EP1203511A1 - Infrared heater with electromagnetic induction - Google Patents
Infrared heater with electromagnetic inductionInfo
- Publication number
- EP1203511A1 EP1203511A1 EP00938420A EP00938420A EP1203511A1 EP 1203511 A1 EP1203511 A1 EP 1203511A1 EP 00938420 A EP00938420 A EP 00938420A EP 00938420 A EP00938420 A EP 00938420A EP 1203511 A1 EP1203511 A1 EP 1203511A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- transmitter according
- infrared
- plate
- induction
- inductor
- Prior art date
- Legal status (The legal status 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 status listed.)
- Granted
Links
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
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/02—Induction heating
- H05B6/10—Induction heating apparatus, other than furnaces, for specific applications
- H05B6/105—Induction heating apparatus, other than furnaces, for specific applications using a susceptor
-
- 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
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/02—Induction heating
- H05B6/10—Induction heating apparatus, other than furnaces, for specific applications
- H05B6/105—Induction heating apparatus, other than furnaces, for specific applications using a susceptor
- H05B6/106—Induction heating apparatus, other than furnaces, for specific applications using a susceptor in the form of fillings
Definitions
- the invention relates to an electromagnetic induction infrared transmitter. More particularly, the invention relates to a device allowing the emission of infrared radiation, which device is supplied with electricity by means of an inductor, and characterized by a choice of material for the transmitter which makes it possible to support high temperatures and achieve high densities of medium-type radiation power.
- the emission temperature of gas radiant heaters is between 900 and 1150 ° C: the radiation is therefore of the "medium” type, that is to say in the wavelengths identified with medium infrared (more than 85% of the radiated power between 1 and 6 m). They offer radiation power densities of 100 to 160 kW / m 2 . Electric lamp transmitters (whose filament is brought to 2200 ° C) radiate more in the short type infrared (more than 85% of the radiated power between 0 and 2.5 m), and offer power densities that can exceed 300 kW / m 2 .
- the present medium-type infrared electrical technology is limited in power density and the object of the present invention is therefore to overcome these limitations.
- an infrared source consists of a solid body which is brought to a temperature such that it emits electromagnetic radiation of the infrared type.
- Electric infrared emitters involve the passage of a direct current through a resistor, usually a wire. Heating is therefore carried out by the Joule effect (direct electrical conduction).
- the power density of a transmitter made of a metal wire is limited for several reasons.
- the metal wires have a low electrical resistivity and cannot exceed a temperature of 1300 ° C.
- To obtain an adequate resistance ie sufficiently high to imply reasonable currents, it is necessary to decrease the diameter or increase the length of the wire.
- the lifetime decreases sharply with the diameter of the wire: it is therefore preferable to increase the length of the wire, which is achieved by shaping a sausage.
- a certain distance between turns of the same tube and between the rows of tubes must be respected under penalty of producing hot spots. This requirement again limits the power density.
- the tubes In addition, it is often imperative to cover the tubes with a material isolating them from the environment, both from a thermal point of view (in order to limit losses by convection to ambient air) and electrically (for reasons of security).
- the extruded wires are then embedded or inserted in a material which may or may not be transparent to infrared radiation. In the case of an infrared opaque material, the heat must be transmitted from the internal metal wire to the external envelope by direct conduction. It is then this envelope which emits infrared radiation and it is necessarily maintained at a lower temperature than the internal wire itself.
- tubular heaters In the case of radiant tubes (“tubular heaters"), an electrically non-conductive material (usually an oxide) must be inserted between the resistance and the envelope, which limits the heat transfer and creates a strong gradient of temperature. The power density is therefore more limited than for a naked rod.
- infrared sources When a material transparent to infrared radiation (usually quartz) is used to contain the tube, the radiation comes from the tube itself but passes directly through the quartz. The metal tube is then protected from the movement of the surrounding air: convection losses are therefore reduced.
- the power density of infrared sources with extruded wires embedded in plates or inserted in quartz tubes is the highest among medium-type electric infrared sources but remains below 100 kW / m 2 , providing less than 80 kW / m 2 in radiation.
- sources with short infrared lamps are characterized by a very high power density, because the tungsten wire 6
- the interior of the lamps is brought to a very high temperature (2200 ° C): but as we have seen, this temperature level implies that the emission is rather of the short type, which brings about the disadvantages already mentioned.
- the tungsten wire must be enclosed in a sealed tube to prevent rapid oxidation.
- Another way to increase the power density is to enlarge the actual transmission area by using an extended area and no longer a stranded wire.
- a full and extended plate configuration increases the transmission surface. Theoretically, if we managed to heat a solid surface of Kanthal Al to 1300 ° C in a relatively uniform manner, the radiation power density would be very high (above 300 kW / m 2 ). The difficulty is to pass the current everywhere in this surface. In direct conduction, it is very difficult to achieve uniform heating, because the current flows through the shortest "electric" path. To pass the current everywhere between the voltage terminals, it is necessary to cut several lines in the plate, which poses problems of mechanical strength and local current concentration. Certain means have been evaluated and tested by the applicant, but several problems have led to questioning the use of direct electrical conduction: uniformity of heating, supply voltage, thermal expansion, mechanical solidity, thermal losses through the contacts, and other. 7
- the plaintiff has considered using electromagnetic induction: rather than passing the current directly through a resistor, the heating can then be carried out by eddy currents induced by a conductor physically decoupled from the heated material.
- the material in which these currents are developed may be other than the metal constituting the stranded wire of conventional infrared sources.
- induction rather than direct conduction therefore makes it possible to resolve many technical problems.
- the choice of the material constituting the emitting surface constitutes the determining aspect. This material must be able to withstand very high temperatures, well beyond the Curie point of all materials with magnetic properties. Only the resistivity therefore intervenes on the electromagnetic plane.
- the Applicant has been able to identify a range of resistivity of materials and supply frequencies resulting in an excellent electrical efficiency and a relatively good power factor, two conditions so that the induction can be used as a heating means at the base of an infrared system. It is possible to transfer a very high power (beyond 50 kW for a 0.16 m 2 plate) by generating a typical electric field, at a reasonable supply voltage.
- the heating is relatively uniform, although the currents generated in the hot plate are an image of the configuration of the inductor, which is in circular shape ("pancake"): the four corners of the plate are therefore cooler, thus than the center.
- pancake the four corners of the plate are therefore cooler, thus than the center.
- the material constituting the emitting surface must be able to withstand very high temperatures and thermomechanical stresses.
- the metals constituting the resistive wires of infrared sources are 8
- CMC Ceramic Matrix Composite
- CFRC Continuous Fiber Ceramic Composites
- CFCCs are therefore a solution to the traditional problem of ceramic fragility. They can operate at high temperature, undergo thermal shocks, and have a long service life. These advantages make them ideal candidates to serve as the basis of a high power density infrared system. On the other hand, most CFCCs do not conduct electricity, and are therefore not likely to be heated by electromagnetic induction. The Applicant has found that CFCCs comprising carbon fibers (C / SiC) conduct electricity enough to be efficiently heated by electromagnetic induction.
- the object of the invention is to produce a radiant surface simply made of an appropriate material, of an appropriate size and shape, and the electrical, mechanical and thermal characteristics of which are suitably chosen.
- Another object of the invention is to use induction, which makes it possible to use non-metallic materials and to obtain good electrical efficiency.
- the object of the invention is also to reach a limit temperature higher than that of the metals based on Fe - Cr - A, which is 1300 ° C, and even to go beyond 1400 ° C.
- Another object of the invention is to use a composite material having a relatively low electrical resistivity, in order to respond to induction heating. Another object of the invention is to achieve power densities of more than 200 kW / m 2 in medium infrared using a transmitter according to the invention.
- Another object of the invention is to use a material that responds to electromagnetic induction and is capable of supporting the operating conditions mentioned, in particular in order to respond to induction heating.
- Another object of the invention is to propose as emitter material, composite ceramics which do not suffer from the disadvantages of ceramics of the monolithic type.
- an infrared emitter comprising a surface made of a material which responds to induction and capable of withstanding high temperatures, at least an insulating thickness of very low. thermal conductivity attached to said surface, an inductor adjacent to the thicknesses insulation and separated from said surface by the latter, as well as a field concentrator adjacent to the inductor.
- the material responding to induction can for example consist of a matrix allowing induction heating and comprising carbon fibers.
- the surface responding to the induction is in the form of a plate, which can be chosen from composite materials, in particular of the CFCC and carbon / carbon type.
- the surface responding to the induction can be a thin layer attached to a plate.
- the surface must be capable of being brought to a temperature of at least 1300 ° C., and of generating a radiation power density exceeding 250 kW / m 2 .
- the insulator consists of a thickness of a low temperature insulator and a thickness of a high temperature insulator.
- the inductor can include an inductor made of a water-cooled copper tube, or can also include Litz cables.
- the field concentrator is juxtaposed with the inductor.
- the plate has a thickness lying between approximately 1 mm and 5 mm.
- FIG. 1 is a plan view of an infrared induction transmitter, according to the invention
- FIG. 2 is a section taken along A '- A "of Figure 1.
- a field concentrator 1 is juxtaposed with the spiral tubing ( Figure 1).
- the infrared emitter is placed to transmit radiation on a sheet of paper 6.
- a CFCC comprising carbon fibers makes it possible to obtain an extended plate at high temperature producing medium-type infrared radiation at a high power density.
- Tests have shown that carbon fibers, which are within a matrix of silicon carbide, allow induction heating at frequencies of a few tens of kilohertz. Simulation tests and tests on a prototype have shown that it would be possible to transfer power with very good electrical efficiency. Thermomechanically, it has been possible to see that this composite has excellent properties.
- a plate manufactured in CFCC from the company AlliedSignal Composites had perfect flatness and a good appearance of uniformity. Induction heating of a very demanding nature did not lead to any breakage, deformation or reduction in mechanical rigidity. The electromagnetic coupling was also confirmed excellent. 13
- the invention consists in heating a plate of a specific material by electromagnetic induction, which plate is brought to high temperature and, consequently, emits infrared radiation.
- the main temperature of the plate is around 1300 ° C, which makes it a medium infrared type source, therefore suitable for coating drying on paper.
- the radiation power density exceeds 250 kW / m 2 , which would more than double the radiation power density of most current gas radiant heaters. This very high power density constitutes the essential advantage of such a system. This translates into an occupied area reduced by half for the same installed power.
- the concept is characterized by a very small vertical footprint compared to current gas and electrical technologies: this is due to the absence of combustion air and gas supply lines (with reference to gas radiant heaters) or cooling air for the connectors (with reference to short infrared lamp technology).
- the new concept therefore makes it possible to reduce the space occupied both horizontally and vertically.
- the reduced vertical footprint can allow IRHD / induction sources to be placed on either side of the sheet of paper, which would further increase the power density.
- IRHD technology could also find very interesting applications in the field of metallurgy and glass.
- the high temperature furnaces currently heated by radiating tubes could advantageously be replaced by plates heated by induction. These plates would then line the internal walls of the oven and allow a very high heating capacity, and therefore production.
Abstract
Description
Claims
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA2277885 | 1999-07-16 | ||
CA002277885A CA2277885C (en) | 1999-07-16 | 1999-07-16 | Electromagnetic induction infrared heat system |
PCT/CA2000/000722 WO2001006814A1 (en) | 1999-07-16 | 2000-06-15 | Infrared heater with electromagnetic induction |
Publications (2)
Publication Number | Publication Date |
---|---|
EP1203511A1 true EP1203511A1 (en) | 2002-05-08 |
EP1203511B1 EP1203511B1 (en) | 2006-02-22 |
Family
ID=4163791
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP00938420A Expired - Lifetime EP1203511B1 (en) | 1999-07-16 | 2000-06-15 | Infrared heater with electromagnetic induction and its uses |
Country Status (7)
Country | Link |
---|---|
US (1) | US6858823B1 (en) |
EP (1) | EP1203511B1 (en) |
AU (1) | AU5383000A (en) |
CA (1) | CA2277885C (en) |
DE (1) | DE60026139T2 (en) |
NO (1) | NO20021642L (en) |
WO (1) | WO2001006814A1 (en) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20070210056A1 (en) * | 2005-11-16 | 2007-09-13 | Redi-Kwick Corp. | Infrared oven |
FR2906786B1 (en) * | 2006-10-09 | 2009-11-27 | Eurocopter France | METHOD AND DEVICE FOR DEFROSTING AN AIRCRAFT WALL |
US8043375B2 (en) * | 2008-03-06 | 2011-10-25 | MoiRai Orthopaedic, LLC | Cartilage implants |
EP2893854B1 (en) * | 2014-01-10 | 2016-11-30 | Electrolux Appliances Aktiebolag | Induction cooker |
EP3758445B1 (en) * | 2018-02-23 | 2023-09-06 | TMT Machinery, Inc. | Heating roller and spun yarn drawing device |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
BE497198A (en) | ||||
US2635168A (en) | 1950-11-04 | 1953-04-14 | Pakco Company | Eddy current heater |
US5227597A (en) * | 1990-02-16 | 1993-07-13 | Electric Power Research Institute | Rapid heating, uniform, highly efficient griddle |
US5240542A (en) * | 1990-09-06 | 1993-08-31 | The Board Of Trustees Of The Leland Stanford Junior University | Joining of composite materials by induction heating |
US5528020A (en) * | 1991-10-23 | 1996-06-18 | Gas Research Institute | Dual surface heaters |
-
1999
- 1999-07-16 CA CA002277885A patent/CA2277885C/en not_active Expired - Lifetime
-
2000
- 2000-06-15 DE DE60026139T patent/DE60026139T2/en not_active Expired - Lifetime
- 2000-06-15 WO PCT/CA2000/000722 patent/WO2001006814A1/en active IP Right Grant
- 2000-06-15 EP EP00938420A patent/EP1203511B1/en not_active Expired - Lifetime
- 2000-06-15 AU AU53830/00A patent/AU5383000A/en not_active Abandoned
- 2000-06-15 US US10/030,990 patent/US6858823B1/en not_active Expired - Lifetime
-
2002
- 2002-04-05 NO NO20021642A patent/NO20021642L/en unknown
Non-Patent Citations (1)
Title |
---|
See references of WO0106814A1 * |
Also Published As
Publication number | Publication date |
---|---|
WO2001006814A1 (en) | 2001-01-25 |
NO20021642D0 (en) | 2002-04-05 |
DE60026139D1 (en) | 2006-04-27 |
CA2277885A1 (en) | 2001-01-16 |
US6858823B1 (en) | 2005-02-22 |
EP1203511B1 (en) | 2006-02-22 |
NO20021642L (en) | 2002-04-05 |
CA2277885C (en) | 2007-05-22 |
DE60026139T2 (en) | 2006-11-23 |
AU5383000A (en) | 2001-02-05 |
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