FR3101731A1 - "Device for cooling an electrical element liable to release heat in operation" - Google Patents

Abstract

The invention relates to a thermal management device (1) for an electrical element capable of releasing heat in operation (2), in particular for an electric or hybrid vehicle, comprising a housing (11) for receiving said at least one electrical element (2), said receiving box (11) comprising a first tray (6) arranged so as to present: a housing (3) arranged to receive an electrical element (2), this housing (3) being arranged so as to extend over a first height (h1) less than the total height (H) of the first tray (6), so that the electrical element, once mounted in the housing, extends outside of said housing (3) over a second height (h2) of the electrical element (2) distinct from the first height (h1), said housing having a cross section (t), a reservoir (4) intended to contain a dielectric fluid and having a third height h3, said tank com communicating with the housing so that the electrical element can extend into said tank over the second height (h2), the tank having a cross section (T) greater than the cross section (t) of the housing (3). [Fig. 1]

Description

"Device for cooling an electrical element liable to give off heat in operation"

The present invention lies in the field of devices for thermal regulation of electrical elements capable of releasing heat in operation.

Electrical elements, whether electrical energy storage cells, integrated circuits, servers, data centers, etc. require thermal regulation in order to maintain them within their operating temperature range.

Data centers around the world currently represent 10% of global electricity consumption. The advent of “blockchain” and 5G technologies means that this percentage could increase drastically in the coming years. At least half of this consumption comes from the cooling systems of these data centers. Currently the majority of data centers are air-cooled by cooling the ambient air of the storage rooms by air conditioning devices. The optimal operating temperature for data centers is between 5°C and 40°C, more particularly around 27°C. Taking into consideration that air has a very low conductivity, in order to sufficiently cool the electrical elements, which can reach temperatures exceeding 60°C, the temperature difference between the air and the electrical elements to be cooled must be important and therefore this type of device is very energy-intensive.

In the automotive field for example, it is known to implement electric batteries in the form of electronic modules capable of releasing heat in operation. Each module may comprise a plurality of electronic cells capable of releasing heat in operation received in a housing. High density energy storage cells such as Li-ion or Li-polymer batteries ideally need to operate in a temperature range between 20°C and 40°C, and too low a temperature impacts their autonomy while too high a temperature affects their lifespan.

The various battery cells of an electrical storage system can in particular be cooled by means of a cold plate inside which a cooling fluid circulates, the plate being in contact with the battery cells to be cooled. It has been observed that such heat exchangers can lead to inhomogeneous cooling of the electric batteries of the same electric storage system, then leading to a reduction in the performance of these electric batteries. These thermal treatment devices also have a high thermal resistance due to the thicknesses of material present between the cooling fluid and the battery cells, another parameter contributing to the high thermal resistance being the contact between the cooling plates, the interfaces (PAD) and cell surfaces.

In order to provide an answer to these different problems, several devices are known.

The document FR3037727 is known in particular, in which a device for cooling the electric batteries of electric or hybrid cars is disclosed. More particularly, this document relates to a device for cooling the cells of the electric batteries of a battery pack of the Ion-Lithium type. It comprises a hermetically sealed case in which a dielectric fluid circulates. The electrical storage cells are partially immersed in the dielectric fluid, so that the heat exchange between the cells and the dielectric fluid is ensured. Thus, the cooling of the electric batteries is carried out by immersing the cells of the electric batteries in said fluid. An additional deformable reserve of dielectric fluid consists of a tank located outside the casing and makes it possible to limit pressure variations due to fluid temperature variations.

However, the total immersion of electrical storage cells in a fluid, in particular dielectric, presents problems of size, weight and price.

The object of the invention is to offer an alternative for the thermal management of electronic elements liable to release heat in operation by at least partially overcoming the aforementioned problems of the state of the art, thus optimizing the lifespan as well as the performance of such an electrical element. The invention can advantageously be used in the automotive field for, for example, thermally regulating a power electronics element or an electrical energy storage element, or even in the field of data centers for cooling servers and other electrical elements.

More particularly the invention relates to a:
Thermal management device for an electrical element capable of releasing heat in operation, comprising a receiving box for said at least one electrical element, said receiving box comprising a first tray arranged so as to present:

a housing arranged to receive an electrical element, this housing extending over a first height "h1" less than a total height "H" of the first tray, so that the electrical element once mounted in the housing extends outside of said housing over a second height h2 of the electrical element, said housing having a cross section t,

a reservoir intended to contain a dielectric fluid and having a third height h3, said reservoir communicating with the housing so that the electrical element can extend into said reservoir over the second height h2,
the reservoir having a cross section T greater than the cross section t of the housing.

Throughout the description, the terms “lateral”, “transverse” and “vertical” refer to an arbitrary orientation of a thermal management device according to the invention in an orthonormal frame Oxyz. Thus, a “transverse” direction corresponds to a direction parallel to an Ox axis, a “lateral” direction corresponds to a direction parallel to an Oz axis and a “vertical” direction corresponds to a direction parallel to an Oy axis. cross section” refer to sections made according to a plane, called the transverse plane, parallel to the plane Oxz in which the transverse axis Ox and the lateral axis Oz are inscribed. The terms “vertical section” refer to sections made according to a plane, called the vertical plane, parallel to the plane Oxy in which the transverse axis Ox and the vertical axis Oy are inscribed.

The term "tank" is understood to mean an element advantageously having a bottom, said bottom extending mainly in one plane, and side walls linked to said bottom extending in planes secant to the plane of the bottom.

Throughout the description, thermal interaction means that heat transfer is possible.

Throughout the description, the term "first height" refers to the height of the housing, the term "total height" refers to the height of the first tray, the term "second height" refers to the height of an electrical element, and the term “third height” refers to the height of the tank.

Thus, the thermal management device according to the invention, once assembled with at least one electrical element, the part of said electrical element emerging from the housing over a height h2 is immersed directly in the reservoir and therefore in a large quantity of dielectric fluid. Thermal management devices are designed to be able to manage the temperature of an electrical element under extreme conditions. However, not all parts of an electrical element have the same thermal requirement. Depending on the type of electrical element, the person skilled in the art is easily able to determine which will be the hot spots during the operation of said electrical element requiring significant cooling, the points requiring less significant cooling and, if necessary, the points cold that need to be warmed up. The thermal management device according to the invention makes it possible to regulate different zones of an electrical element according to different thermal management techniques and thus makes it possible to adapt the heat extraction capacity according to need. The invention makes it possible to improve the uniformity of the temperature within the same electrical element.

Advantageously, the emerging part is the part giving off the most heat in operation, such as, for example, the connectors of an electrical energy storage element during a charging phase.

For example, in the case of battery cells, in the charging phase, the terminals of said cells and the parts remote from said terminals do not give off the same heat and therefore do not have the same cooling needs. Consequently, when the entire heat treatment device is sized to cool the hottest part, namely the connectors for the cells, the parts giving off the least heat will be overcooled, which can lead to a temperature difference within the same electrical element too high which could cause damage to said element, or an extension of the charging time. In addition, this also leads to the use of too much fluid and therefore excess weight and unjustified additional cost of the device.

The invention makes it possible in particular to optimize the size by focusing on the cooling of the battery cell zones requiring the greatest cooling.

The cooling device advantageously comprises any one at least of the following characteristics, taken alone or in combination:

- the receiving box further comprises a cover intended to close the first tray,

- the first tank containing a dielectric fluid,

- the level of fluid within the reservoir, once an electrical element has been assembled in the housing of the device, is greater than the second height h2, thus, once the device has been assembled with an electrical element, said element is immersed in the dielectric fluid at least at the level of the tank,

- the first tank comprises a bottom and side walls extending from said bottom,

- the side walls include a rim over the entire periphery of the first tank,

- the rim comprises an upper face and a lower face,

- the cover is in sealed contact with the first container on the upper face of the rim,

- the rim carrying the fixing means between the cover and the first tray,

- the rim is inclined with respect to the side walls,

- the rim extends in a plane parallel to the bottom of the first tank

- the first container and the cover are assembled peripherally by fastening means, preferably by screwing means, advantageously with the interposition of a sealing element between the first container and the cover, the cover is thus fixed at least on the side walls of the first container, thus making it possible to form a compartment that is hermetic to the external environment,

- the first tray comprises a wall comprising an internal face intended to be at least partially facing an electrical element and an external face opposite the internal face.

- the housing is formed by a local protuberance of the bottom of the first tray, advantageously the bottom of the first tray extends at least partially in a transverse plane and the housing is a local deformation of said font in a vertical direction.

- the protrusion is arranged to correspond to the external face of the electrical element, it is understood by “correspond to the external face” that the internal face of the housing has at least partially a complementarity of shape with the external face of the electrical element , with or without space between the internal face of the housing and the external face of the electrical element, thus, the person skilled in the art can easily adapt the housing according to the type of electrical element to be thermally regulated so as to minimize the quantity required in dielectric fluid contained in the first tank,

- the wall of the first tray at the level of the housing is arranged so as to be in thermal interaction with the electrical element once mounted in said housing,

- the internal face of the housing is arranged so as to be spaced from the external face of the electrical element, once assembled, by a distance of between 0.1 and 3. This distance, also called assembly clearance, facilitates assembly and makes it possible to anticipate the thermal expansion of the electrical element during its heating. Thus, the dielectric fluid present in the housing is minimized, and the total amount of dielectric fluid required in the device is optimized,

- the internal face of the housing is intended to be spaced from the external face of the electrical element by an average distance of between 0 and 30 mm, advantageously between 2 and 10 mm, in this embodiment, the dielectric fluid of the reservoir fills the space available between the internal face of the housing and the external face of the electrical element, the heat exchange between the electrical element and the wall of the housing is greatly improved,

- the housing comprises a mouth for connection to the reservoir, the mouth being intended to form a passage for the electrical element and/or dielectric fluid between the housing and the reservoir,

- the third height h3 is lower than the first height h1,

- the second height h2 is lower than the height h3,

- the tank is intended to receive the part that releases the most heat in operation of the electrical element, called the hot spot, and the housing is intended to receive at least partially a part that releases less heat,

- the receiver box comprises a thermal management device arranged to regulate the temperature of the dielectric fluid,

- the thermal management unit comprising at least one duct in which a second heat transfer fluid distinct from the dielectric fluid can circulate, the second heat transfer fluid can be for example a refrigerant fluid (of the 1234yf, R134a, R744 type, etc.), by example of a vehicle air conditioning loop, or glycol water,

- the thermal management device comprises an inlet orifice and a coolant fluid outlet orifice, the inlet orifice communicates with the duct so as to supply said duct with coolant fluid and the outlet orifice communicates with the conduit so as to evacuate the heat transfer fluid from said conduit,

- the thermal management member at least partially forms the lid,

- the thermal management member comprises a thermal management plate formed of two plate portions, at least one of which has embossments so as to delimit at least one circulation channel for the second heat transfer fluid,

- the thermal management device is arranged so as to be able to selectively cool or heat an electrical element,

- the thermal management device is connected via the inlet orifice and the outlet orifice to a circuit in which the second heat transfer fluid circulates, the second heat transfer fluid circulating in the duct of the management device is advantageously of the glycol water type or equivalent, said circuit comprising a device for cooling and a device for heating said second heat transfer fluid,

- the thermal management device comprises a heating element in thermal interaction with the dielectric fluid,

- the dielectric fluid is chosen to have a phase change temperature in the optimum operating temperature range of the electrical element, advantageously, the dielectric fluid is chosen to have a boiling point such that the fluid vaporizes on contact of the electrical element when the latter is at a temperature higher than a chosen operating point,

- the thermal management device is configured in such a way as to liquefy the dielectric fluid having evaporated in contact with an electrical element,

- the thermal management device is arranged so as to always be at least partially immersed in the dielectric fluid,

- the receiver box further comprises a positioning element comprising an opening facing the housing, said positioning element being arranged so as to hold the electrical element in position in the housing, the positioning element can incidentally be arranged to so as to ensure the seal between the reservoir and the housings once the electrical element has been placed in said housing, the opening facing the housing can be calibrated so as to match the shape of the external face of an electrical element ,

- the thermal management device further comprises a second tank assembled peripherally to the first tank, the second tank forming, together with a part of the external face of the first tank, a compartment suitable for the circulation of a third heat transfer fluid,

- the second tray is assembled to the first tray on the underside of the rim,

- the thermal management device is arranged so that the third fluid is in thermal interaction with the part of the electrical element present within the housing,

- the third heat transfer fluid can be, for example, air, a refrigerant fluid (type 1234yf, R134a, R744, etc.), for example from an air conditioning loop of a vehicle, or glycol water .

- the third heat transfer fluid is air, in this embodiment, the complete weight and cost of the device is reduced,

- the second tank comprises a fluid inlet opening, and a fluid discharge opening,

- the fluid inlet opening of the second tank is fluidically connected to an air delivery duct,

- the air delivery duct being fluidly connected either to a ventilation, heating and/or air conditioning device, for example of the passenger compartment of a vehicle, or to a dedicated ventilation, heating and/or air conditioning system, either directly to the ambient air,

- the fluid inlet opening of the second tank is intended to be fluidically connected, directly or indirectly, to the passenger compartment of a vehicle,

- the fluid inlet and outlet openings of the second tank are intended to be connected to a vehicle coolant circuit,

- the first tank includes an opening, which can allow the addition of an evacuation valve intended to open if the pressure inside the reception box exceeds a certain threshold,

- the first tank comprises an opening, advantageously at least two openings, allowing the connection of the reservoir with a dielectric fluid circuit external to the receiver box,

- the first tray is made at least partially of thermally conductive materials, in particular metal of the aluminum or steel type, advantageously at the level of the housing, thus, the cooling of the housings passively, by the surrounding air, or active, by the circulation of a third fluid, is possible,

- the second tray is made of an insulating material, advantageously of plastic material, in particular of thermoplastic material such as for example polypropylene, polyamide, polyester, etc. which may or may not be loaded with additives and/or fibers, such as glass fibers, carbon fibers, and may or may not include a reinforcing grid,

the first and second trays are made of the same material, in particular of metal of the aluminum or steel type or of plastic material, in particular of thermoplastic material such as for example polypropylene, polyamide, polyester, etc. which may or may not be loaded with additives and/or fibers, such as glass fibers, carbon fibers, and may or may not include a reinforcing grid,

- the first tray comprises a plurality of housings each arranged to receive an electrical element,

- the first tray comprises a housing arranged to receive a plurality of electrical elements,

- the thermal management device is arranged in such a way that once assembled with an electrical element, the volume of fluid in the reservoir is strictly greater than the volume of fluid in the housing,

- the thermal management device further comprises a ventilation, heating and/or air conditioning system dedicated to said thermal management device and connected at least to the fluid inlet opening of the second tank,

- the cross section T of the tank is defined by the surface of said section delimited by the internal face of the wall of the tank at the level of the tank,

- the cross section t of the housing is defined by the surface of said section delimited by the internal face of the wall of the tank at the level of the housing,

- in an embodiment of the invention in which the tank and/or the housing do not have a regular shape, and therefore have cross-sections of different surfaces depending on the section planes parallel to the Oxz plane, the cross-sections of the tank and housing compared should be the most important surface cross-sections, i.e. the tank cross-section Tmax and the housing cross-section tmax.

The invention also relates to an assembly comprising a thermal management device as described according to one of the embodiments above, and at least one electrical element capable of releasing heat during its operation.

The features, variants and different embodiments of the invention may be associated with each other, in various combinations, insofar as they are not incompatible or exclusive of each other. In particular, variants of the invention may be imagined comprising only a selection of characteristics described below in isolation from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention from to the state of the prior art.

Other characteristics and advantages of the invention will become apparent through the description which follows on the one hand, and several embodiments given by way of indication and not limiting with reference to the appended diagrammatic drawings on the other hand, on which :

schematically illustrates a view according to a vertical section of a thermal management device according to one of the embodiments of the invention,

schematically illustrates a view according to a vertical section of a thermal management device according to one of the embodiments of the invention,

schematically illustrates in so-called exploded view, the thermal management device according to the embodiment of the invention shown in Figure 2,

schematically illustrates in sectional view the thermal management device according to one embodiment of the invention.

In the figures, the elements common to several figures retain the same reference.

FIG. 1 shows in an Oxy reference, a thermal management device 1 for an electrical element 2 capable of releasing heat in operation, comprising a reception box 11 for said at least one electrical element 2, said reception box 11 comprising a first tray 6 arranged so as to present:

a housing 3 arranged to receive an electrical element 2, this housing 3 extending over a first height h1 less than the total height H of the first tray, so that the electrical element once mounted in the housing extends outside said housing 3 over a second height h2 of the electrical element 2, said housing having a cross section t,

a reservoir 4 containing a dielectric fluid (whose level is not shown here) and having a third height h3, said reservoir communicating with housing 3 so that electrical element 2 can extend into said reservoir 4 on the second height h2,

the tank 4 having a cross section T greater than the cross section t of the housing 3.

The first tray 6 comprises a bottom 12 and side walls 122 extending from said bottom. The box 11 further comprises a cover 5 intended to close the first container 6 and thus form a compartment sealed against the external environment. The side walls 122 comprise a rim 123 over the entire periphery of the first tray 6 intended to carry fixing means 7, and to serve as a contact zone between the first tray 6 and the cover 5. Said rim 123 is inclined by relative to the side walls 122, advantageously the flange extends in a plane parallel to the bottom. The fastening means 7 may consist of openings, threaded or not, intended to receive a bolt, also called a screw/nut system, or any other fastening means that a person skilled in the art considers suitable. Advantageously a sealing means, not shown here, for example a metal or elastomer seal, is interposed between the rim 123 and the cover 5.

The first tank has a wall 61 comprising an internal face 15 and an external face 14. The cross section T of the tank 4 is defined by the surface of said section delimited by the internal face(s) 15 of the tank. 6 at the level of the tank 4 and the cross section t of the housing 3 is defined by the surface of said section delimited by the internal face(s) 15 of the tank 6 at the level of the housing 3.

Each housing 3 has a bottom wall 32 and side walls 31. The side walls 31 provide the connection between the bottom 12 of the first tray 6 and the bottom wall 32 of the housing 3. According to the embodiment shown in Figure 1, the first tray is made in one piece. According to an embodiment not shown, the tank and the housing or housings are separate parts assembled together in a sealed manner which may or may not be of the same material.

The first tank 12 comprises mouths 13 for connection to the reservoir 4, the mouth 13 being intended to form a passage for the electrical element and/or dielectric fluid between the housing and the reservoir.

According to the embodiment of Figures 2 and 3, the thermal management device 1 further comprises a thermal management member forming at least partially the cover 5, said thermal management member 8 comprises:

a channel 9 in which a second heat transfer fluid of the glycol water or refrigerant type can circulate,

an inlet 20 and an outlet 21 for coolant fluid, said orifices 20, 21 communicating with channel 9.

The first tank 6 comprises two openings 19 which can allow the addition of an evacuation valve intended to open if the pressure inside the reception box 11 exceeds a certain threshold, or allowing the connection of the tank with a dielectric fluid circuit external to the receiving box 11.

In this embodiment, the cover 5 comprises a first plate 51 and a second plate 52. The plate 51 carrying the inlet 20 and outlet 21 orifices, and the second plate 52 carrying ribs, or stampings, making it possible to delimit the channel 9. Advantageously, the first and second plates are assembled together by brazing or welding, these plates can also be assembled by screwing together with the first tray 6, in particular with the interposition of a sealing element between the first and second plates.

The receiver box 11 further comprises a positioning element 25 comprising openings 26 intended for the passage of the electrical elements 3.

The thermal management device 1 further comprises a second tray 16 assembled peripherally to the first tray 6. In this embodiment, the second tray 16 is assembled on the periphery of the bottom 12 of the first tray so that at least a part of the housings 3 is covered by the second tank 16. The second tank 16 forming together with a part of the outer face 14 of the first tank 6 a compartment suitable for the circulation of a third heat transfer fluid, in particular delimiting a circulation path of said third coolant.

The second tray 16 includes a fluid inlet opening 17, and a fluid discharge opening 18. These openings are intended to be connected to conduits for inlet and outlet of the third fluid, this embodiment lends itself particularly to the use of air as the third fluid. Thus the part of the electrical element present within the housing will be cooled by air. Indeed, the electric element by heating transfers energy to the wall of the housing and the wall of the housing transfers heat to the circulating air. The presence of the second tray 16 optimizes the air circulation path and avoids external disturbances as much as possible.

The first tray has a rim 123 comprising an upper face 125 and a lower face 124. The lid 5 is assembled in a sealed manner to the upper face 125 of the first tray 6.

In this embodiment, the first tray 6 is made at least partially of thermally conductive materials, in particular metal of the aluminum or steel type or even a ceramic-filled polymer, advantageously at least at the level of the housing 3 in order to improve the heat exchange between the third fluid and the electrical element through the wall 61.

In an embodiment not shown, the walls at the level of the housings are made of a conductive material while the walls at the level of the reservoir are made of an insulating material.

Figure 4 illustrates a thermal management device according to the invention. This is a top view of a section of the device made at the level of the tank according to a transverse plane Oxz.

The first tank has a wall 61 comprising an internal face 15 and an external face 14. The cross section T of the tank 4 is defined by the surface of said section delimited by the internal face 15 of the wall 61 of the tank 6 at the level of the tank. 4, and particularly as shown in Figure 4, at the section plane.

The cross section t of the housing 3 is defined by the surface of said section delimited by the internal face 15 of the wall 61 of the tray 6 at the level of the housing 3. The section t as represented in FIG. 4 is a projection on the plane of section of a cross section taken along a transverse plane at the level of the housing, said plane being parallel to the section plane.

The representations of FIGS. 1 to 4 are schematic. The present invention also covers different embodiments, in particular due to the shape of the housing and/or of the reservoir.

Claims (10)

Thermal management device (1) for an electrical element capable of releasing heat in operation (2), comprising a housing (11) for receiving said at least one electrical element (2), said receiving housing (11) comprising a first tray (6) arranged so as to present:

• a housing (3) arranged to receive an electrical element (2), this housing (3) extending over a first height (h1) less than the total height (H) of the first tray, so that the electrical element once mounted in the housing extends outside said housing (3) over a second height (h2) of the electrical element (2), said housing having a cross section (t),
• a reservoir (4) intended to contain a dielectric fluid and having a third height h3, said reservoir communicating with the housing so that the electrical element can extend into said reservoir over the second height (h2),

the reservoir having a cross section (T) larger than the cross section (t) of the housing (3). Thermal management device (1) according to the preceding claim, in which the casing (11) further comprises a cover (5) intended to close the first tray (6). Thermal management device (1) according to any one of the preceding claims, in which the housing (3) is formed by a local protrusion of the bottom (12) of the first tray (6). Thermal management device (1) according to the preceding claim, in which the protrusion is arranged to correspond to the outer wall of the electrical element capable of releasing heat in operation (2). Thermal management device (1) according to any one of the preceding claims, in which the receiving box (11) comprises a thermal management member (8) arranged to regulate the temperature of the dielectric fluid. Thermal management device (1) according to the preceding claim, in which the thermal management member (8) at least partially forms the cover (5), the said thermal management member (8) comprising at least one channel (9) in which can circulate a second heat transfer fluid distinct from the dielectric fluid. A thermal management device (1) according to any preceding claim wherein the receiver box comprises a plurality of housings. Thermal management device (1) according to any one of the preceding claims, further comprising a second tray (16) assembled peripherally to the first tray (6), the second tray (16) forming together with a part of the external face ( 14) of the first tank (6) a compartment capable of circulating a third heat transfer fluid. Thermal management device (1) according to the preceding claim, in which the second tank (16) comprises a fluid inlet opening (17), and a fluid outlet opening (18). Assembly comprising a thermal management device (1) according to any one of the preceding claims and at least one electrical element (2) capable of releasing heat during its operation.