Field of the Disclosure
The configurations described herein relate to a smart susceptor radiant heater. The smart susceptor radiant heater may include a high emissivity coating and induction coils. The smart susceptor radiant heater may be an air heater for drying or convection heating.
Description of the Related Art
Induction heating systems have been used to provide heat for processes such as fabricating parts or components. Induction heating systems typically include a susceptor (an electrically conducting material which can be ferromagnetic) that responds to electromagnetic flux generated by an energized induction coil by generating heat within the electrically conducting/ferromagnetic material. Heat is typically conducted from the electrically conducting/ferromagnetic element, hereinafter referred to as a ferromagnetic element, directly to the parts or components. Induction heating systems may also provide a heating element with a fairly stable temperature that may be preferred to heat certain objects, such as thin films, by radiation rather than by conduction which is the typical heat transfer mechanism utilized by typical induction heating systems.
Conventional heating equipment for the non-contact heating of objects such as films and coatings may not provide reliable uniform heat to heat the object. Conventional infrared or radiant heaters may not provide reliable uniform heating, which can result in overheating or under heating of the article being heated. Further, lack of spatial uniformity in conventional non-contact heating equipment may result in portions of an article being heated to different temperatures.
It may be beneficial to provide a radiant heater having a ferromagnetic element including a high emissivity surface.
One configuration of a radiant heater includes a susceptor including a ferromagnetic element having a high-emissivity surface and an induction coil operatively coupled with the ferromagnetic element, wherein an application of electrical power to the induction coil generates eddy currents in the susceptor that heat the susceptor. The high-emissivity surface may comprise a coating on the surface of the susceptor. The coating may comprise black paint or a film that includes carbon black. The high-emissivity surface may comprise a micro-textured surface.
The ferromagnetic element of the radiant heater may be a sheet, a film, a wire, a composite, or combinations of these elements. The high-emissivity surface of the radiant heater may have an emissivity higher than 0.8. The high-emissivity surface of the radiant heater may have an emissivity higher than 0.9. The radiant heater may include at least one aperture through the susceptor. The radiant heater may include a feedback mechanism configured to reduce the application of power to the induction coiled when the entire susceptor is heated to a predetermined temperature. The predetermined temperature may be the Curie temperature of the ferromagnetic element of the radiant heater. The feedback mechanism of the radiant heater may monitor trends in electrical power applied to the induction coil. The ferromagnetic element of the radiant heater may be positioned within a matrix.
One configuration of a system for heating an object comprises a first susceptor including a ferromagnetic element having a high-emissivity surface, the first susceptor having a first Curie temperature, a first induction coil operatively coupled with the ferromagnetic element, and a first power source in electrical communication with the first induction coil, wherein application of power to the induction coil heats the first susceptor. The system may include an object positioned adjacent to the first susceptor, wherein a distance separates the object and the first susceptor. The system may include a roller. The object to be heated may be a thin film.
The system may include a second susceptor including a ferromagnetic element having a high-emissivity surface, the second susceptor having a second Curie temperature that differs from the first Curie temperature, a second induction coil operatively coupled with the ferromagnetic element, and a second power source in electrical communication with the second induction coil, wherein application of power in the second induction coil heats the second susceptor. The system may also include a third susceptor including a ferromagnetic element having a high-emissivity surface, the third susceptor having a third Curie temperature that differs from the first Curie temperature and the second Curie temperature, a third induction coil operatively coupled with the ferromagnetic element, and a third power source in electrical communication with the third induction coil, wherein application of power in the third induction coil heats the third susceptor.
A method of heating an object with a radiant heater comprises energizing an induction coil operatively coupled with a ferromagnetic element that includes an emissive surface, the ferromagnetic element having a Curie temperature and generating eddy currents within the ferromagnetic element until the ferromagnetic element is heated to the Curie temperature. The method further comprises positioning the object a selected distance from the emissive surface, such that the object and the emissive surface are thermally coupled but not in contact with each other and radiating heat that is substantially uniformly distributed from the emissive surface to the object. The emissive surface may be a high emissivity surface.
The method may include moving the object with respect to the ferromagnetic element. The method may include monitoring power provided to energize the induction coil to determine when the ferromagnetic element has been heated to the Curie temperature. The method may include energizing a second induction coil operatively coupled with a second ferromagnetic element that includes a second high emissivity surface, the second ferromagnetic element having a Curie temperature, wherein the Curie temperature of the second ferromagnetic element differs from the Curie Temperature of the ferromagnetic element, generating eddy currents within the second ferromagnetic element until the second ferromagnetic element is heated to the Curie temperature, and radiating uniformly distributed heat from the second high emissivity surface, wherein the second high emissivity surface and the object are thermally coupled.
While the disclosure is susceptible to various modifications and alternative forms, specific configurations have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the scope of the disclosure as defined by the appended claims.
The smart susceptor radiant heater 100 includes an induction coil 10 connected to a power supply (shown in
The ferromagnetic element 20 of the smart susceptor radiant heater 100 may be adapted to have a desired Curie temperature as would be appreciated by one of ordinary skill in the art. Thus, the smart susceptor radiant heater 100 may be used to carefully control the heating of a temperature sensitive element, such as a thin film, coating, biological cell growth, electronic component, or to achieve controlled chemical reactions or crystal growth. The smart susceptor radiant heater 100 includes a high emissivity surface 30 adjacent to the object 40 that is to be heated via radiation from the smart susceptor radiant heater 100. Emissivity is the relative ability of the surface to emit energy by radiation. A high emissivity surface is defined herein as a surface that has an emissivity of 0.7 or greater. This emissivity is an integrated property over the blackbody spectrum for an object of the desired/specified heating temperature.
The high emissivity surface 30 of the smart susceptor radiant heater 100 permits the heater 100 to more efficiently radiate energy to heat the object 40. The high emissivity surface 30 may be a paint that is highly absorptive of thermal radiation at the desired heating temperature applied to the surface of the smart susceptor radiant heater 100 that is adjacent to the object 40 that is to be heated by the heater 100. The high emissivity surface 30 may be a matte or otherwise textured surface to mitigate interaction with the external environment. The high emissivity surface 30 may be a very thin coating on the surface of the heater 100 that is adjacent to the object being heated. For example, the high emissivity surface 30 may only be a few microns thick. The high emissivity surface 30 may be any surface and/or coating that has a 0.7 or greater emissivity. The high emissivity surface 30 may have an emissivity of approximately 0.8 or higher. The high emissivity surface 30 may have an emissivity of approximately 0.9 or higher. The high emissivity surface 30 may be a polymer film containing carbon black. The high emissivity surface 30 may be a metal with a highly textured surface. The high emissivity surface may be a microstructured surface created from a material that itself may or may not have high emissivity, e.g. m micro-textured metal surface. A surface with emissivity of less than 0.7 will require a substantially longer heating time (for a non-moving object) or a substantially longer heater (for a moving object).
The object 40 to be heated may be moved along a path adjacent to the high emissivity surface 30 of the radiant heater 100. For example, rollers 50 may move a plurality of films adjacent the radiant heater 100 to be heated. A plurality of rollers 50 of various configurations could be used in combination with a radiant heater 100 to heat and/or cure an object. The heating of the plurality of films may laminate the films together. The radiant heater 100 may also be moved along an object, such as a coating, to heat, dry, and/or cure the object. For example, the radiant heater 100 may be mounted on a device, such as a robot, that is configured to move the radiant heater 100 along a path adjacent to the object to be heated, dried, and/or cured.
A power supply 260 providing alternating current electric power may be connected to the induction coil 210 of the radiant heater 200 by wiring 265. The power supply 260 may be configured as a portable or fixed power supply which may be connected to a convention 60 Hz, 110 volt or 220 volt outlet. The frequency of the alternating current that is provided to the induction coil 210 may preferably range from approximately 1000 Hz to approximately 300,000 Hz. The voltage provided to the induction coil 210 may range from approximately 10 volts to approximately 300 volts. The alternating current provided to the induction coil 210 may range from approximately 10 amps to approximately 1000 amps. The power supply 260 may be provided in a constant-current configuration wherein the voltage across the induction coil 210 may decrease as the ferromagnetic material 220 approaches the Curie temperature.
The radiant heater 200 may include a feedback mechanism, such as thermal sensors, thermocouples, or other suitable temperature sensing devices, for monitoring heat along the high emissivity surface 230 of the radiant heater 200 in combination with a controller 280 to dynamically control the power supplied by a power supply 260. The radiant heater 200 may include a sensor 270 connected to the power supply 260. The sensor 270 may monitor the voltage or the current provided by the power supply 260. As discussed above, the power supply 260 may be provided as a constant current configuration to minimize unwanted resistive heating in the inductor coil 210. The sensor 270 may monitor changes in voltage, current, and/or power to determine when the ferromagnetic element 220 of the heater 200 has reached the Curie temperature.
The sensor 270 may be configured to indicate the voltage provided by the power supply 260. For a constant current configuration of the radiant heater 200, the voltage may decrease as the ferromagnetic element 220 approaches the Curie temperature. The power supply 260 may be configured to facilitate adjustment of the frequency of the alternating current in order to alter the heating rate of the magnetic material. The power supply 260 may be coupled with a controller 280 to facilitate adjustment of the alternating current over a predetermined range in order to facilitate the application of the radiant heater to a wide variety of objects having different heating requirements.
The power supply 260 may be configured to supply constant power permitting the current and voltage to change at a predetermined ratio while the wires 220 heat up to the Curie temperature. The sensor 270 can detect and indicate when the radiant heater 200 has reached the Curie temperature by detecting when the load from the induction coil 210 stops changing. When the radiant heater 200 reaches or approaches the Curie temperature, the power needed to drive the current through the wires 220 decreases substantially so that the only power costs is the power needed to heat the object coupled with the radiant heater 200. If the object being heated is already at the Curie temperature, then the object and the radiant heater 200 are emitting the same heat to each other (i.e. the two are thermally coupled in equilibrium) and the only power needed is the power required to offset any heat loss to the surrounding equipment. The thermally insulating structure 235 may help to minimize the heat lost from the radiant heater 200.
As discussed above, the ferromagnetic material 20, 220 becomes substantially non-magnetic when it reaches the Curie temperature. As the shown in
The method 400 may include a step 450 of moving the object with respect to the ferromagnetic element and also may include a step 460 of monitoring power provided to energize the induction coil to determine when the ferromagnetic element has been heated to the Curie temperature. The method 400 may also include a step 470 of energizing a second induction coil operatively coupled with a second ferromagnetic element that includes a second high emissivity surface. The second ferromagnetic element may have a Curie temperature that differs from the Curie temperature of the first ferromagnetic element energized in step 410. The method 400 may also include a step 480 of generating eddy currents within the second ferromagnetic element until the second ferromagnetic element is heated to the Curie temperature and may also include a step 490 of radiating uniformly distributed heat from the second high emissivity surface, wherein the second high emissivity surface and the object are thermally coupled.
Referring to
Each of the processes of method 300 may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include without limitation any number of aircraft manufacturers and major-system subcontractors; a third party may include without limitation any number of vendors, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on.
As shown in
Apparatus and methods embodied herein may be employed during any one or more of the stages of the production and service method 300. For example, components or subassemblies corresponding to production process 308 may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft 302 is in service 314. Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during the production stages 308 and 310, for example, by substantially expediting assembly of or reducing the cost of an aircraft 302. Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft 302 is in service 314, for example and without limitation, to maintenance and service 316.
Although this disclosure has been described in terms of certain preferred configurations, other configurations that are apparent to those of ordinary skill in the art, including configurations that do not provide all of the features and advantages set forth herein, are also within the scope of this disclosure. Accordingly, the scope of the present disclosure is defined only by reference to the appended claims and equivalents thereof.
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