dishwasher

Abstract

Dishwasher with a wash tank (2) providing a wash chamber (3), a spray device (4) for supplying wash liquor to the items to be cleaned, wherein the spray device (4) is connected to a supply line (5) arranged inside the wash tank (2) for supplying the wash liquor, with a circulation pump (10) for conveying the wash liquor through the supply line (5) to the spray device (4) and with a heat pump for heating the wash liquor, wherein the heat pump has a condenser (6) with two coaxially arranged pipes (7, 8), one of which is a refrigerant pipe (7) and the other a wash liquor pipe (8), characterized by that the flushing liquor pipe (8) is arranged as a bypass line (9) to the supply line (5) at least partially outside the flushing tank (2) and has an inner diameter of 3.5 mm to 9 mm, wherein the pipes (7, 8) of the condenser have a length of 1.0 m to 2.7 m, and wherein the bypass line (9) is directly connected to the circulation pump (10) on both the suction and pressure sides.

Description

[0001] The invention relates to a dishwasher with a washing container providing a washing chamber, a spray device for supplying washing liquid to the items to be cleaned, wherein the spray device for supplying washing liquid is connected to a supply line arranged inside the washing container, and with a heat pump for heating washing liquid, wherein the heat pump has a condenser with two coaxially arranged pipes, one of which is a refrigerant pipe and the other a washing liquid pipe.

[0002] Typical dishwashers have a wash chamber that provides a washing area. When used as intended, the wash chamber serves to hold the items to be cleaned, especially dishes and / or cutlery.

[0003] A spray system located inside the wash tub serves to fill the dishes to be cleaned with cleaning solution. This system typically has several spray arms mounted so they can rotate around a common axis. Usually, there are two or three such spray arms inside the wash tub, arranged one above the other in the vertical direction of the dishwasher.

[0004] A supply line provides the spray arms with cleaning solution. This line is connected to a circulation pump on the loading side. In the prior art, embodiments are known in which the supply line for the spray device is located outside the wash tub. The present invention, however, relates to a dishwasher in which the supply line for the spray device is arranged inside the wash tub.

[0005] Dishwashers of the type mentioned above have been known for some time, which are equipped with heat pump circuits to reduce energy consumption, especially during the heating phase of the dishwasher, since the heating process accounts for the largest share of the dishwasher's energy consumption.

[0006] Such a heat pump cycle serves, for example, to extract heat energy from the ambient atmosphere, i.e., the air surrounding the dishwasher, and transfer it to the wash water circulating inside the dishwasher. A typical heat pump cycle generally includes an evaporator, a compressor, a condenser, and a flow circuit that connects these components. The condenser acts as a heat exchanger.

[0007] From DE10 2011 000 042 A1, a method for heating the dishwashing liquid of a dishwasher using an air-to-water heat pump is known as follows. During the heating phase of a dishwasher, room air is drawn in by fans and passed over the evaporator of the heat pump. This cools the supplied room air, and the heat energy extracted from the room air is transferred to a working medium, for example, a refrigerant, which consequently evaporates. The working medium, now in gaseous form, is then compressed in a compressor and thus brought to a higher temperature. Finally, the gaseous working medium is introduced into the condenser, where it liquefies, releasing energy. The released heat energy is used to heat the dishwashing liquid.

[0008] To transfer the heat energy released during the condensation of the refrigerant to the cleaning solution, so-called coaxial tube heat exchangers are also known as condensers. Such heat exchangers have two tubes: a refrigerant tube, which serves to transport the working fluid (i.e., the refrigerant), and a cleaning solution tube, through which cleaning solution is passed during normal use. As described in the subsequently published application EP 2682039 A1, the cleaning solution tube can be arranged, in particular, inside the refrigerant tube, so that, during normal use, heat transfer can occur from the working fluid carried in the refrigerant tube to the cleaning solution tube located inside the refrigerant tube, and thus also to the cleaning solution passing through the cleaning solution tube.

[0009] If the supply line for the spray unit with cleaning solution is located outside the dishwasher's wash tank, the supply line itself can serve as the cleaning solution pipe of such a coaxial tube heat exchanger, as described in subsequently published application EP 2682039 A1. This has the particular advantage that no additional dead volume is created by further piping. However, if the supply line is located inside the wash tank, a condenser in the previously known form of a coaxial tube heat exchanger cannot be used.

[0010] EP 2215954 A1 discloses a dishwasher with a heat pump which has an evaporator by means of which heat is transferred from the washing liquor discharged in a drain pipe to a refrigerant circulated in a refrigerant pipe.

[0011] The object of the invention is to provide an alternative embodiment to the previously described construction, which offers safety in everyday practical use while maintaining high efficiency.

[0012] To solve this problem, the invention proposes a dishwasher with the features of claim 1.

[0013] The invention still provides a condenser in the form of a coaxial tube heat exchanger. To enable this, however, the invention proposes a bypass line running parallel to, i.e., alongside, the supply line, with the condenser's purge pipe serving as this bypass line. In the intended use, a portion of the purge circulated by the circulation pump and conveyed through the supply line is diverted and routed via the purge pipe of the coaxial tube heat exchanger. The purge pipe is preferably located within the refrigerant line of the condenser.

[0014] The bypass line provided according to the invention results in the disadvantage of an additional dead volume. This disadvantage is deliberately accepted in light of the advantages associated with a coaxial tube heat exchanger and is further minimized by the fact that, according to the invention, the flushing liquor tube is designed with regard to its geometric dimensions, preferably exclusively with the aim of optimizing heat transfer from the refrigerant to the flushing liquor. Designs known from the prior art do not allow for such optimization. In this respect, the design according to the invention proves to be advantageous, despite the bypass line, in contrast to solutions known from the prior art.This ensures operational reliability, especially with simultaneous efficiency in heat recovery, simplifies initial assembly, improves access in case of repairs, and creates the possibility of retrofitting.

[0015] If the supply line for the spray system were routed outside the rinsing tank, the design of a coaxial tube heat exchanger would be comparatively simple, because the supply line, which is already located outside the rinsing tank, could serve as the rinsing liquor pipe of a coaxial tube heat exchanger. The supply line, and therefore also the portion of the supply line that serves as the rinsing liquor pipe, must be designed with the supply line and the rinsing liquor supplying the spray system in mind. In particular, the supply line's inner diameter must be such that the required flow rate of rinsing liquor can reach the spray system. Furthermore, the length of such a supply line in the flow direction must be adapted to the height of the rinsing tank and limited accordingly to avoid creating dead volume.Consequently, it is not possible to design the heat exchanger for the purpose of optimized heat transfer.

[0016] The inventive design provides a remedy for this problem. The spray device is supplied via the supply line located within the cleaning chamber. This supply line, particularly its diameter, can be optimized for the precise supply of cleaning solution to the spray device, ensuring the desired level of cleaning solution flow. The cleaning solution pipe of the coaxial tube heat exchanger, which bypasses the supply line, can be designed with a focus on efficient heat transfer, since, unlike the prior art, the spray device is supplied via the supply line located within the cleaning chamber and not via the cleaning solution pipe of the coaxial tube heat exchanger. This advantageously ensures both an optimized supply of cleaning solution and optimized heat transfer within the heat pump circuit.

[0017] Preferably, the heat pump is an air-to-water heat pump in which, during the dishwasher's heating phase, room air is drawn in by fans and passed over the heat pump's evaporator. This cools the incoming room air, and the heat energy extracted from the room air is transferred to a working fluid, such as a refrigerant, which then evaporates. The working fluid, now in gaseous form, is subsequently compressed in a compressor, thus raising its temperature. Finally, the gaseous working fluid is introduced into the condenser, where it liquefies, releasing energy. The released heat energy is used to heat the dishwashing liquid.

[0018] The heat exchangers of typical heat pumps provide approximately 500 W of heating power. For this to be achieved, a minimum of 0.5 l / min of cleaning fluid should flow through the heat exchanger. The efficiency increases with increasing cleaning fluid flow rate.

[0019] Since the heat exchanger according to the invention is operated in bypass mode, an upper limit for the volume flow rate must be considered, as the bypass volume flow rate is lost to the supply of cleaning solution to the spray device. Typical circulation pumps circulate approximately 35 to 60 l / min at their operating point. The bypass volume flow rate should be limited to approximately 20% of this, thus approximately 7 to 12 l / min.

[0020] The heat exchanger surface area should be approximately 300 cm². 2 Smaller heat exchanger surfaces reduce efficiency, while larger heat exchanger surfaces require increased material consumption, more installation space, and a larger dead volume.

[0021] Taking these boundary parameters into account, the invention proposes that the flushing liquor pipe has an inner diameter of 3.5 mm to 9 mm, preferably 5 mm to 7 mm. (To be continued for 300 cm) 2 To achieve the required heat exchange surface area, a pipe length of approximately 2.7 m is needed for an inner diameter of 3.5 mm. This results in a dead volume of only 26 ml. At a flow rate of 0.5 l / min, a straight pipe of this length has a pressure drop of approximately 150 mbar.

[0022] With an inner diameter of 9 mm and a heat exchanger surface of 300 cm², this results in 2 A pipe length of 105 cm results in a dead volume of approximately 67 ml. At a flow rate of 11 l / min, this results in a pressure loss of 150 mbar.

[0023] However, an inner diameter of 5 mm to 7 mm is particularly preferred. With a diameter of this size, a flow rate of 1.6 l / min to 5 l / min is advantageously achieved. For an inner diameter of 5 mm, this results in a pipe length of 1.9 m for the desired heat exchanger surface area of ​​300 cm². 2 And this with a dead volume of only 37 ml.

[0024] At a flow rate of 1.6 l / min, a straight pipe has a pressure drop of almost 150 mbar and a temperature increase of approximately 4.7°C is achieved with a heating power of 500 W.

[0025] With an inner diameter of 7 mm, the pipe length is approximately 1.35 m, resulting in a dead volume of only 52 ml. At a flow rate of 5 l / min, this results in a temperature increase of only 1.5°C.

[0026] In the preferred area of ​​the inner diameter design, a good compromise is thus achieved between the smallest possible volume flow and dead volume on the one hand and a low temperature rise on the other.

[0027] According to the design parameters above, a coaxial tube heat exchanger requires a tube length of 1.05 m to 2.7 m, which cannot be accommodated as a straight tube in a standard dishwasher. Therefore, the invention proposes to design the coaxial tube heat exchanger in a spiral shape with multiple windings. For example, in a 1.35 m long exchanger with an inner diameter of 7 mm, four turns could be wound into a spiral with a spiral diameter of approximately 11 cm. To save space, one or more other components of the heat pump, such as the compressor and / or an expansion valve, can also be arranged inside the spiral.

[0028] The shape of the heat exchanger wound into a spiral does not necessarily have to be circular. Other shapes can be chosen, such as oval shapes or even shapes of any regular or irregular polygon with rounded corners.

[0029] Another embodiment of the invention provides for bending the coaxial tube heat exchanger in a meandering shape, so that the overall shape remains flat and can be inserted, for example, into the side wall between the washing container and the housing of the dishwasher.

[0030] To improve thermal insulation, a further feature of the invention proposes to design the condenser with thermal insulation. Preferably, not each individual tube is insulated separately, but rather the entire heat exchanger is insulated. Particularly when other components are arranged inside a heat exchanger, for example, one designed as a spiral, it is advantageous to insulate not the entire spiral, but several turns together.

[0031] To minimize harmful dead volume, the invention further proposes connecting the bypass line directly to the circulation pump on both the suction and pressure sides. Furthermore, to prevent carryover of the flushing solution from one sub-program step to the next, it is advantageous to connect the coaxial tube heat exchanger to the circulation pump in such a way that the heat exchanger can drain itself under its own weight.

[0032] Further features and advantages of the invention will become apparent from the following description with reference to the figures. Fig. 1 in schematic representation a dishwasher according to the invention; Fig. 2 in schematic representation a dishwasher according to EP 2682039 A1; Fig. 3 in a schematic section view the dishwasher according to the invention Fig. 1; Fig. 4 in a schematic view a coaxial tube heat exchanger according to the invention and Fig. 5 in schematic view a heat exchanger according to Fig. 4 according to a preferred embodiment.

[0033] The Fig. 1 and Fig. Figure 2 each schematically depicts a dishwasher 1, wherein Fig. 1 the inventive design and Fig. 2 concerns a design according to EP 2682039 A1.

[0034] The dishwasher 1 has a wash container 2. This provides a wash chamber 3 which, in its intended use, serves to hold the items to be cleaned.

[0035] A spray device 4, located inside the washing container 2, serves to supply the items to be cleaned with cleaning solution. A spray device 4 typically has a plurality of rotatably arranged spray arms, whereby in the illustrated embodiment only the upper arm of such a spray device 4 is shown by way of example.

[0036] The rinsing chamber 3 empties into a collection container (not shown) to which a circulation pump 10 is connected. The spray device 4 is fluidically connected to the circulation pump 10, so that, under normal operating conditions, the spray device 4 can be supplied with rinsing solution by means of the circulation pump 10.

[0037] According to the embodiment according to EP 2682039 A1 Fig. 2. The spray device 4 is fluidically connected to the circulation pump 10 by means of a supply line 5. This line is laid outside the flushing tank 2 and runs as a flushing liquor pipe 8 through a refrigerant pipe 7 of a condenser 6, which serves as a coaxial tube heat exchanger, of a heat pump (not shown in detail below). In the intended operating condition, refrigerant condenses in the refrigerant pipe 7, releasing heat which is transferred to the flushing liquor pipe 8 and thus to the flushing liquor flowing through it.

[0038] The flushing liquor pipe 8 or the supply line 5 is geometrically designed to ensure proper supply of flushing liquor to the spray device 4.

[0039] The embodiment according to the invention is in Fig. 1 shown. As can be seen from this illustration, a supply line 5 is provided to supply the spray device 4 with rinsing solution, which, unlike the Fig. 2 is not located outside the washing tank 2, but inside the washing tank 2. For heat transfer, a condenser 6 in the form of a coaxial tube heat exchanger is provided, whereby, in contrast to the Fig. 2. The flushing liquor pipe 8 is designed as a bypass line 9. The bypass line 9 is preferably connected directly to the circulation pump 10 on both the suction and pressure sides in order to avoid the formation of an unnecessary dead volume.

[0040] In contrast to the embodiment according to Fig. 2. The supply line 5 itself does not pass through the refrigerant pipe 7 of the condenser 6, but instead a bypass line 9 is routed in a bypass to the supply line 5. The advantage of this design is that the geometric dimensions of the bypass line 9 are designed solely with regard to optimized heat transfer from the refrigerant to the cleaning solution. In contrast to the design according to Fig. 2. No design of the bypass line 9 is required with regard to the proper supply of the spray device 4 with cleaning solution, because the supply line 5 laid in the interior of the cleaning tank 2 serves this purpose. As a result of this design innovation, on the one hand an optimized design for the supply of the spray device 4 with cleaning solution and on the other hand an optimized design with regard to heat transfer in the condenser 6, which is designed as a coaxial tube heat exchanger.

[0041] According to a preferred embodiment, the flushing liquor pipe 8 has an inner diameter of 5 mm to 7 mm. With a total heat exchanger surface area of ​​300 cm² 2This results in a length of 1.9 m with an inner diameter of 5 mm, or a pipe length of 1.35 m with an inner diameter of 7 mm. To accommodate a heat exchanger 6 with such a pipe length in the housing of the dishwasher 1, the invention provides for the coaxial tube heat exchanger to be designed in a spiral shape, as is the case with the Fig. 3 and Fig. 4. It is preferred to provide a total of four spiral turns with a spiral diameter of approximately 11 cm. For the purpose of optimized space utilization, it is planned to provide further components within the spiral, i.e., to route the spirally shaped coaxial tube heat exchanger around other components of the heat pump.

[0042] To avoid unnecessary dead volume in the system, as in Fig. As can be seen in Figure 3, it is also proposed to connect the condenser 6, designed as a coaxial tube heat exchanger, directly to the circulation pump 10 and not to the collection tank 11, with a direct connection 12 or 13 being provided on both the suction and pressure sides of the circulation pump 10.

[0043] For better thermal insulation, it shows Fig. 5 a preferred embodiment in which an insulating material 14 is provided that surrounds the entire condenser 6. In this embodiment, not the coils of the condenser 6 are completely surrounded by insulating material, but only the individual coils, as shown in the cross-sectional view according to Fig. 5 can be seen. The insulation made of the insulating material 14 is therefore ring-shaped. Reference sign 1 dishwasher 2 washing containers 3. Dishwashing area 4 Spray device 5 Supply line 6 liquefiers 7 Refrigerant pipe 8 flushing pipe 9 Bypass line 10 Circulation pump 11 Collection pot 12 connection 13 connection 14 Insulation material

Claims

[1] Dishwasher with a wash tank (2) providing a wash chamber (3), a spray device (4) for supplying wash liquor to the items to be cleaned, wherein the spray device (4) is connected to a supply line (5) arranged inside the wash tank (2) for supplying the wash liquor, with a circulation pump (10) for conveying the wash liquor through the supply line (5) to the spray device (4) and with a heat pump for heating the wash liquor, wherein the heat pump has a condenser (6) with two coaxially arranged pipes (7, 8), one of which is a refrigerant pipe (7) and the other a wash liquor pipe (8), characterized by , that the flushing liquor pipe (8) is arranged as a bypass line (9) to the supply line (5) at least partially outside the flushing tank (2) and has an inner diameter of 3.5 mm to 9 mm, wherein the pipes (7, 8) of the condenser have a length of 1.0 m to 2.7 m, and wherein the bypass line (9) is directly connected to the circulation pump (10) on both the suction and pressure sides. [2] Dishwasher according to claim 1, characterized by that the flushing liquor pipe has an inner diameter of 5 mm to 7 mm. [3] Dishwasher according to claim 1, characterized by , that the pipes (7, 8) of the condenser have a length of 1.35 m to 1.9 m. [4] Dishwasher according to any one of the preceding claims, characterized by , that the heat exchanger surface between the flushing liquor pipe (8) and the refrigerant pipe (7) is 300 cm² 2 amounts. [5] Dishwasher according to any one of the preceding claims, characterized by , that the pipes (7, 8) of the condenser (6) are wound in a spiral shape. [6] Dishwasher according to claim 5, characterized by, that the tubes (7, 8) are wound into a spiral with four turns with a turn diameter of 8 cm to 15 cm, preferably of 11 cm to 13 cm. [7] Dishwasher according to claim 5 or 6, characterized by that the spiral has a shape that deviates from a circular one. [8] Dishwasher according to any one of the preceding claims 1 to 4, characterized by , that the pipes (7, 8) of the condenser are laid in a meandering pattern. [9] Dishwasher according to any one of the preceding claims, characterized by , that the condenser (6) is designed to be thermally insulated.

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