EP2134143B1 - Electric resistance heat element for a heating device for heating a flowing gaseous medium - Google Patents

Electric resistance heat element for a heating device for heating a flowing gaseous medium Download PDF

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Publication number
EP2134143B1
EP2134143B1 EP08010426A EP08010426A EP2134143B1 EP 2134143 B1 EP2134143 B1 EP 2134143B1 EP 08010426 A EP08010426 A EP 08010426A EP 08010426 A EP08010426 A EP 08010426A EP 2134143 B1 EP2134143 B1 EP 2134143B1
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EP
European Patent Office
Prior art keywords
heating
heating element
heating resistor
resistance heating
flow
Prior art date
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Application number
EP08010426A
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German (de)
French (fr)
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EP2134143A1 (en
Inventor
Ulrich Gubler
Reto Zurbuchen
Michel Prestat
Ulrich Vogt
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Leister Process Technologies
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Leister Process Technologies
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Publication date
Application filed by Leister Process Technologies filed Critical Leister Process Technologies
Priority to EP08010426A priority Critical patent/EP2134143B1/en
Priority to AT08010426T priority patent/ATE492140T1/en
Priority to DE502008002030T priority patent/DE502008002030D1/en
Priority to JP2009125138A priority patent/JP4977844B2/en
Priority to US12/478,825 priority patent/US20090304372A1/en
Priority to CN2009102034001A priority patent/CN101603733B/en
Publication of EP2134143A1 publication Critical patent/EP2134143A1/en
Application granted granted Critical
Publication of EP2134143B1 publication Critical patent/EP2134143B1/en
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H3/00—Air heaters
    • F24H3/02—Air heaters with forced circulation
    • F24H3/04—Air heaters with forced circulation the air being in direct contact with the heating medium, e.g. electric heating element
    • F24H3/0405—Air heaters with forced circulation the air being in direct contact with the heating medium, e.g. electric heating element using electric energy supply, e.g. the heating medium being a resistive element; Heating by direct contact, i.e. with resistive elements, electrodes and fins being bonded together without additional element in-between
    • F24H3/0423—Air heaters with forced circulation the air being in direct contact with the heating medium, e.g. electric heating element using electric energy supply, e.g. the heating medium being a resistive element; Heating by direct contact, i.e. with resistive elements, electrodes and fins being bonded together without additional element in-between hand-held air guns
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H3/00—Air heaters
    • F24H3/02—Air heaters with forced circulation
    • F24H3/04—Air heaters with forced circulation the air being in direct contact with the heating medium, e.g. electric heating element
    • F24H3/0405—Air heaters with forced circulation the air being in direct contact with the heating medium, e.g. electric heating element using electric energy supply, e.g. the heating medium being a resistive element; Heating by direct contact, i.e. with resistive elements, electrodes and fins being bonded together without additional element in-between
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/10—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
    • H05B3/12—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material
    • H05B3/14—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material the material being non-metallic
    • H05B3/141—Conductive ceramics, e.g. metal oxides, metal carbides, barium titanate, ferrites, zirconia, vitrous compounds
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/10—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
    • H05B3/16—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor the conductor being mounted on an insulating base
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/40—Heating elements having the shape of rods or tubes
    • H05B3/42—Heating elements having the shape of rods or tubes non-flexible
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/018—Heaters using heating elements comprising mosi2
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/02—Heaters using heating elements having a positive temperature coefficient

Definitions

  • the invention relates to an electrical resistance heating element for a heating device for heating a gaseous medium, comprising at least one extending substantially in the longitudinal direction of the electrical resistance heating element heating resistor, where the medium flows past and is heated.
  • the resistance heating element has at least one flow channel extending along the heating resistor, through which the gaseous medium can pass from a channel inlet side to a channel outlet side of the resistance heating element, wherein the heating resistor has an electrically conductive ceramic material for the power line.
  • the invention also relates to a heating device for a flowing gaseous medium, which is equipped with such an electrical resistance heating element.
  • heating devices are understood in particular to be heating devices, modules or systems in which the electrical resistance heating element is arranged in a heating tube. At one end, for example, air or gas is injected and at the other end exits the heated air or gas stream.
  • air flow generated by a fan provided on the heater or the heater of be supplied to an external air flow generator or emanate the gas stream from a preferably under pressure gas reservoir.
  • Such heaters are well known and find extensive applications in industry and craft.
  • a cold stream of the gaseous medium is introduced to the resistance heating element in these devices and then passed through the energized heating element and / or along this, the cold medium by contact with the hot heating resistance increasingly from the inlet side is heated to the exit side of the heating resistor.
  • the flowing gaseous medium passes through the heating element in one or more flow channels, which enclose the at least one heating resistor.
  • a heater in the form of a hot air device in which the resistance heating element is located in a heating tube.
  • the heating element has a support made of a high-temperature-resistant ceramic material, which is held via a central pin on a side facing the fan side connecting head.
  • the electrical connection of the heating resistor which is formed by helically extending heating wires in a central air duct, also takes place via this connection head.
  • On the air outlet side of the heating element is still a thin final ceramic plate, which is also held by the central pin. Both the connection head and the end plate have openings for the air flow, so that it can pass unhindered the air duct with the heating resistor.
  • the heating wire usually burns through.
  • the heating element is thus unusable.
  • the too low air flow can be caused for example by failure of the blower or by narrowing the air inlet or air outlet cross section of the hot air device.
  • special electrical protection measures are required to protect the heating wire from unwanted overheating.
  • the heating air devices available on the market usually have a thermal sensor or switch, which throttles or interrupts the power supply to the heating resistor in case of overheating.
  • the DE 10 12 675 A1 discloses a PCT ceramic flow rate electrical resistance heating element which is particularly suitable for heating fluid flow at small cross-sections and low throughput.
  • the heating element has an elongated profile body in the flow direction, which has a substantially constant cross-sectional area and electrode layers in the longitudinal direction, through which the heating current is passed through the walls of the profile body substantially perpendicular to the flow direction of the flowing liquid.
  • the walls have consistently a substantially the same, the current path corresponding thickness and provided with electrode layers heating ribs which protrude into the flow channel.
  • the US Pat. No. 6,442,341 B1 also teaches a water heater for liquids.
  • the water heater described therein has a resistance heating element which is embedded in a metallic housing.
  • a flow passage for the liquid extends at a distance parallel to the one heating element.
  • the resistance heating element itself has no integrated flow channels and is integrally connected to the housing over its entire surface. The heat transfer from the heating element to the flowing liquid takes place indirectly over a portion of the housing in which extends the tubular flow channel, wherein the housing is made of a highly thermally conductive metal.
  • the EP 0 899 985 A1 deals with a water heater for heating liquid in a closed circuit of a motor vehicle.
  • the instantaneous water heater comprises at least one heating element with at least one channel, through which the liquid to be heated flows, and with at least one PCT heating element for heating the closely adjacent heating element.
  • the structure and operation corresponds essentially to that of US Pat. No. 6,442,341 B1 known water heater. It differs from this by several flow channels and several provided heating elements.
  • the following invention has for its object to propose an improved electrical resistance heating element for a heater for a gaseous flowing medium, in which the risk of overheating is reduced even without special protective measures.
  • the heating resistor of the electrical resistance heating element is rod-shaped, wherein the heating resistor is held by arranged on the channel inlet side and the channel outlet side of the resistance heating element support plates in which the flow channel continues.
  • the heating resistor is positively engaged with the carrier plates at its ends.
  • a massive heating resistor whose longitudinal extent is formed significantly larger than the transverse extent.
  • the cross-sectional shape is arbitrary and can vary over the longitudinal extent.
  • the heating resistor can also be two or more parallel to each other in the longitudinal direction Have sections that are connected to each other so that they form a current path.
  • the heating resistor has an electrically conductive ceramic material for the power line.
  • the conductive ceramic material alone may form the ceramic heating resistor or be provided as a sheath of a ceramic rod made of an electrically non-conductive ceramic material.
  • Such a heating resistor has a high mechanical and electrical wear and overheating resistance, allowing a long service life.
  • the ceramic materials used also have excellent properties in terms of thermal and electrical conductivity.
  • the current flow through the heating resistor can be influenced by the conductivity of the ceramic as well as by the geometry of the ceramic heating element become.
  • the conductivity of the ceramic is adjustable by changing its conductive and non-conductive substance shares in a wide range. Another advantage is that over known heating elements higher temperatures and faster temperature changes are possible.
  • the electrical heating element according to the invention is provided for example for an air heater, which operates with the usual voltages of 48V, as they occur in ships or aircraft, or of 110 V, 230 V or 380 V, as it provides the power grid of network operators can be.
  • the electrical resistance of the ceramic rod-shaped heating resistor must be sufficiently large. This can be achieved on the one hand with a high resistivity of the electrically conductive ceramic material and / or on the other hand by the geometric design of the ceramic heating resistor.
  • the electrical resistance heating element in which the conductive ceramic material has a resistivity between 0.01 and 1.0 ⁇ ⁇ cm and / or the ratio of the length to the cross-sectional area of the ceramic material of the heating resistor is between 1 and 500 cm -1 ,
  • the rod-shaped heating resistor is advantageously formed U-shaped. This doubles the length of the ceramic heater rod and thus its electrical resistance.
  • a plurality of, preferably U-shaped heating resistors may be provided. These can vary depending on the Voltage supply level and the desired power to be electrically connected in series or in parallel.
  • a metal layer For electrical contacting of the rod-shaped heating resistors whose end are expediently provided with a metal layer. This can be used up, for example, by steaming or sputtering. Preferably, a metal paste is used, which typically contains silver and possibly another precious metal, such as. As platinum or palladium.
  • the support plates holding the heating resistor are each formed from a non-electrically conductive ceramic material.
  • the support plates have similar to the electrical conductivity similar specific characteristics as the ceramic heating element.
  • the support plates preferably have recesses adapted to the cross-sectional shape of the heating resistor for receiving the ends of the heating resistor, as well as openings through which the flow of the gaseous medium can pass.
  • the resistance heating element according to the invention comprises a plurality of ceramic heating rods, which are arranged concentrically around the center of the heating element.
  • Each U-shaped heating resistor is positively held with its front and rear end portions in the recesses of the support plates, wherein the support plates are fixed by a common central axially extending pin together.
  • the heating resistors are electrically connected to each other and to the power supply lines.
  • the flow of the medium can pass through the flow channel, which extends between the two support plates and in which the at least one heating resistor is arranged, through the openings of the two support plates.
  • the heating resistor is connected in a material-locking manner to the carrier plates.
  • the heating resistors In order to hold the elongated heating resistors with the carrier plates in position, they can be firmly connected before, by or after sintering.
  • the heating elements thus produced are self-supporting and need not be guided or supported by an additional element.
  • the support plates, which hold the ceramic heating resistors on both sides, must withstand temperatures well above 1000 ° C, for example on the air outlet side of the resistance heating element.
  • the U-shaped ceramic heating resistor may have a planar or a structured surface.
  • An embodiment of the invention is preferred in which the heating resistor has depressions and / or elevations in order to increase the surface area for contact with the flow of the gaseous medium in relation to a planar surface. Due to the more complex geometry, in addition to the largest possible surface for the heat exchange with the flowing medium, it is also achieved that the medium flowing past the heating resistor in the flow channel is swirled. This causes the entire media flow is uniformly and homogeneously heated.
  • the conductive ceramic material of the heating resistor is a mixed ceramic having a conductive and a non-conductive component, the conductive ceramic component having a positive temperature coefficient of between 0 and 10000 ppm / K.
  • a conductive ceramic component is preferably molybdenum disilicide (MoSi 2 ) and as a non-conductive ceramic component preferably alumina (Al 2 O 3 ) is provided.
  • the preferably positive temperature coefficient should not rise too steep, otherwise hot spots may form. Also within the service temperature up to about 1500 ° C no steep slope of the resistivity should occur, as with some electrically conductive ceramics with positive Temperature coefficient is the case.
  • the mixed ceramic may also have other additives for improving sinterability or stability. It is also possible, the alumina by other insulating ceramics such. As oxide or nitride or silicate ceramics partially substitute.
  • the proportion of the conductive component the specific resistance of the material can be adjusted within a certain range. A proportion of 20 to 30% molybdenum disilicide in the mixed ceramic has proven to be ideal. Thus, specific resistances between 0.01 and 1.0 ⁇ ⁇ cm can be achieved at room temperature, which increase up to 1000 ° C by a factor of three or more.
  • the heating device according to the invention for example for a hot air device, with a arranged in a stream of gaseous medium resistance heating element, which is encompassed by a heating tube, has an inventive electrical resistance heating element with the features of claim 1.
  • a heating tube for example, air or gas is blown in as a medium, and at the other end of the heating tube, the heated air or gas stream exits.
  • the air or gas stream generated by a fan provided on the heater or the heater can be supplied from an external reservoir under pressure.
  • FIG. 1 shows an embodiment of the resistance heating element 1 according to the invention with four heating resistors 2 in an Achsmaledarwolf, of which only two are visible in the drawing.
  • the heating resistors 2 are formed substantially rod-shaped and have front and rear end portions 3, 4.
  • the rear end sections 4 are associated with an air inlet side 5 and the front end sections of an air outlet side 6 of the resistance heating element 1.
  • the heating resistors 2 are U-shaped with a flat surface 7 and have ends 8, 8 ', legs 9, 9' and a leg 9, 9 'connecting base 10.
  • the ends 8 'of the heating resistors 2 are electrically connected by means of an electrical bridge 11. To the ends 8 of the heating resistors 2 lead electrical leads 12th
  • the heating resistors 2 are held by a front and rear support plate 13, 14.
  • the base 10 is in positive engagement with the air outlet side front support plate 13, the two opposite ends 8, 8 'with the air inlet side rear support plate 14.
  • the support plates 13, 14 are fixed to each other with a central, preferably four-edged pin 15.
  • the heating resistors 2 extend into an air duct 16 which is delimited on the front side by the carrier plates 13, 14 and peripherally by a heating tube, not shown in the drawing, as soon as the heating element 1 is installed in a hot air device.
  • FIGS. 1, 2 seen, an elongated substantially cylindrical shape.
  • FIG. 2 shows the designed as a round flat disc support plates 13, 14, which are made of an electrically non-conductive ceramic material, in plan view. Shown is the heating resistors 2 associated inside.
  • the support plates 13, 14 have recesses 17 with holes 18 for receiving the front and rear end portions 3, 4 of the heating resistors 2.
  • a central attachment hole 20 for the carrier plates 13, 14 connecting pin 15 is formed.
  • the holes 18 of the recesses 17 allow the electrical connection of the heating resistors. 2
  • FIG. 3 shows a first embodiment of the U-shaped heating resistor 2 made of an electrically conductive ceramic material.
  • the legs 9, 9 'and the base 10 have a square cross-sectional shape and lie in one plane.
  • the surface 7 is flat.
  • FIG. 4 is a second variant of the in the FIG. 3 shown heating resistor 2 shown in the legs 9, a rectangular and the legs 9 'and the base 10 have a triangular cross-sectional shape, so that together they form a cylinder segment corresponding to one-eighth of a right circular cylinder.
  • the surfaces 7 of the legs 9, 9 ' are flat and inclined to each other.
  • FIG. 5 shows a third embodiment of the U-shaped heating resistor 2.
  • the legs 9, 9 'and the base 10 have a substantially triangular cross-sectional shape. They are designed so that together they form a cylinder segment which corresponds to a quarter of a circular cylinder.
  • the surface 7 of the legs 9, 9 ' is structured. It has recesses 21 and ridges 22 to increase the surface 7 for contact with the air flow.
  • the structured surface 7 advantageously causes a turbulence of the air flow and thus a uniform heating.
  • FIG. 6 shows the to the in the FIG. 5
  • the carrier plates 13, 14 have a circumferential, substantially square recess 17 and are suitable for cohesive connection with the heating resistors 2.
  • the heating resistors 2 are arranged in the corners 23 of the recess 17.
  • the support plates 13, 14 have openings 19 for the air flow and the formed recess 17 holes 18 for the electrical connection of the heating resistors 2.
  • heating element 2 matching support plates 13, 14 are not shown in the drawing. They can be similar to those in the FIG. 6 be formed support plates 13, 14, wherein the shape of the recess 17 is adapted to the different cross-sectional shape of the cylinder segment of the heating resistor 2.
  • FIGS. 7, 8 show two embodiments of H contemplattuft listeningen invention 24, 25.
  • hot air device 24 is a flanged on a machine frame hot tufting device without integrated fan. The air flow is supplied to the hot air device 24 from the outside.
  • the in the FIG. 8 shown hot air device 25 is equipped with an internal fan and can be used as a hand-held hot air device. Otherwise, the two devices are formed substantially the same. They have a housing 26 with a front heating tube 27. In the heating tube 27 is the invention Resistance heating element 1 is not visible installed in the drawing. In this case, the air outlet side 6 of the resistance heating element 1 to the air outlet opening 28 of the heating tube 27 and the air inlet side 5 to the rear end of the housing 26. About the housing 26, the heating resistors 2 of the resistance heating element 1 are supplied with electrical voltage.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Resistance Heating (AREA)
  • Direct Air Heating By Heater Or Combustion Gas (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)

Abstract

The element (1) has a heating resistor (2) extending in a longitudinal direction, and a flow canal extending along the heating resistor. The heating resistor has an electrically conductive ceramic material for conducting current, where the heating resistor is rod-shaped and held by carrier plates (13, 14) that are located at a canal inlet side and a canal outlet side of the resistance heating element. The flow canal continues in the carrier plates, where the heating resistor positively engages the carrier plates at ends (8, 8'). An independent claim is also included for a heating device for heating a flowing gaseous medium comprising a heating tube.

Description

Die Erfindung betrifft ein elektrisches Widerstandsheizelement für eine Heizeinrichtung zum Erhitzen eines gasförmigen Mediums, mit mindestens einem sich im wesentlichen in Längsrichtung des elektrischen Widerstandheizelements erstreckenden Heizwiderstand, an dem das Medium vorbeiströmt und dabei erhitzt wird. Das Widerstandsheizelement weist mindestens einen sich entlang dem Heizwiderstand erstreckenden Strömungskanal auf, durch den das gasförmige Medium von einer Kanaleintrittsseite zu einer Kanalaustrittsseite des Widerstandsheizelementes gelangen kann, wobei der Heizwiderstand ein elektrisch leitfähiges Keramikmaterial zur Stromleitung aufweist. Die Erfindung betrifft außerdem eine Heizeinrichtung für ein strömendes gasförmiges Medium, die mit einem solchen elektrischen Widerstandsheizelement ausgestattet ist.The invention relates to an electrical resistance heating element for a heating device for heating a gaseous medium, comprising at least one extending substantially in the longitudinal direction of the electrical resistance heating element heating resistor, where the medium flows past and is heated. The resistance heating element has at least one flow channel extending along the heating resistor, through which the gaseous medium can pass from a channel inlet side to a channel outlet side of the resistance heating element, wherein the heating resistor has an electrically conductive ceramic material for the power line. The invention also relates to a heating device for a flowing gaseous medium, which is equipped with such an electrical resistance heating element.

Unter Heizeinrichtungen werden in diesem Zusammenhang insbesondere Heizgeräte, -module oder -systeme verstanden, bei dem das elektrische Widerstandsheizelement in einem Heizrohr angeordnet ist. An dessen einem Ende wird beispielsweise Luft oder Gas eingeblasen und an dem anderen Ende tritt der erhitzte Luft- oder Gasstrom aus. Dabei kann der Luftstrom von einem an der Heizeinrichtung vorgesehenen Gebläse erzeugt oder der Heizeinrichtung von einem externen Luftstromerzeuger zugeführt werden bzw. der Gasstrom von einem vorzugsweise unter Überdruck stehenden Gasreservoir ausgehen.In this context, heating devices are understood in particular to be heating devices, modules or systems in which the electrical resistance heating element is arranged in a heating tube. At one end, for example, air or gas is injected and at the other end exits the heated air or gas stream. In this case, the air flow generated by a fan provided on the heater or the heater of be supplied to an external air flow generator or emanate the gas stream from a preferably under pressure gas reservoir.

Derartige Heizeinrichtungen sind allgemein bekannt und finden umfangreiche Anwendungen in Industrie und Handwerk. Zur Erzeugung eines heißen Luft- oder Gasstromes wird bei diesen Einrichtungen ein kalter Strom des gasförmigen Mediums an das Widerstandsheizelement herangeführt und anschließend durch das bestromte Heizelement und/oder an diesem entlang geführt, wobei das kalte Medium durch Kontakt mit dem heißen Heizwiderstand zunehmend von der Eintrittsseite zu der Austrittsseite des Heizwiderstandes erhitzt wird. Das strömende gasförmige Medium passiert dabei das Heizelement in einem oder mehreren Strömungskanälen, die den mindestens einen Heizwiderstand umschließen.Such heaters are well known and find extensive applications in industry and craft. To produce a hot air or gas stream, a cold stream of the gaseous medium is introduced to the resistance heating element in these devices and then passed through the energized heating element and / or along this, the cold medium by contact with the hot heating resistance increasingly from the inlet side is heated to the exit side of the heating resistor. The flowing gaseous medium passes through the heating element in one or more flow channels, which enclose the at least one heating resistor.

Aus der DE 198 39 044 A1 ist eine derartige Heizeinrichtung in Form einer Heißlufteinrichtung bekannt, bei der sich das Widerstandsheizelement in einem Heizrohr befindet. An der der Luftaustrittsseite des Heizelementes zugeordneten Seite des Heizrohres können üblicherweise verschiedene Düsen angeschlossen werden. Das Heizelement weist einen Träger aus einem hochtemperaturbeständigen Keramikmaterial auf, der über einen zentralen Stift an einem dem Gebläse zugewandten Seite angeordneten Anschlusskopf gehalten ist. Über diesen Anschlusskopf erfolgt auch der elektrische Anschluss des Heizwiderstandes, der von sich spiralförmig in einem zentralen Luftkanal erstreckenden Heizdrähten gebildet ist. Auf der Luftaustrittsseite des Heizelementes befindet sich noch eine dünne Abschlusskeramikplatte, die ebenfalls von dem zentralen Stift gehalten ist. Sowohl der Anschlusskopf wie auch die Abschlussplatte weisen Durchtrittsöffnungen für den Luftstrom auf, so dass dieser ungehindert den Luftkanal mit dem Heizwiderstand passieren kann.From the DE 198 39 044 A1 is such a heater in the form of a hot air device is known in which the resistance heating element is located in a heating tube. At the air outlet side of the heating element associated side of the heating tube usually different nozzles can be connected. The heating element has a support made of a high-temperature-resistant ceramic material, which is held via a central pin on a side facing the fan side connecting head. The electrical connection of the heating resistor, which is formed by helically extending heating wires in a central air duct, also takes place via this connection head. On the air outlet side of the heating element is still a thin final ceramic plate, which is also held by the central pin. Both the connection head and the end plate have openings for the air flow, so that it can pass unhindered the air duct with the heating resistor.

Werden die dabei verwendeten Widerstandsheizelemente eine gewisse Zeit ohne ausreichenden Luftstrom betrieben, so brennt in der Regel der Heizdraht durch. Das Heizelement ist damit unbrauchbar. Der zu geringe Luftstrom kann beispielsweise durch Ausfall des Gebläses oder durch Verengung des Lufteintritts- oder Luftaustrittsquerschnittes der Heißlufteinrichtung verursacht werden. Aus diesem Grund sind zum Schutz des Heizdrahtes vor unerwünschter Überhitzung besondere elektrische Schutzmaßnahmen erforderlich. Dazu weisen die auf dem Markt erhältlichen Heizlufteinrichtungen üblicherweise einen Thermosensor oder -schalter auf, der die Stromzufuhr zu dem Heizwiderstand bei Überhitzungsgefahr drosselt oder unterbricht.If the resistance heating elements used in this case are operated for a certain time without sufficient air flow, the heating wire usually burns through. The heating element is thus unusable. The too low air flow can be caused for example by failure of the blower or by narrowing the air inlet or air outlet cross section of the hot air device. Out For this reason, special electrical protection measures are required to protect the heating wire from unwanted overheating. For this purpose, the heating air devices available on the market usually have a thermal sensor or switch, which throttles or interrupts the power supply to the heating resistor in case of overheating.

Zum Stand der Technik wird weiterhin auf die Druckschriften DE 10 12 675 A1 , US 6,442,342 B1 und EP 0 899 985 verwiesen.The prior art will continue to the documents DE 10 12 675 A1 . US Pat. No. 6,442,342 B1 and EP 0 899 985 directed.

Die DE 10 12 675 A1 offenbart ein elektrisches Durchfluss-Widerstandsheizelement aus PCT-Keramik, welches besonders zum Erwärmen durchströmender Flüssigkeiten bei kleinem Querschnitt und kleinem Durchsatz geeignet ist. Das Heizelement weist einen in Durchflussrichtung länglichen Profilkörper auf, der in Längsrichtung eine im wesentlichen konstante Querschnittsfläche und Elektrodenschichten aufweist, durch welche der Heizstrom im wesentlichen senkrecht zur Durchflussrichtung der strömenden Flüssigkeit durch die Wände des Profilkörpers geleitet wird. Dabei haben die Wände durchweg eine im wesentliche gleiche, dem Stromweg entsprechende Dicke und mit Elektrodenschichten versehene Heizrippen, die in den Durchflusskanal hinein ragen.The DE 10 12 675 A1 discloses a PCT ceramic flow rate electrical resistance heating element which is particularly suitable for heating fluid flow at small cross-sections and low throughput. The heating element has an elongated profile body in the flow direction, which has a substantially constant cross-sectional area and electrode layers in the longitudinal direction, through which the heating current is passed through the walls of the profile body substantially perpendicular to the flow direction of the flowing liquid. The walls have consistently a substantially the same, the current path corresponding thickness and provided with electrode layers heating ribs which protrude into the flow channel.

Die US 6,442,341 B1 lehrt ebenfalls einen Durchlauferhitzer für Flüssigkeiten. Der dort beschriebene Durchlauferhitzer weist ein Widerstandsheizelement auf, das in ein metallisches Gehäuse eingebettet ist. In dem Gehäuse erstreckt sich ein Durchflusskanal für die Flüssigkeit mit Abstand parallel zu dem einen Heizelement. Das Widerstandsheizelement weist selbst keine integrierten Strömungskanäle auf und ist über seine gesamte Oberfläche stoffschlüssig mit dem Gehäuse verbunden. Die Wärmeübertragung von dem Heizelement zu der strömenden Flüssigkeit erfolgt indirekt über einen Abschnitt des Gehäuses, in dem sich der rohrförmige Durchflusskanal erstreckt, wobei das Gehäuse aus einem gut wärmeleitenden Metall hergestellt ist.The US Pat. No. 6,442,341 B1 also teaches a water heater for liquids. The water heater described therein has a resistance heating element which is embedded in a metallic housing. In the housing, a flow passage for the liquid extends at a distance parallel to the one heating element. The resistance heating element itself has no integrated flow channels and is integrally connected to the housing over its entire surface. The heat transfer from the heating element to the flowing liquid takes place indirectly over a portion of the housing in which extends the tubular flow channel, wherein the housing is made of a highly thermally conductive metal.

Die EP 0 899 985 A1 behandelt einen Durchlauferhitzer zum Erwärmen von Flüssigkeit in einem geschlossenen Kreislauf eines Kraftfahrzeugs. Der Durchlauferhitzer umfasst wenigstens einen Heizkörper mit wenigstens einem Kanal, der von der zu erwärmenden Flüssigkeit durchflossen wird, und mit wenigstens einem PCT-Heizelement zum Erwärmen des eng benachbart angeordneten Heizkörpers. Der Aufbau und die Funktionsweise entspricht im wesentlichen dem aus der US 6,442,341 B1 bekannten Durchlauferhitzer. Er unterscheidet sich von diesem durch mehrere Strömungskanäle und mehrere vorgesehene Heizelemente.The EP 0 899 985 A1 deals with a water heater for heating liquid in a closed circuit of a motor vehicle. The instantaneous water heater comprises at least one heating element with at least one channel, through which the liquid to be heated flows, and with at least one PCT heating element for heating the closely adjacent heating element. The structure and operation corresponds essentially to that of US Pat. No. 6,442,341 B1 known water heater. It differs from this by several flow channels and several provided heating elements.

Der folgenden Erfindung liegt die Aufgabe zugrunde, ein verbessertes elektrisches Widerstandsheizelement für eine Heizeinrichtung für ein gasförmiges strömendes Medium vorzuschlagen, bei dem die Gefahr der Überhitzung auch ohne besondere Schutzmaßnahmen reduziert ist.The following invention has for its object to propose an improved electrical resistance heating element for a heater for a gaseous flowing medium, in which the risk of overheating is reduced even without special protective measures.

Diese Aufgabe wird erfindungsgemäß durch ein elektrisches Widerstandsheizelement mit den Merkmalen des Anspruchs 1 sowie eine Heizeinrichtung für ein strömendes gasförmiges Medium gemäß Anspruch 10 gelöst. Weitere vorteilhafte Ausgestaltungen sind den Unteransprüchen zu entnehmen.This object is achieved by an electrical resistance heating element with the features of claim 1 and a heating device for a flowing gaseous medium according to claim 10. Further advantageous embodiments can be found in the dependent claims.

Gemäß der Erfindung ist der Heizwiderstand des elektrischen Widerstandsheizelementes stabförmig ausgebildet, wobei der Heizwiderstand von an der Kanaleintrittsseite und der Kanalaustrittsseite des Widerstandsheizelementes angeordneten Trägerplatten gehalten ist, in denen sich der Strömungskanal fortsetzt. Der Heizwiderstand ist mit den Trägerplatten an seinen Enden formschlüssig in Eingriff.According to the invention, the heating resistor of the electrical resistance heating element is rod-shaped, wherein the heating resistor is held by arranged on the channel inlet side and the channel outlet side of the resistance heating element support plates in which the flow channel continues. The heating resistor is positively engaged with the carrier plates at its ends.

Unter stabförmiger Heizwiderstand wird in diesem Zusammenhang ein massiver Heizwiderstand verstanden, dessen Längserstreckung gegenüber der Quererstreckung deutlich größer ausgebildet ist. Dabei ist die Querschnittsform beliebig und kann auch über die Längserstreckung variieren. Der Heizwiderstand kann in Längsrichtung auch zwei oder mehr parallel zueinander verlaufende Abschnitte aufweisen, die derart miteinander verbunden sind, dass sie einen Strompfad bilden.Under rod-shaped heating resistor is understood in this context, a massive heating resistor whose longitudinal extent is formed significantly larger than the transverse extent. The cross-sectional shape is arbitrary and can vary over the longitudinal extent. The heating resistor can also be two or more parallel to each other in the longitudinal direction Have sections that are connected to each other so that they form a current path.

Der Heizwiderstand weist ein elektrisch leitfähiges Keramikmaterial zur Stromleitung auf. Dabei kann das leitfähige Keramikmaterial allein den keramischen Heizwiderstand bilden oder als Ummantelung eines Keramikstabes aus einem elektrisch nicht leitfähigen Keramikmaterial vorgesehen sein. Ein solcher Heizwiderstand hat eine hohe mechanische sowie elektrische Verschleiß- und Überhitzungsfestigkeit, was eine lange Nutzungsdauer ermöglicht. Die verwendeten Keramikmaterialien weisen außerdem exzellente Eigenschaften bezüglich der Wärme- und der elektrischen Leitfähigkeit auf. Dabei kann der Stromfluss durch den Heizwiderstand durch die Leitfähigkeit der Keramik sowie durch die Geometrie des keramischen Heizstabes beeinflusst werden. Die Leitfähigkeit der Keramik ist durch Änderung ihrer leit- und nichtleitfähigen Stoffanteile in einem weiten Bereich einstellbar. Weiterer Vorteil ist, dass gegenüber bekannten Heizelementen höhere Temperaturen und schnellere Temperaturänderungen möglich sind.The heating resistor has an electrically conductive ceramic material for the power line. In this case, the conductive ceramic material alone may form the ceramic heating resistor or be provided as a sheath of a ceramic rod made of an electrically non-conductive ceramic material. Such a heating resistor has a high mechanical and electrical wear and overheating resistance, allowing a long service life. The ceramic materials used also have excellent properties in terms of thermal and electrical conductivity. The current flow through the heating resistor can be influenced by the conductivity of the ceramic as well as by the geometry of the ceramic heating element become. The conductivity of the ceramic is adjustable by changing its conductive and non-conductive substance shares in a wide range. Another advantage is that over known heating elements higher temperatures and faster temperature changes are possible.

Das erfindungsgemäße elektrische Heizelement ist beispielsweise für einen Lufterhitzer vorgesehen, der mit den üblichen Spannungen von 48V, wie sie in Schiffen oder Flugzeugen vorkommen, bzw. von 110 V, 230 V oder 380 V, wie sie das Stromnetz von Netzbetreibern zur Verfügung stellt, betrieben werden kann. Dazu muss der elektrische Widerstand des keramischen stabförmigen Heizwiderstandes genügend groß sein. Dies kann einerseits mit einem hohen spezifischen Widerstand des elektrisch leitenden Keramikmaterials und/oder andererseits durch das geometrische Design des keramischen Heizwiderstandes erreicht werden.The electrical heating element according to the invention is provided for example for an air heater, which operates with the usual voltages of 48V, as they occur in ships or aircraft, or of 110 V, 230 V or 380 V, as it provides the power grid of network operators can be. For this purpose, the electrical resistance of the ceramic rod-shaped heating resistor must be sufficiently large. This can be achieved on the one hand with a high resistivity of the electrically conductive ceramic material and / or on the other hand by the geometric design of the ceramic heating resistor.

Bevorzugt wird eine Ausführungsform des elektrischen Widerstandsheizelementes, bei der das leitfähige Keramikmaterial einen spezifischen Widerstand zwischen 0,01 und 1,0 Ω·cm aufweist und/oder das Verhältnis der Länge zu der Querschnittsfläche des Keramikmaterials des Heizwiderstandes zwischen 1 und 500 cm -1 beträgt.Preferred is an embodiment of the electrical resistance heating element in which the conductive ceramic material has a resistivity between 0.01 and 1.0 Ω · cm and / or the ratio of the length to the cross-sectional area of the ceramic material of the heating resistor is between 1 and 500 cm -1 ,

Wegen der erreichbaren spezifischen Widerstandswerte und der Betriebsspannungen müssen längliche Heizelemente für das erfindungsgemäße Widerstandsheizelement vorgesehen werden. Um eine aufwändige elektrische Verbindungstechnik auf der im Betrieb heißeren Seite des Heizwiderstandes, also an der Kanalaustrittsseite des elektrischen Widerstandsheizelementes zu vermeiden, ist der stabförmige Heizwiderstand vorteilhafterweise U-förmig ausgebildet. Dies verdoppelt die Länge des keramischen Heizstabes und somit dessen elektrischer Widerstandswert. Zur weiteren Erhöhung des elektrischen Widerstandes des Widerstandsheizelementes und zur Vergrößerung der Kontaktfläche zu dem strömenden gasförmigen Medium können mehrere, vorzugsweise U-förmige Heizwiderstände vorgesehen sein. Diese können abhängig von der Spannungsversorgungshöhe und der gewünschten Leistung elektrisch seriell oder parallel zusammengeschaltet sein.Because of the achievable resistivity values and the operating voltages, elongated heating elements must be provided for the resistance heating element according to the invention. In order to avoid a complex electrical connection technology on the hotter in operation side of the heating resistor, ie at the channel exit side of the electrical resistance heating, the rod-shaped heating resistor is advantageously formed U-shaped. This doubles the length of the ceramic heater rod and thus its electrical resistance. To further increase the electrical resistance of the resistance heating element and to increase the contact surface with the flowing gaseous medium, a plurality of, preferably U-shaped heating resistors may be provided. These can vary depending on the Voltage supply level and the desired power to be electrically connected in series or in parallel.

Zur elektrischen Kontaktierung der stabförmigen Heizwiderstände werden deren Ende zweckmäßigerweise mit einer Metallschicht versehen. Diese kann beispielsweise durch Bedampfen oder Sputtern aufgebraucht werden. Bevorzugt wird eine Metallpaste verwendet, die typischerweise Silber enthält und eventuell noch ein weiteres Edelmetall, wie z. B. Platin oder Palladium.For electrical contacting of the rod-shaped heating resistors whose end are expediently provided with a metal layer. This can be used up, for example, by steaming or sputtering. Preferably, a metal paste is used, which typically contains silver and possibly another precious metal, such as. As platinum or palladium.

Bei einer bevorzugten Ausführungsform der Erfindung sind die den Heizwiderstand haltenden Trägerplatten jeweils aus einem nicht elektrisch leitfähigen Keramikmaterial geformt. Die Trägerplatten weisen bis auf die elektrische Leitfähigkeit ähnliche spezifische Stoffmerkmale auf wie der keramische Heizstab.In a preferred embodiment of the invention, the support plates holding the heating resistor are each formed from a non-electrically conductive ceramic material. The support plates have similar to the electrical conductivity similar specific characteristics as the ceramic heating element.

Außerdem weisen die Trägerplatten vorzugsweise an die Querschnittsform des Heizwiderstandes angepasste Ausnehmungen zur Aufnahme der Enden des Heizwiderstandes auf, sowie Durchbrüche, durch die der Strom des gasförmigen Mediums hindurchtreten kann.In addition, the support plates preferably have recesses adapted to the cross-sectional shape of the heating resistor for receiving the ends of the heating resistor, as well as openings through which the flow of the gaseous medium can pass.

Vorzugsweise weist das erfindungsgemäße Widerstandsheizelement mehrere keramische Heizstäbe auf, die konzentrisch um das Zentrum des Heizelementes angeordnet sind. Dabei ist jeder U-förmige Heizwiderstand mit seinen vorderen und hinteren Endabschnitten in den Ausnehmungen der Trägerplatten formschlüssig gehalten, wobei die Trägerplatten durch einen gemeinsamen zentralen sich axial erstreckenden Stift aneinander festgelegt sind. Durch die Ausnehmungen der kanaleintrittsseitigen Trägerplatte sind die Heizwiderstände miteinander und mit den Stromzuleitungen elektrisch verbunden. Des weiteren kann der Strom des Mediums den Strömungskanal, der sich zwischen den beiden Trägerplatten erstreckt und in dem der mindestens eine Heizwiderstand angeordnet ist, durch die Durchbrüche der beiden Trägerplatten passieren.Preferably, the resistance heating element according to the invention comprises a plurality of ceramic heating rods, which are arranged concentrically around the center of the heating element. Each U-shaped heating resistor is positively held with its front and rear end portions in the recesses of the support plates, wherein the support plates are fixed by a common central axially extending pin together. Through the recesses of the channel entry side carrier plate, the heating resistors are electrically connected to each other and to the power supply lines. Furthermore, the flow of the medium can pass through the flow channel, which extends between the two support plates and in which the at least one heating resistor is arranged, through the openings of the two support plates.

Bei einer Variante des erfindungsgemäßen Heizwiderstandselementes ist der Heizwiderstand stoffschlüssig mit den Trägerplatten verbunden. Um die länglichen Heizwiderstände mit den Trägerplatten in Position zu halten, können diese vor, durch oder nach dem Sintern fest miteinander verbunden werden. Im Unterschied zu den klassischen elektrischen Widerstandsheizelementen sind die so hergestellten Heizelemente selbsttragend und müssen nicht durch ein zusätzliches Element geführt oder gestützt werden. Die Trägerplatten, die die keramischen Heizwiderstände an den beiden Seiten halten, müssen Temperaturen bis weit über 1000 °C, beispielsweise an der Luftaustrittsseite des Widerstandsheizelementes aushalten.In a variant of the heating resistor element according to the invention, the heating resistor is connected in a material-locking manner to the carrier plates. In order to hold the elongated heating resistors with the carrier plates in position, they can be firmly connected before, by or after sintering. In contrast to the classical electrical resistance heating elements, the heating elements thus produced are self-supporting and need not be guided or supported by an additional element. The support plates, which hold the ceramic heating resistors on both sides, must withstand temperatures well above 1000 ° C, for example on the air outlet side of the resistance heating element.

Der U-förmige keramische Heizwiderstand kann eine ebene oder eine strukturierte Oberfläche aufweisen. Bevorzugt wird eine Ausführungsform der Erfindung, bei der der Heizwiderstand Vertiefungen und/oder Erhöhungen aufweist, um die Oberfläche für den Kontakt mit dem Strom des gasförmigen Mediums gegenüber einer ebenen Oberfläche zu vergrößern. Durch die komplexere Geometrie wird neben einer möglichst großen Oberfläche für den Wärmeaustausch mit dem strömenden Medium auch erreicht, dass die in dem Strömungskanal an dem Heizwiderstand vorbeiströmende Medium verwirbelt wird. Dies bewirkt, dass der gesamte Medienstrom gleichmäßig und homogen erwärmt wird.The U-shaped ceramic heating resistor may have a planar or a structured surface. An embodiment of the invention is preferred in which the heating resistor has depressions and / or elevations in order to increase the surface area for contact with the flow of the gaseous medium in relation to a planar surface. Due to the more complex geometry, in addition to the largest possible surface for the heat exchange with the flowing medium, it is also achieved that the medium flowing past the heating resistor in the flow channel is swirled. This causes the entire media flow is uniformly and homogeneously heated.

Vorteilhafterweise ist das leitfähige Keramikmaterial des Heizwiderstandes eine Mischkeramik mit einer leitfähigen und einer nichtleitfähigen Komponente, wobei die leitfähige Keramikkomponente einen positiven Temperaturkoeffizienten zwischen 0 und 10000 ppm/K aufweist. Als leitfähige Keramikkomponente ist vorzugsweise Molybdändisilizid (MoSi2) und als nichtleitfähige Keramikkomponente vorzugsweise Aluminiumoxid (Al2O3) vorgesehen.Advantageously, the conductive ceramic material of the heating resistor is a mixed ceramic having a conductive and a non-conductive component, the conductive ceramic component having a positive temperature coefficient of between 0 and 10000 ppm / K. As a conductive ceramic component is preferably molybdenum disilicide (MoSi 2 ) and as a non-conductive ceramic component preferably alumina (Al 2 O 3 ) is provided.

Der vorzugsweise positive Temperaturkoeffizient sollte nicht zu steil ansteigen, da sich sonst Hot Spots bilden können. Auch sollte innerhalb der Gebrauchstemperatur bis etwa 1500 °C keine steile Flanke des spezifischen Widerstandes auftreten, wie es bei manchen elektrisch leitfähigen Keramiken mit positiven Temperaturkoeffizienten der Fall ist. Die Mischkeramik kann auch noch weitere Additive für die Verbesserung der Sinterfähigkeit oder der Stabilität aufweisen. Es ist auch möglich, das Aluminiumoxid durch andere isolierende Keramiken wie z. B. Oxid- oder Nitrid- oder Silikatkeramiken partiell zu substituieren. Durch den Anteil der leitenden Komponente kann der spezifische Widerstand des Materials in einem gewissen Bereich eingestellt werden. Ein Anteil von 20 bis 30 % Molybdändisilizid in der Mischkeramik hat sich als ideal herausgestellt. Damit können spezifische Widerstände zwischen 0,01 und 1,0 Ω·cm bei Raumtemperatur erreicht werden, die sich bis zu 1000 °C um den Faktor drei oder mehr erhöhen.The preferably positive temperature coefficient should not rise too steep, otherwise hot spots may form. Also within the service temperature up to about 1500 ° C no steep slope of the resistivity should occur, as with some electrically conductive ceramics with positive Temperature coefficient is the case. The mixed ceramic may also have other additives for improving sinterability or stability. It is also possible, the alumina by other insulating ceramics such. As oxide or nitride or silicate ceramics partially substitute. By the proportion of the conductive component, the specific resistance of the material can be adjusted within a certain range. A proportion of 20 to 30% molybdenum disilicide in the mixed ceramic has proven to be ideal. Thus, specific resistances between 0.01 and 1.0 Ω · cm can be achieved at room temperature, which increase up to 1000 ° C by a factor of three or more.

Die erfindungsgemäße Heizeinrichtung, beispielsweise für eine Heißlufteinrichtung, mit einem in einem Strom des gasförmigen Mediums angeordneten Widerstandsheizelement, das von einem Heizrohr umgriffen ist, weist ein erfindungsgemäßes elektrisches Widerstandsheizelement mit den Merkmalen des Anspruchs 1 auf. An dem einen Ende des Heizrohres wird als Medium beispielsweise Luft oder Gas eingeblasen und an dem anderen Ende des Heizrohrs tritt der erhitzte Luft- bzw. Gasstrom aus. Dabei kann der Luft- oder Gasstrom von einem an der Heizeinrichtung vorgesehenen Gebläse erzeugt oder der Heizeinrichtung von einem externen unter Überdruck stehenden Reservoir zugeführt werden.The heating device according to the invention, for example for a hot air device, with a arranged in a stream of gaseous medium resistance heating element, which is encompassed by a heating tube, has an inventive electrical resistance heating element with the features of claim 1. At the one end of the heating tube, for example, air or gas is blown in as a medium, and at the other end of the heating tube, the heated air or gas stream exits. In this case, the air or gas stream generated by a fan provided on the heater or the heater can be supplied from an external reservoir under pressure.

Nachfolgend wird die Erfindung anhand zweier in den begleitenden Zeichnungen dargestellten Ausführungsbeispiele näher erläutert. Weitere Merkmale der Erfindung ergeben sich aus der folgenden Beschreibung der Ausführungsbeispiele der Erfindung in Verbindung mit den Ansprüchen und den beigefügten Zeichnungen. Die einzelnen Merkmale der Erfindung können für sich allein oder zu mehreren bei unterschiedlichen Ausführungsformen der Erfindung verwirklicht sein. Die dargestellten Ausführungsbeispiele sind zum Erhitzen eines Luftstroms vorgesehen. Es stellen dar:

Figur 1
ein erfindungsgemäßes Widerstandsheizelement in einer Schnittdarstellung;
Figur 2
die Trägerplatten aus Figur 1 in Draufsicht;
Figur 3
den Heizwiderstand aus Figur 1 in perspektivischer Ansicht;
Figur 4
eine zweite Ausführungsform eines Heizwiderstandes mit glatter Oberfläche;
Figur 5
eine dritte Ausführungsform eines Heizwiderstandes mit strukturierter Oberfläche;
Figur 6
eine zweite Ausführungsform einer Trägerplatte passend zu den Heizwiderständen gemäß Figur 5;
Figur 7
eine erste erfindungsgemäße Heizeinrichtung in perspektivischer Ansicht; und
Figur 8
eine zweite erfindungsgemäße Heizeinrichtung in perspektivischer Ansicht.
The invention will be explained in more detail with reference to two embodiments illustrated in the accompanying drawings. Further features of the invention will become apparent from the following description of the embodiments of the invention in conjunction with the claims and the accompanying drawings. The individual features of the invention may be implemented on their own or in several different embodiments of the invention. The illustrated embodiments are provided for heating an air flow. They show:
FIG. 1
a resistance heating element according to the invention in a sectional view;
FIG. 2
the carrier plates FIG. 1 in plan view;
FIG. 3
the heating resistor off FIG. 1 in perspective view;
FIG. 4
a second embodiment of a heating resistor with a smooth surface;
FIG. 5
a third embodiment of a heating resistor with a structured surface;
FIG. 6
a second embodiment of a carrier plate according to the heating resistors according to FIG. 5 ;
FIG. 7
a first heating device according to the invention in a perspective view; and
FIG. 8
a second heater according to the invention in a perspective view.

Figur 1 zeigt eine Ausführungsform des erfindungsgemäßen Widerstandsheizelementes 1 mit vier Heizwiderständen 2 in einer Achsschnittdarstellung, von denen in der Zeichnung nur zwei sichtbar sind. Die Heizwiderstände 2 sind im wesentlichen stabförmig ausgebildet und weisen vordere und hintere Endabschnitte 3, 4 auf. Die hinteren Endabschnitte 4 sind einer Lufteintrittsseite 5 und die vorderen Endabschnitte einer Luftaustrittsseite 6 des Widerstandsheizelementes 1 zugeordnet. Die Heizwiderstände 2 sind dabei U-förmig mit ebener Oberfläche 7 ausgebildet und weisen Enden 8, 8', Schenkel 9, 9' sowie eine die Schenkel 9,9' verbindende Basis 10 auf. Die Enden 8' der Heizwiderstände 2 sind mittels einer elektrischen Brücke 11 elektrisch leitend verbunden. Zu den Enden 8 der Heizwiderstände 2 führen elektrische Zuleitungen 12. FIG. 1 shows an embodiment of the resistance heating element 1 according to the invention with four heating resistors 2 in an Achsschnittdarstellung, of which only two are visible in the drawing. The heating resistors 2 are formed substantially rod-shaped and have front and rear end portions 3, 4. The rear end sections 4 are associated with an air inlet side 5 and the front end sections of an air outlet side 6 of the resistance heating element 1. The heating resistors 2 are U-shaped with a flat surface 7 and have ends 8, 8 ', legs 9, 9' and a leg 9, 9 'connecting base 10. The ends 8 'of the heating resistors 2 are electrically connected by means of an electrical bridge 11. To the ends 8 of the heating resistors 2 lead electrical leads 12th

Die Heizwiderstände 2 sind von einer vorderen und hinteren Trägerplatte 13, 14 gehalten. Die Basis 10 ist mit der luftaustrittsseitigen vorderen Trägerplatte 13 formschlüssig in Eingriff, die beiden gegenüberliegenden Enden 8, 8' mit der lufteintrittsseitigen hinteren Trägerplatte 14. Die Trägerplatten 13, 14 sind mit einem zentralen, vorzugsweise vierkantigen Stift 15 aneinander festgelegt. Die Heizwiderstände 2 erstrecken sich in einen Luftkanal 16, der stirnseitig von den Trägerplatten 13, 14 und umfangsseitig von einem in der Zeichnung nicht dargestellten Heizrohr begrenzt wird, sobald das Heizelement 1 in eine Heißlufteinrichtung eingebaut ist.The heating resistors 2 are held by a front and rear support plate 13, 14. The base 10 is in positive engagement with the air outlet side front support plate 13, the two opposite ends 8, 8 'with the air inlet side rear support plate 14. The support plates 13, 14 are fixed to each other with a central, preferably four-edged pin 15. The heating resistors 2 extend into an air duct 16 which is delimited on the front side by the carrier plates 13, 14 and peripherally by a heating tube, not shown in the drawing, as soon as the heating element 1 is installed in a hot air device.

Das elektrische Widerstandsheizelement hat wie aus den Figuren 1, 2 ersichtlich, eine längliche im wesentlichen zylindrische Form. Figur 2 zeigt die als runde Flachscheibe ausgeführten Trägerplatten 13, 14, die aus einem elektrisch nicht leitfähigen Keramikmaterial hergestellt sind, in Draufsicht. Gezeigt wird die den Heizwiderständen 2 zugeordnete Innenseite. Die Trägerplatten 13, 14 weisen Ausnehmungen 17 mit Löchern 18 zur Aufnahme der vorderen und hinteren Endabschnitte 3, 4 der Heizwiderstände 2 auf. Des weiteren ist ein zentrales Befestigungsloch 20 für den die Trägerplatten 13, 14 verbindenden Stift 15 ausgebildet. Die Löcher 18 der Ausnehmungen 17 ermöglichen den elektrischen Anschluss der Heizwiderstände 2.The electrical resistance heating element has as from FIGS. 1, 2 seen, an elongated substantially cylindrical shape. FIG. 2 shows the designed as a round flat disc support plates 13, 14, which are made of an electrically non-conductive ceramic material, in plan view. Shown is the heating resistors 2 associated inside. The support plates 13, 14 have recesses 17 with holes 18 for receiving the front and rear end portions 3, 4 of the heating resistors 2. Furthermore, a central attachment hole 20 for the carrier plates 13, 14 connecting pin 15 is formed. The holes 18 of the recesses 17 allow the electrical connection of the heating resistors. 2

Figur 3 zeigt eine erste Ausführungsform des U-förmigen Heizwiderstandes 2 aus einem elektrisch leitfähigen Keramikmaterial. Die Schenkel 9, 9' sowie die Basis 10 haben eine quadratische Querschnittsform und liegen in einer Ebene. Die Oberfläche 7 ist eben. FIG. 3 shows a first embodiment of the U-shaped heating resistor 2 made of an electrically conductive ceramic material. The legs 9, 9 'and the base 10 have a square cross-sectional shape and lie in one plane. The surface 7 is flat.

In Figur 4 ist eine zweite Variante des in der Figur 3 gezeigten Heizwiderstandes 2 dargestellt, bei der Schenkel 9 eine rechteckige und der Schenkel 9' sowie die Basis 10 eine dreieckige Querschnittsform aufweisen, so dass sie zusammen ein Zylindersegment bilden, das einem Achtel eines geraden Kreiszylinders entspricht. Die Oberflächen 7 der Schenkel 9, 9' sind eben und zueinander geneigt ausgeführt.In FIG. 4 is a second variant of the in the FIG. 3 shown heating resistor 2 shown in the legs 9, a rectangular and the legs 9 'and the base 10 have a triangular cross-sectional shape, so that together they form a cylinder segment corresponding to one-eighth of a right circular cylinder. The surfaces 7 of the legs 9, 9 'are flat and inclined to each other.

Figur 5 zeigt eine dritte Ausführungsform des U-förmigen Heizwiderstandes 2. Die Schenkel 9, 9' und die Basis 10 haben eine im wesentlichen dreieckige Querschnittsform. Sie sind derart ausgeführt, dass sie zusammen ein Zylindersegment bilden, das einem Viertel eines Kreiszylinders entspricht. Die Oberfläche 7 der Schenkel 9, 9' ist strukturiert. Sie weist Vertiefungen 21 und Erhöhungen 22 auf, um die Oberfläche 7 für den Kontakt mit den Luftstrom zu vergrößern. Außerdem bewirkt die strukturierte Oberfläche 7 vorteilhafterweise eine Verwirbelung des Luftstroms und damit eine gleichmäßige Erwärmung. FIG. 5 shows a third embodiment of the U-shaped heating resistor 2. The legs 9, 9 'and the base 10 have a substantially triangular cross-sectional shape. They are designed so that together they form a cylinder segment which corresponds to a quarter of a circular cylinder. The surface 7 of the legs 9, 9 'is structured. It has recesses 21 and ridges 22 to increase the surface 7 for contact with the air flow. In addition, the structured surface 7 advantageously causes a turbulence of the air flow and thus a uniform heating.

Figur 6 zeigt die zu dem in der Figur 5 gezeigten Heizwiderstand 2 passenden Trägerplatten 13, 14. Die Trägerplatten 13, 14 weisen eine umlaufende, im wesentliche viereckige Ausnehmung 17 auf und sind zur stoffschlüssigen Verbindung mit den Heizwiderständen 2 geeignet. Dazu werden die Heizwiderstände 2 in den Ecken 23 der Ausnehmung 17 angeordnet. Im übrigen weisen die Trägerplatten 13, 14 noch Durchbrüche 19 für den Luftstrom und die ausgebildeten Ausnehmung 17 Löcher 18 für die elektrische Verbindung der Heizwiderstände 2 auf. FIG. 6 shows the to the in the FIG. 5 The carrier plates 13, 14 have a circumferential, substantially square recess 17 and are suitable for cohesive connection with the heating resistors 2. For this purpose, the heating resistors 2 are arranged in the corners 23 of the recess 17. Incidentally, the support plates 13, 14 have openings 19 for the air flow and the formed recess 17 holes 18 for the electrical connection of the heating resistors 2.

Die zu dem in der Figur 4 gezeigten Heizwiderstand 2 passenden Trägerplatten 13, 14 sind zeichnerisch nicht dargestellt. Sie können ähnlich den in der Figur 6 dargestellten Trägerplatten 13, 14 ausgebildet sein, wobei die Form der Ausnehmung 17 an die unterschiedliche Querschnittsform des Zylindersegments des Heizwiderstandes 2 angepasst ist.The to the in the FIG. 4 shown heating element 2 matching support plates 13, 14 are not shown in the drawing. They can be similar to those in the FIG. 6 be formed support plates 13, 14, wherein the shape of the recess 17 is adapted to the different cross-sectional shape of the cylinder segment of the heating resistor 2.

Die Figuren 7, 8 zeigen zwei Ausführungsformen von erfindungsgemäßen Heißtufteinrichtungen 24, 25. Bei der in der Figur 7 dargestellten Heißlufteinrichtung 24 handelt es sich um ein an einem Maschinengestell anflanschbares Heißtuftgerät ohne integriertes Gebläse. Der Luftstrom wird der Heißlufteinrichtung 24 von extern zugeführt. Die in der Figur 8 gezeigte Heißlufteinrichtung 25 ist mit einem internen Gebläse ausgestattet und kann als handführbares Heißluftgerät verwendet werden. Ansonsten sind die beiden Geräte im wesentlichen gleich ausgebildet. Sie weisen ein Gehäuse 26 mit einem vorderen Heizrohr 27 auf. In dem Heizrohr 27 ist das erfindungsgemäße Widerstandsheizelement 1 in der Zeichnung nicht sichtbar eingebaut. Dabei weist die Luftaustrittsseite 6 des Widerstandsheizelementes 1 zu der Luftaustrittsöffnung 28 des Heizrohres 27 und die Lufteintrittsseite 5 zum hinteren Ende des Gehäuses 26. Über das Gehäuse 26 werden die Heizwiderstände 2 des Widerstandsheizelementes 1 mit elektrischer Spannung versorgt.The FIGS. 7, 8 show two embodiments of Heißtufteinrichtungen invention 24, 25. In the in the FIG. 7 shown hot air device 24 is a flanged on a machine frame hot tufting device without integrated fan. The air flow is supplied to the hot air device 24 from the outside. The in the FIG. 8 shown hot air device 25 is equipped with an internal fan and can be used as a hand-held hot air device. Otherwise, the two devices are formed substantially the same. They have a housing 26 with a front heating tube 27. In the heating tube 27 is the invention Resistance heating element 1 is not visible installed in the drawing. In this case, the air outlet side 6 of the resistance heating element 1 to the air outlet opening 28 of the heating tube 27 and the air inlet side 5 to the rear end of the housing 26. About the housing 26, the heating resistors 2 of the resistance heating element 1 are supplied with electrical voltage.

Claims (10)

  1. Electrical resistance heating element (1) for heating a gaseous medium, with at least one heating resistor (2) that extends essentially in the longitudinal direction of the electrical resistance heating element (1), with the medium flowing past the heating resistor and being heated in the process, and with at least one flow canal (16) that extends along the heating resistor (2) and through which the medium is able to flow from a canal inlet side (5) to a canal outlet side (6) of the resistance heating element (1), with the heating resistor (2) comprising an electrically conductive ceramic material for conducting the current, characterized in that the heating resistor (2) is rod-shaped and is held by carrier plates (13, 14) that are located at the canal inlet side (5) and the canal outlet side (6) of the resistance heating element (1), with the flow canal (16) continuing in said carrier plates, and with the heating resistor (2) positively engaging the carrier plates (13, 14) at its ends (8, 8', 10).
  2. Resistance heating element (1) as claimed in Claim 1, characterized in that the conductive ceramic material has a specific resistance of between 0.01 and 1.0 Ω cm.
  3. Resistance heating element (1) as claimed in Claims 1 or 2, characterized in that the ratio of the length to the cross-sectional area of the ceramic material of the heating resistor ranges amounts between 1 and 500 cm-1.
  4. Resistance heating element (1) as claimed in any one of the preceding Claims, characterized in that the heating resistor (2) is essentially U-shaped.
  5. Resistance heating element (1) as claimed in any one of the preceding Claims, characterized in that the carrier plates (13, 14) are formed from an electrically non-conductive ceramic material.
  6. Resistance heating element (1) as claimed in any one of the preceding Claims, characterized in that the carrier plates (13, 14) have recesses (17) that match the cross-sectional shape of the heating resistor (2) and serve to accept the ends (8, 8', 10) of the heating resistor (2), and also have passages (19) through which the flow of the gaseous medium is able to pass.
  7. Resistance heating element (1) as claimed in any one of the preceding Claims, characterized in that the heating resistor (2) is positively connected to the carrier plates (13, 14).
  8. Resistance heating element (1) as claimed in any one of the preceding Claims, characterized in that the heating resistor (2) has indentations (21) and/or elevations (22) in order to enlarge its surface (7) for the contact with the flow of the gaseous medium, in comparison with a flat surface.
  9. Resistance heating element (1) as claimed in any one of the preceding Claims, characterized in that the conductive ceramic material is a mixed ceramic material comprising a conductive and a non-conductive component, wherein the conductive ceramic component has a positive thermal coefficient, and with molybdenum disilicide (MoSi2) preferably used as conductive ceramic component, and with aluminum oxide (Al2O3) preferably used as non-conductive ceramic component.
  10. Heating device (24, 25) for heating a flowing gaseous medium, comprising an electrical heating element (1) surrounded by a heating tube (27) positioned in a flow of the gaseous medium, wherein the flow is generated by a blower provided at the heating device (25) or is provided from an external pressurized reservoir, characterized by a resistance heating element (1) as claimed in any one of the preceding Claims 1 to 9.
EP08010426A 2008-06-09 2008-06-09 Electric resistance heat element for a heating device for heating a flowing gaseous medium Active EP2134143B1 (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
EP08010426A EP2134143B1 (en) 2008-06-09 2008-06-09 Electric resistance heat element for a heating device for heating a flowing gaseous medium
AT08010426T ATE492140T1 (en) 2008-06-09 2008-06-09 ELECTRICAL RESISTANCE HEATING ELEMENT FOR A HEATING DEVICE FOR HEATING A FLOWING GASEOUS MEDIUM
DE502008002030T DE502008002030D1 (en) 2008-06-09 2008-06-09 Electrical resistance heating element for a heating device for heating a flowing gaseous medium
JP2009125138A JP4977844B2 (en) 2008-06-09 2009-05-25 Resistance heating element of flowing gas heating device
US12/478,825 US20090304372A1 (en) 2008-06-09 2009-06-05 Electrical resistance heating element for a heating device for heating a flowing gaseous medium
CN2009102034001A CN101603733B (en) 2008-06-09 2009-06-09 Electric resistance heat element for a heating device for heating a flowing gaseous medium

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP08010426A EP2134143B1 (en) 2008-06-09 2008-06-09 Electric resistance heat element for a heating device for heating a flowing gaseous medium

Publications (2)

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EP2134143A1 EP2134143A1 (en) 2009-12-16
EP2134143B1 true EP2134143B1 (en) 2010-12-15

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US (1) US20090304372A1 (en)
EP (1) EP2134143B1 (en)
JP (1) JP4977844B2 (en)
CN (1) CN101603733B (en)
AT (1) ATE492140T1 (en)
DE (1) DE502008002030D1 (en)

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Also Published As

Publication number Publication date
EP2134143A1 (en) 2009-12-16
DE502008002030D1 (en) 2011-01-27
JP4977844B2 (en) 2012-07-18
US20090304372A1 (en) 2009-12-10
CN101603733B (en) 2012-08-29
CN101603733A (en) 2009-12-16
ATE492140T1 (en) 2011-01-15
JP2009293916A (en) 2009-12-17

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