EP2190336B1 - Dishwasher having means for changing heat dissipation - Google Patents

Description

The present invention relates to a dishwasher according to the preamble of claim 1.

From the DE 103 46 964 A1 For example, a dishwasher is known in which the walls have insulation that is variable in thermal conductivity. As a result, the thermal barrier coating can be adjusted during a flushing operation so that only a low thermal conductivity is present and the heat energy is maintained in the flushing chamber. During the drying process, however, the thermal conductivity can be increased, so that the removal of heat energy, an inner wall is cooled, and then to accelerate the dehumidification by condensation. In order to vary the thermal conductivity, hydrogen is released in a metal hydride grid, which then changes the thermal conductivity. The use of such a metal hydride grid in a thermal barrier coating is comparatively expensive, since electrical heating means for operating the thermal barrier coating must also be present.

Other commercially available dishwashers have a washing compartment with surrounding walls, which are thermally insulated by an insulating layer. For example, bitumen is provided as the insulating layer, although no change in the thermal conductivity of such insulating layers is possible. Therefore, the heat conductivity remains constant, regardless of whether during the flushing operation, the heat is to be kept in the washing compartment or if the heat from the washing compartment should be dissipated as well as possible during the drying operation to cool an inner wall and to accelerate the condensation.

From the DE 196 22 882 A1 a dishwasher is known in which a latent heat storage with the interposition of an intermediate layer with the Spülraumwandaußenseite is in surface heat contact. The intermediate layer is so variable that it is thermally conductive during the dry phase, but otherwise is substantially heat-insulating.

It is an object of the present invention to provide a dishwasher, which allows a variable design of the heat transfer to at least one wall with a simple structure.

This object is achieved with a dishwasher having the features of claim 1. Advantageous embodiments emerge from the subclaims.

According to the invention, the walls, which are surrounded by an insulating layer, have, at least in regions, on the outside, a layer whose emissivity can be changed. As a result, the heat contained in a flushing chamber can be retained as well as possible during the flushing operation, while in the drying operation at least partial heat can be released by increased heat radiation. In this case, no change in the thermal conductivity of the insulating layer is required, but a different heat radiation is used to make the operation of the dishwasher as efficient and energy-efficient. This includes keeping the energy losses as low as possible during the rinsing period, while increasing the heat radiation during the drying process.

In this case, the layer may be changeable in color, for example as a function of the temperature. Furthermore, it is possible that the emissivity of the layer is variable via pulses from a controller. In this case, the layer can be adjusted so that at high temperatures, a high emissivity is present, while at somewhat lower temperatures, a lower heat radiation occurs. Because just before the drying program usually a particularly high temperature is introduced into the washing compartment, so that then a high heat radiation is necessary for the subsequent drying process.

It is known that dark matte surfaces have high heat radiation, but bright shiny surfaces are very low. For example, bitumen has an emission coefficient of almost 1, a glossy surface, for example bitumen coated with aluminum foil, has an emission coefficient of about 0.16. Experiments have shown that a dishwasher with coated bitumen for a total Spülprogrammablauf (standard program) has a by about 40 Wh lower energy consumption than uncoated bitumen. In this respect, the difference in heat radiation through a different surface design can also be used for optimizing the program sequence of a dishwasher.

In a further embodiment of the invention it is provided that at least partially pivotable slats are provided on the outside. These fins may have a reflective surface and be movable to change the heat radiation from a closed position to an open position. Such a slatted curtain can be arranged on a side wall of a dishwasher in order to be able to change the heat radiation over the corresponding wall surface. A pivoting of the slats can preferably be carried out when switching between cleaning process and drying process.

The invention will be explained in more detail below with reference to two exemplary embodiments: According to a first embodiment, a dishwasher comprises a washing chamber surrounded by walls, the walls having a watertight inner wall and an outer insulating layer of bitumen. At least on one wall of the washing compartment, a lamellae curtain is provided which has a plurality of pivotable lamellae, which are provided on one side with a reflective surface. During the flushing operation, the heat radiation should be kept low, so that the lamellae with their reflective surface face the insulating layer of bitumen. As a result, heat radiated from the dark bitumen is reflected, for example by corresponding color design of the lamellae or a coating with an aluminum foil. For the drying process, the slats are pivoted, so that now the heat radiation can pass through the slats. Behind the slatted curtain further units are arranged, for example, water bags, drying unit or other components, so that any heat radiation is not reflected directly from an outer wall. In this respect, the insulating layer is in the closed state against a bright reflective surface, while allow for the drying process, the lamellae in the open position, a heat radiation.

According to a second embodiment of the invention, a dishwasher with a surrounding walls is provided in which at least partially on the outside of the walls on the insulating layer, a coating is provided, the emissivity of which is variable. In this case, the change can be effected by a direct influence of the control (for example by an electrical impulse), or also indirectly by the fact that, starting from a certain temperature, a reversible change in the emissivity occurs. You can use colors with a function that depends on the temperature. For example, the temperature required for the color change may be selected such that a lower emissivity (low heat radiation losses) at a lower temperature and a high emissivity (high heat radiation losses) at a predetermined reversal temperature are present. This ensures that in the normal rinsing process with low temperatures tends to cause low losses and in the drying step with high temperatures tend to contribute high losses to drying support.

Such a coating preferably consists of polymer microcapsules (diameter about 6 microns), which are filled with coloring components and a medium, wherein the state of matter of the medium may be liquid or solid. Below the temperature at which the medium changes from liquid to solid, the coloring components are in direct contact and the particular color appears. Above the temperature at which the medium changes from the state of aggregation to liquid, the coloring components are no longer in direct contact and the particular color is not visible. This process is reversible, with a hysteresis between the pass from cold to warm and back from warm to cold, so that the temperature at which no color is visible is slightly higher than the temperature at which the color reappears.

The color change temperature is preferably in a range between 50 ° and 90 °, in particular 60 ° to 70 °.

Of course, it is also possible to combine the two embodiments described above with one another, that is to say to provide both a lamellae curtain and at least partially to apply a coating with a change in the emissivity to the insulating layer.

Claims (7)

1. Dishwasher comprising a washing chamber enclosed by walls, the walls comprising a watertight internal wall and an insulation layer, at least one wall comprising, at least in regions on the exterior thereof, means for changing the radiation of heat, characterised in that the means for changing the radiation of heat comprise a layer of which the emissivity can be changed.
2. Dishwasher according to claim 1, characterised in that the colour of the layer can be changed.
3. Dishwasher according to claim 2, characterised in that the colour of the layer can be changed as a function of temperature.
4. Dishwasher according to any of claims 1 to 3, characterised in that the emissivity of the layer can be changed via pulses from a control unit.
5. Dishwasher according to claim 4, characterised in that the colour of the layer can be changed via pulses from a control unit.
6. Dishwasher according to any of claims 1 to 5, characterised in that pivotable slats are provided at least in regions on the exterior of said wall.
7. Dishwasher according to claim 6, characterised in that the slats have a reflective surface and are movable from a closed position into an open position for changing the radiation of heat.