EP3236711B1 - Method and device for the non-invasive dielectrical heating of solids - Google Patents

Description

The invention relates to a method and a device for the non-invasive dielectric heating of solids. In particular, the present invention relates to a method and a device for the thermal treatment of an extensive solid-state structure by means of high-frequency energy, wherein for contacting at least one component acting as an electrode, a capacitive coupling without constructive connections that conduct electrical direct current is realized through the solid.

Technological background of the invention

The release of unwanted substances such as water or contaminants from solids and in particular from building materials such as masonry, natural stone, brick, concrete or wood can be significantly accelerated by a controlled temperature increase in the material. The reasons for this can be an increase in the vapor pressure and the rate of diffusion with the temperature or the evaporation of the foreign matter with sufficient heating. Dehumidification is significantly accelerated by the evaporation of pore water and the thermally assisted desorption of adsorbed water, especially if an optimal water removal away from the surface is ensured by suitable supporting measures. This applies analogously to chemicals such as mineral oil hydrocarbons, solvents and wood preservatives, which can be contained in solids as undesired contamination. A combination of water and chemical discharge can lead to an effective form of decontamination if the chemical discharge is supported by the formation of water vapor and the associated generation of an inherent transport flow out of the pore space. This process, known as stripping, corresponds to a steam distillation as is known from chemical process engineering and from soil remediation supported by high-frequency heating [ U. Roland et al., Environ. Sci. Technol. 44 (2010) 9502 ].

The need to remove water and / or chemicals from materials such as building materials can arise from a variety of causes. Acute events can lead to flooding of buildings or water damage, which may also result in contamination with heating oil due to leaks in heating systems. The use of toxic chemicals, for example for wood protection, can lead to an unacceptable pollution of the room air, so that decontamination is necessary. Finally, planning and execution errors can lead to moisture damage, which in turn can lead to energy and health problems, for example due to mold formation. In the construction sector, the boundary conditions for a renovation result on the one hand from constructive aspects (access on one or both sides, affected materials, geometry, etc.), but on the other hand also from aspects of intrinsic value and monument preservation. As a rule, there is a special need for non-invasive procedures that interfere and damage the building structure as little as possible.

If necessary, the remedial measures must naturally be supplemented by activities that prevent rewetting or contamination. These can be horizontal barriers, for example, which are realized by introducing a polymer-forming substance into masonry. The prerequisite for this is the provision of free pore volume in the material, which often also requires prior dehumidification.

In addition to the removal of chemicals, decontamination in the sense of this description of the invention can also be understood to mean that pests and in particular wood pests are killed or at least damaged by the treatment by reaching a certain temperature in the material. The lethal temperatures required for killing depend on the respective organisms and their stages of development, but can also be influenced by parameters such as material moisture and duration of the treatment. Although in most cases the destruction of wood pests can be justified by thermal effects [ S. Steinbach et al., Protect & Preserve (2012) 29 ; C. Hoyer et al., Chemical Engineer Technology 86 (2014) 1187 ], selectivity effects are also discussed in the literature which allow the pests to be killed at lower temperatures of the matrix surrounding the pest in comparison with the lethal temperature [ SO Nelson, Trans. Am. Soc. Agricult. Closely. 39 (1996) 1475 ]. However, this distinction is not relevant for use in the context of the invention.

An increase in the temperature in materials to be treated and in particular in building materials that are integrated into a structure can be achieved by various methods will. The introduction of heating rods into boreholes is technically relatively simple, but there are strong temperature gradients in the vicinity of the heating rods. This is particularly the case when dry materials have a low thermal conductivity. However, the mechanical damage to the treated structure is particularly disadvantageous, which is often unacceptable, particularly in the area of listed buildings, and also necessitates subsequent renovation for other applications. The aim is therefore to use non-invasive procedures, which will be discussed in more detail below.

The surface of the material is heated by infrared radiation, and the very small penetration depth of the infrared radiation means that the interior of the solid has to be heated by heat conduction. As a result, high temperature gradients with overheating of the surface can be expected. Irradiated and thus heated areas of less than one square meter are typical for this process. Furthermore, it can have a disadvantage that the irradiated infrared energy is partially absorbed by the escaping water vapor and thus there is a loss of effectiveness with regard to the heating of the surface during drying. The same applies to the use of heated blankets or hot plates. Even when the room is heated with hot gas, the heat is transported from the surface. The heat transfer into the interior of the material, which is decisive for the treatment of the volume, does not depend on how the increased surface temperature is established (infrared, heating plates or hot gas).

Another, partly already established method for non-invasive heating is dielectric heating with microwaves with frequencies in the gigahertz (GHz) range [ EP 1 374 676 B1 ]. The warming here is preferably linked to the presence of water molecules, since these are reoriented as dipole molecules in an external field and impart warming through interactions with their environment due to internal friction losses. Some dry building materials can therefore practically not be heated using this method. Non-polar hydrocarbons (eg mineral oil components) are also unsuitable for imparting energy. Characteristic of microwave heating are the mostly shallow penetration depths in the centimeter range for most building materials, which lead to large temperature gradients with the corresponding disadvantages for the treatment. This harbors the risk that the temperatures required for the relevant processes of drying, decontamination or killing of pests will not be reliably achieved in the entire volume.

An innovative direct heating method, the principle of which is similar to that of microwave heating, is dielectric heating using radio waves, ie electromagnetic waves in the radio frequency range of a few megahertz (MHz) [ DE 20 2008 012 371 U1 ]. This method of volumetric heating achieves significantly more homogeneous temperature profiles due to a much greater depth of penetration into the materials in the meter range. This means that masonry made of different materials can generally be treated well thermally. According to the prior art, however, it is as in DE 20 2010 001 410 U1 described, necessary to attach electrodes on both sides of a flat structure and to contact them. If there are no natural openings, holes must be made in the wall to be heated, through which electrically conductive means for contacting must be made. Although this method is already much gentler than an invasive method such as the introduction of heating elements, damage to the building structure to be treated must be accepted. Under certain circumstances, this can considerably limit the applicability of radio frequency heating, despite its advantages, particularly in the area under monument protection. In addition, with the conventional arrangement, it is more difficult to treat the wall or other solid structures to be treated successively, since both electrodes usually have to be moved while maintaining the described contacting and while ensuring adequate electromagnetic shielding, which also means that the masonry has to be drilled several times would require.

It is therefore an object of the present invention to provide a method and a device which takes up the advantages of radio frequency heating mentioned with regard to the range of use and homogeneity of the temperature profiles and thereby overcomes the disadvantages of the prior art described, as a result of which the use potential of radio waves is increased -Technology significantly increased for the named and other applications. With the method and the device according to the present invention, it should be possible, in a non-invasive manner, practically without damaging the material and the structure, arrangements of materials such as e.g. Efficiently thermally drying and / or decontaminating stone, concrete, brick or wood, whereby both chemical and biological contamination can be eliminated. The invention is intended to make it possible to successfully treat so-called one-sided structures that are only accessible from one side, according to the principles mentioned.

DE 94 13 736 U1 discloses a microwave drying and pest control system in which the effectiveness of high-frequency alternating fields is exploited. Out EP 0 581 815 A1 are a method to prevent and control fungal infestation in building structures and electrodes for carrying out the method are known. FR1 151 084 A relates to an electrode system for dielectric loss heating and in particular to a system in which two electrodes are arranged next to one another on one side of a volume to be heated and a counter electrode is located on the opposite side.

Summary of the invention

According to the invention, these objects are achieved by the independent claims. Preferred embodiments of the invention are contained in the subclaims.

The method according to the invention for the dielectric heating of solids comprises providing at least one live electrode and at least one shielding electrode on a first side of a solid and at least one coupling element on a second side of the solid, the first side of the solid and the second side of the solid being opposite one another . Furthermore, the area ratio between the overlap area between the surfaces of the at least one coupling element and the at least one shielding electrode and the surfaces of the at least one live electrode is adjusted, the area ratio being greater than 3: 1. Furthermore, the at least one coupling element is at least partially capacitively coupled to the at least one shielding electrode. Furthermore, the method comprises applying a high-frequency voltage to the at least one live electrode, the high-frequency voltage having a frequency in the range between 500 kHz and 500 MHz.

The method for the dielectric heating of solids with high-frequency energy is preferably characterized in that the solid is at least partially arranged between at least one live, so-called hot electrode and at least one coupling element, and in that the coupling element has a shielding electrode which is located on the side of the hot electrode is capacitively coupled, so that a high-frequency electric field builds up in the solid between the hot electrode and the coupling element, which leads to the heating of the solid.

The applied electrical field can preferably have a high frequency in the range between 500 kHz and 500 MHz, likewise preferably between 1 and 50 MHz and particularly preferably an ISM frequency in this range, for example 13.56 MHz or 27 MHz, which is approved for industrial, medical and research applications , exhibit.

The idea of the present invention is to thermally treat a solid body made of a solid and in particular a building structure with the aid of a capacitive coupling in such a way that it is not necessary to conduct electrically conductive connections for contacting through the solid body structure or past it. The thermal treatment is preferably associated with a significant increase in temperature which allows water and / or pollutants to be removed from the solid more efficiently and / or to kill harmful organisms present in the solid by exceeding a lethal temperature and / or irreversibly damaging them. The method according to the invention is particularly suitable for the treatment of structures which have planar surfaces which are arranged parallel to one another. One example of this is brick or concrete walls in buildings.

In contrast to the effect of capacitive coupling, which has to be considered in connection with electromagnetic compatibility [ AJ Schwab, Electromagnetic Compatibility, Springer Verlag 1996, ISBN 3-540-60787-0 ], this instrument is used for targeted energy input in the case of the invention. From the aspect of electromagnetic compatibility, capacitive coupling leads, for example, to undesired coupling of high-frequency voltages into lines lying in parallel. It can also be used deliberately to transmit high-frequency voltages at different DC voltage levels. In both cases, despite the use of the same term, the applications differ very clearly from the method according to the invention, in which this principle is used to implement dielectric heating by means of an energy input.

The implementation of the method according to the invention is preferably implemented with an arrangement in which there is a live flat electrode on one side of the structure in the area of the structure that is preferably to be heated (hot electrode), and an extended grounded and electrically conductive electrode (shielding electrode) on the same side. , which can act as a shield and which is usually extended a few centimeters above the hot electrode, is arranged and on the other side of the structure to be treated there is a coupling element which acts as an electrode and is capacitively coupled to the first two components . The coupling element is located at the position of a "cold" electrode in the conventional two-electrode arrangement (cf. for example DE 20 2010 001 410 U1 ). The field strength of the high-frequency field between the coupling element and the hot electrode is preferably particularly high, which leads to a heating especially between the hot electrode and the coupling element. In a Particularly preferred arrangement, the hot electrode is completely spanned by an electrically conductive structure which acts as a shield and which acts as a shielding electrode, so that the electromagnetic radiation into the surroundings is minimized. The at least one coupling element preferably comprises an electrically conductive coupling electrode, wherein the coupling electrode can comprise a metallic material.

It is preferred that a preselected heating regime takes place by adapting the introduced HF power to at least one temperature measured in the volume. It is also preferred that the drying of the solid is accelerated by the temperature increase. It is also preferred that the discharge of pollutants from the solid is accelerated by the temperature increase. It is also preferred that the discharge of the pollutants is supported by the discharge of water vapor. It is particularly preferred that the temperature increase leads to destruction and / or impairment of the viability of wood pests.

In the method according to the invention, the heating is achieved without direct contacting in that a capacitive coupling takes place between the shielding electrode and the coupling element. Put simply, this means indirect contacting of the coupling element, which can then functionally function similarly to a cold electrode in conventional arrangements according to the prior art. The shielding electrode is preferably grounded, for example by being electrically conductively connected to the housing of an upstream electronic matching network, a so-called matchbox. The capacitive coupling thus means that the potential difference between the shielding electrode and the coupling element is small compared to the potential difference between the coupling element and the "hot" electrode. For solid structures with sufficient homogeneity, for example, this results in a significantly higher electrical field strength between the hot electrode and the coupling element than between the shielding electrode and the coupling element. As is known, this leads to greater dielectric heating between the hot electrode and the coupling element in comparison to the volume away from the hot electrode. In particular, embodiments are preferred in which the high-frequency voltage is generated by a high-frequency generator and the power reflected back from the at least one live electrode to the high-frequency generator is minimized by an electronic matching network. In a preferred implementation of the method and the device, the capacitive coupling between the shielding electrode and the coupling element is implemented partially or completely by a material that is different from the material to be preferably heated between the hot electrode and coupling element differs in terms of its electrical properties. It is further preferred that the respective materials or substances between the hot electrode and the coupling element and between the shielding electrode and the coupling element differ completely or partially from one another.

A dielectric heating of solid-state structures according to the invention is thus also possible if one side of the capacitor arrangement produced, which contains the solid to be heated, has no (direct) electrical direct current-conducting contact. This even applies if the coupling element is not an electrode in the actual sense, but if a naturally occurring medium such as a moist floor takes over this function. This is particularly relevant in the context of applications in construction. This can be, for example, the drying and / or decontamination of chemically or biologically contaminated masonry or other building materials. Structures that are accessible from one and both sides can thus be thermally treated. It is preferred, inter alia, in the application context mentioned that the at least one coupling element is formed by or comprises a natural compartment (environmental compartment). In particular, no metallic or electrically conductive coupling electrodes are required. The natural compartment is preferably pending or filled soil.

In a preferred embodiment of the method according to the invention for single-sided problem cases, the capacitively coupled counter electrode (coupling electrode), which is located opposite the "hot" electrode, is made available by a natural structure. This can be, for example, an existing floor with sufficient high-frequency conductivity so that this natural electrode can act as a coupling element and approximately forms an equipotential surface. A typical example of this with such a one-sided arrangement in the basement area of buildings is moist soil. The capacitive coupling is possible in that, at the frequencies used, the solid to be treated, which acts as a capacitor between the electrodes arranged on both sides, has sufficient dielectric conductivity, which significantly reduces the potential difference between the shielding electrode and the coupling element on the opposite side.

In a preferred variant in use, the properties of the natural compartment are specifically varied so that it can better fulfill the function as a coupling element. A typical preferred option in this sense is the humidification of ground to improve its electrical conductivity and thus its effect as an electrode-equivalent coupling element. The corresponding moistening can be carried out continuously if required or repeated several times.

In certain situations, the materials for the different areas of the solid structure to be treated can also differ or be spatially separated from one another. For example, the material to be preferably heated between the hot electrode and the coupling element can differ from the material by which the capacitive coupling is implemented in the manner described.

For the function of the method according to the invention, it is generally necessary that the overlapping area between the shield and the "cold" electrode on the opposite side is significantly larger than the area of the "hot" electrode. The corresponding ratio is preferably greater than 4: 1, particularly preferably at least 8: 1. In this case, a preferred heating of the volume which is located between the hot electrode and the coupling element is to be expected. The corresponding area ratio depends on the specific material and geometric conditions and, if necessary, can be determined experimentally or by means of a model calculation. The area ratio between the hot electrode and the overlap area of the shielding electrode and the oppositely arranged coupling element is preferably set such that the heating preferably takes place in the volume between the hot electrode and the coupling element.

However, it is also possible to choose the ratio of the areas of the shielding electrode and the hot electrode in such a way that a specific ratio of the heating rates in both volume ranges (between the hot electrode and the coupling element or between the shielding electrode and the coupling element) is set, which for the procedural sequence can be advantageous. For example, it can be achieved that the colder area of the solid structure does not fall below a temperature that would lead to recondensation of evaporated substances such as water or chemicals. It is preferred that the method according to the invention, for the purpose of maximum heating of the area between the at least one live electrode and the at least one coupling element, furthermore the setting of the area ratio between the overlap area between the surfaces of the at least one coupling element and the at least one shielding electrode, and the Surfaces of the at least one live electrode. In particular, area ratios of greater than 3: 1, greater than 6: 1 and greater than 10: 1 are special prefers. A preselected ratio of the heating rates inside and outside the range between the at least one live electrode and the at least one coupling element can preferably be set via the area ratio. The ratio of the overlap areas of the hot electrode and the coupling element or of the shielding electrode and the coupling element can preferably be selected such that a predefined ratio of the heating rates in the solid to be treated is realized in the areas between the hot electrode and the coupling element or between the shielding electrode and the coupling element.

The method according to the invention is based on direct dielectric heating of the material, an element acting as an electrode, the coupling element, being capacitively and not directly electrically connected to the RF voltage source via the shielding electrode. For this purpose, a high-frequency alternating electric field is applied in such a way that a field is established in the solid that leads to the reorientation or other movement of polar structures in the solid. Their reorientation or movement is associated with frictional losses due to the interaction with their environment, which leads to heating in the volume. While the orientation polarization of the water molecule in the MHz range, in contrast to the GHz frequency range for microwaves, does not lead to efficient energy coupling and thus heating, processes of ion mobility, for example, can lead to very efficient heating in the MHz frequency range. For this reason, it is also possible to heat dry materials efficiently in the frequency range used. The mechanisms of energy coupling that underlie dielectric heating can be found in the specialist literature. For the implementation of the method according to the invention, it is irrelevant which physical operating principle the dielectric heating is based on. By implementing the advantages of radio wave heating, the method according to the invention permits a comparatively homogeneous heating of building structures even if it is not possible to pass electrical lines through the structure or if the structure is only accessible from one side because, for example, the soil is closed heating structure limited on the side facing away from the hot electrode.

The large number of processes that enable dielectric energy input for the individual substances, ie absorption of energy in the high-frequency range, brings with it a high degree of flexibility with regard to the materials to be treated. Dry and moist, porous and non-porous materials can be heated with high efficiency. Examples from the construction sector include natural stone, brick masonry, concrete or wood. This closes if necessary, intermediate and top layers such as mortar joints and plaster surfaces. However, the method according to the invention can also be transferred to other areas of process engineering. In principle, the solid structure to be heated can also be a component made of plastic or ceramic or a pouring bed made of different materials such as adsorbents or catalysts. Further applications with other materials are expressly not excluded.

The borderline case of an ideal capacitive coupling would only be reached if the ratio of the overlapping areas of shielding electrode and coupling element on the one hand and hot electrode and coupling element on the other hand were infinitely large. In real use, the electrical field strength, which is relevant for the heating rate, is not zero due to the finite area ratio between the shielding electrode and the coupling element arranged opposite. However, since the heating rate is proportional to the square of the electric field strength, a clearly preferred heating in the area of the “hot” electrode can easily be achieved by choosing area ratios above 5 or even 10. For example, for a very extensive coupling element with an area that covers the entire area, this means that the shielding electrode must be significantly larger than the hot electrode, which can generally be implemented without problems.

From a procedural point of view, however, it can be advantageous to carry out a moderate heating in the vicinity of the zone of the solid body that is actually to be heated, parallel to the heating between the hot electrode and the coupling element. For example, undesired recondensation of compounds emerging from the hot zone, such as water and pollutants, can be prevented. Reduced temperature gradients also reduce the heat flow from the directly heated area. Lower temperature gradients are also associated with smaller mechanical stresses in the material, which can reduce the risk of damage, for example due to crack formation. A variant of the method according to the invention can therefore fall back on reduced or defined area ratios in the above-mentioned sense in order to specifically coordinate the heating rates in the actual target area and in the adjacent wall area.

Another aspect of the present invention relates to a device for the dielectric heating of solids, which preferably has at least all those features which are necessary for carrying out the individual method steps of the described Procedure are required. A device for the dielectric heating of solids comprises a live electrode; a shielding electrode, wherein the live electrode and the shielding electrode can be arranged on a first side of a solid, and the shielding electrode is capacitively coupled to a coupling element on a second side of the solid during operation, the first side of the solid and the second side of the solid oppose; and a means for applying a high-frequency voltage, designed to apply a high-frequency voltage with a frequency in the range between 500 kHz and 500 MHz to the live electrode, the area ratio between the overlap area between the surfaces of the at least one coupling element and the at least one shielding electrode, and the surfaces of the at least one live electrode is greater than 3: 1.

In particular, a preferred embodiment of a device according to the invention for the dielectric heating of solids can have a voltage-carrying electrode which is extended over a large area and has a main plane; a flat shield electrode with a main plane, the main plane of the shield electrode being aligned parallel to the main plane of the live electrode; and a means for applying a high-frequency voltage, designed to apply a high-frequency voltage with a frequency in the range between 500 kHz and 500 MHz to the live electrode; include. This embodiment of the device is characterized in that the projection of the voltage-carrying electrode onto the shielding electrode completely overlaps the shielding electrode along an axis perpendicular to the main plane of the voltage-carrying electrode, the minimum distance between the voltage-carrying electrode and the shielding electrode preferably at least 1 cm, likewise preferably at least 10 cm, more preferably at least 20 cm, and the projected area ratio between the surfaces of the shielding electrode and the live electrode is preferably greater than 3: 1, also preferably greater than 6: 1, still preferably greater than 10: 1.

For this consideration, a surface of the shielding electrode results from that surface region of the shielding electrode which lies flat on the solid to be heated or which is largely adjacent to its surface. In a preferred embodiment variant, the surface of the shielding electrode is the maximum area defined within the main plane by the dimensions of the shielding electrode and lies in one plane with the live electrode. The Live electrode and the main plane of the shield electrode are preferably parallel to each other, so that projection of the live electrode on the main plane of the shield electrode completely overlaps with the shield electrode.

Furthermore, this embodiment of the device for the dielectric heating of solids preferably comprises a coupling element, a receiving space for a solid to be heated being formed between the voltage-carrying electrode and the coupling element; the live electrode and the shielding electrode are arranged on a first side of the accommodating space and the coupling element is arranged on a second side of the accommodating space, the first side of the accommodating space and the second side of the accommodating space being opposite one another; the coupling element is at least partially capacitively coupled to the shielding electrode; and a high-frequency voltage is present between the at least one live electrode and the coupling element, the high-frequency voltage having a frequency in the range between 500 kHz and 500 MHz.

Preferably, the device according to the invention for the dielectric heating of solids further comprises a high-frequency voltage source which generates an electrical voltage with a frequency between 500 kHz and 500 MHz, preferably between 1 and 50 MHz and particularly preferably with one approved for industrial, medical and research applications ISM frequency of 13.56 MHz or 27 MHz, for example, provides electrical connections to a live electrode and to a shielding electrode, which preferably acts as an electromagnetic shield, and a coupling element on the opposite side of the solid structure to be treated, which is capacitive to the shielding electrode is coupled. Both the electrically conductive shielding electrode and the live hot electrode are thus arranged on one side of the solid structure to be treated and are connected in an electrically conductive manner to the voltage source. An actively attached coupling electrode or a passive natural coupling element is positioned on the opposite side of the arrangement, which does not have to be connected to the electrode-shield arrangement arranged on the other side by electrically conductive supply lines. It is an essential feature inherent to the process that a capacitive coupling between the shielding and the electrode or the coupling element, which is arranged on the opposite side and has a large area, is realized.

The device according to the invention preferably additionally contains an electronic matching network which is arranged between the voltage source and electrodes or shielding and that adjusts the impedance of the load to the internal resistance of the voltage source in such a way that the RF power reflected to the generator is minimized and, if possible, completely eliminated.

At least one means for temperature measurement, for example a temperature sensor, is preferably positioned in the medium to be heated, which is particularly preferably connected to a means for power control, for example a computer system with corresponding software for evaluation, control and regulation, such that on the basis of the Measured values of the power input into the solid can be regulated in such a way that preselected temperature programs can be implemented. Furthermore, the device can comprise at least one means for measuring a field strength, a measured field strength being fed to the means for power regulation and can also be used by the latter for control and regulation. The means for power control, which is preferably part of the device according to the invention, can also take on additional tasks for optimizing the process flow in addition to the control and regulation. This also includes, for example, data acquisition and archiving, monitoring of the temperatures in the volume to be heated, monitoring of the electrical field strength, data transfer or taking over control functions to initiate emergency regimes.

The electrodes and / or the shielding are preferably designed such that substances emerging from the treated solid can pass through. The electrodes and the shielding are in particular designed so that the transport of water and / or pollutants from the treated material is not or only slightly hindered. Line or perforated electrodes or similar shields are suitable for this. The use of metal-coated, possibly permeable foils can also be suitable for the formation of the different electrodes in order to improve the handling on site.

In a particularly preferred variant for certain application contexts, the live electrode, the coupling element and / or the shielding electrode comprise an adsorption-active material. The electrodes are particularly preferably covered with a layer of adsorption-active material, preferably of activated carbon or a hydrophobic zeolite, as a result of which the passage of evaporating pollutants into the ambient air is minimized or completely prevented. An activated carbon fleece, which can be connected directly to the flat electrodes, is particularly suitable for fulfilling this task.

Accordingly, the device according to the invention for the dielectric heating of solids preferably has at least all those features which are necessary for carrying out the individual process steps of the described method are required. In particular, the individual components of the device for dielectric heating of solids preferably have all those features which are considered necessary or preferred in the description of the method. Furthermore, corresponding embodiments of the device according to the invention also result from individual embodiments or the combination of individual features of the method according to the invention. All statements made about the individual embodiments of the method according to the invention apply accordingly.

Even if the explanations focus on potential applications in construction, applications in other areas are expressly addressed. In other fields of application, other relevant thermally supported processes should also be explicitly addressed. This can be, for example, a thermally initiated hardening or structure formation in the material science context. The thermally assisted polymer formation in building materials can also be optimally combined with the device and the method for in-situ applications.

Brief description of the figures

Figur 1

eine schematische Aufsicht-Darstellung einer bevorzugten Ausführungsform einer erfindungsgemäßen Vorrichtung zur Erwärmung von Feststoffen;

Figur 2

eine schematische Aufsicht-Darstellung einer erfindungsgemäßen Elektrodenanordnung mit metallischer Kopplungselektrode als Kopplungselement;

Figur 3

eine schematische Aufsicht-Darstellung einer erfindungsgemäßen Elektrodenanordnung mit natürlichem Kompartiment als Kopplungselement;

Figur 4

zeitliche Verläufe der mittleren Temperatur, der HF-Leistung und der HF-Spannung während eines Versuches zur Erwärmung einer Porenbetonwand mittels kapazitiver Kopplung;

Figur 5

zeitliche Verläufe der mittleren Temperatur, der HF-Leistung und der HF-Spannung während eines Versuches zur Erwärmung der Wand aus Ziegelmauerwerk mittels kapazitiver Kopplung;

Figur 6

zeitliche Verläufe der mittleren Temperatur in zwei verschiedenen Tiefen, der HF-Leistung und der HF-Spannung während eines Versuches zur Erwärmung eines Kellerbodens mittels kapazitiver Kopplung;

Figuren 7a, 7b

zeitliche Verläufe der mittleren Temperatur, der HF-Leistung und der HF-Spannung (Figur 7a) sowie Temperaturverläufe für verschiedene Tiefen (Figur 7b) im Mauerwerk während eines Versuches zur Erwärmung einer Kellerwand mittels kapazitiver Kopplung;

The invention is explained below in exemplary embodiments with reference to the accompanying drawings. Show it:

Figure 1

is a schematic plan view of a preferred embodiment of a device for heating solids according to the invention;

Figure 2

is a schematic plan view of an electrode arrangement according to the invention with a metallic coupling electrode as a coupling element;

Figure 3

is a schematic plan view of an electrode arrangement according to the invention with a natural compartment as a coupling element;

Figure 4

time profiles of the mean temperature, the RF power and the RF voltage during an attempt to heat a cellular concrete wall by means of capacitive coupling;

Figure 5

temporal courses of the mean temperature, the RF power and the RF voltage during an attempt to heat the wall of brick masonry by means of capacitive coupling;

Figure 6

temporal courses of the mean temperature at two different depths, the RF power and the RF voltage during an attempt to heat a basement floor by means of capacitive coupling;

Figures 7a, 7b

time profiles of the mean temperature, the RF power and the RF voltage ( Figure 7a ) and temperature profiles for different depths ( Figure 7b ) in the masonry during an attempt to heat a basement wall using capacitive coupling;

Detailed description of the invention

Figure 1 shows a schematic top view of a preferred embodiment of a device 100 according to the invention for heating solids 40. The embodiment shown is an electrode arrangement with an electrically conductive, for example metallic coupling electrode 22 as the coupling element 20. This lies flat on a spatially extended solid 40 on. For example, the solid can be standing masonry. On the opposite side of the solid 40 there is also a voltage-carrying electrode 10 parallel to the coupling element 20. The surface of the solid covered by the voltage-carrying electrode 10 can, as shown here, be significantly smaller than the surface covered by the coupling element 20.

The live electrode 10 is surrounded by a shielding electrode 30, which also lies flat against the surface of the solid 40 in a region around the live electrode 10. This surface element forms the main plane of the shielding electrode 30. In the illustration shown, the voltage-carrying electrode 10 lies completely within the main plane of the shielding electrode 30 spanned by a large part of the shielding electrode 30. The main plane of the shielding electrode 30 lies parallel to the coupling electrode 10. Between the voltage-carrying electrode 10 and the coupling electrode 22 as a coupling element 20 a Receiving space for a solid 40 to be heated. In the area immediately around the live electrode 10, the shielding electrode 30 is shaped such that the live electrode Although electrode 10 is enclosed or covered on one side by the shielding electrode 30, there is, however, a minimal distance d _min between the live electrode 10 and the shielding electrode 30. This serves in particular to electrically decouple the shielding electrode 30 from the live electrode 10 with regard to the conductivity. The shielding electrode 30 and the live electrode 10 can thus be at different electrical potentials. The shape of the immediate area between the live electrode 10 and the shielding electrode 30 can be largely arbitrary; the corner profile of the cover shown here is chosen purely by way of example for illustrative purposes.

The live electrode 10 and the shielding electrode 30 are preferably connected to a high-frequency generator 50 via an electronic matching network 60. This generates a high-frequency alternating field between the live electrode 10 and the coupling electrode 22 as the coupling element 20, the power reflected back from the electrode arrangement to the high-frequency generator 50 being minimized by the electronic matching network 60. The device according to the invention shown further comprises a means 70 for temperature measurement and a means 90 for determining the field strength. The means 70 for temperature measurement can in particular be a fiber-optic temperature sensor. The means 90 for determining the field strength can in particular be a sensor for measuring the electrical field strength. The sensors can be connected to a means 80 for regulating the high-frequency voltage. The means 80 for regulating the high-frequency voltage can control and regulate the high-frequency voltage emitted by the high-frequency generator 50 or the high-frequency power as a function of the input variables of individual measuring devices. If active regulation and control is omitted, the measured values can preferably be stored by means 80 for regulating the high-frequency voltage and / or made available for further evaluation.

Figure 2 shows a schematic top view of an electrode arrangement according to the invention with a metallic coupling electrode 22 as a coupling element 20. The electrode arrangement shown corresponds to that in FIG Figure 1 shown arrangement. The reference symbols and descriptions therefore apply accordingly. In addition, however, the external dimensions of the surface A _{1 of} the shielding electrode 30 and the surface A _{2 of} the live electrode 10 are also shown. An inventive determination of a projected area ratio between the surfaces A ₁ , A _{2 of} the shielding electrode 30 and the live electrode 10 results from the ratio of surfaces, wherein for A ₁ only the area is taken into account for which the shielding electrode is in contact with the structure 40 to be treated. In this case, "concern" means that the distance to the solid 40 is substantially smaller than the distance to the solid in the area of the live electrode 10. In this context, a factor of at least 10 is essential. The projection is particularly important in the case of a mutual tilting between the live electrode 10, more precisely the plane spanned by the live electrode 10, and the main plane of the shielding electrode 30. However, these two levels are preferably parallel to one another.

Figure 3 shows a schematic top view of an electrode arrangement according to the invention with a natural compartment 24 as coupling element 20. The electrode arrangement shown largely corresponds to that in FIG Figure 1 shown arrangement, but here the coupling element 20 in Figure 1 shown coupling electrode 22 was replaced by a natural compartment 24. This can in particular be adjacent or heaped up soil. To implement the method according to the invention, it must be able to take on the function of a coupling electrode 22. It is therefore particularly preferred that the natural compartment 24 comprises an at least slightly electrically conductive material. In particular, this can be moist, mineral-containing soil. It is possible, within the scope of a variant of the method according to the invention, to moisten the medium acting as coupling element 20 continuously or discontinuously in order to improve its function as coupling element 20. For this purpose, an arrangement according to the invention can contain a corresponding metering device, preferably for water. In a further preferred embodiment of the device, a means for measuring the electrical conductivity and / or the moisture can additionally be placed in the compartment 24. It is particularly preferred to connect this means to the evaluation and control unit.

Example 1: Heating a wall made of aerated concrete on a pilot plant scale

For demonstration purposes, a wall made of aerated concrete (size approx. 2.0 mx 1.8 m, thickness 0.2 m) was treated in a pilot plant experiment using the method according to the invention. For this purpose, it was provided on the back with an aluminum (layer thickness 7 µm) coated polyethylene film (film thickness 12 µm), which acted as a coupling electrode (area 3.6 m ² ). The live, so-called hot electrode consisted of perforated aluminum sheet and had an area of 0.36 m ² . The shielding electrode made of copper gauze covered a total area of 3 m ² , it also being used for shielding over the hot electrode. This was achieved by placing the shield at a distance of 10 cm above the hot electrode.

The live hot electrode and the grounded shield electrode were connected to an electronic matching network, which in turn was connected to an HF generator (working frequency 13.56 MHz, maximum power 3 kW) via a coaxial cable. A capacitive coupling between the shielding electrode and the coupling electrode was realized in the manner according to the invention.

Figure 4 shows temporal profiles of the mean temperature, the RF power and the RF voltage during an attempt to heat a cellular concrete wall by means of capacitive coupling according to the inventive method and use of a variant of the inventive device. With an essentially constant RF power and RF voltage over time, an almost linear temperature rise in the cellular concrete masonry between the hot electrode and the coupling electrode can be observed. The experiment was stopped at a final temperature of approx. 32 ° C because the demonstration goal had been reached. A temperature increase of approx. 13 K was detected by fiber optic temperature sensors.

Example 2: Heating a wall segment from brick masonry

At a real location, a moistened wall made of brick masonry was thermally treated with the method and device according to the invention. The wall thickness was 24 cm. The treated outer wall of the corresponding building was accessible from both sides, but it should not be drilled through for drying, which is why the capacitive coupling had to be used for the dielectric heating. On the outside of the wall, an aluminum perforated plate acting as a coupling electrode was used, which covered the wall over an area of approximately 12 m ² . The hot electrode made of perforated aluminum with an area of approx. 1 m ² and the shielding electrode made of copper gauze (approx. 10 m ² ) were positioned on the inner wall. Shielding and hot electrode were connected to the electronic matching network and further by means of a coaxial cable to the HF generator (working frequency 13.56 MHz, maximum power 5 kW). Inside the heated wall were at depths of 4 cm, 12 cm and 20 cm fiber optic temperature sensors arranged to track the heating progress continuously and locally.

Figure 5 shows time profiles of the mean temperature, the RF power and the RF voltage during an attempt to heat the wall made of brick masonry by means of capacitive coupling. The curve profiles shown illustrate the heating progress within the wall for the segment below the hot electrode on the basis of the mean value for the corresponding temperature sensors arranged there. The stabilization of the temperature in the range of 100 ° C is mainly due to the water evaporation, which increases significantly in this temperature range. It should be noted that this temperature plateau was clearly detectable for many individual sensors, while the mean value shown here is also determined by temperature sensors that have not yet reached the evaporation temperature of the water. The depth-resolved temperature measurement showed good homogeneity of the temperature profile across the wall cross-section. The increasing HF voltage, which was necessary to maintain the nominal power of 5 kW, can be explained by the progressive drying out of the wall. The dielectric heating of the wall again demonstrates the applicability of the invention.

Example 3: Heating of a basement floor with a damp surface

Here, the device according to the invention and the method according to the invention were carried out in a house which had a dampened basement floor. It can be assumed that there was moist soil beneath the basement floor, which functioned as a coupling element in the sense of the invention. The basement floor consisted of a top layer of screed (thickness approx. 2 cm) over a layer of bricks, which in turn rested directly on the moist soil. In this respect, the screed / brick bond is to be understood as a solid to be heated.

An HF generator (working frequency 13.56 MHz, maximum power 3 kW) was used for heating in connection with an electronic matching network. This was connected via a copper tape to a hot electrode made of perforated aluminum sheet with an area of approximately 1 m ² . The Matchbox housing was connected to the shielding electrode, which was made of copper gauze and laid out on the basement floor. The total area of the copper gauze was approx. 10 m ² . The moist soil was capacitively coupled with a shielding gauze and acted as effectively as a coupling element, as from the results of the Attempts to heat can be closed. A total of 24 fiber-optic temperature sensors, which also provide reliable measurements during dielectric heating, were used to record the temperatures at depths of 5 cm and 15 cm below the surface of the basement floor.

Figure 6 shows time profiles of the mean temperature at two different depths, the RF power and the RF voltage during an attempt to heat a basement floor by means of capacitive coupling. The average temperature profiles in the two horizontal levels within the basement floor are shown, which were determined from the data of 12 temperature sensors. In addition, the RF power (constant 1 kW) and the RF voltage are specified. It becomes clear that heating of the basement floor is possible with the aid of the device according to the invention and using the method according to the invention, without it being necessary to make contact with the layer of earth acting as a coupling electrode through the basement floor. A comparison of the heating rates for the individual temperature sensors showed a good homogeneity of the heating within one level (deviations less than 20%). By increasing the power used and / or extending the time, significantly higher temperatures can be reached in the basement floor, which can ensure adequate drying.

Example 4: Heating of a basement wall with soil behind it

At another demonstration site, the device and the method according to the invention were successfully tested in analogy to embodiment 3 on a structure that was accessible from one side and was heavily dampened, in this case a brick wall (area 4 mx 2 m, thickness 0.36 m) with adjacent soil . Here the moist soil behind acted as a coupling element. The hot electrode used had a size of 1 m ² and was made of perforated aluminum sheet. Copper gauze and aluminum-coated polyethylene film were used for the shielding electrode.

An HF generator (working frequency 13.56 MHz, maximum power 5 kW) in connection with an electronic matching network was available for the heating tests. The connection between the electronic matching network (Matchbox) and the hot electrode was realized via a brass profile. Furthermore, the housing of the matchbox with the shielding electrode, which was made of copper gauze in the area of the hot electrode and out aluminum-coated plastic film (perforated, thickness of the aluminum layer 15 microns, thickness of the carrier film 20 microns) existed in the rest of the area. The total area of the shielding electrode was approximately 7 m ² . A total of 15 fiber optic temperature sensors, which were introduced into the brick masonry at depths of 6 cm, 18 cm and 30 cm, were used to record the temperatures.

Figure 7 shows temporal profiles of the mean temperature, the RF power and the RF voltage ( Figure 7a ) and temperature profiles for various depths in the masonry during an attempt to heat a basement wall using capacitive coupling ( Figure 7b ). The average temperature of all temperature sensors placed in the directly heated area behind the hot electrode as well as the RF power and the RF voltage over the entire test period are shown. In addition, the mean temperature profiles for the individual depths in the masonry are shown. It could be shown that with the aid of the method according to the invention and using the device according to the invention, dielectric heating of a cellar wall accessible from one side is possible by means of radio waves.

Reference list

10th

live electrode

20th

Coupling element

22

Coupling electrode

24th

natural compartment

30th

Shielding electrode

40

Solid

40 '

Recording room

50

High frequency generator

60

electronic matching network

70

Means for temperature measurement

80

Power regulation means

90

Means for determining the field strength

100

Dielectric heating device

d _min

minimum distance between the live electrode and the shielding electrode

A ₁

Surface of the shield electrode 30

A ₂

Surface of the live electrode 10

Claims (14)

1. A method for the dielectric heating of solids (40), comprising the following steps:

   - providing at least one live electrode (10) and at least one shielding electrode (30) on a first side of a solid (40) and at least one coupling element (20) on a second side of the solid (40), wherein the first side of the solid (40) and the second side of the solid (40) lie opposite one another;

   - setting the area ratio between the overlapping area between the surfaces of the at least one coupling element (20) and the at least one shielding electrode (30) and the surfaces of the at least one live electrode (10), wherein the area ratio is greater than 3:1;

   - coupling the at least one coupling element (20) with the at least one shielding electrode (30) in a manner that is at least partially capacitive;

   - applying a high-frequency voltage to the at least one live electrode (10), wherein the high-frequency voltage has a frequency in the range between 500 kHz and 500 MHz.
2. The method according to claim 1, wherein a preselected ratio of the heating rates inside and outside the area between the at least one live electrode (10) and the at least one coupling element (20) is set via the area ratio.
3. The method according to one of the preceding claims, wherein the at least one coupling element (20) comprises a natural environmental compartment (24) as an electrode-equivalent coupling element (20).
4. The method according to claim 3, wherein a wetting of the natural environmental compartment (24) occurs in order to improve the electrical conductivity of the natural environmental compartment (24) and thus its effect as an electrode-equivalent coupling element (20) .
5. The method according to one of the preceding claims, wherein the output of the high-frequency voltage is adjusted to a temperature measured in the area between the at least one live electrode (10) and the at least one coupling element (20) in view of an intended temporal heating regime.
6. The method according to one of the preceding claims, wherein the temperature of the solid (40) is increased in order to dry the solid (40), to kill wood pests and/or impair their ability to live and/or in order to remove noxious substances from the solid (40).
7. The method according to one of the preceding claims, wherein a removal of noxious substances from the solid (40) is supported by a removal of water vapour from the solid (40).
8. The method according to one of the preceding claims, wherein the output of the high-frequency voltage is adjusted to a field strength measured in the area between the at least one live electrode (10) and the at least one coupling element (20).
9. A device (100) for the dielectric heating of solids (40) comprising:

   - a live electrode (10);

   - a shielding electrode (30), wherein the live electrode (10) and the shielding electrode (30) can be arranged on a first side of a solid (40), and the shielding electrode (30) is capacitively coupled to a coupling element (20) on a second side of the solid (40) during operation, wherein the first side of the solid (40) and the second side of the solid (40) lie opposite one another; and

   - a means for applying a high-frequency voltage which is configured to apply a high-frequency voltage with a frequency in the range between 500 kHz and 500 MHz to the live electrode (10),
   characterized in that
   the area ratio between the overlapping area between the surfaces of the at least one coupling element (20) and the at least one shielding electrode (30) and the surfaces of the at least one live electrode (10) is greater than 3:1.
10. The device (100) according to claim 9, wherein the shielding electrode (30) and the live electrode (10) lie in a common plane.
11. The device (100) according to claim 9 or 10, wherein the at least one coupling element (20) comprises a natural environmental compartment (24) as an electrode-equivalent coupling element (20).
12. The device (100) according to claim 11, wherein at least one means for the wetting of the natural environmental compartment (24) is provided in order to improve the electrical conductivity of the natural environmental compartment (24) and thus its effect as an electrode-equivalent coupling element (20).
13. The device (100) according to one of claims 9 to 12, further comprising:

    - a means (70) for temperature measurement which is configured to determine a temperature of a solid (40) and/or a means (90) for determining the field strength between the live electrode (10) and the coupling element (20);

    - a means (80) for output adjustment which is configured to adjust the output of the high-frequency voltage applied to the live electrode (10) as a function of the temperature of the solid and/or of the field strength.
14. The device (100) according to one of claims 9 to 13, wherein the live electrode (10), the coupling element (20) and/or the shielding electrode (30) are permeable for noxious substances escaping from the solid (40) and/or comprise an adsorption-active material.

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