EP1521501A1 - Mikrowellenheizvorrichtung - Google Patents

Mikrowellenheizvorrichtung Download PDF

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Publication number
EP1521501A1
EP1521501A1 EP03102665A EP03102665A EP1521501A1 EP 1521501 A1 EP1521501 A1 EP 1521501A1 EP 03102665 A EP03102665 A EP 03102665A EP 03102665 A EP03102665 A EP 03102665A EP 1521501 A1 EP1521501 A1 EP 1521501A1
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EP
European Patent Office
Prior art keywords
heating device
microwave heating
cavity
load
microwave
Prior art date
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Withdrawn
Application number
EP03102665A
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English (en)
French (fr)
Inventor
Per Olov G Risman
Magnus Fagrell
Fredrik Stillesjö
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Personal Chemistry i Uppsala AB
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Personal Chemistry i Uppsala AB
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Publication date
Application filed by Personal Chemistry i Uppsala AB filed Critical Personal Chemistry i Uppsala AB
Priority to EP03102665A priority Critical patent/EP1521501A1/de
Priority to AU2004241919A priority patent/AU2004241919B2/en
Priority to JP2006532173A priority patent/JP4299862B2/ja
Priority to CA002526474A priority patent/CA2526474A1/en
Priority to RU2005139728/09A priority patent/RU2324305C2/ru
Priority to PCT/SE2004/000669 priority patent/WO2004105443A1/en
Priority to EP04730780A priority patent/EP1625775A1/de
Priority to US10/556,505 priority patent/US7528353B2/en
Publication of EP1521501A1 publication Critical patent/EP1521501A1/de
Withdrawn legal-status Critical Current

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    • 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
    • H05B6/64—Heating using microwaves
    • H05B6/80—Apparatus for specific applications
    • H05B6/806—Apparatus for specific applications for laboratory use
    • 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
    • H05B6/64—Heating using microwaves
    • H05B6/6402—Aspects relating to the microwave cavity
    • 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
    • H05B6/64—Heating using microwaves
    • H05B6/70—Feed lines
    • H05B6/707—Feed lines using waveguides
    • H05B6/708—Feed lines using waveguides in particular slotted waveguides

Definitions

  • the present invention relates to a microwave heating device, a microwave heating system and a method according to the preambles of the independent claims.
  • Cavities and applicators for microwave heating of materials are typically resonant in operation, since such a condition results in possibilities of achieving a high microwave efficiency.
  • Typical cavity/applicator loads have either a high permittivity such as 10 to 80 for polar liquids and compact food substances, or a lower permittivity but then also a low loss factor and a larger volume, such as in drying operations. In both these cases there is a need for the microwave energy to be reflected and retro-reflected many times in the cavity/applicator in order for a sufficient heating efficiency to be obtained.
  • resonant conditions entails a limitation of the frequency bandwidth of proper function. There are three methods in use to overcome the practical problem of limited resonance frequency bandwidth:
  • An overall object of the present invention is to achieve a microwave heating device having a stable resonant frequency for a large variety of load geometries and permittivities, and also being less complex, more robust and less expensive than prior art arrangements.
  • This object is achieved by the present invention according to the independent claims. Preferred embodiments are set forth in the dependent claims.
  • the present invention relates to a microwave enclosure which may be a partially open or closed resonant applicator incorporating a dielectric structure between a periphery wall and the load.
  • the applicator is in principle mathematically cylindrical, which means that it has a defined longitudinal axis and a constant cross surface area (including that of the dielectric structure) along this axis.
  • the type of mode in the applicator is essentially fieldless along a longitudinal axis in a central region of the applicator.
  • the resonant frequency is reduced when a load is inserted, and if the load is not so large that it modifies the applicator mode pattern significantly, a higher load permittivity further lowers the resonant frequency.
  • the device according to the present invention is essentially self-regulating by the mode being of a particular hybrid type.
  • the mode can be said to consist of a TE part (with the axis as reference) and a TM part, the latter having an "inherent" higher resonant frequency and becoming stronger in relative terms when a load is inserted into the applicator, so that a compensation of the lowering of resonant TM mode frequency occurs.
  • the hybrid mode is of the HE type and have all six E and H orthogonal field components. It may exist in its basic form in a circularly cylindrical waveguide or cavity having a concentric dielectric at the periphery or further inwards. A TE mode with higher first (rotational, m ) index than zero has this theoretically known property.
  • the mode is to be fieldless at the longitudinal central axis in the present case, so the lowest first index is 2.
  • Such applicators may be quite small, but applicators with first indices over 10 are also possible, resulting in a very wide application area for loads a fraction of a mL up to tens of L in volume, at 2450 MHz.
  • An applicator for small loads may be basically closed and sector-shaped with a minimum sector angle of 360 m /4; in such cases an integer index is no longer needed.
  • An applicator for large loads that are for example tube-shaped may be circular and open in central areas at the axis, for load insertion.
  • the invention deals with and depends on certain properties of arch surface modes.
  • Such modes can exist in cylindrical cavities with circular and elliptical cross sections, as well as with some polygonal cross sections. It has, however, been found that the deviations from smooth surfaces caused by the edges at corners may be unfavourable in some circumstances even with more than regular 12-sided polygonal cross sections. Therefore, and since elliptical cross sections offer advantages only in some distinct cases, mainly circular cross sections - and in particular cross sections consisting of a circular sector - are dealt with here. More detailed extensions for non-circular peripheral geometries will follow later.
  • the TE 41 mode is now dealt with (see figure 1). It has 8 maxima of the axial magnetic field (which is the dominating magnetic field direction) along the circular periphery of an empty waveguide or cavity.
  • the magnetic field is dashed and the electric field (which only exists in the plane perpendicular to the axis) is drawn as continuous lines.
  • An air filled empty TE 411 cavity is resonant at 2450 MHz when it has an axial length of 100 mm and is about 260 mm in diameter. Most of the energy is concentrated at the periphery, and can be described as two propagating waves along that, in opposite directions then setting up a standing wave pattern.
  • Arch surface modes can exist in confining geometries having a curved outer metal wall.
  • that of circularly cylindrical waveguides and resonators they are defined by the axis being fieldless.
  • the first (circumferential variation, defined to be in the ⁇ -direction) index is "high”
  • the second (radial variation, defined to be the p-direction) index is "low”
  • the third, axial (defined to be the z direction) index is arbitrary.
  • the most common polarisation type for arch surface modes is TE, which means that there is no z -directed E field. Typically, there is a dominating z -directed magnetic field (and hence a ⁇ -directed wall current) at the curved metal surface.
  • the first index must be at least 2.
  • the first index must also here be at least 2.
  • TE modes generally couple less efficiently to dielectric loads which are characterised by having a larger axial (circumferential, polygonal or circularly cylindrical) surface than its "top” and “bottom” (constant z plane) surfaces, since their E field is only horizontally directed and will therefore be perpendicular to any vertical load surface. They also have higher impedance than that of free space plane waves, which again results in a poorer coupling to dielectric loads which are inherently low impedance.
  • Q value quality factor
  • TM modes have z -directed E fields and are low impedance. They therefore couple significantly better to loads as above. However, that also means that loads which are not very small may influence the overall system properties, by for example causing a very significant resonant frequency change which offsets the advantage of a lower Q value (and by that the larger frequency bandwidth of the resonance).
  • a subgroup of the arch surface modes are the arch surface modes bound by a dielectric wall structure in the form of e.g. slabs, tiles or a plane or curved sheet.
  • the present invention is directed to this subgroup of arch surface modes, i.e. to microwave heating devices that include a closed cavity provided with a dielectric wall structure essentially located between a periphery wall of the cavity and one or many loads to be heated inside the cavity.
  • the field impedance of the radially inwards-going evanescent mode is high and inductive. Since the load is supposed to have a significantly larger permittivity than air, the wave energy having reached the load is no longer evanescent. A significant absorption can take place, provided the wave energy density has not fallen off "too much" at the load location. However a load located near the edge tip will couple very poorly. Obviously, by locating a smaller load closer to the arched part of the cavity, the coupling will become stronger. It is also influenced by the load location in the angular direction, since the strength of in particular the magnetic field varies with location relative to the microwave feed or radial wall locations.
  • Microwaves may propagate along the boundary between two dielectrics, provided one of the regions has some losses (a so-called Zennek wave). Waves may also propagate without losses, along and bound to a lossless dielectric slab (a so-called dielectric-slab waveguide).
  • a lossless dielectric slab a so-called dielectric-slab waveguide.
  • the dielectric has a metal backing on one side - as is the case for the present invention; the modes are then trapped surface waves.
  • the lossless propagation means that there is no radiation away from the system, in all the cases above - if there is no disturbing or absorbing object in the vicinity of the surface.
  • the mode type is of the TM type, with the propagation in the direction (z) in the feeding TE 10 waveguide in essence having a dielectric slab filling being open to ambient in one broadside ( a side). Hence, the mode field just outside the dielectric filling has no z-directed magnetic field but E fields in all directions.
  • the mode used in the cavity according to the present invention is a hybrid mode that is defined herein as a mode where both E- and H-fields exist in the z-direction (being the longitudinal direction of the cavity.). In the hybrid mode the TE- and TM-modes exist and have radially directed H-fields.
  • the hybrid mode HE 311 has all 6 components in a cavity provided with rotationally symmetrical dielectric structure.
  • TM arch surface modes with the same three indices as TE modes have a higher resonant frequency in the same cavity (i.e. known diameter and length).
  • f R is the resonant frequency
  • c 0 the speed of light
  • mnp the mode indices
  • a the cavity radius and h its height It is also important that all TE and TM modes in circular waveguides are orthogonal (except for the TE 0 and TM 1 series, which are, however, not arch surface modes). Hence, they cannot couple energy to each other.
  • Figure 2 shows a cross-sectional view in the xy plane, of a 120° sector applicator (or cavity) comprising a periphery wall 2, side walls 4, a load 6, a dielectric wall structure 8 and a microwave feeding means 10, where the dielectric wall structure comprises four flat dielectric tiles.
  • Figure 3 illustrates in a perspective view a similar heating device but here with a dielectric-coated periphery wall 2.
  • the dielectric wall structure is about 7 mm thick and has a typical permittivity of about 7,5.
  • the loads are quite large (30 to 40 mm diameter) and the applicator radius is about 85 mm; the height is about 80 mm and the operating frequency is in the 2450 MHz ISM band.
  • the field patterns of the TE 311 mode dominate. That mode should not have any z -directed E component but the applicator mode has. This can be verified by microwave modelling, but the other components of the TM 311 mode ( xy- plane H fields with maxima at the ceiling and floor, and xy -plane E fields with maxima at half height) are "hidden" since the TE 311 mode has those same components.
  • the cavity mode is a hybrid HE 311 mode, where the cavity field intensities of the TE type are stronger than those of the TM type.
  • the antenna protrusion was quite small, in practice being in the same plane as the cavity wall (still with a hole in the ceramic block).
  • the ceramic permittivity was 7,5-j0,0125 throughout; this corresponds to a penetration depth of 4,2 m.
  • This field component is strongest at the half height of the circular periphery; there are maxima at 0°, 60° and 120°. Hence, a vertical slot feed at 0° or 120° is feasible.
  • the complementary E field to obtain a Poynting vector is then horizontal radial.
  • the feed configuration is shown in figure 4; there is a normal TE 10 waveguide beside the cavity, with a vertical slot at the end.
  • the envelope of the Hz field in a very similar scenario, at half the cavity height, is shown in figure 5.
  • the field pattern 12 in the dielectric wall structure resulting from the TE 31 mode part is schematically illustrated.
  • the dielectric material used in the dielectric wall structure should have such a high permittivity that a substantial part of the oscillating energy is bound to the periphery region.
  • the only presumption for a HE mode to exist is that the permittivity ( ⁇ ) is greater than 1. This results in a wide variety of combinations of the permittivity and the thickness of the dielectric wall structure. E.g. if ⁇ is above 9, the (ceramic) cladding becomes rather thin, resulting in possible tolerance problems.
  • the permittivity is preferably between 4 and 12.
  • One design consideration is that it may be more difficult to metallise the outer surface of the ceramic than to leave an air distance between it and the cavity periphery. According to one embodiment of the present invention it has been found that a distance of 2 to 4 mm is feasible, in cases where a minimum distance is desirable for achieving a very small applicator.
  • the distance between the dielectric wall structure and the periphery wall is increased to at least 15 mm, a second trapped surface wave occurs in that region and the axial magnetic field of the mode changes sign in the dielectric wall structure.
  • the mode then becomes of the same kind as the basic (now Cartesian/rectangular) TM- zero dielectric-slab type. If the applicator is circularly cylindrical, a number of standing (integer wavelengths) waves will occur circumferentially, with the right dimensions.
  • Such an applicator will still retain the radial index 1 inwards (where the load(s) is/are), but may be easier to feed if very large (exceeding 300 mm or so at 2455 MHz, corresponding to circumferential index 10 or more (if 10, there are 20 standing wave maxima around the periphery).
  • a particular advantage is that the feed needs not to be close to the tiles; near-field excitation resulting in risks of arcing or local overheating of the tile are drastically reduced in high power systems. It has turned out that it is possible to use a larger distance (25 mm or more at 2450 MHz) between the inner surface of the periphery wall and the dielectric wall structure.
  • the two mode types are then dominantly TM 0 and TM 1 . In the former case, there is no polarity change across the dielectric structure, and in the latter case there is one.
  • the resulting cavity mode will have a lower first (the circumferential) index with the ceramic TM 0 field than with the ceramic TM 1 field, in spite of the radial index now being 2. That means that in this preferred case, the radial inwards evanescence will be slower and the mode behaviour also be less influenced by the load.
  • the load is located close to the inner surface of the dielectric wall structure.
  • the feeding means (between the dielectric structure and the periphery wall) can now be such that insignificant near-fields exist on the inner surface of the dielectric structure under conditions of normal high power transfer (i.e. impedance matching).
  • the feeding means is a common quarterwave radially directed coaxial metal antenna.
  • Arranging the dielectric structure at significant radial distance from the cavity periphery wall allows dual antenna constructions with a phase delay, resulting in an essentially unidirectional energy to flow inside the cavity in the circumferential direction.
  • the radial airspace between the periphery wall and the dielectric structure is up to half a free-space wavelength, which in a preferred embodiment is 20-30 mm.
  • Either of the rectangular ceramic mode TM 0 or TM 1 is used, and TM 0 is typically preferred and is also what is obtained when the distance between the periphery wall and the dielectric structure is short.
  • figures 14 and 15 illustrates two embodiments of microwave heating devices provided with large radial airspaces according to the present invention.
  • Figure 14 is a cross-sectional view of a circular cylindrical cavity including a periphery wall 2, an airspace 18 between the periphery wall and the dielectric wall structure 8 that encloses the load cavity 6.
  • a feeding means 10 is arranged through the periphery wall.
  • Figure 15 shows a cross-sectional view of a sector-shaped microwave heating device that in addition to the items of the embodiment in figure 14 includes two sidewalls 4.
  • the operating resonance frequency is essentially constant, it may be set to a suitable value in production trimming, by some means. It has been found preferable to include a small radial metal post 22 (see figure 2) positioned at the same location as the microwave feeding point but in the next halfwave position of the field (which has two halfwaves in figure 2 as drawn; that also applies to figures 5 and 13).
  • the metal post provides an about 50 MHz downwards adjustment of the resonant frequency in the 2450 MHz band, without any detrimental effects.
  • the opening may have a diameter of 4 mm and the post is then less than 2 mm.
  • Microwave losses in the ceramic tiles cannot be avoided. As a matter of fact these ultimately determine how small loads can be heated efficiently. However, efficient heating of very small loads is difficult to control, due to the minute energy requirement. With “controlled” losses in the ceramic tiles, these can be said to be connected in electric parallel with the load and thus limit the "voltage”. This results in a maximum heating intensity in the load when it absorbs the same power as the tiles (and also the cavity metal walls), and this intensity then falling off rather than remaining constant if the absorption capability of the load decreases further.
  • a second preferred embodiment of the present invention comprises a group of different variants that all fulfil the following design goals:
  • the cavity carries a dominating mode which is evanescent radially inwards towards the axis of a circular or sector-shaped cavity, in an airfilled region being either very small or at least trapezoid (triangular is preferred), so that resonances determined by the load itself and this workspace are deprecated.
  • a dominating mode which is evanescent radially inwards towards the axis of a circular or sector-shaped cavity, in an airfilled region being either very small or at least trapezoid (triangular is preferred), so that resonances determined by the load itself and this workspace are deprecated.
  • FIGs 6-9 illustrates different variants of the second preferred embodiment.
  • the triangular applicator as in figure 7, is basically just a distorted sector-shaped design for resonance of the mainly HE type hybrid arch surface mode. It has been found that the flat instead of arched ceramic does not give as good results with regard to frequency constancy for different loads, but results may be sufficient if load geometry or volume constraints are introduced.
  • the general geometry of the second preferred embodiment is that of a cylinder with triangular cross-section, containing a dielectric wall structure having a rectangular cross section the base side.
  • the cavity feed is by a small, central coaxial antenna.
  • the adaptation of resonant frequency to about 2455 MHz is by changing the overall height. For that reason, the original height should be higher than anticipated for 2455 MHz resonance, so that it can more easily be changed.
  • the shape is shown in the figures 6 and 7.
  • the triangle above the ceramic has a base side of 80 mm and a height of 54 mm.
  • the vertical cylinder height for about 2455 MHz resonance is about 61 mm, but the original height should be made 80 mm.
  • the cavity without ceramic consists of a triangular plus a rectangular part. The latter being 80 ⁇ 12 mm horizontally.
  • At the half height there is a centred coaxial feed with a corresponding hole through the ceramic.
  • the hole is 8 mm in diameter.
  • the load axis and tube axis nominal positions are 32 mm from the applicator tip.
  • a top wall 14 and a bottom wall 16 that together with the side walls 4 and the dielectric wall structure make up the closed cavity.
  • the feeding means 10 is a coaxial probe.
  • figure 10 is shown a schematic and simplified set up of 6 microwave heating devices as the one illustrated in figure 7 arranged together. Please observe that no feeding means are included in the figure.
  • the cavity being a cylinder having a circular cross-section and is provided with one single feeding means that creates a single standing wave pattern within the cavity.
  • This embodiment is primarily intended for heating multiple equal loads located symmetrically as illustrated in the schematic drawing in figure 11 that shows a cavity provided with 6 loads.
  • the standing wave pattern may be of the HE 6,1 mode and have one load at each field maximum, i.e. 12 loads, placed 30° apart or 6 loads (every second field maximum, i.e. 60° apart) or 4 loads (every third field maximum, i.e. 90° apart) or 3 loads (i.e. 120° apart) or 2 loads (i.e. 180° apart) or naturally one single load (schematically illustrated in figure 12).
  • Figure 11 shows a circular microwave heating device with dielectric wall structure 8 and a feeding means 10.
  • the device may be in the HE 3 ; 1 ; 1 mode and there will then be 6 field periods, so that 6 equal loads 6 arranged in a circular fashion will be equally treated. Since the system resonance Q factor can be made as high as desired (due to the mode evanescence), there can actually be an extremely similar "impinging" field to all loads. It is now possible to choose the load locations in relation the positions of the standing magnetic and electric fields, so that the loads are treated by equivalent current or voltage sources, respectively.
  • the result may be a negative or positive feedback of relative heating; for example by a hotter load of a number of otherwise equal loads being heated less, or for example by a larger load being heated more strongly - or vice versa, which is of course not desirable.
  • the cavity has a smaller size, and the periphery wall and the dielectric structure have circular cross-sections concentrically arranged with regard to each other.
  • this embodiment also covers variants where the periphery wall and the dielectric structure have a cross-section that is a part of a circle.
  • the outer radius of the dielectric structure 8 (in figure 13) with a permittivity of 9 is 50 mm (which also is the radius of the inner surface of the periphery wall) and an opening 6 for the load with a radius of 20 mm.
  • Figure 13 illustrates the field pattern 12 in a semicircular cavity provided with feeding means 10 working at 2450 MHz at the lowest part in the figure. The field pattern will then have two whole and two half waves.
  • centre angle may instead be 120° giving the same function.
  • the height of the cavity is about 50 mm (e.g. 49 mm).
  • the radial thickness of the dielectric wall structure (ceramic) is large and the arch-trapped evanescent resonance primarily takes place in the dielectric structure.
  • two hybrid modes HE m2;2;p and HE m1;1;p , with m2>m1
  • the coupling factor from a simple radial feeding antenna will become different for the two modes, since the fields of the HE m2;2;1 mode are more tightly bound to the dielectric and therefore couples less strongly then the HE m1;1;1 mode which has a more constant field near the cavity periphery wall.
  • a cavity with a large load will get a lower quality factor (Q value), since stationary conditions occur after fewer retro reflections in the cavity.
  • a design goal for a single mode resonant cavity for heating is therefore to set the coupling factor not to be too low for the largest (or most strongly absorbing) load, to be about 1 (critical coupling, resulting in impedance matching and thus maximum system efficiency) for the most typical load requiring high power, and not to be too high for the smallest (or weakly absorbing) load.
  • the dynamic range of the system is extended by using the HE m2;2;1 mode to heat small loads since its coupling factor for such loads is smaller than that of the HE m1;1;1 mode - and by using the HE m1;1;1 mode to heat larger loads since its coupling factor for such loads is larger than that of the HE m2;2;1 mode.
  • the HE m2;2;1 mode will be strongly undercoupled for large loads and thus not disturb the action of the HE m1;1;1 mode.
  • the HE m1;1;1 mode will be overcoupled and may then disturb the action of the desired HE m2;2;1 mode in that case.
  • FIG 16 illustrates a microwave heating device according to the fourth embodiment of the present invention.
  • the device comprises a sector-shaped cavity comprising a periphery wall 2 and two sidewalls 4" that encloses the dielectric wall structure 8" and the load 6.
  • the dielectric wall structure has the form of two equal, flat tiles that extend all the way from the bottom wall (not shown in figure 16) to the top wall (not shown in figure 16) of the cavity.
  • the tiles are typically 10 mm thick, 80 mm high and have typically an ⁇ value of 8, the radius of the cavity is 85 mm and the sector angle is 120°.
  • One important feature of the fourth embodiment is that there is a significant radial distance between the curved periphery wall 2 and the dielectric wall structure 8" where air spaces 18' are formed. This is important since only then can two close resonant frequencies for modes of the HE m1;1;p and HE m2;2;p types easily be found and used.
  • a metal post (not shown in figure 16) may be used for fine-tuning of the resonant frequency of the HE m1;1;p mode. There may also be a need to fine-tune to zero difference between that resonance and that of the HE m2;2;p mode. This is achieved by moving the tiles inwards in the radial direction.
  • a microwave feeding means 10 here in the form of a coaxial antenna.
  • the insertion depth of the antenna is sensitive for the proper function of the microwave device. In the case illustrated in figure 16 the antenna insertion depth into the cavity is about 7 mm and its diameter is about 3 mm.
  • the frequency of both resonances is reduced somewhat with increased insertion depth - which of course also results in an increase of the coupling factor.
  • the load may have diameters ranging from 3 mm to 20 mm, and heights from 20 to 60 mm.
  • a number of data modelling of the system according to the fourth embodiment have been performed primary to investigate the frequency behaviour for different loads. This investigation confirms that a high efficiency is maintained under all conditions, with regard to the resonant frequency variability.
  • the dual hybrid arch surface mode cavity according to the fourth embodiment of the present invention provides a high heating efficiency for an exceptionally wide range of loads.
  • the modes are interchangeably over- and undercoupled for large and small loads. This results in at least one of them couples well to almost any reasonable cavity load. This extends the range of use to also small loads of about 0,1 mL (depending on the permittivity and how much overpowering is to be used).
  • Such overpowering (perhaps up to 700 W input power) may be used with such small loads, since the cavity antenna is not located close to any ceramic tile which would otherwise cause field concentrations.
  • the field pattern in the dual hybrid arch surface mode cavity has an improved coupling to some types of very small load geometries, in comparison with a single hybrid mode cavity.
  • the dual hybrid arch surface made cavity also provides possibilities for a quite even heating pattern in several load geometries - both large and small, and not necessarily in the shape of a vial. Examples of such extended use is heating of thin and horizontally flat loads, and use of a flow-through load application for processing of solid, semisolid or liquid loads in a type having a diameter up to 40 mm.
  • figure 17 shows a block diagram of a system for using the microwave heating device according to the present invention.
  • An operator controls the system via a user interface (not shown) connected to a control means that inter alia controls the microwave generator with regard to e.g. the frequency and energy.
  • the microwave generator applies the microwaves to microwave heating device via the microwave feeding means.
  • the control means may also by provided with measurement input signals from the microwave heating device; these signals may represent e.g. the temperature and pressure of the load.
  • the present invention also relates to a method of heating loads in a microwave heating device or in a microwave heating system according to any above-mentioned embodiment.
  • the method comprises the steps of arranging a load in the cavity and applying microwave energy at a predetermined frequency to the microwave heating device in order to heat the load(s).
  • the present also relates to the use of a microwave heating device or a microwave heating system according to any above-mentioned embodiment for chemical reactions and especially for organic chemical synthesis reactions, and also the use of the above method for chemical reactions and especially for organic chemical synthesis reactions.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Health & Medical Sciences (AREA)
  • Clinical Laboratory Science (AREA)
  • General Health & Medical Sciences (AREA)
  • Constitution Of High-Frequency Heating (AREA)
EP03102665A 2003-05-20 2003-08-28 Mikrowellenheizvorrichtung Withdrawn EP1521501A1 (de)

Priority Applications (8)

Application Number Priority Date Filing Date Title
EP03102665A EP1521501A1 (de) 2003-08-28 2003-08-28 Mikrowellenheizvorrichtung
AU2004241919A AU2004241919B2 (en) 2003-05-20 2004-04-30 Microwave heating device
JP2006532173A JP4299862B2 (ja) 2003-05-20 2004-04-30 マイクロ波加熱装置
CA002526474A CA2526474A1 (en) 2003-05-20 2004-04-30 Microwave heating device
RU2005139728/09A RU2324305C2 (ru) 2003-05-20 2004-04-30 Сверхвысокочастотное нагревательное устройство
PCT/SE2004/000669 WO2004105443A1 (en) 2003-05-20 2004-04-30 Microwave heating device
EP04730780A EP1625775A1 (de) 2003-05-20 2004-04-30 Mikrowellen heizvorrichtung
US10/556,505 US7528353B2 (en) 2003-05-20 2004-04-30 Microwave heating device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP03102665A EP1521501A1 (de) 2003-08-28 2003-08-28 Mikrowellenheizvorrichtung

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EP03102665A Withdrawn EP1521501A1 (de) 2003-05-20 2003-08-28 Mikrowellenheizvorrichtung

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3848106A (en) * 1972-05-29 1974-11-12 Stiftelsen Inst Mikrovags Apparatus for heating by microwave energy
US5834744A (en) * 1997-09-08 1998-11-10 The Rubbright Group Tubular microwave applicator
WO2001062379A1 (en) * 2000-02-25 2001-08-30 Personal Chemistry I Uppsala Ab Microwave heating apparatus

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* Cited by examiner, † Cited by third party
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US3848106A (en) * 1972-05-29 1974-11-12 Stiftelsen Inst Mikrovags Apparatus for heating by microwave energy
US5834744A (en) * 1997-09-08 1998-11-10 The Rubbright Group Tubular microwave applicator
WO2001062379A1 (en) * 2000-02-25 2001-08-30 Personal Chemistry I Uppsala Ab Microwave heating apparatus

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