Patent Application
20170122627
The present invention relates to a vacuum insulation body comprising a thermoelectric element which is preferably configured as a Peltier element and which is preferably used in refrigerator units and/or freezer units.
With refrigerator units and/or freezer units, a vacuum insulating body is arranged in the region between the outer jacket of the unit and the inner container to be cooled to achieve a sufficiently high thermal insulation between the outside and the inside of the unit to be insulated by means of the principle of vacuum thermal insulation.
Thermoelectric elements, in particular Peltier elements, are elements which can generate a temperature drop with the aid of electrical energy. The Peltier element comprises two or more small cuboids which are made up of p-doped and n-doped semiconductor materials and are connected to one another alternatingly at the top and bottom by metallic bridges. The cuboids are connected to one another such that serial connection is made in which differently doped semiconductor materials are arranged alternately.
The thermoelectric elements, however, have a comparatively small efficiency or a small capacity, which has the result that Peltier elements have no extensive use in the cooling of refrigerator units and/or freezer units. Thermoelectric elements are only used sporadically in the field of coolers in which no large temperature difference is required. The use of thermoelectric elements in the field of refrigerating technology is therefore restricted to special cases.
Due to the insulation becoming better and better, however, and due to the reduced cooling power required for cooling which results therefrom, thermoelectric elements, in particular Peltier elements are becoming an interesting alternative.
On a simultaneous use of a vacuum insulation and a thermoelectric element, however, the problem arises of effectively integrating the two components. This problem stems from the fact that the cold generation and the heat generation of a thermoelectric element naturally take place directly next to one another so that the use of the thermoelectric element can only be carried out with the aid of a large hole through the vacuum insulation. This results in a reduced insulation performance and in a complicated design of the vacuum insulation and the thermoelectric element.
These considerations are, however, by no means restricted to refrigerator units and/or freezer units, but also apply to thermally insulated containers in general. Thermally insulated containers subject to these considerations have at least one temperature-controlled inner space, with this being able to be cooled or heated so that a temperature results in the inner space below or above the ambient temperature of e.g. 21° C.
It is the object of the present invention to eliminate the above problems and to provide an efficient use of a combination of thermoelectric element and vacuum insulation which has a comparatively simple design.
This object is achieved by a vacuum insulation body having the features of claim 1.
The vacuum insulation body accordingly has at least one envelope which defines at least one vacuum zone. At least one thermoelectric element is located within the vacuum zone to generate a temperature difference between two zones provided at the outside of the envelope.
The at least one thermoelectric element is thus preferably located completely within the vacuum zone of the vacuum body so that openings in the envelope of the vacuum insulation body for the heat dissipation and heat supply from/to the thermoelectric element can preferably be omitted.
A preferably diffusion-tight envelope or film is required to provide a vacuum insulation body in which a vacuum is present. In this respect, a core material can be provided in the vacuum zone that provides the vacuum insulation body with the corresponding shape stability and that simultaneously prevents the walls of the envelope directly contacting one another after the generation of a vacuum.
Since the thermoelectric element is provided in the vacuum zone, the typically large opening of the vacuum insulation is avoided which was conventionally provided by a thermoelectric element in the refrigeration. A particularly advantageous insulation performance of an inner space bounded by the vacuum insulation body and a very space-saving and structured arrangement of the two components result from this arrangement.
The arrangement of the thermoelectric element in the vacuum zone provides that a corresponding temperature gradient is present for orienting the thermoelectric element on an operation of the thermoelectric element at the outside of the envelope. This means that, depending on the hot or cold surface of the thermoelectric element, the zones of the envelope facing the hot or cold surface adopt a corresponding temperature. Two different temperature levels are thus present at two different points (zones) of the outside of the envelope which are caused by the thermoelectric element or can be caused by it.
The arrangement of the thermoelectric element within the vacuum zone also brings about the advantage that it is protected from external influences. Sealing measures for preventing condensation at the cold point of the thermoelectric element or Peltier element can in particular be dispensed with.
The thermoelectric element preferably has a substantially plate-like basic shape, with the thermoelectric element having two thermal surfaces which preferably extend approximately in parallel with one another and are spaced apart.
In accordance with a further advantageous feature of the invention, the vacuum insulation body has at least one heat conductive body arranged in the vacuum zone. It is in heat-transferring, preferably thermoconductive, contact with the thermoelectric element and with the envelope. The thermoconductive body is in direct or indirect contact with the thermoconductive body and/or with the envelope.
A “thermoconductive body” or a “heat exchanger” is understood within the framework of the present invention as any desired element with which heat can be transferred, with this heat transfer inter alia comprising the heat conduction, but not being restricted thereto.
The named thermoconductive body advantageously has a thermal conductivity λ of at least 3 W/m*K). The thermal conductivity λ of the thermoconductive body is preferably at least 10 W/(m*K), preferably at least 75 W/(m*K), and particularly preferably at least 150 W/m*K).
It is possible in accordance with the invention to bring the thermoelectric element arranged in the vacuum zone in an effective thermal (direct or indirect) contact with the envelope. The thermoconductive body in this respect provides a good thermal coupling of the Peltier element or of the thermoelectric element and the envelope since the heat exchange via convection in a vacuumed zone is only possible in a slowed down manner or is not possible at all.
On a transport of the heat generated and/or removed at the cold surface and at the waste heat surface of the thermoelectric element through the envelope of the vacuum insulation body, the envelope represents a significant thermal resistance, independent of its thickness, which has to be overcome.
It is expedient in this respect to provide the thermoconductive body (also called the “primary heat exchanger” in the following), in addition to the thermoelectric element, such that its contact surface with the envelope is larger than its contact surface with the thermoelectric element. This has the result that the transfer surface at the envelope is much larger than the transfer surface of the thermoelectric element at the thermoconductive body and the temperature dropping over the envelope is reduced to an acceptable degree. The smaller temperature difference which is present at the two sides of the envelope due to the specific design of the thermoconductive body produces smaller losses at the envelope overall.
The thermoconductive body or bodies is/are preferably arranged within the vacuum zone.
A fixing of the thermoelectric element or elements and of the thermoconductive body or bodies, which are attached within the vacuum zone, preferably takes place with the help of the envelope itself which has a specific pressure which is applied from the outside due to its vacuumed state and said pressure can be used to fix the elements arranged in the vacuum zone. A partial vacuum arises due to the vacuum present in the vacuum zone which can be sufficiently large to achieve a layering of the thermoelectric element with the thermoconductive body without the contact or adhesive bonding with a substance capable of good thermal conductivity typical for a thermoconductive body being necessary. It is therefore not necessary to provide a further element between the envelope and the Peltier element and/or the thermoconductive body or between the envelope and the thermoconductive body that reduces the thermal conductivity.
Provision is made in accordance with a preferred embodiment that the thermoelectric element is clamped between the solid bodies which form the primary heat exchanger.
Provision is preferably made in this respect that the connection element or elements which connects/connect the solid bodies has/have a small thermal conductivity so that no significant heat bridge is produced. It is conceivable to use screws as the connection element or connection elements. It is also possible to use a part such as an injection molded part as a connection element or as connection elements that is fastened to a molded part and that latches at another molded part on assembly.
Provision is made in an embodiment that no adhesive is provided between the thermoconductive body or bodies and the inside of the film.
However, the case is generally also covered by the invention that means promoting the heat transfer, in particular a substance with thermal conductivity e.g. in the form of an adhesive bond, are present between the thermoelectric element and the thermoconductive body or bodies.
Provision is made in an embodiment that the thermoelectric element and the thermoconductive body are connected to one another using an adhesive connection. Provision is preferably made in this respect that an adhesive having a comparatively high thermal conductivity is used, for example an adhesive in which adhesive compound fillers of good heat conductivity are present. Such an adhesive can also be used for other adhesive connections used within the framework of the present invention.
In accordance with a further advantageous optional feature of the invention, the vacuum insulation body furthermore has at least one heat exchanger (also called a “secondary heat exchanger” in the following) that is arranged outside the vacuum zone, that is at the outside of the envelope. The secondary heat exchanger is thermally coupled to region of the envelope that is preferably the region whose temperature can be influenced by the thermoelectric element. Thermally coupled includes the possibility of a direct contact or of a thermal contact.
Provision is preferably made that the thermoconductive body or bodies are connected to the inside of the film and are not in direct contact with the secondary heat exchanger. The heat exchange in this case takes place through the film. This embodiment can be advantageous for technical production reasons as well as for reasons of vacuum tightness. It is conceivable that the thickness of the film in the contact region of the thermoconductive body or bodies is/are reduced with respect to the other regions to ensure a better heat exchange. Alternatively, the thickness of the film can, however, also be unchanged in these regions, which in turn can be advantageous for technical production reasons as well as for reasons of vacuum tightness.
Provision can alternatively be made that the thermoconductive body or bodies is/are in direct contact with the secondary heat exchanger and that cutouts are provided in the film of the envelope in the region of the thermoconductive body or bodies. The thermal conduction can thus be optimized.
The secondary heat exchanger can e.g. be connected to the outer film side by means of a thermoconductive paste or by a thermoconductive adhesive.
Provision is made in a preferred embodiment that a thin graphite film is arranged at one side as a coupling element for the mechanical relief of the thermoelectric element in the production process, with the thermoelectric element being fixed by clamping between the two solid bodies via the connection elements. At the other side, the thermoconductive adhesive is also used to compensate production tolerances in the thicknesses of the thermoelectric element, the solid bodies and the connection elements. The graphite film is preferably used at the hot side since the higher heat flows flow here and the heat transfer resistance through the thin graphite film is typically smaller than the thermoconductive adhesive layer somewhat thicker due to tolerance compensation.
The secondary heat exchanger or heat exchangers are preferably arranged such that a direct or indirect heat exchange takes place from or to the primary heat exchanger.
The envelope preferably comprises a high barrier film or is a high barrier film which terminates the vacuum zone formed by the envelope in a vacuum-tight manner.
A vacuum-tight or diffusion-tight envelope or a vacuum-tight or diffusion-tight connection or the term high barrier film is preferably understood as an envelope or as a connection or as a film by means of which the gas input into the vacuum insulation body is reduced so much that the increase in the thermal conductivity of the vacuum insulation body caused by gas input is sufficiently low over its service life. A time period of 15 years, preferably of 20 years, and particularly preferably of 30 years, is to be considered as the service life, for example. The increase in the thermal conductivity of the vacuum insulation body caused by gas input is preferably<100%, and particularly preferably<50%, over its service life.
The surface-specific gas permeation rate of the envelope or of the connection or of the high barrier film is preferably<10-5 mbar * I/s *m2 and particularly preferably<10-6 mbar * I/s *m2 (measured according to ASTM D-3985). This gas permeation rate applies to nitrogen and to oxygen. There are likewise low gas permeation rates for other types of gas (in particular steam), preferably in the range from<10-2 mbar * I/s * m2 and particularly preferably in the range from<10-3 mbar * I/s * m2 (measured according to ASTM F-1249-90). The aforesaid small increases in the thermal conductivity are preferably achieved by these small gas permeation rates.
An enveloping system known from the sector of vacuum panels are so-called high barrier films. Single-layer or multilayer films (which are preferably able to be sealed) having one or more barrier layers (typically metal layers or oxide layers, with aluminum and an aluminum oxide preferably being used as the metal or oxide respectively) are preferably understood by this within the framework of the present invention which satisfy the above-named demands (increase in thermal conductivity and/or surface-specific gas permeation rate) as a barrier to the gas input.
The above-named values or the make-up of the high barrier film are exemplary, preferred values which do not restrict the invention.
In a further advantageous embodiment of the invention, the at least one thermoconductive body and/or one heat exchanger, i.e. the primary and/or the secondary heat exchanger, is/are itself/themselves a part of the envelope or forms the total envelope. It is of advantage in this respect that, on the emission of the temperature difference generated by the thermoelectric element, a thermal resistance which is brought about by the envelope does not have to be overcome.
If the primary or secondary heat exchanger forms a part of the envelope, the heat exchangers (primary and secondary) can be directly in contact with one another, which brings along the advantage that the thermal resistance of the film does not have to be overcome.
The vacuum insulation body furthermore preferably comprises a core material that is present within the vacuum zone and that is arranged between the individual semiconductor elements of the thermoelectric element.
The skilled person knows that a thermoelectric element (Peltier element) comprises a plurality of differently doped semiconductor elements arranged next to one another in a grid-like manner. In this respect, the respective semiconductor elements are spaced apart from one another, with a core material being provided in this region in accordance with an optional feature of this invention.
The core material is therefore inserted into the region between the semiconductor pellets of the Peltier element. The gas heat conduction and the radiation heat exchange whose importance in the transfer of temperature increases in a vacuumed state with an increasing purity of the vacuum is thereby effectively suppressed between the hot and cold side of the thermoelectric element. Overall, this results in an increase in performance of the thermoelectric element, whereby a more resource-efficient cooling or heating is possible.
In addition, the present invention describes a thermoelectric element that comprises at least one n-doped semiconductor element and at least one p-doped semiconductor element. The p-doped semiconductor element is connected via a conductor bridge to the n-doped semiconductor element, with the two semiconductor elements being spaced apart from one another so that a free space is formed between them. The thermoelectric element in accordance with the invention is characterized in that the free space between the p-doped semiconductor element and the n-doped semiconductor element is filled with a material in powder form.
The material in powder form preferably has a mean grain size in which a powder grain is between 5 μm and 30 μm, preferably between 10 μm and 25 μm, and particularly preferably between 15 μm and 20 μm.
Another name for the differently doped semiconductor elements of the thermoelectric element is semiconductor pellets. The material in powder form inserted between the space of the semiconductor pellets prevents convection between the hot surface and the cold surface of the thermoelectric element. The effectiveness of the thermoelectric element can thus be increased.
The present invention furthermore relates to a vacuum insulation body in accordance with one of the above-described variants in which the thermoelectric element has a material in powder form in the free space between the differently doped semiconductor elements. This material in powder form is in this respect simultaneously also a core material for the vacuum insulation body. Not only the performance capability of the thermoelectric element can thus be increased, but rather the advantages associated with the core material can also simultaneously be achieved. An encapsulation of the thermoelectric element from the core material is not necessary in this respect due to the material identity.
In addition, the present invention relates to a thermally insulated container having at least one carcass and having at least one temperature-controlled inner space, preferably to a refrigerator unit and/or freezer unit having at least one carcass and having at least one refrigerated inner space which is surrounded by the carcass as well as having at least one closing element by means of which the temperature-controlled and preferably the refrigerated inner space can be closed. At least one intermediate space in which at least one vacuum insulation body in accordance with the invention and/or a thermoelectric element in accordance with the invention is located between the temperature-controlled and preferably the refrigerated inner space and the outer wall of the container and preferably of the unit.
The vacuum insulation body can be located between the outside of the carcass in the inner container and/or between the outside and the inside of the door or of another closing element.
In a preferred embodiment of the container in accordance with the invention and preferably of the refrigerator unit and/or freezer unit in accordance with the invention, it is partly or completely insulated with the help of a full vacuum system. It is in this respect an arrangement whose thermal insulation between the outside and the inner space at the carcass and/or at the closing element only or primarily comprises an evacuated element, in particular in the form of the envelope of vacuum-tight film or high barrier film with a core material. The full vacuum insulation is preferably formed by one or more vacuum insulation bodies in accordance with the invention. A further thermal insulation by an insulating foam and/or by vacuum insulation panels or by another means for thermal insulation between the inside and the outside of the unit is preferably not provided.
This preferred form of thermal insulation in the form of a full vacuum system can extend between the wall bounding the inner space and the outer skin of the carcass and/or between the inner side and the outer side of the closing element such as a door, flap, lid, or the like.
The full vacuum system can be obtained such that an envelope of a gas-tight film is filled with a core material and is subsequently sealed in a vacuum-tight manner. In an embodiment, both the filling and the vacuum-tight sealing of the envelope take place at normal or ambient pressure. The evacuation then takes place by the connection to a vacuum pump of a suitable interface worked into the envelope, for example an evacuation stub which can have a valve. Normal or ambient pressure is preferably present outside the envelope during the evacuation. In this embodiment, it is preferably not necessary at any time of the manufacture to introduce the envelope into a vacuum chamber. A vacuum chamber can be dispensed with in an embodiment to this extent during the manufacture of the vacuum insulation.
The temperature-controlled inner space is either cooled or heated depending on the type of the unit (cooling appliance, heating cabinet, etc.).
Provision is made in an embodiment that the container in accordance with the invention is a refrigerator unit and/or a freezer unit, in particular a domestic appliance or a commercial refrigerator. Such units are, for example, covered which are designed for a stationary arrangement at a home, in a hotel room, in a commercial kitchen or in a bar. It can, for example, be a wine cooler. Chest refrigerators and/or freezers are furthermore also covered by the invention. The units in accordance with the invention can have an interface for connection to a power supply, in particular to a domestic mains supply (e.g. a plug) and/or can have a standing aid or installation aid such as adjustment feet or an interface for fixing within a furniture niche. The unit can, for example, be a built-in unit or also a stand-alone unit.
In an embodiment, the container or the unit is configured such that it can be operated at an AC voltage such as a domestic mains voltage of e.g. 120 V and 60 Hz or of 230 V and 50 Hz. In an alternative embodiment, the container or the unit is configured such that it can be operated with DC current of a voltage of, for example, 5 V, 12 V or 24 V. Provision can be made in this embodiment that a plug-in power supply is provided inside or outside the unit via which the unit is operated. An advantage of the use of thermoelectric heat pumps in this embodiment is that the whole EMC problem only occurs at the power pack.
Provision can in particular be made that the refrigerator unit and/or freezer unit has a cabinet-type design and has a useful space which is accessible to a user at its front side (at the upper side in the case of a chest). The useful space can be divided into a plurality of compartments which are all operated at the same temperature or at different temperatures. Alternatively, only one compartment can be provided. Storage aids such as trays, drawers or bottle-holders (also dividers in the case of a chest) can also be provided within the useful space or within a compartment to ensure an ideal storage of refrigerated goods or frozen goods and an ideal use of the space.
The useful space can be closed by at least one door pivotable about a vertical axis. In the case of a chest, a lid pivotable about a horizontal axis or a sliding cover is conceivable as the closing element. The door or another closing element can be connected in a substantially airtight manner to the carcass by a peripheral magnetic seal in the closed state. The door or another closing element is preferably also thermally insulated, with the thermal insulation being able to be achieved by a foaming and optionally by vacuum insulation panels or also preferably by a vacuum system and particularly preferably by a full vacuum system. Door storage areas can optionally be provided at the inside of the door in order also to be able to store refrigerated goods there.
It can be a small appliance in an embodiment. In such units, the useful space defined by the inner wall of the container has, for example, a volume of less than 0.5 m3, less than 0.4 m3 or less than 0.3 m3.
The outer dimensions of the container or unit are preferably in the range up to 1 m with respect to the height, width and depth.
The invention is, however, not restricted to refrigerator units and/or freezer units, but rather generally applies to units having a temperature-controlled inner space, for example also to heat cabinets or heat chests.
Further particulars and details will be explained with reference to the following description of the Figures. There is shown:
In addition, a thermoelectric element 3 can be recognized having semiconductor pellets which connect the two thermoconductive bodies 4 or extend between them in the drawing. The thermoelectric element 3 has two surfaces 31, 32, between which a temperature drop can be adopted, in a direction extending transversely to the alignment of the semiconductor pellets. To transport the temperature present at these surfaces 31, 32 efficiently to marginal regions of the envelope 2, the respective thermoconductive bodies 4 are connected both to the envelope 2 and to the surface 31, 32 of the thermoelectric element 3.
The thermoconductive bodies 4 have a cross-sectional area which increases in size toward the margin of the vacuum insulation body starting from the thermoelectric element 3.
In addition, a heat exchanger 5 can be recognized which is arranged outside the vacuum zone and which is configured to take up or emit the heat transported through the respective thermoconductive bodies 4.
The thermoconductive bodies 4 and the heat exchanger 5, i.e. the primary 4 and the secondary heat exchanger 5, are thermoconductively connected to one another. The heat conduction takes place through the thin film. Provision can be made, as shown in the drawing, that the thickness of the films 2 is reduced with respect to the other regions at the inside and outside in the region of the heat exchanger 4 to ensure a better heat exchange. Alternatively, the thickness of the film 2 can, however, also be unchanged in this region, which is advantageous in production and increases the vacuum-tightness of the system.
Vacuum is present within the vacuum insulation body so that the thermoelectric element 3 and the primary heat exchangers 4 are located completely within the evacuated zone.
A support core, for example in the form of a powder, and preferably in the form of Pearlite powder, is furthermore present within the evacuated region between the films. If this powder is also present between the semiconductor pellets of the Peltier element, both the gas thermal conduction and the radiation heat exchange between the hot and cold sides of the Peltier element or of the thermoelectric element are thereby suppressed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2014 008 668.2 | Jun 2014 | DE | national |
| 10 2015 000 553.7 | Jan 2015 | DE | national |
| 10 2015 001 060.3 | Jan 2015 | DE | national |
| 10 2015 001 142.1 | Jan 2015 | DE | national |
| 10 2015 001 281.9 | Feb 2015 | DE | national |
| 10 2015 001 380.7 | Feb 2015 | DE | national |
| 10 2015 006 561.0 | May 2015 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/001183 | 6/11/2015 | WO | 00 |
