Heat exchangers for temperature control of vehicle batteries

Abstract

Heat exchanger (1) for tempering and holding battery units of the battery of a motor vehicle, comprising - flat tubes (2) through which a heat transfer medium can flow, and - a collecting pipe (3) and a distributor pipe (4) for conducting the heat transfer medium, wherein - the flat tubes (2) are designed as multi-channel flat tubes (2) and - the collecting pipe (3) and the distributor pipe (4) are connected to one another via the flat pipes (2) in such a way that a holding frame is formed, wherein the holding frame provides a structure forming intermediate spaces and the intermediate spaces are provided as chambers (5) for receiving the battery units, wherein the holding frame is designed as a one-piece structure in such a way that the chambers (5) have a rectangular outline with long sides (12) and narrow sides (13) and are aligned in a row with one another, characterized in that - the multi-channel flat tubes (2) are aligned horizontally, parallel to each other, with their narrow sides one above the other, so that the wide sides of the multi-channel flat tubes (2) are each arranged in vertical planes, and - the collecting pipe (3) and the distribution pipe (4) are aligned vertically, with the connections for the discharge line on the collecting pipe (3) and for the supply line on the distribution pipe (4) being provided at the lower end of the pipe.

Description

[0001] The invention relates to a heat exchanger for tempering and holding battery units in a motor vehicle, in particular a hybrid or electric vehicle.

[0002] The large-capacity batteries used in electric or hybrid vehicles are used to store electrical energy. In electric vehicles, the energy is supplied to the battery by connecting it to a power source. In hybrid vehicles, energy can also be recovered during the vehicle's braking.

[0003] During operation—that is, when charging or discharging, or when the stored energy is extracted from the battery—heat is released. Batteries have an optimal operating temperature, so the resulting heat must be dissipated, as elevated operating temperatures place a significant thermal load on the battery cells and electronic components. Furthermore, very strict requirements exist regarding a small temperature spread between individual battery cells.

[0004] Cooling the battery, which is considered a heat source, increases its service life and should be done in such a way that the temperatures of the cooled battery only vary within a limited range and the temperature differences between individual cells are as small as possible.

[0005] Integrating a battery cooling system into the cooling system of the combustion engine in hybrid vehicles is not possible due to the excessively high temperatures within the engine cooling system, which can reach up to 100°C. The highest temperatures within the battery, however, should not exceed 40°C to 60°C, depending on the battery type. For this reason, the use of an additional cooling system is necessary.

[0006] It is known to cool the batteries used in electric or hybrid vehicles with ambient air. However, on a hot summer day, the outside air temperature can reach or exceed 40°C, making cooling with untreated ambient or outside air impossible. On the one hand, it is conceivable to reduce the battery's power output under these outdoor conditions to limit the heat generated. However, the disadvantage is that the battery cannot deliver its maximum power.

[0007] On the other hand, it is possible to take the cooling air either from the environment or from the air-conditioned passenger compartment and to pass it through the battery, cooled by the vehicle's air conditioning system.

[0008] Although the use of cooling air from inside the passenger compartment allows for a narrower temperature range than using ambient air, the extraction of passenger compartment air increases noise in the vehicle and thus reduces comfort. Furthermore, cooling the batteries with air can result in a large temperature difference between the individual battery cells. To reduce the temperature difference, a very large air mass flow is required. In addition to the aforementioned high flow noise and the ambient-dependent cooling performance, the use of an air cooling system also results in the significant space required for the air duct and the necessary fans.

[0009] In addition to cooling the battery using air cooled by the vehicle's air conditioning system, other methods are known for connecting the battery cooling system to the vehicle's air conditioning system. One option is to cool the battery directly with coolant, and the other is to use a secondary circuit of the air conditioning system. With direct cooling, the heat exchanger is pressurized with coolant to absorb the heat generated within the battery. With cooling using a secondary circuit, the heat absorbed in the battery's heat exchanger could be dissipated to the vehicle's air conditioning system in a second heat exchanger. Water or glycol, for example, can be used as a circulating heat transfer medium.

[0010] DE 10 2006 004 419 A1 proposes a cooling structure that has a cooling water circuit for cooling the heat-generating elements. The cooling water circuit is connected to the engine cooling water circuit, for example, of a hybrid vehicle. The closed water circuit and a refrigerant circuit of the vehicle's air conditioning system are thermally coupled via a water / refrigerant heat exchanger. The heat absorbed in the water circuit as a secondary circuit is transferred to the refrigerant circuit in the water / refrigerant heat exchanger.

[0011] DE 10 2006 004 419 A1 also discloses a heat exchanger for absorbing the heat generated within the battery. The plate-shaped heat-generating elements are arranged in a plate thickness direction so that predetermined distances between them form fluid channels. The heat-generating elements are permanently integrated into the heat exchanger, which, with its large flow cross-sections on the heat transfer medium side, has a disadvantageously large installation space in its external dimensions. Due to the transfer of sensible heat, a large mass flow of the heat transfer medium is also necessary, depending on the heat output to be dissipated.

[0012] Various other devices and systems are proposed in the prior art as heat exchangers for absorbing the heat generated within the battery.

[0013] DE 198 49 491 C1 discloses an electrochemical energy storage device comprising a heat exchanger structure for controlling the temperature of the storage cells. The heat exchanger structure has two supply channels running on opposite sides of the storage cell arrangement and two corresponding return channels on the opposite side. Flow flows through the associated parallel channels in opposite directions. The heat exchanger channels, designed as tubular elements with a rectangular cross-section, also serve to support the storage cells. Their shape ensures good, flat contact between the channels and the cuboid-shaped storage cells. Air, water, or a similar liquid coolant are used as the temperature control medium.

[0014] DE 10 2007 044 461 A1 discloses a heat exchanger unit designed as a waveguide cooler for an electrochemical energy storage device, which has flow channels through which a temperature control medium can flow. The channels are each provided at their ends with supply or collecting flow distribution or return collection channels, which are arranged opposite one another and have a rectangular flow cross-section. The flow channels are designed to be wave-shaped in the flow direction for better adaptation to round storage cells. A gaseous medium, such as air, or a liquid medium, such as water, is used as the temperature control medium.

[0015] DE 10 2008 032 086 A1 discloses a drive battery assembly for an electric, fuel cell, or hybrid vehicle. The drive battery assembly comprises a plurality of battery cells, each enclosed to the outside by its own cell housing and combined to form a cell pack, and at least one cooling fin that lies flat against the cell housing. The cooling fin is double-walled at least in sections and has walls spaced apart in sections. The spaced-apart region forms a channel carrying cooling fluid to dissipate thermal energy from the battery cells.

[0016] DE 602 13 474 T2 describes an electrochemical storage unit with a plurality of electrochemical cells. The cells are arranged at a distance from one another, with each of the cells having opposing first and second flat surfaces, first and second side surfaces, and first and second end surfaces. The cells are subject to volume changes during the charge and discharge cycle. The storage unit also has a cooling bellows made of a deformable, thermally conductive material. The cooling bellows forms a serpentine arrangement to contact the respective first and second flat surfaces of each of the cells, as well as the alternating first and second end surfaces of adjacent electrochemical cells during volume changes.

[0017] DE 10 2004 005 394 A1 discloses an electrochemical energy storage device with heat exchanger units and a plurality of electrochemical storage cells, each arranged side by side in at least two adjacent rows. The storage cells are each arranged between a heat exchanger unit. The heat exchanger units, which have channels through which a temperature control medium flows, are designed with the storage cells arranged between them as a self-supporting unit that can be inserted into a battery box.

[0018] State-of-the-art heat exchangers for cooling storage cells in a battery, particularly a vehicle battery, have large flow cross-sections on the heat transfer medium side due to their operation with air or water. This requires a disadvantageously large installation space for the heat exchanger and thus for the storage device. In addition, the transfer of sensible heat requires a very large mass flow of the heat transfer medium, depending on the heat output to be dissipated. Due to the increase in temperature in the flow direction of the heat transfer medium within the heat exchanger, a uniform temperature distribution within the storage cells cannot be ensured. Large temperature differences between the individual battery or storage cells, in turn, have a negative impact on the service life of the cells.

[0019] The object of the present invention is to realize a compact heat exchanger unit for controlling the temperature of a battery consisting of storage cells in a motor vehicle, in particular a hybrid or electric vehicle, which has a minimal installation space while providing high cooling performance and ensuring a very homogeneous temperature distribution within the battery with minimal noise generation. The assembly-related effort during installation in the vehicle must also be minimized.

[0020] This object is achieved by a heat exchanger according to the invention with the features of claim 1, which is intended for temperature control and for supporting electrochemical energy storage devices. The electrochemical energy storage devices are referred to below as battery units. The electrochemical energy storage device can, in particular, be Ni / MeH or Li-ion cells. Several cells are connected to form a battery unit, which in turn, together form the battery.

[0021] The heat exchanger has flat tubes through which a heat transfer medium can flow, as well as header tubes and distributor tubes for conducting the heat transfer medium. The flat tubes are designed as multi-channel flat tubes. The header tubes, distributor tubes, and flat tubes together form a vertically aligned holding frame whose structure creates intermediate spaces. The advantageously cuboid-shaped intermediate spaces are provided as chambers for directly accommodating the battery units. The heat transfer medium that absorbs or releases the heat is guided through the flat tubes arranged between the battery units. The chambers are preferably closed on the underside in the horizontal plane and open at the top. Alternatively, the chambers can also be open on the underside. The openings in the vertical direction enable the battery units to be inserted or installed within the heat exchanger forming the intermediate spaces.

[0022] The use of multi-channel flat tubes in conjunction with the header and distributor pipes advantageously results in a very compact heat exchanger unit with minimal installation space requirements.

[0023] The support frame, formed by the tubes as a one-piece structure, has chambers with a rectangular footprint characterized by long and narrow sides. The heat exchanger forms a functional unit consisting of a support frame for positioning and securing the battery units in the vehicle and a heat exchanger for dissipating waste heat to achieve the optimal operating temperature of the battery units. This combination results in a reduction in space and installation space while maintaining optimal heat transfer conditions.

[0024] The chambers are aligned in a row as intermediate spaces in the support frame, i.e., the chambers are arranged adjacent to one another in one spatial direction of the horizontal plane. According to an advantageous embodiment of the invention, several rows of chambers are arranged adjacent to one another in the second spatial direction of the horizontal plane.

[0025] According to the concept of the invention, the walls of the intermediate spaces are formed from multi-channel flat tubes, with the flat tubes arranged horizontally, parallel, and with the narrow sides facing each other. The wide sides of the flat tubes each form the vertical walls of the chambers, i.e., the wide sides are each arranged in vertical planes.

[0026] According to the invention, the header pipe and the distributor pipe are vertically aligned. The connections for discharging the heat transfer fluid from the header pipe and for supplying the heat transfer fluid to the distributor pipe are located at the lower end of the pipe.

[0027] The chambers of the heat exchanger, designed as a support frame, are preferably closed around their perimeter. This means that the battery units arranged in the chambers are completely enclosed by the heat exchanger. The heat transfer medium flows along all four vertical sides of the battery units and can dissipate the heat generated in the units.

[0028] According to a particularly advantageous embodiment of the invention, different multi-channel flat tubes have different flow cross-sections, while the external dimensions and external geometries of the flat tubes are identical. This allows heat exchangers with identical external shape and dimensions, but with flow cross-sections adapted to the respective heat transfer medium, to be used inside the multi-channel flat tubes. Battery units that are identical in shape, dimensions, and arrangement can thus be temperature-controlled by systems with heat exchangers operating with different heat transfer media.

[0029] According to an alternative embodiment, the heat exchanger is constructed from multi-channel flat tubes with different flow cross-sections but with the same external geometries and dimensions. This allows the heat exchanger to optionally be supplied with different heat transfer media and can be switched to a different heat transfer medium without further adjustments to other components within the battery units. The internal divisions and the connecting pieces of the header and distributor pipes are adapted to the internal flow cross-sections matched to the heat transfer medium properties. In their vertical arrangement, the multi-channel flat tubes can preferably be alternately flowed through by the different heat transfer media. For example, if a heat exchanger is designed for two different heat transfer media I and II, the multi-channel flat tubes supplied with heat transfer media I are arranged directly next to the multi-channel flat tubes supplied with heat transfer media II.However, since the heat exchanger is flowed through by either heat transfer medium I or II, the other flat tubes are not exposed to heat and therefore serve only as a support and heat conducting element for the battery units and walls of the heat exchanger.

[0030] The walls are also advantageously formed with heat conducting plates. The multi-channel flat tubes are mechanically and thermally connected to each other vertically along the long sides of the chambers by means of heat conducting plates. The heat conduction between the flat tubes ensures a uniform temperature on the surface of the heat exchanger.

[0031] In addition, the chambers for accommodating the battery units are segmented by heat-conducting plates. The inner surfaces of the chambers have a flat and smooth surface formed by the heat-conducting plates, allowing the battery units to be easily installed in the gaps or chambers of the heat exchanger. The heat-conducting plates thus serve not only to provide a heat-conducting connection between the flat tubes, but also to provide contact surfaces for heat transfer with the battery units.

[0032] The heat conducting plates are preferably soldered, glued or clamped onto the multi-channel flat tubes.

[0033] According to a preferred embodiment of the invention, the multi-channel flat tubes are deformable at the narrow sides of the chambers, i.e., the narrow sides of the chambers are variable in length. This advantageously allows the chambers to be flexibly formed in the horizontal spatial directions. This deformability enables easier assembly of the battery units inside the chambers due to the bending. Subsequent pressing also ensures good heat transfer between the heat exchanger and the battery units. Furthermore, this deformability has the particular advantage that spatial expansion of the battery units due to thermal stress during operation can be compensated.

[0034] Alternatively, the multi-channel flat tubes, starting from a rectangular arrangement opposite the long sides of the chambers, are curved outward in the longitudinal direction of the chambers. The curvatures or deformations of the multi-channel flat tubes in the longitudinal direction of the chambers shorten the narrow sides and bring the long sides of the chambers closer together. The deformability of the flat tubes in the horizontal spatial directions has the aforementioned advantage of simplifying the assembly of the battery units and compensating for spatial expansion of the battery units due to thermal stress during operation.

[0035] According to a preferred embodiment, the heat exchanger is designed as a refrigerant evaporator. Direct refrigerant cooling advantageously allows for the realization of a very compact unit consisting of the battery or battery units and the heat exchanger for controlling the temperature of the battery units. Direct refrigerant cooling also has the advantage that the heat exchanger can be connected directly to the refrigerant circuit of the vehicle's air conditioning system.

[0036] When refrigerant evaporates, a very homogeneous temperature distribution is achieved within the battery due to an almost constant temperature during evaporation.

[0037] Preferred refrigerants as phase-change heat transfer media are carbon dioxide (R744), R134a, or HFO1234yf. However, the heat exchanger can also be supplied with a liquid, single-phase coolant, such as glycol. The flow cross-sections of the multi-channel flat tubes must be adapted depending on the heat transfer media used.

[0038] Since the flat tubes are in direct contact with the battery units, the heat to be dissipated is conducted from the battery units into the refrigerant or coolant.

[0039] A further advantage is that the manifold and distributor pipes connected via the multi-channel flat tubes are designed in such a way that the mass flow of the heat transfer medium can be divided into partial flows among the multi-channel flat tubes. All partial flows flow through the multi-channel flat tubes in parallel in one direction.

[0040] Alternatively, the mass flow of the heat transfer medium can be divided into partial flows on the multi-channel flat tubes, whereby the partial flows preferably flow through the multi-channel flat tubes in parallel in one direction and, after deflection in the collecting pipe and / or distributor pipe, flow through adjacently arranged multi-channel flat tubes in counterflow.

[0041] The selectable distribution and direction of the refrigerant mass flow in countercurrent has the advantage that a highly heated multi-channel flat tube is arranged next to a flat tube through which heat transfer medium flows in the inlet state, i.e. at a significantly lower temperature, thus enabling a better uniformity of the temperature within the battery units.

[0042] According to a further preferred embodiment of the invention, bracing frames with bracing struts for bracing the battery units are provided within the chambers of the heat exchanger. This ensures sufficient heat transfer between the battery units and the walls of the heat exchanger chambers, in particular the heat conducting plates. The bracing struts extending between the battery units are advantageously designed such that they are stretched in a defined manner during bracing, thus ensuring a certain prestress to brace the side walls of the bracing frames and thus the walls of the heat exchanger chambers. By means of the prestress, the contact force required for heat conduction is maintained when the battery units change size.The bracing struts are designed according to their tensile strength and cross-section to ensure minimal tension under all operating conditions and a maximum tension is not exceeded. Alternatively, the bracing struts can be dimensioned larger so that no significant stretching of the bracing struts occurs under any operating condition. If the bracing struts are dimensioned larger, spring elements are provided to preload the bracing frame.

[0043] According to an alternative design, the clamping forces are applied by the bracing frame. When assembling the bracing frame with bracing struts, the non-stretchable bracing struts are tightened, and the clamping forces are transferred to the bracing frame. The preload is ensured by the stretchable bracing frame. By shortening the bracing struts, the bracing frame is deformed in a defined manner during assembly, so that the side walls of the bracing frame or the walls of the heat exchanger chambers are braced.

[0044] The bracing frames and bracing struts can be made of metal or plastic.

[0045] This description refers to the upright version of the heat exchanger, in which the chambers are open upwards, i.e., vertically. Alternatively, the heat exchanger can also be designed horizontally. In the horizontal version, the chambers are open laterally, i.e., horizontally. The references to "horizontal" and "vertical" refer primarily to the following explanations of the figures. The terms "horizontal" and "vertical" therefore merely indicate a relative direction and are not used in a restrictive manner.

[0046] In summary, the main advantage of the heat exchanger is its compactness, i.e. high cooling capacity with minimal installation space.

[0047] Further advantages of the heat exchanger compared to the state of the art can be summarized as follows: - minimal noise, - minimal assembly effort due to the intended assembly play, - very homogeneous temperature distribution due to good heat transfer, - Uniformity of the temperature on the surface of the heat exchanger by heat conducting plates, - flow cross-sections of the multi-channel flat tubes adapted to the respective heat transfer medium with the same external dimensions and geometries of the flat tubes, - flexible deformability in horizontal spatial directions, so that spatial expansions due to thermal stress can be compensated, and - Training as a refrigerant evaporator with direct connection to the refrigerant circuit of the vehicle air conditioning system.

[0048] Further details, features, and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. They show: Fig. 1: Heat exchanger with chambers for accommodating battery units, Fig. 2: Temperature equalization between the multi-channel flat tubes by heat conduction, Fig. 3: Cross-section of the multi-channel flat tubes with the same outer geometries, but different flow cross-sections of the channels for different fluids, Fig. 4: Deformation of the heat exchanger and Fig. 5: Heat exchanger with bracing frame and bracing struts.

[0049] In Fig. Figure 1 shows the heat exchanger 1 with chambers 5 for accommodating battery units, which are cooled by the heat exchanger 1. The heat exchanger 1, through which a heat transfer medium flows, dissipates the heat generated during operation of the battery units, i.e., during charging or discharging, and thus ensures that the battery does not exceed a certain maximum temperature in order to extend its service life.

[0050] The heat transfer medium that dissipates heat from the battery flows through the flat tubes 2 arranged around the battery units, so that the heat-absorbing medium is guided directly between the adjacent battery units. The multi-channel flat tubes 2 are connected to one another. A distributor pipe 4 is provided for distributing the heat transfer medium into the individual cross-sections of the multi-channel flat tubes 2, and a collector pipe 3 is provided for merging the individual channels. Depending on the desired distribution and redirection of the heat transfer medium within the heat exchanger 1 or the multi-channel flat tubes 2, the internal volumes of the distributor pipe 4 and / or the collector pipe 3 have subdivided sections or are formed as a continuous area. The multi-channel flat tubes 2 are aligned horizontally, while the collector pipe 3 and the distributor pipe 4 are aligned vertically.The connections for discharging the heat transfer fluid from the header pipe 3 and for supplying the heat transfer fluid to the distributor pipe 4 are located at the lower end of the pipe. From a thermodynamic perspective, the connection to the header pipe 3 can also be advantageously located at the upper end of the pipe.

[0051] The heat exchanger 1 can be operated with a phase-changing medium, for example with the refrigerant of the refrigerant circuit of the vehicle's air conditioning system, or with a single-phase fluid, for example glycol. Since the battery cooler is also designed for operation at outside temperatures below 0 °C, at which the vehicle's air conditioning system for conditioning the passenger compartment may not be switched on, oil return from the heat exchanger 1 must be ensured; so-called oil traps must be avoided. The vertical arrangement of the collecting pipe 3 and distribution pipe 4 with connections located at the bottom, which serves in particular to guarantee the necessary oil supply under all operating conditions, ensures that no "reservoirs" for oil storage are created.

[0052] The rectangular walls of the chambers 5, designed to accommodate the battery units, are arranged in a grid-like structure, so that the battery units lie next to each other in the horizontal spatial directions X, Y. The multi-channel flat tubes 2 completely enclose a chamber 5, each of which has long sides 12 and narrow sides 13, so that the heat is dissipated from the vertical sides of each battery unit. The heat is preferentially transferred along the long sides 12.

[0053] For better heat conduction and thus distribution of the heat to be dissipated, the adjacent multi-channel flat tubes 2 are connected to one another on the long sides 12 of the chambers 5 with heat conducting plates 6. The heat conducting plates 6 are connected to the multi-channel flat tubes 2 by a material or form-fitting connection. The heat conducting plates 6 are glued or clamped onto the multi-channel flat tubes 2. In this case, the multi-channel flat tubes 2 are brazed to the header tubes 3 and distributor tubes 4, commonly also referred to as tanks, using an induction process, which advantageously significantly shortens the required brazing time. The heat conducting plates 6 can, however, also be brazed to the multi-channel flat tubes 2. The entire heat exchanger 1, consisting of header tubes 3 and distributor tubes 4, multi-channel flat tubes 2, and heat conducting plates 6, is then brazed as a pre-assembled unit in the brazing furnace with correspondingly high cycle times.

[0054] Because the heat conducting plates 6 are made of a very good heat conductor, such as copper or aluminum, the temperatures on the outside of the battery units are very evenly distributed. Any temperature differences that may occur due to processes within the battery units are well compensated. The heat conducting plates 6 applied to the multi-channel flat tubes 2 enable heat flow between the individual multi-channel flat tubes 2. A multi-channel flat tube 2 through which a lower-temperature heat transfer medium flows absorbs a greater heat flow than a flat tube 2 through which a warmer heat transfer medium flows. The heat conduction between the flat tubes 2 thus ensures an even temperature on the surface of the battery units or of the heat exchanger 1.If, for example, the temperature in a flat tube 2 rises due to local overheating or a strongly heated heat transfer medium, the adjacent battery unit is cooled via heat conducting plates 6 by means of the nearest multi-channel flat tube 2.

[0055] The flow direction of the refrigerant mass flow can be freely selected in the design of the heat exchanger 1, so that two adjacent multi-channel flat tubes 2 are flowed through in countercurrent, wherein next to a strongly heated flat tube 2 there is one with the refrigerant or the coolant in the inlet state, i.e. with a lower temperature.

[0056] Out of Fig. 1 also shows that the vertically arranged heat conducting plates 6 not only create a beneficial thermal connection between the multi-channel flat tubes 2, but also segment the rectangular, grid-like chambers 5 for accommodating the battery units. Due to the closure of the gaps between the multi-channel flat tubes 2 and the flat surface of the heat conducting plates 6, the battery units can be easily installed in the chambers 5. Furthermore, the flat surface of the heat conducting plates 6 enables a closed, flat contact between the heat exchanger surface and the surface of the battery units, which ensures good heat conduction and thus efficient temperature control of the battery units.

[0057] Fig. Figure 2 illustrates the temperature equalization between the multi-channel flat tubes 2 through heat conduction within the heat conducting plates 6. The multi-channel flat tubes 2 are arranged on the heat conducting plate 6 at equal spacing from one another and are thermally coupled to it by soldering, gluing, clamping, or another suitable method. Alternatively, the multi-channel flat tubes 2 can also be arranged at alternating spacings or at spacings adapted to the installation space or other conditions. The heat equalization between the multi-channel flat tubes 2 is therefore based on heat conduction processes. The equalizing heat flows then run essentially in a vertical direction 10 between the multi-channel flat tubes 2.

[0058] The collecting pipe 3 and the distribution pipe 4, which are connected via the multi-channel flat pipes 2, are designed in such a way that the mass flow of the heat transfer medium can be divided into partial flows, wherein a partial flow flows through several multi-channel flat pipes 2 in parallel in one direction 11 and flows through adjacent multi-channel flat pipes 2 in counterflow.

[0059] On the other hand, the mass flow of the heat transfer medium can also flow through all multi-channel flat tubes 2 one after the other by being redirected within the header pipe 3 and distributor pipe 4 in such a way that, in this application, all adjacent multi-channel flat tubes 2 flow in countercurrent. Furthermore, it is possible to distribute the mass flow of the heat transfer medium evenly among the multi-channel flat tubes 2, so that the heat transfer medium does not flow back and forth between the distributor pipe 4 and the header pipe 3, but rather a constant flow of the heat transfer medium is realized.

[0060] In the Fig. 3a and Fig. Figure 3b shows cross-sections of multi-channel flat tubes 2 with identical external geometries and different flow cross-sections 9 of the channels. Using multi-channel flat tubes 2 with different flow cross-sections 9 while maintaining the same external geometry, the heat exchanger 1 is designed for use with different heat transfer media.

[0061] When using phase-changing, i.e., evaporating, refrigerant as the heat transfer medium, the flow cross-sections 9 of the multi-channel flat tubes 2 are adapted to the respective permissible pressure loss. The pressure loss within the flat tubes 2 is designed such that the permissible temperature spread of the battery is not exceeded. The flow cross-section 9 of a flat tube 2 per meter of flow length and kilowatt of heat output is in the range of 35 mm. 2 / (m·kW) up to 55 mm 2 / (m·kW).

[0062] For a single-phase coolant such as glycol, the flow cross-sections 9 must be designed to allow a sufficiently large mass flow, whereby the mass flow is determined by the heat output to be dissipated and the maximum permissible temperature spread of the battery. With a sufficiently large mass flow, a very small temperature spread can be achieved using glycol as the heat transfer medium.

[0063] In particular, however, a very homogeneous temperature distribution is achieved during the evaporation of refrigerant within the battery, since the temperature of the refrigerant depends solely on the pressure level. As the refrigerant flows along the flow path, the evaporation temperature drops due to pressure loss. When the refrigerant superheats at the evaporator outlet following the evaporation process, the temperature rises again. The pressure losses and superheat are adjusted to the permissible temperature spread of the battery.

[0064] By adapting the internal flow cross-sections 9 while maintaining the same external geometry, the heat exchanger 1 can be operated with different heat transfer fluids and can be converted to a different refrigerant or heat transfer fluid without adapting other components within the battery. In particular, the constant external dimensions of the flow-carrying components, such as the multi-channel flat tubes 2, the header pipe 3, and the distributor pipe 4, can be implemented for the refrigerants R134a, HFO1234yf, and R744, as well as for glycol. However, the flow cross-sections 9 must be adapted to the respective fluid.

[0065] Fig. Figure 4 shows a section of a chamber 5 of the heat exchanger 1, in which the deformable multi-channel flat tubes 2 arranged on the narrow side 13 are deformed as a composite. The webs in the flat tube 2 enable very strong bending of the flat tube 2 without closing the flow cross-sections 9. The multi-channel flat tubes 2 can be deformed before and / or after the brazing process.

[0066] The flat tubes 2, which are bulged outwards in relation to the rectangular arrangement or curved outwards in the longitudinal direction of the chambers 5, demonstrate that the heat exchanger 1 can be designed flexibly in the defined spatial directions X and Y. The degree to which the narrow side or chamber 5 is shortened in the spatial direction X increases the degree to which the flat tubes 2 bulge. The compression of the heat conducting plates 6 in the horizontal spatial direction X, i.e., the movement of the heat conducting plates 6 toward one another, thus reduces the distances between the heat conducting plates 6 during deformation V of the multi-channel flat tubes 2. The multi-channel flat tubes 2 are thereby moved outwards in the horizontal spatial direction Y relative to the chamber 5 and bent within a specific radius. The deformation of the multi-channel flat tubes 2 can take place in the elastic or plastic range and allows for flexible formability of the external dimensions of the chambers 5.The variable width of chamber 5 and thus the variable design of the outer dimensions of chamber 5 allows, within limited limits, the accommodation of battery units with slightly different outer dimensions while ensuring sufficient contact between the heat conducting plates 6 and the outer walls of the battery units. This ensures very good heat transfer between the battery units and the heat exchanger 1, as well as advantageous clearance for the assembly of the battery units within the chambers 5 of the heat exchanger 1. The chambers 5 of the heat exchanger 1, which are bent open for the assembly of the battery units - deformation V of the flat tubes 2 - are subsequently pressed onto the battery units to ensure good heat transfer. The bending of the chambers 5 can be up to 10% of the width of the chamber 5. With certain adaptations of the inner webs in the flat tube 2, the value of 10% can be increased even further.

[0067] In addition, possible expansions during operation of the battery units can be compensated for by ensuring sufficient surface contact between the heat conducting plates 6 and the battery units.

[0068] In Fig. Figure 5 shows the heat exchanger 1 with bracing frame 7 and bracing struts 8. To ensure sufficient heat transfer between the battery units and the heat exchanger 1, the heat exchanger 1 is braced to the battery units by means of bracing frame 7 and bracing struts 8, with the bracing struts 8 passing between the battery units. The battery units and the heat exchanger 1 thus form a composite assembly, in which the bracing frame is also designed with a bottom to close off the chambers 5 at the bottom.

[0069] The bracing frame 7 and the bracing struts 8 can be made of metal or plastic, for example. The bracing struts 8 are dimensioned such that they are stretched in a defined manner during bracing, thus ensuring prestressing of the heat exchanger 1. As a result of the prestressing, the contact force between the surfaces of the battery unit and the heat exchanger 1 is maintained even when the cells of the battery units change size. The cross-section and shape of the bracing struts 8 are designed based on their tensile strength to ensure minimal stress under all operating conditions and not exceed the maximum stress.

[0070] The bracing struts 8 can optionally also be dimensioned larger so that no significant stretching of the bracing struts 8 occurs, whereby the preload in this case is realized by spring elements, such as spring washers. List of reference symbols 1 heat exchanger 2 flat tubes / multi-channel flat tubes 3 Collecting pipe 4 distribution pipe 5 chamber 6 heat conducting plate 7 bracing frames 8 bracing strut 9 Flow cross-section 10 Direction of heat flow 11 Direction of mass flow 12 Long side 13 Narrow side V Deformation X, Y horizontal spatial direction

Claims

[1] Heat exchanger (1) for tempering and holding battery units of the battery of a motor vehicle, comprising - flat tubes (2) through which a heat transfer medium can flow, and - a collecting pipe (3) and a distributor pipe (4) for conducting the heat transfer medium, wherein - the flat tubes (2) are designed as multi-channel flat tubes (2) and - the collecting pipe (3) and the distributor pipe (4) are connected to one another via the flat pipes (2) in such a way that a holding frame is formed, wherein the holding frame provides a structure forming intermediate spaces and the intermediate spaces are provided as chambers (5) for receiving the battery units, wherein the holding frame is designed as a one-piece structure in such a way that the chambers (5) have a rectangular plan with long sides (12) and narrow sides (13) and are aligned in a row with one another, characterized by , that - the multi-channel flat tubes (2) are aligned horizontally, parallel to each other, with their narrow sides one above the other, so that the wide sides of the multi-channel flat tubes (2) are each arranged in vertical planes, and - the collecting pipe (3) and the distribution pipe (4) are aligned vertically, with the connections for the discharge line on the collecting pipe (3) and for the supply line on the distribution pipe (4) being provided at the lower end of the pipe. [2] Heat exchanger (1) according to claim 1, characterized by that the chambers (5) are closed at their periphery, so that the battery units arranged in the chambers (5) are completely enclosed by the heat exchanger (1). [3] Heat exchanger (1) according to claim 1 or 2, characterized bythat the multi-channel flat tubes (2) with different flow cross-sections (9) have the same external geometries, so that heat exchangers with the same external shape but flow cross-sections (9) adapted to a heat transfer medium in the multi-channel flat tube (2) can be used for the same applications. [4] Heat exchanger (1) according to claim 1 or 2, characterized by that the multi-channel flat tubes (2) with different flow cross-sections (9) have the same external geometries and a heat exchanger (1) is optionally provided for use with different heat transfer media, wherein the heat exchanger (1) is formed from multi-channel flat tubes (2) with different flow cross-sections (9). [5] Heat exchanger (1) according to one of claims 1 to 4, characterized bythat the multi-channel flat tubes (2) are mechanically and heat-conductingly connected to one another on the long sides (12) of the chambers (5) in the vertical direction by means of heat conducting plates (6), so that the chambers (5) for receiving the battery units are segmented by the heat conducting plates (6) and the inner surfaces of the chambers (5) have a flat and smooth surface formed by the heat conducting plates (6). [6] Heat exchanger (1) according to one of claims 1 to 5, characterized by that the multi-channel flat tubes (2) are deformable on the narrow sides (13) of the chambers (5) and thus the narrow sides (13) of the chambers (5) can be changed in length, so that the chambers (5) can be flexibly formed in the horizontal spatial directions (X, Y) and the expansion of the battery units due to thermal stress can be compensated. [7] Heat exchanger (1) according to claim 6, characterized bythat the multi-channel flat tubes (2), starting from the rectangular arrangement opposite the long sides (12) of the chambers (5), are deformed in an outwardly curved manner in the long direction of the chambers (5), so that the narrow sides (13) are shortened and the long sides (12) of the chambers (5) approach one another. [8] Heat exchanger (1) according to one of claims 1 to 7, characterized by that the heat exchanger (1) is designed as a refrigerant evaporator. [9] Heat exchanger (1) according to one of claims 1 to 8, characterized by that the collecting pipe (3) and the distributor pipe (4), which are connected via the multi-channel flat pipes (2), are designed such that the heat transfer mass flow can be divided into partial flows onto the multi-channel flat pipes (2), wherein all partial flows flow through the multi-channel flat pipes (2) in parallel in one direction. [10] Heat exchanger (1) according to one of claims 1 to 8, characterized bythat the collecting pipe (3) and the distributor pipe (4), which are connected via the multi-channel flat pipes (2), are designed such that the heat transfer mass flow can be divided into partial flows onto the multi-channel flat pipes (2), wherein the partial flows flow through the multi-channel flat pipes (2) in parallel in one direction and, after deflection into the collecting pipe (3) and / or distributor pipe (4), flow through adjacently arranged multi-channel flat pipes (2) in counterflow. [11] Heat exchanger (1) according to one of claims 1 to 10, characterized by that a bracing frame (7) with bracing struts (8) is provided for bracing the battery units within the chambers (5) of the heat exchanger (1). [12] Heat exchanger (1) according to claim 11, characterized by that the bracing struts (8) are guided between the battery units and brace the side walls of the bracing frames (7). [13] Heat exchanger (1) according to claim 11 or 12, characterized bythat the bracing struts (8) are designed in such a way that they are stretched during bracing and thus ensure a pre-tension in order to brace the side walls of the bracing frames (7) and thus the walls of the chambers (5) of the heat exchanger (1). [14] Heat exchanger (1) according to claim 11 or 12, characterized by that the bracing frame (7) is designed in such a way that it is deformed during bracing and thus ensures prestressing in order to brace the walls of the chambers (5) of the heat exchanger (1). [15] Heat exchanger (1) according to one of claims 11 to 14, characterized by that resilient elements are provided for pre-tensioning the bracing frame (7).

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