Technical field

[0001 ] The present invention relates generally to a method and an apparatus for dehumidification of air and more specifically to a method and an apparatus which can be switched between different operating modes.

Background art

[0001 ] The international patent publication No. W09006165 A1 describes a method and an apparatus for dehumidification of air wherein process air is dehumidified through passing a drying rotor comprising moisture adsorbing means. In order to reach high temperatures radiation heat is used from a heating element, for example a radiator, for regeneration of an adsorption means comprised in a rotor.

[0002] One problem with this kind of solution is that the wet regeneration air flow must be led away from the space being dried. This can normally be achieved by passing the wet air-flow to a room or to the surroundings, for example with the aid of a hose. There are cases, however, when this known technique can only be applied with difficulty and at relatively high costs, for instance where there are no vents or windows or when these windows cannot be opened. Other examples are when cellar air or the air in a bank vault shall be dehumidified and dried. There may also be other reasons, such as a risk for spreading contaminations or mould.

[0003] This problem is normally solved by connecting a condenser/heat- exchanger to a dehumidifier or to integrate a heat-exchanger in a dehumidifier. In principle, a condenser is a heat-exchanger in which wet air is brought into heat- exchange contact with cold air, therewith extracting and collecting the moisture in the wet air while heating the cold air delivered to the heat exchanger. In the international patent publication No. WO9304764 A1 this is solved by delivering wet regenerating air exiting from the dehumidifier to one side of a condenser or heat- exchanger so as to deliver energy to the process air delivered to the other side of said condenser or heat-exchanger for cooling purposes; collecting and/or carrying away condensation obtained from the regenerating air; and delivering the process air heated in the preceding step to the dehumidifier so as to extract moisture from the process air and further dry said process air. This solves the problem of leading away the wet regeneration air flow. However, it is not always known in advance which solution is the best to apply to a specific task. This can lead to extra transportation costs which in turn has a negative effect on the environment.

Summary of invention

[0004] An object of the present invention is to avoid the problem of having to choose the kind of dehumidifier in advance and to provide a versatile dehumidifier which can be switched between different operating modes.

[0005] According to a first aspect of the invention, a dehumidifier is provided comprising a housing provided with a process air inlet and a process air outlet; a drying device provided with moisture adsorption means; a fan adapted to bring process air entering through the process air inlet to pass the drying device and, subsequent to having been dehumidified, depart through the process air outlet; means for heating regeneration air, wherein the regeneration air, during operation, passes through the drying device for regeneration of the moisture adsorption means; a regeneration air outlet, and a heat-exchanger with a first inlet and a second inlet for effecting an exchange of heat between air entering through the first inlet and air entering through the second inlet; which is characterized by a valve switchable between a first position, wherein the drying device and the regeneration air outlet are in fluid connection, allowing wet regeneration air to exit through the regeneration air outlet; and a second position, wherein the drying device and the second inlet of the heat-exchanger are in fluid connection, allowing an exchange of heat between wet regeneration air having passed through the drying device and air entered through the first inlet of the heat exchanger, wherein the wet regeneration air will be cooled and water vapour of the wet regeneration air will condense. A versatile dehumidifier which can be switched between different operating modes is thereby provided. [0006] In a preferred embodiment, the drying device comprises a rotor. This provides for a compact device wherein the moisture adsorption means in sectors of the rotor are alternately used for drying process air and being regenerated, depending on the position of the rotor.

[0007] In a preferred embodiment, a distribution chamber is provided in fluid connection with the second inlet of the heat-exchanger, wherein, with the valve in the second position, wet regenerating air exiting from the valve is delivered to the distribution chamber.

[0008] In a preferred embodiment, a condensation trough is provided below the heat exchanger, in which water condensed from the wet regeneration air will collect. A condensation water pump may optionally be connected to the

condensation trough for removing condensation water from the trough.

[0009] In a preferred embodiment, the valve comprises has an inlet end in fluid connection with the rotor and an outlet end opposite the inlet end and in fluid connection with the regeneration air outlet, wherein the valve is essentially tubular and comprises an inner tube and an outer tube, wherein the inner tube exhibits an end wall opposite the inlet end, and wherein the inner and outer tubes are coaxial and the inner tube is rotatably journaled within the outer tube. This design provides a compact valve which is easy to switch between different positions.

[0010] In a preferred embodiment, the inner tube is provided with an opening in its envelope surface for the function of releasing regeneration air in one of two directions, depending on the rotational position of the inner tube: in the first position of the valve to the regeneration air outlet and in the second position of the valve to the second inlet of the heat-exchanger.

[0011 ] In a preferred embodiment, the outer tube is provided with a first opening in fluid connection with the second inlet of the heat-exchanger and a second opening in fluid connection with the regeneration air outlet.

[0012] In a preferred embodiment, a bypass chamber is provided, wherein the outer tube is provided with a third opening, wherein the second and third openings of the outer tube are in fluid connection with the bypass chamber and wherein the third opening is in fluid connection with the regeneration air outlet.

[0013] In a preferred embodiment, the first inlet of the heat-exchanger is connected to the process air inlet. Thereby, the process air can be used for cooling the wet regeneration air.

[0014] According to a second aspect of the invention, a method of drying air is provided comprising the following steps: bringing process air to pass a drying device provided with moisture adsorption means; and, after having been dehumidified, depart through a process air outlet; heating regeneration air and bringing the heated regeneration air to pass through the drying device (6) for regeneration of the moisture adsorption means; wherein the method is

characterized by the step of: in a first operation mode, bringing the drying device (6) and a regeneration air outlet into fluid connection, allowing wet regeneration air to exit through a regeneration air outlet; and in a second operation mode, bringing the drying device and a second inlet of a heat-exchanger into fluid connection, allowing an exchange of heat between wet regeneration air having passed through the drying device (6) and air having entered a first inlet of the heat-exchanger with subsequent cooling of the wet regeneration air and condensation of water vapour of the wet regeneration air.

[0015] In a preferred embodiment, the process air is brought to enter the first inlet of the heat-exchanger. Thereby, the process air can be used for cooling the wet regeneration air.

Brief description of drawings

[0016] The invention is now described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic overall sectional view of a dehumidifier according to the invention; Figs 2a and 2b show perspective views of a valve comprised in the dehumidifier of Fig. 1 ;

Fig. 3a is a perspective view of the dehumidifier of Fig. 1 with removed cover plate, showing the interior of the dehumidifier, in a first mode of operation;

Fig. 3b is a cross-sectional view of a heat-exchanger comprised in the apparatus of Fig. 3a;

Fig. 3c is a sectional view through the valve comprised in the dehumidifier of Fig. 3a in the first mode of operation;

Fig. 4a is a perspective view of the dehumidifier of Fig. 1 with removed cover plate, showing the interior of the dehumidifier, in a second mode of operation;

Fig. 4b is a cross-sectional view of a heat-exchanger comprised in the apparatus of Fig. 4a; and

Fig. 4c is a sectional view through the valve comprised in the dehumidifier of Fig. 4a in the second mode of operation.

Description of embodiments

[0017] In the following, a detailed description of a method and apparatus for dehumidification according to the invention will be given. It will be realized that when reference is made to directions, such as“up” or“down”, these are to be interpreted as during normal operation of the apparatus. Also, when the term“in fluid connection” is used, it is to be interpreted as including the ability to conduct air from one point to another.

[0018] With reference to Fig. 1 a dehumidifier comprises a housing 2 provided with an inlet 3 for process air and an outlet 4 for dry process air. A handle 2a on the housing 2 is provided for facilitate carrying of the dehumidifier 1. A partition wall 5 is provided in the housing 2 exhibiting a hole housing a drying device in the form of a rotor 6, the journaling of which is not shown in the figures. The rotor is driven by an electrical motor (not shown), directly or indirectly via a belt, for example. The rotor is provided with a suitable sealing (not shown) sealing the rotor against the partition wall 5.

[0019] The rotor 6 exhibits a large number of passages, in which an adsorption means in the form of a desiccant, for example silica gel, a molecular sieve or the like is provided, whereby an almost infinite regeneration of the rotor is possible.

[0020] There is provided a fan 10, such as a centrifugal fan, adapted to draw damp air, in the following referred to as process air, into the inlet 3. The speed of the fan can be controlled by means of a controller a potentiometer or the like between a lowest speed and a highest speed, whereby the amount of drawn process air can be controlled in dependence of a desired operating mode. This controller may generate a step-less external control signal varying between 0-10 VDC or operate according to a PWM control scheme. The speed control may also be effected through a potentiometer or the like. As an alternative to step-less control, the speed of the fan can be controlled between the lowest and the highest speeds or between several speeds by means of a switch, for example.

[0021 ] The fan creates an overpressure in the part 2a of the housing which is provided adjacent to the partition wall 5. The process air which has been drawn in and been pressurized by the fan 10 flows through the rotor 6 and is dehumidified herein. The major part of this flow of process air flows into a chamber 2b provided on the other side of the partition wall 5 and leaves the dehumidifier through the outlet 4 for process air. This dried process air is returned to a space or room to be dried, for example to a water damage or to another process wherein air with a low moisture content is used.

[0022] A minor part of the air that flows through the rotor 6, for example one fifth of the incoming flow of process air, is captured by a first cover 12, preferably made of aluminium or other heat resistant material, which is mounted on the low pressure side of the rotor 6. The first cover 12 preferably has the shape of a circle sector except the portion corresponding to the rotor axle. A corresponding second cover 13 is provided on the high pressure side of the rotor 6. [0023] As previously mentioned a part, in one embodiment 20 %, of the process air flowing through the rotor is captured by the first cover and this deflected air, the regeneration air, is heated by a heating element, preferably in the form of a PTC heater, provided in the first cover 12. The heating element is thus adapted to heat air flowing by and which then flows though the rotor and heats this, whereby moisture captured by the desiccant is removed by the regeneration air and is bound thereto, whereafter the damp regeneration air leaving the rotor is captured by the second cover 13 and is guided by a tube 16 and to a valve 20, the function of which will be explained in detail below.

[0024] A temperature sensor (not shown) may optionally be provided in close proximity to and preferably downstream of the heating element for measuring of the temperature up to which the heating element heats the air flowing by. In addition to or alternatively a flow sensor may optionally be provided for measuring the air flow through the rotor. These parameters may be used for adjusting the operation of the dehumidifier.

[0025] An outlet 7 for bypass air is provided on the high-pressure side 2a from which process air can exit the dehumidifier 2 without having been dried. This outlet is optional and is used to create an underpressure in the dehumidifier. This is advantageous since the distribution of dust and other particles and also odour from the dehumidifier is decreased.

[0026] A condenser/heat-exchanger 8 is provided adjacent to the inlet 3 for process air and below the valve 20. This heat-exchanger 8 comprises lamellar between which heat-exchange is effected between wet regenerating air, which is delivered from the valve 20, and process air which is delivered to the

condenser/heat-exchanger from the inlet 3.

[0027] Thus, in a first operating mode, wet regenerating air exiting from the valve 20 is delivered to a condensation or distribution chamber 9 above, i.e. , in fluid connection with a top inlet of the heat-exchanger for the purpose of delivering energy to the process air, which is delivered to the front side, in Fig. 1 the left side, of the heat-exchanger 8. This is shown with a dashed arrow in Fig. 1. The process air is therewith used for cooling purposes and will be slightly heated as it takes up energy from the wet regenerating air, the water vapour of which will condense and be collected in a trough 8a below the heat-exchanger 8 from where it can be removed through a pipe (not shown), preferably by means of a condensation water pump 22. The slightly heated process air then enters the chamber 2a and then the rotor 6, in which the air is dehumidified.

[0028] In order to make the heat-exchanger more effective, a number of cells can be coupled sequentially so that the efficiency of the heat-exchanger will correspond to a contraflow heat-exchanger, despite each cell operating in crossflow. The efficiency is greatly improved even when only two cells are coupled.

[0029] In a second operating mode, the regeneration air is conducted to a regeneration air outlet 21 , shown by the dash-dotted arrow in Fig. 1 , to be further conducted to the outside of the space to be dehumidified by means of a hose or the like (not shown).

[0030] The valve 20 will now be explained in detail with reference to Figs. 2a and 2b, showing different perspective view of the valve. The valve 20 has an inlet end 20a facing the rotor 6, i.e. , in fluid connection with the regeneration portion of the rotor, and an outlet end 20b opposite the inlet end, which is in fluid connection with the regeneration air outlet 21. In this embodiment, the valve 20 is essentially tubular and comprises an inner tube 22 and an outer tube 24. The inner and outer tubes 22, 24 are coaxial and the inner tube 22 is rotatably journaled within the outer tube 24. The inner tube 22 is shorter than the outer tube 24, preferably about half the length, and is provided with an open end facing the rotor 5 and an end wall 22a opposite the open end which is situated in the mid portion of the outer tube 24, see also the sectional views in Figs. 3c and 4c.

[0031 ] The inner tube 22 is provided with an opening 22b in its envelope surface for the function of releasing regeneration air in one of two directions, depending on the operating mode, i.e., depending on the rotational position of the inner tube 22. This switching of mode is effected by rotating the inner tube 22 to align the opening 22b with either a first opening 24a or a second opening 24b in the outer tube. The outer tube is also provided with a third opening 24c in the portion not overlapping the inner tube 22. The rotation or turning of the inner tube 22 is facilitated by means of manually turning a handle 22c attached to the inner tube 22, although any means for turning the inner tube, such as an electric motor, may be provided.

[0032] The switching between the two operating modes will now be described with reference to Figs. 3a-c, showing a first operating mode wherein the

regeneration air is conducted to and through the heat-exchanger 8, and to Figs. 4a-c, showing a second operating mode wherein the regeneration air is conducted out of the dehumidifier 1 through the regeneration air outlet 21.

[0033] In Figs. 3a-c there is shown a rotational position of the inner tube 22, wherein the opening 22b in the inner tube 22 is aligned with the first opening 24a in the outer tube 24. The outer tube 24 is mounted so that this first opening 24a is in fluid connection with the distribution chamber 9 above the heat-exchanger 8, see the cross-sectional view in Fig. 3b. This means that wet regeneration air entering the valve 20 through the first end thereof will be conducted to the heat- exchanger 8, there participating in heat-exchanging with process air. The end wall 22a of the inner tube 22 will prevent the regeneration air from reaching the other end of the valve 20 and thereby keep the regeneration air within the dehumidifier.

[0034] In Fig. 3b it is schematically shown with an arrow how the wet

regeneration air leaves the condensation or distribution chamber 9. Thus, one function of this chamber is to ensure that the wet regeneration air is distributed between the multiple channels of the heat exchanger 9. The wet regeneration air passes a first portion of the heat exchanger 8, then a volume below the heat exchanger where condensed water is collected and returns via a second portion of the heat exchanger to another space above the heat exchanger to mix with the process air. In the figure, the division between the first and second portions of the heat exchanger 8 is shown with a dashed line. The condensation mainly takes place in channels of the heat exchanger, although some condensation can occur also in the distribution chamber 9.

[0035] In Figs. 4a-c there is shown a rotational position of the inner tube 22, wherein the opening 22b in the inner tube 22 is aligned with the second opening 24b in the outer tube 24. The outer tube 24 is mounted to that this second opening 24b and also the third opening 24c are in fluid connection with a bypass chamber 26, see Fig. 4b, which is sealed from the rest of the interior of the dehumidifier 1. This means that wet regeneration air entering the valve 20 through the first end thereof will be conducted out of the opening 22b of the inner tube 22 and the second opening 24b of the outer tube 24, which is aligned therewith, and into the bypass chamber 26. From there, the regeneration air enters the third opening 24c in the outer tube 24 and onward to the second end of the valve, from which it exits the dehumidifier 1 through the regeneration air outlet 21.

[0036] In summary, when air is dried according to the invention, process air is brought to pass a drying device 6 provided with moisture adsorption means; and, after having been dehumidified, depart through a process air outlet 4.

Regeneration air is heated and then brought to pass through the drying device 6 for regeneration of the moisture adsorption means. In a first operation mode, the drying device 6 and a regeneration air outlet 21 are brought into fluid connection, allowing wet regeneration air to exit through a regeneration air outlet. In a second operation mode, the drying device and a second inlet of a heat-exchanger 8 are brought into fluid connection, allowing an exchange of heat between wet regeneration air having passed through the drying device 6 and process air having entered a first inlet of the heat-exchanger 8.

[0037] A preferred embodiment of a dehumidifier according to the invention has been described. It will be appreciated that this may be varied within the scope of the appended claims without departing from the inventive idea. Thus, although a drying device in the form of a driven rotor has been described, this could also be a static device which is intermittently dried. [0038] An embodiment with a single fan creating an overpressure in one part of the housing for effecting a flow of the process and regeneration air has been shown. It will be appreciated that other fan arrangements may be provided, as long as the desired air flows are obtained. For example, a separate fan for the regeneration air may be provided. The inventive idea also covers an embodiment with a separate circuit for regeneration air, i.e. , instead of using part of the dried process air as regeneration air, a separate regeneration air intake is provided.

[0039] In the described embodiment, process air entering the process air inlet is used in the heat-exchanger for cooling the wet regeneration air. It will be realized that the wet regeneration air can be cooled by a separate air stream. In other words, a separate air path for air entering the first inlet of the heat-exchanger may be provided while the process air to be dried is brought to the drying device without passing the heat-exchanger.

[0040] A specific design of the valve has been described. It will be realized that any kind of two-way valve having the ability to forward incoming air to one of two different destinations can be used, such as a flap valve.