WO1995002952A1 - Electric heating unit - Google Patents

Electric heating unit Download PDF

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Publication number
WO1995002952A1
WO1995002952A1 PCT/CH1994/000143 CH9400143W WO9502952A1 WO 1995002952 A1 WO1995002952 A1 WO 1995002952A1 CH 9400143 W CH9400143 W CH 9400143W WO 9502952 A1 WO9502952 A1 WO 9502952A1
Authority
WO
WIPO (PCT)
Prior art keywords
heating unit
unit according
electric heating
carrying
solid body
Prior art date
Application number
PCT/CH1994/000143
Other languages
German (de)
French (fr)
Other versions
WO1995002952B1 (en
Inventor
Dusko Maravic
Original Assignee
Dusko Maravic
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Dusko Maravic filed Critical Dusko Maravic
Priority to AU70670/94A priority Critical patent/AU7067094A/en
Priority to EP94919544A priority patent/EP0659328A1/en
Priority to PL94308110A priority patent/PL308110A1/en
Publication of WO1995002952A1 publication Critical patent/WO1995002952A1/en
Publication of WO1995002952B1 publication Critical patent/WO1995002952B1/en

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Classifications

    • 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
    • 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
    • H05B2203/021—Heaters specially adapted for heating liquids

Definitions

  • the present invention relates to an electrical heating unit with a current-carrying resistance heating element and a solid body which carries or guides the object to be heated or the medium to be heated.
  • Conventional electrical heating units have heating elements which are formed from conductors through which current flows.
  • Preferred materials are Cr-Ni alloys, which have a specific electrical resistance p of approximately 1-10 " 6 ⁇ m. Since the specific resistance p of electrical conductors is very small, the conductor must have the smallest possible cross-sectional area and a great length, So that a sufficiently large effective resistance R is obtained. Therefore, conventional resistance heating elements are formed from thin wires that are spirally wound. Nevertheless, the resistance R of these heating wires is so small that the input power is high even at low voltages. The wire therefore quickly has one high temperature, typical temperature values are 1000 ° C.
  • the resistance wire is separated from the liquid or gaseous medium or object to be heated by a solid, usually electrically insulated body. This carries the object to be heated or guides the medium to be heated.
  • heating units A typical example of such heating units is the electric hotplate.
  • the glass ceramic disc on which the pan to be heated is located is spaced above the heating coil.
  • Another example is the instantaneous water heater.
  • the water to be heated is guided in tubes which are wound at a distance with helically wound resistance wires.
  • the object or the medium is heated less by heat conduction than by heat radiation.
  • These examples illustrate the disadvantages of the known heating units with resistance heating elements.
  • This intermediate element has a large mass and is usually also a poor heat conductor because it is electrically insulated. This system is therefore very sluggish in terms of heat transfer. Therefore, the heating element must have a much higher temperature than would be effectively achieved with the object or medium.
  • a large part of the heating power is lost because the heat radiation is radiated in all directions. The efficiency of known heating units is therefore very low.
  • an electrical heating unit according to the preamble of claim 1, which is characterized in that the load-bearing or leading massive Body simultaneously forms the current-carrying resistance heating element.
  • the electric heating unit according to the invention like the known heating units, has a current-carrying resistance heating element.
  • this is designed as a solid, that is, as a solid and massive body.
  • it can be designed as a tube or plate.
  • This solid body is not only used as a heat source in the heating unit according to the invention, but also to carry the object to be heated or, in the case of a gas or a liquid, to guide it.
  • the resistance heating element according to the invention is not, as is known, made from an electrically conductive material with a small specific electrical resistance, but from a material which has a considerably higher specific resistance.
  • the materials used are semiconductors, such as silicon carbide, high-performance plastics doped with carbon, graphite or metal, or other semiconductor-like materials. These materials have a significantly higher resistivity p than those previously used. Typical values are between 10 ⁇ 4 to 1 ⁇ m.
  • the specific resistance p of the materials used and thus also their effective resistance R are sufficiently large that a small cross section and a large length do not Condition for the resistance heating element represents more.
  • the energy converted into heat at constant voltage is somewhat lower than in the case of conventional conductive resistance heating elements.
  • the heating element can be controlled for a low to medium temperature. Typical temperatures are between 50 ° C and 700 ° C.
  • the semiconducting resistance heating element designed as a solid body has several advantages.
  • the heating element can already be regulated at low temperatures, it can be heated to a temperature which is only slightly higher than the desired end temperature of the object or medium. As a result, it can be brought into contact with the object or medium to be heated, so that the heat transfer can take place by heat conduction and not by heat radiation.
  • the heating element is designed as a solid body, the contact area with the object or medium is large. The heat transfer can take place over this large area. In addition, no additional solid intermediate element is required which inhibits heat transfer. Therefore, from a reverse perspective, the low to medium temperature of the heat source is sufficient to achieve the desired temperature on the object or medium.
  • the efficiency of the heating unit according to the invention is accordingly considerably higher than that of conventional heating units with resistance heating wires.
  • the heating unit according to the invention is energy-saving.
  • the surfaces of the heating element that are not used for heat transfer can be thermally insulated.
  • the heat is brought specifically to the required location. The losses from heat radiation are kept low.
  • the solid body of the resistance heating element is electrically insulated from the medium or object to be heated.
  • the insulation layer can be, for example, a ceramic coating with a coefficient of thermal expansion similar to that of the solid body.
  • An electrically insulating material with the best possible heat-conducting properties is preferably selected.
  • Figure 1 is a heating unit in the form of a tube
  • FIG. 2 shows a heating unit with a plate-shaped resistance heating element
  • FIG. 3 shows a hotplate according to the invention.
  • a tubular resistance heating element is shown in FIG. It consists of a pipe section 1 which has well-conductive metallic contacts 2 at each of its ends with large contact areas for creating a circuit. If a voltage source is connected to these contacts, a current flows through the tube. This is heated according to its resistance R.
  • Such a resistance heating element is used, for example, in a water heater or a dishwasher.
  • the pipe section 1 of the resistance heating element is then at the same time the pipe for the water to be heated.
  • the water flows in the interior 3 of the tube 1.
  • the water is heated by direct contact with the hot tube wall. Since the tube wall only has an insignificantly higher temperature than the desired water temperature, there are no structural conversions of the water and the efficiency is considerably higher than with conventional instantaneous water heaters.
  • the pipe can be surrounded with a thermally insulated jacket.
  • the heating unit must be surrounded with an electrically insulating jacket from the surroundings.
  • the medium to be heated, the liquid or the gas remains direct Contact with the pipe serving as a heat source.
  • silicone rubber is used as insulation material.
  • a thin insulation layer of this type is also applied to the inner wall of the current-carrying tube.
  • a resistance heating element is shown in the form of a plate.
  • electrical contacts 2 are attached to both ends of the plate. They can be attached to the end faces of the plate or, as shown, enclose the circumference of the plate.
  • the plate is simultaneously the heat source and the solid body carrying the object to be heated.
  • the plate is covered with an electrically insulating layer which, however, has the best possible heat-conducting properties.
  • the lower side of the plate if not used for heat transfer, can be thermally insulated.
  • Application examples are hot plates in household use or heating elements that are immersed in a container filled with liquid.
  • FIG. 3 An application example of such a plate is shown in Figure 3.
  • the resistance element is used as a hotplate.
  • the lower side 5 of the plate 4 is electrically and thermally insulated.
  • the upper side 6 has an electrical insulation layer.
  • the saucepan to be heated is placed on this.
  • This hotplate also has the top described advantages and thus enables energy-saving preparation of meals.
  • the supporting heating element is in contact with another solid body.
  • This body has electrically insulating, but good heat-conducting properties.
  • this massive insulation is used instead of the insulation layer described above.
  • This insulating body separates the supporting heating element from the medium or object to be heated.
  • such an insulation body connects several solid heating elements to one another, which thus form a common heating unit.
  • the optimization of all essential parameters must be calculated for each application example.
  • the length and cross-sectional area of the resistance heating element must be selected so that the resulting resistance R has the size necessary to achieve the desired temperature.
  • the requirement must be met that the stability of the body is sufficient to carry the medium or carry the object.
  • the material is a freely selectable parameter in some cases.
  • the specific resistance can be changed the doping of the silicon carbide or the plastic vary.

Landscapes

  • Resistance Heating (AREA)

Abstract

A heating unit has a current-flow resistance heating element designed as a massive body, for example as a tube (1) or as a plate. This body made of a semiconducting material carries the object to be heated or leads the medium to be warmed up. A large contact surface for heat transfer is thus made available, and a high efficiency is achieved. The invention may be applied in flow heaters, heating and cooking plates.

Description

Elektrische Heizeinheit Electric heating unit
Die vorliegende Erfindung betrifft eine elektrische Heizein¬ heit mit einem stromdurchflossenen Widerstandsheizelement und einem, den zu heizenden Gegenstand oder das zu erwärmende Medium tragenden beziehungsweise führenden, massiven Körper.The present invention relates to an electrical heating unit with a current-carrying resistance heating element and a solid body which carries or guides the object to be heated or the medium to be heated.
Konventionelle elektrische Heizeinheiten weisen Heizelemente auf, die aus stromdurchflossenen Leitern gebildet werden. Bevorzugte Materialien sind Cr-Ni-Legierungen, die einen spezifischen elektrischen Widerstand p von circa 1-10"6 Ωm aufweisen. Da der spezifische Widerstand p von elektrischen Leitern sehr klein ist, muss der Leiter eine möglichst kleine Querschnittsfläche und eine grosse Länge aufweisen, damit ein genügend grosser effektiver Widerstand R erhalten wird. Deshalb werden konventionelle Widerstandsheizelemente aus dünnen Drähten gebildet, die spiralförmig gewickelt sind. Trotzdem ist der Widerstand R dieser Heizdrähte so klein, dass schon bei kleinen Spannungen die Eingangsleistung gross ist. Der Draht weist somit schnell eine hohe Temperatur auf. Typische Temperaturwerte liegen bei 1000°C.Conventional electrical heating units have heating elements which are formed from conductors through which current flows. Preferred materials are Cr-Ni alloys, which have a specific electrical resistance p of approximately 1-10 " 6 Ωm. Since the specific resistance p of electrical conductors is very small, the conductor must have the smallest possible cross-sectional area and a great length, So that a sufficiently large effective resistance R is obtained. Therefore, conventional resistance heating elements are formed from thin wires that are spirally wound. Nevertheless, the resistance R of these heating wires is so small that the input power is high even at low voltages. The wire therefore quickly has one high temperature, typical temperature values are 1000 ° C.
Der Widerstandsdraht ist von dem zu erwärmenden, flüssigen oder gasförmigen, Medium oder Gegenstand durch einen massi¬ ven, meist elektrisch isolierten Körper getrennt. Dieser trägt den zu heizenden Gegenstand oder führt das zu erwär¬ mende Mediu .The resistance wire is separated from the liquid or gaseous medium or object to be heated by a solid, usually electrically insulated body. This carries the object to be heated or guides the medium to be heated.
Ein typisches Beispiel derartiger Heizeinheiten ist die elek¬ trische Kochplatte. Beabstandet über der Heizspirale befindet sich die Glaskeramikscheibe, auf der sich die zu erwärmende Pfanne befindet.A typical example of such heating units is the electric hotplate. The glass ceramic disc on which the pan to be heated is located is spaced above the heating coil.
Ein weiteres Beispiel ist der Durchlauferhitzer. Das zu erwärmende Wasser wird in Rohren geführt, die mit spiral¬ förmig gewickelten Widerstandsdrähten beabstandet umwickelt sind.Another example is the instantaneous water heater. The water to be heated is guided in tubes which are wound at a distance with helically wound resistance wires.
In beiden Beispielen erfolgt die Erwärmung des Gegenstandes oder des Mediums weniger durch Wärmeleitung als durch Wärme¬ strahlung. Diese Beispiele verdeutlichen die Nachteile der bekannten Heizeinheiten mit Widerstandsheizelementen. Es ist stets ein Zwischenelement zwischen der Wärmequelle, dem Heiz- draht, und der Wärmesenke, dem Gegenstand oder Medium, notwendig. Dieses Zwischenelement weist eine grosse Masse auf und ist meist auch noch ein schlechter Wärmeleiter, da er elektrisch isoliert ist. Dieses System ist somit bezüglich der Wärmeübertragung sehr träge. Deshalb muss das Heizelement eine viel höhere Temperatur aufweisen als effektiv beim Gegenstand oder Medium erzielt werden möchte. Zudem geht ein Grossteil der Heizleistung verloren, da die Wärmestrahlung in allen Richtungen abgestrahlt wird. Der Wirkungsgrad bekannter Heizeinheiten ist demzufolge sehr klein. Eine Erhöhung des Wirkungsgrades könnte erzielt werden, indem der zu erwärmende Gegenstand oder das Medium in wärmeleiten¬ den Kontakt mit der Wärmequelle gebracht wird. Dies ist aber bei den herkömmlichen Heizdrähten nicht durchführbar. Wie bereits erwähnt, können keine niedrigen bis mittleren Tempe¬ raturen erzielt werden. Berührung mit dem heissen Heizelement kann zu Strukturveränderungen des Gegenstandes oder des Mediums führen. Ebenso können die Wärmeübertragung hemmende Randeffekte auftreten.In both examples, the object or the medium is heated less by heat conduction than by heat radiation. These examples illustrate the disadvantages of the known heating units with resistance heating elements. There is always an intermediate element between the heat source, the heating wire, and the heat sink, the object or medium. This intermediate element has a large mass and is usually also a poor heat conductor because it is electrically insulated. This system is therefore very sluggish in terms of heat transfer. Therefore, the heating element must have a much higher temperature than would be effectively achieved with the object or medium. In addition, a large part of the heating power is lost because the heat radiation is radiated in all directions. The efficiency of known heating units is therefore very low. An increase in efficiency could be achieved by bringing the object to be heated or the medium into heat-conducting contact with the heat source. However, this cannot be carried out with conventional heating wires. As already mentioned, low to medium temperatures cannot be achieved. Touching the hot heating element can lead to structural changes in the object or the medium. Edge effects inhibiting heat transfer can also occur.
Eine optimale Wärmeübertragung ist zudem erst dann vorhanden, wenn die Kontaktfläche zwischen den wärmetauschenden Medien möglichst gross ist. Aus den bisher verwendeten Materialien kann jedoch kein grossflächiges Heizelement gebaut werden, da ihr spezifischer Widerstand zu klein ist.Optimal heat transfer is only available if the contact area between the heat-exchanging media is as large as possible. However, a large-area heating element cannot be built from the materials used hitherto, since their specific resistance is too small.
In Hinblick auf die immer bedeutendere Forderung, dass elek¬ trische Energie möglichst effizient und sparsam verwendet werden soll, können diese bekannten Heizeinheiten nicht mehr genügen.In view of the increasingly important requirement that electrical energy should be used as efficiently and economically as possible, these known heating units can no longer suffice.
Es ist deshalb Aufgabe der vorliegenden Erfindung, eine elek¬ trische Heizeinheit zu schaffen, die einen hohen Wirkungsgrad in der Wärmeübertragung von der Wärmequelle zu der Wärmesenke gewährleistet.It is therefore an object of the present invention to provide an electrical heating unit which ensures high efficiency in the heat transfer from the heat source to the heat sink.
Diese Aufgabe löst eine elektrische Heizeinheit gemäss Ober¬ begriff des Patentanspruchs 1, die dadurch gekennzeichnet ist, dass der tragende, beziehungsweise führende, massive Körper gleichzeitig das stromdurchflossene Widerstands- heizelement bildet.This object is achieved by an electrical heating unit according to the preamble of claim 1, which is characterized in that the load-bearing or leading massive Body simultaneously forms the current-carrying resistance heating element.
Die erfindungsgemässe elektrische Heizeinheit weist wie die bekannten Heizeinheiten ein stromdurchflossenes Widerstands¬ heizelement auf. Dieses ist jedoch als massiver, das heisst als fester und wuchtiger Körper ausgebildet. Es kann beispielsweise als Rohr oder Platte gestaltet sein. Dieser massive Körper wird in der erfindungsgemässen Heizeinheit nicht nur als Wärmequelle eingesetzt, sondern auch um den zu erwärmenden Gegenstand zu tragen oder, im Falle eines Gases oder einer Flüssigkeit, dieses zu führen.The electric heating unit according to the invention, like the known heating units, has a current-carrying resistance heating element. However, this is designed as a solid, that is, as a solid and massive body. For example, it can be designed as a tube or plate. This solid body is not only used as a heat source in the heating unit according to the invention, but also to carry the object to be heated or, in the case of a gas or a liquid, to guide it.
Das erfindungsgemässe Widerstandsheizelement ist nicht, wie bekannt, aus einem elektrisch leitenden Material mit kleinem spezifischen elektrischen Widerstand gefertigt, sondern aus einem einen beträchlich höheren spezifischen Widerstand auf¬ weisenden Material. Beispiele der verwendeten Materialien sind Halbleiter, wie Siliciumkarbid, mit Kohlenstoff, Graphit oder Metall dotierte Hochleistungs-Kunststoffe oder andere halbleiterähnliche Materialien. Diese Materialien haben einen beträchtlich höheren spezifischen Widerstand p als die bisher verwendeten. Typische Werte liegen zwischen 10~4 bis 1 Ωm.The resistance heating element according to the invention is not, as is known, made from an electrically conductive material with a small specific electrical resistance, but from a material which has a considerably higher specific resistance. Examples of the materials used are semiconductors, such as silicon carbide, high-performance plastics doped with carbon, graphite or metal, or other semiconductor-like materials. These materials have a significantly higher resistivity p than those previously used. Typical values are between 10 ~ 4 to 1 Ωm.
Der spezifische Widerstand p der verwendeten Materialien und damit auch deren effektiver Widerstand R sind genügend gross, so dass ein kleiner Querschnitt und eine grosse Länge keine Bedingung für das Widerstandsheizelement mehr darstellt. Zudem ist die bei gleichbleibender Spannung in Wärme umgewan¬ delte Energie wegen dem höheren Widerstand um einiges tiefer als bei den herkömmlichen leitenden Widerstandsheizelementen. Das Heizelement lässt sich schon für eine niedrige bis mittlere Temperatur regeln. Typische Temperaturen liegen bei 50°C bis 700°C.The specific resistance p of the materials used and thus also their effective resistance R are sufficiently large that a small cross section and a large length do not Condition for the resistance heating element represents more. In addition, due to the higher resistance, the energy converted into heat at constant voltage is somewhat lower than in the case of conventional conductive resistance heating elements. The heating element can be controlled for a low to medium temperature. Typical temperatures are between 50 ° C and 700 ° C.
Das als massiver Körper ausgebildete, halbleitende Wider¬ standsheizelement birgt mehrere Vorteile.The semiconducting resistance heating element designed as a solid body has several advantages.
Da das Heizelement bereits bei tiefen Temperaturen regelbar ist, kann es auf eine Temperatur erwärmt werden, die nur leicht höher als die gewünschte Endtemperatur des Gegen¬ standes oder Mediums liegt. Dadurch kann es in Kontakt mit dem zu erwärmenden Gegenstand oder Medium gebracht werden, so dass die Wärmeübertragung durch Wärmeleitung und nicht durch Wärmestrahlung erfolgen kann.Since the heating element can already be regulated at low temperatures, it can be heated to a temperature which is only slightly higher than the desired end temperature of the object or medium. As a result, it can be brought into contact with the object or medium to be heated, so that the heat transfer can take place by heat conduction and not by heat radiation.
Da das Heizelement als massiver Körper ausgebildet ist, ist die Kontaktfläche zum Gegenstand oder Medium gross. Die Wärmeübertragung kann über diese grosse Fläche erfolgen. Zudem ist kein zusätzliches massives Zwischenelement erfor¬ derlich, das die Wärmeübertragung hemmt. Daher reicht, in umgekehrter Betrachtungsweise, die niedrige bis mittlere Temperatur der Wärmequelle zu Erzielung der gewünschten Temperatur am Gegenstand oder Medium aus.Since the heating element is designed as a solid body, the contact area with the object or medium is large. The heat transfer can take place over this large area. In addition, no additional solid intermediate element is required which inhibits heat transfer. Therefore, from a reverse perspective, the low to medium temperature of the heat source is sufficient to achieve the desired temperature on the object or medium.
Der Wirkungsgrad der erfindungsgemässen Heizeinheit ist dem¬ nach beträchtlich höher als bei konventionellen Heizeinheiten mit Widerstandsheizdrähten. Die erfindungsgemässe Heizeinheit ist energiesparend.The efficiency of the heating unit according to the invention is accordingly considerably higher than that of conventional heating units with resistance heating wires. The heating unit according to the invention is energy-saving.
Zur zusätzlichen Erhöhung des Wirkungsgrades können die nicht zur Wärmeübertragung verwendeten Flächen des Heizelementes thermisch isoliert werden. Die Wärme wird so gezielt an die benötigte Stelle gebracht. Die Verluste durch Wärmestrahlung sind gering gehalten.To further increase the efficiency, the surfaces of the heating element that are not used for heat transfer can be thermally insulated. The heat is brought specifically to the required location. The losses from heat radiation are kept low.
Je nach Anwendungsbereich wird der massive Körper des Wider¬ standsheizelementes gegenüber dem zu erwärmenden Medium oder Gegenstand elektrisch isoliert. Die Isolationsschicht kann beispielsweise ein Keramiküberzug mit ähnlichem Wärmeausdeh¬ nungskoeffizient wie der massive Körper sein. Vorzugsweise wird ein elektrisch isolierendes Material mit möglichst guten wärmeleitenden Eigenschaften gewählt.Depending on the area of application, the solid body of the resistance heating element is electrically insulated from the medium or object to be heated. The insulation layer can be, for example, a ceramic coating with a coefficient of thermal expansion similar to that of the solid body. An electrically insulating material with the best possible heat-conducting properties is preferably selected.
In den Zeichnungen sind Ausführungsbeispiele des Erfindungs¬ gegenstandes dargestellt und in der nachfolgenden Beschrei¬ bung erläutert. Es zeigen:Exemplary embodiments of the subject matter of the invention are shown in the drawings and are explained in the following description. Show it:
Figur 1 eine Heizeinheit in Form eines Rohres;Figure 1 is a heating unit in the form of a tube;
Figur 2 eine Heizeinheit mit einem plattenförmigen Wider¬ standsheizelement;FIG. 2 shows a heating unit with a plate-shaped resistance heating element;
Figur 3 eine erfindungsgemässe Kochplatte. In Figur 1 ist ein rohrförmiges Widerstandsheizelement darge¬ stellt. Es besteht aus einem Rohrstück l, das an jedem seiner Enden gut leitende metallische Kontakte 2 mit grossen Kon¬ taktflächen zur Erstellung eines Stromkreises aufweist. Wird eine Spannungsquelle an diese Kontakte angeschlossen, so fliesst ein Strom durch das Rohr. Dieses wird entsprechend seinem Widerstand R erhitzt.Figure 3 shows a hotplate according to the invention. A tubular resistance heating element is shown in FIG. It consists of a pipe section 1 which has well-conductive metallic contacts 2 at each of its ends with large contact areas for creating a circuit. If a voltage source is connected to these contacts, a current flows through the tube. This is heated according to its resistance R.
Ein derartiges Widerstandsheizelement wird beispielsweise in einem Durchlauferhitzer oder einer Geschirrspülmaschine verwendet . Das Rohrstück 1 des Widerstandsheizelementes ist dann gleichzeitig die Rohrleitung für das zu erwärmende Wasser. Das Wasser fliesst im Innern 3 des Rohres 1. Durch den direkten Kontakt mit der heissen Rohrwandung wird das Wasser erwärmt. Da die Rohrwandung nur eine unwesentlich höhere Temperatur als die gewünschte Wassertemperatur aufweist, treten keine Strukturumwandlungen des Wassers auf und der Wirkungsgrad ist wesentlich höher als bei konven¬ tionellen Durchlauferhitzern. Um unerwünschten Wärmeverlust an die Umgebung zu verhindern, kann das Rohr mit einem thermisch isolierten Mantel umgeben sein.Such a resistance heating element is used, for example, in a water heater or a dishwasher. The pipe section 1 of the resistance heating element is then at the same time the pipe for the water to be heated. The water flows in the interior 3 of the tube 1. The water is heated by direct contact with the hot tube wall. Since the tube wall only has an insignificantly higher temperature than the desired water temperature, there are no structural conversions of the water and the efficiency is considerably higher than with conventional instantaneous water heaters. To prevent unwanted heat loss to the environment, the pipe can be surrounded with a thermally insulated jacket.
Wird eine Niederspannung, das heisst eine Spannung kleiner als 50 V, an das Rohr angelegt, so ist keine spezielle elek¬ trische Isolation notwendig.If a low voltage, that is to say a voltage of less than 50 V, is applied to the tube, no special electrical insulation is necessary.
Wird jedoch eine Spannung von 220 V verwendet, so muss die Heizeinheit gegenüber der Umgebung mit einem elektrisch iso¬ lierenden Mantel umgeben werden. Das zu erwärmende Medium, die Flüssigkeit oder das Gas, bleibt trotzdem in direktem Kontakt mit dem als Wärmequelle dienenden Rohr. Als Isolationsmaterial wird beispielsweise Silikon-Kautschuk verwendet. Eine dünne derartige Isolationsschicht wird in einer speziellen Ausführungsform auch auf der inneren Wandung des stromdurchflossenen Rohres angebracht.However, if a voltage of 220 V is used, the heating unit must be surrounded with an electrically insulating jacket from the surroundings. The medium to be heated, the liquid or the gas, remains direct Contact with the pipe serving as a heat source. For example, silicone rubber is used as insulation material. In a special embodiment, a thin insulation layer of this type is also applied to the inner wall of the current-carrying tube.
In Figur 2 ist ein Widerstandsheizelement in Form einer Platte dargestellt. An beiden Enden der Platte sind wie in der bereits beschriebenen Ausführungsform elektrische Kontakte 2 angebracht. Sie können an den Stirnflächen der Platte befestigt sein oder, wie dargestellt, den Umfang der Platte umfassen. Auch in diesem Beispiel ist die Platte gleichzeitig die Wärmequelle und der massive, den zu erwär¬ mende Gegenstand tragende Körper. Je nach angelegter Spannung wird die Platte mit einer elektrisch isolierenden Schicht bedeckt, die aber möglichst gute wärmeleitende Eigenschaften aufweist. Ebenso kann die untere Seite der Platte, falls sie nicht zur Wärmeübertragung verwendet wird, thermisch isoliert sein. Anwendungsbeispiele sind Wärmeplatten im Haushalts- gebrauch oder Heizelemente, die in einen mit Flüssigkeit gefüllten Behälter eingetaucht werden.In Figure 2, a resistance heating element is shown in the form of a plate. As in the embodiment already described, electrical contacts 2 are attached to both ends of the plate. They can be attached to the end faces of the plate or, as shown, enclose the circumference of the plate. In this example too, the plate is simultaneously the heat source and the solid body carrying the object to be heated. Depending on the voltage applied, the plate is covered with an electrically insulating layer which, however, has the best possible heat-conducting properties. Likewise, the lower side of the plate, if not used for heat transfer, can be thermally insulated. Application examples are hot plates in household use or heating elements that are immersed in a container filled with liquid.
Ein Anwendungsbeispiel einer derartigen Platte ist in Figur 3 dargestellt. Das Widerstandselement wird als Kochplatte verwendet. Die untere Seite 5 der Platte 4 ist elektrisch und thermisch isoliert. Die obere Seite 6 weist eine elektrische Isolationsschicht auf. Auf diese wird der zu erwärmende Kochtopf gestellt. Auch diese Kochplatte weist die oben beschriebenen Vorteile auf und ermöglicht so eine energie¬ sparende Zubereitung von Mahlzeiten.An application example of such a plate is shown in Figure 3. The resistance element is used as a hotplate. The lower side 5 of the plate 4 is electrically and thermally insulated. The upper side 6 has an electrical insulation layer. The saucepan to be heated is placed on this. This hotplate also has the top described advantages and thus enables energy-saving preparation of meals.
In einem weiteren, nicht dargestellten Ausführungsbeispiel ist das tragende Heizelement mit einem weiteren massiven Körper in Kontakt. Dieser Körper weist elektrisch isolie¬ rende, aber gut wärmeleitende Eigenschaften auf. Im Falle einer Kochplatte oder einer Wärmeplatte wird diese massive Isolation anstelle der oben beschriebenen Isolationsschicht verwendet. Als Isolationsmaterial wird beispielweise Alumi¬ niumnitrid (AlN) . Dieser Isolationskörper trennt das tragende Heizelement von dem zu erwärmenden Medium oder Gegenstand.In a further embodiment, not shown, the supporting heating element is in contact with another solid body. This body has electrically insulating, but good heat-conducting properties. In the case of a hotplate or hotplate, this massive insulation is used instead of the insulation layer described above. Aluminum nitride (AlN), for example, is used as the insulation material. This insulating body separates the supporting heating element from the medium or object to be heated.
In einer weiteren Ausführungsform verbindet ein derartiger Isolationskörper mehrere massive Heizelemente miteinander, die somit eine gemeinsame Heizeinheit bilden.In a further embodiment, such an insulation body connects several solid heating elements to one another, which thus form a common heating unit.
Damit die erfindungsgemässe Heizeinheit sinnvoll eingesetzt werden kann, muss für jedes Anwendungsbeispiel jeweils die Optimierung aller wesentlichen Parameter berechnet werden. Das heisst, die Länge und Querschnittsfläche des Widerstands¬ heizelementes müssen so gewählt werden, dass der resultie¬ rende Widerstand R die zur Erzielung der gewünschten Tempera¬ tur notwendige Grosse aufweist. Gleichzeitig muss aber die Forderung erfüllt werden, dass die Stabilität des Körpers zum Führen des Mediums oder Tragen des Gegenstandes ausreicht. Ein dabei teilweise frei wählbarer Parameter ist das Mate¬ rial. Der spezifische Widerstand lässt sich durch Veränderung der Dotierung des Siliziumkarbits oder des Kunststoffes variieren.In order that the heating unit according to the invention can be used sensibly, the optimization of all essential parameters must be calculated for each application example. This means that the length and cross-sectional area of the resistance heating element must be selected so that the resulting resistance R has the size necessary to achieve the desired temperature. At the same time, however, the requirement must be met that the stability of the body is sufficient to carry the medium or carry the object. The material is a freely selectable parameter in some cases. The specific resistance can be changed the doping of the silicon carbide or the plastic vary.
Im folgenden werden einige Zahlenbeispiele typischer Ausführungsformen angegeben:Some numerical examples of typical embodiments are given below:
1. Beispiel;1st example;
- verwendetes Material : graphitgefüllter Hochleistungs - kunststoff mit einem spezifischen Widerstand von p = 4 Ωcm.- Material used: graphite-filled high-performance plastic with a specific resistance of p = 4 Ωcm.
Abmessungen des Rohres Durchmesser: 40 mm Wandstärke: 2.5 mm Länge: 200 mm angelegte Spannung: 220 V , 50 Hz Leistung: 1.78 kWDimensions of the tube diameter: 40 mm wall thickness: 2.5 mm length: 200 mm applied voltage: 220 V, 50 Hz power: 1.78 kW
2. Beispiel:2nd example:
- verwendetes Material : Hochleistungskunststoff mit einem spezifischen Widerstand von p = 0.04 Ωcm- Material used: high-performance plastic with a specific resistance of p = 0.04 Ωcm
Abmessungen des Rohres siehe Beispiel 1 angelegte Spannung: 24 V Leistung: 2.12 kWDimensions of the tube see example 1 applied voltage: 24 V power: 2.12 kW
3. Beispiel:3rd example:
- verwendetes Material : Hochleistungskunststoff mit einem spezifischen Widerstand von p = 40 Ωcm - Abmessungen des Rohres: siehe Beispiel 1- Material used: high-performance plastic with a specific resistance of p = 40 Ωcm - Dimensions of the pipe: see example 1
- angelegte Spannung: 380 V- applied voltage: 380 V.
- Leistung: 532 W- Power: 532 W.
4. Beispiel :4. Example:
- verwendetes Material .- Siliziumkarbit mit einem spezifi¬ schen Widerstand von p = 1.3 Ωcm- Material used .- Silicon carbite with a specific resistance of p = 1.3 Ωcm
- Abmessungen des Stabes Durchmesser: 8 mm Länge: 150 mm- Dimensions of the rod diameter: 8 mm length: 150 mm
- angelegte Spannung: 220 V, 50 Hz- applied voltage: 220 V, 50 Hz
- Leistung. - 1.25 kW - Power. - 1.25 kW

Claims

Patentansprüche claims
1. Elektrische Heizeinheit mit einem stromdurchflossenen Widerstandsheizelement und einem, den zu heizenden Gegen¬ stand oder das zu erwärmende Medium tragenden beziehungs¬ weise oder führenden, massiven Körper, dadurch gekenn¬ zeichnet, dass der tragende, beziehungsweise führende massive Körper gleichzeitig das stromdurchflossene Wider¬ standsheizelement bildet.1. Electric heating unit with a current-carrying resistance heating element and a solid body carrying or to be heated or carrying the medium or medium to be heated, characterized in that the carrying or leading solid body simultaneously carries the current-carrying resistor parking heater forms.
2. Elektrische Heizeinheit nach Anspruch 1, dadurch gekenn¬ zeichnet, dass der stromdurchflossene, massive Körper aus einem halbleitenden Material hergestellt ist, dessen spezifischer elektrischer Widerstand 10~4 Ωm bis 1 Ωm beträgt.2. Electric heating unit according to claim 1, characterized gekenn¬ characterized in that the current-carrying, solid body is made of a semiconducting material whose specific electrical resistance is 10 ~ 4 Ωm to 1 Ωm.
3. Elektrische Heizeinheit nach Anspruch 2, dadurch gekenn¬ zeichnet, dass der massive Körper aus Siliziumkarbit gefertigt ist.3. Electric heating unit according to claim 2, characterized gekenn¬ characterized in that the solid body is made of silicon carbide.
4. Elektrische Heizeinheit nach Anspruch 2, dadurch gekenn¬ zeichnet, dass der massive Körper aus einem mit Kohlen¬ stoff, Graphit oder Metall dotierten Hochleistungs-Kunst¬ stoff gefertigt ist.4. Electrical heating unit according to claim 2, characterized gekenn¬ characterized in that the solid body is made of a high-performance plastic doped with carbon, graphite or metal.
5. Elektrische Heizeinheit nach Anspruch 1, dadurch gekenn¬ zeichnet, dass der massive Körper die Form eines Rohres hat. 5. Electric heating unit according to claim 1, characterized gekenn¬ characterized in that the solid body has the shape of a tube.
6. Elektrische Heizeinheit nach Anspruch 5, dadurch gekenn¬ zeichnet, dass das Rohr einen thermisch isolierten Mantel aufweist.6. Electric heating unit according to claim 5, characterized gekenn¬ characterized in that the tube has a thermally insulated jacket.
7. Elektrische Heizeinheit nach Anspruch 1, dadurch gekenn¬ zeichnet, dass das Heizelement mindestens teilweise mit einer elektrisch isolierenden, gut wärmeleitenden Schicht oder einem Isolationskörper bedeckt ist.7. Electrical heating unit according to claim 1, characterized gekenn¬ characterized in that the heating element is at least partially covered with an electrically insulating, good heat-conducting layer or an insulating body.
8. Elektrische Heizeinheit nach einem der Ansprüche 1 oder 7, dadurch gekennzeichnet, dass das Heizelement aus einer Platte besteht.8. Electric heating unit according to one of claims 1 or 7, characterized in that the heating element consists of a plate.
9. Elektrische Heizeinheit nach Anspruch 7, dadurch gekenn¬ zeichnet, dass sie eine Kochplatte ist.9. Electric heating unit according to claim 7, characterized gekenn¬ characterized in that it is a hotplate.
10. Elektrische Heizeinheit nach Anspruch 7, dadurch gekenn¬ zeichnet, dass sie eine Kochplatte ist. 10. Electric heating unit according to claim 7, characterized gekenn¬ characterized in that it is a hotplate.
PCT/CH1994/000143 1993-07-12 1994-07-08 Electric heating unit WO1995002952A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
AU70670/94A AU7067094A (en) 1993-07-12 1994-07-08 Electric heating unit
EP94919544A EP0659328A1 (en) 1993-07-12 1994-07-08 Electric heating unit
PL94308110A PL308110A1 (en) 1993-07-12 1994-07-08 Electric heating system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH208393A CH688328A5 (en) 1993-07-12 1993-07-12 Electrical heating.
CH2083/93-2 1993-07-12

Publications (2)

Publication Number Publication Date
WO1995002952A1 true WO1995002952A1 (en) 1995-01-26
WO1995002952B1 WO1995002952B1 (en) 1995-02-16

Family

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Family Applications (1)

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PCT/CH1994/000143 WO1995002952A1 (en) 1993-07-12 1994-07-08 Electric heating unit

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EP (1) EP0659328A1 (en)
AU (1) AU7067094A (en)
CH (1) CH688328A5 (en)
CZ (1) CZ283545B6 (en)
HU (1) HUT71146A (en)
PL (1) PL308110A1 (en)
WO (1) WO1995002952A1 (en)

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Publication number Priority date Publication date Assignee Title
CN100379318C (en) * 2003-05-26 2008-04-02 住友电气工业株式会社 Baking method
EP2073600A1 (en) 2007-12-21 2009-06-24 Tadeusz Tatarzynski Collective heating unit, especially for electric heater

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US2371275A (en) * 1945-03-13 heating element
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FR2197295A1 (en) * 1972-08-25 1974-03-22 Bailey Barbara
DE2347766A1 (en) * 1972-09-22 1974-03-28 Inventum Koninklijke Fab HEATING ELEMENT
US4384192A (en) * 1981-03-02 1983-05-17 Teledyne Still-Man Manufacturing Electric heating element
WO1991001617A1 (en) * 1989-07-18 1991-02-07 Matsusita Electric Works, Ltd. Heat generating member

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Publication number Priority date Publication date Assignee Title
US2371275A (en) * 1945-03-13 heating element
CH138805A (en) * 1926-04-28 1930-03-31 Max Dr Hauser Electrical resistance body and method of making the same.
DE1239416B (en) * 1960-04-26 1967-04-27 Siemens Electrogeraete Ges Mit Electric instantaneous water heater with ceramic heating resistor
US3309643A (en) * 1964-01-02 1967-03-14 Massachusetts Inst Technology Electric heating element
DE2049977A1 (en) * 1970-10-12 1972-04-20 Danfoss As High temp electrical resistance - based on aluminium oxycarbide for stability and thermal shock resistance
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100379318C (en) * 2003-05-26 2008-04-02 住友电气工业株式会社 Baking method
EP2073600A1 (en) 2007-12-21 2009-06-24 Tadeusz Tatarzynski Collective heating unit, especially for electric heater

Also Published As

Publication number Publication date
HU9500746D0 (en) 1995-05-29
PL308110A1 (en) 1995-07-24
AU7067094A (en) 1995-02-13
CH688328A5 (en) 1997-07-31
CZ283545B6 (en) 1998-04-15
EP0659328A1 (en) 1995-06-28
CZ63095A3 (en) 1995-08-16
HUT71146A (en) 1995-11-28

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