HEAT EXCHANGER FOR TRANSFERRING HEAT BETWEEN A COOLANT AND A RE-FRIGERANT IN A VEHICLE

CROSS-REFERENCE TO RELATED APPLICATION

[0001]This application claims priority to German Application No. DE 102024203741.9 filed on Apr. 22, 2024, which is incorporated herein by reference in its entirety for all purposes.

TECHNICAL FIELD

[0002]The invention relates to a heat exchanger for transferring heat between a coolant and a refrigerant, the heat exchanger comprising a heating device for heating the refrigerant and the coolant. In particular, the invention relates to such a heat exchanger for use in a heat management system of a completely or partially electrically driven vehicle.

BACKGROUND

[0003]In vehicles, in particular battery-powered electric motor vehicles (hybrid or fully electric), the complex thermal requirements mean that heat management systems may increasingly be used. Firstly, for example, the omission of internal combustion engines may make it necessary to provide an auxiliary heating means for heating the passenger compartment at low temperatures, the energy consumption of which, however is at the expense of the energy stored in the vehicle battery. Secondly, the demand for quick-charging capacity is also considerably increasing. DC quick-charging stations with a power of up to 350 KW are currently provided. In association therewith, the temperatures of the vehicle batteries have to be kept within a narrow range in order to be able to make optimum use of an available charging power. Depending on the current operating mode and external temperature, the vehicle batteries therefore have to be either cooled or heated. Even higher quick-charging capacities intensify the demands made on the heat management system. The heat management has the task of highly efficiently using the heat quantities or temperatures respectively assumed in the existing heat circuits in order to keep the consumption of power additionally to be fed in low and to maintain specified temperature ranges of the components, e.g. electric motor, vehicle battery and power electronics, etc., in order to ensure their efficiency and durability.

[0004]Such a heat management system often comprises a heat pump. The heat pump comprises in each case at least one high-voltage compressor, a condenser, an expansion valve, an evaporator and a suitable working fluid or refrigerant (e.g. R134a, R1234yf, R744, R290). In a known manner, heat from the environment or another fluid can be absorbed via the evaporator in the heating mode of such a heat pump.

[0005]A heat management system in which heat can be exchanged between different heat circuits is known from document DE 10 2016 214 623 A1. The heat circuits are each operated with a coolant. The corresponding heat exchange unit comprises a heat pump operated with refrigerant, with a heat exchanger for the transfer of heat to or from the one or the other of the heat circuits being available on the heat side (condenser) and on the cold side (evaporator). On the heat side or the cold side, a PTC element may be provided as an auxiliary heater within the throughflow region of the respective heat exchanger. The auxiliary heater can be activated as required if a temperature in the throughflow region is to be quickly increased, for example, when the heat management unit is started and/or at low ambient temperatures.

[0006]In document EP 3 739 276 B1, a heat exchanger is connected to a refrigerant line, which can be integrated in a fluid circuit, and to a coolant line, which is in heat exchange connection with a coolant and can be integrated in a further fluid circuit. A fluid-fluid heat exchanger is also involved here. The heat exchanger can be used in an air conditioning system for vehicles. The refrigerant line runs coaxially within the coolant line. The refrigerant line is provided in the low-pressure range of the corresponding fluid circuit with a compressor, condenser and an expansion member. An electrically operable heating element is located on the outside of the coolant line. The heating element has a heating wire wound around the coolant line or a heating foil, the surface of which lies around said line.

[0007]In the case of electrically powered vehicles, the vehicle battery, as described, may be cooled during operation or during quick charging, i.e. in a higher temperature range via a refrigeration system and a heat exchanger thermally integrated in the refrigeration system. A heat exchanger configured in such a way is also referred to as a chiller. It is used to transfer heat between the corresponding refrigerant circuit and the coolant circuit which interacts thermally with the vehicle battery. In particular, in this case, in the low-pressure range, refrigerant is evaporated in or in front of the chiller, with heat being able to be absorbed from the coolant in the chiller.

[0008]Document DE 10 2022 111 067 A1 discloses a heat exchanger, which is operated as such a chiller, for an at least partially electrically driven motor vehicle with a plurality of heat exchanger plates arranged next to or parallel to one another and having respective refrigerant lines and coolant lines fluidically separated from one another. The refrigerant lines are connected to a refrigerant circuit of a refrigeration system. The coolant lines are connected to a coolant circuit of a cooling system. The heat exchanger plates are designed to permit heat transfer from the refrigerant to the coolant or vice versa. It is provided that the heat exchanger has an electrical heating device, which can heat the refrigerant and the coolant simultaneously as required. The heating device may be of plate-like or cushion-like design and positioned in a sandwich-like manner between two adjacent heat exchanger plates. Alternatively, the heating device may be arranged laterally between a housing of the heat exchanger and the heat exchanger plates. In this case, the heating devices may be attached laterally to an inner wall of the housing or secured opposite to the edges of the heat exchanger plates, but in particular outside the heat exchanger plates. Furthermore, the heating device may also be integrated in a similar lateral position in the housing of the heat exchanger itself.

[0009]The chiller has the function of transferring heat from the coolant to the refrigerant when the temperatures are too low. In this case, passenger compartment heating is generally also desirable. Therefore, an approach to implementing an auxiliary heating means usually consists in primarily heating the coolant. In the case of a combination of chiller and auxiliary heating means, the refrigerant is heated (indirectly) by said auxiliary heating means as required.

SUMMARY

[0010]It is an object to provide a heat exchanger for transferring heat between a coolant and a refrigerant, preferably for use in a vehicle, in which the efficiency of the heat transfer function is further improved.

[0011]According to one aspect, a heat exchanger is proposed for transferring heat between a coolant and a refrigerant, preferably for use in a vehicle, in particular a motor vehicle. The proposed heat exchanger may be a component of a heat management system and be implemented in a completely or partially (hybrid) electrically powered vehicle. The heat exchanger can be designed as a chiller and can have a heating device for heating the refrigerant and the coolant.

[0012]The heat exchanger comprises a bottom wall forming an end-face end of a stack of at least two flow volumes through which the refrigerant or coolant flows. The flow volumes can be arranged in an alternating manner in the stack (or package) for the refrigerant and the coolant to flow through them. Other arrangements are also possible. Also, the numbers of flow volumes for the refrigerant and the flow volumes for the coolant in the stack may also differ instead of being identical. That the bottom wall forms an end-face end means that the stack or another stack with corresponding flow volumes does not extend beyond the bottom wall on the other side. As far as the throughflow with fluids is concerned, the bottom wall forms a closure or an end of the stack or package.

[0013]Adjacent to the bottom wall (in the stack direction) is a first flow volume for the refrigerant to flow through and which is connected to a first fluid inlet and to a first fluid outlet. These are designed to produce a connection to a refrigerant circuit, with the first flow volume additionally being defined by a first partition opposite the bottom wall. Preferably, the flow volume defined by the bottom wall and the partition has a flat design, with the bottom wall and the first partition being parallel to each other in their direction of extent at a small distance (or height) from each other in comparison to the dimensions of the bottom wall and partition. The refrigerant may be, for example, a known working fluid such as R134a, R1234yf, R744, R290, but the exemplary embodiments are not limited to these specific fluids. As described at the beginning, the refrigerant circuit may comprise, inter alia, for example, a compressor, a condenser, an expansion valve, an evaporator and other components, such as collectors, etc. Overall, the refrigerant circuit may be part of a heat pump.

[0014]Adjacent to the first partition is a second flow volume for the coolant to flow through and which is opposite the first flow volume. The first partition can therefore transfer heat from the coolant to the refrigerant and, as required, also vice versa, depending on the operating mode. The second flow volume is connected to a second fluid inlet and to a second fluid outlet, which are configured to produce a connection to a coolant circuit. The coolant circuit may, for example, provide heating or cooling of the passenger compartment, the vehicle battery or other components of the vehicle, such as the drive or other motors. For example, the coolant may be water or a similar suitable fluid with a comparatively high heat capacity.

[0015]The second fluid inlet and the second fluid outlet can each have connectors which are designed in a known manner, for example, as quick-action couplings and thus ensure a quick installation which is sufficiently reliable with respect to the fluid and is foolproof. This is in contrast to the first fluid inlet and the first fluid outlet, which, inter alia, for reasons of sustainability, require a higher degree of durability and tightness of the coupling and thus more complicated securing because the working fluid (refrigerant) must not be allowed to enter the environment and loss of same may lead to damage to the components. In this respect, the first flow volume and the second flow volume are each already defined just by the configuration of the fluid inlets and outlets for use with the fluids described.

[0016]In addition, the second flow volume has a basically similar flat structure and substantially the same dimensions as the first flow volume. However, the dimensions, in particular the height of the flow volumes in a direction perpendicular to the bottom wall, may be specifically entirely different. Preferably, the fluid inlets and outlets are each positioned diagonally to each other, and this is also true of the first flow volume. In the stack-shaped structure, the fluid inlets and outlets preferably extend in the vertical direction perpendicular to the bottom wall, and they optionally extend through adjacent flow volumes.

[0017]According to aspects according to the invention, it is now proposed, in such a structure of the heat exchanger, to arrange the heating device on the bottom wall on a side opposite the first flow volume. In other words, the heater is more or less directly thermally connected to the first flow volume through which the refrigerant flows. This means that, in an (optional) heating mode, heat is first transferred to the refrigerant. Subsequently or indirectly, heat is furthermore also transferred to the second flow volume—lying behind the first flow volume, as seen from the heating device. However, this heat has to pass through the first flow volume, more precisely: the fluid contained therein (refrigerant) and fixed mechanical components, such as their walls, and especially through one or more turbulators optionally provided therein.

[0018]This structure differs from the approach described at the beginning, primarily to heat the coolant, since here the heat capacity or heat absorption is significantly higher than in the refrigerant and consequently an advantageous concentration of the heat for the intended purpose would be anticipated. However, tests and calculations carried out show a surprising advantage in that it is precisely the lower heat capacity of the refrigerant compared to the coolant that leads to relatively less heat energy remaining in the first flow volume (or being absorbed in the fluid) from the heat fed in via the bottom wall by means of heating power, and thus enough heat can still reach the second flow volume via the first flow volume to bring about the desired heating of the coolant. It has turned out that, conventionally, when namely the coolant is heated primarily and the refrigerant is heated secondarily, too much heat is removed from the coolant during operation. This can usually only be compensated for by reducing the flow rate which, however, may be associated with drawbacks and may lead to excessively high coolant temperatures. The arrangement of the first flow volume, through which the refrigerant flows, adjacent to the bottom wall and thus in close proximity to the heating device achieves a particularly good balance between the degree of heating and a desired volume flow in both fluid circuits.

[0019]According to an advantageous embodiment of the heat exchanger, at least one first turbulator is installed in the first flow volume for the refrigerant to flow through. Preferably, at least one second turbulator is also installed in the second flow volume for the coolant to flow through. Such a turbulator not only has the property of bringing about efficient swirling or mixing of the different fluid components in the flow, but especially also enables an efficient heat transfer to the fluid via a large contact area with respect to the fluid. In the present case, however, particular use is made of the fact that the turbulator is in thermal contact both with the bottom wall and with the first partition between the first flow volume and the second flow volume. This further improves the conduction of heat from the bottom wall to the second flow volume in comparison to a situation in which heat is transported only via the fluid (and optionally the lateral side walls which connect the bottom wall and the partition).

[0020]In a preferred embodiment, for the purpose of improved heat conduction from the bottom wall to the partition, the at least one first turbulator is secured both to the bottom wall and to the opposite first partition, preferably by brazing. This embodiment can optionally be further improved by the at least one first turbulator having a lattice structure which is formed from a flat workpiece of a first wall thickness by accordion-like folding and has a lattice period (also called pitch). The flat workpiece can be a plate made of a heat-conducting metal, for example an aluminium alloy. By means of the introduction of slots, a filigree structure with a large surface area in the folded workpiece can be achieved. The original shape of the flat workpiece with suitable folding makes it possible to configure extensive contact portions between the turbulator and the bottom wall or the first partition, which can then optionally be brazed or else welded. The greater the contact area, the better is the heat conduction to the second flow volume through the turbulator.

[0021]A preferred refinement makes provision to adjust the wall thickness of the workpiece on which the turbulator is based, in particular to be thicker. The case is considered in which the bottom wall and the first partition are arranged substantially parallel to each other, wherein a heat conduction direction extends perpendicular to the bottom wall and the partition. In this case, the bottom wall, based on its cross-sectional area perpendicular to the heat conduction direction, has a first heat conductivity value R_th1, and the at least one first turbulator, in the event of a plurality of first turbulators, the overall number of same, based on a cross-sectional area of the first flow volume perpendicular to the heat conduction direction, has a second thermal resistance R_th2. The second thermal resistance R_th2 of the at least one first turbulator, or corresponding to the overall number of the first turbulators, is 10% or more of the first thermal resistance R_th1, preferably 11% or more, more preferably 12% or more.

[0022]However, a thicker wall thickness also increases the flow resistance. This can preferably be compensated for by a suitable orientation of a preferred flow direction, which is defined by the folding direction of the workpiece (and runs transversely to the folding direction), relative to the flow direction, preferably parallel thereto. The flow direction itself is defined by the position of the fluid inlet, the fluid outlet and by possible flow-conducting dividing walls.

[0023]In the case described above in which the at least one first turbulator has a lattice structure which is formed from a flat workpiece of a first wall thickness by accordion-like folding and has a lattice period, the greater wall thickness means that a ratio of the lattice period to the first wall thickness is 20:1 or less. “Greater” refers here to a comparison with the wall thickness of a turbulator of the same design, as would be used, for example, in a fluid heater of a simple auxiliary heating means (only heat exchange between a heating device and a single fluid) with the same dimensions. If, for example, a wall thickness of 0.3 mm for the turbulator in the case of the simple auxiliary heating means provides an optimum compromise between flow resistance and heat transfer with otherwise similarly dimensioned external dimensions (length×width×height) of the flow volume (above ratio, e.g. approx. 30:1), in this case, a wall thickness of 0.4 to 0.5 mm can provide an optimum value with regard to the heat conduction to the second flow volume.

[0024]According to a further special refinement, at least two, preferably three, first turbulators are installed in the first flow volume for the refrigerant to flow through. Furthermore, at least one dividing wall connecting the bottom wall and the first partition, in the event of three first turbulators, for example, two dividing walls connecting the bottom wall and the first partition, extends in the first flow volume. Said dividing wall or walls divide the first flow volume in such a way that the refrigerant flows sequentially, i.e. successively, through the at least two or three first turbulators from the first fluid inlet to the first fluid outlet. The dividing walls do not necessarily have to connect the bottom wall and the partition to each other, but they may, for example, have a small distance to the bottom wall and/or the partition, with the effect thereof on the flow deflection being small. In general, at least one dividing wall extending between the bottom wall and the first partition is included in the first flow volume, i.e. according to this embodiment; in the case of three first turbulators, two dividing walls extending between the bottom wall and the first partition are included. For example, dividing walls can be an integral part of the bottom wall or the partition and can be connected on the other side to the partition or the bottom wall by brazing. As a result, the flow through the sequential turbulators is as homogeneous as possible and at the same time (at a given volume flow rate) a maximum heat input is achieved. The sequential throughflow does indeed increase the flow resistance, which is why the division preferably only needs to be used for the refrigerant. For the refrigerant, however, it affords the special advantage that a required amount of heat can be introduced more easily, since in this case there is a longer dwell time in the respective volume. It should furthermore be taken into consideration that the refrigerant is also subject to evaporation.

[0025]A development for this purpose provides that a cross-sectional area which is defined in the partial volume of the flow volume perpendicular to the respective flow direction, which partial volume is formed by the partition or the partitions and is filled by the respective first turbulators, increases in each case from the first fluid inlet to the first fluid outlet. As a result, the volume flow towards the first fluid outlet slows down, and therefore the distribution of the heat absorbed in the refrigerant over the cross-sectional area (parallel to the bottom wall or first partition) is approximately constant, because since the refrigerant in the vicinity of the fluid outlet is already heated, it actually absorbs less heat here. However, in the vicinity of the fluid outlet, the dwell time is also higher as compensation, which increases the heat absorption again. Overall, the heat conduction towards the second flow volume is therefore homogenized across the area. An additional aspect consists in that the refrigerant evaporates and then takes up a larger volume. Also for this reason, the cross sections in the flow direction can be successively larger (with a correspondingly decreasing flow rate).

[0026]According to a further development, a second wall thickness of the second turbulator for the second flow volume for the coolant to flow through may be smaller than the first wall thickness of the first turbulator, especially if no further flow volumes are connected.

[0027]Furthermore, a second partition which is parallel to the first partition and together with the first partition limits the second flow volume can be adjoined by a third flow volume for the refrigerant to flow through again, which third flow volume is connected to the first fluid inlet and the first fluid outlet. The refrigerant flows through the first and third flow volumes preferably in parallel. With regard to the third flow volume, a structure with at least two, preferably three third turbulators and corresponding dividing walls can be constructed in the same way as in the first flow volume. Preferably, even in the third flow volume, the preferred flow directions defined by the lattice structure of the third turbulators are oriented parallel in relation to the respective flow direction. In contrast thereto, in an alternative configuration, however, the preferred flow directions defined by the lattice structure of the third turbulators can be oriented transversely or inclined with respect to the respective flow direction.

[0028]Alternatively or in association therewith, in this case, a third wall thickness of the at least one third turbulator (or the third turbulators) may be less than the first wall thickness of the at least one first turbulator. Preferably, a ratio of the lattice period of the at least one third turbulator to the third wall thickness can be more than 20:1 here. Thinner walls can be used remotely, for example, because the wall thickness can be used in particular to adjust the heat conductivity through the material from passage to passage. Conversely, in principle, however, it is also conceivable to increase the wall thickness in the more remote volumes.

[0029]This results in a higher pressure loss in the more remote passage and allows more heat to be introduced into the passage adjacent to the heating means.

[0030]In the second flow volume and optionally a fourth flow volume, through which coolant flows, a second and optionally a fourth turbulator with an accordion-like folding structure and preferred flow direction perpendicular to the folding direction is preferably included, in which the turbulator is arranged such that its preferred flow direction is oriented transversely to a main flow direction of the flow volume.

[0031]According to a further development, the at least one second turbulator substantially fills the second flow volume, with the exception of two regions extending transversely to an imaginary connecting line between the second fluid inlet and the second fluid outlet directly at the fluid inlet and at the fluid outlet, respectively. This enables a more uniform distribution of the flow across the turbulator cross section and ensures a substantially parallel flow direction in the flow volume. The main flow direction here is essentially between the main sides, along which the regions free from turbulator extend.

[0032]As described, at least the at least one first turbulator, preferably also all the further turbulators, may be formed from an aluminium alloy, preferably with magnesium and/or silicon, e.g. the special aluminium alloys “3003” or “6060”. The bottom walls and partitions can preferably be formed from the same material.

[0033]According to a further development, the fluid inlet and the fluid outlet for the first flow volume for the refrigerant to flow through are designed as connectors. The connector of the fluid inlet is provided with a receptacle for an expansion valve of the refrigerant circuit. Alternatively or additionally, the connector of the fluid inlet and/or the fluid outlet is provided with a receptacle for a temperature sensor.

[0034]According to exemplary embodiments, the heating device can comprise a heating conductor layer which is formed on the bottom wall or on a substrate attached thereto and in which heating strip conductors are formed.

[0035]In particular, the heating device can be implemented in various ways, and the invention is not limited to certain embodiments thereof. For example, the heating device can consist of thermally sprayed layers. Atmospheric plasma spraying can be used, for example, as a coating process during production. It is also possible to apply heating elements on both sides, i.e. also on the bottom wall. Starting from the flat plate, the layer structure first results in an optional adhesive base, then an insulation ceramic, the actual heating conductor layer and optionally a cover layer or seal. The heating conductor layer can be structured by laser or by masking. The material of the heating conductor can be a material having linear or PTC resistance behaviour.

[0036]Polymer-based heating devices having PTC behaviour are also suitable. Heating elements made of plastic foils may also be involved. The heating elements usually consist of an extruded or laminated polymer matrix in which a heating conductor and a positive and negative electrode are embedded.

[0037]Furthermore, the heating device may also comprise ceramic heating elements having PTC behaviour (PTC thermistors).

[0038]In addition, the heating device can be designed as a thick-film heating element. In this case, the carrier element in turn can be the bottom wall of a heat exchanger. The carrier element or bottom wall can have applied to it the thick-film heating element, which may be a dielectric and a heating conductor for providing a flat heating resistance.

[0039]Alternatively, the heating device may comprise a ceramic substrate (as a carrier element), for example consisting of Al₂O₃, with a screen-printed heating conductor layer. Here, the heating conductor layer may be formed, for example, as a metallization of a resistance alloy, which constitutes the corresponding heating resistance. Examples include an iron-nickel alloy or a nickel-chromium alloy. An insulation interruption provides for the structuring of long strip conductors from the layer which is otherwise applied flat and later burned in, and can already be produced, for example, during the application by means of a screen printing process. The ceramic substrate can be a ceramic carrier plate. According to aspects of the invention, this embodiment of a heating element is preferred.

[0040]In the case of the described polymer-based heating element having PTC behaviour, the ceramic heating element having PTC behaviour or the heating device with a ceramic substrate with a screen-printed heating conductor layer, the flat heating device can be applied to the preferably flat bottom wall by means of a thermal intermediary as an adhesive layer, e.g. thermally conductive adhesive. The thermal intermediary and the heating element or the heating device can be applied with the aid of a pressing device.

[0041]In all of these cases, a heating device is present which is extensively arranged on or lying against the bottom wall and, beyond the bottom wall, lying opposite the first flow volume or the refrigerant. According to exemplary embodiments, the area projected onto the bottom wall by the turbulator and the area projected onto the bottom wall by the heating device or the heating elements concerned substantially coincide (degree of overlap of the projected heating element area to the projected turbulator area of the first passage, e.g. greater than 60%, greater than 70%, greater than 80% or even greater than 90%; preferably greater than or equal to 60% and less than or equal to 80%).

[0042]A circuit board with power electronics can also be arranged on the bottom wall. The corresponding circuit breakers can also be positioned on the bottom wall such that they lie opposite the first flow volume in order to participate in a heat transfer as well.

[0043]Alternatively or additionally, the side of the bottom wall with the heating device (optionally also with the power electronics) can be closed by a housing cover that protects against dirt and contact with body parts. As described above, the flow volumes of the fluids involved are arranged exclusively on that side of the bottom wall or carrier plate which faces away from the heating device and the housing cover.

[0044]The bottom wall can extend towards one or more sides beyond the first flow volume lying opposite the heating device. The extended surface region of the bottom wall is firstly provided for the attachment of a control housing to the bottom wall, the control housing accommodating or providing a control device (ECU) and the power supply for the heating device. One refinement provides that the control housing is attached on the same side of the bottom wall as the stack of flow volumes. This has the advantage that both the fluid connections and the electronic connections (HV for power and LV for communication) are arranged on the same side of the bottom wall now acting as a carrier plate, which substantially facilitates implementation in the installation space of the vehicle, in particular motor vehicle, since operating and maintenance access should be kept free only from one side. For this purpose, the bottom wall can have one or more openings which allow passage of the corresponding lines (HV supply for the power electronics for heating, LV lines for controlling the circuit breakers for temperature sensors, e.g. on the circuit board with the power electronics) from the control housing to the other side towards the heating device or the power electronics thereof.

[0045]The first flow volume can be limited or defined in the vertical direction by the bottom wall and the first partition, which are preferably oriented parallel to each other as described. An advantageous refinement provides that also a first lateral enclosure wall limiting the first flow volume is integrally formed on the bottom wall (e.g. by welding or brazing). The bottom wall or the carrier plate forming the latter comprises a trough-like structure, which is covered by the first partition. The first lateral enclosure wall, which correspondingly runs all the way around, can be continuously slightly inclined outwards in relation to the vertical direction perpendicular to the bottom wall. That is, the trough expands upwards. A second trough, which is substantially identical in structure, can be inserted into said first trough, the second trough being formed by the first partition and an upwardly bent edge—e.g. by deep drawing the flat blank. The upwardly curved edge here forms the corresponding second lateral enclosure wall for the following second flow volume. This side wall also expands in the vertical direction, and therefore a desired majority of troughs can be used in this way. The enclosure walls meeting one another in each case conically on the inside or outside in this process can be brazed in a simple way. The enclosure walls are merely expanded in such a way that the respective flow volumes are maintained between the troughs nested one inside the other. Their height corresponds to the turbulators respectively attached therein, and therefore the latter can be brazed on or welded at the top and bottom. Overall, there is a particular advantage in that only two components have to be attached per flow volume (the next trough and the corresponding turbulator) and the production process is thus considerably simplified. In addition, there is in each case only one physical wall between the flow volumes. However, the invention does not exclude the situation in which each flow volume provides a completely separate, container-like boundary wall formed all the way around, such that the partitions according to the invention (as well as the bottom wall) may be entirely multi-layered.

[0050]Heating the coolant without heating the refrigerant circuit can be achieved by reducing the volume flow in the refrigerant circuit to zero. In this case, the first flow volume passes the transferred heat only through to the second flow volume.

[0051]According to a further embodiment, the heat exchanger has at least five flow volumes. In a development of this embodiment, refrigerant can flow through the first, the third and the fifth flow volumes, and coolant can flow through the second and the fourth flow volumes.

[0052]According to a further embodiment, the heat exchanger has at least six flow volumes. In a development of this embodiment, refrigerant can flow through the first, the third and the fifth flow volumes, and coolant can flow through the second, the fourth and the sixth flow volumes.

[0053]According to a further embodiment, the heat exchanger has at least seven flow volumes. In a development of this embodiment, refrigerant can flow through the first, the third, the fifth and the seventh flow volumes, and coolant can flow through the second, the fourth and the sixth flow volumes. In principle, the heat exchanger can also have more than seven flow volumes.

[0054]In an embodiment with three flow volumes through which coolant can flow, said flow volumes can be connected in terms of flow in such a way that coolant can flow through them in parallel.

[0055]In a further advantageous embodiment, the heat exchanger has at least two flow volumes through which refrigerant can flow, said flow volumes being connected to one another in terms of flow in such a way that the flow can pass through at least one of said flow volumes sequentially to the other of said flow volumes.

[0056]In the case of an embodiment with a first, third and fifth flow volume, said flow volumes are connected to one another in terms of flow in such a way that refrigerant can flow through at least the fifth flow volume sequentially to the first and third flow volumes. The first and the third flow volumes can be connected to each other in terms of flow in such a way that refrigerant can flow through them in parallel to each other.

[0057]In the case of an embodiment with a first, third, fifth and seventh flow volume, through each of which refrigerant can flow, the flow can pass through the first and the third flow volume and the fifth and the seventh flow volume in each case in parallel to each other. Furthermore, refrigerant can flow through the fifth and the seventh flow volumes sequentially to the first and third flow volumes.

[0058]Further embodiments of the invention result from the appended dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0059]Exemplary embodiments of the invention will be explained in more detail below with reference to the drawings, in which:

[0060]FIG. 1 shows a perspective view of a heat exchanger having an electric high-voltage heating device according to an exemplary embodiment;

[0061]FIG. 2 shows the heat exchanger from FIG. 1 from a different perspective;

[0062]FIG. 3 shows a top view of the bottom wall of the heat exchanger from FIG. 1 with heating elements of the heating device attached thereto;

[0063]FIG. 4 shows a perspective view of the heat exchanger with the control housing removed;

[0064]FIG. 5 shows a highly schematic cross-sectional view of a section through the bottom wall with a stack of flow volumes attached thereto;

[0065]FIG. 6 shows a perspective view of the turbulators associated with the flow volumes with bottom wall and partitions removed, but including fluid inlets and outlets;

[0066]FIG. 7 shows the turbulators from FIG. 6 in an exploded illustration;

[0067]FIG. 8 shows an enlarged perspective view of a detail of a first turbulator of the first flow volume positioned closest to the bottom wall;

[0068]FIG. 9 shows the same as in FIG. 8, but with respect to a second turbulator of the second flow volume adjoining the first flow volume in the stack;

[0069]FIG. 10 shows the same as in FIG. 8 or 9, but with a comparison of the first turbulator and a third turbulator of a third flow volume adjoining the second flow volume in the stack;

[0070]FIG. 11 shows a highly schematic cross-sectional view, according to an alternative exemplary embodiment, of a section through the bottom wall with a stack of flow volumes attached thereto and flow paths of the refrigerant through them shown;

[0071]FIG. 12 shows a highly schematic cross-sectional view analogous to FIG. 11 of a section through the bottom wall with a stack of flow volumes attached thereto and flow paths of the coolant through them shown.

DETAILED DESCRIPTION:

[0072]In the description below of a preferred exemplary embodiment, it should be taken into consideration that the present disclosure of the various aspects is not limited to the details of the structure and the arrangement of the components as illustrated in the description below and in the figures. The exemplary embodiment can be implemented or carried out in various ways in practice. It should also be taken into consideration that the wording and terminology used here is used merely for the purpose of the specific description and should not be interpreted restrictively as such by a person skilled in the art. In addition, in the description below, the same reference signs in the exemplary embodiment or the figures denote identical or similar features or objects, and therefore in some cases a repeated detailed description of them is omitted in order to maintain the compactness and clarity of the illustration.

[0073]In each of FIGS. 1 and 2, a heat exchanger 1 having an electric (high-voltage) heating device 51 according to an exemplary embodiment is shown in a perspective view. This in particular involves a fluid-fluid heat exchanger having a heating device, e.g. for a heat management system in purely electrically powered or hybrid vehicles, in particular motor vehicles. The fluids can be a refrigerant of a refrigerant circuit of a heat pump, on the one hand and a coolant of a coolant circuit, or a plurality of coolant circuits which can be configured, for example, via three-way valves depending on the operating mode, on the other hand.

[0074]The heat exchanger 1 comprises a control module 10, a heat exchanger module 20 and a heating module 50. The control module 10 has a control housing 11 which is preferably formed from plastic and which accommodates a control board (not shown) which acts as an ECU (electronic control unit). A high-voltage connection socket 12 and a low-voltage connection socket 13 can be used to connect the control board to a vehicle electrical system for the power supply and for communication with a BCM (body control module). The control housing 11 can be closed via a control housing cover 14 (see FIG. 2).

[0075]The heat exchanger module 20 comprises a bottom wall 30, which also serves as a carrier plate for the components and modules. The bottom wall 30 is designed as a level, flat and substantially rectangular plate (with rounded edges) made from a material of high heat conductivity, in particular an aluminium alloy. A first lateral enclosure wall 31 is integrally formed with the bottom wall 30, said enclosure wall surrounding or forming a flat rectangular region (also again with rounded edges) on the bottom wall 30. The first lateral enclosure wall 31 extends virtually perpendicular to the bottom wall 30, but also extends slightly upwards. This flat rectangular region forms a first flow volume 21 for a refrigerant to flow through, said first flow volume being shown in the highly simplified schematic cross-sectional view of FIG. 5.

[0076]A second component which is formed from a first partition 81 and a second lateral enclosure wall 32 is mounted on this component, which is formed from the bottom wall 30 and the first lateral enclosure wall 31. The first partition 81 extends parallel to the bottom wall 30, lies opposite the latter and limits the first flow volume 21 upwards. The second lateral enclosure wall 32, like the first lateral enclosure wall 31, extends virtually perpendicular to the first partition 81 and forms a second flow volume 22 for a coolant to flow through. By expansion of the first lateral enclosure wall 31, a lower end of the second lateral enclosure wall 32 can be received in an upper edge region of the first lateral enclosure wall 31 and brazed to the latter in order to seal the first flow volume 21. Like the first lateral enclosure wall 31, the second lateral enclosure wall 32 also expands upwards or conically outwards.

[0077]In the same way, a third component which is formed from a second partition 82 and a third lateral enclosure wall 33 is mounted on this component, which is formed from the first partition 81 and the second lateral enclosure wall 32. The second partition 82 extends parallel to the first partition 81 and the bottom wall 30, lies opposite the first partition and limits the second flow volume 22 upwards. Like the first and second lateral enclosure walls 31, 32, the third lateral enclosure wall 33 extends virtually perpendicular to the second partition 81 and forms a third flow volume 23 for the refrigerant in turn to flow through. By expansion of the second lateral enclosure wall 32, a lower end of the third lateral enclosure wall 33 can be received in an upper edge region of the second lateral enclosure wall 32 and brazed to the latter in order to seal the second flow volume 22. Like the first and second lateral enclosure walls 31, 32, the third lateral enclosure wall 33 also expands upwards or conically outwards.

[0078]In the same way in turn, a fourth component which is formed from a third partition 83 and a fourth lateral enclosure wall 34 is mounted on this component, which is formed from the second partition 82 and the third lateral enclosure wall 33. The third partition 83 extends parallel to the second partition 82, the first partition 81 and the bottom wall 30, lies opposite the second partition and limits the third flow volume 23 upwards. Like the first, second and third lateral enclosure walls 31, 32, 33, the fourth lateral enclosure wall 34 extends virtually perpendicular to the second partition 82 and forms a fourth flow volume 24 for the coolant in turn to flow through. By expansion of the third lateral enclosure wall 33, a lower end of the fourth lateral enclosure wall 34 can be received in an upper edge region of the third lateral enclosure wall 33 and brazed to the latter in order to seal the third flow volume 23. Like the first, second and third lateral enclosure walls 31, 32, 33, the fourth lateral enclosure wall 34 also expands upwards or conically outwards.

[0079]On the fourth lateral enclosure wall 34 is arranged an upper covering wall parallel to the third partition 83, said upper covering wall limiting the fourth flow volume 24 upwards and closing off the resulting stack of four flow volumes 21-24. As a result, the four flow volumes are configured in an alternating manner for the refrigerant and coolant to flow through, as viewed from the bottom wall 30 starting with the refrigerant. Apart from the slight expansion of the lateral enclosure walls 31-34, which allows the trough-shaped components to be nested one inside the other, these lateral enclosure walls are substantially flush with each other, resulting in an overall closed, cuboidal stack structure for the sum total of the fluid chambers. The stacking direction is perpendicular to a plane formed by the bottom wall 30.

[0080]The first flow volume 21 and the third flow volume 23 are each opened up by a first fluid inlet 61 and a first fluid outlet 62 and incorporated in a refrigerant circuit of a heat pump (not shown). For this purpose, a respective connector of the first fluid inlet 61 and the first fluid outlet 62 also extends through the partitions 81, 82, 83 and the upper covering wall 35. Said connectors are positioned in diagonally opposite corners of the flow volumes or stack. The first fluid inlet 61 and the first fluid outlet 62 are configured in their structure for coupling to the refrigerant circuit of a heat pump. They have a first receptacle 65 for an expansion valve (not shown) and a second receptacle 66 for a temperature sensor (not shown). By means of the expansion valve, the first flow volume 21 and the third flow volume 23 obtain the function of an evaporator in the refrigerant circuit. With the aid of the temperature sensors, which can be connected to the control board (not shown), suitable monitoring with control or regulation, inter alia, of the heat transfer, e.g. by adjusting a heating power and/or the volumetric flows both in the refrigerant circuit and in the coolant circuit, can be carried out.

[0081]The second flow volume 22 and the fourth flow volume 24 are each opened up by a second fluid inlet 71 and a second fluid outlet 72 and incorporated in a coolant circuit (not shown) of the vehicle. The second fluid inlet 71 and the second fluid outlet 72 each have a connector designed as a quick-action coupling for connection to a coolant hose. Said connectors are positioned in the remaining two diagonally opposite corners of the flow volumes or stack. They also extend at least through the partitions 82, 83 and the upper covering wall 35.

[0082]FIG. 3 shows a top view of the bottom wall 30. The bottom wall 30 has a side surface 39 (heat exchanger side) facing the stack of fluid chambers through which the flow passes (flow volumes) and a side surface 38 facing the heating device 51. FIG. 3 shows the top view of the side surface 38 facing the heating device 51. Three heating elements 52 of the heating device 51 are positioned on the side of the bottom wall 30 opposite the first flow volume 21. The heating elements 52 each have heating conductor layers applied to ceramic substrates and heating strip conductors structured in thick-film technology, which act as a heating resistance when applying or switching a high voltage. The heating strip conductors can have a meandering layout on the ceramic substrate (not shown). The circuit breakers can be placed on an additional board (not shown) mounted on the bottom wall 30, or can be located in the control housing 11, e.g. on the control board.

[0083]The bottom wall furthermore has holes 36, which allow the control housing 11 to be attached to the bottom wall 30 on the side surface 39 facing the stack of fluid chambers. Openings 37 are provided to allow passage of high-voltage and control lines to the heating elements 52 or to any temperature sensors.

[0084]FIG. 4 shows the bottom wall 30 with the stack of fluid chambers, looking at the side surface 39. The cross-sectional view of FIG. 5 shows that the heating device 51 is positioned with a large overlap (degree of overlap e.g. over 80%-90%) opposite the first flow volume for the refrigerant to flow through. As can also be seen schematically in FIG. 5, each fluid chamber or each flow volume 21-24 has a turbulator on 41-44. The turbulators 41-44 are fixedly connected to the respective lower wall (e.g. bottom wall 30) and upper wall (e.g. first partition 81) via extensive contact surfaces 49 (see FIG. 10), e.g. by brazing. As a result, a large portion of the respective heat transfer to the nearest flow volume takes place via the turbulators and only secondarily via the fluids themselves.

[0089]FIG. 6 shows the arrangement of the turbulators 41-44 with the partitions and side walls, etc., having been removed. The turbulators 41-44 fill a large portion of the interior of the flow volumes 21-24 and thus reproduce their stacked arrangement in FIG. 6. In a projection in the heat conduction direction or vertical direction 26 perpendicular to the bottom wall 30, the flow volumes 21-24 and the turbulators 41-44 substantially overlap.

[0090]In the case of the first and third flow volumes 21, 23 for the refrigerant to flow through, however, comparatively larger volumetric regions are not filled with the turbulators 41, 43, as can be seen from the exploded illustration of FIG. 7. The first and third flow volumes 21, 23 each comprise three individual first turbulators 41a, 41b, 41c and third turbulators 43a, 43b, 43c and are also divided by dividing walls 46 and 48 such that the refrigerant flows through the turbulators sequentially. Starting from the respective fluid inlet 61, the dividing walls 46 and 48 form three sub-chambers, which are separated from each other by deflection regions (indicated in FIG. 7 by deflection arrows). These deflection regions are kept free from the first and third turbulators to ensure efficient deflection and to avoid dead angles where the fluid is only slowly exchanged. Also, the regions around the respective fluid inlet and outlet 61, 62 are kept free for the same reasons.

[0091]It should also be noted that a cross-sectional area or a width b1, b2, b3, perpendicular to the respective flow direction, of the first or third turbulators 41a, 41b, 41c, 43a, 43b, 43c or of the corresponding sub-chambers increases from the fluid inlet 61 to the fluid outlet 62.

[0092]By contrast, in the case of the second and fourth flow volumes 21, 23 for the coolant to flow through, only the regions directly underlying the connectors 42a, 42c, 42e and 42f and 44a, 44c, 44e and 44f in question, and also, on the end face, those volumetric regions 42b, 42d and 44b, 44d which extend from said regions and are near the second and fourth lateral enclosure walls 32, 34 are kept clear and are intended to ensure a better, i.e., more homogeneous flow of the fluid through the turbulators 42 and 44.

[0093]FIGS. 8 and 9 show a comparison between one of the first turbulators 41 (e.g. the first turbulator 41a, 41b or 41c) and the second turbulator 42 in greater detail. In the exemplary embodiment, the turbulators are produced from a flat, plate-like workpiece with an individual wall thickness by slots being introduced into them and then the workpiece being periodically folded along a folding direction 47. The slots permit projections, which are formed by the slots, to be bent out in alternating fashion. It can be seen that a wall thickness of the workpiece in the case of the first turbulator 41 is greater than in the case of the second turbulator 42. For example, the wall thickness of the first turbulator 41 is about 0.45 mm, while the wall thickness of the second turbulator 42 is about 0.3 mm. In both cases, the lattice period 45 is approximately 9 mm. The ratio of the lattice period 45 to the wall thickness is therefore approx. 20:1 for the first turbulator 41 and approx. 30:1 for the second turbulator 42.

[0094]FIG. 10 shows a comparison between one of the first turbulators 41 (e.g. the first turbulator 41a, 41b or 41c) and one of the third turbulators 43 (e.g. the first turbulator 43a, 43b or 43c). The wall thickness can (but does not have to) be selected to be the same here. By contrast, the lattice period 45 between the turbulators 41 and 43 is varied here. The lattice of the third turbulator 43 has a greatly increased lattice period 45, which leads to a flow resistance in the third flow volume 23 being significantly reduced, because fewer filigree structures per volume oppose the flow.

[0095]The alternative exemplary embodiment shown in FIGS. 11 and 12 is a heat exchanger 1, which has seven flow volumes. In comparison to the exemplary embodiments according to FIGS. 1 to 10, the heat exchanger additionally has a fifth flow volume 27, a sixth flow volume 28 and a seventh flow volume 29. By means of the dashed arrows, it is illustrated how in FIG. 11 the refrigerant and in FIG. 12 the coolant can flow through the flow volumes, i.e. how the flow volumes are connected to one another in terms of flow.

[0096]In FIG. 12, the dashed arrows illustrate the coolant flow path 75. The second flow volume 22, the fourth flow volume 24 and the sixth flow volume 28 are connected in terms of flow in such a way that coolant can flow through them in parallel.

[0097]In FIG. 11, the dashed arrows illustrate the refrigerant flow path 74. The first flow volume 21, the third flow volume 23, the fifth flow volume 27 and the seventh flow volume 29 are connected in terms of flow in such a way that refrigerant can in each case flow through the first and the third flow volumes 21, 23 and the fifth and the seventh flow volumes 27, 29 in parallel to each other. Furthermore, refrigerant can flow through the fifth and the seventh flow volumes 27, 29 sequentially to the first and third flow volumes 21, 23.

[0098]All of the features not shown in FIGS. 11 and 12 can be carried out analogously to the exemplary embodiments illustrated in FIGS. 1 to 10, wherein the fifth and the seventh flow volumes 27, 29 can be configured analogously to the third flow volume 23, and the sixth flow volume 28 can be configured analogously to the fourth flow volume 24, in particular with respect to the internal flow path, side walls and turbulators. In contrast to the exemplary embodiments according to FIGS. 1 to 10, in the exemplary embodiment shown in FIGS. 11 and 12, the fluid outlets 61, 61 (not shown) can be formed on the bottom wall 30.

[0099]Completely different exemplary embodiments are possible. For example, it can be provided that, instead of the bottom wall finally closing the fluid chamber stack, as described above, the housing cover is not arranged on the other side of the heating device 51, but rather there is a further bottom wall, from which a corresponding stack of fluid chambers continues in the opposite direction. Overall, the heating device is then arranged between two flow volumes in a sandwich-like structure of flow volumes. The flat heating device 51 could emit its heat in two (opposite) directions. The respective flow volumes for the refrigerant and the coolant could each be correspondingly connected to each other between the stacks. In principle, this involves a heating device 51 which is integrated intermediately in a single stack and is adjacent on at least one side directly to a flow volume conducting refrigerant. It is also possible and preferred that then a flow volume conducting refrigerant is adjacent on both sides of the heating device 51 beyond the relevant wall; the arrangement is reflected, as it were, to the heating device. These exemplary embodiments which are directed to a dedicated sandwich-like structure can be combined, for example, with all of the features specified in the appended claims.

LIST OF REFERENCE SIGNS