Device for dehumidifying air

Abstract

Device for dehumidifying air, with at least one body (10; 10a) having pores (12), wherein the pores (12) are designed to absorb the moisture present in the air in an inlet region (16; 16a) into the pores (12) by capillary action with condensation and to release it again from the pores (12) to the environment by evaporation in an outlet region (22; 22a) of the pores (12), characterized in that the cross-sectional area of ​​the pores (12) in the inlet region (16; 16a) is smaller than in the outlet region (22; 22a) of the pores (12) and / or that the angle (θ) of the pores (12) in the inlet region (16; 16a) is different from the angle (θ) of the pores (12) in the outlet region (22; 22a).

Description

State of the art

[0001] The invention relates to a device for dehumidifying air with the features of the independent device claim.

[0002] The energy required for air conditioning in a building, for example, is made up of the energy required to cool the air and the energy required to remove the moisture from the cooled air. The latter share of the total energy can amount to around 30% to 50% of the total energy depending on the climatic region or ambient conditions. Thermally driven devices in which the moisture is absorbed by liquids or solids can be used to dehumidify the cooled air. Silica gel or zeolite, for example, have proven to be effective solids. These are porous materials or bodies through which the air to be dehumidified flows. The moisture absorbed by the pores of the body must then be carried away again or removed from the pores by evaporation in order to maintain the functionality and effectiveness of the system.To ensure the body's regeneration, it is necessary to supply thermal energy, for example, through heating.

[0003] A method and a device for dehumidifying air using such a solid body is known from DE 11 2013 006 529 B4, wherein the device referred to there as a moisture absorption unit is designed as a porous sheet whose surface is, for example, coated or surface-treated, for example with the mentioned silica gel or zeolite. Disclosure of the invention

[0004] The method and the device according to the invention for dehumidifying air with the features of the independent claim have the advantage that the energy required to dehumidify the air is reduced compared to the above-mentioned prior art.

[0005] The invention is based on the idea that the Gibbs-Thomson effect, also known as the curvature effect, can be used both for dehumidification of the room air, i.e., for the absorption of moisture into the body's pores, and for the regeneration of the active material, i.e., for the expulsion of moisture from the pores. A curvature at the water-air interface, e.g., in a capillary membrane, leads to a change in the saturation vapor pressure across the curved surface. With a concave curvature, the saturation pressure is lowered, thus promoting condensation. With a convex curvature, on the other hand, the saturation vapor pressure is increased across the entire surface, thus promoting evaporation.

[0006] In other words, to minimize the energy required, it is advantageous if a porous body used to absorb and separate liquid through condensation and evaporation has a concave interface between the moisture and the air at the point where the moisture enters the pores, and a convex interface at the point where the moisture exits the pores. Depending on the material or geometry of the pores, this results in a steady flow of condensation on one side of the body and evaporation on the opposite side. This passively regenerates the material of the body for dehumidification, thereby reducing energy consumption in the desired manner.

[0007] Therefore, the method for dehumidifying air proposes that a first interface between the moisture and the air with a concave shape is created at the entry area of ​​the moisture into the pores of the body and a second interface between the moisture and the air with a convex shape is created at the exit area of ​​the moisture from the pores of the body.

[0008] To achieve a concave or convex shape of the interface between the moisture and the air in the area of ​​the body's pores, the shape of the interfaces is created by dimensioning the pore size at the inlet and outlet areas and / or by creating an angle between the interface and the pore. Both the pore size and the angle between the interface and the pore depend on the relative humidity and the material used for the body.

[0009] To optimize the pore effect, the air is designed to flow through the body in a main flow direction. In other words, this means that the body typically has two opposing end faces, with the air flow being directed onto the body in such a way that it typically enters perpendicularly onto the end face of the body and also exits at least substantially perpendicularly from the opposite end face of the body, while no pores are provided for flow through in a transverse extension of the body, or these are covered or closed.

[0010] To accelerate the evaporation of moisture in the exit area of ​​the body, or to enable it in the first place, the body can be heated in the exit area. This can be achieved, for example, by a heating element arranged in at least indirect contact with the body. Alternatively, the air exiting the exit side of the body can also be heated.

[0011] In a device according to the invention for dehumidifying the air, it is provided that the cross-sectional area of ​​the pores in the inlet region of the body is smaller than in the outlet region of the pores and / or that the opening angle of the pores in the inlet region is different from the opening angle of the pores in the outlet region of the body.

[0012] Advantageous further developments of the device according to the invention are listed in the subclaims.

[0013] Specifically, to achieve the mechanism according to the invention, it is preferably provided that the pores are substantially circular at least in the inlet region and in the outlet region, and that the diameter of the pores in the inlet region is less than 10 nm and in the outlet region at least 20 nm.

[0014] A further structurally preferred embodiment for forming the device according to the invention provides that the number of pores in the inlet region is greater than the number of pores in the outlet region, and that at least two pores in the inlet region are connected to a common pore in the outlet region, wherein in a section of the body between the inlet region and the outlet region the inlet-side and the outlet-side pores are connected to at least one common intermediate space.

[0015] Such a body suitable for dehumidification is preferably plate-shaped, with the pores of the inlet area opening at a first end face and the pores of the outlet area opening at the opposite, second end face of the body. This allows for a large area of ​​the body to be permeated by air, while the flow or throughflow resistance of the body is relatively low and the body is also relatively compact in the direction of the air flow.

[0016] It is particularly preferred if such a body is designed in the form of a membrane fiber plate. Such a membrane fiber plate can be used to produce pore diameters in the nanometer range mentioned above.

[0017] A further preferred design for optimizing the dehumidification effect provides that several plate-shaped bodies arranged at a distance from one another form a dehumidification arrangement, wherein the spaces between the bodies can be ventilated.

[0018] In the latter arrangement, it is furthermore preferably provided that, in the case of at least two adjacently arranged bodies, the inlet regions or the outlet regions are arranged directly opposite one another. Furthermore, the dehumidification effect can be optimized while reducing the space required for the arrangement if the distance between the bodies is smaller than their respective thicknesses.

[0019] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings.

[0020] This shows in: Fig. 1 a diagram explaining the relationship between relative humidity and a required capillary or pore diameter using silica gel for a dehumidifying body, Fig. 2 a schematic representation of a section of a device for dehumidifying the air and Fig. 3 an arrangement of three plate-shaped bodies arranged one behind the other and interacting with each other for dehumidifying air.

[0021] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0022] The physical process of absorption in capillaries is well known. For applications such as dehumidification of indoor air, the required capillary diameter can be calculated using a model. The Kelvin equation applies. In(pGp0)=2σr0⋅MWρWRT where p Gthe saturation vapor pressure above the curved liquid surface in the capillary, p0 is the saturation vapor pressure above a flat liquid surface, σ as surface tension of water and function of temperature, r0 is the radius of curvature of the liquid surface in the capillary, M w the molar mass of water, ρ w the density of water, R is the gas constant and T of the absolute temperature in Kelvin corresponds.

[0023] Since the saturation vapor pressure is proportional to the relative humidity (RH), pG / p0=rH

[0024] This allows the above equation to be solved for the radius of curvature r0. The contact angle θ between water and the capillary wall gives the relationship between the inner radius of the capillary r Kand the radius of curvature r0 under the approximation that the water surface in the capillary represents a circular segment of r K = r0 cos θ. This gives the capillary radius r K as a function of relative humidity rK=2σ⋅MWρWRT1In rF⋅cosΘ.

[0025] For a θ of 45°, the Fig. 1 for silica gel. To achieve a relative humidity rH of less than 50%, an inner diameter r K of 1nm or smaller is required.

[0026] In the Fig. 2 is a highly simplified and fragmentary representation of a body 10 acting as a membrane or device for dehumidification, which comprises a plurality of Fig. 2 has pores 12 shown in a highly simplified manner. The body 10 is designed in particular in the form of a membrane fiber plate 14 and has an inlet region 16 on a first end face 18 of the body 10, and an outlet region 22 on the opposite second end face 20.

[0027] Humid air enters the pores 12 of the body 10 via the inlet area 16 according to the flow arrows 24 through condensation in conjunction with the capillary action of the pores 12 and is evaporated from the pores 12 of the body 10 in the outlet area 22. Furthermore, it is assumed for simplicity that the cross section of the pores 12 is circular in the flow direction, which runs perpendicular to the two end faces 18, 20.

[0028] In particular, the Fig. 2, that a first interface 26 in the inlet region 16 of the pores 12, in which the water or moisture enters the pores 12 by capillary action, has a convex shape, while in the region in which the moisture is released from the pores 12 to the ambient air or the environment of the body 10, a second interface 28 is formed between the air and the moisture, which has a concave shape.

[0029] As shown by the Fig. As can also be seen in Figure 2, it is intended that the diameter d or the radius r of the pores 12 increase in the flow direction, i.e., from the inlet region 16 toward the outlet region 22 of the pores 12. In other words, this means that an asymmetric pore geometry is realized. Alternatively, it is also conceivable to achieve the corresponding interfaces 26, 28 by changing the contact angle between the pores 12 and the moisture through a surface treatment of the porous material of the body 10.

[0030] Without such a surface treatment, pore radii of less than 5 nm are typically required in the inlet region 16, while on the evaporation side or the outlet region 22, pore radii many times larger, ie at least 10 nm, are required.

[0031] In the Fig.3 shows a section of an arrangement 100 which essentially has three plate-shaped bodies 10a arranged parallel to one another and each at a distance a from one another. The respective distance a between the bodies 10a is in each case less than the thickness D of the respective body 10a. Furthermore, it can be seen that the number of pores 12 in the inlet region 16a is in each case less than the number of pores 12 in the outlet region 22a of the body 10a. This is achieved in that the pores 12 are connected to a section of the body 10a which is located between the two end faces 18a, 20a, via an intermediate space 30. In the case of the middle body 10a, the angle Θ between the pore 12 and the first interface 26a of the moisture as well as the cone angle ψ of the pore 12 to the vertical are also shown at each pore 12.

[0032] Furthermore, it can be seen that in the arrangement 100, the respective inlet regions 16a and outlet regions 22a of two adjacent bodies 10a are arranged directly opposite one another. The spaces 32 between the individual bodies 10a are ventilated or can be flowed through transversely in the direction of arrows 34, for example, to remove the (moist) air located there that has escaped from the respective body 10a.

[0033] The invention described so far can be modified or altered in many different ways without deviating from the inventive concept. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 11 2013 006 529 B4

[0003]

Claims

[1] Device for dehumidifying air, with at least one body (10; 10a) having pores (12), wherein the pores (12) are designed to absorb the moisture in the air in an inlet region (16; 16a) into the pores (12) by capillary action under condensation and to release it again by evaporation in an outlet region (22; 22a) of the pores (12) from the pores (12) to the environment by evaporation, characterized by that the cross-sectional area of ​​the pores (12) in the inlet region (16; 16a) is smaller than in the outlet region (22; 22a) of the pores (12) and / or that the angle (θ) of the pores (12) in the inlet region (16; 16a) is different from the angle (θ) of the pores (12) in the outlet region (22; 22a). [2] Device according to claim 1, characterized bythat the cross-section of the pores (12) is substantially circular at least in the inlet region (16; 16a) and in the outlet region (22; 22a), and that the diameter (d) of the pores (12) in the inlet region (16; 16a) is less than 10 nm and in the outlet region (22; 22a) is at least 20 nm. [3] Device according to claim 1 or 2, characterized by that the number of pores (12) in the inlet region (16; 16a) is greater than the number of pores (12) in the outlet region (22; 22a), and that at least two pores (12) in the inlet region (16; 16a) are connected to a common pore (12) in the outlet region, wherein in a section of the body (10; 10a) between the inlet region (16; 16a) and the outlet region (22; 22a) the pores (12) are connected to at least one intermediate space (30). [4] Device according to one of claims 1 to 3, characterized bythat the body (10; 10a) is plate-shaped, wherein the pores (12) of the inlet region (16; 16a) open at a first end face (18; 18a) and the pores (12) of the outlet region (22; 22a) open at the second end face (20; 20a) of the body (10; 10a) opposite the first end face (18; 18a). [5] Device according to one of claims 1 to 4, characterized by that the body (10; 10a) is designed in the form of a membrane fiber plate (14). [6] Device according to one of claims 1 to 5, characterized by that several bodies (10a) arranged at a distance (a) from one another form an arrangement (100), and that the spaces (32) between the bodies (10a) can be ventilated. [7] Device according to claim 6, characterized by that in at least two adjacently arranged bodies (10a) the respective inlet regions (16a) or outlet regions (22a) are arranged directly opposite one another. [8] Device according to claim 6 or 7, characterized by that the distance (a) between the bodies (10a) is less than their respective thickness (D).

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