EP2861914B1 - Continuous flow heater - Google Patents

Description

For the heating of liquids in continuous operation many different proposals have been made. After DE 1 335 456 U are a tubular heater with an electric heating element and a metal tube for water each guided in a helical shape with several mutually running at a small distance turns and poured into a metal body. The DE 690 17 041 T2 describes a coffee machine with a heater with electrical resistance and coil in a metal block. The heat losses of the metal body are relatively large and the large mass of the metal body makes the radiator sluggish, so that heating of the water flowing through the metal pipe in a short time is not possible if the metal body is not already at a high temperature.

After DE 198 29 681 C1 are a heating coil and Kapillarrohrwendel arranged radially at the same distance from an axis adjacent to each other by pouring in a tubular brass body. The liquid to be heated flows through a capillary tube which of course does not allow large flow rates. In addition, the heating coil runs directly on the outer surface of the brass body, resulting in a considerable heat loss. The arrangement of the capillary tube and the heating coil in the brass body is associated with a large manufacturing effort.

In case of DE-103 22 034 a surface heater is attached to the outside of a pipe. An inner tube serves as a carrier for helical ribs, but which do not extend to the outer tube, so that the heat transfer from the surface heating element to the guided over the ribs liquid is relatively poor. In addition, a portion of the heat generated is emitted directly to the outside.

EP 1 360 918 A1 describes an espresso machine in which an electric heating coil is arranged in a boiler. To quickly provide hot water, the water in the boiler must be kept at a high temperature even before the need for hot water, which is associated with an undesirable standby operation or with long heat-up times.

From the DE 35 42 507 C2 a continuous flow electric heater for heating liquid media is known, which consists of an extrusion with a passage for the channel to be heated Medium and a tube portion for a compacted tubular heater and is wound into a helix. The heat-conductive connection from the tubular heater to the passage channel is formed only in a small peripheral region of the tubular heater, so that on the one hand the desired heat flow is reduced and on the other hand a larger peripheral area serves as a radiating surface over which a portion of the heat of the tubular heater is lost.

According to DE 29 13 385 For example, a coiled tubing with copper tube and heating resistor is wound around a water chamber, so that the heating resistor can heat the water in the chamber and the water in the copper tube, wherein the heating is used in the copper tube to generate steam. Rapid further heating of water from the chamber is only possible when the water temperature in the chamber is already at a high temperature. In the beginning, this system is very sluggish and if the water in the chamber has to be kept warm for a long time, corresponding heat losses occur.

US 1 595 819 describes a coiled tubing which is arranged around a longitudinal tube. In the interior of the longitudinal tube is a refractory filling block with a spiral groove, in which a heating coil is inserted so that it does not come into contact with the longitudinal tube. This arrangement is complex and does not achieve sufficiently rapid heating of the liquid flowing through the coiled tubing.

The invention has for its object to provide an energy-efficient water heater, which is able to bring the respective liquid, such as water, milk or the like., In the shortest possible time to the desired temperature, and this in a cost effective manner. According to the invention, this is achieved by the combination of the features of claim 1.

The ability to make the outer and inner layers relatively thin, reduces the heat-absorbing and therefore the heating of the liquid retarding mass. But this also means a space-saving and cost-effective design. At the same time, heat storage and losses through the at least one insulation layer are kept low.

The water heater is cylindrical in shape around a central axis. It comprises radially outside the outer layer with a helically arranged channel, radially inside the outer layer then the inner layer with an electric heating coil and radially inside to the inner layer then the insulation layer. These three layers comprise material and shape properties corresponding to the respective function and they can be constructed of different layers. The arrangement of the layers ensures that substantially all the heat generated by the heating coil passes radially outward to the helical channel and that a structure with a small mass of material to be heated in relation to the channel volume is possible.

In order to deliver the generated heat substantially without delay to the medium or the liquid in the channel, the inner layer is formed between the heating coil and the channel with small thickness and / or of material with a high thermal conductivity. The inner layer comprises at least one heating coil. The inner layer comprises a layer extending from the heating coil to the outer layer with heat-conducting and electrically insulating material. If the material of the inner layer between the heating coil and the outer layer with the channel is electrically non-conductive, then as a heating coil, a non-insulated heating wire can be used and the heat of the heating wire passes directly, ie without delay, in the material of the inner layer between the heating coil and the outer layer. The radial thickness of this material need only be so large that an electrical penetration of the heating wire is excluded to a voltage applied to the inner layer metallic sleeve of the outer layer. Preferably, the layer with heat-conducting and electrically insulating material between the heating coil and the outer layer has a radial extent of less than 4 mm, in particular less than 2 mm.

In a preferred embodiment, the inner layer between the heating coil and the outer layer is formed by a compacted powder of magnesium oxide. In this material, a radial distance between the heating wire and the outer layer sleeve of 2 mm, in particular only 1.1 mm, is sufficient to prevent electrical breakdown. According to the small distance and the mass of the inner layer is very small, so that the heat generated by the heating wire passes by the warming up of this small mass only slightly delayed to the outer layer. The innermost layer of the outer layer adjoining the inner layer can be formed by a thin sleeve of metal with high thermal conductivity. As a result, the heat from the heating wire with minimal delay in the medium located in the channel.

The solution according to the invention makes it possible to wind the heating wire onto a bolt-shaped insulating layer, preferably made of ceramic, on which, if necessary, a thin layer of thermally conductive and electrically insulating material has already been applied. Experiments have shown that even a directly wound onto the insulation layer heating wire transfers the heat sufficiently well in the voltage applied to the heating wire thermally conductive material. The arrangement and compression of heat-conducting and electrically insulating material between the heating coil and the outer layer can be carried out in a sleeve with little effort. It is much simpler than the positioning required in the solutions of the prior art a heating wire in a tube, the subsequent filling of the tube with heat-conducting and electrically insulating material, the forming of the tube into a tube coil, the positioning in a mold and the casting of this tube coil with metal. In the inventive solution not only the production cost is smaller, but in operation, the reaction rate is much higher, because it can be dispensed with an embedding of the heating wire in a pipe.

The outer layer comprises at least two layers which each form a wall of this outer layer. The channel is incorporated into one of these walls. The innermost layer of the outer layer closes the channel tight against the inside and lets the heat flow from the inner layer to the channel. A middle layer of the outer layer comprises the helical channel wall and an outer layer of the outer layer closes the channel tightly against the outside. With this structure can be dispensed with the use and costly positioning of a coiled tubing. Solutions in which the channel is formed by helically extending pipelines have the disadvantage that they are essentially restricted to round cable cross sections and that the distance between two adjacent cable cross sections amounts to at least two wall thicknesses of the pipeline. In the solution according to the invention, the channel cross section is freely selectable.

In order to supply the generated heat essentially completely to the medium or the liquid in the channel, the helically extending channel walls are formed as narrow as possible in a further preferred embodiment, so that in a longitudinal section of the cylindrical continuous flow heater, the predominant length fraction is preferably more than 80%, in particular more than 90%, occupied by the adjacent channel sections in the axial direction. When the channel is filled with a medium to be heated, the majority of the heat flowing radially outwardly from the inner layer goes directly into the medium. Even from the narrow channel walls, a large proportion of the incoming heat goes into the medium to be heated, so that only a very small proportion of the heat does not enter the medium.

In order to ensure that substantially all of the heat generated by the heating coil flows radially outwards, an insulating layer with a thermal conductivity which is as small as possible is subsequently arranged on the inside of the inner layer.

According to a preferred embodiment, this insulating layer is also electrically insulating and a heating wire is wound directly onto the insulating layer. At this Embodiment is used as an insulating layer, for example, a cylindrical bolt made of ceramic material. On the bolt of ceramic material, the heating wire is wound helically. Optionally, a thin heat-conducting but electrically insulating inner layer of the inner layer is applied to the bolt before winding, so that the outgoing from the heating wire heat can flow around the heating wire in the heat-conductive material of the inner layer.

In a further preferred embodiment, the insulation layer comprises a layer or a region which is free and through which an electrical and / or a fluid line can be guided. The heating coil can thus have both electrical connections at the same end face of the flow heater, with one connection leading directly to the proximal end of the heating coil and the other through the insulation layer to the remote end of the heating coil. Optionally, a fluid supply line is passed through the insulating layer, so that even the small amount of heat flowing through the insulating layer can be supplied to the fluid.

The dimensioning of the water heater, in particular the radial and axial dimensions of the outer layer and the inner layer, as well as the heating power of the heating coil can be easily adapted to the particular application. The instantaneous water heater according to the invention can be advantageously used wherever predetermined flow rates of a medium at a predetermined temperature have to be provided without heat storage with short reaction times.

For coffee machines, the instantaneous water heater can be designed so that, after a delay of less than 7 seconds, it can continuously supply water at a temperature of 90 ° C, with the inlet temperature of the water at around 20 ° C and the volume of water in the channel at the same time about 8500mm ³ or 8.5ml. If 8.5ml of water is contained in the channel, water must be provided for 1dl of coffee in the amount of 12 times the channel volume. After starting the water heating, the water in the channel is first heated to the desired temperature during a short warm-up time. Then the water with the desired flow rate is conveyed through the water heater and heated to the desired temperature during flow. The inventive water heater can ensure the desired outflow of water with the desired temperature with an electrical power of 1100 watts.

Laboratory equipment may have very different requirements for temperature and flow rate. The respective requirements can be met easily with the appropriate design of the inventive water heater.

Also in applications with high flow rates but lower temperatures, such as in a shower toilet, where per minute about 1 liter of water is required at 37 ° C, inventive water heater can be used with appropriate design.

So that the water heater can adjust its performance or the heating of the fluid to a desired fluid outlet temperature and in particular to a respective fluid flow, it is supplemented with a controller which controls the electrical supply of the heating wire. The controller must receive at least an on-off signal that determines whether the heater wire should be electrically energized or whether no heat should be generated. If the heating wire is electrically powered, it can achieve a heating power according to the flowing current. If the temperature of the heated fluid to be selected and this also for different flow rates, the controller is in addition to the on-off signal at least one more signal from a temperature sensor at the end of the water heater and / or by a flow sensor and / or by a Temperature sensor received at the inlet of the water heater and take into account when adjusting the heating power.

Due to the high efficiency and the rapid provision of hot water, the instantaneous water heater according to the invention is also suitable for heating hot water obtained via faucets or shower heads. Because the powerful water heater can be manufactured inexpensively, it is possible to equip all consumption points with a water heater. The maximum heat output can be designed for the maximum hot water consumption (maximum temperature, maximum flow) of a point of consumption, whereby the different demands on the maximum water temperature and the maximum flow can be taken into account for different consumption points such as the bathroom or kitchen.

The respective heating of the water can be adapted to the consumption temperature selected by the consumer. If the electrical supply of the water heater is connected via a control connection with a setting device of the fitting of the point of consumption, the heating power can be adjusted exactly to the selected position of the adjustment. If necessary, when adjusting the heating power also a temperature measurement during the passage of the water heater and / or a flow measurement used. The inventive instantaneous water heater allows service water to be provided directly at a very precisely predetermined temperature. If the heating of the service water emanates from the cold water, so can be dispensed with a central hot water storage tank and the parallel laying of hot and cold water pipes. It can be assumed that the outlay for the water heaters required at the points of consumption is smaller than the expense for the hot water storage tank and the hot water pipes.

In the conventional solutions hot water is kept in a reservoir in particular in a boiler and promoted as needed over a often very long line to the point of consumption and mixed with cold water so that water can be delivered at the desired temperature. The line from the reservoir to the point of consumption leads to the delayed arrival of the hot water and also the mixing ratio between the water from the reservoir and the cold water supply must be changed in the start-up phase. With the instantaneous water heater according to the invention, water of the desired temperature can be dispensed directly even if the consumption points are opened at different rates. If necessary, also located close to each other points of consumption via a common instantaneous water heater. If a hot water storage tank is already present in a house, for example combined with thermal solar collectors, then the instantaneous water heater according to the invention can be used in a supplementary manner where the immediate receipt of hot water is always to be ensured, ie even if the water between the hot water tank Reservoir and the point of consumption has cooled. The heating power of the water heater is reduced with the arrival of the coming from the hot water storage tank hot water or possibly switched off. In such an application, it is expedient if the instantaneous water heater comprises a temperature sensor both at the inlet and at the outlet.

The use of a continuous flow heater according to the invention for heating over consumption points, such as faucets or shower heads, related hot water, in which use a continuous flow heater according to the invention is located at the point of consumption, is also claimed as the invention.

Rinsing and cleaning cycles can be used to remove dirt and limescale. The channel shape can be chosen so that there are no Ansetzstellen for the attachment of dirt and lime. If the channel is accessible for cleaning must, the layers of the outer layer are formed so that at least the outermost layer of the outer layer in the axial direction can be deducted from the adjoining inner layer. As a result, the entire channel border is accessible, with a partial area at the innermost layer and a partial area at the outermost layer of the outer layer being accessible. This means that the outer layer comprises two sleeves, which can be pulled apart for cleaning.

In a particularly advantageous embodiment, the insulating layer provided with the heating wire is arranged centrally in a first sleeve of good heat-conducting material, in particular in a first sleeve of metal, and in the annular region between the heating wire and the first sleeve powdered material, preferably magnesium oxide, filled. In order to achieve the desired high thermal conductivity, the powdery material is compressed in the annulus. According to a preferred production method, the filled first sleeve is narrowed radially inward by a rolling process, so that with the decreasing outer diameter of the first sleeve, the powdery material is compressed and the voids are displaced. The rolled and preferably closed at least one end face first sleeve is inserted into a second sleeve, wherein in an annular space between the two sleeves of the helically arranged channel is formed. The annular area between the two sleeves is sealed at the two front ends of the sleeves. For this example, two rings with laser seams are tightly connected to the sleeves.

The helical channel may be incorporated in the outside of the first sleeve or in the inside of the second sleeve. Optionally, a channel wall forming coil is used for channel formation between the two sleeves. The channel wall only has to ensure that the large proportion of the medium flowing through the channel flows completely along the spiral shape. Even if the channel wall does not connect completely tightly to both sleeves, a passage of the channel which is essentially following the helical shape is still ensured. The channel wall can be formed with a very small thickness, so that the majority of the annular space between the two sleeves of channel areas is occupied. In this case, the channel in cross-section preferably has a substantially rectangular shape.

An inlet for a liquid to be heated and at the other end an outlet for the latter are then formed at one end of the channel. The inlet and the outlet preferably lead in the radial direction through the second sleeve.

If the channel is incorporated in the outside of the first sleeve, the use of a rolling process for compacting, or narrowing radially inward, through the channel walls is made more difficult. At least for small diameter sleeves, it is advantageous if the channel is incorporated in the inside of the second sleeve and thus the first sleeve can be formed very thin-walled. The incorporation of the channel in the inside or the outside of a sleeve can be carried out with a turning process or a milling process. According to a particularly simple manufacturing method, the second sleeves are separated from a tube in which a continuous channel was produced by means of rotation. The separated second sleeves have no end of the channel at the ends and therefore two rings with laser seams are tightly connected to the two sleeves. If the channel on the individual sleeves is worked out, it can be worked out so that a conclusion remains at both front ends and thus no rings must be used for the conclusion between the two sleeves.

The incorporation of the channel in the inside or in the outside of a sleeve can also be carried out before the formation of the sleeve shape. For this purpose, for example, a blank of a sheet can be pressed with a press into a mold, so that on one side of the sheet projecting segments of the channel wall. This sheet metal with projecting segments of the channel wall can then be formed into a tubular shape and closed at adjoining side lines with a longitudinal seam, in particular a laser seam, to form a tube. The segments of the channel wall then close to each other so that a helical channel wall is provided. The longitudinal seam must also be formed at the channel wall. The channel wall does not necessarily have to be continuous, because it only has to ensure that the water flows essentially along the channel through the instantaneous water heater. Embodiments are also possible in which the channel wall is interrupted in the longitudinal seam, so that the side lines of the sheet metal blank to be joined together run along straight lines. As a result, the formation of the longitudinal seam is simplified.

Fig. 1

eine Draufsicht auf einen Durchlauferhitzer im Sinne des Pfeiles I der Fig. 2, jedoch ohne Ummantelung;

Fig. 2

eine Seitenansicht des Durchlauferhitzers mit angedeuteter Ummantelung;

Fig. 3

einen Längsschnitt durch den Durchlauferhitzer der Fig. 1 und 2;

Fig. 4

einen Schnitt durch eine abgewandelte Ausführungsform;

Fig. 5

einen Längsschnitt durch einen Durchlauferhitzer mit an der Innenschicht einer Hülse ausgebildeter Kanalwand;

Fig. 6

einen Längsschnitt durch eine an einer Stirnseite geschlossenen Hülse mit darin angeordneter Innenschicht und Isolierungsschicht;

Fig. 7

einen Längsschnitt durch eine Hülse mit der an der Innenseite ausgebildeten Kanalwand, zwei Leitungsanschlüssen und zwei Abschlussringen;

Fig. 8

eine perspektivische Darstellung der Hülse nach Fig. 7

Fig. 9

eine Draufsicht auf einen Druchlauferhitzer nach Fig. 5

Fig. 10

einen Längsschnitt durch einen Durchlauferhitzer mit an der Aussenschicht einer Hülse ausgebildeter Kanalwand;

Fig. 11

einen Längsschnitt durch eine Hülse mit der an der Aussenseite ausgebildeten Kanalwand;

Fig. 12

eine perspektivische Darstellung eines Durchlauferhitzers mit zwei elektrischen Anschlüssen und zwei Leitungsanschlüssen; und

Fig. 13

eine perspektivische Darstellung eines Durchlauferhitzers mit einer axial durchgeführten Leitung und zwei elektrischen Anschlüssen.

Further details of the invention will become apparent with reference to the following description of exemplary embodiments schematically illustrated in the drawings. Show it:

Fig. 1

a plan view of a water heater in the direction of arrow I the Fig. 2 but without sheathing;

Fig. 2

a side view of the water heater with indicated casing;

Fig. 3

a longitudinal section through the instantaneous water heater Fig. 1 and 2 ;

Fig. 4

a section through a modified embodiment;

Fig. 5

a longitudinal section through a flow heater with trained on the inner layer of a sleeve duct wall;

Fig. 6

a longitudinal section through a closed at one end sleeve with inner layer and insulating layer disposed therein;

Fig. 7

a longitudinal section through a sleeve with the formed on the inside channel wall, two line connections and two end rings;

Fig. 8

a perspective view of the sleeve after Fig. 7

Fig. 9

a top view of a Druchlauferhitzer after Fig. 5

Fig. 10

a longitudinal section through a flow heater with formed on the outer layer of a sleeve duct wall;

Fig. 11

a longitudinal section through a sleeve with the formed on the outside channel wall;

Fig. 12

a perspective view of a water heater with two electrical connections and two line connections; and

Fig. 13

a perspective view of a water heater with an axial line and two electrical connections.

Fig. 1 shows a flow heater 1 with at least one (preferably at least two) Efensicherung (s) and ground 2 in the circuit of a heating coil 3 and a sensor unit 4, which will generally comprise at least one temperature sensor. To the heating line 3, a control stage 5 is connected to the output to the heating coils 3 from a power supply 6 energy. Conveniently, this control level 5 is provided with a program memory 7 to run one of several programs that can be accessed via an input unit 8, such as a keypad, a touch screen or a mere selector switch, via this input unit 8 expediently the desired heating temperature can be entered. This temperature is measured by the sensor unit 4 and fed to the control stage 5 as an input signal. The type of possible programs will be discussed later.

Further, the control stage 5 is connected to a pump control device 9, with which the flow rate of each liquid pumped through the water heater 1 - and thus the supply of cold liquid - regulated (eg via a in the sensor unit 4 or separately existing pressure sensor) or by controlling the Pump speed can be controlled.

Based on FIGS. 2 and 3 Now, the structure of the water heater 1 will be explained. This is made up of several layers, of which Fig. 3 an outer layer 10 with approximately helically wound around a longitudinal axis A, in a wall 11 of the layer 10 incorporated, preferably milled channels 12 has. The channels 12 preferably have a different shape from a round or circular cross-section, and are thus - as shown - preferably rectangular or trapezoidal, so as to increase the surface area compared to the volume (compared to a circular cross-section). Typically, the ratio of the channel wall 14 facing a second inner layer 13 to the helical lateral boundary wall 15 is in the range of 1: 0.2 to 1: 0.25, but pitch of the helical shape and dimension can be varied. The wall of the wall 14 opposite, radially outer wall may optionally be shorter, in which case then by appropriate dimensioning of the side walls 15, a trapezoidal cross-section is formed.

This outer layer has as a cover to a jacket tube 16, the shrunk best or warm, but then also - at least at the ends -, conveniently by means of laser welded. Advantageously, the continuation of the channel wall 14 corresponding extension 14a extends to at least one attached to an end face of the water heater 1 (unheated and heat resistant) cover 17, the function will be explained below and through which advantageously at least one end of the heating 3 runs (see. Fig. 1 and 2 ).

For supplying the liquid to be heated, such as water (eg in the case of a shower water heater) or milk (in the case of a beverage manufacturing apparatus), a respective inlet pipe 18 and a drain pipe 19 is provided, which theoretically although parallel to the axis A in the channels 12 could, but preferably transverse to the axis A of the layers having body of the water heater 1 are mounted, as shown in FIGS FIGS. 2 and 3 is apparent.

The inner layer 13 consists of a heat-resistant, heat-conducting, eg ceramic, Heizleiterträger, in which the coils 3a of the heating element 3 are embedded. These coils 3a are coiled in the same direction as the channels 12, ie they run parallel to them, so that an optimum heat transfer from the heating coils 3a to the channels 12 takes place. For this purpose, the heating coils 3a are arranged closer to the channels 12 than to the axis A. Preferably, the distance a between the (circular) line of the channels 12 and the (circular) line of the heating coils is one quarter to one Fifth of the distance a 'of the line of heating coils 3a to the axis A, so that the heat transfer from the heating coils 3a to the channels 12 can be done very quickly.

The fact that the distance a 'is much larger than the distance a results in a relatively large space in between, which would also absorb a large amount of heat. To avoid this and to allow the performance of the heating coils 3a possible only the channels 12, at least one insulating layer in the form of a hollow tube 20 made of temperature-resistant material is provided against the axis A. The hollow interior of this tube can be filled with heat-resistant insulating material 21, in particular ceramic, so as to reduce the energy-absorbing volume and thus to save energy when heating the liquid in the channels 12. But it is also possible to use the air inside the hollow tube 20 for the insulation.

While thus preventing the passage of greater amounts of heat into the interior of the flow heater 1, which accelerates the heating of the liquid in the channels 12 (actually, it is only a single helical channel 12, although a multi-speed screw would also be possible), it is alternative or additional also still possible in Fig. 2 indicated insulating layer 22 on the outside of the water heater 1 to install. Moreover, it may be advantageous to provide on the outside, in particular over the axial extent of the heating coils 3a, a good heat-conducting or heat-storing layer 23, for example of aluminum or copper, which expediently in the axial direction only over the length of the of the layers 10th , 13 formed body of the water heater 1 extends.

It has been found that for various applications, the attachment of a connected to the control stage 5 and controlled by her vibrator 24 on the outside of the water heater 1 is advantageous. On the one hand, its operation favors the heating, on the other hand it can be used after switching off the heater and / or shortly before commissioning for cleaning or decalcifying the channels 12. Optionally, the respective operating mode and / or the vibration frequency or intensity can be set by the input unit 8. Especially if the layers 22 and 23 are missing, it may be advantageous for some purposes if the axial position of the vibrator 24 is adjustable. Alternatively, the axial position of the vibrator 24 may be adjusted prior to attaching at least one of the layers 22, 23 externally. The displacement takes place via a fixable with a clamping screw 26 support ring 25. It can but a improved heat transfer can be achieved in that at least one of the layers 22, 23 and / or (in particular) of the support ring 25 is poured.

Since thus the conditions for rapid - and thus energy-saving - heating by the radial direction with respect to the axis A successive layers, but also by the subsequent in the axial direction and there the departure of heat preventing covers 17 are optimized and thus a rapid temperature change can be brought about can, via the input unit 8 different programs, such as a therapy program with a change of water temperature in the manner of a Kneipp cure, a rinse (after completion of heating) or programming for the pump control 9 in such a way that the fluid pressure at the beginning of heating is lowered (facilitates rapid heating). For all these programs, the program memory 7 is provided.

According to Fig. 4 a radiator 13a is provided, which is basically constructed in a similar manner as previously described with reference to the layers 13, 20 and 21. On a wall 10a of the outer layer 10, however, the channels are not milled on the outside, but from the inside (in principle, the production of the channels would also be conceivable by turning). The thus prepared wall 10a of the outer layer 10 is then warmly applied to the body 13a and adheres to it after cooling. Again, it is expedient if the outer layer 10a is subsequently welded firmly to the (axial) ends, in particular by laser welding.

Fig. 5 to 9 show the structure and elements of a simple to produce water heater 1. In this embodiment, as the insulating layer 21, a cylindrical bolt made of ceramic material is used. Because the insulation material is sufficiently stable, it is possible to dispense with a tube 20 surrounding this material. On the bolt of ceramic material of the heating element 3 or resistance heating wire is wound as a heating coil 3a. The insulation layer 21 provided with the heating coil 3a is arranged centrally in a first sleeve 10b made of metal and in the annular region between the heating coil 3a and the first sleeve 10b is powdered material, preferably magnesium oxide, filled for further construction of the inner layer 13. In order to achieve the desired high thermal conductivity, the powdery material is compressed in the annulus. According to a preferred production method, the filled first sleeve 10b is narrowed radially inward by a rolling process, so that with the decreasing outer diameter of the first sleeve, the pulverulent material is compressed and the voids are displaced. The first sleeve 10b is preferably at an end face with closed a bottom 27 and is optionally made by deep drawing from a sheet.

The first sleeve 10b with insulating layer 21 and the inner layer 13 is inserted into a second sleeve 10a or into a wall 10a of the outer layer 10, wherein the wall 10a of the outer layer 10 with a radially inwardly extending coiled channel side wall 15 a channel 12th forms. The channel 12 is thus worked on the inside of a wall 10 a of the outer layer 10. In the assembled state according to Fig. 5 The first sleeve 10b together with the second sleeve 10a forms the outer layer 10 with two walls and an intermediate channel 12.

The channel side wall 15 only has to ensure that the large proportion of the medium flowing through the channel flows completely along the helical shape. Even if the channel side wall 15 does not completely close to the first sleeves 10b, a passage of the channel 12 substantially following the helical shape is still ensured. The channel side wall 15 is formed with a small thickness, so that the predominant portion, preferably more than 80%, in particularly advantageous embodiments even more than 90%, of the annular space between the two continuous cylinder walls of the outer layer is occupied by channel regions. In this case, the channel 12 has a substantially rectangular shape in cross section.

The annular region between the two sleeves 10b and 10a is sealed at the two front ends of the sleeves 10b and 10a. For this example, two rings 28 are connected with laser seams tightly with the sleeves 10b and 10a. Then, at one end of the channel 12, an inlet pipe 18 for a liquid to be heated and at the other end a drain pipe 19 for the heated liquid are formed on the channel 12. The inlet pipe 18 and the outlet pipe 19 preferably connect in the radial direction to openings 18a and 19a of the second sleeve 10a.

The heating coil 3a can have both electrical connections 3 at the same end face of the flow heater 1, one connection 3 leading directly to the proximal end of the heating coil 3a and the other through the insulation layer 21 to the remote end of the heating coil 3a. For this purpose, an axial bore and a radial bore or a groove is arranged in the insulating layer 21 for the guidance of the heating conductor 3 that the heating conductor 3 does not come into contact with the bottom 27th

10 to 12 show the structure and elements of another easily manufactured flow heater 1. Also in this embodiment is used as the insulating layer 21, a cylindrical bolt made of ceramic material. On the bolt of ceramic material of the heating element 3 or resistance heating wire is wound as a heating coil 3a. The insulation layer 21 provided with the heating coil 3a is arranged centrally in a first sleeve 10b made of metal or in a wall 11 of the outer layer 10 and in the annular area between the heating coil 3a and the first sleeve 10b is pulverulent material, preferably magnesium oxide, for further construction the inner layer 13 filled. In order to achieve the desired high thermal conductivity, the powdery material is compressed in the annulus.

A second sleeve or a jacket tube 16 of the outer layer 10 is pulled over the first sleeve 10b or over the wall 11 of the outer layer 10, wherein the outer layer 10 forms a channel 12 with a channel side wall 15. The channel 12 is worked out on the outside of the wall 11. In the illustrated embodiment, the channel 12 is formed by milling so that at the two end faces of the wall 11, a conclusion is formed, which is tightly connected to the casing tube 16. Then, at one end of the channel 12, an inlet pipe 18 for a liquid to be heated and at the other end a drain pipe 19 for the heated liquid are formed on the channel 12. The inlet pipe 18 and the outlet pipe 19 preferably connect in the radial direction to openings of the jacket pipe 16. On the two end faces of the flow heater 1, electrically insulating covers 17a are arranged, one of which comprises a protruding separating layer 17b in the electrical connections 3.

Fig. 13 shows an embodiment in which the insulating layer 21 has a central bore through which a fluid line 29 is guided. After the passage of the fluid line 29 through the insulating layer 21, the fluid line 29 is connected to the inlet pipe 18. The heating coil has the two electrical connections 3 on each side of the flow heater 1.

Claims (15)

1. Continuous flow heater (1) comprising a body, which is formed from at least two layers (10, 13, 20, 21) extending around an axis (A), wherein

   a) an outer layer (10) comprises a channel (12), which is coiled around the axis (A) and the outer layer (10) has an inlet (18) to the channel (12) on one end for a liquid, which is to be heated, and has an outlet (19) on the other end for said liquid,

   b) an inner layer (13), which comprises an electrical heating coil (3a), connects to the outer layer (10) on the inside, and

   c) at least one insulating layer (20, 21) connects to the inner layer (13) on the inside,

   characterised in that
   the channel (12) is incorporated into a wall of the outer layer (10), the heating coil (3a) is arranged in direct contact with a heat conducting and electrically insulating material of the inner layer (13), said material extending to the outer layer (10), and the insulating layer (20, 21) ensures that substantially all of the heat produced by the heating coil (3a) flows radially outwards by means of a heat conductivity of the insulating layer (20, 21), which is as small as possible.
2. Continuous flow heater (1) according to claim 1,
   characterised in that
   the heating coil (3a) is arranged closer to the channel (12) than to the axis (A), preferably in a fourth to a fifth of the distance to the axis (A).
3. Continuous flow heater (1) according to any one of the preceding claims,
   characterised in that
   the heat conducting and electrically insulating material of the inner layer (13) has a radial expansion of less than 4 mm, in particular of less than 2 mm, between the heating coil (3a) and the outer layer (10).
4. Continuous flow heater (1) according to any one of the preceding claims,
   characterised in that
   the channel (12) of the outer layer (10) is embodied between two walls (11), wherein ome wall is mounted on the other wall and the walls are connected tightly on the end faces.
5. Continuous flow heater (1) according to any one of the preceding claims,
   characterised in that
   the electrical heating coil (3a) is formed by a heating wire (3), which is coiled onto the insulating layer (21), the insulating layer (21) comprising the heating coil (3a) is arranged centrally in a first sleeve (10b) of material, which conducts heat well, the area between the insulating layer (21) and the first sleeve (10b), which has a ring-shaped cross section, comprises the heating coil (3a) and compacted, powdery material, preferably magnesium oxide, as inner layer (13), the first sleeve (10b) is inserted into a second sleeve (10a), and the channel (12), which is arranged in a helical manner, is embodied between the two sleeves (10a, 10b), wherein the outer layer (10) is formed by the two sleeves (10a, 10b) and by the channel (12).
6. Continuous flow heater (1) according to claim 5,
   characterised in that,
   on the inner side, the second sleeve (10a) comprises a coiled channel side wall (15), which extends radially inwards and which is preferably embodied by means of turning or milling, if applicable, of the channel region.
7. Continuous flow heater (1) according to any one of the preceding claims,
   characterised in that
   the insulating layer (21) is formed from a cylindrical bolt of ceramic material.
8. Continuous flow heater (1) according to any one of the preceding claims,
   characterised in that
   the insulating layer (21) comprises a feedthrough for an electrical and/or a fluid line in the direction of the axis (A), and the heating coil (3a) preferably has both electrical connections (3) on the same front face of the continuous flow heater (1), wherein one connection leads directly to the close end of the heating coil (3a) and the other end leads through the insulating layer (21) to the remote end of the heating coil (3a).
9. Continuous flow heater (1) according to any one of the preceding claims,
   characterised in that
   the inlet (18) and/or the outlet (19) are attached at right angles to the axis (A) of the body.
10. Continuous flow heater (1) according to any one of the preceding claims,
    characterised in that
    the body has a cover (17, 17a) on at least one of its front faces.
11. Continuous flow heater (1) according to any one of the preceding claims,
    characterised in that
    provision is made for at least one temperature sensor (4), the output signal of which can be supplied to a control stage (5) for the energy emitted to the heating coil (3a).
12. Continuous flow heater (1) according to any one of the preceding claims,
    characterised in that
    the cross section of the channel (12) has a shape, which differs from a round or circular cross section, respectively, and that this shape is preferably rectangular or trapezoidal.
13. Continuous flow heater (1) according to any one of the preceding claims,
    characterised in that
    the major share in the length, namely more than 80%, preferably more than 90%, in a longitudinal section of the cylindrical continuous flow heater (1) of the channel (12) is covered by the channel sections located next to one another in axial direction.
14. Use of a continuous flow heater according to any one of the preceding claims for heating warm water obtained via points of consumption,
    characterised in that
    the continuous flow heater is arranged at the point of consumption and that it is supplemented with a control, which controls the electrical supply of the heating wire and can accommodate at least one on-off signal, which determines, whether the heating wire is to be supplied electrically or whether no heat is to be produced.
15. Use according to claim 14,
    characterised in that
    the continuous flow heater makes it possible to adapt the respective heating of the water to a usage temperature, which can be chosen by the user, preferably comprising a control connection between the electrical supply of the continuous flow heater and a setting device of the armature of the point of consumption, wherein in particular a temperature measurement at the outlet of the continuous flow heater and/or a flow measurement and/or a temperature measurement at the inlet of the continuous flow heater is also considered for adapting the heat output.

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