Electric liquid heating device for a vehicle

Abstract

An electric heating device (10), in particular an electric heating device for a vehicle, comprises a heating element (20, 60a, 60b, 60c) which is configured to convert electric energy supplied to it into heat; and a heat exchanger (12) which is in thermal operative connection with the heating element (20, 60a, 60b, 60c) and is configured to transfer heat supplied to it by the heating element (20, 60a, 60b, 60c) to a fluid (F) which flows through said heat exchanger. The heat exchanger (12) has a flat fluid chamber (120) which defines a heat exchanger region, a fluid inlet (12), a fluid outlet (14) and a turbulator (40) for the heat transfer which is arranged in the fluid chamber (120), wherein the fluid chamber (120) is formed by delimiting walls. At least one current deflection apparatus is provided within the heat exchanger region of the fluid chamber (120), in particular at the turbulator (40), and / or in a region of the delimiting walls which is opposite the turbulator. Said current deflection apparatus is designed to influence a flow guidance of the fluid through the fluid chamber.

Description

[0001] ELECTRIC LIQUID HEATER FOR A VEHICLE

[0002] Description

[0003] Technical area:

[0004] The present invention relates to an electric heating device, in particular an electric liquid heater for a vehicle

[0005] Technical background:

[0006] Known electrical heating devices, such as those used in vehicles, particularly electric and / or hybrid vehicles, generally comprise an electrical heating conductor layer which is arranged adjacent to a heat exchanger and converts the electrical energy with which it is supplied into heat. The heat is transferred to the heat exchanger, through which a fluid flows, which is consequently heated. The heated fluid is fed via a fluid outlet or outflow of the heating device, for example, to a fluid circuit, via which it is transported to a location where it releases the heat in the desired manner. The cooled fluid is then fed back to the heat exchanger via the fluid circuit, into which it re-enters through a fluid inlet or inlet to be heated again.

[0007] The heating output is typically adjusted by a control unit. The heating output can be adjusted based on the temperature the fluid has reached upon leaving the heat exchanger. The temperature can be determined or recorded, for example, using a temperature sensor. The temperature sensor is therefore usually placed near the fluid outlet. Basically, two approaches are available for this purpose:

[0008] Firstly, the temperature sensor can be placed outside in a wall of the heat exchanger near the fluid outlet for the coolant, preferably in an area where the flowing fluid (with locally varying temperatures during the flow) has been sufficiently mixed again due to the flow conditions. A corresponding recess, such as a blind hole or similar, can be formed in the wall for this purpose. However, this approach requires that the coolant outlet area around the fluid outlet is appropriately accessible and that a structural implementation with sufficient thermal and mechanical connection to the heat exchanger wall can be implemented.Furthermore, it must be ensured that the fluid is sufficiently mixed internally at the installation location due to the specific flow conditions to enable an average coolant temperature to be recorded. This is usually achieved if there is a sufficiently large flow volume (fluid throughput per unit time) and / or a sufficiently large volume of space between the heat exchanger area and the location where the temperature sensor is installed. However, meeting these requirements entails disadvantages in terms of installation space, weight, and cost.

[0009] Alternatively, the temperature sensor can also be placed directly in the coolant or fluid, i.e., in the interior of the heat exchanger. However, this requires a hole to be drilled through the wall of the heat exchanger into its interior or hydraulic area—for the reasons mentioned above, preferably near the fluid outlet, in order to maintain the temperature achieved for the control circuit during heat transfer.

[0010] The consequence of this, however, is that a sealed opening for the cable connection or, for example, a sealing thread for the implementation of the temperature sensor must be implemented directly in the coolant or flowing fluid, which increases costs and effort. In addition, especially in the case of special use in a high-voltage heater, a leak if this opening is inadequately or degradingly sealed can always have critical consequences in terms of electrical short circuits in the high-voltage area (e.g. the adjacent control electronics) and thus affect the safety of the entire system. Furthermore, even in the event of a break, the coolant or fluid must be sufficiently mixed to achieve a uniform temperature distribution in the flow cross-section at the position of the temperature sensor, so that the corresponding recorded value is representative of an average temperature.

[0011] There is an overall need to reduce the effort and costs for temperature detection, which is necessary for controlling the heating output, and to remove the restrictions regarding the required installation space or weight in the vehicle.

[0012] Description of aspects of the invention: According to various aspects of the invention, an electric heating device, in particular an electric liquid heater for a vehicle, which can meet these needs, comprises at least one heating element which is designed to convert electrical energy supplied to it into heat, and a heat exchanger which is in thermal connection with the at least one heating element and is designed to transfer heat supplied to it by the heating element to a fluid flowing through it.

[0013] The heat exchanger has a flat fluid chamber defining a heat exchanger region therein. Furthermore, the heat exchanger has a fluid inlet, a fluid outlet, and a turbulator for heat transfer arranged in the fluid chamber, wherein the fluid chamber is formed by boundary walls.

[0014] Within the heat exchanger region of the fluid chamber, in particular at the turbulator, and / or in a region of the boundary walls opposite the turbulator, at least one flow deflection device is formed, which is designed to influence the flow guidance of the fluid through the fluid chamber. According to exemplary embodiments, the flow deflection device can be designed in various ways. However, it has been found that such structural measures for flow deflection have a particularly advantageous effect when implemented within the heat exchanger region and not (only) outside.

[0015] In particular, by installing at least one flow diversion device, it is possible to achieve a desired mixing of the coolant or fluid across the interior of the fluid chamber. In particular, however, by using at least one flow diversion device, it is possible to specifically achieve sufficient mixing at a desired, i.e. predetermined, location in the fluid chamber, which location may well be at a distance from the relevant fluid outlet. This location can be adjacent to or in the vicinity of an attachment point for a temperature sensor which has proven to be useful or suitable for structural reasons (e.g. as an external specification). The flow diversion device is set up and arranged such that the heat absorbed in the diverted flow up to this location due to the mixing of the flow corresponds to an average temperature which is representative of the thermal state of the fluid subsequently released.

[0016] A temperature sensor that detects this no longer needs to be implemented by breaking through the boundary walls of the interior in order to detect it as "close" to the fluid as possible, but can be placed outside close to the selected location (or a plurality of selected locations or even in larger areas where good mixing is achieved), thus saving costs and effort for implementation and increasing system safety, since there is now no fear of leakage.

[0017] Increasing the distance to the fluid outlet is also possible because the improved mixing allows a reliable temperature value to be determined, which is in a fixed relationship close to the temperature value that the fluid actually has when leaving the heat exchanger through the fluid outlet. For a corresponding temperature difference of, for example, a maximum of 2 °C, large areas of the outer surface of the heat exchanger can already be considered as possible mounting points for temperature sensors if the flow guidance is influenced accordingly by implementing one or more, optionally also by combining different types of, flow deflection devices. For a given layout of a heat exchanger and for specified operating points (defined by heating output, fluid outlet temperature and volume flow), the positioning, dimensioning and orientation, etc.The flow diversion device can be determined, for example, through simulation. For example, a desired location or area on the outer surface of the heat exchanger can be specified, and the exact implementation of the flow diversion device can then be calculated from this specification in the computer-aided simulation.

[0018] Individual embodiments of flow deflection devices are described below. Their effect can be to reduce pressure and / or simply influence the direction of the flow.

[0019] But first, some terms should be explained:

[0020] A vehicle is generally understood to mean all possible mobile applications, in particular passenger cars, trucks, construction machinery, aircraft, and watercraft. This also includes, for example, construction machinery or cranes, as well as trailers such as caravans that can be towed and transported by other vehicles.

[0021] The term liquid heating, as used here, means that the heater transfers heat to a liquid heat transfer medium / fluid of a heat transfer circuit flowing through the heater. The heat transfer medium / fluid can, in particular, be a vehicle's liquid coolant, which transports heat within the vehicle and can release it at various points. Alternatively, the liquid heating can, for example, also be part of a vehicle's heat pump, so that the heat transfer medium / fluid can, for example, be a coolant in a heat pump. In this case, the coolant may only be in completely liquid form under certain conditions and only temporarily, or perhaps never, and may otherwise be partially or completely gaseous. Nevertheless, this is also understood to mean a liquid heater.

[0022] The liquid heater can preferably have a heating output of at least 5 kW, preferably of at least 7 kW, for example of at least 9 kW. The heating output is preferably less than or equal to 13 kW. The operating voltage with which the vehicle heater is operated, which can be the same as the on-board voltage of an electrically powered vehicle, can be greater than or equal to 400 V, preferably greater than or equal to 700 V, for example 800 V, 900 V, or 1000 V. The liquid heater has at least one heating element. This heating element can have a heat conductor layer. The liquid heater preferably has at least two heating elements, particularly preferably at least three heating elements.

[0023] A heating conductor layer can preferably have corresponding heating conductor tracks. The heating conductor layers and heating conductor tracks can be arranged together on a single carrier element. Preferably, each heating conductor layer or each heating conductor track is applied to its own, separate carrier element. The carrier element can also be a wall or plate of the heat exchanger, so that the heat exchanger and heating element can share individual elements.

[0024] The heating element can be implemented in various ways, and the invention is not limited to specific embodiments thereof. The heating element can, for example, consist of thermally sprayed layers. During production, atmospheric plasma spraying can be used, for example, as a coating process. It is also possible to apply heating elements to both sides, i.e., also to the bottom wall. The layer structure, starting from the flat plate, initially consists of an optional primer, then an insulating 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 one with linear or PTC resistance behavior.

[0025] Polymer-based heating elements with PTC behavior are also considered. These can be heating elements made of plastic foil. The heating elements typically consist of an extruded or laminated polymer matrix in which a heating conductor and a positive and negative electrode are embedded.

[0026] Furthermore, the heating elements can also be ceramic heating elements with PTC behavior (thermistor).

[0027] Furthermore, the heating element can be designed as a thick-film heating element. In this case, the carrier element can again be a plate of the heat exchanger. The thick-film heating element, which can consist of a dielectric and a heating conductor to form a planar heating resistor, is applied to this plate.

[0028] Furthermore, the heating element can be designed as a ceramic substrate (as a carrier element), for example made of Al2O3, with a screen-printed heating conductor layer. The heating conductor layer can be formed, for example, as a metallization made of a resistance alloy, which represents the corresponding heating resistance. Examples of suitable materials include an iron-nickel alloy or a nickel-chromium alloy. An insulation interruption ensures the structuring of long conductor tracks from the otherwise flatly applied and later fired layer and can, for example, be created during application using a screen-printing process. The ceramic substrate can be a ceramic carrier plate. This embodiment of a heating element is preferred according to aspects of the invention.

[0029] In the case of the described polymer-based heating element with PTC behavior, the ceramic heating element with PTC behavior, or the heating element as a ceramic substrate with a screen-printed heat-conducting layer, the flat heating element can be applied to the outer side of the cover wall, which is usually designed as a flat plate, using a thermal mediator as an adhesive layer, e.g., a thermally conductive adhesive. The thermal mediator and the heating element can be applied using a pressing device.

[0030] It should be noted that according to embodiments of the invention, heating elements can also be applied on both sides of the heat exchanger, i.e. on the cover wall and on the bottom wall.

[0031] The heat exchanger itself can be made of steel or aluminum, for example, preferably aluminum. According to specific embodiments, the boundary walls forming the flat fluid chamber of the heat exchanger comprise a cover wall, a bottom wall opposite the cover wall, and narrow side walls connecting them, with the fluid inlet and the fluid outlet being formed in the bottom wall. According to the embodiments, the basic structure can have a flat cuboid shape, but it is by no means necessary for opposite walls to be parallel to one another. Rather, they can also enclose an angle. Furthermore, the boundary walls do not necessarily have to be flat, but can optionally have a curved or rounded shape. The cover wall and the bottom wall are preferably flat and extend essentially along a plane defined by the heat exchanger.

[0032] The heat exchanger can also be referred to as a plate heat exchanger or be designed as such. This means that an overall height perpendicular to the cover wall, which is designed as a substantially flat plate and to which the heating element can be attached or which also forms the heating element, is significantly smaller than a width and length with which it extends parallel to the cover wall. The ratio of the overall height to length / width of the heat exchanger can be, for example, less than 1:2, preferably less than 1:4, more preferably less than 1:8, and under certain circumstances even less than 1:16.A plate heat exchanger within the meaning of these documents, however, does not refer to what is sometimes called a design in which a heat exchanger is composed of several corrugated plates in such a way that a medium to be heated flows in one space and a heat-emitting medium flows in the other space. A plate heat exchanger within the meaning of these documents preferably contains only one fluid chamber, so it is only suitable for heat transfer within one fluid, but not between two fluids. The heat exchanger is preferably a sheet-metal heat exchanger.

[0033] According to exemplary embodiments, the heat exchanger can preferably be constructed in two parts. It can have a base part and a cover part, which, together with the turbulator described below, are connected to one another by a material fit and, if necessary, also by a form-fitting and / or force-fitting connection, in particular by soldering or welding. The base wall, together with the side walls, can be part of the base part, and the cover wall can be part of a cover part, preferably designed as a flat plate. The cover wall and cover part can be identical.

[0034] The turbulator can preferably have a filigree structure and can include a grid structure. It is preferably in thermally conductive contact with at least the cover wall in order to conduct the heat transferred via this into the grid structures around which the fluid flows, so that the fluid absorbs the heat efficiently due to the large contact area between the fluid and the grid. The turbulator can change the fluid flow in the interior space towards a turbulent flow, so that the fluid flowing through the interior space is better mixed, thereby further increasing the efficiency of the heat exchanger. The grid-like turbulator can, for example, be made from a single sheet of metal. For production, slots can first be punched into the sheet of metal. Subsequently, a grid-like structure of the turbulator can be created, for example, by "accordion-like" folding.The turbulator can be made of the same material as the base and / or cover wall. The turbulator is preferably also attached to the base wall in order to avoid dynamic bulging and thus a change in the hydrodynamic conditions at the high pressures of the fluid flowing through. The material thickness of the turbulator can, for example, correspond to the wall thickness of the base and / or cover wall, or at least be in a similar range. As an alternative to using a continuous lattice-like turbulator, it can also be provided that the base wall and / or the cover wall have a plurality of projections which, when assembled, protrude into the interior and thus also form a lattice-like turbulator there. Other embodiments for a heat-transfer mechanism are also possible.The turbulator and the heating element can preferably essentially coincide in their surface coverage in a plan view in a direction perpendicular to the cover wall, ie they completely overlap each other.

[0035] According to one embodiment, the flow deflection device is designed as a concave, outwardly directed bulge in one or more of the boundary walls, expanding the fluid chamber. This bulge then forms a channel in the heat exchanger area, bordered internally by the turbulator, through which the fluid can flow over the turbulator. This is, in a sense, a flow bypass that influences the overall flow distribution within the turbulator.

[0036] The embodiments of the invention make it possible to dispense with essentially turbulence-free inlet or outlet areas, thus enabling a very compact, flat design of the heat exchanger. Space is actually only required internally for the heat exchanger area, into which the fluid inlets and outlets can open directly. However, this usually means that there is no longer any free space for pre-distribution of the flow, so that the heat exchanger can no longer be flowed through homogeneously (parallel flow with essentially the same cross-section). However, more complex geometries are now possible. For example, the fluid inlets no longer need to be arranged at opposite ends, but can introduce the fluid laterally, in particular perpendicular to the plane defined by the cover wall, directly into the heat exchanger area, where it then spreads from the inlet point.Due to the symmetry, the flow is usually no longer homogeneous per se, but can, for example, be directed partly toward the opposite fluid outlet, but partly also initially toward the side walls (before this flow also turns toward the fluid outlet). This is where the channels formed by the curvature come into play, influencing the flow conditions in such a way that a more even mixing of the flow components occurs, thus reducing temperature differences. In particular, these channels achieve a beneficial reduction in pressure loss in the heat exchanger area.

[0037] A particularly advantageous embodiment provides that the concave, outwardly directed curvature expanding the fluid chamber is a dome formed in the bottom wall and forms a channel above the turbulator adjacent to the fluid inlet or the fluid outlet. Through this dome, the fluid can locally flow over the turbulator and thus be efficiently introduced either from the fluid inlet into the turbulator or, conversely, discharged from the fluid outlet.

[0038] The dome can preferably extend from the fluid inlet or the fluid outlet in a predetermined direction. In particular, it can extend toward a central region of the bottom wall. These embodiments have proven particularly advantageous, especially when the fluid outlet and / or the fluid inlet are aligned perpendicular to the plane of the heat exchanger or the cover wall, respectively, and are positioned on the bottom wall toward the corners of the latter.

[0039] Furthermore, according to a special embodiment, the cross-section of the dome can continuously decrease at greater distances from the fluid inlet or fluid outlet. This causes a continuous change in the flow conditions in the cross-section away from the inlet or toward the outlet. Preferably, a dome is assigned to each of the fluid inlet and the fluid outlet. Furthermore, the arrangement of the walls, the fluid inlets and outlets, and the domes is symmetrical, in particular mirror-symmetrical or point-symmetrical.

[0040] An alternative embodiment (or one that can advantageously be combined with the dome in the heat exchanger) provides for the concave, outwardly directed curvature that expands the fluid chamber to be designed as an overflow channel formed in one of the side walls that extend longitudinally or parallel to a connecting line between the fluid inlet and the fluid outlet. This enables an overflow between an edge of the turbulator and the side wall, which allows for a faster flow of fluid components that have already traveled a longer distance through the turbulator, so that they can be directed to a location for faster mixing. In particular, this also reduces undesirable pressure loss.

[0041] Instead of, or advantageously in addition to, an outward curvature that reduces the pressure loss in the heat exchanger, the flow deflection device can also be a section that narrows the cross-section of the fluid chamber in a direction perpendicular to the connecting line between the fluid inlet and the fluid outlet. This intervention per se leads to an increased pressure loss. However, further advantages can arise. Liquid heaters are operated at predetermined operating points, which are heating output, fluid outlet temperature, and volume flow. The latter does not necessarily have to be known for the control system, since the heating output is generally regulated via the temperature. For heaters for high volume flows (e.g.900 L / h or higher), the geometry (size, design) of the heat exchanger can already be designed in such a way that the feature of a flow diverter that narrows the cross-section is not even necessary, because in this case, a high volume flow already ensures sufficient flow through the interior or the heat exchanger area. Now, practical electric heaters with a lower volume flow (e.g. 600 L / h) can use the same heat exchanger in basic design, i.e., the same geometry (size, design). This saves development costs and enables the production of identical components in larger volumes. Furthermore, it offers vehicle manufacturers the opportunity to provide the same installation space for the respective vehicle type, whereby the selection of the specific volume flows of the liquid heater only needs to be made at the time of installation. In this case, i.e.With the volume flow now lower, the flow conditions in the interior of the heat exchanger can change significantly. In this case, it has now been shown that narrowing the cross-section by measures (narrowing section), which only need to be carried out on individual parts of the heat exchanger shortly before assembly, brings about the desired effects, namely better mixing of the fluid components, with the result that larger outer areas of the surface are available for the placement of a temperature sensor. As a concrete embodiment, the section can be formed in the turbulator. The turbulator can have a generally grid-like structure as described, wherein the section is provided in particular by a connected, bar-like closed area of ​​grid points.In the example of the punched sheet metal with slots, in which slotted lamellae are created that are alternately pressed outwards and inwards during production in the accordion-like folded state of the sheet metal, the corresponding lamellae can be subsequently pushed back before inserting and securing the turbulator sheet in the interior (on the cover part and / or the base part) to form a closed bar that, when inserted, is perpendicular to the otherwise existing flow direction. The flow is thus redirected. This variant has the advantage that only one insert needs to be modified, and this is done without great effort.

[0042] According to further embodiments not shown, such a bar can be formed by just two or three adjacent slats that are pressed in the same way to one or the other side. Alternatively or additionally, several such small bars can be combined alternately with permeable areas of unchanged slats (grid locations) to implement a bar with a certain degree of permeability, i.e. with increased flow resistance. For example, in the alternating arrangement of slats, a specific slat can be pressed towards the opposite side to form a bar of two or three together with one or two adjacent slats. The next but one slat in the row transverse to the flow direction, in contrast, remains pressed towards the opposite side, allowing flow to pass through. The row then continues as described above with a bar of two or three.It should be noted that it is obvious to the person skilled in the art that, due to the design, for example due to punching to form the generally grid-like structure, the slats or grid points positioned similarly in a bar can also result in a limited permeability for the flow between them.

[0043] Alternatively or additionally, the section can be provided by an embossed portion of the bottom wall extending from a side wall, particularly if the bottom wall is part of a deep-drawn mold that forms the bottom part. In particular, the embossed portion can be formed in a side wall extending longitudinally or parallel to a connecting line between the fluid inlet and the fluid outlet.

[0044] According to another aspect of the present invention, an electric heating device, in particular an electric liquid heater for a vehicle, can have at least one heating element which is designed to convert electrical energy supplied to it into heat, and a heat exchanger which is in thermal connection with the at least one heating element and is designed to transfer heat supplied to it by the heating element to a fluid flowing through it.

[0045] The heat exchanger is a heat exchanger and accordingly has a flat fluid chamber defining a heat exchanger region therein. Furthermore, the heat exchanger has a fluid inlet, a fluid outlet, and a turbulator for heat transfer arranged in the fluid chamber, wherein the fluid chamber is formed by boundary walls.

[0046] As described above, the heat exchanger has a cover wall, which can be part of a flat cover part, preferably designed as a plate. The cover wall or cover part is thermally connected to the heating element for heat transfer. The electrical heating device also has a temperature sensor. This can be arranged on a circuit board, which is also thermally connected to the cover part or cover wall.

[0047] This aspect is particularly advantageous because the circuit board is thermally connected to the cover wall in a similar way to the heating element. This means that the temperature of the fluid can also be measured approximately at or on the circuit board. The circuit board can also be configured to accommodate power switching elements for operating the heating element, so that the heat generated during operation due to the switching processes can also be conducted into the fluid. This creates a synergy effect in that the circuit board itself is advantageously already provided and is also used to implement a temperature sensor with very little effort, because the connections for electrical contact are already available on site or can be implemented with little effort.

[0048] According to embodiments, this aspect can be combined with the above aspects and exemplary embodiments, because they also provide opportunities to no longer place the temperature sensor in the fluid or at the fluid outlet. However, installing the temperature sensor on the circuit board without a current diversion device, but with the aforementioned advantages, is equally possible.

[0049] In a further development of the present aspect, a control device can be provided which is connected to the temperature sensor and is configured to determine an actual temperature of the fluid exiting from the fluid outlet during operation based on a temperature value detected by the temperature sensor.

[0050] In a further development, the control unit can be configured to read in an offset value for the temperature and add this value to the detected temperature value. This offset value preferably corresponds to a difference from the actual temperature value present in the fluid outlet and can be determined experimentally in advance and stored in a memory to which the control unit has access or is part of the control unit. The offset value is preferably dependent on the detected temperature value and / or the current heating output. This can be implemented, for example, within the framework of a look-up table or through parameters in a simple calculation formula.

[0051] The invention described above will now be explained by way of example with reference to the accompanying drawings using a preferred embodiment.

[0052] They show:

[0053] Figure 1 is a perspective view of a heat exchanger of an electric heating device 1 according to an embodiment of the invention;

[0054] Figure 2 is a schematic perspective view of only a cover part of the heat exchanger from Fig. 1, with a heating element formed thereon;

[0055] Figure 3 is a plan view of the cover part of Fig. 2 in greater detail;

[0056] Figure 4 is a schematic cross-sectional view of the electric heating device;

[0057] Figure 5 is a perspective view of only a bottom part of the heat exchanger from Fig. 1, with inserted turbulator;

[0058] Figure 6 is a perspective view of a section of the turbulator from Fig. 5;

[0059] Figure ? a cross-section through the heat exchanger from Fig. 1 , wherein the fluid inlet and the fluid outlet are shown in a partial side view;

[0060] Figure 8 shows a cross-section through the heat exchanger from Figure 1, with the fluid inlet and the fluid outlet also shown in cross-section; Figure 9 shows the cross-section from Figure 8 in an enlarged view, with a VDA nozzle with a nominal diameter of 16 for the fluid inlet;

[0061] Figure 10 like Figure 9, but for a different VDA nozzle with nominal diameter 20 for the fluid inlet;

[0062] Figure 11 like Fig. 9 or 10, but for a classic nozzle with freely selected contour (for mounting with hose clamp), with diameter 19 mm for the fluid inlet;

[0063] Figure 12 shows the turbulator from Fig. 6;

[0064] Figure 13 shows a modification of the turbulator of Figure 12, wherein a grating period in the main flow direction has been increased; and

[0065] Figure 14 shows a modification of the turbulator from Figure 13, in which a grating period in the bypass direction has been increased.

[0066] In the following description of preferred embodiments, it should be noted that the present disclosure of the various aspects is not limited to the details of the construction and arrangement of the components as shown in the following description and in the figures. All embodiments, even those not shown in the figures, can be practiced or carried out in various ways. It should also be noted that the phraseology and terminology used herein is used for the purpose of specific description only and should not be construed as such by one skilled in the art.Furthermore, in the following description, the same reference numerals in the figures denote the same or similar features or objects, so that in some cases a repeated detailed description of the same is omitted in order to maintain the compactness and clarity of the illustration.

[0067] Figure 1 shows a perspective view of a heat exchanger 10 of an electric heating device 1 according to an embodiment of the invention. The heat exchanger 10 comprises a base part 16 and a cover part 18, which form a brazing assembly and enclose a fluid chamber 120 (see Figures 4, 5, 7, and 8), as well as a fluid inlet 12 and a fluid outlet 14. Furthermore, a turbulator 40 is provided in the fluid chamber 120 (see schematically in Figure 4, and in Figure 5 in the partially open state of the fluid chamber).

[0068] The cover part 18 and the base part 16 can be made of steel or aluminum, preferably aluminum. The terms base part and cover part are chosen subjectively to distinguish them from one another and could also be used interchangeably. The chosen terminology is not to be interpreted restrictively. The base part 16 is made from a plate that is deep-drawn on the inside. It thus comprises a roughly cuboid-shaped, deep-drawn region 17 with side walls 161, 162, 163, and 164 as well as a substantially flat, preferably planar base wall 165, and a plate-shaped, completely planar edge region 171. In contrast to a strict cuboid shape, the side walls 161-164 are slightly inclined, and the edges are rounded.

[0069] The cover part 18 is formed by a plate that is completely flat in the illustrated embodiment. The cover part 18 forms a cover wall 181. The base part 16 and the cover part 18 are soldered together at the edge, in the completely flat areas on both sides, sealing the interior space or fluid chamber 120. The cover wall 181, the base wall 165, and the side walls 161-164 connecting them form the fluid chamber 120 on the inside.

[0070] In Fig. 2, the outer side of the cover part 18 or the cover wall 181 is shown in a reversed state compared to the orientation in Fig. 1. In this purely schematic illustration, a heating element 20 is shown, which is mounted on a surface of the outer side and is arranged opposite the interior space or the fluid chamber 120. The heating element 20 of Fig. 2 is not drawn to scale.

[0071] Fig. 3 shows the outer side of the cover part 18 or the cover wall 181 in greater detail. The heating element 20 is formed by three heating element units 60a, 60b, 60c, each comprising a preferably ceramic substrate 42 on which heating conductor tracks 50 are formed using a screen printing process. These heating conductor tracks are formed in a meander shape using insulation interruptions in a heating conductor layer made of a resistance alloy. Other shapes of heating conductor tracks and other types of heating elements, such as the variants described above, are also possible.

[0072] Connection points of the conductor tracks 50 are connected via connecting lines 44 to a printed circuit board 48, on which power switching elements (not shown in Fig. 3) are arranged, with which the heating element units 60a-c can be operated (switched, e.g., PWM). The power switching elements can be switched by a control unit 46 of the electric heating device 1 using connecting lines 47. Furthermore, a power supply is provided from the control unit 46 via connecting lines 47.

[0073] Fig. 4 shows a schematic representation of the electrical heating device 1 described so far in cross section.

[0074] Fig. 1 and Fig. 5 show flow deflection devices formed in the base part 16 and in the turbulator 40. These are domes 30, 31, an overflow channel 32, a stamped portion 34, and a bar-like closed region 405 of grid points in the turbulator 40. The domes 30, 31, the overflow channel 32, and the stamped portion 34 are formed in the base part 16.

[0075] The dome 30 extends from the fluid inlet 12, located in a region near a corner of the bottom wall 165, toward a central portion of the bottom wall 165. The turbulator 40 is provided as a grid punched from sheet metal and folded in an accordion-like manner, which, as shown in Fig. 6, has a plurality of lamellae 401 alternately pressed in and out. The grid is regularly constructed and has a constant thickness across its length and width. The dome 30, which is configured as an outwardly directed, i.e., concave, bulge in the bottom wall 16, therefore forms a shallow, confined channel above the turbulator 40, through which the fluid F is fed into the underlying turbulator 40. A cross-section of the dome decreases continuously starting from the fluid inlet 12.The dome 31 is formed in a similar manner and in a mirror-symmetrical arrangement on the side of the fluid outlet 14, which is located near another corner of the bottom wall 165. The two corners are connected by the side wall 164.

[0076] As can be seen in Figs. 7 and 8, the fluid inlet 12 has an inlet nozzle with a first central axis Z1 and the fluid outlet 14 has an outlet nozzle with a second central axis Z2. The first central axis Z1 and the second central axis Z2 are aligned substantially perpendicular to a plane defined by the flat fluid chamber 120 and in particular the cover wall 181. The flat domes 30, 31 consequently extend in a direction perpendicular to the central axes Z1 and Z2. The first central axis Z1 and the second central axis Z2 extend as an extension through the turbulator 40. Because the fluid inlet 12 and the fluid outlet 14 are no longer in the plane of the base or cover wall, a very compact and particularly flat structure is created without a separate inlet or outlet area. At this point, the domes 30, 31 appear, but they only form a flat channel that allows flow over the turbulator 40.

[0077] Due to the interaction of the domes 30, 31 with the turbulator 40 (formation of a channel between them), the domes 30, 31 are arranged in the heat exchanger region. This is characterized by the overlapping projection of the turbulator 40 and the heating element 20 in plan view (along the center axes Z1, Z2 of the fluid inlet 12 and the fluid inlet 14, respectively), with the circuit board 48 also acting as a heat-dissipating element. For this reason, the fluid chamber 120 is defined entirely as the heat exchanger region in this case.

[0078] It should be noted that the cross-section in Figures 7 and 8 is along line AA in Figure 1. This does not intersect any of the flow deflection devices except the area 405 of grid sites in the turbulator 40, so that these, although present, are not visible in Figures 7 or 8.

[0079] Figures 9 to 11 show, purely by way of example, variations of the nozzle for the fluid outlet 14. The fluid inlets 12 are each provided with a correspondingly analogous nozzle design. Figure 9 once again shows the nozzle of the fluid outlet 14 from Figures 7 and 8 in greater detail. Due to the viewing direction in Figures 9 - 11, which is opposite to Figures 7 and 8, along the cross-sectional line AA in Figure 1, the dome 30 can now also be seen. Also clearly visible is a collar 166, which is formed in the bottom wall 165 of the deep-drawn shape of the base part 16 and accommodates a lower, for example cylindrical, section of the nozzle of the fluid outlet 14.

[0080] The collar 166 has an inner diameter of, for example, 22 or 24 mm. In particular, the nozzle is a separate component in the embodiments. This design makes it possible to use different types or sizes of nozzles (especially with different inner diameters) without having to fundamentally modify the heat exchanger for the respective application. The nozzles can advantageously be attached only during assembly of the heat exchanger, depending on customer requirements, so that "variant creation" only needs to take place in a very last process step. The available nozzles only need to have the lower section with an outer diameter matching the inner diameter of the collar 166, but can otherwise differ from one another as desired.The fastening of the nozzle to the base component 16 can be soldered to the material of the nozzle for the various nozzles in the same step as the base part 16 to the flat, plate-shaped cover part 18.

[0081] The nozzle of the fluid outlet 14 in Fig. 9, for example, is a VDA nozzle with an inner diameter (nominal width) of 16 mm. In this particular case, the inner diameter of the nozzle tapers from the receiving section to the opening for which the nominal width is specified. Figure 10 shows a variation (fluid outlet 14') in the form of a VDA nozzle with an inner diameter (nominal width) of 20 mm.

[0082] Fig. 11 shows the same heat exchanger as in Figs. 9 and 10 with a classic nozzle with a hose clamp (fluid outlet 14", which does not correspond to a VDA nozzle). Here, it is clearly visible that not only the inner diameter (19 mm) can be different, but also the other design of the nozzle.

[0083] As can be seen in Fig. 1 and 5, an elongated overflow channel 32 is arranged on the side wall 162 of the deep-drawn area 17 of the base part 16, which also allows a (here lateral) flow over or around the turbulator 40.

[0084] Furthermore, starting from a central region of the opposite side wall 164, approximately midway between the fluid inlet 12 and the fluid outlet 14, the bottom wall 165 is provided with an embossed portion 34 (as an example of a flow deflection device), so that a contact area with the cover wall 181 is locally enlarged there. This causes a narrowing of the cross-section of the fluid chamber, thereby changing, i.e., influencing, the flow guidance in the fluid chamber.

[0085] As can be seen in Fig. 5, a grid row in the turbulator 40 is closed off in a bar-like manner, extending from the embossed portion 34. This bar-like closed region 405 of grid points extends into the center of the fluid chamber 120, which leads to a further narrowing of the cross-section available to the flow, so that the flow guidance in the fluid chamber is further changed, i.e., influenced. The embossed portion 34 and the bar-like closed region 405 of grid points in the turbulator 40 lead to a throttling of the pressure.

[0086] The flow deflection devices shown in Figs. 1 and 5, in combination, create a specific flow field in the fluid chamber 120. Other combinations, additions, or omissions also have a significant influence on the flow pattern. They can be adjusted through simulation to achieve good mixing depending on the operating point, thus making additional areas on or near the surface of the heat exchanger available for temperature sensing, with a temperature difference of only 2 °C or less from the fluid outlet temperature.

[0087] 3 and 4 show that a temperature sensor 52 is arranged on the circuit board 48. This sensor detects the temperature and transmits it to the control unit 46 via a connecting line 49. Reference numeral 54 denotes lead frames that provide portions of the connecting lines 45, 47, and 49 to / from the control unit 46. Based on the detected temperature, the control unit 46 can adjust the control of the power switching elements (not shown) on the circuit board 48. As described, the control unit 46 can determine the actual fluid outlet temperature by adding a stored offset value, possibly also using a lookup table.

[0088] Figures 12-14 show another example of a flow deflection device. Figure 12 shows the turbulator 40 from Figures 5 or 6 as a starting point. In Figure 13, in a main flow direction X, the pitch or grating period is increased from Px1 (Figure 12) to Px2 (Figure 13), thereby reducing the flow resistance in this direction. Furthermore, in Figure 14, in a secondary flow direction Y, the pitch or grating period is increased from Py1 (Figure 12) to Py2 (Figure 14), thereby reducing the flow resistance in this direction as well. The effect is similar to that of overflow channels when applied locally.

[0089] The features of the invention disclosed in the above description, in the drawings, and in the claims can be essential for the realization of the invention both individually and in any combination. This applies in particular to a cumulative consideration of the flow deflection devices (as shown) as well as to the implementation of the same individually. Furthermore, the temperature sensor can be arranged at positions other than those shown schematically in Fig. 4 and specifically in Fig. 3, in particular on or near an outer surface of the heat exchanger that does not correspond to the circuit board 34, but also is not directly adjacent to the fluid outlet. In other embodiments, the temperature sensor can be provided near or directly adjacent to the fluid outlet, or it can be omitted entirely. List of Reference Symbols

[0090] 1 electric heater, liquid heater

[0091] 10 heat exchangers, plate heat exchangers

[0092] 12 Fluid inlet

[0093] 14, 14', 14" fluid outlet

[0094] 16 Base part

[0095] 161-164 side walls

[0096] 165 floor wall

[0097] 166 Collar for nozzle in floor wall

[0098] 17 deep-drawn area

[0099] 171 flat edge area

[0100] 18 Lid part

[0101] 181 cover wall

[0102] 20 heating element

[0103] 30 Cathedral

[0104] 31 Cathedral

[0105] 32 overflow channel

[0106] 34 Embossing

[0107] 36 circuit board

[0108] 40, 40a Turbulator

[0109] 40b Turbulator with increased pitch (main flow direction)

[0110] 40c Turbulator with increased pitch (sidestream direction)

[0111] 401 slat

[0112] 405 bars

[0113] 42 Substrat

[0114] 44 Connecting cable (circuit board - heating element)

[0115] 45 Connecting cable (control unit - circuit board: control signals for switches)

[0116] 46 Control unit

[0117] 47 Connecting cable (control unit - circuit board: power supply)

[0118] 48 circuit board

[0119] 49 Connecting cable (control unit - circuit board: temperature detection)

[0120] 50 heating conductor track

[0121] 52 Temperature sensor

[0122] 54 punched grids

[0123] 60a-c heating element unit

Claims

Claims 1. An electric heating device (1), in particular an electric liquid heater for a vehicle, comprising: a heating element (20, 60a, 60b, 60c) configured to convert electrical energy supplied to it into heat; and a heat exchanger (10) thermally connected to the heating element (20, 60a, 60b, 60c) and configured to transfer heat supplied to it by the heating element (20, 60a, 60b, 60c) to a fluid (F) flowing through it;wherein the heat exchanger (10) has a flat fluid chamber (120) defining a heat exchanger region, a fluid inlet (12), a fluid outlet (14) and a turbulator (40) for heat transfer, which is arranged in the fluid chamber (120), wherein the fluid chamber (120) is formed by boundary walls (161 - 165, 181), wherein within the heat exchanger region of the fluid chamber (120), in particular on the turbulator (40), and / or in a region of the boundary walls which is opposite the turbulator, at least one flow deflection device is formed, which is designed to influence a flow guidance of the fluid through the fluid chamber.

2. Electric heating device (10) according to claim 1, wherein the boundary walls (161 - 165, 181) forming the flat fluid chamber (120) comprise a cover wall (181), a bottom wall (165) opposite the cover wall (181) and narrow side walls (161 - 164) connecting them, wherein the fluid inlet (12) and the fluid outlet (14) are formed in the bottom wall (165).

3. Electric heating device (1) according to claim 1, wherein a further flow deflection device is provided, which is a concave, outwardly directed curvature in one or more of the boundary walls (161 - 165, 181) which widens the fluid chamber (120) and forms a channel which is delimited on the inside by the turbulator (40) and through which the fluid (F) can flow over the turbulator (40).

4. Electric heating device (1) according to claim 3, wherein the concave, outwardly directed curvature extending the fluid chamber (120) is a dome (30, 31) which is in the bottom wall (165) is formed and forms a channel above the turbulator (40) adjacent to the fluid inlet (12) or the fluid outlet (14).

5. Electric heating device (1) according to claim 4, wherein the dome (30, 31) extends in a predetermined direction starting from the fluid inlet (12) or the fluid outlet (14).

6. Electric heating device (1) according to claim 5, wherein the dome (30, 31) extends towards a central region of the bottom wall (165).

7. Electric heating device (1) according to claim 5 or 6, wherein a cross-section of the dome (30, 31) continuously decreases towards greater distances from the fluid inlet (12) or fluid outlet (14).

8. Electric heating device (1) according to one of claims 4 to 7, wherein preferably both the fluid inlet (12) and the fluid outlet (14) are each assigned a dome (30, 31).

9. Electric heating device (1) according to claim 3, wherein the concave, outwardly directed bulge expanding the fluid chamber (120) is an overflow channel (32) formed in one of the side walls (162) extending longitudinally or parallel to a connecting line between the fluid inlet (12) and the fluid outlet (14).

10. Electric heating device (1) according to claim 2, wherein the flow deflection device is a section narrowing a cross section of the fluid chamber in a direction perpendicular to the connecting line between the fluid inlet (12) and the fluid outlet (14).

11. Electric heating device (1) according to claim 10, wherein the section is formed in the turbulator (40), the turbulator having a generally grid-like structure, the section being provided by a region (405) of grid locations, the region preferably being formed in a continuous and / or bar-like manner and / or further preferably being closed.

12. Electric heating device (10) according to claim 10, wherein the section is provided by an embossment (34) of the bottom wall (165) extending from a side wall (164), preferably a side wall (164) extending longitudinally or parallel to a connecting line between the fluid inlet (12) and the fluid outlet (14).

13. Electric heating device (1) according to one of claims 1 to 9, wherein the cover wall (181) is part of a flat cover part (18), preferably designed as a plate, which is thermally connected to the heating element (60a, 60b, 60c) for transferring the heat, further comprising a temperature sensor (52) which is arranged on a printed circuit board (48) which is also thermally connected to the cover part (18).

14. Electric heating device (1) according to claim 13, further comprising a control unit (46) which is connected to the temperature sensor (52) and is configured to determine an actual temperature of the fluid (F) emerging from the fluid outlet (14) during operation on the basis of a temperature value detected by the temperature sensor (52), wherein the control unit (46) is preferably configured to read in an offset value for the temperature and to add this value to the detected temperature value, wherein the offset value is further preferably dependent on the detected temperature value and / or the current heating power.

15. Electric heating device (1) according to one of the preceding claims, wherein the fluid inlet (12) has an inlet nozzle with a first central axis (Z1) and the fluid outlet (14) has an outlet nozzle with a second central axis (Z2), wherein the first central axis (Z1) and the second central axis (Z2) are aligned substantially perpendicular to a plane defined by the flat fluid chamber (120), and / or wherein the first central axis (Z1) and the second central axis (Z2) extend in an extension through the turbulator (40).

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