The invention relates to a method for freeing a fluid, which is picked up by a desiccant, from said desiccant. The invention further relates to a household appliance component and to a household appliance having means for regenerating a desiccant.

Desiccants are widely used for various purposes because of their capacity to adsorb and/or absorb water and other fluids. In most applications, desiccants induce dryness in the environment and reduce the amount of present moisture. In other applications, desiccants are used to accelerate the water phase transition from liquid to steam. Some desiccants are chemically inert while others are reactive and require specialized handling techniques. The most common desiccant is silica, an inert, nontoxic, water-insoluble white solid. Once the desiccant is saturated, it is necessary to reverse the adsorption/absorption process by desorbing the fluid from the desiccant, in order to prepare the desiccant for the next working cycle.

The common way of desorbing the picked-up fluid from the desiccant, a process called "regeneration", is usually made by warming the desiccants up to certain temperatures by applying heat with infrared heat sources (radiation) or by applying a stream of purge gas. These methods, however, take a considerable amount of time and energy to remove the adsorbed fluid volume from the desiccant.

It is the task of the present invention to provide a method for freeing a fluid, which is picked up by a desiccant, from said desiccant, in a faster and more efficient way. A further task of the invention consists in providing a household appliance component which is able to regenerate a desiccant in a faster and more efficient way. Still further, it is an object of the current invention to provide a household appliance comprising at least one household appliance component which is able to regenerate a desiccant in a faster and more efficient way. These tasks are solved by a method, a household appliance component, and a household appliance according to the independent claims. Advantageous developments of the invention are specified in the respective dependent claims, wherein advantageous developments of a specific aspect of the invention are to be regarded as advantageous developments of all other aspects of the invention and vice versa.

A first aspect of the invention relates to a method for freeing a fluid, which is picked up by a desiccant, from said desiccant. A faster and more efficient way for regenerating said desiccant is achieved by the steps of bringing the desiccant comprising the picked-up fluid into contact with a carrier, wherein the carrier comprises openings and has a thermal conductivity λ of at least 10 W/(m*K) at 0 °C, heating the carrier up to a predetermined temperature, and freeing at least part of the fluid from the desiccant by transferring heat energy from the carrier to the desiccant. The predetermined temperature depends on the properties of the specific desiccant. As has already been stated, the way to desorb fluid from a desiccant according to the prior art is by warming it up, because desorption (regeneration) is favoured at high temperatures. However, this process is slow and inefficient, because radiation or convection are used for heating up the desiccant. Thus, according to the prior art, air around the desiccant is first heated. Afterwards heat is transferred slowly from the air to the desiccant due to the low thermal conductivity of air. Air, however, only has a thermal conductivity λ of approximately 0.0262 W/(m*K) at 0 °C. In contrast thereto, according to the method of the present invention the desiccant is brought into contact with a carrier which is made of a material having a high thermal conductivity λ of at least 10 W/(m*K) (measured at 0 °C). A thermal conductivity λ of at least 10 W/(m*K) comprises for example λ values of 10 W/(m*K), 20 W/(m*K), 30 W/(m*K), 40 W/(m*K), 50 W/(m*K), 60 W/(m*K), 70 W/(m*K), 80 W/(m*K), 90 W/(m*K), 100 W7(m*K), 1 10 W/(m*K), 120 W/(m*K), 130 W/(m*K), 140 W/(m*K), 150 W/(m*K), 160 W/(m*K), 170 W/(m*K), 180 W/(m*K), 190 W/(m*K), 200 W/(m*K), 210 W7(m*K), 220 W/(m*K), 230 W/(m*K), 240 W/(m*K), 250 W/(m*K), 260 W/(m*K), 270 W/(m*K), 280 W/(m*K), 290 W/(m*K), 300 W/(m*K), 310 W/(m*K), 320 W/(m*K), 330 W/(m*K), 340 W/(m*K), 350 W/(m*K), 360 W/(m*K), 370 W/(m*K), 380 W/(m*K), 390 W/(m*K), 400 W7(m*K), 410 W/(m*K), 420 W/(m*K) or more (measured at 0 °C). Thus, by using said carrier, heat is transferred by conduction and therefore much faster to the desiccant than in conventional heating modes (radiation or convection) because the carrier has a much higher thermal conductivity λ and is in direct contact with the desiccant. Therefore the carrier and the desiccant are heated up more quickly so that fluid, e. g. water, which has been picked-up or adsorbed/absorbed (chemisorption) by the desiccant, is rapidly desorbed and can exit the carrier through the openings, resulting in a fast and energy efficient regeneration of the desiccant. According to an advantageous development of the invention, the desiccant comprising the picked-up fluid is embedded in a carrier having a mesh and/or foam geometry and/or wherein the desiccant comprising the picked-up fluid is arranged on a storage area of the carrier with a coarse surface structure and/or wherein the carrier defines a desiccant containing chamber, in which the desiccant is arranged. This allows for a homogenous distribution of the desiccant within and/or on the carrier, an intimate contact between desiccant and carrier, and thus for a particularly fast heat transfer and regeneration of the desiccant. The design of the carrier, e.g. a mesh or a foam structure, can be chosen based on the heating method that will be used and the size and shape of the desiccant. For example, the carrier can have a three-dimensional structure made of two or more mesh layers disposed upon each other, or may be a porous foam, in which the desiccant particles are distributed homogeneously. Additionally or alternatively, the carrier may be a (horizontal) plate with a coarse surface on which the desiccant particles are distributed to increase the contact surface with the carrier and thus the heat transfer rate. Still further, the carrier may define a desiccant containing chamber in which the desiccant is arranged. The carrier may for example be a tubular mesh which is filled with the desiccant.

In a further advantageous development of the invention, the carrier is heated up to said predetermined temperature by one or more of induction heating, electrical heating, and radiant heating. The method is thus easily adaptable to different heating devices and can thus be employed in different home appliances.

In a further advantageous development of the invention it is provided that a gas is passed through the openings of the carrier to remove at least part of the freed fluid from the desiccant. This step accelerates the regeneration of the desiccant since desorbed fluid is transported by the gas away from the desiccant and cannot be readsorbed/reabsorbed by the desiccant. This step can also be used to essentially remove the entire picked-up fluid volume from the desiccant to achieve a complete regeneration.

In a further advantageous development of the invention it is provided that the carrier consists of a metal, in particular aluminum and/or copper, or a metal alloy, in particular steel and/or an aluminum alloy. Metals and/or metal alloys such as for example steel or aluminum are inexpensive and have good thermal conductivity values λ of at least 15 W/(m*K). Further, metals and metal alloys can easily be heated by applying an electrical current, i.e. by using the carrier as a heating resistor. This is an easy, fast and inexpensive method to heat the carrier and thus the desiccant.

A second aspect of the invention relates to a household appliance component comprising a carrier, which is in contact with a desiccant for picking up fluid, wherein the carrier comprises openings and has a thermal conductivity λ of at least 10 W/(m*K) at 0 °C, and a heating device which is configured to heat the carrier up to a predetermined temperature such that at least part of the fluid, which has been picked up by the desiccant, is freed from the desiccant by transferring heat energy from the carrier to the desiccant. The household appliance component according to the present invention in other words comprises a desiccant, which is in contact with a carrier. The carrier is made of a material having a high thermal conductivity λ of at least 10 W/(m*K) (measured at 0 °C). A thermal conductivity λ of at least 10 W/(m*K) comprises for example λ values of 10 W/(m*K), 20 W/(m*K), 30 W/(m*K), 40 W/(m*K), 50 W/(m*K), 60 W/(m*K), 70 W/(m*K), 80 W/(m*K), 90 W/(m*K), 100 W/(m*K), 1 10 W/(m*K), 120 W/(m*K), 130 W/(m*K), 140 W/(m*K), 150 W/(m*K), 160 W/(m*K), 170 W/(m*K), 180 W/(m*K), 190 W/(m*K), 200 W/(m*K), 210 W7(m*K), 220 W/(m*K), 230 W/(m*K), 240 W/(m*K), 250 W/(m*K), 260 W/(m*K), 270 W/(m*K), 280 W/(m*K), 290 W/(m*K), 300 W/(m*K), 310 W/(m*K), 320 W/(m*K), 330 W/(m*K), 340 W/(m*K), 350 W/(m*K), 360 W/(m*K), 370 W/(m*K), 380 W/(m*K), 390 W/(m*K), 400 W/(m*K), 410 W/(m*K), 420 W/(m*K) or more (measured at 0 °C). Said carrier can be heated via a heating device such that heat is transferred by conduction from the carrier to the desiccant. The heat transfer is therefore much faster than in conventional heating modes (radiation or convection) because the carrier has a much higher thermal conductivity λ and is in direct contact with the desiccant. Therefore the carrier and the desiccant can be heated up more quickly so that fluid, e. g. water, which has been picked-up or adsorbed/absorbed (chemisorption) by the desiccant, can be rapidly desorbed and can exit the carrier through the openings, resulting in a fast and energy efficient regeneration of the desiccant.

In an advantageous embodiment of the invention it is provided that the carrier comprises one or more of a group consisting of two or more mesh layers, between which at least part of the desiccant is arranged, a foam, in which at least part of the desiccant is arranged, a storage area having a coarse surface structure, on which at least part of the desiccant is arranged, and a desiccant containing chamber defined by the carrier, in which the desiccant is arranged. Thus, the household appliance component can be easily adapted to different intended applications and household appliances.

In a further advantageous embodiment of the invention it is provided that the household appliance component further comprises a fan device for passing a gas through the openings of the carrier to remove at least part of the freed fluid from the desiccant. The use of a fan device accelerates the regeneration of the desiccant since desorbed fluid can be transported by the gas away from the desiccant and cannot be readsorbed/reabsorbed by the desiccant. The fan device can also be used to essentially remove the entire picked-up fluid volume from the desiccant to achieve a complete regeneration.

In a further advantageous embodiment of the invention it is provided that the carrier consists of a metal, in particular aluminum and/or copper, or a metal alloy, in particular steel and/or an aluminum alloy. Metals and/or metal alloys such as for example steel or aluminum are inexpensive and have good thermal conductivity values λ of at least 15 W/(m*K). Further, metals and metal alloys can easily be heated by applying an electrical current, i.e. by using the carrier as a heating resistor. This is an easy, fast and inexpensive method to heat the carrier and thus the desiccant. In a further advantageous embodiment of the invention it is provided that the heating device is configured to heat up the carrier to said predetermined temperature by one or more of induction heating, electrical heating, and radiant heating. The heating device is thus easily adaptable to various household appliances. In a further advantageous embodiment of the invention it is provided that the desiccant is chemically inert. This ensures a high stability and a long service life of the desiccant. The desiccant may for example be or comprise silica, silica gel, and/or one or more zeolites.

A third aspect of the invention relates to a household appliance, which is configured to perform a method according to the first aspect of the invention and/or which comprises at least one household appliance component according to the second aspect of the invention. The resulting features and their advantages can be gathered from the description of the first and the second aspect of the invention. In an advantageous embodiment of the invention it is provided that the household appliance is configured as a dishwasher, a dryer, a washing machine, a microwave oven, and/or a steam oven. All these embodiments are exposed to humidity and thus require a fast and energy efficient way to reactivate the desiccant that is used to lower the humidity.

In a further advantageous embodiment of the invention it is provided that the household appliance further comprises a control device, which is configured for generating control signals for driving the heating device. This allows for a particularly precise control of the reactivation of the desiccant.

In a further advantageous embodiment of the invention it is provided that the control device is configured to generate the control signals based on a loading condition of the desiccant with fluid. Thereby it is ensured that a reactivation cycle of the desiccant is only started if required due to the loading condition of the desiccant. Unnecessary waste of energy is thus reliably avoided.

Further features of the invention are apparent from the claims, the figures and the description of figures. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of figures and/or shown in the figures alone are usable not only in the respectively specified combination, but also in other combinations without departing from the scope of the invention. Thus, implementations are also to be considered as encompassed and disclosed by the invention, which are not explicitly shown in the figures and explained, but arise from and can be generated by separated feature combinations from the explained implementations. Implementations and feature combinations are also to be considered as disclosed, which thus do not have all of the features of an originally formulated independent claim. Moreover, implementations and feature combinations are to be considered as disclosed, in particular by the implementations set out above, which extend beyond or deviate from the feature combinations set out in the relations of the claims. The figures show in:

Fig. 1 a schematic sectional view of a carrier, which is configured as a metallic foam and in which a desiccant is arranged; Fig. 2 a schematic sectional view of the carrier, which is configured as a metallic mesh and on which the desiccant is arranged; and

Fig. 3 a perspective view of several carriers, which are configured as metallic tubular meshes.

Fig. 1 shows a schematic sectional view of a carrier 1 , which is configured as a metallic foam and in which a desiccant 2 is arranged. The desiccant 2 consists of particles which are distributed homogeneously within the carrier 1. The material of the carrier 1 may for example comprise or consist of steel or aluminum which are inexpensive metals with good thermal conductivity. The carrier 1 thus has high thermal conductivity λ of at least 15 W/(m*K) (measured at 0 °C) and a low specific heat capacity. The desiccant 2 may for example comprise or consist of zeolites. The carrier 1 is further connected to an electric heating device 3 which is configured to heat the carrier 1 up to a predetermined temperature such that at least part of a fluid, which has been picked up by the desiccant 2, is freed from the desiccant 2 by transferring heat energy from the carrier 1 to the desiccant 2. Therefore the carrier 1 can quickly be heated up so that the temperature of the desiccant 2 is increased, which results in the desorption of the picked-up fluid. The fluid may for example be water, a solvent or other kinds of fluids. The desorbed fluid can then exit the carrier 1 through the porous holes of the foam. The metallic foam of the carrier 1 in other words is heated by an electrical current comparable to a resistor. This is an easy, fast and inexpensive method to heat the metallic carrier 1. Heat is transferred from the carrier 1 to the desiccant 2 much faster than in conventional heating methods because the carrier 1 is in direct contact with the desiccant 2. Heat is thus transferred by conduction (faster) instead of radiation or convection (slower) which leads to a fast and efficient regeneration of the desiccant 2. This principle can be used for example in household appliances, in particular in household appliances that use water.

Fig. 2 shows a schematic sectional view of another embodiment of the carrier 1 , which is configured as a metallic mesh and on which the desiccant 2 is arranged. The carrier 1 may comprise two or more mesh layers in order to enclose the desiccant particles 2. The carrier 1 is again in operative connection with an electrical heating device 3. Fig. 3 shows a perspective view of several carriers 1 , which are configured as metallic tubular meshes of different sizes. Each carrier 1 thus defines a desiccant containing chamber 4. The desiccant 2 (e. g. zeolites) may thus be easily arranged within the desiccant containing chamber 4 of each metallic tubular mesh and restored if needed. The carrier 1 can further be easily feeded with an air or gas stream. With this configuration, the air/gas can be in contact with a huge percentage of the surface of the desiccant 2 and remove desorbed fluid from the desiccant 2.

Apart from these three-dimensional mesh or foam structures it is generally also possible to configure the carrier 1 as a horizontal plate with a (slightly) coarse surface on which the desiccant particles 2 are distributed homogeneously in order to increase the contact surface with the heatable structure of the carrier 1.

The advantages of all embodiments of the present invention comprise the following points:

the heat transfer between the heat source (heating device 3) and the desiccant 2 is much faster compared to e. g. radiation heating methods because of the heat conductive carrier 1. Therefore, the heat transfer is carried out by conduction and not by convection or radiation;

the principle of the present invention is easily adaptable to different heating methods and heating devices 3 (radiation/convection, induction heating, conduction/electrical heating);

the principle of the present invention is particularly energy-efficient, because heat energy is directly transferred to the desiccant 2 and less residual waste is generated; and

by using porous carrier 1 such as foams and/or carrier with many openings such as (tubular) meshes, air or other gases can be in contact with a huge percentage of the surface of the desiccant 2 (zeolites), thereby improving the adsorption and regeneration processes. It will be understood by those skilled in the art that while the present invention has been disclosed above with reference to preferred embodiments, various modifications, changes and additions can be made to the foregoing invention, without departing from the spirit and scope thereof. The parameter values used in the claims and the description for defining process and measurement conditions for the characterization of specific properties of the invention are also encompassed within the scope of deviations, for example due to measurement errors, system errors, weighing errors, DIN tolerances and the like.

LIST OF REFERENCES carrier

desiccant

heating device

desiccant containing chamber