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)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (2)

Family

ID=4225513

Family Applications (1)

Country Status (7)

Cited By (2)

Citations (10)

• 1993
  • 1993-07-12 CH CH208393A patent/CH688328A5/de not_active IP Right Cessation
• 1994
  • 1994-07-08 AU AU70670/94A patent/AU7067094A/en not_active Abandoned
  • 1994-07-08 PL PL94308110A patent/PL308110A1/xx unknown
  • 1994-07-08 WO PCT/CH1994/000143 patent/WO1995002952A1/de not_active Application Discontinuation
  • 1994-07-08 CZ CZ95630A patent/CZ283545B6/cs not_active IP Right Cessation
  • 1994-07-08 EP EP94919544A patent/EP0659328A1/de not_active Withdrawn
  • 1994-07-08 HU HU9500746A patent/HUT71146A/hu unknown

Patent Citations (10)

Also Published As

Similar Documents

Legal Events