EP2226584A2 - Flow heater and method for producing same - Google Patents

Abstract

The heater (111) has a flow channel (117) for a heated medium around heating elements (120a-120f), which comprises a large boundary surface with the flow channel. The flow channel is opened at the origin and at an end and is closed between the origin and the end. The flow channel comprises a cross-section surface with reduced length, and a constant circumference. Height of the flow channel along the length of the channel is reduced from a maximum channel height to a minimum channel height. The heating element is provided only in sections with constant cross-sectional surface and/or height. An independent claim is also included for a method for manufacturing a flow heater.

Description

The invention relates to a flow-through heating device and to a method for producing such a flow-through heating device.

Flow heaters are known in many forms. Usually, a flow channel, usually a tube, provided on its outer side with a heating element, either wound or firmly applied, for example, printed as a thick-film heating element. Through running water or other liquid media are heated.

A corresponding flow heater is for example from the EP 485 211 A1 known, which has a substantially box-like shape and by projections in the interior has a meandering flow channel. At least at the top of thick-film heating elements are applied, whose course follows or corresponds to the flow channel.

Task and solution

The invention has for its object to provide an aforementioned flow heater and a method for their preparation, which can be eliminated with the problems of the prior art and in particular a low-calcification, low-noise, energy-efficient, pressure-resistant and space-saving flow heater for the heating of liquids, especially water, can be provided close to a cooking point.

This object is achieved by a flow heating device with the features of claim 1 and a method for their preparation with the features of claim 13. Advantageous and preferred embodiments of the invention are the subject of further claims and are explained in more detail below. Some of the features listed below are explained only for the flow heater or only for the manufacturing process. However, they should be able to apply independently to both the heater and the process. The wording of the claims is incorporated herein by express reference.

It is provided that the heating device has a flow channel for the medium to be heated, ie in particular the water, and at least one heating element. The heating element has a large interface with the flow channel and is preferably applied to the outer wall. The flow channel is open at the beginning and at the end and closed in between, in particular tubular. According to the invention, the flow channel has a cross-sectional area which becomes smaller over its length, that is to say from the beginning to the end, wherein the flow channel has a substantially constant circumference.

Thus, it can be achieved with the invention that the flow cross-section in the flow direction, ie along the longitudinal extension of the flow channel decreases continuously, while maintaining its outer circumference. Thus, on the one hand, the flow velocity of the medium or of the water increases and heat transfer between the wall of the flow channel and the medium flowing therein becomes better through the decrease in the flow cross section. It will also the radial temperature gradient within the flowing medium reduces for a better heating of the medium. Further advantageous possibilities emerge from the subclaims and the features explained below.

It is advantageously provided that the flow channel or its cross section in longitudinal extension, ie from the beginning to the end of the flow channel, always or steadily flatter. This may advantageously be such that the cross-sectional area along the flow channel decreases from a maximum cross-sectional area to a minimum cross-sectional area. In this case, the minimum cross-sectional area may be about 20% of the maximum cross-sectional area, in particular at least 40%. Although this is not a change in the cross-sectional area in orders of magnitude, but clearly. Finally, should still be able to pass through the flow channel a sufficient amount of medium without too much flow resistance. At the same time, such a reduction in the cross-sectional area is considered sufficient to achieve a significant increase in the flow rate. In the context of this application, the term "flat" does not necessarily have to be synonymous with "even", but it can be.

A height of the flow channel may, in particular according to the width, change to a similar extent. Thus, a minimum channel height can amount to at least 20% of the maximum channel height, advantageously at least 40%. Of course, a channel width changes considerably less, but also significantly.

According to a first basic embodiment of the invention, it is possible that a change in the cross-sectional area or the height of the flow channel, which, so to speak, takes place hand in hand, takes place approximately uniformly. This can advantageously be a strictly monotonous change that can be achieved, for example, by a continuous printing or rolling process. So, for example a tube, from which the flow channel is substantially formed, is progressively flattened by flattening the gap between the lobes.

In another basic embodiment of the invention, it is possible that the cross-sectional area or the height of the flow channel changes in steps or in jumps. Either these may be jumps directly adjacent to one another, which may be the case, for example, if the flow channel consists of a plurality of interconnected, previously separately produced sections. It is also possible to manufacture the flow channel from two half-shells, which are then connected to each other, for example by laser welding. As a result, it is above all very easy to subsequently produce meandering shapes which are mentioned below.

In a further embodiment, individual sections, each having the same cross-sectional area, can be connected by transition sections which convert the cross-sectional areas into one another. In the above-described flat rolling of a tube for the flow channel, a gap between the rollers can be made narrower in Schrtten. The tube section running through the rollers during this adjustment then forms such a transition section. In such a case, it is advantageously provided that heating elements are provided only in sections with a constant cross-sectional area or constant height. In particular, they are not provided for in the abovementioned transitional periods. Here, because of the uneven surface, the application of heating elements would be very difficult.

In a further embodiment of the invention can be provided that heating elements do not run continuously over the entire length of the flow cross-section, but are provided only in certain longitudinal areas of the flow channel, which are offset from each other or have a distance from each other. In this case, such Heating elements may well be connected in series. Due to the distance from each other, however, it is easily possible to form each with different width and thus performance. By a respective constant width of a heating element, the power generation is based on its area or on its length constant.

It is advantageously provided that a channel wall is at least partially flattened on its outer side or flat, even if the flow channel has been made of a round tube. This is particularly advantageous for opposite sides. In the flattened areas, the heating elements are then applied, possibly even on opposite sides.

Heating elements can basically be applied in many ways. Advantageously, they are applied in thick film technology, which is a proven and reliable method.

A thickness of a heating element can remain unchanged per section. Advantageously, all heating elements have the same thickness, so that they vary only in terms of width and / or length in order to adjust their area performance or heating power. However, it is also possible to vary the thickness of a heating element or its conductor track and thus adjust the area performance or heating power, in particular to vary in the longitudinal course.

For producing a flow-through heating device according to the invention, therefore, a tube, in particular a round tube, can be flattened on two opposite sides and thereby become ever flatter. This can be done for example by an initially described and per se known rollers, alternatively by pressing.

Subsequently, a tube can be bent deviating from a straight extension, for example in loops or in so-called meandering form. Such a curved heater may extend in a plane, advantageously with an inlet and outlet at spaced ends.

In a further embodiment, a flow-through heating device may be designed so that it is bent in the room, so to speak. Here it is possible that it forms a kind of cylindrical shape by hren course, the course also has loops or meander shape and at the same time this meandering forms a cylinder, in particular a round cylinder. It can be advantageously provided that the aforementioned flattened sides of the flow channel at least on one of the sides, ie inside or outside, are provided, in particular approximately following the lateral surface. It is possible, for example, first to deform a tube by flattening in its longitudinal course and bending in meandering and then bending into a cylindrical shape. Then, for example, on the outside, so the lateral surface, the heating elements applied, in particular by printing described above as a thick-film heating element. Such flow heaters have a very small size with high heating power.

Another advantage of the invention is that by forming the flow channel in a curved shape, so for example, loop shape or meander, but especially in spiral or helical shape, with temperature changes, especially when switching on the heating elements, a certain length expansion and thus deformation takes place. This can serve to detach or break off accumulated lime or other contaminants in the interior of the flow channel and then to flush them out.

The surface temperature at the heat exchanging water-side pipe surface increases in the longitudinal direction of the heater similar to the temperature of the medium. The ratio of heated pipe surface to cross-sectional area of the medium increases, advantageously continuously. As a result, the temperature gradient decreases continuously within the medium cross-sectional area.

In the case of thick-film heating, the length-specific heating power of the heating element (W / cm) can be structurally designed or changed. Advantageously, it is constant. The area performance of the heating conductor (W / cm ² ) and likewise the heat exchanging water-side pipe surface can sink in the course of the heating element. Furthermore, the temperature difference in the interface area between the medium and the water-side pipe surface decreases. This reduces the tendency to vapor bubble formation.

In the case of full-surface thin-film or thick-layer heating, the length-specific heating element output (W / cm) is advantageously constant or may even decrease over the line length. The area performance (W / cm ² ) of the heating elements and thus also the heat exchanging surface remains constant over the length of the heater. In the hot water zone, a cautious transfer of heat to the medium or water takes place due to the increased flow velocity and the reduced flow cross section. A vapor bubble formation and the resulting noise is low. This minimizes the formation of deposits in this potentially hazardous area. In the case of formation of deposits, these are largely removed by the high flow velocity in this zone.

Due to the good heat transfer between heating element, pipe and water, especially in the hot water zone in conjunction with the reduced area performance of the heating conductor, the surface temperature of the heating elements is relatively low. As a result, the radiation of heat energy and the release of heat energy by convection is low.

The use of a flattened tube with continuously reduced cross-sectional area causes in the inlet a minimized flow resistance, which slowly increases only slowly with the requirement of the cross-sectional constriction. Flow-favorable noise-generating turbulences are avoided. This enables a hydraulically energy-efficient flow pattern.

The choice of geometry as a flattened tube with a small diameter in one piece and a single material, advantageously from a cylindrical or round cylindrical tube, generally allows a minimized amount of material and insert mass. Consequently, the heating element mass to be heated is low. The heating time is accordingly short, the hot water is provided within a very short time. Water losses are minimized by the steep temperature rise curve. Especially with frequent removal of small amounts of hot water per process, this advantage comes especially to fruition.

These and other features will become apparent from the claims but also from the description and drawings, wherein the individual features each alone or more in the form of sub-combination in one embodiment of the invention and in other areas be realized and advantageous and protectable Represent embodiments for which protection is claimed here. The subdivision of the application into individual sections as well as intermediate headings does not restrict the general validity of the statements made thereunder.

Brief description of the drawings

Fig. 1

eine Schrägansicht auf eine erste Ausführung einer erfindungsgemäßen Durchfluss-Heizeinrichtung mit flacher werdendem Durchflusskanal und Querschnitten an drei Stellen,

Fig. 2

eine zweite Ausführung einer erfindungsgemäßen Durchfluss-Heizeinrichtung mit noch mehr Windungen und aufgesetzten Temperatursensoren,

Fig. 3

eine weitere alternative Ausführung einer erfindungsgemäßen Durchfluss-Heizeinrichtung mit anderem Aufbau,

Fig. 4

eine vierte Ausführung einer erfindungsgemäßen Durchfluss-Heizeinrichtung mit wiederum anderem Aufbau und

Fig. 5

einen Schnitt durch die Durchfluss-Heizeinrichtung gemäß Fig. 4.

Embodiments of the invention are shown schematically in the drawings and are explained in more detail below. In the drawings show:

Fig. 1

3 is an oblique view of a first embodiment of a flow heater according to the invention with a flattening flow channel and cross sections in three places,

Fig. 2

a second embodiment of a flow heater according to the invention with even more turns and mounted temperature sensors,

Fig. 3

a further alternative embodiment of a flow heater according to the invention with a different structure,

Fig. 4

a fourth embodiment of a flow heater according to the invention with in turn another structure and

Fig. 5

a section through the flow heater according to Fig. 4 ,

Detailed description of the embodiments

In Fig. 1 a flow heater 11 according to the invention is shown. It consists of an elongate tube 12 which is bent at two loops 18 and has an inlet 13 and an outlet 15. Here, according to the arrow, water flows through for heating in the flow passage 17 extending between the inlet 13 and the outlet 15. From the cross sections above in Fig. 1 gem. Section AA can be seen that at the inlet 13, as well as advantageous at the outlet 15, a cross section is circular. In particular, the flow channel 17 is formed from such a circular tube 12 by the flat rolling described above.

Shortly after the inlet 13, the flow cross-section becomes flatter, see section BB. Here the height is only about half the width. Subsequently, the cross section becomes ever flatter, as can be seen on the section CC, where the height is only about one fifth of the width. At this last, very shallow section then joins the round outlet 15 again. Inlet 13 and outlet 15 can thereby be made by a one-piece tube 12, that they are not rolled flat or pressed flat. Alternatively, they may be welded or otherwise connected as separate parts. For this purpose, transition regions 14 can serve at the inlet 13 and 16 at the outlet 15.

It can be seen from the cross sections that from the area with the section BB to the area with the section CC, this cross section not only becomes ever flatter, but also flat and flat at the top and bottom. In this respect, heating elements 20a, 20b and 20c can be provided on three straight heating sections 19a, 19b and 19c at least on one side, advantageously on both sides, ie opposite one another. They cover approximately the width of the planar top of the heating sections 19 and their straight length to the bends. The heating elements 20 can be applied to the usually made of metal pipe 12 of the flow channel 17 by conventional thick-film method. This is for example on the EP 933626 A1 , the EP 1152639 A1 or the DE 102007058833 A1 explicitly referenced. The temperature sensors are formed in a generally known manner, advantageously also printed.

The three heating elements 20a, 20b and 20c are connected in series with electrical terminals 22, which, since they are known in the art, need not be explained in detail. For series connection, connecting conductors 24 are provided along the loops 18, in which the heating elements just do not run. These overlap the heating elements 20a to c according to the electrical contacting, it does not matter which layer overlaps which. Advantageously, the connecting conductors 24 overlap on the heating elements 20, so that they can rest directly on the outside of the heating sections 19a to c for better heat input. With regard to the application method for the heating elements, reference is also made to the above-mentioned prior art.

As an alternative to a structurally predetermined series connection, basically some or all of the heating elements may also be connected separately and routed to an interconnection device. This can interconnect them in any way, for example, in mixing circuits of serial and parallel interconnection. Likewise, they can also be controlled with different performance, for example, be individually controlled for each performance.

In Fig. 2 an alternatively formed flow heater 111 is shown with a tube 112 which is bent with five loops 118 and thus has six straight heating sections 119 a to f and also an inlet 113, an outlet 115 and corresponding transition regions 114 and 116th

On the straight heating sections 119a to f, heating elements 120a to 120f are mounted. According to the flatter and widening flow channel 117, the heating elements 120, as well as in Fig. 1 , towards the outlet 115 towards wider and wider. As a result, the surface temperature decreases and the ratio of heated surface to the cross-sectional area of the medium becomes ever larger, so that the temperature gradient decreases within the cross-sectional area. Advantageously, a length-specific heating power of the heating elements 120 is the same, although of course, in principle, they can also be set differently by changing the width of the heating elements or the thickness or the composition. However, this means that all the heating elements 120a to f generate the same power, only just along the direction of flow of the water to be heated to distribute over a larger area. In Fig. 2 It is also easy to see how the connecting conductors 124 are applied along the loops 118, which interconnect all the heating elements 120 in series. Here, it is easy to imagine how at the ends of the heating elements contact fields are provided with welded leads, connected to an aforementioned interconnection device goes with adjustable power control for each heating element 120 and their arbitrary interconnection.

In Fig. 2 It can also be seen that a plurality of temperature sensors 126a to e are provided on the heater 111. Although these can also be provided on both sides, as advantageous the heating elements 120 itself, but it is also sufficient to one. With the temperature sensors 126, the temperature can be detected at their respective mounting locations. Thus, the temperature sensor 126a probably still detects the initial temperature of the introduced, usually cold water. A slight heating by the heating element 120a is already detected at the temperature sensor 126b. At the temperature sensors 126c and 126d, the absolute temperature can be measured directly on the heating element 120f. If the temperature in normal use exceeds a certain limit, this indicates a calcification of the heat-exchanging inner wall of the pipe. Then countermeasures can be taken automatically or this state is displayed to an operator.

Exceeding a significantly higher limit value indicates an impermissible excess temperature of the heating element 120f. At the temperature sensor 126e, the temperature of the water exiting at the outlet 115 can be detected. By means of the temperature sensors 126 can thus take place in addition to a known temperature measurement performance and thus temperature control.

A modification of the flow heater 111 according to FIG Fig. 2 can still be done by the loops 118 occupy a slightly larger arc angle than 180 °, for example, 190 ° or so much that they rest against the respective adjacent loops. Inlet 113 and outlet 115 thus also move closer together, where they can continue to run either parallel or can also include an angle. The meander shape does not just make one achieved more compact training, but at the same time achieved a very good turbulence or flow through the water with optimal mixing, so that exits at the outlet 115 constantly heated water. A possible power density of the heating elements 120 according to Fig. 2 can go from 50 W / cm ² at the heating element 120a up to 40 W / cm ² at the heating element 120f, advantageously with steps in steps of 2W / cm ² _.

In a further flow-through heater 211 according to Fig. 3 Again, first a substantially circular tube 212 having inlet 213 and outlet 215 has been flattened except for the inlet and outlet of increasingly flatter cross-section and lesser height and greater width, respectively. Subsequently, it has been wound up substantially helically with directly adjacent turns, to form a total of a kind of cylindrical surface. Through the extension of the outlet 215 is then led out again so that it is parallel and adjacent to the inlet 213. The heating elements 220a to f are at least on the outside, so in this case only one side, applied and cover advantageously a large part of a Windungsumgangs, so for example by about 300 °. The remainder is then in turn bridged by the connecting conductors 224 accordingly Fig. 2 , here just in a circumferential arrangement.

Alternatively, as it were, a single heating element may be provided which extends over the entire length of the tube 212 between the inlet 213 and the outlet 215 or, more precisely, between the first temperature sensor 226a and the last temperature sensor 226e. An application of the heating elements 220, similar to connecting conductors 224, can be done easily in the usual manner due to the round cylindrical, substantially flat outer surface.

The advantage of the construction according to Fig. 3 This is because a very compact arrangement and size can be achieved at large Length of the tube 212 and large total heating power. Inlet 213 and outlet 215 are also very close to each other.

Yet another embodiment of a flow heater 311 is off Fig. 4 to be seen in an oblique view. This shape of the tube 312 is essentially due to the fact that approximately a heating device according to Fig. 2 is rolled up to form a cylindrical cylindrical surface. This is in the schematic sectional view Fig. 5 to see. Inlet 313 and outlet 315 are again, similar to FIG Fig. 3 , provided in the axial direction. On the outwardly facing sides of the tube 312 eight heating elements 320a to 320h are provided. These heating elements 320a to 320h are in turn electrically connected or connected in series via connecting conductors 324 on the loops 318. By the in Fig. 5 The construction shown, the meander shape accordingly Fig. 2 with very good mixing of the heated water with the compact, round cylindrical curved form of Fig. 3 be combined.

Out Fig. 5 It can also be seen that the flow area of the pipe 312 and the flow heater 311 from the inlet 313 to the outlet 315 not only becomes narrower as shown in FIGS Fig. 1 , but is also bent kidney-like. However, this is not very difficult to produce and has the advantage that the outer surface is actually round cylindrical. As a result, it can be printed very well with the heating elements 320 and the connecting conductors 324.

Claims (14)

Flow heater for heating a flowing medium, in particular a liquid such as water, wherein the heater has a flow channel for the medium to be heated and at least one heating element having a large interface with the flow channel, the flow channel is open at the beginning and at the end and is closed in between, characterized in that the flow channel has a decreasing over its length cross-sectional area and substantially constant circumference. Flow heater according to claim 1, characterized in that the cross-section or the flow channel along its longitudinal extent becomes flatter. Flow heater according to claim 1 or 2, characterized in that the cross-sectional area along the flow channel decreases from a maximum cross-sectional area to a minimum cross-sectional area, wherein preferably the minimum cross-sectional area is at least 20% of the maximum cross-sectional area, in particular at least 40%. Flow heater according to one of the preceding claims, characterized in that the height of the flow channel along its length from a maximum channel height to a minimum channel height decreases, in particular, the minimum channel height is at least 20% of the maximum channel height, preferably at least 40%. Flow heating device according to one of the preceding claims, characterized in that a change in the Cross-sectional area or the height of the flow channel is approximately evenly, preferably strictly monotonically changing. Flow heating device according to one of claims 1 to 4, characterized in that the cross-sectional area or the height of the flow channel changes stepwise or in jumps, in particular with respective sections of constant cross-sectional area or height, which are preferably connected by transition sections for transfer the cross-sectional areas or heights into each other. Flow heating device according to claim 6, characterized in that heating elements are provided only in sections with a constant cross-sectional area or height. Flow heating device according to one of the preceding claims, characterized in that heating elements are provided only in certain, mutually remote longitudinal regions of the flow channel or at a distance from each other. Flow heater according to one of the preceding claims, characterized in that some or all heating elements are separately controllable and are connected to an interconnection device for interconnection in any kind, preferably in mixing circuits of serial and parallel interconnection. Flow heating device according to one of the preceding claims, characterized in that a channel wall is at least partially flattened outside, in particular on opposite sides, and in particular in the flattened areas, the heating elements are applied. Flow heater according to one of the preceding claims, characterized in that the heating elements are applied in thick film technology. Flow-through heater according to one of the preceding claims, characterized in that the flow channel consists of a tube, in particular of an original round tube which has been flattened on opposite sides and has been formed in its longitudinal course ever flatter. Method for producing a flow-through heater according to one of the preceding claims, characterized in that the flow channel is formed from a tube, in particular from a round tube, which is flattened on opposite sides and is formed in its longitudinal course ever flatter. A method according to claim 13, characterized in that the flattened tube is bent prior to the application of heating elements with loops in the longitudinal direction, preferably in meandering form.

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