Patent Description:
It is known that the heating of the air intended for heating the passenger compartment of a motor vehicle, or for demisting or defrosting, is provided by the passage of a flow of air through a heat exchanger, more precisely by a heat exchange between this flow of air and a fluid circulating inside the exchanger. This may in particular be the cooling fluid in the case of a heat engine.

In the case of an electric vehicle, it is also known to use an air-conditioning loop operating in heat pump mode for air heating. However, this mode of air heating can also be unsuitable or insufficient.

This is because the performance of the air-conditioning circuit in heat pump mode depends on the outdoor climatic conditions. For example, when the outside air is too cold, the air cannot be heated to a temperature sufficient to warm the passenger compartment. In this context, it is known to add to the fluid circulation loops an additional electric device for thermal conditioning of the fluid such as an additional electric heating device. Such an additional electric heating device can be adapted to heat a suitable fluid upstream of the heat exchanger. In a known way, such an electric additional heating device comprises one or more thermal modules in contact with the fluid to be heated. More precisely, and as may be disclosed in particular in document <CIT>, a thermal module may comprise a core and a heating element surrounding the core, both being spaced apart in order to define a fluid circulation space between the core and the inner surface of the heating element. The heating element is a source of thermal energy. The heating element has electric heating means, e.g. one or more heating resistors serigraphically formed as serigraphic resistive tracks on the outer surface of the heating element. A fluid circulation in the circulation space between the core and the heating element ensures a heat transfer between the heating element and the fluid. In order to obtain sufficient heating power for the desired operation, it may be necessary to multiply the thermal modules in the same additional electric heating device.

Fluid circulation is facilitated by a pump, which is arranged upstream or downstream of the heat exchanger on a fluid circulation pipe.

The present invention relates to an electric heating block, such as a heating block for a motor vehicle. Electric heating block comprising tubes for receiving heating elements are known as electric heating blocks. Such heating elements include, for example, PTC (positive temperature coefficient) resistors. Such heating blocks also include heat sinks, e.g. fins, in thermal contact with the heating elements. The tubes serve to electrically insulate the heating elements from the outside while allowing thermal conduction between the heating elements and the heat sinks.

<CIT> discloses a headerless heat exchanger having a core comprised of a stack of flat tubes of rectangular cross section through which a first heat exchange fluid passes. The tubes are expanded in height at their end portions to provide spaces between adjacent plate pairs for passage of a second heat exchange fluid between the tubes. The sides of the tubes are coplanar, at least in the end portions of the tubes, to provide flat surfaces along which the core is sealed to side plates of the heat exchanger, for example by brazing or welding. The side plates may be separately formed or may comprise part of a continuous housing. The tubes can be formed from plate pairs having nesting side walls.

<CIT> discloses a heat exchanger comprising exchanging elements and a housing for receiving said exchanging elements. The housing consists of a plurality of interconnected walls. The housing comprises two L-shaped walls.

It would be desirable to provide an electric heater design which would be cost efficient and/or simple to manufacture.

The object of the invention is an electric fluid heater for a vehicle, comprising a heating block comprising an inlet and an outlet for the fluid, a first channel for the fluid intended to flow between the inlet and the outlet, a first tube and a second tube
characterized in that opposing ends of the first tube and second tube are mounted in headers, wherein the tubes comprise heating elements, and wherein the first channel is delimited by a top plate and a bottom plate sealingly connected to the first tube, the second tube and the headers.

Preferably, the first tube and the second tube comprise two side walls connecting the large walls, wherein the top plate and the bottom plate are connected to side walls of the first tube and the second tube.

Preferably, the large walls of the first tube and the second tube are arranged perpendicularly with respect to the top plate and the bottom plate.

Preferably, a side plate is connected parallel to the first tube and/or the second tube on the exterior of the heating block.

Preferably, the side plate is distanced from the headers and the top plate and the bottom plate.

Preferably, the top plate comprises at at least one of the end portions a raised section.

Preferably, the bottom plate comprises at at least one of the end portions a raised section.

Preferably, the inlet and the outlet are each connected to one of the raised portions.

In one option, both the inlet and the outlet are connected to the top plate.

In another option, wherein the inlet is connected to the top plate, while the outlet is connected to the bottom plate.

Preferably, the headers comprise a pair of protrusions extending perpendicularly to the axis of the first tube and/or the second tube.

Preferably, between the first tube and the second tube there is one or more further tubes.

Examples of the invention will be apparent from and described in detail with reference to the accompanying drawings, in which:.

As illustrated in <FIG>, the invention relates to an electric heating block <NUM>. The said heating block <NUM> is intended to be supplied with electric current to heat a fluid passing through the said block <NUM>.

The electric heating block <NUM> advantageously presents a substantially parallelepipedal configuration. It is intended to exchange heat with a fluid passing between an inlet <NUM>, between and/or around tubes <NUM>, and outlet <NUM>. The tubes <NUM> comprise at least a first tube 20a and a second tube 20b.

Electric fluid heater comprises a heating block <NUM> comprising an inlet <NUM> and an outlet <NUM> for the fluid. Therein, a first channel <NUM> for the fluid intended to flow between the inlet <NUM> and the outlet <NUM> is formed. The heater further comprises a first tube 20a and a second tube 20b with opposing ends mounted in headers <NUM>, <NUM>, wherein the tubes 20a, 20b comprise heating elements <NUM>. The first channel <NUM> is delimited by a top plate <NUM> and a bottom plate <NUM> sealingly connected to the first tube 20a, the second tube 20b and the headers <NUM>, <NUM>. The tubes <NUM> are mounted in headers <NUM> and <NUM>, which in turn are connected by top plate <NUM>. To the top plate <NUM> there may be connected also the inlet <NUM> and the outlet <NUM> for the fluid. In particular, the top plate <NUM> may comprise raised portions 4a and 4b, which are connected to each other by a connecting portion 4c. Since the raised portions 4a and 4b are located at a different distance from the tubes <NUM> than the connecting portion 4c, i.e. at the greater distance from the tubes <NUM>, the fluid is enabled to flow more freely in the vicinity of the inlet <NUM> and the outlet <NUM>, thereby facilitating its distribution between and/or around the tubes <NUM>. The channel for the fluid is closed from the bottom by the bottom plate <NUM>, so that the fluid path is limited and an efficient heat exchange with the tubes <NUM> can take place. The headers <NUM>, <NUM> may comprise protrusions <NUM> serving as positioning aid during assembly. This may be useful if slots for the tubes <NUM> are of different character between two sides of the headers <NUM>, <NUM>, e.g. slots on one side may have widening for facilitated insertion of tubes during assembly. Optionally, a side plate <NUM> is connected parallel to the first tube 20a and/or the second tube 20b on the exterior of the heating block <NUM>, for thermal insulation and/or for improving the rigidity of the assembly. In one option, the side plate <NUM> may be distanced from the headers <NUM>, <NUM> and the top plate <NUM> and the bottom plate <NUM>.

<FIG> shows an example of heater tube <NUM>. The heating block <NUM> here comprises several tubes <NUM> and, preferably, several fins <NUM>, or turbulators, alternately stacked in a vertical stacking direction as shown in the figure. The tubes <NUM> are positioned parallel to each other. These tubes <NUM> are used to electrically insulate and protect the heating element(s) <NUM> from the outside. The fins form heat sinks, which increase the heat exchange surface with the fluid.

Heating elements <NUM> are, for example, PTC resistors (for positive temperature coefficient). Each tube <NUM> may have several heating elements, which may be arranged one after the other in a direction of the tube <NUM>. The heating elements <NUM> are preferably distributed evenly along the tubes <NUM>.

The tubes <NUM> together with the heating elements <NUM> form heating units. The heating units are preferably supplied with power selectively. This means that the heating elements <NUM> of each heating unit are supplied with current independently of the heating elements <NUM> of the other heating units and can therefore be supplied with a different current, in particular in terms of its intensity, from the current flowing through the other heating units.

The heating units also have electrodes <NUM> on both sides of the heating elements <NUM> for their power supply. The said heating units further comprise electrically insulating and thermally conductive material layers, the said layers being located between one of the electrodes <NUM> and a large wall <NUM> of the tube <NUM>. In this way, the tube <NUM> is electrically insulated from the electrodes <NUM> and the heating elements <NUM> but thermally in contact with them.

Preferably, in each of the heating units, said heating elements <NUM> are electrically connected in parallel, in particular by means of the electrodes <NUM>.

The fins <NUM> are in thermal contact with the tubes <NUM>. The said fins <NUM> are positioned between the said tubes <NUM>, in particular between the large walls <NUM> of the said tubes <NUM>.

The tubes <NUM> have two side walls <NUM> connecting the large walls <NUM>. The large walls <NUM> each have an external face <NUM> to which the fin <NUM> is fixed and an internal face intended to come into thermal contact with the heating elements <NUM>. Thermal contact involves heat exchange between the elements, even if the elements are not in direct physical contact with each other. The function of the large walls <NUM> is to transmit the heat generated by the electric heating elements <NUM> to the fins. The tube <NUM> can be made of any material suitable for use in an electric heating block <NUM>. In particular, tube <NUM> is made of aluminium and/or aluminium alloy.

The top plate <NUM> and the bottom plate <NUM> are sealingly connected to side walls <NUM> of the first tube 20a and the second tube 20b.

Advantageously, the inner faces of the side walls <NUM> of the tube <NUM> have a substantially vertical profile, if necessary slightly rounded.

Both the large walls <NUM> and the side walls <NUM> are made from the material of the tube <NUM>. Even if several parts are defined, the tube is a single piece.

Fin <NUM> is advantageously attached to one or both of the large walls <NUM> of tube <NUM> by brazing. This fin fixing technique has several advantages. First of all, brazing the fins to tube <NUM> improves the heat exchange between the heating elements <NUM> and the fins. In addition, once tube <NUM> has been brazed, the material of tube <NUM>, for example aluminium, will be more malleable and more easily deformable than before the brazing step, even after it has cooled to room temperature. This reduces the elastic relaxation that the material may have after deformation. In addition, this state of material guarantees a tight contact between the tube <NUM> and the heating elements <NUM> and therefore a better heat exchange. Brazing also ensures a longer life for tube <NUM> as it will be less sensitive to temperature changes and relaxation during the life of heating block <NUM>.

<FIG> shows a partial cross-section of the heater of <FIG>. As can be seen, the large walls <NUM> of the first tube 20a and the second tube 20b are arranged perpendicularly with respect to the top plate <NUM> and the bottom plate <NUM>. Between the first tube 20a and the second tube 20b there may be one or more further tubes 20c.

<FIG> presents another configuration of the heater. The bottom plate <NUM> comprises at least one of the end portions a raised section 8a, 8b. In this case, the raised portions 8a, 8b is located at both ends. This may promote fluid distribution.

<FIG> shows yet another configuration of the heater. In this example, the inlet <NUM> is connected to the top plate <NUM>, while the outlet <NUM> is connected to the bottom plate <NUM>.

Claim 1:
Electric fluid heater for a vehicle, comprising a heating block <NUM> comprising an inlet (<NUM>) and an outlet (<NUM>) for the fluid, a first channel (<NUM>) for the fluid intended to flow between the inlet (<NUM>) and the outlet (<NUM>), a first tube (20a) and a second tube (20b)
characterized in that opposing ends of the first tube (20a) and the second tube (20b) are mounted in headers (<NUM>, <NUM>), wherein the tubes (20a, 20b) comprise heating elements (<NUM>) and wherein the first channel (<NUM>) is delimited by a top plate (<NUM>) and a bottom plate (<NUM>) sealingly connected to the first tube (20a), the second tube (20b) and the headers (<NUM>, <NUM>).