dishwasher

Abstract

A dishwasher with a receiving space (1) serving to receive items to be cleaned, wherein the receiving space (1) is delimited on the outside by walls (2) of a washing container (3) and a door, wherein the walls (2) each have an inner side (4) facing the receiving space (1) and an outer side (5) facing away from the receiving space (1), and wherein a flat latent heat storage material (6) is arranged in the region of the outer side (5) of at least one of the walls (2), which is in heat-conducting contact with an evaporator (7) of a heat pump arrangement (8) of the dishwasher, wherein the heat pump arrangement (8) is designed to transfer heat from the latent heat storage material (6) to a wash liquor circulating at least temporarily within the dishwasher during operation of the dishwasher, characterized in that the latent heat storage material (6) has at least one additive (11),wherein the mixture of latent heat storage material (6) and additive has a higher thermal conductivity than the latent heat storage material (6).,

Description

[0001] The present invention relates to a dishwasher with a receiving space serving to receive items to be cleaned, wherein the receiving space is delimited on the outside by walls of a washing container and a door, wherein the walls each have an inner side facing the receiving space and an outer side facing away from the receiving space, and wherein in the region of the outer side of at least one of the walls a flat latent heat storage material is arranged, which is in heat-conducting contact with an evaporator of a heat pump arrangement of the dishwasher, wherein the heat pump arrangement is designed to transfer heat from the latent heat storage material to a washing liquor circulating at least temporarily within the dishwasher during operation of the dishwasher.

[0002] Dishwashers are well known in the art and are generally used to clean dirty dishes. While heat is generally required during the cleaning program steps to be introduced into the wash tub and thus into the circulating wash liquor (water or water with detergent) within the wash tub, during a drying step, during which the wash items are to be dried, it is necessary to dissipate heat from the walls of the wash tub to condense the water vapor present within the wash tub.

[0003] In other words, every standard dishwashing program contains program steps during which heat must be introduced into the washing tub, as well as program steps during which heat must be removed from the washing tub. It is therefore common practice to equip dishwashers with a water tank that serves as an intermediate heat storage device. However, since such water tanks must be watertight, such solutions are relatively complex to construct.

[0004] In EP 2 193 741 A2, a heat coupling tank is provided for a household appliance such as a dishwasher with a processing chamber for treating items at different temperatures and with a heat accumulator, which heat coupling tank is adjacent to the processing chamber on a first side and to the heat accumulator on a second side. The thermal resistance between the processing chamber and the heat accumulator is smaller when the heat coupling tank is filled with a coupling fluid than when the heat coupling tank is not filled with the coupling fluid. An evaporator of a heat pump can be thermally coupled to the heat accumulator. In addition, the heat accumulator can be a subcoolable latent heat accumulator. During the program sequence of a dishwasher, such as according to Fig. 1 In a first process phase or during the main wash cycle, the heat pump is activated to extract heat from the heat storage unit and feed it into the process water in the process chamber or tub of the dishwasher. During this phase, the heat coupling tank is empty. In the last liquid-carrying process phase of the program sequence, the final rinse phase, the fresh water in the tub of the dishwasher, which has been mixed with rinse aid, can also be heated again using the heat pump if necessary. Here, too, the heat coupling tank remains empty. Only in the subsequent drying phase is the heat coupling tank filled with liquid, so that the thermal resistance between the heat storage unit and the tub wall decreases. As a result, the tub wall, on the outside of which the heat storage unit is located, forms a cooling surface on which water can separate from the moist tub air.

[0005] The dishwasher of DE 196 22 882 A1 has a latent heat accumulator located outside its wash chamber for condensing the moisture contained in the wash chamber atmosphere during the drying process. At least a portion of the outer surface of the wash chamber wall is in surface thermal contact with the latent heat accumulator, interposed by an intermediate layer that is thermally conductive only during a drying phase but otherwise essentially thermally insulating.

[0006] The object of the present invention is to counteract disadvantages of these dishwashers.

[0007] According to the invention, a flat latent heat storage material is arranged in the region of the outer side of at least one of the said walls of the washing container, which is in heat-conducting contact with an evaporator of a heat pump arrangement of the dishwasher, wherein the heat pump arrangement is designed to transfer heat from the latent heat storage material to a washing liquor circulating at least temporarily within the dishwasher during operation of the dishwasher.

[0008] A latent heat storage material is a so-called phase change material (PCM), i.e. a heat storage material whose latent heat of fusion is significantly greater than the heat it could store due to its normal specific heat capacity (without the phase transformation effect). If, for example, a paraffin, a salt solution or another material known to those skilled in the art is used whose melting temperature is X °C (X corresponds to a specific value), this means that the substance exists in a solid state up to a temperature of X °C. If further heat energy is then added to the substance at this temperature (e.g. during a cleaning step of the dishwashing program), it gradually begins to melt and in this way once again stores a relatively large amount of heat.

[0009] According to the invention, the latent heat storage material is flat, i.e., its spatial extent running parallel to the adjacent wall of the flushing container is many times (for example, at least 10 to 50 times) greater than its thickness running perpendicular to the said wall. In particular, the latent heat storage material can be in the form of one or more mats, which can be attached directly to one or more of the outer sides of the walls. Alternatively, one or more layers of another material, e.g., bitumen, can be arranged between the respective wall and the adjacent latent heat storage material.

[0010] Furthermore, the latent heat storage material is in heat-conducting contact with an evaporator of a heat pump arrangement of the dishwasher. With the help of the heat pump arrangement, it is possible to transfer heat that the latent heat storage material has absorbed during a program step in which heated wash liquor circulates within the wash tub back to the wash liquor in a subsequent program step. This enables energy-efficient operation of the dishwasher, in which overall energy consumption can be minimized. The evaporator can be a flat or tubular structure that, for example, rests against the latent heat storage material and through which, during operation of the heat pump arrangement or a pump thereof, a heat transfer material flows. This heat transfer material serves to absorb heat from the latent heat storage material.

[0011] In addition to the evaporator, the heat pump arrangement preferably comprises a piping system for a heat pump medium, an expansion valve, and a compressor for the heat transfer medium evaporated by heat absorption. A liquid with an evaporation point between -20°C and 20°C is preferably used as the heat transfer medium. As this liquid flows through the piping system with the aid of a pump and into the area of ​​the heated and / or liquefied latent heat storage material, it evaporates. As the flow continues, it reaches the area of ​​the compressor, where it is compressed and liquefied, becoming considerably hotter. Finally, it reaches the area of ​​a heat exchanger, which is located, for example, in the area of ​​a pump sump of a dishwasher and can be used to transfer heat from the heat transfer medium to the wash liquor.The pressure of the heat transfer medium is then reduced in the area of ​​the expansion valve, causing the heat transfer medium to cool and finally pass through the latent heat storage material in liquid form, where it is re-evaporated while absorbing heat. As a result, the heat pump arrangement makes it possible to transfer heat from the latent heat storage material to the wash liquor without the latent heat storage material coming into direct contact with the wash liquor.

[0012] As a result, the dishwasher according to the invention has an “intermediate heat storage device” in the form of the latent heat storage material and a device (heat pump arrangement) for transferring the temporarily stored heat to the washing liquor.

[0013] According to an advantageous development of the invention, the latent heat storage material has a phase change temperature whose value lies between 0 °C and 30 °C, preferably between 10 °C and 25 °C. If the latent heat storage material, initially in solid form, reaches the corresponding phase change temperature during a program step, it begins to melt and absorbs further thermal energy. If heat is required in a subsequent program step to transfer it to the wash liquor, the heat pump arrangement and thus also its pump are activated. As a result, the heat transfer medium is pumped through the evaporator and extracts the temporarily stored thermal energy from the latent heat storage material, which can then be transferred to the wash liquor with the help of the aforementioned heat exchanger.

[0014] According to an advantageous development of the invention, the latent heat storage material has, at least in sections, a thickness running perpendicular to the adjacent wall, the thickness of which is 3 mm to 50 mm, preferably 10 mm to 40 mm. The latent heat storage material is preferably in the form of one or more mats, wherein the mat(s) are preferably glued to the adjacent wall of the flushing container or to an intermediate layer (e.g., bitumen) arranged between the latent heat storage material and the wall.

[0015] According to an advantageous development of the invention, the evaporator has at least one evaporator tube, wherein the evaporator tube is at least partially embedded in the latent heat storage material. The evaporator tube can have an inner diameter of 5 mm to 20 mm, at least in sections, and is preferably made of a metal to ensure good heat transfer between the heat transfer medium circulating within the evaporator tube and the latent heat storage material. Of course, several interconnected evaporator tubes can also be present. Branches within the latent heat storage material are also conceivable to increase the contact area between the evaporator tube and the latent heat storage material.

[0016] According to an advantageous development of the invention, the evaporator tube extends through the latent heat storage material in a serpentine pattern. For example, it would be conceivable for the evaporator tube to enter the latent heat storage material in the region of a first lateral wall of the washing container, extend through it in a serpentine or meandering pattern, and exit the latent heat storage material again at a second lateral wall of the washing container.

[0017] According to an advantageous development of the invention, the latent heat storage material extends over at least one lateral wall of the washing compartment. Preferably, the latent heat storage material extends over several lateral walls (including the rear wall, i.e., the wall facing away from the door). In this context, it is also conceivable for the latent heat storage material to be present as a structure extending over the corresponding walls. Alternatively, several latent heat storage material units can be used, which do not necessarily have to be connected to one another. For example, two or more of the aforementioned walls could have separate latent heat storage material units.

[0018] According to an advantageous development of the invention, the latent heat storage material extends over at least 70%, preferably over at least 80%, of the outer surface of at least one wall adjacent to the latent heat storage material. The respective outer surface(s) is / are thus largely surrounded by a latent heat storage material, ensuring the largest possible heat transfer surface between the latent heat storage material and the washing container or its walls. The latent heat storage material is preferably in the form of a rectangular, mat-shaped structure.

[0019] According to an advantageous development of the invention, the latent heat storage material extends over two lateral walls and an upper wall of the washing compartment, so that the latent heat storage material has a U-shape in a front view of the dishwasher. In this case, the latent heat storage material is, so to speak, "slipped over" the washing compartment and has a trough shape. The depth of the latent heat storage material, i.e., its spatial extension to the rear (in a front view of the U-shape), is furthermore preferably constant and in particular has an amount that is at least 60%, preferably at least 80%, of the corresponding depth of the washing compartment.

[0020] According to an advantageous development of the invention, the latent heat storage material is surrounded by a dimensionally stable shell. The latent heat storage material is thus encapsulated, particularly externally, by the shell, so that it always remains in its predetermined position, regardless of its physical state. The shell can be made of a solid or rigid material. A shell made of a flexible material is also conceivable. For example, the shell can be formed by a closed plastic film, the wall thickness of which should be at least 2 mm.

[0021] According to an advantageous development of the invention, the shell is formed by a molded plastic part. For example, the molded plastic part can be a thin-walled blow-molded part made of polypropylene, for example. The latent heat storage material is preferably completely encapsulated to the outside by means of the molded plastic part, with connection areas or openings naturally being provided through which the evaporator can enter and exit the latent heat storage material.

[0022] According to an advantageous development of the invention, an outer surface of the casing facing the outer side of a wall of the washing container is adapted, at least in sections, to the contour of said outer side. In this case, the casing conforms to the adjacent wall(s) at least in sections, thus ensuring particularly good heat transfer between the washing container and the latent heat storage material (of course, one or more additional materials, e.g., bitumen, which preferably has a constant thickness, can be arranged between the wall(s) and the adjacent casing).

[0023] According to an advantageous development of the invention, the evaporator has, at least in part, an uneven surface, at least in the region where it is in heat-conducting contact with the latent heat storage material, in order to improve heat transfer between the evaporator and the latent heat storage material. For example, the evaporator could have fins extending into the latent heat storage material to increase the effective heat transfer area between the evaporator and the latent heat storage material. Additionally or alternatively, the evaporator could also be formed by a corrugated tube.

[0024] According to the invention, the latent heat storage material comprises at least one additive, wherein the mixture of latent heat storage material and additive has a higher thermal conductivity than the latent heat storage material. Graphite, copper, or aluminum, or corresponding mixtures of the aforementioned substances, can be used as an additive, preferably homogeneously mixed with the latent heat storage material (which can be in powder form, for example).

[0025] Finally, the advantageous embodiments and further developments of the invention explained above and / or reproduced in the subclaims can generally be used individually or in any combination with one another - except, for example, in cases of clear dependencies or incompatible alternatives.

[0026] Further advantages of the invention are described in the following exemplary embodiments. They show, schematically: Fig. 1 a sectional front view of a partially illustrated dishwasher, Fig. 2 a perspective view of the washing container of a dishwasher according to the invention, and Fig. 3 a sectional front view of a partially illustrated dishwasher constructed according to the invention.

[0027] In the following figures, corresponding parts are provided with the same reference numerals. Only those components of a dishwasher that are necessary for understanding the invention are shown and explained. It goes without saying that the dishwasher according to the invention can comprise additional parts and assemblies.

[0028] It should also be noted that the individual figures always show only selected features. Naturally, the individual features can be combined in any way when implementing the dishwasher according to the invention, as long as the essence of the invention defined in claim 1 is realized.

[0029] Fig. 1 shows a schematic sectional view of a dishwasher, with the section running parallel to the plane of the page, so that the front door with which the dishwasher can be closed is not visible (since it has been cut away).

[0030] In principle, the dishwasher comprises a washing container 3 arranged inside an outer shell (not shown), which generally has two side walls 2, a rear wall 2 (running parallel to the plane of the page), an upper wall 2, and a base region 18 also forming a wall 2. The washing container 3, together with the aforementioned door, defines a receiving space 1 for the items to be cleaned, which can be placed, for example, in corresponding dish baskets 14. Furthermore, the aforementioned walls 2 each have an inner side 4 facing the receiving space 1 and an outer side 5 facing away from the receiving space 1.

[0031] Furthermore, one or more, preferably rotatable, spray nozzles 13 are preferably provided, with the aid of which the items to be washed can be sprayed with washing liquor during corresponding cleaning steps of a washing program.

[0032] During operation of the dishwasher, the washing solution collects in a pump sump 15, from which it is pumped out by means of a pump 17 and fed to the spray nozzles 13 via various lines 16. In addition, further lines 16 are usually connected to the pump sump 15, which can be connected, for example, to a fresh water connection or a waste water connection (these are shown in Fig. 1 are only indicated and run from the pump sump 15 to the right in relation to the page level).

[0033] Furthermore, a control and / or regulating unit 12 is provided in which various washing programs can be stored and which is designed to operate the dishwasher or its individual functional units in accordance with the respectively selected washing program.

[0034] In order to be able to dissipate heat from the washing compartment 3 and temporarily store it, the dishwasher according to the invention has a latent heat storage material 6, which is arranged in the area of ​​one or more of the walls 2 mentioned. By way of example, Fig. 2 a solution in which the two lateral walls 2, the wall 2 in the ceiling area and the wall 2 in the floor area 18 are coated with a mat-shaped flat latent heat storage material 6 (the illustration is limited to the essentials; of course, the Fig. 2 has additional components that are necessary for the operation of the dishwasher; of course, in the case of Fig. 2 a pump sump 15 is present in the floor area 18, even if this is not explicitly shown).

[0035] A particularly preferred arrangement of the latent heat storage material 6 is shown Fig. 3. As can be seen from this figure, the latent heat storage material 6 has a U-shape in the view shown, whereby, if necessary, the rear wall 2 running parallel to the plane of the sheet can also be provided with a latent heat storage material 6.

[0036] Furthermore, a heat pump arrangement 8 is provided, with regard to the individual, in Fig. 3, reference is made to the above description for elements not shown individually (expansion valve, heat exchanger, etc.). In any case, the heat pump assembly 8 comprises an evaporator 7, which is in heat-conducting contact with the latent heat storage material 6.

[0037] In particular, it has proven advantageous if the evaporator 7, as in Fig. 3, is designed as an evaporator tube 9, which extends in a meandering or serpentine manner through the latent heat storage material 6. During operation of the heat pump arrangement 8, a heat transfer medium flows through the evaporator tube 9 and thereby absorbs heat from the latent heat storage material 6. The connection of the evaporator tube 9 with the remaining components of the heat pump arrangement 8 is shown in Fig. 3 is not shown. However, it goes without saying that the evaporator tube 9 has an inlet and an outlet for the heat transfer medium, so that circulation of the heat transfer medium through the evaporator tube 9 is possible.

[0038] In any case, it is advantageous if the evaporator 7 is at least partially embedded in the latent heat storage material 6. Furthermore, it is advantageous if the latent heat storage material 6, as in Fig. 3, is surrounded by a shell 10, which fixes the latent heat storage material 6 in a predetermined position even in the liquid state. Furthermore, the latent heat storage material 6 has at least a large part of a thickness D (see Fig. 3), the amount of which is in the range already mentioned above.

[0039] Finally, the latent heat storage material 6 may comprise one or more additives 11 (in Fig. 2 as small dots), which cause the thermal conductivity of the mixture of latent heat storage material 6 and additive(s) 11 to be higher than that of the latent heat storage material 6 alone.

[0040] Furthermore, the invention is not limited to the illustrated embodiment. Rather, all combinations of the described individual features, as shown or described in the claims, the description, and the figures, and to the extent that such a combination appears technically possible or reasonable, are the subject of the invention.

[0041] One aim of the invention is, among other things, to operate a dishwasher more energy-efficiently using a heat pump. The heat source can play a crucial role in this.

[0042] Existing solutions typically use closed PCM storage units in the base support area of ​​the dishwasher as a heat source. Thermal regeneration occurs over several hours through the environment. Disadvantages include limited installation space and long regeneration times. Some manufacturers also require a fan to provide the storage unit with the necessary thermal energy for regeneration.

[0043] The PCM storage used can be characterized by being positioned on the outer walls of the rinse tank. The heat pump's evaporator is thermally coupled to the PCM. To increase the PCM / evaporator contact area, specific fin geometries can be attached to the evaporator. The PCM can be mixed with various additives to increase thermal conductivity. Encapsulated PCM materials can be used (e.g., encapsulated by a thin-walled PP blown part as a container). The phase change temperature should be within the following range: TPCM >0°C and TPCM <23°C.

[0044] The advantages are: - Installation space in the base carrier is available for other components. - Waste heat from the dishwasher is stored again in the attached PCM storage units. - Increased COP of the heat pump expected. - Less condensation of the ambient air at the PCM storage is to be expected due to higher temperatures of the PCM storage. - Due to the low thermal conductivity of the PCM, an insulation element between the flushing tank and the PCM storage tank can be omitted or significantly reduced. - Higher heating rates in the dishwasher are to be expected due to the lower temperature difference between the washing container and the PCM storage tank. - Contours of the dishwasher can be well reproduced with the PCM wall. List of reference symbols 1 recording room 2 wall 3 rinsing containers 4 Inside of the wall 5 Outside of the wall 6 Latent heat storage material 7 evaporators 8 Heat pump arrangement 9 Evaporator tube 10 Cover 11 Addition 12 Control and / or regulation unit 13 Spray nozzle 14 Dish basket 15 Pump sump 16 Line 17 Pump 18 Floor area D Thickness of the latent heat storage material

Claims

[1] Dishwasher with a receiving space (1) serving to receive items to be cleaned, wherein the receiving space (1) is delimited to the outside by walls (2) of a washing container (3) and a door, wherein the walls (2) each have an inner side (4) facing the receiving space (1) and an outer side (5) facing away from the receiving space (1), and wherein in the region of the outer side (5) of at least one of the walls (2) a flat latent heat storage material (6) is arranged, which is in heat-conducting contact with an evaporator (7) of a heat pump arrangement (8) of the dishwasher, wherein the heat pump arrangement (8) is designed to transfer heat from the latent heat storage material (6) to a washing liquor circulating at least temporarily within the dishwasher during operation of the dishwasher, characterized bythat the latent heat storage material (6) has at least one additive (11), wherein the mixture of latent heat storage material (6) and additive has a higher thermal conductivity than the latent heat storage material (6). [2] Dishwasher according to the preceding claim, characterized by that the latent heat storage material (6) has a phase change temperature whose value is between 0 °C and 30 °C, preferably between 10 °C and 25 °C. [3] Dishwasher according to one of the preceding claims, characterized by that the latent heat storage material (6) has, at least in sections, a thickness (D) running perpendicular to the respective adjacent wall (2), the amount of which is 3 mm to 50 mm, preferably 10 mm to 40 mm. [4] Dishwasher according to one of the preceding claims, characterized bythat the evaporator (7) has at least one evaporator tube (9), wherein the evaporator tube (9) is at least partially embedded in the latent heat storage material (6). [5] Dishwasher according to claim 4, characterized by that the evaporator tube (9) runs through the latent heat storage material (6) in a serpentine manner. [6] Dishwasher according to one of the preceding claims, characterized by that the latent heat storage material (6) extends over at least one lateral wall (2) of the rinsing container (3). [7] Dishwasher according to one of the preceding claims, characterized by that the latent heat storage material (6) extends over at least 70%, preferably over at least 80%, of the outer side (5) of at least one wall (2) adjacent to the latent heat storage material (6). [8] Dishwasher according to one of the preceding claims, characterized bythat the latent heat storage material (6) extends over two side walls (2) and an upper wall (2) of the washing container (3), so that the latent heat storage material (6) has a U-shaped form in a front view of the dishwasher. [9] Dishwasher according to one of the preceding claims, characterized by that the latent heat storage material (6) is surrounded by a dimensionally stable shell (10). [10] Dishwasher according to claim 9, characterized by that the casing (10) is formed by a plastic molded part. [11] Dishwasher according to claim 9 or 10, characterized by that an outer surface of the casing (10) facing the outer side (5) of a wall (2) of the rinsing container (3) is adapted at least in sections to the contour of said outer side (5). [12] Dishwasher according to one of the preceding claims, characterized bythat the evaporator (7) has at least partially an uneven surface, at least in the region in which it is in heat-conducting contact with the latent heat storage material (6), in order to improve the heat transfer between the evaporator (7) and the latent heat storage material (6).

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