DE102018133341A1 - Heating unit for electrically conductive liquid heating medium, electrode for such a heating unit and corresponding heating device and heating circuit - Google Patents

Abstract

The invention relates to an electrode (30, 30a, 30b, 30c) for a heating unit (1), in particular for an instantaneous water heater, for heating an electrically conductive liquid heating medium, a heating unit (1, 1a, 1b, 1c) and a heating device ( 3) and a heating circuit (100). The electrode (30, 30a, 30b, 30c) is made of steel and has a cylindrical rod-shaped electrode base body (34) with two opposite end regions (31, 32) and a profile region (33) arranged between them, the electrode base body (34) in the profile region (33) has a longitudinal profile with at least one circumferential notch (61, 62, 63), in particular with a plurality of circumferential notches (61, 62, 63). The heating unit (1, 1a, 1b, 1c) comprises an electrically insulating and fluid-tight housing (10) which has a flow chamber (20) extending along a longitudinal axis (A) for an electrically conductive liquid heating medium with at least one inflow opening (14) and delimited at least one outflow opening (15), a first electrode (30) with a cylindrical rod-shaped electrode base body (34) and a second electrode (40), which extends radially spaced at least in sections around the first electrode (30), wherein

Description

The invention relates to an electrode for a heating unit for heating a liquid heating medium, a corresponding heating unit, in particular an instantaneous water heater and a heating device and a heating circuit.

Continuous-flow heaters for heating electrically conductive liquids, in particular water, are known from the prior art, which heat a liquid flow by means of electrodes immersed therein by electrical current. The liquid to be heated serves as an electrolyte, its electrical conductivity or, conversely, its specific resistance, influencing the heating power. Movable charge carriers present in the electrolyte enable current to flow between the electrodes. Such instantaneous water heaters can be operated in the low-voltage range.

Heating with electrical current, both for hot water preparation and for heating commercial and / or living spaces, is becoming more energetically and economically attractive due to the increasing decentralized generation of electrical current by photovoltaics, wind power or the like.

From the US 3,885,125 A a method for electrically heating a liquid heating medium in an annular chamber is known.

From the US 2605381 A a water boiler with electrodes is known, three conductive electrodes being arranged around a central neutral conductor.

The DE 2426196 A1 describes electrodes for water heating, each inner electrode being surrounded concentrically by an outer electrode in the form of a jacket which is open on both ends. A similar arrangement describes the DE 2 300 561 A1 .

From the WO 2009/013279 A2 an electrical instantaneous water heater for conductive liquids is known with three conductive electrodes and a neutral electrode installed in a hermetically sealed body and electrically insulated from the body.

The instantaneous water heaters known from the prior art have the disadvantage that the electrodes used are not optimal with regard to heating the liquid heating media as efficiently as possible. In addition, these instantaneous water heaters are relatively complex in construction and therefore expensive to manufacture.

Starting from this prior art, the present invention has the task of providing an electrode for a heating unit for an electrically conductive liquid heating medium and a heating unit for an electrically conductive liquid heating medium which are as efficient as possible with regard to the heating of the heating medium. In addition, the heating unit should be constructed as simply as possible.

This object is achieved by an electrode according to claim 1, a heating unit according to claim 9, a heating device according to claim 23, a heating circuit according to claim 24 and a use of such an electrode, heating unit or heating device according to claim 26.

In particular, the object is achieved by an electrode for a heating device, in particular for an instantaneous water heater, for heating an electrically conductive liquid heating medium, the electrode being made of steel, preferably of a steel alloy comprising chromium and vanadium, and a cylindrical rod-shaped, preferably round, electrode base body with two opposite end regions and a profile region arranged between them, the electrode base body having a longitudinal profile in the profile region with at least one circumferential notch, in particular with a plurality of circumferential notches.

One idea of the invention is to increase the efficiency of the electrical heating of a liquid medium flowing along the electrode by forming a cylindrical rod-shaped electrode with a specific longitudinal profile (i.e. the profile of the cross section in the longitudinal direction of the electrode). According to the invention, therefore, at least one circumferential notch of the electrode base body is provided.

A circumferential notch can be understood to mean a depression in the circumferential direction, ie in particular a local cross-sectional reduction in the longitudinal direction. Conversely, the area between two circumferential notches could also be referred to as a circumferential projection (local increase in cross-section in the longitudinal direction). A notch is not to be understood as limiting in the sense of a tapered incision (triangular), but in particular also includes polygonal (for example rectangular) and round or rounded shapes of a notch cross section. In particular, a circumferential notch extends in relation to an (imaginary) outer enveloping circle diameter of the electrode base body toward a central axis of the electrode. The at least one circumferential notch preferably extends around the entire circumference of the cylindrical rod-shaped electrode, but can also extend only in sections over the Scope. The electrode body or the electrode is preferably round, in particular circular, the peripheral diameter in particular varying over the length of the electrode.

The electrode base body or the electrode is preferably a (one-piece) solid rod (not a hollow rod), in particular made of a uniform material, wherein the electrode can be coated or surface-treated with another material (e.g. with a noble metal such as platinum or titanium). A preferred steel alloy with chrome and vanadium is a steel with the designation 115CrV3 (so-called silver steel).

The heating medium is in particular an electrolytic aqueous solution, preferably a sodium hydroxide solution, i.e. Sodium hydroxide (NaOH), or potassium hydroxide solution, i.e. Potassium hydroxide (KOH), dissolved in water, especially distilled water, the electrical conductivity being adjustable by the concentration. The use of other electrically conductive heating media, for example water with added salts, acids or other bases, is also possible.

An electrode according to the invention has the advantage that the longitudinal field with one or more circumferential notches interacts the electrical field generated by the electrode with the flow surrounding the electrode in an efficient manner for heating. As a result, the efficiency of a heating device in which the electrode is used can be increased. In particular, the electric field in the vicinity of the electrode is formed unevenly in the longitudinal direction in accordance with the position, shape, depth and width (longitudinal extent) of the circumferential notches. For example, the electric field is weaker in the area of the circumferential notches than in the area between two circumferential notches (in the area of a circumferential projection) in accordance with the smaller distance to a jacket electrode (second electrode) surrounding the electrode. In this case, in particular in the radially inner region (inside) of the circumferential notch, the electric field is stronger (locally denser field line course) than in the radially outer region (outside) of the circumferential notch. A circumferential indentation can also be used to generate flow structures, such as vortices (recirculations). The distance between the circumferential notches and their notch geometries makes it possible to influence the electrical field on the one hand and the flow in the vicinity of the electrode on the other.

In an advantageous development of the invention, a first circumferential notch has a first notch distance from a second circumferential notch, the second circumferential notch having a second notch distance from a third circumferential notch, the first notch distance being different from the second notch distance. In particular, a first notch distance is less than a second notch distance. The second notch distance is preferably at least or approximately twice as large as the first notch distance. In particular, the longitudinal profile has a circumferential projection (two circumferential shoulders) between the first and the second circumferential notch and between the second and third circumferential notch. Different projections between the circumferential notches produce circumferential projections (longitudinal regions of larger diameter) of different lengths.

In an advantageous development of the invention, the circumferential notches have different notch geometries, which in particular have a rectangular or U-shaped notch profile. The circumferential notches are made in particular by transverse profile plunge cutting. The notch geometries can vary in shape, depth and / or width (in the longitudinal direction of the electrode). In particular, a first circumferential notch is narrower than a second circumferential notch.

In an advantageous development of the invention, the profile area has at least three circumferential indentations, each of different widths and / or each differently spaced from one another, the longitudinal profile being in particular symmetrical to a central plane of the electrode base body. In particular, the circumferential notches are arranged in the longitudinal direction symmetrically to the central plane of the main electrode body. The profile area preferably has an even number of circumferential notches, for example six, eight or ten circumferential notches. In particular, the notch distance increases towards the end regions of the electrode. Preferably, the notch distance between (in the longitudinal direction) centrally (centrally) arranged circumferential notches is approximately the same.

In an advantageous development of the invention, the electrode base body has an inner diameter D _i and an outer diameter D _a has, the circumferential notches radially from the outer diameter D _a to the inner diameter D _i extend. A profile depth of the longitudinal profile is preferably between a twentieth and a quarter, more preferably between a twelfth and an eighth, particularly preferably approximately one tenth of the outer diameter D _a . The profile depth can be understood to mean half the difference between the outer diameter and the inner diameter, or the difference between the corresponding radii. For example, the outer diameter is D _a of the electrode base body 20 mm, while the inner diameter D _i Is 16 mm, which results in a profile depth of 2 mm.

In an advantageous development of the invention, the ratio of the length of the profile area to the outer diameter is between 8 and 4, preferably between 7 and 5, particularly preferably approximately 6, the length of the profile area preferably being between 100 mm and 150 mm, particularly preferably approximately 125 mm. In particular, the length of the electrode base body depends on the heating power required.

In an advantageous development of the invention, the first end area forms a first mounting pin and the second end area forms a second mounting pin, the first mounting pin being longer than the second mounting pin, preferably more than twice as long. The first and / or second mounting pin can be used to make electrical contact with the electrode, for example by contacting a lead wire or an electrically conductive pin, in particular a threaded pin. An elongated mounting pin provides sufficient space for mechanical mounting (storage) on the one hand and an adequate electrical contact area on the other.

In an advantageous development of the invention, the first and / or second end region has an inclined flow guide surface, in particular a chamfer between 30 ° and 45 °, preferably between 35 ° and 40 °. A flow guide surface serves in particular to deflect (deflect) an axial flow against the electrode (radially) in order to reduce the flow resistance of the electrode.

• - ein elektrisch isolierendes und fluiddichtes Gehäuse, vorzugsweise mit hohlzylindrischer Grundform, das eine sich entlang einer Längsachse erstreckende Durchflusskammer für ein elektrisch leitfähiges flüssiges Heizmedium mit mindestens einer Zuströmöffnung und mindestens einer Abströmöffnung begrenzt,
• - eine, vorzugsweise genau eine, erste Elektrode mit einem zylinderstabförmigen Elektrodengrundkörper, insbesondere eine, vorzugsweise genau eine, erfindungsgemäße Elektrode, und
• - eine zweite Elektrode, die sich radial beabstandet zumindest abschnittsweise um die erste Elektrode erstreckt, wobei die Elektroden im Gehäuse elektrisch voneinander isoliert aufgenommen sind und das Gehäuse elektrische Anschlüsse zur Verbindung der Elektroden mit je einem elektrischen Potential einer Spannungsquelle, insbesondere einer Dreiphasenwechselspannungsquelle, aufweist und wobei die Elektroden in Richtung der Längsachse verlaufend, sich zumindest im Wesentlichen parallel zueinander erstreckend, angeordnet sind und die Zuströmöffnung und die Abströmöffnung sich in Richtung der Längsachse gegenüberliegend angeordnet sind.

The object is also achieved in particular by a heating unit, in particular an instantaneous water heater, for heating an electrically conductive liquid heating medium for a heating circuit, comprising the following:

• an electrically insulating and fluid-tight housing, preferably with a hollow cylindrical basic shape, which delimits a flow chamber extending along a longitudinal axis for an electrically conductive liquid heating medium with at least one inflow opening and at least one outflow opening,
• one, preferably exactly one, first electrode with a cylindrical rod-shaped electrode base body, in particular one, preferably exactly one, electrode according to the invention, and
• a second electrode, which extends radially spaced at least in sections around the first electrode, the electrodes being accommodated in the housing in an electrically insulated manner from one another and the housing having electrical connections for connecting the electrodes to a respective electrical potential of a voltage source, in particular a three-phase AC voltage source, and wherein the electrodes are arranged running in the direction of the longitudinal axis, extending at least substantially parallel to one another, and the inflow opening and the outflow opening are arranged opposite one another in the direction of the longitudinal axis.

The first electrode is preferably arranged centrally, in particular centrally, in the housing. A single first electrode is preferably provided in one housing. A second electrode can (completely) surround the first electrode, wherein a plurality of second electrodes or (curved) electrode sections can also be arranged around the first electrode. The second electrode is in particular designed as a jacket electrode, wherein it is preferably shaped as a (tubular section) closed (in the circumferential direction) or open hollow cylinder, which is open on both sides in particular in the longitudinal direction. An electrical potential is provided in particular by a voltage source outside of the heating device, preferably by a connection to a voltage source in the low voltage range up to, e.g. 1000 V AC.

An electrically insulating housing consists in particular of a dielectric and dielectric material. A dielectric material can be understood to mean an electrically weak or non-conductive solid, in particular in comparison to the electrical conductivity of an electrically conductive heating medium used. The electrical conductivities of the material of the electrode holder and of the heating medium preferably differ by several orders of magnitude. The flow-through chamber can be understood as a space which can be filled with the liquid heating medium to be heated and which surrounds the basic electrode body. In this respect, the flow chamber is an essentially cylindrical space. A heating unit according to the invention has the advantage that an essentially axial flow flow (main axial flow) is formed between the inflow opening and the outflow opening through the flow chamber, which flows along the cylindrical rod-shaped first electrode.

In an advantageous development of the invention, the at least one inflow opening is provided in a first housing cover and / or the at least one outflow opening is provided in a second housing cover, the housing cover or housings in particular is or are connected to a hollow cylindrical housing middle part. The housing cover can form (central shoulders) which are inserted in a form-fitting manner in the middle part of the housing. Seals, for example sealing rings, are preferably arranged between the housing covers and the middle part of the housing and are inserted, in particular, into grooves provided for this purpose on the end face. A multi-part, in particular three-part, housing is easy to manufacture.

In an advantageous development of the invention, the at least one inflow opening and / or the at least one outflow opening are each provided as pairs of separate inflow openings or outflow openings. By designing the inflow and outflow openings in each case as two separate openings, the heating medium can be introduced axially into the flow chamber in a controlled manner or can be discharged from the flow chamber. In addition, between the two inflow and outflow openings, in particular radial material sections or material webs can be formed for mounting recesses for the first electrode, which are arranged centrally in the housing covers.

In an advantageous further development, in particular of this aspect of the invention, the inflow openings and the outflow openings are arranged in pairs, preferably rotated by 90 ° to one another about the longitudinal axis. A twisted arrangement by a different angle, for example by an angle between 45 ° and 90 °, e.g. around 60 ° is possible. This gives the flow a twist, i.e. a circumferential speed component. A uniform flow around the first electrode can thereby be achieved.

In an advantageous development of the invention, the inflow openings and / or the outflow openings are each designed as axial through-channels in the housing cover, the through-channels preferably having an arcuate cross section. As a result, the heating medium is fed in or out in the axial direction. By means of an arcuate cross-section of the through-channels or the outflow and / or inflow opening, the most uniform possible inflow or outflow of the flow from the first electrode is achieved over the circumference.

In an advantageous development of the invention, the inflow openings and / or the outflow openings are arcuate and each extend over an angular range between 90 ° to 150 °, preferably between 110 ° and 130 °, particularly preferably of approximately 120 °. As a result, on the one hand the largest possible area of the inflow and outflow openings and on the other hand a high stability of the housing cover is achieved.

In an advantageous development of the invention, the inflow openings and / or the outflow openings overlap in the radial direction with the cross section of the first electrode. A center circle diameter of the inflow openings and / or the outflow openings is in particular larger than the outer diameter D _a of the electrode body. An inner circle diameter of the (arc-shaped) inflow or outflow openings is in particular smaller than the outer diameter D _a of the electrode base body, which results in a radial overlap of the inflow and outflow openings with the cross section of the first electrode. The flow emerging from the inflow opening or entering the outflow opening is deflected in particular via flow guide surfaces of the electrode base body. This overlap achieves a good flow through the flow chamber, the flow being at least essentially laminar, in particular in the end regions of the first electrode.

In an advantageous development of the invention, the second electrode is designed as a hollow cylindrical jacket electrode, which extends in particular along an inner surface of the housing. In particular, the jacket electrode extends (approximately) over the length of the electrode base body.

In an advantageous development of the invention, the first electrode has mounting pins on both sides, which are received, in particular inserted, in the mounting recesses formed in the housing covers. The mounting recesses are preferably designed (in the middle, i.e. along the longitudinal axis) as axial blind holes.

In an advantageous development of the invention, the first housing cover has a radial through opening for an electrical connecting line, in particular for an electrically conductive threaded pin, which opens into the first mounting recess. Electrical contacting can either be releasable, for example by means of a press or clamp contact, in particular by means of a threaded pin, or firmly connected, in particular in a material manner, for example by means of a soldering point. The set screw can have a contacting tip. In particular, the setscrew is screwed into the through-opening in order to produce an electrical connection for a mounting pin of the first electrode received in the first mounting recess. The through opening can be designed as a bore. In general, an electrical connecting line can be understood to mean a metallic line section for making electrical contact with an electrode from outside the housing, for example in the form of a through the through opening extending wire section or a socket formed in the through hole.

In an advantageous development of the invention, the middle part of the housing has a radial through opening for an electrical connecting line, in particular for an electrically conductive threaded pin. In particular, the setscrew is screwed into the through hole in order to establish an electrical connection for the second electrode (jacket electrode) by making electrical contact with it in particular on an outer peripheral surface.

In an advantageous development of the invention, the housing, in particular the middle part of the housing and the two housing covers, is made of a plastic or a synthetic resin, preferably of polyoxymethylene (POM). POM has high heat resistance, low water absorption and good electrical insulation behavior. The plastic can be glass fiber reinforced.

In an advantageous development of the invention, the second electrode is made from the same material as the first electrode, in particular from steel, preferably from a steel alloy comprising chromium and vanadium. On the one hand, such a steel can be machined well (cutting, in particular by inserting a transverse profile) and, on the other hand, it is suitable for use as an electrode in electrically conductive heating media.

In an advantageous development of the invention, the housing covers each form flange sections with axial through holes, via which the housing covers are clamped together by means of stud bolts, in particular on both sides against the middle part of the housing. Preferably four stud bolts are provided which are distributed uniformly over the circumference and are passed through corresponding through holes. In particular, the stud bolts have threaded sections at the ends and are braced on both sides by means of screw connections to the flange sections.

The object is also achieved in particular by a heating device for an electrically conductive liquid heating medium, comprising three heating units according to the invention, the first electrode of the respective heating unit being connectable to an outer conductor of a three-phase AC voltage source, in particular the second electrode of the respective heating unit each having the neutral conductor the three-phase AC voltage source is connectable.

The individual heating units are preferably connected to one another via pipeline sections connected to the inflow and outflow openings. The individual pipe sections can be connected to one another by connecting pieces with three outlets (to the inflow openings) or three inlets (for heating medium coming from the outflow openings).

• - mindestens eine erfindungsgemäße Heizeinheit nach einem der, vorzugsweise eine erfindungsgemäße Heizvorrichtung,
• - einen Wärmetauscher, insbesondere Plattenwärmetauscher,
• - eine Umwälzpumpe und
• - Rohrleitungen für das Heizmedium, die mit mindestns einer Zuströmöffnung und mindestns einer Abströmöffnung der Heizvorrichtung verbunden sind.

The object is also achieved in particular by a heating circuit for an electrically conductive liquid heating medium, in particular as the primary circuit of a heating system for living and / or commercial spaces or for hot water preparation, comprising:

• at least one heating unit according to one of the, preferably a heating device according to the invention,
• a heat exchanger, in particular a plate heat exchanger,
• - a circulation pump and
• - Pipes for the heating medium, which are connected to at least one inflow opening and at least one outflow opening of the heating device.

The heating device of the heating circuit preferably has three heating units according to the invention, the first electrode of the respective heating unit being connected to an outer conductor of a three-phase AC voltage source. In particular, the second electrodes of the heating units are connected to the neutral conductor of the three-phase AC voltage source.

A heating circuit with a heating device, a heat exchanger, a circulation pump and pipes for the heating medium is known from the prior art. A combination with a heating device according to the invention results in the same advantages for a heating circuit according to the invention as have already been described in connection with the electrode according to the invention and the heating unit. In particular, a heating circuit can be operated as efficiently as possible in terms of energy.

In particular, the heating circuit according to the invention is thermally coupled to a secondary circuit via a heat exchanger. The heat generated in the primary circuit by the heating device according to the invention is transferred to the secondary circuit via the heat exchanger. In the secondary circuit, in particular, another, preferably electrically non-conductive, heating medium itself is heated for consumption, for example water as hot water, or for heating living and / or commercial spaces, in particular via radiators. In particular, the heating circuit according to the invention can be used as a primary circuit in a Heating system can be easily retrofitted with an existing secondary circuit.

In an advantageous development of the invention, the heating medium has an electrical conductivity between 10 μS and 10000 μS, preferably between 10 μS and 1000 μS, further preferably between 10 μS and 500 μS, further preferably between 50 μS and 200 μS, particularly preferably of approximately 150 µS (µS: microsiemens, ie 1 × 10 ^-6 Siemens). In this way, the heating device or the heating circuit provides sufficient heating power for heating when supplying voltages in the low-voltage range, in particular when connecting to a household single-phase AC voltage from 220 V to 230 V or when connecting to a three-phase AC voltage from 380 V to 400 V. of residential and / or commercial premises. The heating medium is preferably an electrolytic aqueous solution, preferably a sodium hydroxide solution, ie sodium hydroxide (NaOH), or potassium hydroxide solution, ie potassium hydroxide (KOH), dissolved in water, in particular distilled water, the electrical conductivity being adjustable by the concentration.

The object is also achieved in particular by using an electrode according to the invention, a heating unit according to the invention or a heating device according to the invention for heating an electrically conductive liquid heating medium of a heating circuit of a heating system for living and / or commercial spaces.

• 1a eine schematische Darstellung einer Ausführungsform einer erfindungsgemäßen Elektrode in einer Seitenansicht;
• 1b eine schematische Darstellung der Elektrode nach 1a in einer perspektivischen Ansicht;
• 2 eine schematische Darstellung einer Ausführungsform einer erfindungsgemäßen Heizeinheit in einer Schnittansicht entlang der Linie B-B in 3;
• 3 eine schematische Darstellung der Heizeinheit nach 2 in einer Draufsicht;
• 4 eine schematische Darstellung der Heizeinheit nach 2 in einer Schnittansicht entlang der Linie A-A in 3;
• 5 eine schematische Darstellung der Heizeinheit nach 2 in einer perspektivischen Ansicht;
• 6 eine schematische Darstellung des Gehäusemittelteils der Heizeinheit nach 2 in einer perspektivischen Ansicht;
• 7a eine schematische Darstellung eines Gehäusedeckels der Heizeinheit nach 2 in einer Seitenansicht;
• 7b eine schematische Darstellung des Gehäusedeckels nach 7a in einer perspektivischen Ansicht;
• 8 eine schematische Darstellung einer Ausführungsform eines erfindungsgemäßen Heizkreises mit einer an eine Dreiphasenwechselspannungsquelle angeschlossenen Heizvorrichtung.

Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. Here show:

• 1a a schematic representation of an embodiment of an electrode according to the invention in a side view;
• 1b is a schematic representation of the electrode 1a in a perspective view;
• 2nd is a schematic representation of an embodiment of a heating unit according to the invention in a sectional view along the line BB in 3rd ;
• 3rd a schematic representation of the heating unit after 2nd in a top view;
• 4th a schematic representation of the heating unit after 2nd in a sectional view along the line AA in 3rd ;
• 5 a schematic representation of the heating unit after 2nd in a perspective view;
• 6 a schematic representation of the middle part of the housing of the heating unit 2nd in a perspective view;
• 7a is a schematic representation of a housing cover of the heating unit 2nd in a side view;
• 7b a schematic representation of the housing cover after 7a in a perspective view;
• 8th is a schematic representation of an embodiment of a heating circuit according to the invention with a heating device connected to a three-phase AC voltage source.

In the following description of the invention, the same reference numerals are used for identical and identically acting elements.

The 1a and 1b show an electrode according to the invention 30th (hereinafter also as 30a , 30b or 30c denotes) for heating an electrically conductive liquid heating medium, which the electrode 30th flows around or flows along it. The electrode 30th has a cylindrical electrode body 34 to which a first end area 31 and a second end area 32 connect. The two end areas 31 , 32 form circular cylindrical mounting pins 35 or. 36 for holding the electrode 30th in one housing 10 a heating unit 1 (or. 1a , 1b , 1c ) out. Beveled flow control surfaces 64 , 65 are designed as chamfers with a slope of approximately 35-40 °. The electrode 30th is designed as a solid steel rod, preferably a steel alloy comprising chrome and vanadium. In a profile area 33 between the end areas 31 , 32 has the electrode base 34 a longitudinal profile with several circumferential notches 61 , 62 , 63 on. The longitudinal profile is symmetrical to a central plane M and comprises a total of six circumferential notches 61 , 62 , 63 . The circumferential notches 61 , 62 , 63 are spaced apart from one another to a different extent and each have a rectangular notch geometry. The notch profile could also be rounded, in particular U-shaped. For example, the perimeter notches 61 , 62 , 63 each between 7 mm and 8 mm wide and about 2 mm deep, which is a profile depth T of 2 mm. The circumferential notches 61 , 62 , 63 extend from an outer diameter D _a , which is for example 20 mm, up to an inner diameter D _i , which is 16 mm, for example. The first notch distance a1 between a first circumferential notch 61 and a second perimeter notch 62 is approximately half the second notch distance a2 between the second perimeter notch 62 and the third perimeter notch 63 . The first notch distance a1 is 7, for example mm, while the second notch distance a2 Is 14 mm. The basic electrode body 34 is approximately 125 mm long. The longitudinal profile of the electrode 30th influenced by a suitable choice of the notch distances a1 , a2 and the notch geometries of the circumferential notches 61 , 62 , 63 on the one hand the resulting electric field and on the other hand the flow in the vicinity of the electrode 30th . This can increase the efficiency of heating the electrode 30th be increased in the flowing heating medium.

The 2nd to 5 show a heating unit according to the invention 1 (in 8th With 1a , 1b or 1c designated). The housing 10 the heating unit 1 has a cylindrical basic shape with a longitudinal axis A and is in three parts with a first housing cover 12th , a second housing cover 13 and a hollow cylindrical housing middle part arranged between them 11 (please refer 6 ) executed. The housing 10 is preferably made of the electrically insulating material polyoxymethylene (POM). There are seals between the individual parts of the housing 80 , here sealing rings, provided in the circumferential grooves on the end face 81 are inserted. The bracket recess 16 with the electrical connection for the first electrode 30th is via a seal designed as an O-ring 82 separately sealed. The housing cover 12th , 13 each have flange sections 18th or. 19th in which axial through holes 71 are provided. A total of four outside the middle part of the housing 11 Stud bolts distributed over the circumference 70 are for bracing the flange sections 18th , 19th by means of screw connections through the through holes 71 passed through.

The housing 10 has inflow openings 14 , 14a , 14a and outflow openings 15 , 15a , 15b for an electrically conductive liquid heating medium on the flow chamber 20 flows in the axial direction. The electrically conductive heating medium is preferably sodium hydroxide solution with distilled water and is in the flow chamber 20 electrically heated by creating an electric field between the centrally located first electrode 30th (or. 30a , 30b , or 30c ) and the first electrode 30th radially surrounding second electrode 40 is directed. The second electrode 40 is designed as a hollow cylindrical jacket electrode open on both sides, ie as a round tube, and extends along the inside of the middle part of the housing 11 . The second electrode 40 is about 135 mm long and has an inner diameter of approx. 35 mm. The electrode 40 is made of the same material as the electrode 30th . The previously related to the 1a and 1b described electrode 30th is on both sides with the first and second mounting pins 35 , 36 in the first and second bracket recesses 16 or. 17th the housing cover 12th , 13 recorded, namely plugged in. The bracket recesses 16 and 17th are centered as blind holes. In this embodiment, the flow chamber has 20 a volume of approximately 0.1 l. The volume can also have, for example, between 0.05 l to 1 l or up to 10 l. The electrical conductivity of the heating medium is approximately 150 µS. The heating power of the heating device can be, for example, in the range from 10, 15 or 30 kW. The heating unit 1 can be used to heat commercial and residential spaces.

In the housing covers 12th , 13 are axial through-channels 21st , 22 trained to the inflow openings 14 , 14a , 14b or outflow openings 15 , 15a , 15b to lead. The inflow openings 14 and outflow openings 15 are each as a pair of two separate arcuate inflow openings 14a , 14b or outflow openings 15a , 15b educated. The inflow and outflow openings 14a , 14b or. 15a , 15b are each 90 ° around the longitudinal axis A arranged rotated to each other and each extend over an angular range of approximately 120 °. In the central areas of the housing cover 12th , 13 are the mounting recesses 16 , 17th arranged. The inflow and outflow openings 14 or. 15 overlap in the radial direction with the cross section of the first electrode 30th . The first housing cover 12th is in the 7a and 7b shown. The housing covers face on the axial outer sides 12th , 13 recesses with internal threads for connecting pipes.

The first electrode 30th is via a connecting cable 50 through a radial through opening 52 in the first housing cover 12th is provided and in the first mounting recess 16 flows into, electrically contacted. The second electrode 40 is via a connecting cable 51 acting as a radial through hole 53 in the middle part of the housing 11 is made, electrically contacted. In the through opening 53 is a reducing nipple 54 used. The connecting lines 50 and 51 are each available as metallic grub screws 50 , 51 with contact tips. On the peripheral outer surfaces of the first housing 12th and the middle part of the housing 11 are flat connection surfaces 55 for screwing in the set screws 50 , 51 intended.

8th shows a schematic representation of a heating circuit according to the invention 100 with a heat exchanger 101 , a circulation pump 102 , Piping 103 for an electrically conductive heating medium and a heating device according to the invention 3rd , the three previously as a heating unit 1 described heating units according to the invention 1a , 1b , 1c includes. The heating units 1a , 1b , 1c each include an electrode previously described 30th hereinafter referred to as the three electrodes 30a , 30b and 30c are designated. Via an upstream Line crosspiece 105 (three outlets) and a downstream cross piece 106 (three inlets) are the inflow openings 14 or the outflow openings 15 of the individual heating units 1a , 1b , 1c with the pipeline system 103 of the heating circuit 100 connected. The heater 3rd is connected to a voltage source 2nd connected, which is designed as a three-phase AC voltage source. The three outer conductors L1 , L2 , L3 the three-phase AC voltage source are each with a connecting cable 50a , 50b , 50c the first electrodes 30a , 30b , 30c connected. The neutral conductor N is with the connecting cables 51 of the total of three in the heating units 1a , 1b , 1c existing second electrodes 40 connected. The heat exchanger 101 is a plate heat exchanger. The heating circuit 100 is provided here as a primary circuit of a heating system, with the heat exchanger 101 that of the heater 3rd generated heat and stored in the electrically conductive liquid heating medium to a secondary circuit 200 is transmitted, for example for hot water preparation or for heating residential and / or commercial premises.

Reference list

1

Heating unit

2nd

Voltage source

3rd

Heater

10th

casing

11

Middle part of the housing

12th

first housing cover

13

second housing cover

14, 14a, 14b

Inflow opening

15, 15a, 15b

Outflow opening

16

first bracket recess

17th

second bracket recess

18, 19

Flange section

20

Flow chamber

21, 22

Through channel

30, 30a, 30b, 30c

first electrode

31

first end area

32

second end area

33

Profile area

34

Electrode base

35

first mounting pin

36

second mounting pin

40

second electrode

50, 50a, 50b, 50c

Connecting cable

51

Connecting cable

52

Through opening

53

Through opening

54

Reduction nipple

55

Pad

61, 62, 63

Perimeter notch

64, 65

Flow control surface

70

Stud bolts

71

Through hole

72

Screw connection

80, 82

poetry

81

Circumferential groove

100

Heating circuit

101

Heat exchanger

102

Circulation pump

103

Pipeline

105, 106

Line crosspiece

200

Secondary circuit

A

Longitudinal axis

M

Middle plane

T

Profile depth

L1, L2, L2

Outer conductor

N

Neutral conductor

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 3885125 A [0004]
• US 2605381 A [0005]
• DE 2426196 A1 [0006]
• DE 2300561 A1 [0006]
• WO 2009/013279 A2 [0007]

Claims (26)

Electrode (30, 30a, 30b, 30c) for a heating unit (1), in particular for an instantaneous water heater, for heating an electrically conductive liquid heating medium, wherein the electrode (30, 30a, 30b, 30c) is made of steel, preferably of a steel alloy comprising chromium and vanadium, and has a cylindrical rod-shaped, preferably round, electrode base body (34) with two opposite end regions (31, 32) and a profile region (33) arranged between them, wherein the electrode base body (34) has a longitudinal profile in the profile region (33) with at least one circumferential notch (61, 62, 63), in particular with a plurality of circumferential notches (61, 62, 63). Electrode (30, 30a, 30b, 30c) Claim 1 , characterized in that a first circumferential notch (61) has a first notch distance (a1) from a second circumferential notch (62), the second circumferential notch (62) having a second notch distance (a2) from a third circumferential notch (63), the the first notch distance (a1) differs from the second notch distance (a2), the second notch distance (a2) in particular being approximately twice as large as the first notch distance (a1). Electrode (30, 30a, 30b, 30c) Claim 1 or 2nd , characterized in that the circumferential notches (61, 62, 63) have different notch geometries, which in particular have a rectangular or U-shaped notch profile, the circumferential notches (61, 62, 63) being produced in particular by transverse profiling. Electrode (30, 30a, 30b, 30c) according to one of the preceding claims, characterized in that the profile region (33) has at least three circumferential notches (61, 62, 63), each of different widths and / or differently spaced from one another, the Longitudinal profile is in particular symmetrical to a central plane (M) of the electrode base body (34). Electrode (30, 30a, 30b, 30c) according to one of the preceding claims, characterized in that the electrode base body (34) has an inner diameter D _i and an outer diameter D _a , the circumferential notches (61, 62, 63) being radial extend from the outer diameter D _a to the inner diameter D _i , a profile depth (T) of the longitudinal profile preferably being between a twentieth and a quarter, more preferably between a twelfth and an eighth, particularly preferably approximately one tenth of the outer diameter Da. Electrode (30, 30a, 30b, 30c) according to one of the preceding claims, characterized in that the ratio of the length of the profile region (33) to the outer diameter D _{a is} between 8 and 4, preferably between 7 and 5, particularly preferably approximately 6 , wherein the length of the profile area (33) is preferably between 100 mm and 150 mm, particularly preferably approximately 125 mm. Electrode (30, 30a, 30b, 30c) according to one of the preceding claims, characterized in that the first end area (31) forms a first mounting pin (35) and the second end area (32) forms a second mounting pin (36), the first mounting pin (35) is longer than the second mounting pin (36), preferably more than twice as long. Electrode (30, 30a, 30b, 30c) according to one of the preceding claims, characterized in that the first and / or second end region (31, 32) has an inclined flow guide surface, in particular a chamfer between 30 ° and 45 °, preferably between 35 ° and 40 °. Heating unit (1, 1a, 1b, 1c), in particular an electric water heater, for heating an electrically conductive liquid heating medium for a heating circuit, comprising: Flow chamber (20), which extends along the longitudinal axis (A), for an electrically conductive liquid heating medium with at least one inflow opening (14) and at least one outflow opening (15), - one, preferably exactly one, first electrode (30) with a cylindrical rod-shaped main body (34) , in particular a first electrode (30) according to one of the Claims 1 to 8th , and - a second electrode (40) which extends radially spaced at least in sections around the first electrode (30), the electrodes (30, 40) being accommodated in the housing (10) in an electrically insulated manner and the housing (10) in an electrical manner Connections (18, 19) for connecting the electrodes (30, 40) each with an electrical potential of a voltage source (2), in particular a three-phase alternating voltage source, and the electrodes (30, 40) extending in the direction of the longitudinal axis (A) extending at least substantially parallel to one another, and the inflow opening (14) and the outflow opening (15) are arranged opposite one another in the direction of the longitudinal axis (A). Heating unit (1, 1a, 1b, 1c) after Claim 1 characterized in that the at least one inflow opening (14) is provided in a first housing cover (12) and / or the at least one outflow opening (15) is provided in a second housing cover (13), the housing cover (s) (14, 15) is or are connected in particular to a hollow cylindrical housing middle part (11). Heating unit (1, 1a, 1b, 1c) after Claim 1 or 2nd , characterized in that the at least one inflow opening (14) and / or the at least one outflow opening (15) are each provided as pairs of separate inflow openings (14a, 14b) or outflow openings (15a, 15a). Heating unit (1, 1a, 1b, 1c) according to one of the preceding claims, in particular according to Claim 11 , characterized in that the inflow openings (14a, 14b) and the outflow openings (15a, 15a) are arranged in pairs, preferably rotated by 90 ° to one another about the longitudinal axis (A). Heating unit (1, 1a, 1b, 1c) according to one of the preceding claims, characterized in that the inflow openings (14a, 14b) and / or the outflow openings (15a, 15a) each as axial through-channels (21, 22) in the housing cover (12 or 13) are formed, the through channels (21, 22) preferably having an arcuate cross section. Heating unit (1, 1a, 1b, 1c) according to one of the preceding claims, characterized in that the inflow openings (14a, 14b) and / or the outflow openings (15a, 15a) are arcuate and each extend over an angular range between 90 ° to 150 °, preferably between 110 ° and 130 °, particularly preferably of approximately 120 °. Heating unit (1, 1a, 1b, 1c) according to one of the preceding claims, characterized in that the inflow openings (14a, 14b) and / or the outflow openings (15a, 15a) radially with the cross section of the first electrode (30, 30a, 30b, 30c) overlap, a center circle diameter of the inflow openings (14a, 14b) and / or the outflow openings (15a, 15a) in particular being larger than the outer diameter D _{a of} the electrode base body (36). Heating unit (1, 1a, 1b, 1c) according to one of the preceding claims, characterized in that the second electrode (40) is designed as a hollow cylindrical jacket electrode, which extends in particular along an inner surface of the housing (10). Heating unit (1, 1a, 1b, 1c) according to one of the preceding claims, characterized in that the first electrode (30) has mounting pins (34, 35) on both sides, the mounting recesses (16, 17) formed in the housing covers (12, 13) ) are recorded, especially inserted. Heating unit (1, 1a, 1b, 1c) according to one of the preceding claims, characterized in that the first housing cover (12) has a radial through opening (52) for an electrical connection line (50), in particular for an electrically conductive threaded pin, which opens into the first mounting recess (16). Heating unit (1, 1a, 1b, 1c) according to one of the preceding claims, characterized in that the housing middle part (11) has a radial through opening (53) for an electrical connecting line (51), in particular for an electrically conductive threaded pin. Heating unit (1, 1a, 1b, 1c) according to one of the preceding claims, characterized in that the housing (10), in particular the middle housing part (11) and the two housing covers (12, 13), preferably made of a plastic or a synthetic resin made of polyoxymethylene (POM). Heating unit (1, 1a, 1b, 1c) according to one of the preceding claims, characterized in that the second electrode (40) is made of the same material as the first electrode (30), in particular steel, preferably comprising a chromium and vanadium Steel alloy. Heating unit (1, 1a, 1b, 1c) according to one of the preceding claims, characterized in that the housing covers (12, 13) each form flange sections (18, 19) with axial through holes (71) via which the housing covers (12, 13 ) are clamped together by means of stud bolts (70), in particular on both sides against the middle part of the housing (11). Heating device (3) for an electrically conductive liquid heating medium, comprising at least three heating units (1a, 1b, 1c), each according to one of the Claims 9 to 22 , wherein the first electrode (30a, 30b, 30c) of the respective heating unit (1a, 1b, 1c) can be connected to an outer conductor (L1, L2, L3) of a three-phase AC voltage source, in particular the second electrode (40) of the respective heating unit ( 1a, 1b, 1c) can each be connected to the neutral conductor (N) of the three-phase AC voltage source. Heating circuit (100) for an electrically conductive liquid heating medium, in particular as a primary circuit of a heating system for living and / or commercial spaces or for hot water preparation, comprising: - at least one heating unit (1) according to one of the Claims 9 to 22 , preferably a heating device (3) Claim 23 , - a heat exchanger (101), in particular plate heat exchanger, - a circulation pump (102) and - pipes (103) for the heating medium, which are connected to at least one inflow opening (14) and at least one outflow opening (15) of the heating device (3). Heating circuit (100) according to Claim 24 , characterized in that the heating medium has an electrical conductivity between 10 µS and 10000 µS, preferably between 10 µS and 1000 µS, further preferably between 10 µS and 500 µS, further preferably between 50 µS and 200 µS, particularly preferably of approximately 150 µS . Use of an electrode (30, 30a, 30b, 30c) according to one of the Claims 1 to 8th , a heating unit (1, 1a, 1b, 1c) according to one of the Claims 9 to 22 or a heating device (3) Claim 23 for heating an electrically conductive liquid heating medium of a heating circuit (100) of a heating system for living and / or commercial spaces.

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