fluid communication with the primary channel. The method further comprises removing excess build material through the openings.

The article " “Industrial application of topology optimization for forced convection based on Darcy flow” in Structural and Multidisciplinary Optimization (2022) 65: 265 , Springer-Verlag, concerns the design of a layout of flow channels, whereby a basic layout is created by topology optimization. The cooling of automotive battery packs is shown as an application example. The cooling is achieved by liquid flow through cooling channels that are manufactured by roll bonding. This manufacturing process enables complex channel patterns. The temperature on the battery modules is optimized so that it has a uniformly low value and at the same time the mechanical losses in the flow are kept to a minimum.

The DE 10 2021 122 913 A1 discloses a battery cooling device for an electric battery module of an electric drive on an electric vehicle, wherein the battery cooling device forms a substantially closed flow space for circulating a tempering fluid and wherein a plurality of flow elements are arranged in the flow space, which influence a flow of the tempering fluid through the flow space. The flow space is formed between two plates that are connected to one another in regions by roll cladding, wherein the plates are materially connected in bonded regions and are expanded in unconnected hollow regions in order to form the flow space, wherein the flow elements are formed by the bonded regions.

The design freedom offered by the roll-bonded manufacturing process is not fully exploited by the use of simple, geometrically idealized and recurring channel structures.

One object of the application may be to improve a heat exchanger by exploiting the design freedom of roll bonding with regard to its thermal and/or hydraulic properties.

The object is achieved by a heat exchanger according to claim 1. Further embodiments and developments can be found in the subclaims.

The heat exchanger, which is designed in particular as a battery cooling device for an electric battery module of an electric drive on an electric vehicle, has a cooling circuit for Circulation of a tempering fluid. The cooling circuit is formed between two plates that are connected to one another in some areas by roll cladding, whereby the plates are materially connected to one another in bonded areas and are expanded in non-connected hollow areas to form the cooling circuit. Flow elements that flow around on all sides are formed by the bonded areas, which influence a flow of the tempering fluid through the cooling circuit and determine a channel course of the cooling circuit, whereby the flow elements comprise at least one elongated wall with an aspect ratio greater than three and at least one point structure with an aspect ratio of up to three. A predominant proportion of the flow elements has a singular and asymmetrical shape of the respective flow element.

One advantage of the asymmetrical and singular shape of the flow elements is that a channel course is formed that is optimized in terms of thermal and/or hydraulic properties and deviates from standard shapes. Production by roll cladding allows a freedom of design that enables an optimized, bionic channel course whose elongated walls and point structures are mixed. The majority of the flow elements have a singular shape. The individual flow element is therefore unique and does not occur a second time in the channel course. The point structure with an aspect ratio of up to three is also known as a dimple. The aspect ratio in the asymmetrical shape is the ratio of a longest extension to a smallest extension of the point structure in the plane defined by the plates. In particular, the point structure can have an aspect ratio of less than two and particularly preferably an aspect ratio of less than 1.5. The aspect ratio of the elongated wall is calculated in the same way as that of the point structure. Use of the heat exchanger is not limited to the battery cooling device. The heat exchanger can also be used in other cooling and air conditioning devices, such as refrigerators or solar panels.

The cooling circuit is formed between two plates that are connected in some areas by roll bonding, whereby the plates are firmly bonded in bonded areas and expanded in non-connected hollow areas, whereby the flow elements are formed by the bonded areas. Roll bonding can also be referred to as roll bonding. The firm bond is avoided in the hollow areas by applying a coating before roll bonding. The hollow areas between the plates are expanded, for example, by introducing compressed air into the non-firm bonded areas between the plates. The hollow areas can be expanded on one side in one of the plates or on both sides in both plates. In both cases, the heat exchanger as a battery cooling device can have a flat contact surface for the battery modules.

Roll bonding or roll cladding as a manufacturing process for producing the heat exchanger offers various advantages. For example, depending on the application, different aluminum alloys from soft to high-strength can be used. Higher grades have a strength advantage, which has a positive effect on crash behavior. Depending on the material, thickness variation and geometry, roll bonding enables very high burst pressures of over 10 bar and/or up to 20 bar. Another advantage is that the strength of the heat exchanger is independent of temperature. In addition, there is a high degree of flexibility in the design of the heat exchanger, which can be made in one piece with just one upper and lower plate, or in several parts from a group of upper and lower plates. The cooling circuit can be installed on one side or both sides. A mixed steel construction is also possible with the connection technology, for example by using friction welding elements and/or adhesive. The cooling circuit created by expanding has a clean inner surface, which has a positive effect on the service life.

According to one embodiment, it is provided that a predominant part of the total length of the channel course has an asymmetrical shape. Thus, not only the individual flow elements are asymmetrical in themselves, but also the predominant part of the channel course, so that this can advantageously be freely designed and optimized. In particular, an arbitrarily selected section of a predominant part of the channel course can have a singular shape, i.e. not be unique in the channel course.

According to a further embodiment, it is provided that an edge region of the flow elements has a continuous, continuous course in a plane defined by the plates. The edge region is continuous in the mathematical sense, i.e. the edge region has a homogeneous curvature, without a kink or a sharp edge.

According to a further embodiment, it is provided that a channel cross-sectional area varies transversely to a flow direction of a channel section of the channel course in the flow direction, wherein a ratio of a largest channel cross-sectional area to a smallest channel cross-sectional area of the channel section can be at least 1.5, whereby the ratio of the largest channel cross-sectional area to the smallest channel cross-sectional area can be up to ten. The channel cross-sectional area can be constantly varying, i.e. not constant, in particular over a predominant part of the total length of the channel course. A width transverse to a flow direction of a channel section of the channel course can vary in the flow direction, whereby a ratio of a largest width to a smallest width of the channel section can be at least 1.5, whereby the ratio of the largest width to the smallest width can be up to four. The width can be constantly varying, i.e. not constant, in particular over a predominant part of the total length of the channel course. Alternatively or additionally, a height transverse to a flow direction of a channel section of the channel course can vary in the flow direction, whereby a ratio of a largest height to a smallest height of the channel section of the channel course can be at least 1.5, whereby the ratio of the largest height to the smallest height can be up to five. The height can vary continuously, i.e. not be constant, particularly over a large part of the total length of the channel. A flank angle and/or a flank radius of a channel section of the channel can vary in the direction of flow.

According to a further embodiment, it is provided that the channel course has at least one section in which only point structures are arranged. The channel course can in particular have at least eight point structures per square meter. Alternatively or additionally, the aspect ratio of the elongated walls can be on average at least seven, with the average being calculated as the mean value of the aspect ratios of all elongated walls of the channel course.

According to a further embodiment, it is provided that the channel course has a channel area, wherein a ratio of the channel area to an area over which heat power is introduced from the electric battery module is between 60 and 95 percent, in particular between 80 and 95 percent and preferably between 90 and 95 percent.

According to a further embodiment, it is provided that the cooling circuit has at least one first region with channel sections and at least one second region with channel sections, wherein a height of the channel sections in the first region is greater than a height of the channel sections in the second region and wherein the at least one second region corresponds to an area over which heat power is introduced from the electric battery module. The cooling circuit can have at least one third region with channel sections with a changing height, wherein the at least one third region is arranged between the at least one first region and the at least one second region.

• 1 eine Ausführungsform des Wärmetauschers;
• 2 ein Kanalverlauf der Ausführungsform gemäß 1;
• 3 einen Querschnitt eines beispielhaften Kanalverlaufs;
• 4 einen Längsschnitt eines beispielhaften Kanalverlaufs mit Höhenbereichen;
• 5 bis 10 jeweils Kanalverläufe weiterer Ausführungsformen;
• 11 einen Kanalverlauf einer weiteren Ausführungsform mit Höhenbereichen;
• 12 einen Längsschnitt eines beispielhaften Kanalverlaufs mit variierender Höhe;
• 13 einen Querschnitt eines beispielhaften Kanalverlaufs.

Embodiments of the heat exchanger are explained below with reference to the accompanying drawings.

• 1 an embodiment of the heat exchanger;
• 2 a channel course of the embodiment according to 1 ;
• 3 a cross-section of an example channel course;
• 4 a longitudinal section of an exemplary channel course with height ranges;
• 5 to 10 channel courses of further embodiments;
• 11 a channel course of another embodiment with height ranges;
• 12 a longitudinal section of an exemplary channel course with varying height;
• 13 a cross-section of an example canal route.

In the 1 a heat exchanger as a battery cooling device for an electric battery module of an electric drive on an electric vehicle is shown in a perspective view. The battery cooling device has a cooling circuit 1 for circulating a tempering fluid, wherein the cooling circuit 1 is formed between two plates 23, 25 that are connected to one another in some areas by roll cladding, wherein the plates 23, 25 are materially connected to one another in bonding areas 3 and are expanded in unconnected hollow areas 4 in order to form the cooling circuit 1. Flow elements 5, 6 and wall areas 17 that are flowed around on all sides are formed by the bonding areas 3, wherein the flow elements 5, 6 influence a flow of the tempering fluid through the cooling circuit 1 and determine a channel course of the cooling circuit. Apart from connections 2 that lead to the outside, which serve as inlet and return for the tempering fluid, the cooling circuit 1 is closed in a gas-tight manner. Of the externally routed connections 2, one is located below the battery cooling device and is therefore not visible.

The channel course of the embodiment according to 1 is in the 2 shown. The currents The flow elements 5, 6 comprise a plurality of elongated walls 5 with an aspect ratio of greater than three and several point structures 6 with an aspect ratio of up to three. A predominant proportion of the flow elements 5, 6 has a singular and asymmetrical shape of the respective flow element 5, 6. For the sake of clarity, only some of the elongated walls 5 and the point structures 6 are provided with reference symbols as examples on the channel course. The channel course has several sections 10 in which only point structures 6 are arranged. The 2 The channel course shown shows irregular, bionic structures, which cannot be composed of standard design elements. A channel width of, for example, 10 millimeters is not exceeded. The smallest channel width can be a quarter of a maximum channel width. The channel course has only continuous boundaries, so there are no sharp edges on the flow elements 5, 6.

The channel course shows irregular, bionic channel structures, with clearly varying channel widths. Elongated walls 5 and point structures 6 are mixed. The channel course has several branching points 7 that do not have a Y shape, i.e. at which at least four branching branches 8 meet. The branching branches 8 are not differentiated according to inflow or outflow direction. Therefore, a connection 2 also counts as a branching branch 8. To form a flow and a return, another connection is arranged perpendicular to a plane of the plates 23, 25, which is not visible here. The channel course has an asymmetrical shape overall. Furthermore, any section of the channel course has a singular shape, i.e. it does not repeat itself along the channel course.

In the exemplary embodiment, a total of ten rectangular surfaces 11 mark installation areas for battery modules. The channel course takes up a channel area, with a ratio of the channel area to the area 11, over which heat output is introduced by the electric battery module, being between 60 and 95 percent. The proportion of the area covered by channel sections can be particularly large with the bionic-shaped channel course, since the design freedom is fully exploited. Outside the surfaces 11, for example, fastening areas 16 are arranged, in which the ratio is significantly lower.

In the 3 is a cross-section through a channel section of an exemplary channel course. The two plates 23, 25 are connected to one another in the composite areas 3. The upper plate 23 is widened in the unconnected hollow area 4. An edge area 9 of the flow elements 5, 6 formed by the composite area 3 has a continuous, continuous course in the plane defined by the plates 23, 25. A flow direction is perpendicular to the drawing plane of the 3 . A channel cross-sectional area transverse to the flow direction of the channel section can vary along the channel course in the flow direction, wherein a ratio of a largest channel cross-sectional area to a smallest channel cross-sectional area of the channel section can be at least 1.5. For example, a width w can vary transverse to the flow direction of the channel section. Additionally or alternatively, a height h can vary transverse to the flow direction of the channel section of the channel course. It follows that a flank angle α and/or a flank radius r of a channel section of the channel course can also vary in the flow direction.

In the 4 a longitudinal section through a channel section of an exemplary channel course is shown, with the height h being higher in a first area 12 than in a second area 14. The height h increases continuously over a third area 15 between the areas 12 and 14. The inner channel height h varies here between two levels with a continuous connection, which can, however, also have a non-linear course. It would also be possible that no constant height exists, but rather a continuously varying height is implemented.

In the 5 to 10 Further exemplary channel courses of further embodiments are shown.

The 5 shows a diagonally flowing cooling circuit 1 with a connection 2 at the bottom left for the flow and another connection 2 at the top right for the return. The channel course shows more point structures 6 than elongated walls 5.

The 6 shows a vertically flowing cooling circuit 1 with a connection 2 at the bottom left for the flow and another connection 2 at the top left for the return. The channel course shows more elongated walls 5 than point structures 6.

The 7 shows a section of another cooling circuit 1, the channel course of which shows more elongated walls 5 than point structures 6, whereby some elongated walls 5 are connected to fastening areas 16.

The 8 shows a section of another cooling circuit 1, the channel course of which has longer elongated walls 5, the cooling circulation after 7 . Shorter elongated walls 5 are connected to the fastening areas 16.

The 9 shows a section of another cooling circuit 1, the channel course of which has equally elongated walls 5 and point structures 6.

The 10 shows a section of another cooling circuit 1, the channel course of which also has equally elongated walls 5 and point structures 6.

In the 11 a channel course of a further embodiment with height regions is shown. The cooling circuit 1 has first regions 12 with channel sections and second regions 14 with channel sections, wherein a height of the channel sections in the first regions 12 is greater than a height of the channel sections in the second regions 14. The second regions 14 correspond to a surface 11 over which heat output is introduced from the electric battery module ( 2 ). Third areas 15 with channel sections with variable heights are arranged between the first areas 12 and the second areas 14. Larger channel heights are useful in the areas in which no heat is introduced, since here only the pressure loss should be kept as low as possible, while the thermal contribution is negligible. For this purpose, large channel cross-sections due to high channel heights are particularly useful. This applies in particular to the areas of the connections for flow and return up to the surfaces 11 of the heat input, as well as to the areas between the surfaces 11 with battery modules. Between the first areas 12 and the second areas 14, each with a constant height, are the third areas 15 as transition areas with continuously varying channel heights. In the second areas 14 of the heat input, low channel heights can be advantageous in order to increase the fluid velocity and improve heat dissipation.

The first area 12 on the left in the 11 with the connection 2 for the flow and feed channels to the surfaces 11 of the heat input has a large channel height, for example an inner channel height of 3.5mm. The adjoining third area 15 is a transition area with a continuously varying channel height. The left second area 14 is a module area 11 with battery modules, i.e. with heat input, and has a lower channel height, for example an inner channel height of 1.5mm. The adjoining third area 15 is a transition area with a continuously varying channel height. The middle first area 12 is a connection area between the surfaces 11 of the heat input with a large channel height, for example an inner channel height of 3.5mm. The adjoining third area 15 is again a transition area with a continuously varying channel height. The right second area 14 is a module area 11 with battery modules, i.e. with heat input, and has a lower channel height, for example an inner channel height of 1.5mm. The following third area 15 is a transition area with continuously varying channel height. The first area 12 on the right in the 11 with the connection 2 for the return and supply channels from the surfaces 11 of the heat input has a large channel height, for example an inner channel height of 3.5 mm.

In the 12 is a longitudinal section of an exemplary channel course between the plates 23, 25 with varying height h. The height h varies continuously over the channel section shown, i.e. is not constant over any area, which is indicated by the two heights h drawn.

In 13 a cross-section through a channel section of an exemplary channel course is shown. The two plates 23, 25 are materially connected to one another in the bonding areas 3. In the exemplary embodiment shown, both plates 23, 25 are expanded in the unconnected hollow area 4.

list of reference symbols

1

cooling circuit

2

Connection

3

network area

4

hollow areas

5

flow element, elongated wall

6

flow element, point structure

7

branching point

8

branching branch

9

peripheral area

10

Section in which only point structures are arranged

11

area over which heat output is introduced

12

First Area

14

Second area

15

Third Area

16

mounting area

17

wall area

23

plate

25

plate

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 3 625 824 A1 [0003]
• US 11 583 929 B2 [0004]
• DE 10 2021 122 913 A1 [0006]

Cited non-patent literature

• “Industrial application of topology optimization for forced convection based on Darcy flow” in Structural and Multidisciplinary Optimization (2022) 65: 265 [0005]

Claims (18)

Heat exchanger, in particular as a battery cooling device for an electric battery module of an electric drive on an electric vehicle, wherein the heat exchanger has a cooling circuit (1) for circulating a tempering fluid, wherein the cooling circuit is formed between two plates that are connected to one another in some areas by roll cladding, wherein the plates (23, 25) are materially connected to one another in bonded areas (3) and are expanded in non-connected hollow areas (4) in order to form the cooling circuit (1), wherein flow elements (5, 6) around which flow flows on all sides are formed by the bonded areas (3), which influence a flow of the tempering fluid through the cooling circuit (1) and determine a channel course of the cooling circuit, wherein the flow elements comprise at least one elongated wall (5) with an aspect ratio greater than three and at least one point structure (6) with an aspect ratio of up to three, characterized in that a predominant proportion of the flow elements has a singular and asymmetrical shape of the respective flow element (5, 6). heat exchanger after claim 1 , characterized in that the channel course has at least one branching point (7) with at least four branching branches (8). Heat exchanger according to one of the preceding claims, characterized in that a predominant part of a total length of the channel course has an asymmetrical shape. Heat exchanger according to one of the preceding claims, characterized in that any section or a predominant part of a total length of the channel course has a singular shape. Heat exchanger according to one of the preceding claims, characterized in that an edge region (9) of the flow elements (5, 6) has a continuous, continuous course in a plane defined by the plates. Heat exchanger according to one of the preceding claims, characterized in that a channel cross-sectional area transverse to a flow direction of a channel section of the channel course varies in the flow direction. heat exchanger after claim 6 , characterized in that a ratio of a largest channel cross-sectional area to a smallest channel cross-sectional area of the channel section is at least 1.5. Heat exchanger according to one of the preceding claims, characterized in that a width (w) transverse to a flow direction of a channel section of the channel course varies in the flow direction. heat exchanger after claim 8 , characterized in that a ratio of a largest width to a smallest width of the channel section is at least 1.5. Heat exchanger according to one of the preceding claims, characterized in that a height (h) transverse to a flow direction of a channel section of the channel course varies in the flow direction. heat exchanger after claim 10 , characterized in that a ratio of a maximum height to a minimum height of the channel section of the channel course is at least 1.5. Heat exchanger according to one of the preceding claims, characterized in that a flank angle (α) and/or a flank radius (r) of a channel section of the channel course varies in the flow direction. heat exchanger after claim 12 , characterized in that the channel course has at least one section (10) in which exclusively point structures (6) are arranged. Heat exchanger according to one of the preceding claims, characterized in that the channel course has at least eight point structures (6) per square meter. Heat exchanger according to one of the preceding claims, characterized in that the aspect ratio of the elongated walls (5) is on average at least seven. Heat exchanger according to one of the preceding claims, characterized in that the channel course occupies a channel area, wherein a ratio of the channel area to an area (11) over which heat output is introduced from the electric battery module is between 60 and 95 percent, in particular between 80 and 95 percent and preferably between 90 and 95 percent. Heat exchanger according to one of the preceding claims, characterized in that the cooling circuit (1) has at least a first region (12) with channel sections and at least a second region (14) with channel sections, wherein a height of the channel sections in the first region (12) is greater than a height of the channel sections in the second region (14) and wherein the at least one second region corresponds to a surface (11) via which heat output is introduced from the electric battery module. heat exchanger after claim 17 , characterized in that the cooling circuit (1) has at least one third region (15) with channel sections of variable height (h), wherein the at least one third region (15) is arranged between the at least one first region (12) and the at least one second region (14).

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