EP4013187A1 - Electric gas flow heater and gas flow heater manufacturing method - Google Patents

Abstract

The invention relates to an electric gas flow heater having at least one cylindrical structure, in which at least one channel for the gas line is formed and at least one electric heating element is arranged in the channel of the cylindrical structure, heat being applied by the electric heating element to a gas flowing through the channel heating of the gas and/or for achieving high gas temperatures, the electric heating element having two or more spaced-apart meandering heating grid structure levels perpendicular to the flow direction of the channel and the two or more meandering heating grid structure levels being arranged one after the other in the flow direction in the channel, the individual spaced-apart meander-like heater grid structure levels are connected to one another in a meander-like manner via an electrically conductive intermediate connection and the first and the last of the spaced-apart meander-like embodied th heating grid structure levels have an electrical connector, and the cylindrical structure is designed on its inner wall to accommodate the two or more spaced meandering heating grid structure elements.

Description

The invention relates to an electric gas flow heater having at least one cylindrical structure, in which at least one channel for the gas line is formed and at least one electric heating element is arranged in the channel of the cylindrical structure, heat being applied by the electric heating element to a gas flowing through the channel Heating of the gas and / or to achieve high gas temperatures is transferrable.

Furthermore, the invention relates to a gas flow heater production method for producing an electric gas flow heater according to the invention.

The electric gas flow heater is designed in particular for vertical flow. Horizontal use is also possible. The typical temperature range is gas temperatures from 800 °C to 1200 °C, although the electric gas flow heater described here can also be used at significantly lower or even higher operating temperatures.

Different types of gas flow heaters with different manufacturing processes are known from the prior art .

From the DE 10 2014 102 474 A1 a gas flow heater is known in which an electric heating wire is guided through several individual channels. With this solution, the heating wire is stored in small ceramic tubes and electrically insulated. This type of gas flow heater is relatively expensive due to this complex arrangement and the correspondingly complex manufacturing process.

The European patent application with the file number EP20159612.9 discloses a correspondingly simpler manufacturing variant for a gas flow heater known in the prior art, which is electrically heated. The heating element is made from a pre-bent heating wire which is dipped in a wax which in turn forms a layer on the conductor. The wire is cast in concrete or similar material with a layer of wax and the wax is then melted out to form channels with heating wires inside, allowing for easier manufacture at reduced cost.

Also known in the prior art are meandering heaters made of graphite which are bent into tubes. Solutions of this type are offered by the company SGL Carbon, for example (cf. https://www.sglcarbon.com/loesungen/anmeldung/hochtemperaturoefen/).

Also known in the prior art are heaters in which a heating wire is arranged in a serpentine manner around a core, the core being arranged in a channel. Solutions of this type are offered, for example, by Tutco Heating Solutions (cf. https://www.tutco.com/cartridge-heaters).

The problems of the electrical gas flow heaters known in the prior art are essentially that the production of the heating elements is both time-consuming and costly and their installation or assembly must be technically complicated.

Furthermore, they are difficult or impossible to maintain or repair and are also very complicated in terms of achieving a uniform temperature at the end of the channel in which the gas is heated.

The present invention is based on the object of providing an electric gas flow heater and a gas flow heater manufacturing method which enables the realization of both small and large, powerful gas heater heating elements with reduced manufacturing complexity and can be operated economically with reduced manufacturing costs.

This object is achieved with a gas flow heater according to the main claim claim 1 and a gas flow heater manufacturing method according to the independent claim.

• das elektrische Heizelement senkrecht zur Strömungsrichtung des Kanals zwei oder mehr beabstandete mäanderartig ausgebildete Heizgitterstrukturebenen aufweist,
  und
• die zwei oder mehr beabstandeten mäanderartig ausgebildeten Heizgitterstrukturebenen in Strömungsrichtung nacheinander in dem Kanal angeordnet sind, wobei die einzelnen beabstandeten mäanderartig ausgebildeten Heizgitterstrukturebenen mäanderartig miteinander über jeweils eine elektrisch leitende Zwischenverbindung verbunden sind und die erste sowie die letzte der beabstandeten mäanderartig ausgebildeten Heizgitterstrukturebenen einen elektrischen Konnektor aufweisen,
  und
• die zylindrische Struktur auf ihrer Innenwand zur Aufnahme der zwei oder mehr beabstandeten mäanderartig ausgebildeten Heizgitterstrukturebenen ausgebildet ist.

According to the arrangement, the electric gas flow heater has at least one cylindrical structure in which at least one channel for gas conduction is formed and at least one electric heating element is arranged in the channel of the cylindrical structure, heat being applied by the electric heating element to a gas flowing through the channel Heating of the gas and / or to achieve high gas temperatures is transferrable, and is characterized in that

• the electrical heating element has two or more spaced, meandering heating grid structure levels perpendicular to the direction of flow of the channel,
  and
• the two or more spaced meandering heating grid structure levels are arranged one after the other in the flow direction in the channel, the individual spaced meandering heating grid structure levels being connected to one another in a meandering manner via an electrically conductive intermediate connection and the first and the last of the spaced meandering heating grid structure levels having an electrical connector,
  and
• the cylindrical structure is formed on its inner wall to accommodate the two or more spaced meandering heating grid structure levels.

Preferably, the electrical heating element can be formed in one piece and/or in one piece and/or in one piece of material. As a result, possible weak points during operation due to joint or connection errors are almost completely ruled out and additional assembly steps are avoided.

The cylindrical structure can be designed on the inside to accommodate the two or more spaced meandering heating grid structure levels, preferably with an internal thread, particularly preferably with a double-threaded internal thread, with the electrical heating element being able to be inserted or removed from the cylindrical structure by rotating the electrical heating element relative to the latter is. The electrical heating element can thus be screwed into the thread. In the installed state, the individual heating grid structure levels are mounted in the threads, with a line-like contact being established between the heating grid structure levels and the threads.

A two-start thread on the inside of the cylindrical structure is advantageous over a single-start thread, since this prevents excessive bending of the heating grid structure planes and ensures good assembly.

The arrangement, in particular the distance between the individual heating grid structure levels arranged adjacent to one another, is selected in such a way that they fit the internal thread of the cylindrical structure. Each level of the heater grid structure levels is held and supported by the internal thread.

The cylindrical structure can be designed in one piece and/or in one piece, but also in several pieces and/or in several parts. The cylindrical structure can preferably be formed from two half-shells which, when put together, form the cylindrical structure. The use of half-shells facilitates the manufacture of the cylindrical structure by molding or molding and sintering a green body, since less complex semi-finished products can be used for molding and post-processing can be avoided.

In an alternative embodiment, the cylindrical structure may not be provided with a thread on its inner wall for accommodating the two or more spaced meandering heating grid structure planes, but rather with an arrangement of grooves. The distances between the grooves are selected in such a way that they match the distances between the meandering heating grid structure planes. A particularly simple assembly is possible with such an arrangement, namely in that the electric heating element is used or laid in a first of the half-shells and then the second half-shell is assembled with the first. The individual, spaced, meandering heating grid structure levels connected to one another in a meandering manner can be arranged at equal distances, in particular in the direction of flow.

• die einzelnen beabstandeten mäanderartig ausgebildeten Heizgitterstrukturebenen weisen eine kreisrunde Einhüllende auf;
• die einzelnen beabstandeten mäanderartig ausgebildeten Heizgitterstrukturebenen sind in ihren Randbereichen breiter als in ihren Innenbereichen ausgebildet;
• der Leiterquerschnitt der Zwischenverbindungen ist deutlich größer als die Leiterquerschnitte der beabstandeten mäanderartig ausgebildeten Heizgitterstrukturebenen.

The electrical heating element can preferably have at least one of the features selected from the following features:

• the individual, spaced, meandering heating grid structure levels have a circular envelope;
• the individual, spaced, meandering heating grid structure levels are wider in their edge areas than in their inner areas;
• the conductor cross-section of the intermediate connections is significantly larger than the conductor cross-sections of the spaced, meandering heating grid structure levels.

Geometrically, the circular shape is particularly preferred, since in this way a plane construct can be formed which can be introduced into the cylindrical structure for receiving in the thread. In particular, it is of particular advantage if the round configuration is formed in combination with the two-start thread on the inside of the cylindrical structure, since this ensures optimum screwability.

An advantage of the design, that the conductor cross-section in the edge areas of the meander-like heating grid structure levels is larger than the conductor cross-sections of the inner heating conductors of the meander-like heating grid structure levels, is the increased service life, whereby this is realized in that less thermal energy is released there due to the larger conductor cross-section, so that the temperature of the heating grid structure levels in the contact area with the cylindrical structure is not critical. The risk of local overheating as a result of poor heat dissipation at the contact points between the electrical heating element and the cylindrical structure is consequently minimized without making a complex ceramic geometry necessary. In connection with the embodiment described above, the conductor cross-section is to be understood exclusively as meaning the width of the electrical webs of the meander structure and not their height. The electrical heating element is preferably formed from sheet metal of substantially constant thickness, for example 0.7mm or 1.0mm.

The cylindrical structure can preferably be designed as an electrical insulator. In this way, the electrical insulation is realized and the electrical heating element is held in one structure at the same time.

The cylindrical structure is particularly preferably formed from technical ceramics and/or concrete and/or aluminum oxide.

In a further preferred variant, the electrical heating element is designed without a support structure, so that the electrical heating element is mounted exclusively in the thread of the cylindrical structure. This represents a significant manufacturing advantage, since only the heating element and the cylindrical structure are manufactured and subsequently have to be merged.

In a further preferred variant, the adjacent heating grid structure levels of the meandering heating grid structure levels are formed in such a way that the openings of the individual heating grid structure levels do not coincide with one another with respect to the direction of flow. In a further preferred variant, the meandering heating grid structure levels are provided with diffuser elements which are integrally formed with the individual heating grid structure levels and/or in one piece and/or made of one piece of material. The flow of the gas to be heated and the heat input into the gas can be influenced via the arrangement of the openings of the individual levels and via diffuser elements, and the temperature distribution in the gas can thus be optimized.

The electrical heating element can in particular be made of ^VDM® Aluchrom W, ^Kanthal® APM or another aluminum-containing ferritic chrome steel for use at temperatures of up to 1250°C. However, other alloys are also conceivable which have sufficiently high dimensional stability in the selected temperature range and preferably form an oxide layer that protects the surface during operation and in the presence of oxygen.

The cylindrical structure can be designed with openings such that these connection means for electrical contacting of the connectors of the first or last heating grid structure level can be passed through and electrically connected to them, so that the electrical heating element can be supplied with an electrical energy source.

In principle it can be said that the gas flow heater described here essentially consists of two functional components, namely the cylindrical structure and the electric heating element in double meandering form, namely once in the plane perpendicular to the direction of flow and once along the direction of flow.

• a) Herstellen der zylindrischen Struktur;
• b1) Herstellen des elektrischen Heizelements durch Biegen mittels der folgenden Schritte:
  • Herstellen eines Rohlings durch Stanzen und/oder Lasern und/oder Schneiden aus einem Blech, wobei miteinander über Zwischenverbindungen verbundene mäanderartig ausgebildete Heizgitterstrukturebenen ausgebildet werden;
  • Biegen des Rohlings jeweils im Bereich der Zwischenverbindungen um jeweils 180°, so dass eine zylinderförmige Struktur aus planparallelen mäanderartig ausgebildeten Heizgitterstrukturebenen entsteht, deren Abstand durch die Zwischenverbindungen gewahrt wird;
  oder
• b2) alternativ zum Biegen Herstellen des elektrischen Heizelements durch Schweißen mittels der folgenden Schritte:
  • Herstellen mehrerer mäanderartig ausgebildeter Heizgitterstrukturebenen durch Stanzen und/oder Lasern und/oder Schneiden aus einem Blech,
  • mäanderartiges Verschweißen der mehreren mäanderartig ausgebildeten Heizgitterstrukturebenen unter Verwendung von Zwischenverbindungen;
• c) Montage des Gas-Strömungsheizers mittels der folgenden Schritte:
  • Einschrauben oder Einsetzen des elektrischen Heizelements in die zylindrische Struktur; und
  • elektrisches Kontaktieren des elektrischen Heizelements.

According to the method, the gas flow heater production method for producing an electric gas flow heater according to the invention has at least the following steps:

• a) making the cylindrical structure;
• b1) Making the electrical heating element by bending using the following steps:
  • Production of a blank by stamping and/or lasering and/or cutting from sheet metal, meandering heating grid structure levels connected to one another via intermediate connections being formed;
  • Bending the blank in each case in the area of the intermediate connections by 180°, so that a cylindrical structure of plane-parallel meandering heating grid structure levels arises, the distance between which is maintained by the intermediate connections;
  or
• b2) as an alternative to bending, manufacture the electric heating element by welding using the following steps:
  • Production of several meandering heating grid structure levels by punching and/or lasering and/or cutting from sheet metal,
  • meander-like welding of the plurality of meander-like heating grid structure levels using intermediate connections;
• c) Assemble the gas flow heater using the following steps:
  • screwing or inserting the electrical heating element into the cylindrical structure; and
  • electrically contacting the electrical heating element.

The cylindrical structure can be made by molding or molding and sintering a green body. This method makes it possible to produce a corresponding gas flow heater inexpensively and with as few process steps as possible. In particular, the dimensioning can take place by adjusting the number of levels of heating grid structure levels. In addition, the separate manufacture of the heating element and the cylindrical structure also makes it possible to manufacture the two components independently of the location, with these only having to be screwed together during final assembly, i.e. the electrical heating element in the cylindrical structure. The process also enables the production of a three-dimensional heating element in which only the principle of series connection is used. Parallel circuits, which require the use of higher currents, are avoided.

Abb. 1

eine schematische Darstellung eines Rohlings des elektrischen Heizelements in geschnittener bzw. ausgestanzter Form;

Abb. 2

eine schematische Darstellung des Rohlings des elektrischen Heizelements aus Fig. 1 in mäanderartig gefalteter Form in Seitenansicht;

Abb. 3

eine schematische Darstellung des in Fig. 2 gezeigten mäanderartig gefalteten elektrischen Heizelements in isometrischer Darstellung;

Abb. 4

eine schematische Darstellung eines alternativen Rohlings des elektrischen Heizelements in geschnittener bzw. ausgestanzter Form, wobei zusätzliche Stege für das Handling während des Herstellungsprozesses vorgesehen sind;

Abb. 5

eine schematische Darstellung des in Fig. 4 gezeigten nun mäanderartig gefalteten elektrischen Heizelements in isometrischer Darstellung;

Abb. 6

eine schematische Darstellung der zylindrischen Struktur in einer geschnittenen Seitenansicht;

Abb. 7

eine schematische Darstellung eines eingebauten elektrischen Heizelements in einer zylindrischen Struktur in Draufsicht;

Abb. 8

eine schematische Darstellung eines eingebauten elektrischen Heizelements in einer zylindrischen Struktur in einer geschnittenen Seitenansicht; und

Abb. 9

eine schematische Darstellung des zusammengesetzten elektrischen Gas-Strömungsheizers in einer isometrischen Darstellung; und

Abb. 10

eine schematische Darstellung einer alternativen Ausführung des elektrischen Gas-Strömungsheizers in einer Explosionsdarstellung.

Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawings in the description of the figures , which are intended to explain the invention and are not to be viewed as limiting:
Show it:

Fig. 1

a schematic representation of a blank of the electrical heating element in cut or punched form;

Fig. 2

a schematic representation of the blank of the electric heating element 1 in meandering folded form in side view;

Fig. 3

a schematic representation of the in 2 shown meandering folded electrical heating element in isometric representation;

Fig. 4

a schematic representation of an alternative blank of the electric heating element in cut or stamped form, with additional webs being provided for handling during the manufacturing process;

Fig. 5

a schematic representation of the in 4 now shown in a meandering folded electric heating element in an isometric representation;

Fig. 6

a schematic representation of the cylindrical structure in a sectional side view;

Fig. 7

a schematic representation of a built-in electric heating element in a cylindrical structure in plan view;

Fig. 8

a schematic representation of a built-in electric heating element in a cylindrical structure in a sectional side view; and

Fig. 9

Figure 12 is a schematic representation of the composite electric gas flow heater in an isometric view; and

Fig. 10

a schematic representation of an alternative embodiment of the electric gas flow heater in an exploded view.

The following exemplary further explanations should not or do not necessarily have to be evaluated as restrictive, but rather represent special explanations and are intended to explain the invention disclosed here:

First, a blank of the electrical heating element is produced, for which purpose a structure is punched or cut from a sheet metal 1 to 0.7 millimeters thick, for example by means of a laser. The production step can, for example, be CNC-supported. This creates a flat meandering structure as a band made up of several segments that are circular in terms of their envelope, i.e. the individual heating grid structure levels, which are connected to one another by intermediate connections or webs (cf. Fig. 1 ). The meanders of the individual heating grid structure levels are punched or cut in such a way that the conductor cross-section in relation to the center of the circle is larger on the outside than the conductor cross-section of the internal heating conductors (cf. Fig. 7 ). Subsequent to the cutting out, the blank is deburred according to common methods (not shown). The blank is bent by 180° at the intermediate connections or webs, so that a cylinder package is formed from parallel meander sheets lying one on top of the other, the distance between which, for example approx. 3 mm, is maintained by the webs (cf. Fig. 2 and 3 ).

Alternatively, the individual heating grid structure levels can be cut individually and welded to one another. Accordingly, no band-shaped blank would be provided, but only individual circular sheet metal segments.

In order to facilitate production, webs for handling during the manufacturing process can be attached to the heating grid structure levels (cf. Fig. 4 and 5 opposite to Fig. 1 and 3 ) be provided, which are separated after bending or welding or before assembly (step c).

The finished electric heating element is then inserted into the cylindrical structure (cf. Fig. 6 ) introduced, whereby this can be done in particular by turning or screwing (cf. Fig. 7, 8 and 9 ). The cylindrical structure, which also serves as an insulator, is in Fig. 6 shown and provided with an internal thread.

Alternatively, the cylindrical structure can be formed from two half-shells which, when assembled, form the cylindrical structure (cf. Fig. 10 ).

In an alternative configuration, the cylindrical structure can have an arrangement of grooves on its inner wall to accommodate the two or more spaced meandering heating grid structure levels (cf. Fig. 10 ). This design allows for particularly simple assembly, namely by inserting or inserting the electrical heating element into a first of the half-shells and then assembling the second half-shell with the first.

With regard to further optimization options, the following is explained:
When manufacturing the blank of the electrical heating element, it is possible to design corresponding heating grid structure planes or areas thereof with different dimensions, so that thicker conductor cross sections in certain defined areas can give off different amounts of heat to the gas flowing past. In addition, the flow can also be influenced in a targeted manner by cutting out or punching out adjacent heating grid structure levels (and preselecting in the case of welding) in such a way that the openings of adjacent heating grid structure levels do not coincide with one another with respect to the direction of flow. The individual heating grid structure levels can also have diffuser elements that do not make contact between the individual conductors, but influence the flow of flow to increase turbulence (not shown).

This individual design can be designed differently from level to heating grid structure level, so that by specifically influencing the flow, a homogeneously heated gas is discharged from the gas flow heater at the end, which is then made available for further processing. The channel structure inside can be varied and causes a corresponding homogenization. In particular, this allows for great variability in the design of the channel and support structure that can be formed in this way. Channel structures can be designed in the interior, which can then definitely have a positive influence on the heating of the flowing gas. But it can complex inner channel structures can also be formed, for example to calm currents or to make them consciously turbulent. Such bottlenecks for the gas flow can be calculated using computer simulations and adjusted accordingly, since this depends on many factors such as the gas inlet area, gas outlet area, flow rate, etc.

The individual heating conductors of the meandering electrical heating elements can be arranged in different densities. In a special variant, an inhomogeneous distribution of heating conductors in one plane can also be implemented, which can counteract possible uneven gas heating, for example in the edge areas of the heater. For this purpose, the heater can be designed with the heating elements in accordance with the flow profiles.

Should the electric heating element have to be replaced over time as a result of material fatigue, it can be easily unscrewed from the cylindrical socket and a new electric heating element can be used. Gas heating can also be optimized in the same way, since the inventive solution allows rapid validation of simulated temperature distributions of the gas flow heater when using CNC-supported methods.

Possible applications can be seen in particular in the field of solid oxide cell technology or the steel industry, since high gas temperatures have to be reached in both application areas.

The exemplary embodiments mentioned above are intended to explain the invention, but not necessarily to limit its scope of protection.

Claims (10)

Electrical gas flow heater having at least one cylindrical structure in which at least one channel for gas conduction is formed and at least one electrical heating element is arranged in the channel of the cylindrical structure,
wherein heat can be transferred from the electric heating element to a gas flowing through the channel to heat the gas and/or to achieve high gas temperatures,
characterized in that - the electrical heating element has two or more spaced meandering heating grid structure planes perpendicular to the direction of flow of the channel, and - the two or more spaced, meandering heating grid structure levels are arranged one after the other in the channel in the direction of flow, the individual spaced, meandering heating grid structure levels being connected to one another in a meandering manner via an electrically conductive intermediate connection, and the first and the last of the spaced, meandering heating grid structure levels having an electrical connector , and - the cylindrical structure is designed on its inner wall to accommodate the two or more spaced meandering heating grid structure levels. Electrical gas flow heater according to claim 1,
characterized in that
the electric heating element is designed in one piece and/or in one piece and/or in one piece of material. Electric gas flow heater according to claim 1 or 2,
characterized in that
the cylindrical structure on the inside for accommodating the two or more spaced meandering heating grid structure levels - an internal thread, particularly preferably designed with a two-start internal thread, wherein the electrical heating element can be inserted into or removed from the cylindrical structure by a rotary movement of the electrical heating element in relation to the latter,
or - An arrangement of grooves is formed, the electric heating element being insertable or removable when the two-part half-shell formation of the cylindrical structure is open. Electric gas flow heater according to one of the preceding claims,
characterized in that
the spaced-apart individual meander-like heating grid structure levels connected to one another in a meander-like manner are arranged at equal distances in the direction of flow. Electric gas flow heater according to one of the preceding claims,
characterized in that
the electrical heating element has at least one of the features selected from the following features: - The individual spaced meandering heating grid structure levels have a circular envelope; - The individual spaced heating grid structure planes designed in a meandering manner are designed wider in their edge areas than in their inner areas; The conductor cross section of the interconnections is significantly larger than the conductor cross sections of the spaced, meandering heating grid structure levels. Electric gas flow heater according to one of the preceding claims,
characterized in that
the cylindrical structure is designed as an insulator. Electric gas flow heater according to one of the preceding claims,
characterized in that
the cylindrical structure is formed of technical ceramics and/or concrete and/or alumina. Electric gas flow heater according to one of the preceding claims,
characterized in that
the electrical heating element is designed without a support structure, so that the electrical heating element is mounted exclusively in the receptacle of the cylindrical structure. Electric gas flow heater according to one of the preceding claims,
characterized in that
the neighboring heating grid structure levels are shaped in such a way that their openings do not coincide with one another with respect to the direction of flow and/or the heating grid structure levels are provided with diffuser elements. Gas flow heater manufacturing method for manufacturing an electric gas flow heater according to one of the preceding claims, comprising at least the following steps: a) making the cylindrical structure; b1) Making the electrical heating element by bending using the following steps: producing a blank by stamping and/or lasering and/or cutting from sheet metal, meandering heating grid structure levels connected to one another via intermediate connections being formed; - Bending of the blank in each case in the area of the intermediate connections by 180° in each case, so that a cylindrical structure of plane-parallel meandering heating grid structure levels is formed, the distance between which is maintained by the intermediate connections; or b2) as an alternative to bending, manufacture the electric heating element by welding using the following steps: - Production of several heating grid structure levels designed in a meandering manner by punching and/or lasering and/or cutting from sheet metal, - meandering welding of the plurality of meandering heating grid structure levels using intermediate connections; c) Assemble the gas flow heater using the following steps: - screwing or inserting the electrical heating element into the cylindrical structure; and electrically contacting the electrical heating element.

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