CN112087834A

CN112087834A - Microwave device and method for suppressing the escape of microwaves outside the microwave cavity of a microwave device

Info

Publication number: CN112087834A
Application number: CN202010536529.0A
Authority: CN
Inventors: 赖纳·岑特纳; 海莫·科特齐安
Original assignee: Anton Paar GmbH
Current assignee: Anton Paar GmbH
Priority date: 2019-06-13
Filing date: 2020-06-12
Publication date: 2020-12-15
Also published as: AT522473B1; AT522473A4; DE102020114043A1

Abstract

A microwave device and a method of suppressing the escape of microwaves outside a microwave cavity of a microwave device, the microwave device (100) comprising: a microwave cavity (102) in which microwaves can be emitted and/or can be generated; an at least partially electrically insulated fluid line (104) for conducting an electrically conductive fluid (106) between an interior (108) and an exterior (110) of the microwave cavity (102); an at least partially electrically conductive attenuation structure (112) at least sectionally surrounding the fluid line (104) for attenuating microwaves in an exterior (110) of the microwave cavity (102); and additional means (114) for suppressing microwave discharge into the exterior (110) of the microwave cavity (102) due to a coaxial arrangement formed between the attenuating structure (112) and the electrically conductive fluid (106) located in the fluid line (104). With this microwave device, generating microwaves in a microwave cavity and conducting fluid between the interior and the exterior of the microwave cavity through a fluid line is achieved with high operational safety.

Description

Microwave device and method for suppressing the escape of microwaves outside the microwave cavity of a microwave device

Technical Field

The present invention relates to a microwave device and a method for suppressing the escape of microwaves from a microwave device.

Background

Microwave devices include high power oscillators (e.g., magnetrons) designed to generate electromagnetic waves in the microwave length range. Microwaves are absorbed by different materials, depending on their molecular structure, which leads to heating of the materials.

US 5,719,380 discloses a facility for heating a flowing fluid with microwave energy, comprising a pipeline having an inlet section, an outlet section and a holding section, wherein at least the holding section of the pipeline is made of a substantially microwave transparent material. A temperature probe is preset for measuring the temperature of the flowing fluid in the outlet section. The cross-sectional area of the holding section is much larger than the cross-sectional area of the outlet section, so that the flow velocity through the holding section is slower than the flow velocity through the outlet section from the holding section to the temperature sensor. Microwave energy is used to heat the flowing fluid in the holding section, with the microwave energy being generated by a source controlled in response to the signal of the temperature probe. The holding section of the pipeline is located in the waveguide and is elongated transversely therethrough. The waveguide is dimensioned such that an electromagnetic standing wave can be built up therein, wherein the retaining section is located in the region with the greatest field strength.

US 5,659,874 discloses a plant for performing a chemical process, comprising: a working chamber defined by an upper member, a lower member, a sidewall, and a door; a microwave energy generator for the chamber; and a reactor comprising at least one journal resting on the support in the chamber. The chamber is penetrated by at least one passage which makes possible the connection of the journal of the reactor to a connecting line which is fixed to an external installation for carrying out the chemical reaction. The chamber is also penetrated by two further conduits which respectively enable the connection of two further journals to the reactor.

It is very challenging to bring the line guiding the fluid out of the microwave cavity where the microwaves are generated in operation.

Disclosure of Invention

It is therefore an object of the present invention to provide a microwave device with which the generation of microwaves in a microwave cavity and the conduction of a fluid between the interior and the exterior of the microwave cavity via a fluid line are achieved with high operational safety.

This object is achieved by the subject matter of the independent claims. The dependent claims specify particular embodiments of the invention.

According to an embodiment of the present invention, a microwave device is completed, comprising: a microwave cavity in which microwaves can be emitted and/or can be generated; an at least partially electrically insulated fluid line for conducting an electrically conductive fluid between the interior and the exterior of the microwave cavity (e.g., from interior to exterior or from exterior to interior); an at least partially electrically conductive attenuation structure at least partially surrounding the fluid line for attenuating microwaves in the exterior of the microwave cavity; and additional means for suppressing or reducing microwave emissions into the exterior of the microwave cavity. The discharge of microwaves into the exterior of the microwave cavity occurs due to the coaxial arrangement formed between the attenuating structure and the electrically conductive fluid located in the fluid line.

According to another embodiment of the present invention, a method for suppressing the escape of microwaves to the outside of a microwave cavity of a microwave device during conduction of an electrically conductive fluid between the inside and the outside of the microwave cavity by an at least partially electrically insulated fluid line is presented, wherein the microwaves propagate within the microwave cavity, wherein the method comprises: conducting an electrically conductive fluid between the interior and the exterior of the microwave cavity by a fluid line; attenuating the microwaves in the exterior of the microwave cavity by means of an electrically conductive attenuation structure which surrounds the fluid line at least in sections; and taking additional measures to suppress microwave discharge into the exterior of the microwave cavity due to a coaxial connection or coaxial arrangement formed between the attenuating structure and the electrically conductive fluid located in the fluid line.

Within the framework of the present application, the term "microwave" may be understood in particular as electromagnetic radiation in the frequency band between 0.3GHz and 300 GHz.

Within the framework of the present application, the term "microwave cavity" may be understood in particular as a microwave applicator in which a specimen (sample) or other substance of interest is subjected to the application of microwaves or is exposed to microwaves. Such a microwave cavity may, for example, be delimited by walls, in the interior of which microwaves are generated and/or emitted in a defined manner.

Within the framework of the present application, the term "fluid" may be understood in particular as a liquid and/or a gas, which optionally comprises solid particles. In particular, in embodiments of the present invention, the electrically conductive fluid may be directed through a fluid line (e.g., a capillary, hose, or tube). Examples of electrically conductive fluids are liquids comprising or consisting of acids, salt solutions and/or ionic liquids.

Within the framework of the present application, the term "attenuating structure" may be understood in particular as an at least partially electrically conductive body which may be placed on or designed integrally with the microwave cavity and/or may also be partially introduced into it and attenuates or attenuates microwaves which undesirably escape from the microwave cavity. Thereby, the microwave intensity in the environment range of the microwave cavity can be reduced. For example, the attenuating structure may at least sectionally enclose or surround the fluid line leading out of the microwave cavity in order to attenuate the microwave radiation emitted by the fluid line.

Within the framework of the present application, the term "additional means for suppressing microwave emissions into the outside of the microwave cavity due to the coaxial arrangement produced between the electrically conductive fluid and the attenuating structure" may be understood in particular as a solid structure or a mechanism which prevents or attenuates microwave emissions caused by the fluid lines guiding the electrically conductive fluid and the surrounding attenuating structure on the basis of coaxial artefacts (Koaxial-artfakt). In this case, the device can have an additional action mechanism compared to the attenuation structure to prevent the emission of microwaves into the outside of the microwave cavity. Intuitively, the electrically conductive fluid in the interior of the electrically insulated fluid line is in turn surrounded by an electrically conductive attenuating structure, which may function in a manner similar to a non-ideal or actual coaxial cable. This undesirable, non-ideal coaxial arrangement can result in undesirable microwave emissions outside the microwave cavity. The device may be designed to prevent, suppress or even eliminate unwanted microwave emissions outside the microwave cavity resulting from the combined action of the electrically conductive fluid, the electrically insulating fluid line and the electrically conductive attenuating structure.

According to an embodiment of the present invention, a microwave device may be provided which prevents or even eliminates undesired microwave emissions outside the microwave cavity due to parasitic co-action of coaxially arranged components "electrically conductive fluid-electrically insulated fluid line-electrically conductive attenuation structure", even when electrically conductive fluid is transferred between the inside and the outside of the microwave cavity by means of at least section-wise electrically insulated fluid lines. The electrically conductive attenuation structure may be disposed on a microwave cavity in the interior of which microwaves are generated and/or emitted (e.g., by a microwave generator) and which includes channels that also serve to guide fluid lines of the electrically conductive fluid. Such an attenuating structure attenuates the propagation of microwaves by virtue of the geometry conditions and thereby prevents them from undesirably escaping from the interior of the microwave cavity. This applies in particular to the opening of the feeder chamber and also to the passage of the non-conductive fluid. Within the framework of the present invention, it has been recognized that the concentric arrangement of electrically insulated fluid lines in the radial direction between the inner flowing electrically conductive fluid and the outer surrounding damping structure acts in a physical model like a non-ideal electrical coaxial cable. Such a coaxial structure can conduct microwaves very efficiently and is also used to conduct microwaves largely without loss. According to an exemplary embodiment, such undesired microwave emissions due to the coaxial arrangement forming the fluid may be effectively reduced by implementing additional means in the microwave device, wherein the additional means reduce or prevent microwave emissions that are generated based on the coaxial arrangement between the attenuating structure and the electrically conductive fluid, facilitated by the electrically insulating fluid line. In this way, undesired microwave emissions in the external environment range of the microwave cavity can advantageously be strongly suppressed. As a result, a microwave device with acceptably low external emissions can be achieved, which itself meets strict safety regulations with respect to stray radiation.

In the following, additional designs of the microwave device and method are described.

According to one embodiment, the fluid line may extend through a wall defining the microwave cavity. The passage of the fluid line through the opening in the wall of the microwave cavity presents a weak point of microwave tightness of the microwave cavity. This weak point can be remedied by presetting the attenuating structure. Within the framework of the present invention, it has however been realized that by presetting the attenuating structures, new problems arise due to the coaxial arrangement between the conductive fluid and the conductive attenuating structures, which problems can be substantially eliminated only by presetting a separate device for suppressing the effect of the coaxial connection.

According to one embodiment, the attenuating structure may include an attenuating tube penetrated by the fluid line. The aforementioned attenuator tube thus encloses the fluid line in a section adjoining the wall for defining the microwave cavity. The coaxial arrangement described above results therefrom, which, due to the resulting propagation conditions for microwave conduction, can lead to undesired microwave emissions, in particular at one end of the attenuation tube. This is reduced or even eliminated by additional means. For example, the attenuator tube may be connected on the end side to the wall defining the microwave cavity, or be formed integrally with the wall. Other configurations of the damping structure or the damping tube are also possible.

According to one embodiment, the device may be designed to interrupt the flow of fluid along the fluid line segment by segment. Such an embodiment is shown in fig. 1 and 2. By the targeted interruption of the flow of the electrically conductive fluid, the coaxially arranged inner conductor is intuitively divided into sections that are electrically isolated from each other. As a result, the parasitic coaxial arrangement is disturbed in a targeted manner, which leads to a reduction of the microwave emission outside the microwave cavity.

According to one embodiment, the device can be designed as a (in particular vertical) dripping section, or can comprise a dripping section, on which fluid escaping from the first section of the fluid line can be converted into a series of fluid drops which are spaced apart from one another, in particular falling in the vertical direction, before entering the second section of the fluid line. Intuitively, the fluid line is interrupted by the device and within the scope of the device the previously continuous flow of electrically conductive fluid is forced to break (preferably in the vertical direction). The flowing fluid can be divided in the region of the (in particular vertical) falling section into droplets or other fluid sections which are spaced apart from one another and are not conductively connected to one another. Thereby, the amount of microwaves radiated outside the microwave cavity can be effectively reduced.

According to one embodiment, the device can be designed to modify the, in particular horizontal, flow direction of the fluid flowing through the fluid line within the scope of the device, in particular to a vertical flow direction within the scope of the device. By deflecting the fine water flow from a first, in particular horizontal, flow direction in the region of the fluid line section by section into a further, in particular vertical, flow direction selectively in the region of the auxiliary device, it is possible to deliberately disturb the continuous fine water flow and thus avoid the coaxial arrangement being a cause of undesired escape of microwaves into the outside of the microwave cavity.

According to one embodiment, the device may comprise a valve, in particular comprising an electrically insulated, rotatable body, to transform the fluid into a series of fluid sections spatially separated from each other. If, for example, an electrically insulated valve body is rotated and an electrically conductive fluid flowing through a fluid line is operatively connected to the valve body, a continuous fluid flow may be converted into a series of spaced segments before that. Alternatively, it is also possible to open the valve according to a predefinable cycle and thereby to divide the continuous fluid flow into separate sections with a disturbance of the coaxial arrangement.

According to an alternative or supplementary embodiment, the device can be designed to electrically short the electrically conductive fluid flowing along the fluid line to the damping body at least in sections. Such an embodiment is shown in fig. 3 to 5. Intuitively, according to this embodiment, the electrically conductive fluid can be electrically coupled segment by segment to the electrically conductive damping structure when flowing through the dielectric fluid line, the electrically conductive fluid and the damping structure thereby being electrically shorted, i.e. being brought to the same electrical potential.

The described short-circuit between the conductive fluid and the attenuating structure may be realized directly (i.e. without an intermediate body between the fluid and the attenuating structure) or indirectly (i.e. with an intermediate body between the fluid and the attenuating structure).

Thus, in case of a direct electrical short between the conductive fluid and the attenuating structure, the conductive fluid may be in direct contact with a section of the attenuating structure. For example, the damping structure may be designed as a section of a fluid line and the electrically conductive fluid flows through, for example, arranged between two interrupted sections of the fluid line.

According to an embodiment comprising an indirect electrical short, the device may comprise as an intermediate body an electrically conductive and in particular highly thermally conductive pipe connection electrically coupled with the damping structure, which pipe connection is arranged between the first section and the second section of the fluid line and makes contact with the fluid when the electrically conductive fluid flows through the fluid line. Such an electrically conductive pipe connection can overlap an interrupted section of the fluid line and, on its outer side, be electrically conductively connected to the damping structure. The functionality of the undisturbed fluid line can thereby advantageously be combined with an effective prevention of the escape of microwave radiation out of the microwave cavity. By means of such a pipe connection, a short circuit between the conductive fluid and the attenuating structure can be achieved. The high thermal conductivity pipe joint may for example be made of a material having a thermal conductivity of at least 50W/mK and allows for a coordinated removal of heat from the fluid during operation of the microwave device.

According to an alternative or supplementary embodiment, the device may comprise an electrically conductive coaxial filter for additional microwave attenuation. Corresponding embodiments are shown in fig. 6 to 14. The coaxial filter can be intuitively designed as a conductive structure with a cavity or dielectric-filled cavity formed in its interior. The coaxial filter may be connected to the attenuating structure and enclose the fluid line segment by segment. Intuitively, in a corresponding configuration of the coaxial filter, outside the microwave cavity, a considerable escape of microwave radiation is strongly suppressed.

According to one embodiment, the coaxial filter is designed integrally with the attenuating structure. This design is simple to manufacture and is highly effective in preventing microwave radiation from exiting the microwave cavity.

According to one embodiment, the coaxial filter may surround the fluid line outside the microwave cavity. In this way, the coaxial filter may be particularly effective in reducing microwave radiation due to the electrically conductive fluid within the fluid line.

According to one embodiment, the coaxial filter may be designed as a circumferentially closed disk comprising a hollow core and/or a dielectric core centrally penetrated by the fluid line. The geometric parameters of the coaxial filter designed in this way can be adjusted or optimized in accordance with the particular application in order to keep the microwave radiation escaping out of the microwave cavity low or to avoid it altogether.

According to an embodiment, the device may comprise at least one further electrically conductive coaxial filter, in particular having the features described hereinbefore, for additional microwave attenuation. For example, a plurality of coaxial filters may be arranged in series. Alternatively or additionally, it is also possible to connect coaxial filters in parallel. By combining a plurality of coaxial filters, it is possible to avoid microwaves outside the microwave cavity, particularly strongly, above all for different filling levels of the hollow conductor.

According to one embodiment, the microwave device may comprise a constriction structure for selectively constricting the fluid line's cross-section through which the fluid may flow within the range of the coaxial filter. By constricting the fluid line section by section, in particular in the context of a coaxial filter, it is ensured that substantially the entire cross-section of the constriction is traversed by the fluid even at the filtering location in space when a smaller quantity of electrically conductive fluid is conducted through the fluid line. Thereby, it is possible to avoid compromising the attenuation efficiency and to avoid the escape of microwaves out of the microwave cavity, which may be due to the cross section of the fluid line being flowed through only partially by the electrically conductive fluid. It has been shown that an asymmetric filling of the fluid line with a conductive fluid over its cross-section leads to a poor suppression of microwaves outside the microwave cavity. The parasitic microwave radiation outside the microwave cavity can be suppressed particularly effectively in such a way that a complete flow through the fluid line in the region of the coaxial filter is promoted by the cross section of the fluid line being constricted section by means of the constriction.

According to a particularly preferred embodiment, the microwave device may comprise, instead of or in addition to the constriction, an electrically conductive insert which is selectively inserted into the fluid line in the region of the coaxial filter. This preferred embodiment is shown in fig. 12 to 14. The insert, which is preferably axially oriented with respect to the coaxial filter and radially surrounded by the fluid line and the coaxial filter, may significantly improve the functionality of the coaxial filter.

According to one embodiment, the insert may be in contact with the fluid flowing through the fluid line on the inner side. Thus, such an electrically conductive insert may be in direct contact with the electrically conductive fluid flowing through the fluid line on the inside of the fluid line. Advantageously, the inner wall of the fluid line and the inner wall of the insert may be designed to be flush or otherwise stepless in the flow direction of the electrically conductive fluid so as not to disturb the fluid flow.

According to one embodiment, the insert may be surrounded on the outside by a fluid line and thereby electrically isolated from the coaxial filter and/or the attenuating structure. However, the outer wall of such an electrically conductive insert may still be positioned within the fluid line, i.e. on the outside, covered by the electrically insulating material of the fluid line. In this way it is ensured that the insert is not shorted to the attenuation structure, but the effectiveness of the coaxial filter arranged outside the insert can still be improved. In particular, in this configuration, no special sealing measures in the interface region between the insert and the fluid line are required, which is advantageous in particular in corrosive fluids.

According to one embodiment, the insert can be designed as a pipe connection. Such a pipe connection can preferably be made of graphite, of electrically conductive plastic or of electrically conductive ceramic, in order to achieve particularly good corrosion resistance. Alternatively, such a pipe joint may be formed of a metal material.

According to one embodiment, the microwave device may be designed as one of the group consisting of a microwave synthesizer, a microwave analyzer, a microwave digestion instrument, a microwave extractor, a microwave evaporator and a microwave dryer. Microwave synthesis reactors may be used for synthesis applications. One example is the rapid heating of the reaction mixture to high pressures and temperatures by using microwaves. The microwave oven can complete the drying of the test piece by using microwaves. Specimen preparation for processing the specimen by microwave analysis or digestion may be performed in a microwave analyzer. Preferably, the synthesis and/or preparation of the test piece may be carried out in a microwave device. However, it is also possible to combine specimen preparation with subsequent analysis in one instrument.

According to one embodiment, the electrically conductive fluid may be an electrically conductive liquid, in particular an acid and/or salt solution. Other electrically conductive fluids, such as ionic liquids or ionized gases, may also be transferred between the interior and exterior of the microwave oven by fluid lines without excessive microwave discharge outside the microwave cavity.

According to one embodiment, the electrically conductive fluid may completely fill the cross-section of the fluid line, the electrically conductive fluid may only partially fill the cross-section of the fluid line, or there may be no electrically conductive fluid in the fluid line. When there is no electrically conductive fluid in the fluid line (e.g. no fluid at all or electrically insulating fluid), a separate attenuation structure can accomplish a strong attenuation of the microwaves so that no disturbing microwave quantities occur outside the microwave cavity. The means for suppressing the effect of the coaxial arrangement between the electrically conductive fluid and the electrically conductive attenuating structure may effectively prevent the microwaves from escaping out of the microwave cavity when the electrically conductive fluid completely fills the cross section of the fluid line. If only a portion of the fluid line cross-section is filled with electrically conductive fluid, the resulting asymmetric fluid geometry may result in some amount of microwave escape. Here, remedial action may be accomplished, for example, by providing a constriction, shorting between the conductive fluid and the attenuating structure, implementing a drip segment to interrupt fluid flow, and/or installing a conductive tubing segment into the fluid line.

Further advantages and features of the invention result from the following exemplary description of several embodiments, to which the invention is not restricted.

Drawings

Fig. 1 illustrates a microwave device according to an exemplary embodiment of the present invention in a schematic cross-sectional view.

Fig. 2 illustrates a state of the microwave device according to fig. 1, in which the electrically conductive fluid is transferred from the inside to the outside of the microwave cavity of the microwave device.

Fig. 3 illustrates, in a schematic cross-sectional view, a microwave device according to another exemplary embodiment of the present invention.

Fig. 4 illustrates a state of the microwave device according to fig. 3 in which a smaller amount of electrically conductive fluid is transferred between the inside and the outside of the microwave cavity of the microwave device, or the cross-section of the fluid line is only partially filled with electrically conductive fluid.

Fig. 5 illustrates a state of the microwave device according to fig. 3 in which a larger amount of electrically conductive fluid is transferred between the inside and the outside of the microwave cavity of the microwave device, or the cross section of the fluid line is completely filled with electrically conductive fluid.

Fig. 6 illustrates, in a schematic cross-sectional view, a microwave device according to a further exemplary embodiment of the present invention.

Fig. 7 illustrates a state of the microwave device according to fig. 6, in which a conductive fluid completely filling a cross-section of a fluid line is transferred between the inside and the outside of the microwave cavity of the microwave device.

Fig. 8 illustrates, in a schematic cross-sectional view, a microwave device according to yet another exemplary embodiment of the present invention.

Fig. 9 illustrates a state of the microwave device according to fig. 8, in which a quantity of electrically conductive fluid is transferred between the inside and the outside of the microwave cavity of the microwave device.

Fig. 10 illustrates a state of the microwave device according to fig. 8 in which a smaller amount of electrically conductive fluid is transferred between the inside and the outside of the microwave cavity of the microwave device than in the state according to fig. 9.

Fig. 11 illustrates a state of the microwave device according to fig. 8 in which a larger amount of electrically conductive fluid is transferred between the inside and the outside of the microwave cavity of the microwave device than in the state according to fig. 9.

Fig. 12 illustrates a microwave device according to a preferred embodiment of the invention in a schematic cross-sectional view.

Fig. 13 illustrates a state of the microwave device according to fig. 12 in which a smaller amount of electrically conductive fluid is transferred between the inside and the outside of the microwave cavity of the microwave device.

Fig. 14 illustrates a state of the microwave device according to fig. 12 in which a larger amount of electrically conductive fluid is transferred between the inside and the outside of the microwave cavity of the microwave device than in the state according to fig. 13.

Detailed Description

In the different figures, elements that are similar in structure and/or function in different embodiments are designated by the same reference numeral. The description of elements not described in detail in a particular embodiment can be found in the corresponding description in another embodiment.

Before describing exemplary embodiments of the present invention with reference to the attached drawings, several general aspects and basic techniques of the present invention should also be set forth:

according to an exemplary embodiment of the present invention, a microwave device is completed comprising a means for safely transporting an electrically conductive, in particular fluid, substance into and out of a microwave applicator or microwave cavity.

Microwaves may be used in particular for chemical specimen preparation and/or analysis and/or synthesis and/or for digestion. To this end, the reagent can be heated and/or the test piece can be digested, in particular under increased pressure, in the microwave cavity, and in this way, for example, the synthesis reaction can be accelerated and/or the digestion can take place. In this case, material suitable for heating by microwaves may be introduced into the feeder or microwave cavity and heated by microwave radiation introduced into the feeder or microwave cavity. Such feeder cavities or microwave cavities may be, for example, so-called multi-cavity cavities in which standing waves are superposed in a disordered manner and formed, or else, for example, the material to be heated is introduced directly into a suitably dimensioned waveguide, which waveguide comprises a defined propagation mode of microwaves.

The microwaves may be generated by a microwave source, such as a magnetron, klystron, backward wave oscillator, and/or semiconductor source. Instead of a magnetron and antenna, other microwave sources may be used which generate microwaves of the desired frequency or wavelength and which can be emitted into the feeder cavity via a propagation means (e.g. a hollow conductor or antenna arrangement or channel).

In this case, the material to be heated can be introduced into the microwave cavity or the feeder cavity, for example, through a door or other opening which can be closed in a microwave-tight manner. It is also possible to introduce the material to be heated into the feeder or microwave cavity, either continuously or intermittently in the channel, to withdraw it from the feeder or microwave cavity, or to direct it therethrough.

Microwaves are particularly suitable for exciting dipole and multipole vibrations of molecules due to their wavelength, these vibrational energies being converted into heat. In particular, the substance to be heated, such as a solvent, is selected on the basis of its dielectric properties. The basis of heating is here absorption. Microwave energy is absorbed by the dielectric material. In contrast, microwave radiation is reflected by metals and electrical conductors and is only slightly absorbed. These materials thus form the outer walls of the mould cavity, preventing microwave radiation from escaping from the feeder cavity or microwave cavity, and ensuring that a radiation mode is generated within the feeder or microwave cavity. However, suitable insulators are permeable (e.g. thermoplastics, in particular PTFE (polytetrafluoroethylene), glass and many ceramics). Thus, it serves as a container and tube for containing and/or feeding and/or discharging reagents.

By using high temperatures, the quality of the acidification can be improved significantly and the reaction time for decomposing the substances can be shortened rapidly. Thus, in addition to open digestion, closed digestion can be carried out under elevated temperature conditions and thus under concomitant elevated pressure. However, such reaction conditions may place high demands on the container material used. During the reaction, different chemicals, solvents and/or reagents may be input depending on the assay site. Another application is the evaporation of reagents from containers connected via a system of pipes to a vacuum pump located outside the feeder and a gas purging system connected therebetween. In this case, the steam and the condensate are drawn off from the feeder or microwave cavity.

If in this way, in particular, fluid substances such as liquid reagents are removed from or introduced into the microwave applicator or microwave cavity, it is advantageous not to lead to an unacceptably high escape of microwave radiation from the applicator or microwave cavity due to the openings necessary for this. Studies in the preparatory phase of the invention have shown that this requirement is only met in electrically insulating substances by correspondingly dimensioned damping tubes or other damping structures through which fluid lines made of dielectric material can be guided.

Embodiments of the present invention are based on the recognition that the fluid line is surrounded by a damping structure (in particular a damping tube) such that the electrically conductive fluid now acts as a built-in conductive substance, whereas the electrically conductive substance in the fluid line can be regarded as a fluid analogue similar to a coaxial electrical conductor and allows microwaves to escape from the feeder or microwave cavity outwards. Examples of electrically conductive fluids or substances are acid mixtures such as are used in the preparation of test pieces for wet-chemical microwave digestion.

Embodiments of the present invention complete an apparatus for safely transferring an electrically conductive fluid substance into and out of a microwave applicator or microwave cavity.

The attenuating structure, such as an attenuating tube having a corresponding length with respect to its effective diameter for microwave-sealed fluid transfer, reduces the component of microwave energy escaping from the applicator or microwave cavity to an acceptably low value. This is effective in a particular manner if the diameter is chosen in consideration of the dielectric properties in the hollow conductor such that propagation of the wave (cut-off wavelength) is no longer possible. Here, all configurations in the cross-section of the attenuating structure (in particular of the attenuating tube) are crucial in the design, i.e. configurations "empty", "partially filled" or "completely filled" with the non-conductive substance.

If the fluid, in particular a liquid, contained in the fluid line within the attenuation structure, in particular within the attenuation tube, is electrically conductive, then an electrically seen coaxial conductor is produced: fluid channel — a combination of a damping tube section for a predominantly dielectric fluid with negligible electrical conductivity or in an empty state and an additional damping element for an electrically conductive fluid.

The attenuation structure, which comprises a fluid channel for a mainly non-conductive dielectric fluid, particularly designed as an attenuation tube, may be implemented such that the penetration of microwave energy is sufficiently attenuated. Here, it is obvious to a person skilled in the art that the design for a circular hollow conductor can be defined according to the zero point of the bezier function. Here, dimensioning can be effected for the respective microwave frequency and the current propagation conditions in the fluid used (microwave propagation in the medium is effected at a lower wavelength than in vacuum, depending on the dielectric constant). The authorities open specific frequency bands for heating the dielectric medium (ISM frequencies). In particular, magnetrons of 915MHz, 2.45GHz and 5.8GHz may be used for these frequency bands. The specific design of the damping structure (in particular of the damping tube) can be implemented such that the escape of microwave energy is no longer possible or is below official preset values.

In the preparatory phase of the invention, it has been seen that when the electrically conductive liquid is located within a non-conductive hose or tube (or another fluid line) in the cross-section of the damping tube section, the damping tube section loses its damping properties completely or partially. The higher the conductivity of the fluid, the lower the penetration depth of the microwaves in the fluid. Viewed in cross section, the structure of the coaxial conductor, which comprises an electrically conductive fluid as the inner conductor, is produced visually in the metal channel. This may result in propagating microwave energy along the transmission segment in an undesirable manner.

The escape of microwave radiation should be avoided efficiently. At the same time, however, the attenuation properties of the hollow conductor and the passage of channels that are not filled with dielectric or filled with dielectric that is non-conductive should be maintained.

In the following, specific embodiments of the invention providing the desired functionality are described:

fig. 1 illustrates, in a schematic cross-sectional view, a microwave device 100 according to an exemplary embodiment of the present invention, wherein the fluid line 104 does not contain any electrically conductive fluid therein. Fig. 2 illustrates a state of the microwave device 100 according to fig. 1, in which the electrically conductive fluid 106 is transferred from the interior 108 to the exterior 110 of the microwave cavity 102 of the microwave device 100. By way of example, the microwave device 100 shown in the figures may be designed as a microwave synthesis reactor comprising an enlarged multi-mode chamber, or as a hollow conductor comprising a flow arrangement. The microwave apparatus 100 may include fluid channels in its wall or walls 118 for input and/or output of the test piece, reagents and test piece components. The microwave apparatus 100 may present a flow arrangement and the fluid line 104 may be part of the flow arrangement to transport the fluid specimen through the feeder.

The microwave device 100 has a feeder or microwave cavity 102 in which microwaves can be generated by means of a microwave source (not shown). Alternatively or additionally, microwaves may also be emitted into the microwave cavity 102. Also not shown, the processed substance may be located inside the microwave cavity 102, which is influenced by (in particular heated by) the generated microwaves. The microwave field should also be designed in the interior 108 of the microwave cavity 102, but it should not penetrate into the exterior 110 of the microwave cavity 102.

An electrically insulating fluid line 104 (e.g. a plastic hose) is provided for conducting an electrically conducting fluid 106 (e.g. an acid or salt solution) between an interior 108 and an exterior 110 of the microwave cavity 102. The conducting or conveying of the electrically conductive fluid 106 may be accomplished, for example, by a conveying device (not shown), such as a fluid pump.

As shown in fig. 1 and 2, the fluid line 104, which is located partially in the interior 108 of the microwave cavity 102 and partially in the exterior 110 thereof and extends through the wall 118 defining the microwave cavity 102, is surrounded segment by segment (more precisely, in the exterior 110) by an electrically conductive attenuating structure 112. The attenuating structure 112 may be made of metal, for example. Thus, the fluid line 104 extends through the wall 118 defining the microwave cavity 102. In the embodiment shown, the attenuating structure 112 is designed as an attenuating tube 116, within the lumen of which the fluid line 104 is disposed. As shown, the attenuating structure 112 includes an attenuating tube 116 penetrated by the fluid line 104, which may be connected on the end side to a wall 118 defining the microwave cavity 102, or may be integrally formed therewith. The attenuating structure 112 serves to attenuate microwaves in the exterior 110 of the microwave cavity 102. Intuitively, the region of the wall 118 of the microwave cavity 102 penetrated by the dielectric fluid line 104 clearly forms a weak point in shielding against microwaves with respect to the exterior 110 of the microwave cavity 102. Where the microwaves may escape from the interior 108 of the microwave cavity 102 in an undesirable manner. This undesirable phenomenon is suppressed by presetting the attenuation tube 116.

As described hereinabove, from an electrical perspective, the concentric arrangement of the electrically conductive fluid 106 (e.g., acid) in the lumen of the fluid line 104, the hollow cylindrical dielectric fluid line 104 surrounding the fluid 106, and the hollow cylindrical electrically conductive attenuation tube 116 forms a coaxial cable of fluid. Without wishing the applicant to be bound by a particular theory, it is presently assumed that: the coaxial arrangement between the fluid 106 and the attenuator tube 116 may result in undesirable leakage of microwaves from the interior 108 into the exterior 110 of the microwave cavity 102.

In order to reduce or completely eliminate this undesired effect, in the microwave device 100 according to fig. 1 and 2, in addition to the attenuating structure 112, means 114 for suppressing or reducing the microwave emission generated in the exterior 110 of the microwave cavity 102 due to the aforementioned coaxial arrangement are provided. This non-ideal coaxial arrangement is formed between the attenuating structure 112 and the electrically conductive fluid 106 located in the fluid line 104. As shown in fig. 2, the device 114 is designed to interrupt the flow of the electrically conductive fluid 106 along the fluid line 104 segment by segment. More specifically, in the embodiment shown, the device 114 is designed as a vertical drip section 120, wherein the fluid 106 escaping from the first section 140 of the fluid line 104 can be converted into a series of fluid drops 122 that are spaced apart from one another and, in the embodiment shown, fall in a vertical direction before entering the second section 142 of the fluid line 104. Intuitively, a continuous stream of fluid in the first section 140 is split by the drop section 120 into spaced apart fluid drops 122. The spaced apart fluid droplets 122 merge again into a continuous fluid flow only in the second section 142 of the fluid line 104. Thus, the device 114 is designed to change the horizontal flow direction of the fluid 106 within the device 114, via the two

sections

140, 142 of the fluid line 104, such that it is selectively converted within the device 114 into a vertical flow or fall of the fluid 106 that is not continuous during this time, thereby breaking the continuous, electrically conductive fine water flow. Thus, the conductive fluid 106 no longer behaves like an electrical cable. Thereby, the coaxial arrangement between the electrically conductive fluid 106 and the damping tube 116 is deliberately disturbed. Thus, the escape of microwaves into the exterior 110 of the microwave cavity 102 is advantageously suppressed.

Intuitively, the embodiment according to fig. 1 and 2 may be referred to as an attenuation tube 116, which comprises an inner conductor interruption in the form of a means 114 forming a drip segment 120. In the embodiment shown, escape of microwave radiation is achieved by appropriately interrupting the passage or inner conductor formed by the conductive fluid 106 and by the output, so as to interrupt the coaxial penetration of the conductive fluid section through the opening in the wall 118 of the feeder or microwave cavity 102.

According to fig. 1, there is no electrically conductive fluid 106 in the fluid line 104. More precisely, according to fig. 1, the fluid line 104 is empty, which is indicated by reference numeral 144. Thus, in the configuration according to fig. 1, the attenuator tube 116 is operative to substantially inhibit the escape of microwaves into the exterior 110 of the microwave cavity 102. The same applies to the transmission of dielectric, non-conductive fluids that can be heated by absorption in microwaves. Due to the absence of an inner conductor in the form of the conductive fluid 106, according to fig. 1, no coaxial arrangement is formed, so that this phenomenon also does not cause undesired escape of microwaves into the outer portion 110.

In contrast, according to fig. 2, the electrically conductive fluid 106 only fills the cross section of the fluid line 104 exactly partially. Fig. 2 thus shows the case of an inner conductor formed of a conductive liquid, wherein the electrically conductive fluid 106 is interrupted in order to inhibit undesired wave propagation from the microwave cavity 102 along the section being an electrical conductor. According to fig. 2, the described effect is achieved by means of a vertical dripping section 120 of the device 114.

Alternatively, the illustrated interruption of the continuous flow of the conductive fluid 106 can also be realized in other ways, i.e., the flow of the electrically conductive water can also be interrupted in a manner other than by, for example, the vertical drip section 120. This can be done, for example, by a valve that is opened and closed periodically. Such a valve can be, for example, a rotating, non-conductive element integrated in the outlet pipe and at the outlet opening. Thus, although not shown in the figures, the device 114 may alternatively or additionally include a valve for converting the fluid 106 into a series of spaced-apart fluid segments, similar to the case of the drop section 120. For example, such a valve may include a rotatable, electrically insulating body that acts on a continuously flowing electrically conductive fluid 106 such that it is divided into discrete segments.

Fig. 3 illustrates, in a schematic cross-sectional view, a microwave device 100 according to another exemplary embodiment of the present invention, wherein the fluid line 104 is devoid of the electrically conductive fluid 106. Fig. 4 illustrates a state of the microwave device 100 according to fig. 3 in which a small amount of the electrically conductive fluid 106 is transferred from the inside 108 to the outside 110 (and/or in the opposite direction) of the microwave cavity 102 of the microwave device 100. Fig. 5 illustrates a state of the microwave device 100 according to fig. 3 in which a larger amount of the electrically conductive fluid 106 is transferred from the interior 108 to the exterior 110 (and/or in the opposite direction) of the microwave cavity 102 of the microwave device 100 than in the state according to fig. 4. Within the framework of the description, the terms "small amount" and "larger amount" may particularly refer to the current filling state of the respective line and to whether the cross section of the line is completely filled. The total flow or mass flow rate is also dependent on the velocity of the fluid. According to fig. 3 to 5, in order to suppress microwave emissions into the exterior 110 due to the coaxial arrangement between the attenuation structure 112 and the electrically conductive fluid 106 in the fluid line 104, the additional device 114 is designed to electrically short, or thereby electrically couple, the electrically conductive fluid 106 flowing along the fluid line 104 section by section to the attenuation structure 112. For this purpose, the device 114 according to fig. 3 to 5 comprises an electrically conductive (and if appropriate also highly thermally conductive) pipe connection 122 which is electrically coupled to the damping structure 112 and which is arranged in the axial direction or flow direction between a first section 140 and a second section 142 of the fluid line 104 and comes into contact with the fluid 106 when the electrically conductive fluid 106 flows through the fluid line 104. Reference numeral 148 identifies the electrical contact between the electrically conductive attenuator tubes 116 and the tube fittings 122. Additionally, in fig. 4 and 5, the electrical contact between the electrically conductive fluid 106 and the pipe joint 122 is designated by reference numeral 146.

Illustratively, the embodiment according to fig. 3 to 5 shows the attenuator tube 116 in electrical contact with an outer conductor in the form of a tube connection 122, which in turn is in electrical contact with the electrically conductive fluid 106 on the inside. This embodiment also creates an electrical short of the conductive substance (i.e., the conductive fluid 106) to the attenuator tube 116. Thereby, the aforementioned coaxial arrangement of the fluids is advantageously disturbed. Another advantage of this embodiment is a constant geometry along the fluid path.

According to fig. 3, there is no electrically conductive fluid 106 in the fluid line 104 and the separate attenuator tube 116 effectively suppresses microwave emissions into the exterior 102.

According to fig. 4, the fluid line 104 is partially filled with the electrically conductive fluid 106, and according to fig. 5, the fluid line is even completely filled with the electrically conductive fluid. To inhibit undesired wave propagation from the microwave cavity 102, the inner conductor formed of a conductive liquid may be electrically shorted to the outer conductor, i.e., the attenuator tube 116, at the appropriate location, either directly (not shown) or indirectly (i.e., via the tube joint 122).

The embodiment shown in fig. 3 to 5 achieves the use of highly corrosion-resistant materials at a reasonable cost by using short electrically conductive pipe sections in the form of pipe joints 122 within the attenuation pipe 116. The preferred material for the liquid-wetted tube connector 122 has an electrical conductivity (e.g., graphite or conductive ceramic) that matches corrosion resistance.

An advantage of the microwave device 100 according to fig. 3 to 5 is that the possibility of discharging the thermal energy of the fluid is also possible by short-circuiting the fluid outlet tube to the surrounding damping tube 116 and to the outer wall or walls 118 of the mould cavity and/or the housing of the feeder or microwave cavity 102.

Another advantage of this embodiment is the lower geometric space requirement and the avoidance of spatial interruptions of the hose line or the omission of additional movable parts. Another advantage of this arrangement is the compatibility with the outgoing hot fluid, so that in the arrangement shown above, although an undesirable condensate film may form, it may likewise be electrically shorted to the outer conductor via the pipe joint 122. If the pipe joint 122 is made of a highly thermally conductive material, it may help to remove heat from the fluid line 104.

Fig. 6 illustrates, in a schematic cross-sectional view, a microwave device 100 according to a further exemplary embodiment of the present invention, wherein the fluid line 104 is devoid of the electrically conductive fluid 106. Fig. 7 illustrates a state of the microwave device 100 according to fig. 6 in which the electrically conductive fluid 106 is transferred from the interior 108 to the exterior 110 (and/or in the opposite direction) of the microwave cavity 102 of the microwave device 100.

Referring to fig. 6 and 7, the additional device 114 associated with the attenuating structure 112 includes an electrically conductive coaxial filter 124 for additional microwave attenuation. Intuitively, the coaxial filter 124 may be understood as an electronic component that affects the fluid coaxial cable formed by the concentrically arranged components "electrically conductive fluid 106" - "electrically insulated fluid line 104" - "electrically conductive attenuation tube 116" in such a way that the microwave radiation emitted by the fluid coaxial cable may be completely or partially filtered out by the coaxial filter 124 in the exterior 110 of the microwave cavity 102.

In the embodiment shown, the coaxial filter 124 is integrally formed with the attenuating structure 112 and integrally formed with the wall 118 of the microwave cavity 102. It is possible to form the coaxial filter 124 separately with respect to the attenuating structure 112 and/or with respect to the wall 118. Intuitively, the coaxial filter 124 forms a circumferentially symmetrical bulge of the attenuation tube 116. The coaxial filter 124 is shown completely surrounding the fluid line 104 outside the microwave cavity 102. More specifically, in the embodiment shown, the coaxial filter 124 is designed as a circumferentially closed disk 126 that includes a hollow core 128 centrally penetrated by the fluid line 104. The attenuator tube 116 is interrupted in the region of the coaxial filter 124. The outer wall of the fluid line 104 is separated from the outer confines of the in-line filter 124 by a hollow core 128.

Although not shown in the drawings, the apparatus 114 may also include a plurality of conductive coaxial filters 124 for additional microwave attenuation. For example, a plurality of coaxial filters 124 may be arranged spaced apart from one another along the horizontal extension of the attenuation tube 116.

Thus, advantageously, additional microwave attenuation for the channels may be accomplished by at least one coaxial filter 124. More precisely, according to fig. 6 and 7, the attenuation tube 116 is designed integrally with the coaxial filter 124.

According to fig. 6, there is no electrically conductive liquid 106 in the lumen of the fluid line 104, so that the attenuator tube 116 is again effective to suppress microwave propagation in the outer portion 110.

However, according to fig. 7, the attenuation tube 116 alone loses its sufficiently strong microwave attenuation properties when there is conductive fluid 106 in the form of a conductive liquid in its cross-section (i.e., within a non-conductive hose or tube). Viewed in cross-section, a configuration of coaxial conductors of fluid is created, whereby it is possible to propagate microwave energy along the transmission section.

For a geometrically constant inner conductor formed by the conductive fluid 106, the coaxial filter 124 ensures that strict limit values are maintained, wherein the coaxial filter is dimensioned for attenuation of microwave frequencies propagating through the conductor having a cross section of the fluid film.

Thus, as the conductivity of the conductive fluid 106 increases, the attenuation tube 116 alone loses its sufficiently strong microwave attenuation function. Illustratively, the electrically conductive fluid 106 in the attenuation tube 116 becomes an electrical conductor. Starting from a certain order of magnitude of the electrical conductivity, the cross section of the conductor becomes the decisive dimension. The fluid line may be regarded as a conductor, which corresponds to the diameter of the filled tube cross-section, whereby microwave radiation may propagate in the resulting coaxial arrangement. The fluid line 104 may be formed from a microwave transparent and solvent or acid resistant material (e.g., PTFE, ceramic, quartz, etc.).

Advantageously, the configuration of the coaxial filter 124 can be selected to match the medium to be transported, the hose material used, the necessary channel cross-section (and thus the mass flow rate) and the like. For this configuration, the length and diameter of the attenuator tube 116 and the coaxial filter 124 may be calculated. In this case, the dielectric constant of the materials used and the medium to be transported, as well as the desired temperature, can also be taken into account. The dielectric constants of many materials are closely related to temperature, and thus the wavelength of microwave radiation varies with temperature. Thereby, the zero point of the bezier function also changes. For example, at a given lowest conductivity (and thus maximum penetration depth), the combination of the coaxial filter 124 and the attenuation tube 116 is designed or optimized for a particular operating frequency. This dimensioning can be done in a simple manner for the frequency of the microwaves used (for example 2.45GHz, which can be produced by means of a magnetron) and the cross-sectional area of the hollow conductor (i.e. the diameter of the microwave-transparent tube). Such dimensioning may be related to attenuation of the geometrically constant inner conductor. If the fluid cross-section is always the same, it is possible to simply design the coaxial filter 124. Advantageously, the design or configuration of the coaxial filter 124 may be accomplished repeatedly. The geometry and the conductivity or the resulting penetration depth can be adapted to the actual application with suitable simulation tools. An appropriate simulation program is, for example, Ansys HFSS/CST/Comsol.

Advantageously, with a proper design of the coaxial filter 124, it can be ensured that no stray radiation or insignificant stray radiation escapes.

An axial filter in the form of a coaxial filter 124 may be positioned before or after the attenuator tube 116, but may also be positioned perpendicular thereto along the attenuator tube axis. The entire damping tube section can therefore also be implemented in sections.

The microwave device 100, which is designed as a microwave oven, with a rectangular cavity and magnetron microwave radiation of 2.45GHz, can be equipped, for example, with an attenuation tube 116 of 60mm in length and 20mm in diameter and with a built-in PTFE hose as the fluid line 104. An axial air filter adapted to this, having a radius of the air gap of 40mm and a width of the air gap of 9.5mm in the filter, achieves an excellent damping effect for the exclusion of different acids. In this design, the coaxial filter 124 may be made of aluminum, for example, with an air gap serving as the dielectric medium. However, other dielectric materials may be used in this regard. This may make the coaxial filter 124 more compact in geometry, since a lower expansion is sufficient for a constant wavelength. On the other hand, however, air is a medium whose temperature dependence of dielectric constant is very low. In modeling or designing the coaxial filter 124, the strength and dielectric properties of the fluid-conducting tube are preferably also taken into account.

Filling the output section only partially with the conductive fluid 106 changes the geometry or cross-section of the conductive channel or inner conductor. In such unfavorable cases, there is a possibility that asymmetry will occur with respect to the coaxial filter 124, and the attenuation effect will be reduced. In such unfavorable cases, for example, a combination of a plurality of coaxial filters 124 completes the remedial action. Advantageously, these coaxial filters should be arranged at a sufficient distance from each other in order to inhibit mutual influence. Too close an arrangement may result in reflection and interaction of radiation between the coaxial filters 124.

An advantage of the embodiments according to fig. 6 and 7 is that an uninterrupted, microwave transparent and acid and solvent resistant fluid line 104 is provided. No complicated seals are required and corrosive chemicals can also be used as the conductive fluid 106 (e.g. acid).

Fig. 8 illustrates, in a schematic cross-sectional view, a microwave device 100 according to yet another exemplary embodiment of the present invention, wherein the fluid line 104 is devoid of the electrically conductive fluid 106. Fig. 9 illustrates a state of the microwave device 100 according to fig. 8, in which a quantity of the electrically conductive fluid 106 is transferred from the interior 108 to the exterior 110 of the microwave cavity 102 of the microwave device 100 and/or in a reverse flow direction. Fig. 10 illustrates a state of the microwave device 100 according to fig. 8 in which a smaller amount of the electrically conductive fluid 106 is transferred between the interior 108 and the exterior 110 of the microwave cavity 102 of the microwave device 100 than in the state according to fig. 9. Fig. 11 illustrates a state of the microwave device 100 according to fig. 8 in which a larger amount of the electrically conductive fluid 106 is transferred between the interior 108 and the exterior 110 of the microwave cavity 102 of the microwave device 100 than in the states according to fig. 9 and 10.

Advantageously, the microwave device 100 according to fig. 8 to 11 comprises a constriction 130 for selectively constricting the cross-section of the fluid line 104, through which the fluid 106 may flow, within the scope of the coaxial filter 124. The narrowest position of the constriction 130, having the lowest lumen diameter, is shown by reference numeral 150. In other words, the constriction 130 ensures that the lumen through which the conductive fluid 106 flows is narrower at the axial location of the coaxial filter 124 than in other regions of the fluid line 104. As shown in fig. 8, the inner diameter D within the lumen of the constriction 130 is smaller than the inner diameter D of the lumen of the fluid line 104 (D < D).

Thus, fig. 8-11 illustrate an embodiment of a microwave apparatus 100 comprising an attenuation tube 116 having a coaxial filter 124 and a compensation section for balancing different filling states of a fluid line 104 filled with an electrically conductive fluid 106. This compensation segment is accomplished by selectively providing a constriction 130 within the confines of the in-line filter 124, by constricting the fluid line 104 segment by segment.

According to fig. 8, the attenuation tube 116 is effective in attenuating microwaves that undesirably escape only when the conductive fluid 106 is not present in the lumen of the fluid line 104.

Fig. 9 to 11 show different filling states of the fluid line 104 filled with the electrically conductive fluid 106. Most critical is the mode of operation according to fig. 10, in which only a small amount of the electrically conductive fluid 106 is located in the fluid line 104, but the electrically conductive fluid 106 still forms a coherent electrically conductive connection. The constrictions (see constriction 130) integrated in the fluid line 104 in the section of the coaxial filter 124 may limit the geometrical variability (diameter and/or axial displacement) of the conductive liquid to the region outside the coaxial filter 124, thereby always ensuring the effectiveness of the coaxial filter 124 with respect to microwave tightness requirements.

By the described throttling it is ensured that the axial filter in the form of the coaxial filter 124 sees a section that is geometrically the same all the time. At the same time, the stepwise tapering within the constriction 130 results in an increased flow velocity.

When the conductive fluid 106 does not completely fill the fluid line 104 (see fig. 9 and 10), axial displacement may occur without the constriction 130, particularly under liquid test piece conditions. The geometry is thus no longer correct in the circumferential direction. The in-line filter 124 is no longer effective because the best attenuation results for rotational symmetry. In other words, the liquid filling of the fluid line 104 should be circumferentially identical within the scope of the coaxial filter 124 for optimum damping effect. In the embodiment according to fig. 8 to 11, this is advantageously sufficiently close in geometry by the constriction 130 that, even when the fluid line 104 is only slightly filled with the electrically conductive fluid 106 (see fig. 9 and 10), the constriction ensures that, within the scope of the coaxial filter 124, the entire cross section of the lumen of the constriction 130 remains filled with the electrically conductive fluid 106, or at least that the axial displacement, by a lower filling amount, has only a minor effect on the filtration efficiency of the axial filter. Thereby, it is ensured that the microwave radiation is sufficiently effectively attenuated in the exterior 110 of the microwave cavity 102 even in the described critical operating mode.

Fig. 12 illustrates in a schematic cross-sectional view a microwave device 100 according to a preferred embodiment of the present invention, wherein the fluid line 104 is devoid of the electrically conductive fluid 106. Fig. 13 illustrates a state of the microwave device 100 according to fig. 12 in which a small amount of the electrically conductive fluid 106 is transferred from the inside 108 to the outside 110 of the microwave cavity 102 of the microwave device 100 and/or in the opposite direction. Fig. 14 illustrates a state of the microwave device 100 according to fig. 12 in which a larger amount of the electrically conductive fluid 106 is transferred between the interior 108 and the exterior 110 of the microwave cavity 102 of the microwave device 100 than in the state according to fig. 13.

According to fig. 12 to 14, in order to suppress parasitic microwave emissions in the outer portion 102 due to the formation of a coaxial arrangement between the attenuating structure 112 and the electrically conductive fluid 106 in the fluid line 104, the device 114 comprises an electrically conductive insert 132, which is selectively fitted into the fluid line 104 within the scope of the coaxial filter 124. As shown, the insert 132 is in contact on the inside with the fluid 106 flowing through the fluid line 104. Furthermore, the insert 132 is surrounded on the outside by the fluid line 104 and is thereby electrically isolated from the coaxial filter 124 and the attenuating structure 112. The insert 132 may be designed as a pipe joint 122. The pipe joint 122 is formed of graphite, conductive polymer, conductive ceramic, or conductive metal, for example. Thus, the embodiment according to fig. 12 to 14 provides an attenuation tube 116 comprising a coaxial filter 124 and a non-electrically contacting compensation element in the form of an insert 132. This embodiment shows excellent properties in suppressing the emission or propagation of unwanted microwave radiation in the outer portion 110 of the microwave cavity 102.

According to fig. 12, the fluid line 104 does not contain any electrically conductive fluid 106, and the separate attenuator tube 126 again effectively attenuates undesirable microwave radiation in the outer region of the microwave cavity 102.

According to fig. 13 and 14, different amounts of conductive fluid 106 are present in the fluid line 104. In the case where the inner conductor is formed of a conductive liquid, the effectiveness of the coaxial filter 124 may be compromised without the insert 132 if the inner conductor cross-section of the fluid 106 varies in geometry (particularly in terms of diameter and/or axial displacement) within the section of the coaxial filter 124.

Independent of the change in geometry, an electrically conductive, tubular (or more generally preferably rotationally symmetric) element in the form of an insert 132 wetted by the electrically conductive fluid 106, which may also be referred to as a compensation element, as part of the fluid line 104 in the section of the coaxial filter 124, maintains the necessary geometry for the effectiveness of the coaxial filter 124 through the fluid.

In particular in the case of corrosive media or electrically conductive fluids 106, it is advantageous if the electrically conductive tubular insert 132 is present as part of the fluid line 104 and therefore does not require any sealing measures (e.g. O-rings) against it.

The preferred material for the compensating element or insert 132 has an electrical conductivity that is compatible with corrosion resistance (e.g., graphite, ceramic, etc.).

In particular, with such an insert 132 it is also possible in a simple manner to pass a plurality of fluid lines 104 simultaneously through a single damping tube 116 (not shown).

In particular, the embodiments according to fig. 12 to 14 have the additional advantage that there is substantially no restriction with respect to the flow rate supported by the electrically conductive fluid 106 to be transmitted through the fluid line 104.

Many modifications to the embodiments shown in the drawings are possible. For example, an off-horizontal orientation (e.g., vertical or inclined) of fluid line 106 is also possible.

It is additionally noted that "comprising" does not exclude any other elements or steps and "a" or "an" does not exclude a plurality. Furthermore, it is to be noted that features or steps which have been described with reference to one of the above embodiments may also be used in combination with other features or steps of other embodiments described above.

Claims

1. A microwave device (100) comprising:

a microwave cavity (102) in which microwaves can be emitted and/or generated;

an at least partially electrically insulated fluid line (104) for conducting an electrically conductive fluid (106) between an interior (108) and an exterior (110) of the microwave cavity (102);

an at least partially electrically conductive attenuation structure (112) surrounding the fluid line (104) at least section by section, the attenuation structure being for attenuating microwaves in an exterior (110) of the microwave cavity (102); and

additional means (114) for suppressing microwave emissions into the exterior (110) of the microwave cavity (102) due to a coaxial arrangement formed between the attenuating structure (112) and an electrically conductive fluid (106) located in the fluid line (104).

2. The microwave device (100) according to claim 1, wherein the fluid line (104) extends through a wall (118) defining the microwave cavity (102).

3. The microwave device (100) according to claim 1 or 2, wherein the attenuating structure (112) comprises an attenuating tube (116) penetrated by the fluid line (104), which attenuating tube is connected to a wall (118) defining the microwave cavity (102), in particular on an end side, or is integrally formed with the wall (118).

4. The microwave device (100) according to any one of claims 1 to 3, wherein the means (114) are designed to interrupt the flow of the fluid (106) along the fluid line (104) segment by segment.

5. The microwave device (100) according to claim 4, wherein the means (114) comprise a dripping section (120), in particular vertical, at which fluid (106) escaping from a first section (140) of the fluid line (104) can be converted into a series of fluid droplets (122) spaced apart from one another, in particular falling vertically down, before entering a second section (142) of the fluid line (104).

6. The microwave device (100) according to claim 4 or 5, wherein the apparatus (114) is designed to modify a flow direction of the fluid (106) flowing through the fluid line (104) within the scope of the apparatus (114), in particular horizontally, in particular modified to a flow direction that is vertical within the scope of the apparatus (114).

7. The microwave device (100) according to any one of claims 1 to 6, wherein the arrangement (114) is designed to electrically short the electrically conductive fluid (106) flowing along the fluid line (104) to the attenuating structure (112) at least segment by segment, in particular directly or indirectly.

8. The microwave device (100) according to claim 7, wherein the arrangement (114) comprises a pipe connection (122) electrically coupled with the attenuating structure (112) and electrically conductive, in particular highly thermally conductive, which is arranged between a first section (140) and a second section (142) of the fluid line (104) and which makes contact with the fluid (106) when the electrically conductive fluid (106) flows through the fluid line (104).

9. The microwave device (100) according to any one of claims 1 to 8, wherein the arrangement (114) comprises an electrically conductive coaxial filter (124) for additional microwave attenuation.

10. The microwave device (100) according to claim 9, wherein the coaxial filter (124) is designed integrally with the attenuating structure (112).

11. The microwave device (100) according to claim 9 or 10, wherein the coaxial filter (124) encloses the fluid line (104) outside the microwave cavity (102).

12. The microwave device (100) according to any of claims 9 to 11, wherein the coaxial filter (124) is designed as a circumferentially closed disc (126) comprising a hollow core (128) or dielectric core centrally penetrated by the fluid line (104).

13. The microwave device (100) according to any one of claims 9 to 12, wherein the arrangement (114) comprises at least one further electrically conductive coaxial filter (124) for additional microwave attenuation, in particular according to any one of claims 9 to 12.

14. The microwave device (100) according to any of claims 9 to 13, comprising a constriction structure (130) for selectively constricting a cross-section of the fluid line (104) traversable by the fluid (106) within a range of the coaxial filter (124).

15. The microwave device (100) according to any of claims 9 to 14, comprising an electrically conductive insert (132) selectively loaded into the fluid line (104) within the scope of the coaxial filter (124).

16. The microwave device (100) according to claim 15, wherein the insert (132) is in contact on an inner side with a fluid (106) flowing through the fluid line (104).

17. The microwave device (100) according to claim 15 or 16, wherein the insert (132) is surrounded on the outside by the fluid line (104) and thereby electrically isolated from the coaxial filter (124) and/or the attenuating structure (112).

18. The microwave device (100) according to any one of claims 15 to 17, wherein the insert (132) is designed as a pipe joint (122).

19. The microwave device (100) according to any one of claims 1 to 18, designed as one of the group consisting of a microwave synthesis reactor, a microwave analyzer, a microwave oven, a microwave synthesizer, a microwave digestion instrument, a microwave extraction instrument, a microwave evaporator and a microwave dryer.

20. A method of suppressing the escape of microwaves to the outside (110) of the microwave cavity (102) of a microwave device (100), the method being used in the process of conducting an electrically conductive fluid (106) between the inside (108) and the outside (110) of the microwave cavity (102) by an at least partially electrically insulated fluid line (104), the microwave cavity containing and/or generating microwaves, wherein the method comprises:

conducting the electrically conductive fluid (106) between an interior (108) and an exterior (110) of the microwave cavity (102) by the fluid line (104);

-attenuating the microwaves in the exterior (110) of the microwave cavity (102) by means of an electrically conductive attenuating structure (112) surrounding the fluid line (104) at least section by section; and is

Additional measures are taken to suppress microwave emissions into the exterior (110) of the microwave cavity (102) due to a coaxial connection formed between the attenuating structure (112) and the electrically conductive fluid (106) located in the fluid line (104).

21. The method according to claim 20, wherein the electrically conductive fluid (106) is an electrically conductive liquid, in particular an acid and/or salt solution.

22. The method according to claim 20 or 21, comprising one of the following features:

the electrically conductive fluid (106) completely fills the cross-section of the fluid line (104);

the electrically conductive fluid (106) only exactly partially fills the cross section of the fluid line (104);

there is no electrically conductive fluid in the fluid line (104).