Plate heat exchangers

Abstract

Plate heat exchanger (10), in particular for an electrically operated vehicle heater (12), comprising - a fluid inlet (14) and a fluid outlet (16); - a bowl-shaped base part (18); - a cover part (20) covering the bottom part (18), wherein the bottom part (18) and the cover part (20) in the assembled state form a cavity (22) which defines a heat exchanger area for a fluid (24) to be heated; and - at least one electrical heating element (26) arranged flat on the lid part (20).

Description

[0001] The present invention relates to a plate heat exchanger, in particular for an electrically operated vehicle heater.

[0002] Modern vehicles, especially those without a combustion engine, often lack a suitable waste heat source, rendering conventional vehicle heaters that utilize the waste heat from a combustion engine impractical. To address this problem, it is already known to provide an electric heating source, thus creating an electrically operated vehicle heater. Although the basic design of such electrically operated vehicle heaters is known in principle, further improvements are needed, particularly regarding their efficiency and power density, as additional weight or increased power consumption directly reduces the already limited range of a vehicle without a combustion engine. A device with a planar electric heating element is already known from DE 10 2012 207 305 A1.The heat exchanger used comprises a housing with a heat exchanger core, which, together with a cover plate, defines several parallel flow channels for a fluid to be heated. The fluid flows into the heat exchanger at an inlet and out at an outlet. Furthermore, other plate-shaped heat exchangers, which are combined into larger cylindrical units, are known from US 2008 / 0314574 A1 and DE 602 05 645 T2.

[0003] The present invention is based on the objective of providing a lightweight, compact and at the same time efficient heat exchanger.

[0004] This document describes a plate heat exchanger, specifically designed for electrically operated vehicle heating systems. The plate heat exchanger comprises a fluid inlet and a fluid outlet. It also includes a shell-shaped base and a cover that protects the base. The cover may also be shell-shaped. When assembled, the base and cover form a cavity that defines a heat exchanger area for the fluid to be heated. An electric heating element is mounted across the surface of the cover. Additional electric heating elements may also be provided; for example, another electric heating element may be mounted across the surface of the base. The heat exchanger area can be located between the inlet and outlet areas.The fluid to be heated first enters the inlet area, flows from there into the heat exchanger area, and finally reaches the outlet area. The inlet and outlet areas can, for example, be formed directly by the cavity defined by the bottom and top sections. Alternatively, the inlet and outlet areas can be formed separately from the bottom and top sections by additional components that connect directly to the cavity defined by these sections. It is also possible for the inlet and / or outlet areas to be formed solely by the top or bottom section, respectively. The fluid inlet can open into the inlet area or be considered part of it. The outlet area can continue into the fluid outlet or be considered part of it.The electric heating element can, in particular, define the heat exchanger area of ​​the cavity formed by the base and cover parts by its spatial extent. The height of the cavity can be, for example, 2.5 mm to 6 mm, preferably 4 mm. The electric heating element can be arranged flat on an outer surface of the cover part facing away from the cavity, so that the area of ​​the cavity covered by the electric heating element can be considered the heat exchanger area. The electric heating element can, for example, be manufactured directly on the cover part in the form of a resistive conductor track using a coating process. The coating process can, for example, involve applying a resistive paste or a plasma coating process. The electric heating element can, in particular, be the sole heat source of the electrically operated vehicle heater.The base and lid sections can be made, for example, of thin aluminum or steel sheet. The wall thickness of the base and / or lid section can be less than 4 mm, preferably less than 3 mm, and particularly preferably between 1 mm and 2 mm. The plate heat exchanger can, in particular, have exactly a single plate-like cavity in which the fluid is heated. The fluid inlet and outlet, as connection fittings known to those skilled in the art, can be inserted into designated recesses in the base and / or lid section and fixed in a fluid-tight manner. This fixing can be achieved, for example, by means of a soldering or welding process.

[0005] The electric heating element can comprise one or more resistive conductor tracks. Connection contacts can be provided to couple the electric heating element to a power source. The electric heating element can, in particular, be a non-intrinsically safe electric heating element. However, it is also conceivable that the electric heating element is designed as an intrinsically safe electric heating element, for example, in the form of PTC heating elements, which are manufactured separately from the plate heat exchanger and only subsequently, after their manufacture, fixed to the cover part.

[0006] It may be provided that a grid-like turbulator is inserted into the cavity. The turbulator can modify the fluid flow in the cavity, creating a turbulent flow so that the fluid flowing through the cavity is better mixed, thereby increasing the efficiency of the heat exchanger. The grid-like turbulator can, for example, be made from a single sheet of metal, in which slots can first be punched and then a grid-like structure created by folding it like an accordion. The turbulator can be made of the same material as the bottom and / or the top section. The material thickness of the turbulator can, for example, correspond to the wall thickness of the bottom and / or top section or at least be within a similar range.As an alternative to inserting the turbulator, it can also be provided that the bottom part and / or the lid part have a multitude of extensions which, in the assembled state, project into the cavity and form the grid-like turbulator there.

[0007] Furthermore, the turbulator can be positioned fluidically between the fluid inlet and outlet. In particular, the turbulator can be located within and confined to the heat exchanger area. This allows the internal flow resistance of the plate heat exchanger to be kept as low as possible. Additionally, the turbulator's direct contact with the cover plate can improve heat transfer into the cavity.

[0008] Advantageously, the base and top sections can be designed as sheet metal parts. Sheet metal parts are easy and inexpensive to manufacture, allowing for cost-effective production of the resulting plate heat exchanger. Furthermore, sheet metal parts have a thinner wall thickness and therefore a lower weight, particularly compared to conventional die-cast parts. This weight saving also has a positive impact on the final plate heat exchanger.

[0009] It may also be provided that the bottom section and / or the cover section have corrugations that project into the cavity. By providing corrugations, in particular corrugations that are embedded in the bottom section and / or the cover section at the interface between the inlet area and the heat exchanger area and / or at the interface between the outlet area and the heat exchanger area, a uniform fluid inlet and outlet into and out of the heat exchanger area can be achieved. Such a uniform fluid inlet and outlet is not a given due to the various possible flow paths, which can differ significantly in length, but can be achieved through the throttling effects caused by the corrugations.For example, the grooves can extend to different depths into the cavity in order to ensure a uniform fluid flow through the heat exchanger area due to the resulting locally differing throttling effects at different spatial locations.

[0010] It may be provided that the base and / or the lid are at least partially solder-plated on their facing surfaces when assembled. Solder plating of the base and lid on their facing surfaces in the assembled state enables a particularly simple, fluid-tight connection between the base and lid by brief heating, whereby the solder melts and a metallurgical bond is created between the base and lid at all contact points.

[0011] It may therefore be designed so that the base part and the lid part are soldered together.

[0012] Furthermore, the turbulator, which is located between the bottom and top sections, may also be brazed to the bottom and / or top sections. Brazing the turbulator to the bottom and / or top sections significantly increases the mechanical stability of the plate heat exchanger, particularly its rigidity, so that it exhibits sufficient pressure resistance in the event of a failure, even with thin bottom and top wall thicknesses. Brazing can be performed on both the inserted turbulator and the turbulator formed by projections extending into the cavity.

[0013] A thermal insulation layer can be usefully provided, at least to cover the electrical heating element located on the cover. By providing a thermal insulation layer, which can be implemented, for example, in the form of thermally insulating polyurethane foam and / or a separately attached thermally insulating cover, the efficiency of the plate heat exchanger is further increased, as direct energy loss through unused heat radiation to the outside can be significantly reduced.

[0014] Advantageously, the bottom and / or top sections can have post-like indentations, so that the bottom and top sections touch each other in the area of ​​these indentations when assembled. The contact points created by the post-like indentations can also be brazed together, further improving the mechanical stability of the plate heat exchanger. The post-like indentations can be arranged, in particular, in the inlet and / or outlet areas, i.e., in areas where a turbulator is preferably not located. Furthermore, in addition to the grooves, the post-like indentations in the inlet and outlet areas can contribute to generating a uniform fluid flow in the heat exchanger area, for example, by selectively redirecting portions of the fluid flow towards the heat exchanger area.

[0015] The invention is explained below by way of example using a preferred embodiment.

[0016] They show: Fig. 1 a schematic representation of a vehicle with an electrically operated vehicle heater; Fig. 2 a three-dimensional external view of a plate heat exchanger; Fig. 3 a three-dimensional view of a floor section with an inserted turbulator; Fig. 4. A three-dimensional view of a turbulator; and Fig. 5 a side sectional view through a plate heat exchanger.

[0017] In the following drawings, identical reference symbols denote identical or similar parts.

[0018] Fig. Figure 1 shows a schematic representation of a vehicle 40 with an electrically operated vehicle heater 12. The vehicle can, for example, be a fully electric vehicle. The indicated vehicle 40 includes a power source 38 as its primary energy source, which is connected to the electrically operated vehicle heater 12 by means of connecting cables 42. The electrically operated vehicle heater comprises a plate heat exchanger 10 with an electric heating element 26 and thermal insulation 36.

[0019] Fig. Figure 2 shows a three-dimensional external view of a plate heat exchanger 10. The plate heat exchanger 10 shown comprises a fluid inlet 14 and a fluid outlet 16, wherein fluid 24 to be heated enters the plate heat exchanger 10 via the fluid inlet 14 and heated fluid 24 exits the plate heat exchanger 10 via the fluid outlet 16. In the figure, the fluid inlet 14 and the fluid outlet 16 are shown as lying in the plane of the plate heat exchanger 10. Alternatively to the one shown in Fig. However, in the configuration shown in Figure 2, the fluid inlet 14 and / or the fluid outlet 16 can also be realized at an angle to the plane of the plate heat exchanger 10, which may be advantageous depending on the available installation space.

[0020] The fluid inlet 14 empties into the Fig. The embodiment shown in Figure 2 features an inlet area that tapers away from the fluid inlet. Two indentations 44 with a wing-like profile are visible in the inlet area. These indentations project into the inlet area and deflect portions of the fluid 24 flowing into the inlet area towards the adjacent heat exchanger area. The heat exchanger area is located in Fig. 2 essentially below the electric heating element 26. The inlet area and the heat exchanger area are separated from each other by a groove 30, which also contributes to a uniform flow of the fluid 24 from the inlet area into the heat exchanger area. A groove 30 is also provided on the opposite side, i.e., at the end of the heat exchanger area where the fluid 24 flows into the adjacent outlet area. Furthermore, indentations 44 are also visible in the outlet area, which is separated from the heat exchanger area by the groove 30. The grooves 30 can, for example, be deeper closer to the fluid inlet 14 and the fluid outlet 16 to create a greater throttling effect there. The fluid inlet 14 and the fluid outlet 16 can, for example, be designed as conventional pipe fittings.

[0021] Fig. Figure 3 shows a three-dimensional view of a bottom section 18 with turbulator 28. The in Fig. The top-opening base section 18 shown in section 3 essentially corresponds to the lower part of the section shown in Fig. 2 completely enclosed plate heat exchanger 10. The bottom part 18 is designed in a shell-like manner and has a rim 46, which can be circumferential. The heat exchanger area is in Fig. 3 is recognizable by the already inserted turbulator 28, whereby the groove 30 is also visible, at least in the transition area between the heat exchanger area and the outlet area. Furthermore, the fluid inlets and outlets, each designed as simple pipe nozzles, as well as indentations 44 in the inlet and outlet areas, are visible. The illustrated turbulator 28 can be inserted or formed by a multitude of extensions on the bottom part 18 that project into the heat exchanger area. The extensions can, for example, be formed from the bottom part 18 by forming. It is also possible that the turbulator 28 is formed partially or completely by extensions of the cover part (not shown).

[0022] Fig. Figure 4 shows a three-dimensional view of a turbulator 28. The turbulator 28 can be manufactured from a single sheet. For example, during the manufacture of the turbulator 28, slots can first be punched into a sheet, and the punched sheet can then be compressed like an accordion to form the recognizable lattice structure. The in Fig. The turbulator 28 shown in section 4 can in particular be inserted into the cavity formed by the bottom part and the top part.

[0023] Fig.Figure 5 shows a side sectional view of the plate heat exchanger 10. The base section 18 with its rim 46 is visible. The base section 18 has post-like indentations in both the inlet and outlet areas. The inlet and outlet areas are each separated from the heat exchanger area located between them by grooves 30, and the turbulator 28 is visible in the heat exchanger area. The plate heat exchanger is closed at the top by a cover section 20, creating a cavity 22 between the base section 18 and the cover section 20. Opposing surfaces 32, 34 of the base section 18 and the cover section 20 are solder-plated. In the assembled state, the base section 18 and the cover section 20 are in contact, particularly in the area of ​​the rim 46, which can be continuous, in the area of ​​the post-like indentations 44, and at the upper and lower grid surfaces of the turbulator.By briefly heating the plate heat exchanger 10 to a temperature above the melting point of the solder used for plating, all contact points between the bottom part 18 and the top part 20 can be bonded together, so that the resulting plate heat exchanger 10 has high mechanical stability and is fluid-tight.

[0024] The features of the invention disclosed in the foregoing description, in the drawings and in the claims may be essential for the realization of the invention, both individually and in any combination. Reference symbol list 10 plate heat exchangers 12 electrically operated vehicle heaters 14 Fluid inlet 16 Fluid drainage 18 Base section 20 lid part 22 Cavity 24 Fluid 26 electric heating element 28 Turbulator 30 groove 32 surface 34 surface 36 thermal insulation 38 Power source 40 vehicles 42 Connection cable 44 Imprint 46 Rand

Claims

Plate heat exchanger (10), in particular for an electrically operated vehicle heater (12), comprising: - a fluid inlet (14) and a fluid outlet (16); - a bowl-shaped bottom part (18); - a cover part (20) covering the bottom part (18), wherein the bottom part (18) and the cover part (20) in the assembled state form a cavity (22) which defines a heat exchanger area for a fluid (24) to be heated; and - at least one electrical heating element (26) arranged over a surface on the cover part (20). Plate heat exchanger (10) according to claim 1, wherein a grid-like turbulator (28) is inserted into the cavity (22). Plate heat exchanger (10) according to claim 1, wherein the bottom part (18) and / or the top part (20) have a plurality of extensions which, in the assembled state, project into the cavity (22) and form a grid-like turbulator (28) there. Plate heat exchanger (10) according to claim 2 or 3, wherein the turbulator (28) is arranged fluidically between the fluid inlet (14) and the fluid outlet (16). Plate heat exchanger (10) according to one of claims 1 to 4, wherein the bottom part (18) and the top part (20) are designed as sheet metal parts. Plate heat exchanger (10) according to one of claims 1 to 5, wherein the bottom part (18) and / or the top part (20) has grooves (30) that project into the cavity (22). Plate heat exchanger (10) according to one of claims 1 to 6, wherein the bottom part (18) and the top part (20) are at least partially solder-plated on their mutually facing surfaces (32, 34) in the assembled state. Plate heat exchanger (10) according to claim 7, wherein the bottom part (18) and the top part (20) are soldered together. Plate heat exchanger (10) according to one of claims 1 to 8, wherein a thermal insulation (36) is provided which at least covers the electrical heating element (26) arranged on the cover part (20). Plate heat exchanger (10) according to one of claims 1 to 9, wherein the bottom part (18) and / or the lid part (20) has post-like indentations (44) so ​​that the bottom part (18) and the lid part (20) touch each other in the area of ​​the post-like indentations (44) in the assembled state.

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