Desiccant dehumidifier and method for controlling desiccant dehumidifier carried out by control device

Abstract

The present disclosure relates to a method performed by a control device (200) for controlling a desiccant dehumidifier (1), the method comprising the steps of: controlling (s101) a heater device (28) arranged in fluid communication with a regeneration air circuit (12) upstream of a desiccant wheel (2) to provide a substantially constant temperature of regeneration air (14); and controlling (s102) a volumetric flow of regeneration air (14) having a substantially constant temperature through a regeneration sector (16) of the desiccant wheel (2) based on a predetermined target humidity in the regeneration sector (16). The present disclosure also relates to a computer program, a computer readable medium (202) having a computer program stored thereon, and a desiccant dehumidifier (1).

Description

Technical Field

[0001] The present invention relates to a method, a computer program, a computer-readable medium and a desiccant dehumidifier. More specifically, the present disclosure relates to a method for controlling a desiccant dehumidifier performed by a control device. The present invention also relates to a computer program, a computer-readable medium having the computer program stored thereon and a desiccant dehumidifier comprising: a desiccant wheel arranged in a rotatable manner about a central axis of the desiccant wheel; a process air circuit arranged to guide process air through a process sector of the desiccant wheel; a regeneration air circuit arranged to guide regeneration air through a regeneration sector of the desiccant wheel; a fan arranged in the regeneration air circuit downstream of the desiccant wheel, the fan being configured to generate a flow of regeneration air in the regeneration air circuit; and a heater device arranged to be in fluid communication with the regeneration air circuit upstream of the desiccant wheel. Background Art

[0002] Dehumidifiers, such as adsorption dehumidifiers and condensation dehumidifiers, are used to separate and remove moisture from the air. Adsorption dehumidifiers typically include a dehumidifying element in the form of a wheel or rotor that holds a desiccant material that effectively attracts and retains water vapor. The desiccant rotor can be divided into two sectors: a process sector and a regeneration sector. The airflow to be dehumidified, i.e., the process air, passes through the process sector of the desiccant rotor, and the desiccant material in the rotor extracts moisture from the process air so that the process air can leave the rotor as dry air. At the same time, the desiccant material is regenerated by another air flow, i.e., the regeneration air flow, flowing through the regeneration sector, and the desiccant rotor can always rotate slowly around the longitudinal axis of the desiccant rotor. By simultaneously dehumidifying the process air and regenerating the desiccant material, the dehumidifier can operate continuously.

[0003] US2007056307 discloses an example of a dehumidifier having a desiccant wheel.

[0004] The air flowing through the regeneration sector is heated by a heater assembly. The heat in the heater assembly can be generated electrically. The airflow through the regeneration sector can be generated by an electrically powered fan. The heated air flowing through the regeneration sector releases moisture from the desiccant wheel, thereby drying the wheel. Summary of the Invention

[0005] Releasing moisture from the desiccant wheel via the regeneration air reduces the humidity in the wheel, allowing the desiccant wheel to extract moisture from the process air passing through the process sector. However, heating the regeneration air for drying the desiccant wheel is energy-intensive and expensive. Desiccant dehumidifiers are known that use unlimited power to quickly reach a steady state, but with little concern for energy usage.

[0006] Furthermore, there are known heater devices for heating the regeneration air that may not achieve a uniform temperature distribution of the regeneration air in the desiccant wheel. Consequently, it may be difficult to control the desiccant dehumidifier, which may result in an unnecessary dry desiccant wheel due to overheating of the desiccant wheel.

[0007] In some cases, it may be beneficial to operate a desiccant dehumidifier in different operating modes, depending on the conditions and needs of the air in the space or room being treated. In some cases, low cost for drying the room is a priority. In other cases, the same desiccant dehumidifier must be used to reduce humidity in the same room within a short period of time. In still other cases, it may be important to avoid condensation on walls and surfaces in the room.

[0008] Therefore, there is a need for an improved desiccant dehumidifier and method for controlling a desiccant dehumidifier that, in one operating mode, reduces the energy requirements for treating the air in a space or room, in another operating mode, reduces the humidity in the same space or room for a short period of time, and in yet another operating mode, prevents condensation on walls and surfaces in the space or room.

[0009] It is an object of the present disclosure to mitigate, alleviate or eliminate one or more of the above-mentioned deficiencies and disadvantages in the prior art and to at least solve the above-mentioned problems.

[0010] Another object of the present invention is to achieve a desiccant dehumidifier and a method for controlling a desiccant dehumidifier which, in an operating mode, reduces the energy requirements for treating the air in a space or room and thus reduces the heating costs for the regeneration air.

[0011] Another object of the present invention is to achieve a desiccant dehumidifier and a method for controlling a desiccant dehumidifier which, in one operating mode, reduces the humidity in the same space or room within a short period of time.

[0012] Another object of the invention is to achieve a desiccant dehumidifier and a method for controlling a desiccant dehumidifier which, in an operating mode, prevents condensation on walls and surfaces in a space or room.

[0013] These objects are achieved by the method initially defined, the method further comprising the steps of: controlling the heater means to provide a substantially constant temperature of the regeneration air; and controlling the volumetric flow rate of the regeneration air having the substantially constant temperature through the regeneration sector of the desiccant wheel based on a predetermined target humidity in the regeneration sector.

[0014] Desiccant dehumidifiers are configured to process air so as to separate and remove moisture, such as water vapor, from the air. Dry air can be delivered from the desiccant dehumidifier to a space or room where the humidity in the air should be controlled. The desiccant wheel holds a desiccant material that effectively attracts and retains water vapor. The process airflow will flow in a process air circuit and pass through the desiccant wheel. The desiccant material in the main desiccant wheel extracts moisture from the process air in the process airflow so that the process air can leave the desiccant wheel as dry air. The moisture extracted from the process air is removed from the desiccant material in the desiccant wheel by a regeneration airflow that flows in the regeneration air circuit and flows through the desiccant wheel. The moisture removed from the desiccant material is delivered from the desiccant wheel to the downstream of the desiccant wheel by the regeneration airflow in the regeneration air circuit. A fan arranged downstream of the desiccant wheel is configured to generate a regeneration airflow in the regeneration air circuit.

[0015] The heater device is configured to increase the temperature of the regeneration air in the regeneration air circuit. The heater device can produce a constant or substantially constant temperature for the regeneration air. Furthermore, the heater device can produce a regeneration air temperature that is uniformly or substantially uniformly distributed throughout the regeneration sector. The substantially constant temperature of the regeneration air provided by the heater device can be selected based on a selected predetermined target humidity. Furthermore, the regeneration air flow is controlled using a regeneration air fan to achieve a target outlet moisture content. The heater device can have a flattening effect on the temperature distribution, thereby making the temperature distribution uniform. To optimize the unit's energy usage, it is beneficial not to overdry the desiccant wheel in the regeneration sector, as additional dehumidification capacity requires excessive thermal energy, which is expensive. To avoid overdrying, even when the regeneration air flow in the desiccant dehumidifier varies, the control device can limit the regeneration air flow to a precalculated value to ensure low energy usage. This results in a smoother and slower change in the regeneration air flow, which can save costs when achieving the target humidity is not time-critical. Thus, in the first operating mode, the heater device can be controlled to smoothly achieve the target humidity with low overall energy usage. Thus, the humidity in a space or room can be controlled using a variable regeneration airflow limited by a preset value to minimize the total energy use used to achieve the target room humidity. The method for controlling a desiccant dehumidifier in this first operating mode can reduce the energy demand for treating the air in the space or room and therefore reduce the heating costs of the regenerated air. In addition, the desiccant dehumidifier can be switched to a second operating mode for reducing the humidity in the same space or room over a short period of time. The heater device can be controlled to provide an increased and substantially constant temperature of the regeneration air and to control the volume flow of regeneration air with an increased and substantially constant temperature through the regeneration sector based on a lower predetermined target humidity in the desiccant wheel. This selection of the second operating mode can increase the energy demand for both the heater device and the fan arranged in the regeneration circuit, but achieve the target temperature within a short period of time.

[0016] The desiccant dehumidifier may further include a first humidity sensor disposed in a process air circuit downstream of the desiccant wheel, wherein the step of controlling the volumetric flow rate of regeneration air through the regeneration sector is further based on the current humidity in the desiccant wheel determined by means of the first humidity sensor. The first humidity sensor disposed in the process air circuit may be disposed near the desiccant wheel or at a limited distance from the desiccant wheel. The first humidity sensor is configured to transmit a signal to a control device regarding the humidity sensed in the process air circuit downstream of the wheel. In some operating modes of the desiccant dehumidifier, the humidity in the process air circuit downstream of the desiccant wheel may be in the range of 0% RH to 10% RH, preferably in the range of 0% RH to 5% RH, and most preferably in the range of 0% RH to 2% RH. The humidity in the process air circuit downstream of the desiccant wheel is indicative of the humidity in the regeneration sector of the desiccant wheel. In this manner, the humidity in the regeneration sector of the desiccant wheel can be controlled.

[0017] The desiccant dehumidifier may further include a second humidity sensor disposed in the regeneration air circuit downstream of the desiccant wheel, wherein the step of controlling the volumetric flow rate of the regeneration air through the regeneration sector is further based on the current humidity in the desiccant wheel determined by the second humidity sensor. The second humidity sensor disposed in the regeneration air circuit may be disposed near the desiccant wheel or at a limited distance from the desiccant wheel. The second humidity sensor is configured to transmit a signal to a control device regarding the humidity sensed in the regeneration air circuit downstream of the wheel. The humidity in the regeneration air circuit downstream of the desiccant wheel may indicate the humidity in the regeneration sector of the desiccant wheel. In certain operating modes of the desiccant dehumidifier, the humidity in the regeneration air circuit downstream of the desiccant wheel may be in the range of 50% RH to 100% RH, preferably in the range of 65% RH to 95% RH, and most preferably in the range of 70% RH to 90% RH. In this manner, the humidity in the regeneration sector of the desiccant wheel can be controlled. The second humidity sensor may be disposed in conjunction with the first humidity sensor in the desiccant dehumidifier. The value from the second humidity sensor can be evaluated in conjunction with the value from the first humidity sensor in the desiccant dehumidifier.

[0018] The desiccant dehumidifier may further include a third humidity sensor disposed in a space fluidly connected to the process air circuit, wherein the step of controlling the volumetric flow rate of regeneration air passing through the regeneration sector is further based on a target operating time of the desiccant dehumidifier for achieving a target humidity in the space determined by the third humidity sensor. The third humidity sensor may be disposed in the space to be dried by the desiccant dehumidifier. The third humidity sensor is configured to transmit a signal regarding the humidity sensed in the space to a control device. The desiccant dehumidifier may be controlled to reduce the humidity in the space to the target humidity based on the target operating time of the desiccant dehumidifier. The heater device may be controlled to provide a substantially constant temperature at a desired temperature level for the regeneration air. The volumetric flow rate of the regeneration air may be controlled at a desired level by controlling the fan. The desired temperature level and the desired volumetric flow rate of the regeneration air may be selected to achieve the target humidity in the space at the desired operating time of the desiccant dehumidifier. The third humidity sensor may be disposed in conjunction with the first humidity sensor and / or the second humidity sensor in the desiccant dehumidifier. The value from the third humidity sensor may be evaluated in conjunction with the value from the first humidity sensor and / or the second humidity sensor in the desiccant dehumidifier.

[0019] The desiccant dehumidifier may further include a dew point sensor disposed in a room fluidly connected to the process air circuit, wherein the step of controlling the volumetric flow rate of regeneration air passing through the regeneration sector is further based on a target dew point humidity determined by the dew point sensor. The dew point sensor may be disposed in the room to be dried by the desiccant dehumidifier. The dew point sensor is configured to send a signal regarding the dew point sensed in the room to a control device. In some cases, it may be important to avoid condensation of fluid on walls and surfaces in the room. Therefore, the volumetric flow rate of regeneration air passing through the regeneration sector may be controlled to achieve the target dew point humidity. The dew point sensor may be disposed in conjunction with the first humidity sensor, the second humidity sensor, and / or the third humidity sensor in the desiccant dehumidifier.

[0020] The step of controlling the volume flow of the regeneration air passing through the regeneration sector may include controlling the speed of a fan to control the volume flow of the regeneration air. The fan may be connected to a control device. The control device may control the speed of the fan to control the volume flow of the regeneration air passing through the regeneration sector.

[0021] The desiccant dehumidifier may further include a damper disposed in the regeneration air circuit downstream of the desiccant wheel, wherein the step of controlling the volumetric flow of regeneration air passing through the regeneration sector includes controlling the damper to control the volumetric flow of the regeneration air. The damper may be controlled between an open position and a closed position. In the fully open position, a large volumetric flow of regeneration air may pass through the regeneration sector. In positions between the open and closed positions, the volumetric flow of regeneration air passing through the regeneration sector may be restricted. The damper may be electrically or pneumatically controlled.

[0022] The desiccant dehumidifier may further include a purge air circuit arranged to direct purge air through a purge sector of the desiccant rotor, the purge air circuit being arranged in fluid communication with a process air circuit upstream of the desiccant rotor and with a regeneration air circuit upstream of the heater device, wherein the method includes the following further steps: controlling the volumetric flow rates of the purge air and the regeneration air through the desiccant rotor based on a predetermined target humidity in the desiccant rotor. In addition to the process airflow and the regeneration airflow, the purge airflow is also configured to pass through the desiccant rotor. The purge airflow is arranged to flow in the purge air circuit of the desiccant dehumidifier. When the regeneration airflow passes through the rotor, the temperature of the desiccant rotor will increase. In order to effectively capture moisture and water from the process airflow in the desiccant rotor, the goal is to reduce the temperature of the portion of the desiccant rotor where the regeneration airflow has passed through the desiccant rotor. Therefore, the purge airflow is directed through the purge sector. The purge airflow flowing through the purge sector can have a lower temperature than the regeneration airflow passing through the desiccant rotor. Therefore, the purge airflow flowing through the purge sector will reduce the temperature of the portion or sector of the desiccant wheel where the regeneration airflow has passed through it. Since the temperature of the desiccant wheel is increased by the regeneration airflow, the temperature of the air in the purge airflow will increase as it flows through the purge sector. The purge airflow with the increased temperature is directed to the regeneration air circuit upstream of the heater device. The heater device can produce a substantially constant and uniformly distributed regeneration air temperature, which can benefit energy recovery in the purge air sector. In addition, the regeneration airflow can be controlled by a fan in the regeneration circuit to achieve a target moisture outlet content, which also controls the purge airflow. This process has two energy-related benefits: the heater device can have a flattening effect on the temperature distribution, making it more uniform, and the mixed temperature of the purge outlet air and the heated regeneration air will be substantially constant / similar regardless of the air flow / volume because the heat transfer effect in the desiccant wheel will remain substantially constant.

[0023] The step of controlling the volume flow of the purge air and the regeneration air through the desiccant wheel may include controlling the speed of the fan to control the volume flow of the purge air and the regeneration air through the desiccant wheel. The volume flow of both the purge air and the regeneration air through the desiccant wheel can be controlled by the speed of the fan. The fan can be connected to a control device. Since the fan is arranged downstream of the desiccant wheel, a negative pressure can be generated in the regeneration air circuit and the purge air circuit by the fan. The volume flow of both the purge air and the regeneration air through the desiccant wheel can be controlled by a damper. In addition, the volume flow of both the purge air and the regeneration air through the desiccant wheel can be controlled by the damper together with the selected speed of the fan.

[0024] The step of controlling the volumetric flow rates of purge air and regeneration air through the desiccant wheel may include controlling the volumetric flow rate of purge air through the purge sector of the desiccant wheel relative to the volumetric flow rate of regeneration air through the regeneration sector of the desiccant wheel. The predetermined target humidity in the regeneration sector of the desiccant wheel can be used to change the ratio between the volumetric flow rate of purge air and the volumetric flow rate of regeneration air to achieve the predefined target. The operating mode of the desiccant dehumidifier can dry air at a low cost or dry air quickly. For example, in order to enable the desiccant dehumidifier to dry air quickly, when the ratio between the volumetric flow rate of purge air and the volumetric flow rate of regeneration air is reduced, the desiccant dehumidifier can achieve a higher drying capacity value (e.g., expressed in weight per unit time period). To change the ratio, the desiccant dehumidifier can be provided with an adjustable purge air inlet. Such an inlet can block the volumetric flow rate of purge air based on the volumetric flow rate of regeneration air. A high volumetric flow rate of regeneration air with a low ratio between the volumetric flow rate of purge air and the volumetric flow rate of regeneration air can reduce the time taken to reach the predetermined target humidity.

[0025] The step of controlling the volume flow of regeneration air having a substantially constant temperature through the regeneration sector based on a predetermined target humidity in the regeneration sector of the desiccant wheel may include controlling the volume flow of regeneration air having a substantially constant temperature through the regeneration sector based on a predetermined target humidity in the regeneration sector that is greater than 0% RH. The predetermined target humidity may be the humidity in the regeneration sector, which may be greater than 0% RH. When the humidity in the regeneration sector of the desiccant wheel is greater than 0% RH, the desiccant wheel may not be unnecessarily dried due to overheating of the desiccant wheel. Therefore, the heating cost of the regeneration air is reduced. The humidity in the regeneration sector may also depend on the extension or thickness of the wheel in the axial direction, the rotational speed of the wheel, and the volume flow of regeneration air through the regeneration sector.

[0026] The present disclosure also relates to a computer program comprising instructions that, when executed by a data processing unit of a control device of a desiccant dehumidifier, cause the control device to perform the method disclosed above. The present disclosure also relates to a computer-readable medium having the computer program stored thereon. The method may be embodied in preprogrammed software that can be implemented into a production unit suitable for utilizing the method. The preprogrammed software may be stored in the control device. Alternatively, or in combination, the software may be stored in a memory or computer located some distance from the control device.

[0027] The above-mentioned objects are also achieved by the desiccant dehumidifier initially defined, which also includes the following features: the control device can be configured to control the heater device to provide a substantially constant temperature of the regeneration air and control the volume flow of the regeneration air through the regeneration sector based on a predetermined target humidity in the regeneration sector of the desiccant wheel. The control device can be configured to control the heater device so as to provide a constant or substantially constant temperature of the regeneration air. The heater device can be driven by electricity. The power used for the heater device can be controlled by the control device. The substantially constant temperature of the regeneration air provided by the heater device can be selected based on a selected predetermined target humidity. The level of the selected substantially constant temperature is controlled by the control device. In addition, the control device can be configured to control the fan so as to achieve a volume flow of the regeneration air through the regeneration sector.

[0028] According to an example, the heater device includes a PTC heater. The PTC heater can generate a constant or substantially constant regeneration temperature. Furthermore, the PTC heater can generate a uniform or substantially uniform regeneration air temperature across the regeneration sector. Furthermore, the regeneration air flow is controlled using a regeneration air fan to achieve a target outlet moisture content. The PTC heater can have a flattening effect on the temperature distribution, thereby making the temperature uniform. PTC stands for positive temperature coefficient.

[0029] The predetermined target humidity in the regeneration sector of the desiccant wheel can be greater than 0% RH. When the humidity in the regeneration sector of the desiccant wheel is greater than 0% RH, the desiccant wheel may not be unnecessarily dried due to overheating of the desiccant wheel. Therefore, the heating cost of the regeneration air is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above objects and other objects, features and advantages of the present disclosure will be more fully understood by referring to the following illustrative and non-limiting detailed description of example embodiments of the present disclosure when considered in conjunction with the accompanying drawings.

[0031] Figure 1 A desiccant dehumidifier according to an example is schematically illustrated in perspective view;

[0032] Figure 2 schematically illustrates a desiccant dehumidifier connected to a space or room according to an example;

[0033] Figure 3 schematically illustrates a desiccant dehumidifier connected to a space or room according to another example;

[0034] Figure 4 shows a flowchart of a method according to an example; and

[0035] Figure 5 A control device according to an example is schematically illustrated. DETAILED DESCRIPTION

[0036] The present disclosure will now be described with reference to the accompanying drawings, in which preferred exemplary embodiments of the present disclosure are shown. However, the present disclosure may be implemented in other forms and should not be construed as limited to the embodiments disclosed herein. The disclosed embodiments are provided to fully convey the scope of the present disclosure to those skilled in the art.

[0037] Figure 1 A desiccant dehumidifier 1 according to an example is schematically illustrated in perspective view. The desiccant dehumidifier 1 includes a desiccant wheel 2 rotatably arranged about a central axis 4. A process air circuit 6 is arranged to direct process air 8 through a process sector 10 of the desiccant wheel 2. A regeneration air circuit 12 is arranged to direct regeneration air 14 through a regeneration sector 16 of the desiccant wheel 2. A purge air circuit 18 is arranged to direct purge air 20 through a purge sector 22. The purge air circuit 18 is arranged in fluid communication with the process air circuit 6 upstream of the desiccant wheel 2 and in fluid communication with the regeneration air circuit 12 upstream of a heater device 28. The heater device 28 is arranged in fluid communication with the regeneration air circuit 12 upstream of the desiccant wheel 2. The heater device 28 may include a PTC heater. A fan 26 is arranged in the regeneration air circuit 12 downstream of the desiccant wheel 2 and is configured to generate a flow of regeneration air 14 in the regeneration air circuit 12. The motor 32 is arranged to rotate the desiccant wheel 2 about the central axis 4 via a transmission 34 .

[0038] Figure 2 Schematically illustrated is a desiccant dehumidifier 1 connected to a space 80 or room according to an example. Figure 2, the desiccant wheel 2 comprises a process sector 10, a regeneration sector 16 and a purge sector 22. The process air circuit 6 is arranged to guide process air 8 through the process sector 10. A process fan 9 is arranged in the process air circuit 6 to generate a flow of process air 8 in the process air circuit 6. The regeneration air circuit 12 is arranged to guide regeneration air 14 through the regeneration sector 16. The purge air circuit 18 is arranged to guide purge air 20 through the purge sector 22. A fan 26 is arranged in the regeneration air circuit 12 downstream of the desiccant wheel 2. A damper 30 is arranged in the regeneration air circuit 12 downstream of the desiccant wheel 2. A heater device 28 is arranged in fluid communication with the regeneration air circuit 12 upstream of the desiccant wheel 2. Desiccant dehumidifier 1 further includes a first humidity sensor 50 arranged in process air circuit 6 downstream of desiccant wheel 2, a second humidity sensor 60 arranged in regeneration air circuit 12 downstream of desiccant wheel 2, and a third humidity sensor 70 arranged in a space 80 fluidly connected to process air circuit 6. Desiccant dehumidifier 1 further includes a dew point sensor 90 arranged in space 80. Control device 200 is connected to fan 26, damper 30, heater device 28, first humidity sensor 50, second humidity sensor 60, third humidity sensor 70, and dew point sensor 90. Damper 30 can be controlled to control the volumetric flow rate of regeneration air 14 passing through regeneration sector 16. Furthermore, the volumetric flow rates of both purge air 20 and regeneration air 14 passing through desiccant wheel 2 can be controlled by damper 30 in conjunction with the selected speed of fan 26 arranged in regeneration air circuit 12.

[0039] Figure 3 Schematically illustrates a desiccant dehumidifier 1 connected to a space 80 or room according to another example. Figure 3 In the embodiment, the purge air circuit 18 is arranged in fluid communication with the regeneration air circuit 12 upstream of the heater device 28. After passing through the purge sector of the desiccant wheel 2, the purge air circuit is arranged in fluid communication with the regeneration air circuit 12 downstream of the heater device and upstream of the desiccant wheel 2.

[0040] Figure 4 1 shows a flow chart of a method according to an example. The method is executed by a control device 200 for controlling a desiccant dehumidifier 1. The method involves Figure 1 and Figure 2The desiccant dehumidifier 1 disclosed in . Thus, the desiccant dehumidifier 1 comprises: a desiccant wheel 2, which is rotatably arranged about a central axis 4 of the desiccant wheel 1; a process air circuit 6, which is arranged to guide process air 8 through a process sector 10 of the desiccant wheel 2; a regeneration air circuit 12, which is arranged to guide regeneration air 14 through a regeneration sector 16 of the desiccant wheel 2; a fan 26, which is arranged in the regeneration air circuit 12 downstream of the desiccant wheel 2, the fan 26 being configured to generate a flow of regeneration air 14 in the regeneration air circuit 12; and a heater device 28, which is arranged in fluid communication with the regeneration air circuit 12 upstream of the desiccant wheel 2.

[0041] The method comprises the steps of controlling s101 the heater device 28 to provide a substantially constant temperature of the regeneration air 14 , and controlling s102 the volume flow of the regeneration air 14 having the substantially constant temperature through the regeneration sector 16 based on a predetermined target humidity in the desiccant wheel 2 .

[0042] The desiccant dehumidifier 1 further comprises a first humidity sensor 50 arranged in the process air circuit 6 downstream of the desiccant wheel 2, wherein the step of controlling s102 the volume flow rate of the regeneration air 14 through the regeneration sector 16 is further based on the current humidity in the desiccant wheel 2 determined by means of the first humidity sensor 50. The desiccant dehumidifier 1 further comprises a second humidity sensor 60 arranged in the regeneration air circuit 12 downstream of the desiccant wheel 2, wherein the step of controlling s102 the volume flow rate of the regeneration air 14 through the regeneration sector 16 is further based on the current humidity in the desiccant wheel 2 determined by means of the second humidity sensor 60. The desiccant dehumidifier 1 further comprises a third humidity sensor 70 arranged in a space 80 fluidically connected to the process air circuit 6, wherein the step of controlling s102 the volume flow rate of the regeneration air 14 through the regeneration sector 16 is further based on a target operating time t of the desiccant dehumidifier 1 for reaching the target humidity TH in the space 80 determined by means of the third humidity sensor 70. Desiccant dehumidifier 1 further includes a dew point sensor 90 disposed in space 80 fluidly connected to process air circuit 6, wherein the step of controlling (s102) the volumetric flow rate of regeneration air 14 through regeneration sector 16 is further based on a target dew point humidity °DP determined by dew point sensor 90. The step of controlling (s102) the volumetric flow rate of regeneration air 14 through regeneration sector 16 includes controlling the speed of fan 26 to control the volumetric flow rate of regeneration air 14. Desiccant dehumidifier 1 further includes a damper 30 disposed in regeneration air circuit 12 downstream of desiccant wheel 2, wherein the step of controlling (s102) the volumetric flow rate of regeneration air 14 through regeneration sector 16 includes controlling the damper 30 to control the volumetric flow rate of regeneration air 14. Furthermore, the volumetric flow rates of both the purge air and the regeneration air through the desiccant wheel can be controlled by the damper in conjunction with the selected speed of the fan.

[0043] The desiccant dehumidifier 1 further comprises a purge air circuit 18 arranged to direct purge air 20 through a purge sector 22 of the desiccant wheel 2, the purge air circuit 18 being arranged in fluid communication with the process air circuit 6 upstream of the desiccant wheel 2 and with the regeneration air circuit 12 upstream of the heater device 28, wherein the method comprises the following further step: controlling s103 the volumetric flow rates of the purge air 20 and the regeneration air 14 through the desiccant wheel 2 based on a predetermined target humidity in the desiccant wheel 2. The step of controlling s103 the volumetric flow rates of the purge air 20 and the regeneration air 14 through the desiccant wheel 2 comprises controlling the speed of the fan 26 for controlling the volumetric flow rates of the purge air 20 and the regeneration air 14 through the desiccant wheel 2. The step of controlling s103 the volumetric flow rates of purge air 20 and regeneration air 14 through desiccant wheel 2 may include controlling the volumetric flow rate of purge air 20 through purge sector 22 of desiccant wheel 2 relative to the volumetric flow rate of regeneration air 14 through regeneration sector 16 of desiccant wheel 2 .

[0044] The predetermined target humidity is the humidity in the regeneration sector 16 of the desiccant wheel 2, which may be greater than 0% RH.

[0045] Figure 5 The control device 200 of the desiccant dehumidifier 1 according to an example is schematically illustrated. The control device 200 includes at least one processor 201 and a computer readable medium 202. The control device 200 may be configured to perform the following operations when the computer program is executed by the at least one processor 201: Figure 3 The computer program includes computer-readable instructions that can be stored in a computer-readable medium 202 of the control device 200, such as a non-transitory hardware storage device.

Claims

1. A method for controlling a desiccant dehumidifier (1) performed by a control device (200): The desiccant dehumidifier (1) comprises: a desiccant wheel (2), the desiccant wheel (2) being rotatably arranged around a central axis (4) of the desiccant wheel (2); a process air circuit (6) arranged to direct process air (8) through a process sector (10) of the desiccant wheel (2); a regeneration air circuit (12) arranged to direct regeneration air (14) through a regeneration sector (16) of the desiccant wheel (2); a fan (26) arranged in the regeneration air circuit (12) downstream of the desiccant wheel (2), the fan (26) being configured to generate a flow of regeneration air (14) in the regeneration air circuit (12); as well as a heater device (28) arranged in fluid communication with the regeneration air circuit (12) upstream of the desiccant wheel (2), The method is characterized in that the method comprises the following steps: controlling (s101) the heater means (28) to provide a substantially constant temperature of the regeneration air (14); and The volume flow of regeneration air (14) having a substantially constant temperature through the regeneration sector (16) of the desiccant wheel (2) is controlled (s102) based on a predetermined target humidity in the regeneration sector (16).

2. The method according to claim 1, wherein The desiccant dehumidifier (1) further comprises a first humidity sensor (50) arranged in the process air circuit (6) downstream of the desiccant wheel (2), wherein the step of controlling (s102) the volume flow of the regeneration air (14) through the regeneration sector (16) is also based on the current humidity in the desiccant wheel (2) determined by means of the first humidity sensor (50).

3. The method according to any one of claims 1 and 2, wherein: The desiccant dehumidifier (1) further comprises a second humidity sensor (60) arranged in the regeneration air circuit (12) downstream of the desiccant wheel (2), wherein the step of controlling (s102) the volume flow of the regeneration air (14) through the regeneration sector (16) is also based on the current humidity in the desiccant wheel (2) determined by means of the second humidity sensor (60).

4. The method according to any one of the preceding claims, wherein The desiccant dehumidifier (1) further comprises a third humidity sensor (70) arranged in a space (80) fluidically connected to the process air circuit (6), wherein the step of controlling (s102) the volume flow of the regeneration air (14) through the regeneration sector (16) is also based on a target operating time (t) of the desiccant dehumidifier (1) for reaching a target humidity (TH) in the space (80) determined by means of the third humidity sensor (70).

5. The method according to any one of claims 1 to 4, wherein: The desiccant dehumidifier (1) further comprises a dew point sensor (90) arranged in a space (80) fluidically connected to the process air circuit (6), wherein the step of controlling (s102) the volume flow of the regeneration air (14) through the regeneration sector (16) is also based on a target dew point humidity (°DP) determined by the dew point sensor (90).

6. The method according to any one of the preceding claims, wherein The step of controlling (s102) the volumetric flow rate of the regeneration air (14) passing through the regeneration sector (16) comprises controlling the speed of the fan (26) for controlling the volumetric flow rate of the regeneration air (14).

7. The method according to any one of the preceding claims, wherein The desiccant dehumidifier (1) further comprises a damper (70) arranged in the regeneration air circuit (12) downstream of the desiccant wheel (2), wherein the step of controlling (s102) the volume flow of the regeneration air (14) passing through the regeneration sector (16) comprises controlling the damper (70) for controlling the volume flow of the regeneration air (14).

8. A method according to any one of the preceding claims, wherein The desiccant dehumidifier (1) further comprises a purge air circuit (18) arranged to direct purge air (20) through a purge sector (22) of the desiccant wheel (2), the purge air circuit (18) being arranged in fluid communication with the process air circuit (6) upstream of the desiccant wheel (2) and in fluid communication with the regeneration air circuit (12) upstream of the heater device (28), wherein the method comprises the following further steps: The volumetric flow rates of purge air (20) and regeneration air (14) through the desiccant wheel (2) are controlled (s103) based on a predetermined target humidity in the desiccant wheel (2).

9. The method according to claim 8, wherein The step of controlling (s103) the volumetric flow rates of the purge air (20) and the regeneration air (14) through the desiccant wheel (2) comprises controlling the speed of the fan (26) for controlling the volumetric flow rates of the purge air (20) and the regeneration air (14) through the desiccant wheel (2).

10. The method according to any one of claims 8 and 9, wherein: The step of controlling (s103) the volumetric flow rates of purge air (20) and regeneration air (14) through the desiccant wheel (2) comprises controlling the volumetric flow rate of the purge air (20) through the purge sector (22) of the desiccant wheel (2) relative to the volumetric flow rate of the regeneration air (14) through the regeneration sector (16) of the desiccant wheel (2).

11. The method according to any one of the preceding claims, wherein The step of controlling (s102) the volume flow of regeneration air (14) having a substantially constant temperature through the regeneration sector (16) of the desiccant wheel (2) based on a predetermined target humidity in the regeneration sector (16) includes controlling the volume flow of regeneration air (14) having a substantially constant temperature through the regeneration sector (16) based on a predetermined target humidity greater than 0% RH in the regeneration sector (16).

12. A computer program comprising instructions for causing a control device (200) of a desiccant dehumidifier (1) to perform the method according to any one of claims 1 to 11 when the program is executed by a data processing unit (201) of the control device (200).

13. A computer readable medium (202) having a computer program according to claim 12 stored thereon.

14. A desiccant dehumidifier (1), comprising: a desiccant wheel (2), the desiccant wheel (2) being rotatably arranged around a central axis (4) of the desiccant wheel (1); a process air circuit (6) arranged to direct process air (8) through a process sector (10) of the desiccant wheel (2); a regeneration air circuit (12) arranged to direct regeneration air (14) through a regeneration sector (16) of the desiccant wheel (2); a fan (26) arranged in the regeneration air circuit (12) downstream of the desiccant wheel (2), the fan (26) being configured to generate a flow of regeneration air (14) in the regeneration air circuit (12); a heater device (28) arranged in fluid communication with the regeneration air circuit (12) upstream of the desiccant wheel (2); and a control device (200), The invention is characterized in that the control device (200) is configured to control the heater device (28) to provide a substantially constant temperature of the regeneration air (14); and to control the volume flow rate of the regeneration air (14) through the regeneration sector (16) of the desiccant wheel (2) based on a predetermined target humidity in the regeneration sector (16).

15. The desiccant dehumidifier (1) according to claim 14, wherein: The heater device (28) comprises a PTC heater.

16. The desiccant dehumidifier (1) according to any one of claims 14 and 15, wherein: The predetermined target humidity in the regeneration sector (16) of the desiccant wheel (2) is greater than 0% RH.

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