Electric Fluid Heater

This application is a national phase application of, and claims priority to, International Application Number PCT/EP2023/066671, filed Jun. 20, 2023, entitled ELECTRIC FLUID HEATER, which claims priority to German Application Number 10 2022 128 258.9, filed Oct. 25, 2022, and German Application Number 10 2022 115 736.9, filed Jun. 24, 2022, the entire disclosures of each of which are incorporated herein by reference.

The present disclosure relates to an electric heater for fluids, specifically for liquids and more specifically for coolants.

In WO 2011/054970 A2, an electric fluid heater of this type is disclosed. Each of three tubular heating elements forms a plurality of coils along a joint coil axis, the coils being arranged in a housing through which the fluid flows. Thus, the fluid flows around the coils while being heated.

An embodiment with a fluid conduct is shown in which a tubular member is arranged in the housing inside the coils along the coil axis. The fluid to be heated first flows inside the tubular member along the coil axis, from there through passage recesses radially outwardly to the outer circumference of the tubular member and finally flows back at the outer circumference of the tubular member. Since the coils of the tubular heating elements are arranged at the outer circumference of the tubular member, also there the fluid for the first time contacts the coils. At the circumference of the tubular member, outer strips are provided which extend along the tubular member and against which the tubular heating elements can bear. The outer strips can also take over a flow conducting function.

A drawback of those electric fluid heaters is the transverse flow and the resulting limited performance density.

It is the object of the present disclosure to increase the performance density of electric fluid heaters of this type.

The object is achieved by an electric fluid heater comprising the features of an independent claim. Further advantageous configurations are the subject matter of the dependent claims.

The claimed electric fluid heater has a fluid-conducting housing in which at least one tubular heating element each with a plurality of coils is arranged. An inner region extending preferably along a coil axis is delimited by the coils. According to the disclosure, a displacer body arrangement having at least one displacer body at the outer circumference of which a flow region for the fluid is formed is provided in the inner region. In the flow region, also the coils are arranged. An interior space arrangement having at least one interior space of the displacer body arrangement is largely or completely separated from the flow region of the fluid in a fluid-tight manner. Largely separated means, for example, that at least 90%, preferably 95% of the interior space arrangement are surrounded by fluid-tight walls. A transverse flow (i.e., transversely with respect to the longitudinal axis of the coil) is largely or completely avoided. The active principle according to the disclosure thus is a minimization of the dead volume and a reduction of the flow cross-section. This results in an increase of the flow speed. The performance density of the fluid heater according to the disclosure is thus increased, consequently an increase of the heat transfer to the fluid is possible and/or a reduction of the available space and the device-related effort, resp., is possible. Thus, in a variant of the disclosure, the number of the tubular heating elements known from prior art is reduced.

In terms of manufacture, it is simple when the coils result in a circular-cylindrical shape, thus also allowing the inner region to take a circular-cylindrical shape.

In terms of device, it is simple when the displacer body arrangement bears against the coils.

When the housing has two opposite housing end walls which are preferably formed on a trough-like housing part, the displacer body arrangement extends over at least 90%, preferably over at least 95% of the distance of the two housing end walls to largely prevent the transverse flow. The displacer body arrangement can also bear against the two housing end walls.

In a first configuration variant of the disclosure simple in terms of manufacture, the (preferably exactly one) displacer body is a tube. The tube may be cylindrical, that is, it may have a uniform cross-section over its length, or it may have a reduction of diameter (constriction). If more than two tubular heating elements are provided, also more than one diameter reduction (constriction) can be provided.

If each of the end sections of the tube has a distance from the two opposite housing end walls, then two end-face lids each facing one of the two housing end walls are required to form the largely or completely fluid-tight wall according to the disclosure. As an alternative, an inner partition may also be present inside the tube. If more than two tubular heating elements are provided, even more than one inner partition can be provided.

In a second configuration variant of the disclosure, two or more displacer bodies are provided. The displacer bodies can be substantially equal in terms of simple manufacture, and can be arranged mirror-inverted to each other, for example, in the case of two displacer bodies.

In an embodiment of the second configuration variant, the displacer bodies are respective cups each of which has a bottom.

In the case of two cups, the two bottoms can face each other. In this case, the interior space arrangement has two separate interior spaces. Deviating therefrom, each bottom can also be arranged adjacent to a respective housing end wall. In this case, the two cups can be fastened to each other at their respective peripheral edges and/or can be nested. In this case, the two cups jointly form a tubular displacer body arrangement with the interior space arrangement in this case having exactly one interior space.

For particularly preferred developments, the at least one displacer body (e.g., a tube or cup) includes plural longitudinal ribs distributed over the cover. In the case of the cylindrical tube or in the case of the cup, the longitudinal ribs can extend over the entire length of the displacer body, e.g., when they form contact sections with all coils of the tubular heating elements, or when they form flow elements of maximum length. As an alternative, the longitudinal ribs may extend only over a partial length of the displacer body, for example when they form only contact sections for several coils of the tubular heating element.

There may also be provided exactly two opposite longitudinal ribs which, in a concrete embodiment, are shaped (are made uniform) so that an oval cross-section of the tube results.

In order to enable or improve the heat transfer to the fluid even from the inner faces of the coils, it is important that inner flow regions, for example in the form of longitudinal channels, through which the fluid can flow between the coils and the cover of the respective displacer body and can absorb heat are retained between the longitudinal ribs. Those inner flow regions also help reduce the undesired heat input into the interior space.

According to a preferred first basic principle of the disclosure, the interior space of the displacer body arrangement is a rest chamber into which the fluid penetrates. For this purpose, the displacer body arrangement has at least one opening. At least one of the openings may be an oblong hole or a slit.

For example, when taking into operation or after dismantling the fluid heater, it is important that air can escape from the housing and, in the case of the first principle of the disclosure, also from the rest chamber for the fluid, that consequently the rest chamber, too, is completely vented through the at least one opening.

The oblong hole and/or the slit can be introduced into the cover of the displacer body (tube or cup) and/or can extend approximately in parallel to a coil axis.

In the case of the cup, at least one of the openings can also be arranged on the bottom of the cup. In the case of the tube, at least one of the openings can also be arranged at the end-face cover of the tube so that the fluid can penetrate into and fill the rest chamber from a region between the end-face lid and the adjacent housing end wall. Said openings may be formed by slits disposed between triangular or circle segment-shaped sections of the lid.

According to a second principle of the disclosure, the displacer body arrangement can also be constituted by a fluid-tight tube so that the interior space of the tube is delimited against the fluid. In this case, the tube must be connected in a fluid-tight manner to the two housing end walls, and at least one of the housing end walls has an opening so that the interior space is connected to the ambient air.

illustrates an electric fluid heateraccording to the disclosure in a perspective view from below. The fluid heaterhas a housing in the fluid space of which the variants and embodiments of the displacer body arrangement according to the disclosure described with reference to the followingcan be realized.

The housing is composed of a trough-like housing partand a substantially flat housing lid. In order to seal the fluid space delimited in the trough-like housing partand the housing lidin a fluid-tight manner, said two housing parts,are joined cohesively, such as welded or soldered, to each other.

On a lower side of the trough-like housing part(at the top in), two portsfor the fluid are formed spaced apart from each other, one portthereof acting as an inlet and the other portthereof acting as an outlet. Further, two mounting tabsby which the fluid heatercan be mounted in a vehicle, for example, whose coolant is to be heated, are attached to the trough-like housing part.

The housing lidprojects on one side (on the right in) from the trough-like housing part. An electric high-voltage plugfor voltage supply of the fluid heateris screwed to and a ground studis welded to said projection. Moreover, an electric low-voltage plugthrough which the LIN communication with the fluid heateris performed is screwed to the projection.

An electronic housingwhich is mounted tightly to the housing lidby means of crimped tabs is provided on an upper side of the housing lidin the operating position remote from the fluid space. The crimped tabs are formed uniformly along the edge of the electronics housingand encompass the edge of the housing lidaround the full circumference. An electronics space is delimited by the housing lidand the electronics housing. In said electronics space, an electronic system, power busbars and circuit elements such as IGBT are installed (not visible).

On the basis of, general variants and more concrete embodiments of the displacer body arrangement are described according to the first principle of the disclosure. The first principle excels by the fact that at least one rest chamberinto which the fluid penetrates is formed in the at least one interior space of the displacer body arrangement.

Each of theillustrates the housing of the fluid heaterof. The respective coils of two tubular heating elementsextend along a coil axis. Two end sections with electrical connections of the two tubular heating elementsextend in a sealed state through the housing lidinto the electronic space of the electronic housing(shown in), only one end section with the electrical connection being shown in each of the.

illustrates the housing of the fluid heaterofwith a first variant of the displacer body arrangement. The latter consists of a tube;;;;;that is radially spaced apart from the coils of the tubular heating elementsand at the end face is in preferably sealing contact with the two housing end wallsof the preferably trough-like housing part. For this purpose, the tube;;;;;is clamped between the two housing end walls. Initial filling of the rest chambercreated in this way takes placed via radial openingsof the tube;;;;;. During operation of the fluid heater, a transverse flow is largely avoided.

illustrates the housing of the fluid heaterofwith a second variant of the displacer body arrangement. The latter consists of a tube;;;;;that is radially clamped at the coils of the tubular heating elements. The two end faces of the tube;;;;;are spaced apart from the respective housing end wallsof the preferably trough-like housing part. Initial filling of the rest chambercreated in this way takes place via the two annular openingsin the region of the housing end walls. During operation of the fluid heater, low transverse flow is possible, namely along the two housing end wallsand from the one annular openingthrough the rest chamberto the other annular opening.

In a sub-variant of the second variant, an end-face lidis provided on the tube;or an inner partition is provided inside the tube;;;at any position along the coil axis(both are not shown in). An opening is provided in the lidor in the partition.

illustrates the housing of the fluid heaterofwith a third variant of the displacer body arrangement. The latter consists of two cups;;which are clamped radially to the coils of the respective tubular heating element. The bottomsof the two cups;;are adjacent to each other and have a small distance from each other. The end-face edges of the two cups;;are spaced apart from the respective housing end wallof the preferably trough-like housing part. The initial filling of each of the two rest chamberscreated in this way takes place via the annular openingformed between the edge of the cup;;and the adjacent housing end wall. During operation of the fluid heater, a low transverse flow is possible directly along the two housing end wallsand between the bottomsof the cups;;.

In a sub-variant of the third variant (not shown in), the two cups;;abut on each other to minimize the transverse flow. Accordingly, the two bottomsor else, in a deviating manner, the two edges of the cups;can abut on each other.

In the following, more concrete embodiments of the present disclosure shall be described on the basis of the associated figures.

illustrates the electric fluid heateraccording to the disclosure with a first embodiment of a displacer body arrangement formed of two independent displacer bodies each being designed as a cup.

Two tubular heating elementseach having a plurality of coils are provided resulting in a circular-cylindrical inner region which extends along a coil axis. Arrangements of this type are basically known from prior art so that further explanations are not necessary.

The two cupsof the displacer body arrangement are inserted in a respective tubular heating element. Also, two cups of different length can be inserted, the longer cup thereof being inserted in both tubular heating elements.

The fluid heater according toincludes the trough-like housing parton the lower side of which along the coil axisthe two portsfor the fluid, preferably a coolant, are formed to be spaced apart from each other. On an upper side, the trough-like housing partis tightly sealed by a housing lid. Two end sections with electrical connections of each of the two tubular heating elementsextend in a sealed state through the housing lidto the outside, inonly one end section with the electrical connection being shown.

Each cuphas a cover and a bottom, wherein a rounded region is formed on the cover adjacent to the bottom. The two cupsare identical and are inserted mirror-inverted to each other into the inner region of the coils so that the two bottomsface each other and have a small distance from each other. Each of the two edges of the cupsabuts on a housing end wallof the trough-like housing part. In particular due to the distance of the two bottomsfrom each other, the illustrated displacer body arrangement extends over at least 90%, preferably over at least 95% of the distance of the two housing end wallsalong the coil axis.

illustrates the fluid heater ofin a cross-section with the viewing direction A-A (according to) along the coil axis. This results in a view to the bottomof a cupand along the flow region,for the fluid at the outer circumference of the cups. It can be seen that the cuphas four longitudinal ribsdistributed along the circumference of its cover by which the cupis held, such as clamped, in the coils of the tubular heating element, and that four longitudinal channels are maintained between the four longitudinal ribs. Each of the longitudinal channels forms an inner flow regionfor the fluid through which the fluid can flow between the coils and the cover of the cupand can absorb heat. Said inner flow regionsalso help reduce the undesired heat input into the interior space of the respective cup. An outer flow regionis formed at the outer circumference of the coils.

According to the first principle of the disclosure, the cuphas four openings in the form of through-holes, which are arranged in the rounded region of the cover.

illustrates one of the two cupsof the. Only one through-holeout of the four through-holesin the rounded region of the cover can be seen. It is further shown that the cover of the cuphas the four longitudinal ribs, wherein an opening in the form of a slitis provided at one of the longitudinal ribs. The total of five openings allows the fluid to penetrate from the flow region,into the interior space of the cup, resulting in 90%, preferably 95%, of the interior space being separated by fluid-tight walls from the flow region,, thus allowing the fluid to penetrate into the rest chamberformed in this way.

illustrates a deviating embodiment of a displacer body arrangement which is formed by a tubeprovided for insertion into the inner region of the coils of the two tubular heating elementsof. The tubetakes a cylindrical shape having five longitudinal ribsunevenly distributed along the circumference and a corresponding number of inner flow regions.

The upper longitudinal ribinis manufactured to have an overlap so that a slitcan be formed there. Further, the end-face edges of the tubeare not in fluid-tight contact with the two housing end walls(shown in) so that there also openings are formed allowing the interior space to form a rest chamber for the fluid.

The tubeofcan be installed with the slit acting as an opening in the first variant (according to) and with the closed slit of the second variant (according to).

illustrates another embodiment of a one-part displacer body arrangement formed by a tubefor insertion into the inner region of the coils of the tubular heating elementsof the. The tubetakes a cylindrical shape with eight longitudinal ribsdistributed around the circumference and a corresponding number of inner flow regions.

An inner flow region, which is deeper than the other inner flow regions, is provided between two (upper in) longitudinal ribs.