BRPI1007585B1 - method for controlling an active desiccant dehumidifier and active desiccant dehumidifier system - Google Patents

Abstract

METHOD FOR CONTROLLING AN ACTIVE DESICTANT DEHUMIDIFIER AND ACTIVE DESICHANT DEHUMIDIFIER SYSTEM The present invention provides a method for controlling an active desiccant dehumidifier; the method comprising: a. The modulation of the air flow through a processing sector to control the amount of dehumidification; B. The modulation of the air flow through a reactivation sector as a function of the modulation of the processed air flow; and c. The modulation of the rotational speed of a desiccant wheel as a function of the modulation of the processed air flow. The present invention also provides a system for the aforementioned method.

Description

[001] The present invention generally relates to heating, ventilation and air conditioning (HVAC) systems and methods, as well as drying processing systems and methods, and more specifically to conditioner drying systems. of air or dehumidification that incorporate a thermally activated desiccant wheel. The present invention also provides an improved method for conserving / reducing the energy consumed when using such systems using desiccant wheels.

[002] Desiccant wheels and energy recovery wheels are the two types of wheels used in HVAC or for processing air conditioning. Desiccant wheels are used to transform moisture from one air stream to another. Desiccant wheels have two distinct types: “active” desiccant wheels and “passive” desiccant wheels.

[003] The “active” desiccant wheels use an external heat source to heat one of the air currents, to reactivate / regenerate a portion of the wheel. “Active” desiccant wheels have generally been used for industrial applications requiring high moisture removal, but are increasingly used in commercial HVAC applications. Examples of such active desiccant wheels and such systems are disclosed in various patent applications, for example, in U.S. Patent Nos. US 6,311,511, US 5,551,245 and US 5,816,065.

[004] "Passive" desiccant wheels do not use an external heat source and depend on the difference in relative humidity between two or more air currents to perform an operational transfer of moisture between the air currents. Examples of “passive” desiccant wheel systems and their use are disclosed in U.S. Patent Nos. US 6,237,354 and US 6,199,388. Once they are thermally activated, activated desiccant wheel systems use a substantial amount of heating energy (steam, electrical, etc.) to reactivate or regenerate the wheel, several methods have been adopted in the past with the aim of minimizing usage of reactivation energy with various control methods and / or the use of additional components. Methods such as energy recovery devices to transfer heat energy from processed air to a reactivation air inlet, or to transfer heat from a reactivated air outlet to the reactivation air inlet, resulted in “ excessive additional costs ”.

[005] Dehumidification is a process that removes moisture from the air. There are several known methods for dehumidifying air. However, the two commonly used methods are refrigeration and desiccant. In the case of using refrigeration as a dehumidification, moisture is allowed to condense on a cooling coil, hence, removing moisture from an air stream passing over the cooling coil. In the case of dehumidification using desiccants, the processing employed is one of absorption or adsorption. In absorption, either liquid or solid desiccants are used, typically halide salts or solutions. For adsorption, solid desiccants such as silica, activated alumina, molecular sieve, etc., are used.

[006] Systems based on desiccant dehumidification can be either multiple tower type, cyclic type, or continuous rotation type. It generally refers to the air to be dried as processed air, and the air used to regenerate the desiccant is referred to as regenerated air or reactivated air.

[007] In practice, refrigeration-based dehumidification systems are limited in terms of the moisture they can remove because in order to reach dewy moisture below freezing, an accumulation of frozen material occurs over the cooling coil making the most complex system and often requiring the provision of reheating generation. On the other hand, desiccant dehumidifying systems operate independently of the dew point of the air and, therefore, can reach dew points of very low humidity, something that is necessary for many industrial applications. Common and well-known examples of use are in pharmaceutical areas for drug production and in food processing areas, which require lower humidity or dew points than those that can be technically or economically achieved through just cooling.

[008] Also, hybrid systems, using both the refrigeration unit and the desiccant unit, are commonly used to assist in reducing energy use and to provide simple and reliable operation for the entire dehumidification system.

[009] Compared to refrigeration type dehumidifying units, desiccant dehumidification usually uses more heat energy, mainly for the regeneration or reactivation of the desiccant. Accordingly, over the years, several developments have occurred in the physical configuration of the desiccant equipment and in the control strategies for the capacity and energy control of the desiccant dehumidifying system to minimize its energy use.

[010] Desiccant dehumidifying units for dehumidifying / drying air at atmospheric pressure are generally nowadays of the rotary type, since the desiccant is contained in a rotating bed (or a wheel). The wheel moves on a constant or intermittent basis, although typically, in two compartments (or sectors), one for processing and the other for regeneration. In the air processing sector to be dehumidified (usually called processed air) it is passed through the wheel and is dried through contact with the desiccant. In the regeneration sector, air is generally drawn from the atmosphere, passed through a heat source which raises the temperature of the reactivated air, and is then passed through the remaining portion of the wheel, referred to as the reactivation sector or regeneration sector , heating the wheel and expelling water. Typically, the processing sector varies between 50 to 80% of the total bed / wheel area, although it could be less or more and the rest being the reactivation sector.

[011] Often another sector is added between the processing sector and the regeneration sector and is referred to as the purification sector. A third stream of air (usually called purified air) is passed through the purification section and used as a portion of the regenerated air. The incorporation of the purification sector helps in the recovery of some residual heat from the rotating wheel before entering the processing sector, hence, reducing the total energy requirement for regeneration, as well as improving the overall amount of moisture removed by the wheel.

[012] In typical desiccant units, the rate of processed air flow and the reactivation flow rate are generally fixed and are set or adjusted with the aid of manual or automatic dampers.

[013] In the design of a typical dehumidifying system to control the humidity in a given space, the airflow needed to control the space temperature can often be greater than the amount of dehumidified air needed to control the space humidity. In such cases a portion of the processed air is typically diverted around the dehumidifying unit and is then combined with the air leaving a dehumidifying unit and then the combined air is cooled (or heated) and then fed into the controlled space.

[014] Since desiccant dehumidifying systems inherently use a significant amount of heat energy for regeneration, efforts have been made to find ways and means to reduce the amount of heat used by the system. A typical and well-known system and method used is to control the heated temperature of the regenerated air before it enters the wheel reactivation sector.

[015] Another well-known system is that of controlling the amount of regenerated heat input by controlling the air temperature leaving the reactivation sector.

[016] Depending on the type and amount of relative humidity and the dew point control, when the space or the air conditioner is satisfied, the control strategy can employ the start / stop of the dehumidifier.

[017] Similarly, instead of such, automatic dampers can be used to continuously vary the amount of air by deflecting the dehumidifying unit to meet the needs of operation and design.

[018] The correlation of the processing and reactivation sector area, the speed of the rotating wheel, the relative flow rates of processed air and reactivated air and the speeds across the two sectors have been documented in Japan in the most recent decade, India and the USA resulting in robust mathematical modeling tools regularly used for the design, selection and incorporation of a desiccant wheel, in a finite way, in a dehumidifying unit. Such tools are being used regularly to perfect a dehumidification system when in the design and construction stage.

[019] Such study and development of a mathematical model is detailed in a document “Modeling of Rotary Desiccant Wheels” by Harshe, Utikar, Ranade and Pahwa, in 2005.

[020] In the case of rotary desiccant dehumidifying units, it is well known that the performance of the equipment when in the design and construction stage can be improved through the use of a mathematical modeling tool to select a particular percentage as a reactivation sector, as well as processing and reactivation flow rates, and also a given rotational bed speed. In such cases, under partial loads and instantly changeable moisture load, the ability to control dehumidification is achieved through the use of traditional control strategies described above, some of which are well known and well documented, for example, in the manual. Bry Air drawing book as well as in the Munters drawing manual.

[021] With traditional and known methods of dehumidification control, during the operation of such dehumidification systems, the reduction in the use of regeneration energy is somewhat limited.

[022] All of the aforementioned do not achieve the maximum desired energy reduction, or to an extent commensurate with changes in the instantaneous moisture load.

[023] Several examples of the prior art are provided below which are practiced to reduce the energy of regeneration and / or to regulate the speed of the desiccant wheel while improving the dehumidification capacity. U.S. Patent No. US 4,546,442 instructs on a control system based on a programmable microcomputer for fixed bed or multiple bed air dryers used to dehumidify compressed air or other compressed gases. The control system is used to monitor the level of humidity in the desiccant and determine whether a regeneration cycle is required and also to monitor the depressurization and full re-pressurization of the regeneration bed and also to analyze and indicate any valve malfunctions. The application of the invention is limited to a compressed air system.

[024] U.S. Patent No. US 4,729,774 instructs on the air temperature profile in the regeneration sector to improve dehumidifying performance.

[025] U.S. Patent No. US 4,926,618 instructs on a desiccant unit having means of recirculating reactivated air and controllable variable wheel speed means. The humidity of processed air is controlled by modulating a master wheel speed controller, the rate of reactivation of recirculated air and the entry of reactivated heat. The rates of processed and reactivated air flow through the wheel are fixed, and the reactivated air heater is controlled to maintain a constant temperature of the reactivated air leaving the wheel.

[026] U.S. Patent No. US 5,148,374 instructs on a system and method for real-time computer control of multiple wheel sorbent energy transfer systems by improving calculated mass transfer ratios. and by measuring the efficiency of the systems which are not subject to systems with long time constants. The method depends on the sensing at predetermined intervals of a set of predetermined parameters selected from the group of input temperature on the wheel, and output temperature of the wheel, etc., to send a control signal to a predetermined medium of a group of control means which includes controlling the temperature of the fluid flow. The purpose of the control method is to improve the response of the controlled device to a rapid change of load without causing unstable operation of the device and fluctuations resulting from the controlled variable.

[027] U.S. Patent No. US 5,688,305 instructs on a regeneration control device and method of regeneration for a desiccant dehumidifying system in which the reactivated air flow is controlled to maintain a constant reactivated air temperature and temperature. Inlet temperature of reactivated air is controlled at a fixed value. The dwell time in the reactivation is also controlled in an inverse proportion to the reactivated air flow. The purpose of this document is to reduce the over / extra generation of desiccant under partial load conditions, thereby enhancing the operational efficiency of the desiccant dehumidifier. The application cited is for drying granular material in a box or in a feeder using a re-circulated and dehumidified airflow, when the flow of granular material through the box can occur in batches or at a variable rate.

[028] U.S. Patent No. US 6,199,388 B1 instructs on a system and method for controlling the temperature and humidity level of a controlled space and is applied mainly in a combination of an enthalpy wheel, otherwise known as an energy recovery wheel, a cooling coil and a desiccant dehumidifying wheel which does not employ any external heat or energy input for reactivation. Additionally, it instructs on a means to change the performance of a “passive” desiccant wheel by changing the rotational speed in response to a sensitive and latent load in the controlled space. The control of the speed of the desiccant wheel is discussed and the intention is to control the dehumidifying capacity of the “passive” wheel instead of improving the energy efficiency of the dehumidifying process. It does not instruct on the use of the processed air to face or bypass dampers to control the capacity of the dehumidifying wheel. Both supply (processing) and exhaust (reactivation) air flows are maintained at a constant value across all load conditions.

[029] U.S. Patent No. US 6,355,091 B1 instructs on a unitary ventilation and dehumidification system to supply external ventilation air to a conditioned space. The unit includes a desiccant wheel which is rotated at a slow speed to achieve more dehumidification and at a fast speed to achieve more heat recovery. Heat can be added to the space exhaust air upstream of the desiccant wheel to enhance its dehumidifying performance and to prevent the formation of ice during winter operations. Both the supply and exhaust air flows are fixed, no bypass damper is used, and the adjustment of the rotor speed is performed by selecting the operating mode and not by increasing efficiency.

[030] U.S. Patent No. US 6,767,390 B2 instructs on a method for controlling the performance of a multi-bed and fixed-bed desiccant dryer for compressed air and gas applications and for improving the regeneration and purification cycles to release the gas at the desired dew point. The intended field of application is compressed air for use in instruments.

[031] U.S. Patent No. US 7,017,356 B2 instructs on an HVAC system to cool and dehumidify conditioned comfortable spaces which includes a desiccant wheel in a passive dehumidifying arrangement in which the wheel speed varies with air flow , and the wheel is operated for at least an established period during start-up to prevent an outbreak of moist air in the conditioned space. This patent application also instructs on the use of a sensitive and passive recovery device and a cooling coil to precondition the outside air before mixing it with the return air from the conditioned space.

[032] U.S. Patent No. US 7,101,4141 B instructs on a method for reducing a sorbent concentration to a fluid stream processed using a sorption bed system which includes a material that is rotated through multiple zones, in addition to traditional processing and regeneration zones, in which one or two pairs of independent and recirculated fluid streams, other than the processed and regenerated fluid streams, are used to isolate the processed and regenerated flow streams, one from the another. The purpose of insulation can be to prevent cross-leakage of air between the processing and reactivation zones, permeation of sorbent material through the sorption stream, or the formation of condensation or ice on the sorption stream.

[033] U.S. Patent No. US 7,338,548 B2 instructs on the use of an apparatus and a control method to condition humidity and temperature in a stream of air processed from a desiccant dehumidifier, where a portion of the processed unloaded air is used to preheat the regenerated air through the use of an air to air heat exchanger. The field of use of the invention lies in the drying of structures and the remedying of water damage.

[034] U.S. Patent No. US 7,389,646 B2 is a divisional patent from an earlier work and is similar to U.S. Patent No. 7,017,356 B2 by the same inventor. It is also intended for the cooling and dehumidification of conditioned comfort spaces and instructs on an HVCA system which includes a passive desiccant wheel, in which the wheel speed varies with the air flow and depends on the factor of the wheel being energized by at least an established period, and started, and employs a heat recovery system upstream of the wheel to enhance the system's ability to dehumidify air.

[035] Most of the prior art strategies have only been partially successful with regard to limiting and reducing the use of reactivation energy, not commensurating with the reduction of moisture load under partial load conditions.

[036] Also, during the use and application of the desiccant wheel and the system, there is usually a considerable change in the instantaneous moisture loads, in the fresh air, if treatment is required, and in the latent internal loads within the space where the humidity must be controlled based on changes in temperature and external humidity, and product and occupancy loads.

[037] Therefore, there is a need for a control method in conjunction with the necessary correlated components that will substantially reduce the use of reactivation energy and that responds not only to changes in the dynamic / instantaneous moisture load, but also simultaneously allows for the improvement of energy use in the wheel during these changes in the moisture load. Objectives of the Invention

[038] The general objective and purpose of the invention is to substantially reduce the accumulative energy used in the operation of a thermally activated desiccant dehumidifying system. Energy reduction is generally achieved by modulating the energy consumed by the desiccant unit in response to instant changes in humidity in the ambient air and / or in the humidity load in the controlled space, and in the change in humidity of the processed stream. Such instant moisture changes and resulting moisture load require the need to control the capacity of the dehumidification system.

[039] With a constantly changing and changing instantaneous moisture load, this control of dehumidification capacity is mainly achieved by controlling the air flow through the wheel processing sector; the optimum / minimum energy usage in the dehumidifier is achieved by means of proportionally controlling the air flow through the reactivation sector and keeping the reactivated air temperature constant, while simultaneously and proportionally adjusting the rotation speed of the wheel in such a way that a improved efficiency is achieved.

[040] While methods for controlling the capacity of the dehumidification system are established, the present invention provides an innovative method, which achieves a substantial reduction in the use of energy at partial load when compared to previously known methods.

[041] The objectives of the invention are achieved by means of a system and a method of controlling the dehumidifying capacity comprising:

[042] a) the control of the air flow through the rotor processing sector, and the control of a constant temperature of the reactivation inlet, and the control of the reactivated air flow as a function of the processed air flow, and also of rotor speed control as a function of the processed air flow, and the control functions are based on the instantaneous processed air flow ratio to design the processed air flow and the functions are all exponent functions with the exponents resting on anywhere in the range of 0.5 to 2.0, and with the exponents for each of the controllable variables not necessarily being equal;

[043] b) the control of the air flow through the rotor processing sector, and the control of a constant temperature of the reactivated heat source, for example, through the use of a steam at a constant pressure as the heat source of reactivation and the use of a two-position steam valve on the reactivated air heating coil, and by controlling the reactivated air flow as a function of the processed air flow, and also by controlling the rotor speed as a function of the processed airflow, and the control functions are based on the instantaneous processed airflow ratio to draw the processed airflow and the functions are all exponent functions with the exponent resting somewhere in the range of 0 , 5 to 2.0, and with the exponents for each of the controllable variables not necessarily being equal;

[044] c) controlling air flow through the rotor reactivation sector while maintaining a constant air flow through the processing sector and controlling a constant reactivation inlet temperature, and also controlling the rotor speed as a function of the reactivated air flow, and the control functions are based on the instantaneous reactivated air flow ratio to draw the processed air flow and the functions are all exponent functions with the exponent resting somewhere in the range of 0.5 to 2.0;

[045] d) control of air flow through the rotor reactivation sector while maintaining a constant air flow through the processing sector and control of a constant temperature of the heat source, for example, through the use of a current at a constant pressure as a reactivated heat source and oppose through the use of a two-position steam valve on the reactivated air heating coil, and also by controlling the rotor speed as a function of the reactivated air flow , and the control functions are based on the ratio of the instantaneous reactivated air flow to plot the processed air flow and the functions are all exponent functions with the exponent resting somewhere in the range of 0.5 to 2.0;

[046] e) the control of the air flow through the rotor processing sector and the control of a constant reactivated discharge temperature, and through the control of the reactivated air flow as a function of the processed air flow, and also through rotor speed control as a function of the processed air flow and the control functions are based on the instantaneous processed air flow ratio to design the processed air flow and the functions are all exponent functions with the exponent resting somewhere in the range of 0.5 to 2.0, and with the exponents for each of the controllable variables not necessarily being equal;

[047] f) the control of the air flow through the reactivation sector of the rotor while maintaining a constant air flow through the processing sector and the control of a constant temperature of the reactivated discharge, and also through the control of the speed of the rotor as a function of reactivated airflow, and the control functions are based on the instantaneous reactivated airflow ratio to draw the processed airflow and the functions are all exponent functions with the exponent resting somewhere in the variation of 0.5 to 2.0.

[048] Another objective of the invention is to provide a system and a method for the control of the dehumidification capacity in accordance with the four control scenarios described above, and additionally to incorporate a purification sector arranged sequentially between the reactivation sector and the processing sector of the rotors with a concurrent air flow through the processing sector and the purification sector, and controlling the purification sector as a function of the reactivated air flow, the control function based on the air flow ratio instant reactivated and the reactivated air flow designed and having an exponent function with the exponent resting anywhere in the range of 0.5 to 2.0.

[049] Another objective of the invention is to provide a system and a method for the control of the dehumidification capacity in accordance with the four control scenarios described above and additionally incorporate at least a pair of purification sectors arranged between the processing sector and the reactivation sector and each of the pairs having the means to recirculate the air through them in accordance with the North American patent application No. US 7,101,414 B2, the improvement being the control of the rate of recirculation of the purified air as a function of the rotor speed, and the function based on the instantaneous rotor speed ratio to draw the rotor speed and the function being an exponent function with the exponent resting somewhere in the range of 0.5 to 2, 0.

[050] In the aforementioned realizations there is an additional objective which is to provide a design feature for a basic and vacuum-opposed cabinet to allow the size of the reactivation sector to be easily adjusted at the time of manufacture or after installation in the field to additionally perfect the design for any given application for the dehumidification system. The improvement is achieved by selecting the relative size of the processing sector and the reactivation sector that allows the lowest use of reactivation energy under design conditions and / or the lowest processed discharge humidity.

[051] One or more of the aforementioned objectives of the invention should provide a thermally activated dehumidifying system employing an “active” desiccant rotor in such a way that a total advantage is achieved because of the dynamic behavior of the desiccant rotor under varying partial load or under processed flow conditions.

Brief Description of the Invention

[052] Accordingly the present invention provides an apparatus for dehumidifying air fed in an enclosed space or in a processing or drying box, the apparatus comprising:

[053] (a) an accommodation defining an interior space;

[054] (b) the interior space being separated by means of a separator in a feed portion to contain a stream of fed air and a regeneration portion to contain a stream of regenerated air, the feed portion being provided with an inlet to receive air supply and an outlet to supply air to the enclosed space, the regeneration portion being provided with an inlet to receive the regenerated air and an outlet to discharge the regenerated air;

[055] (c) a rotating desiccant wheel positioned in such a way that a portion of the wheel extends into the feed portion and a portion of the wheel extends into the regeneration portion, the wheel being rotated through the stream of fed air and the stream of air regenerated to dehumidify the flow of fed air;

[056] (d) a heat source to heat the stream of regenerated air in order to regenerate the desiccant wheel as it spins through the stream of regenerated air; and

[057] (e) at least one deflection damper between the inlet and outlet of the feed portion to control the amount of air fed through the desiccant wheel by means of selectively deflecting the desiccant wheel.

[058] In one embodiment, the device may be a conventional HVAC unit or a hybrid air conditioning and dehumidifying device.

[059] In another embodiment, the regeneration portion is provided with a fan to move the stream of regenerated air.

[060] In another embodiment, a duct or control means is provided to allow recirculation of a portion of the regenerated air. In a preferred embodiment, a damper and / or a speed control means is provided to allow modulation of the air flow through the regeneration portion.

[061] In another embodiment, the feed portion is provided with a fan to move the fed air stream; a cooling coil is positioned in the stream of regenerated air; with the rotating desiccant wheel being positioned downstream of the cooling coil.

[062] In another embodiment, a speed regulation mechanism is provided to vary the rotational speed of the desiccant wheel to control the amount of moisture removed from the fed air stream and / or to minimize the amount of heat transferred to the stream of powered air.

[063] In an additional embodiment, the heat source is a direct gas-fired combustor. In an additional embodiment the heat source is electricity used in resistance heaters.

[064] In an additional embodiment, the heat source is a source of constant temperature such as steam or hot water.

[065] In an additional embodiment, the heat source is a source of heat recovered from a cooling condenser or heat recovered from another process.

[066] In an additional embodiment, the heat source is a combination of two or more of the heat sources described above, but used sequentially.

[067] In a preferred embodiment, a means of modulating heat is provided for the heat source to regulate the temperature of the regenerated air stream.

[068] In another embodiment of the invention, the modulation means is provided for the deflection damper to regulate the amount of air fed through the desiccant wheel.

[069] In another embodiment, the desiccant wheel is sized to handle a desired fraction of the air flow processed by the air conditioning system.

[070] In another embodiment, the means are provided for cooling and / or heating the air fed after it passes through the dehumidifier and before it is released into the conditioned space.

[071] In another embodiment, the system includes a compartment housing a condenser, the device being provided with a duct or an opening connecting the regenerated inlet air to the compartment housing the condenser in order to allow air preheating input regenerated by the capacitor.

[072] The invention also provides a method for controlling the temperature and humidity of a conditioned space or of a processing or drying box, the method comprising the steps of:

[073] (a) provide an air conditioning system in communication with the conditioned space;

[074] (b) provide an active desiccant wheel system defining an interior space; the interior space being separated by means of a separator in a feed portion to contain a stream of fed air and a regeneration portion to contain a stream of regenerated air, the feed portion being provided with an inlet to receive air fed from from the enclosed space or the air conditioning system and an outlet to supply air to the air conditioning system or enclosed space, the regeneration portion being provided with an inlet to receive the regenerated air and an outlet to discharge the regenerated air; a rotating desiccant wheel positioned in such a way that a portion of the wheel extends into the feed portion and a portion of the wheel extends into the regeneration portion, the wheel being rotated through the stream of fed air and the stream of regenerated air to dehumidify the stream of powered air; a heat source to heat the stream of regenerated air in order to regenerate the desiccant wheel as it turns through the stream of regenerated air; and at least one bypass damper between the inlet and outlet of the feed portion to control the amount of air fed through the desiccant wheel by means of selectively bypassing the desiccant wheel;

[075] (c) connect the active desiccant wheel system to the air conditioning system;

[076] (d) to cool and / or heat the flow of air fed by passing it through the air conditioning system; and

[077] (e) dehumidify the air stream fed by passing it through the active desiccant wheel system while turning the wheel through the air stream fed and the regenerated air stream to exchange moisture and / or heat between the air currents; and,

[078] (f) releasing air from the air conditioning system to the enclosed space.

Brief Description of Drawings

[079] These and other realizations and advantages of the present invention will become more fully apparent from the following description and accompanying drawings, in which:

[080] Figure 1 (a & b) is a schematic drawing of a typical thermally activated desiccant dehumidifying unit shown along with the regeneration blower and shows a typical / classic 25% regeneration sector;

[081] Figure 2 (a & b) is a schematic drawing of a typical thermally activated desiccant dehumidifying unit shown along with the regeneration blower and shows a typical / classic 25% regeneration sector, and also includes a purification;

[082] Figure 3 (a & b) is a schematic drawing of a typical thermally activated desiccant dehumidifying unit shown along with the regeneration blower and shows a typical / classic 25% regeneration sector, and also includes a pair of purification sectors;

[083] Figure 4 (a & b) is a schematic drawing of a typical thermally activated desiccant dehumidifying unit shown along with the regeneration blower and shows a typical / classic 25% regeneration sector, and also includes two additional pairs purification sectors;

[084] Figure 5 (a & b) is a schematic diagram showing a typical dehumidification system and method of the prior art;

[085] Figure 6 (a & b) is also a schematic diagram showing a drying system and method typical of the prior art;

[086] Figure 7 (a & b) is also a schematic diagram showing a drying system and method typical of the prior art and also includes a purification sector;

[087] Figure 8 (a, b, c, d & e), are schematic drawings showing an embodiment of the system and method of the present invention;

[088] Figure 9 is a schematic drawing showing an embodiment of the present invention as a flow chart for the drying / dehumidifying process;

[089] Figure 10 (a & b) is a schematic drawing and an embodiment of the present invention as a diagram showing a product drying system and method;

[090] Figure 11 (a, b & c) is a graphical representation showing energy savings with the present invention when compared to the prior art;

[091] Figure 12 is a schematic drawing showing an embodiment of the system and method of the present invention and also includes several HVAC components that can be allowed and used or not allowed and not used.

Detailed Description of the Invention

[092] The present invention will now be described with reference to the accompanying drawings which are illustrative of certain embodiments of the invention. Variations and modifications are possible without departing from the spirit and scope of the invention.

[093] Figure 1 (a) is a typical flow chart of desiccant dehumidifier. As previously mentioned, a typical desiccant wheel / rotating bed 1 has a processing sector 2 and a regeneration or reactivation sector 3. The dehumidifier incorporating such a desiccant wheel / bed 1 would have a processed flow 6, as well as a regenerated flow 8. The regenerated flow is increased in temperature by passing over a heat source 10 before entering the regeneration part of the bed 3. The regenerated air leaving regeneration sector 3 of the web is exhausted 9 with the aid of the blower 5 The desiccant bed / wheel 1 is rotated through the reactivation and processing compartments with the aid of a bed operating arrangement 4.

[094] Figure 1 (b) shows a typical sector division of wheel 1. Processing sector 2, in a typical unit, is 75% of the total bed area, as shown and can, in practice, generally vary from 50% to 80%, but it can be designed to be even smaller or taller. The remaining area of the desiccant bed is shown as the reactivation sector 3 and can vary between 20% and 50% but can be designed to be smaller or higher.

[095] Figure 2 (a) shows the addition of another sector, referred to as the purification sector 11.0 The purification sector varies from 5 to 40% of the total bed area, the remainder being divided between process 2 and the reactivation area 3. When the wheel rotates from reactivation sector 3 to processing sector 2, the bed is still warm. It is well known that the hot portion of the bed, particularly if it is of the silica gel type, will begin to play (ie, remove moisture) when it cools. Therefore, a certain portion of the bed is substantially inactive when performing the dehumidification function while it is still hot. This segment or portion of the bed is often sectioned and transformed into a purification sector 11. Air 12 is passed over this sector 11, where the bed is hot, hence, air 13 is preheated before to pass through reactivation sector 3, hence both reducing the required reactivation energy input and also cooling that portion of the bed before entering processing zone 2, in which the dehumidification performance through processing sector 2 is intensified. In addition, less heat is communicated to the processed air because the bed is cooled when it enters the processing sector.

[096] Figure 2 (b) shows a desiccant wheel / bed 1 from another angle, where several sectors are marked, and although shown in a typical way these areas of sectors can vary, as explained above.

[097] Figure 3 (a) shows another flow chart of a desiccant bed / wheel system 1 where a pair of sectors (11 a, 12) has been added. In such a configuration it is typical to continuously circulate a given amount of air flow through these sections in a closed loop, with the aid of a separate fan 15. The recirculated air acts as a buffer between the process and the reactivation of air currents capturing leaks of air or diffusion of humidity between the processed and reactivated air currents and, thus, intensifying the system performance. In some cases, the recirculated air flow can also transfer heat between sectors in the same way as the purification sector shown in Figure 2, further enhancing system performance. It should be noted that the air flow in the recirculation loops described in all Figures can be in any direction with the most advantageous direction depending on the specific application. Figure 3 (b) shows the desiccant bed / wheel 1 from another angle, with several sectors marked and although shown in a typical way, these sector areas can vary as clearly explained here above.

[098] Figure 4 (a) is a flow chart of a rotating desiccant bed / wheel 1 where more than a pair of purification sectors 11a, 12, 17 and 18 have been added. In such a configuration it is typical to circulate a given amount of air 13, 19 through these sections in a closed loop by means of separate fans 15, 21.

[099] Figure 4 (b) shows the desiccant bed / wheel 1 from another angle, with several marked sectors and also shows, in a typical way, that these sectors can vary, as clearly explained here above.

[100] Figure 5 (a & b) shows a typical and traditional dehumidification system for a controlled space 27. In this system, for example, the cooling needs for the space to be dehumidified need a certain amount of air supply to be passed through the desiccant wheel to satisfy the space dehumidifying needs. To achieve this, it is a common practice to take a portion of the air through the dehumidifier and deflect the balance 25 to reach the total air flow fed and passed through the cooling coil and release into the environment (room). There is often a need for fresh air supply 31 to meet ventilation / pressurization requirements. Fresh air is usually introduced at the inlet of the dehumidifier, in combination with the air returning 28 from the controlled space. It may be advantageous to cool / heat the fresh air before combining it with the air returning using the air heating and cooling means 22 and 23 as shown in the Figure. In this typical flowchart / schematic drawing, dampers are used to control the air flow. The flow of fresh air is controlled with the aid of damper 35. Bypass damper 32 is used to control the flow that needs to be bypassed from the desiccant dehumidifying unit. The general supply of the air flow is controlled with the aid of the damper 33 positioned, normally, after the air flow fed. Each of these dampers can be adjusted manually or automatically using appropriate actuators and controls.

[101] The regenerated flow is also controlled with the aid of a damper usually positioned after the reactivation fan 5. The regeneration heat input source 10 can be electric, steam, gas or oil combustion, thermal fluid such as such as hot water, cooling condenser heat, recovered from other processing, or any combination of those that can heat the reactivated air to the temperature required for proper application. The energy input of reactivated heat is regulated by means of a thermostat 30 which is generally positioned before the desiccant bed. This thermostat 36 can be located after the desiccant bed in the reactivation “out” section as shown in Figure 5b. And, in some cases the alternating location results in a reduced annual use of reactivated heat compared to the positioning of the control thermostat before the desiccant rotor.

[102] In both the aforementioned dehumidifying systems and the reactivated heat input control methods, the currently and commonly used control strategies will feel the “satisfaction” of the relative humidity or humidity level of a given space or air processing or supply and will stop the reactivated air flow, bed rotation and reactivated heat input when the humidity is satisfied, commonly referred to as “on-off” control ... In another known method, commonly used with heat sources with temperature fixed such as steam or hot water, the air flow is modulated to regulate the unit's dehumidifying capacity.

[103] Figure 6 (a) shows a typical dehumidifying system used for drying applications. In this system, the dehumidified air 7 is heated through a heat source 22 according to the material requirement in the drying box 37. The returned air 28 carrying moisture from the product is passed over a cooling coil 23 and passed through the wheel / drying line 1 to absorb moisture.

[104] The regenerated air flow 8 is provided by means of a reactivation combustion 5. Heat source 10 is used to raise the temperature based on the specific design of the unit. The reactivation inlet temperature is controlled via the thermostat.

[105] Figure 6 (b) shows the desiccant bed / wheel from another angle. Processing sector 2 in a typical unit is 75% of the total bed area as shown and can, in practice, generally range from 50% to 80%, but can be designed to be even smaller or taller. The remaining area of the desiccant bed is shown as the reactivation sector 3, and can vary between 20% and 50%, but can be designed to be even smaller or higher.

[106] Figure 7 (a) shows a typical dehumidifying system for a drying application. This is similar to the system explained in Figure 6 (a & b) except that a purification section 11 has been added. This purification section can vary from 5 to 40% of the total bed area. The object of using a purification sector has already been explained previously.

[107] Figure 7 (b) shows a desiccant bed / wheel 1 from another angle, where the various sectors are marked and although shown in a typical way the areas of these sectors can vary, as explained above.

[108] Figure 8 (a) shows a typical dehumidification system. In this system there is an “internal” bypass 39 interconnected with the processed airflow 6 through a face and a bypass damper 40. Based on the measured humidity in the drawn space 27, and with instantaneous and changing charges, the face and the deflection damper 40 modulate the amount of air flow passing through the wheel while deflecting the rest. If and when there is a need to supply fresh air 31 to the drawn space, fresh air is generally introduced at the inlet of the dehumidifier and is combined with air returning 28 from the drawn space 27. Depending on the application, it may be advantageous to heat or cool the fresh air before it is mixed with the return air.

[109] Air from the outlet of dehumidifier 38 can be mixed with return air 28 before passing through a cooling coil 24 and filters 44, 45 and being released as supply air 26 into the drawn space 27.

[110] The reactivated air flow 8 passes through a heat source 10, which raises the air temperature based on the specific design of the unit. Thermostat 30 controls the temperature according to the established point. To control the reactivated air flow, the speed of the reactivation combustor 5 is continuously variable with a design suitable for this purpose. In order to achieve an improved performance, the speed of the rotor is also varied through an operational arrangement of variable bed speed 4.

[111] Figure 8 (b) is a schematic drawing of an example of a typical dehumidification space system. This example is similar to the example in Figure 8 (a) except that a purification sector 11 is that provided in the bed / desiccant wheel. The purification sector may vary may vary from 5 to 40% of the total bed area. The remainder being divided between processing area 2 and reactivation area 3. Air 12 is passed over this sector 11 where the bed is not hot, hence, air 13 is preheated before making it passes through the reactivation sector 3, thereby reducing the required reactivation energy input and also cooling that portion of the bed before entering processing zone 2, in which the dehumidification performance through processing sector 2 is improved . In addition, less heat is communicated to the processed air because the bed is cooled when it enters the processing sector.

[112] Air from the outlet of dehumidifier 38 can be mixed with the return air 28 before passing through a cooling coil 24 and filters 44, 45 and being released as fed air 26 into the drawn space 27.

[113] The reactivated air flow 28 passes through a heat source 10 which raises the temperature based on the specific design of the unit. Thermostat 30 controls the temperature according to the established point. To control the reactivated air flow, the reactivation combustor 5 has a continuously variable speed with a design suitable for this purpose. In order to achieve an improved performance, the speed of the rotor is also varied through an operational arrangement of variable bed speed 4.

[114] Figure 8 (c) is a schematic drawing of an example of a typical space dehumidification system. This example is similar to the example in Figure 8 (a) except that a pair of purification sectors 11a, 12 has been provided in the bed / desiccant wheel. In such a configuration, it is typical to circulate the air in sectors 11a, 12 in a closed loop using a separate fan 15. The heat from the wheel in section 12 following the reactivation sector can be taken / collected and passed on to “pre - heat ”the wheel in sector 11a following the processing sector with the aid of the marked air flow 13.

[115] The mixed air 38 from the dehumidifier can be mixed with the returned air 28 and then passed through a cooling coil 24 to cool the fed air 26 as required to cool the drawn space 27.

[116] The reactivated air at the inlet 8 passes through a filter 42 and the temperature of this air is raised through a heat source 10 based on the specific design of the unit. This temperature is controlled and kept constant by means of a thermostat 30. In order to continuously vary the air flow, a reactivation combustor 5 has its speed continuously varied with a design suitable for this purpose. In order to achieve an improved performance, the speed of the rotor is also varied through an operational arrangement of variable bed speed 4.

[117] Figure 8 (d) shows a schematic drawing of an example of a typical dehumidification system. This example is similar to the example in Figure 8 (c) except that another pair of purification sectors 17, 18 has been added. In such a configuration, it is typical to circulate a given amount of a5 13,19 through these pairs of sectors in two separate closed loops with separate fans 15, 21. As previously mentioned, the air flow in each of the closed loops can be in any direction depending on which direction is most advantageous.

[118] The mixed air 38 from the dehumidifier can be mixed with the return air 28 and passed through a cooling coil 24 to cool the fed air 26 to cool the space 27.

[119] The reactivated air at the inlet 8 passes through a filter 42 and the temperature of this air is raised through a heat source 10 based on the specific design of the unit. This temperature is controlled and kept constant by means of a thermostat 30. In order to continuously vary the air flow, a reactivation combustor 5 has its speed continuously varied with a design suitable for this purpose. In order to achieve an improved performance, the speed of the rotor is also varied through an operational arrangement of variable bed speed 4.

[120] Figure 8 (e) shows a schematic drawing of a typical dehumidification system. This is an example of a pharmaceutical production area for which the design conditions of 15% and 30% RH at 75 ° F have been selected for room / room 27. The amount of total air fed 26 calculated in this example is 4000 cfm. To satisfy the cooling needs of the space and the removal of moisture, 600 cfm is taken as return air 28. The required fresh air 31 (600 cfm) is passed over the cooling coil 23 and is mixed with the return air 28 The face and deflection damper 40 control the air flow through the deflection / desiccant wheel. The return air 28 (2800 cfm) is mixed with the processed air 7 to provide the desired flow of fed air 26. All air is then passed through the cooling coil 24 to provide the desired room / room temperature.

[121] Figure 9 shows a flow chart for the drying / dehumidifying processing system. Ambient air 31 is passed through the cooling coil 23 to reduce the moisture load and is cooled. The bypass damper 32 modulates the air flow to be passed through the desiccant wheel and the remainder through the bypass. The mixed air 38 (external process 7 and deflected air 39) is passed over heating sources 24 / cooling 22 and is tempered depending on the supply air requirement 26.

[122] The regenerated flow 8 is also controlled with the aid of a shock absorber 34 generally positioned after the regeneration combustion 5. The regenerated heat inlet 10 can be electrical, steam, gas combustion or from a variety of sources that can raise the temperature based on the specific design of the unit. This temperature is controlled by means of thermostat 30.

[123] Figure 10 (a) shows a product drying system and method. In this system, based on the conditions required in the drying box 37, the mixed air (processed air 7 and bypass air 39) 38 is passed over a processing heat inlet 22 to provide the necessary drying temperature. The return air 28 is cooled through a cooling coil 23 and blown through the processing sector 2 and the purification sector 11 of the rotor. The face and the bypass damper 40 are used to control the flow that needs to be bypassed from the dehumidifier. The air leaving the purification sector is recycled and mixed with the return airflow from the cooling coil. This allows the dehumidifier to release dry air. The purification sector generally ranges from 5 to 40% of the total area, the remainder being divided between processing areas 2 and reactivation area 3. The reactivation inlet temperature is controlled via thermostat 30.

[124] Figure 10 (b) shows the desiccant bed / wheel 1 from another angle where the various sectors are marked and although shown in a typical way, the sector division can vary.

[125] Figure 11 (a) compares the annual post-cooling requirement when different control options are used.

[126] Figure 12 is a schematic flowchart showing the various options for HVAC elements. Each of the elements can be included or not included based on the performance requirements of the application. The general amount of fed air to be passed through the cooling coil 59 / heating source 60 / dehumidifier 57 is based on the requirement of the space to be conditioned. The return air 28 can pass through a cooling coil 54 or through a heating coil 53 to give a desired condition for mixing with fresh air 31. Fresh air 31 can pass through a heat recovery unit 50 if the required temperature needs to be increased and heating is required via heat source 22. Fresh air can be cooled., if it is advantageous, using cooling coil 23. The mixed air passes through heating source 55 and the cooling source 56 based on the requirement, and then passes through the face and bypass damper 40. This controls the flow that needs to be passed through the desiccant wheel and dehumidified. The exhausted air passes through the heat recovery unit 52 to the outside through the combustion 23. The regenerated air passes through the heat recovery unit 49 and then passes through the heat source 10 to raise the temperature as required. specific design of the unit. The reactivated air flow from reactivation sector 3 passes through heat recovery unit 48 and through regeneration combustion 5. Using the heat recovery unit reduces the load. Thermostat 30 controls the temperature of the reactivation inlet after the heat source, or alternatively it can be located and controls the temperature of reactivated air leaving the wheel desiccant.

[127] As previously explained, the invention relates to a method and system for the control capacity of the desiccant dehumidifier, which has an active desiccant wheel. As there are instantly changing moisture loads, there is a need to control the capacity of the unit and the dehumidifying system. While there are several control methods currently known and practiced for reducing reactivation use, this invention provides an innovative method that substantially reduces reactivation energy compared to previously known methods.

[128] In the present invention, the fundamental approach is to continuously provide a means to continuously vary the amount of air that will deviate from the desiccant wheel, outside the total processed flow. This reduction in the flow processed through the desiccant unit generally identifies the change in instantaneous moisture loads. When the flow processed through the desiccant wheel is reduced, there is no longer a need to retain the total regenerated flow through the reactivation sector of the wheel. Where the regenerated flow is correspondingly reduced in some definite correlation, a considerable reduction is achieved with respect to the use of regeneration energy. In this invention, through the control function, the regenerated flow can be made to continuously reduce or increase based on the continuously variable processed flow rate through the processing sector. With changes in technology, it is now more economical and common to use variable operating speeds based on the various known methods which now allow a continuous variation in the reactivated air flow.

[129] Similarly, it is also a basis of the invention to use such technology for a continuous variation of speed of the rotational speed of the wheel, also through a correlated control function. In this case, the development of the control function, the use is made of the knowledge of the mathematical model tool “DRI Cal”, or any other similar tool, for example, “Procal”, both of which are similar tools currently in use by worldwide for the selection of a geometry and flow from a desiccant unit / wheel.

[130] During the development of this invention of continuously controlling the process of dehumidifier variables, the use of energy was compared with several known and practiced control methods. To develop the invention, first a sampling project was selected with facts and physical assumptions, typical of the design of a dehumidification application. For this, 30% RH at 70 ° F was selected as a design condition.

[131] To achieve a better spectrum of the energy saving potential, a lower RH of 15% at 70 ° F was also selected for the same pharmaceutical application. The city of Zebulon, NC was selected due to the climatic conditions typical of the Southeast region of the United States. However, to demonstrate the effect of more humid climates, the city of Mumbai, India was selected as being typical. A flow chart was made and prepared for the sample project / drawing. With hourly weather data available and used today to provide a more detailed load profile for the design of the project, climatic environmental housings have been created in increments of 10 particles / lb of air with an average and often coincident dry lamp temperature occurrence in hours / year. This allowed the calculation of several instant load “boxes” to allow a simple simulation to estimate the total energy use with each of the control methods.

[132] Table 1 below shows the hourly cash data that was created for both cities of Zebulon, NC, USA and Mumbai, India.Table -1.0 CASH DATA PER HOUR

[133] With this method, the analysis of reactivation energy use is more defined compared to the application of design data based on two or three design points, for all three control methods considered and defined below.

[134] a) Control option 1 - Fixed Reactivated Air Flow, Fixed Reactivation Inlet temperature, fixed rotor speed, variable processed flow;

[135] b) Control option 2 - Fixed Reactivated air flow, Fixed Reactivation Discharge temperature, fixed rotor speed, variable processed flow. (That is, for the purpose of the invention, considered as a baseline control option).

[136] c) Control option 3 - Fixed reactivation input temperature, variable reactivated air flow, variable rotor speed, variable processed flow through the wheel with the balance deviating from the wheel.

[137] Based on the hourly cash data and the aforementioned three control methods / options, option 3 based on the current invention, the energy used in thermal value / years for all three options was plotted and compared. The comparison is shown here below in Tables 2, 3, 4, 5 and 6. The amount of energy used after the use of cooling is also tabulated in Tables 5 and 6, which clearly show that, in addition to the reduction in energy use regeneration, there is a considerable overall reduction in the use of cooling energy as well.

[138] With reference now to Figure 9 (b), this graph shows the comparison of reactivation heat consumption (in thermal value / Year) for control options 1,2 and 3. The case study is for conditions of 15% and 30% RH considered for Zebulon and Mumbai. It is observed that in the case of control option 2 (baseline control option), in Zebulon for the 15% RH design the reactivation heat consumption is 11071 thermal value / year. If control option 1 is selected, this increases to 13059 thermal value / year. However, if control option 3 is selected, consumption is considerably reduced to 5747 thermal value / year. Tables 2, 3 and 4 provide complete data for the energy consumed as control options 1, 2 and 3 for a 15% design and for 30% RH in Mumbai and Zebulon.

Tabela 3 Dados de Consumo de Energia conforme a opção de controle 2

Tabela 4 Dados de Consumo de Energia conforme a opção de controle 3

Tabela 5 Sumário de Consumo de Energia conforme as opções de controle 1 ,2, 3 para os 30% RH 

Tabela 6 Sumário de Consumo de Energia conforme as opções de controle 1 ,2, 3 para os 15% RH Exemplo de Desenho

[139] Table 5 is a summary of the energy consumed in control option 1, 2 and 3 for a 30% RH design and Table 6 is a summary of energy consumption by control option 1,2 and 3 for a 30% RH design. Table 2 Energy Consumption Data according to control option 1

Table 3 Energy Consumption Data according to control option 2

Table 4 Energy Consumption Data according to control option 3

Table 5 Summary of Energy Consumption according to control options 1, 2, 3 for 30% RH

Table 6 Summary of Energy Consumption according to control options 1, 2, 3 for 15% RH Example of Drawing

[140] While initially the energy use analysis for the invention, by control option 1, was additionally remarked against the baseline of control option 2, it was additionally considered useful to complete the analysis using another commonly and currently used method of dehumidification control capability using control option 1.

[141] Accordingly, the resulting percentage of reduction in energy with the invention was compared across all three options using control option 2 as the baseline, in table 7, and using control option 1 as the baseline. based on table 8.

[142] With reference now to Figure 11 ©, this graph shows the percentage of savings with respect to heat regeneration using different control options. As shown, using control option 3, the savings percentage can be as high as 47%. However, if control option 1 is selected as another baseline, there is an additional increase in the savings percentage. This would then be a comparison between control option 1 and 3.

Tabela 8 Análise de Consumo de Energia

[143] Table 7 provides a detailed energy consumption comparison between Control Option 1, 2 and 3.Table 7 Energy Consumption Analysis

Table 8 Energy Consumption Analysis

[144] From the above, it is evident that this invention presents an innovative method and system with regard to the control capacity of a dehumidifier, providing significant energy savings when compared to known methods and technique.

[145] The system of the invention also incorporates several other advantages such as the design of the basic cabinet and opposite to the vacuum in such a way that the size of the reactivation sector can be selected from the variation of 12% to 45% of the total area of face of the desiccant rotor and adjusted during manufacture without any change in the design of the cabinet. Additionally, if desired, the design of the basic cabinet and opposite to the vacuum is such that the size of the reactivation sector can be manually adjusted in the field anywhere in the range of 66% to 150% of its original design value using hand tools to adapt to modified performance requirements. When the system is used with a purification sector with a concurrent air flow, the design of the basic and vacuum-opposed cabinet allows a purification sector size ranging between 2% and 25% of the rotor face area to be added without major changes to the design.

[146] Although the invention has been described with reference to specific embodiments, it should be understood by those individuals skilled in the art that various changes can be made without departing from the spirit and scope of the invention. For example, the numerous details set forth herein, for example, details relating to the configuration and operation of the presently preferred embodiment of the active desiccant module and hybrid systems, are provided to facilitate understanding of the invention and are not provided as limiting the scope of the invention . Accordingly the disclosure of the embodiments of the invention is intended to be illustrative of the scope of the invention and is not intended to be anything limiting.

Claims (21)

1. Method for controlling an active desiccant dehumidifier of the type comprising a housing having at least one desiccant wheel (1) having a process sector (2) with an air flow device and a reactivation sector (3) with a air flow (5); means (4) for turning the desiccant wheel (1) through the process (2) and reactivation (3) sectors; and means (10) for heating the reactivation air (3), the method comprising: a) modulating the air flow (6) through the process sector (2) to control the amount of dehumidification of the process air flow; and b) modulating the air flow (8) through the reactivation sector (3) as a function of the process air flow modulation (6); characterized by the additional step of c) modulating the speed of rotation of the desiccant wheel (1) as a function of the process air flow modulation (6). Method according to claim 1, characterized in that the modulation of the process air flow (6) (6) comprises ignoring and diverting (25) a portion of the process air flow (6) to the around the desiccant wheel (1) and / or comprises modulating a damper controlling the process air flow (6) (6) and / or simultaneously controlling the air flow (6) through the desiccant wheel (1) and the air flow bypassing and deflecting (25) the desiccant wheel (1) in such a way that the total air flow remains practically constant. Method according to claim 1, characterized in that the modulation of the process air flow (6) comprises varying the operational characteristics of the process air flow medium (6). 4. Method according to claim 1, characterized in that the minimum air flow through the process sector (2) is limited to a predetermined value. Method according to either of Claims 1 or 2, characterized in that the function of controlling the reactivation of the air flow modulation (8) and / or the function of controlling the rotation speed modulation of the desiccant wheel is a linear function. Method according to either of Claims 1 or 2, characterized in that the function of controlling the airflow modulation (8) of reactivation and / or the function of controlling the speed modulation of the desiccant wheel is an exponential function with the exponent between 0.5 and 2.0. 7. Method according to claim 1, characterized by the fact that the heated air temperature entering the reactivation sector (3) is maintained at a fixed value, preferably by modulating the heat input in the air heating reactivation means . 8. Method according to claim 1, characterized by the fact that the temperature of the reactivation air leaving the reactivation sector (3) is maintained at a fixed value by modulating the heat input in the air heating reactivation means . 9. Method according to claim 1, characterized by the fact that the source of reactivation of heated air is maintained at a fixed value and the temperature of reactivation of heated air is not controlled but variation is allowed, increasing as a reduced air flow and decreasing with a higher air flow. 10. Method according to claim 9, characterized by the fact that the heat source is activated whenever there is air flow through the reactivation sector (3). 11. Method according to claim 1, characterized by the fact that the modulation of the reactivation air flow (8) is achieved and achieved by modulating a damper in the reactivation air stream (8), and / or by varying the operational characteristics of the reactivation airflow means by ignoring and diverting a portion of the reactivation air around the desiccant wheel (1). 12. Method according to claim 1, characterized by the fact that the minimum air flow through the reactivation sector (3) is limited to a predetermined value. 13. Method according to claim 1, characterized in that the modulation of the rotation speed of the desiccant wheel (1) is carried out by varying the operational characteristics of the means of rotation of the desiccant wheel. 14. Method according to claim 1, characterized by the fact that the efficient rotation speed of the wheel (1) is achieved by intermittently operating the rotation means of the desiccant wheel in such a way that the percentage of time that the rotation means operates the desired control function is proportional. Method according to claim 1, characterized in that the minimum rotation speed of the desiccant wheel (1) is limited to a predetermined value. 16. Method according to claim 1, characterized by the fact that the function of controlling the rotation speed modulation of the desiccant wheel (1) is a linear function of the reactivation air flow (8). 17. Method according to claim 1, characterized by the fact that the control function of the speed modulation of the desiccant wheel (1) is an exponential function of the reactivation air flow, with the exponent between 0.5 and 2.0. 18. Method according to claim 1, characterized by the fact that the active desiccant dehumidifier also contains an intermediate "purification" sector (11) between the reactivation sector and the process sector to pre-treat a portion of the reactivation air , the air flow (12) passing through the purification sector is preferably modulated in a direct proportion to the reactivation air flow (8). 19. Method according to claim 1, characterized by the fact that one or more purification sectors (11) are provided in order to act as a buffer between the process sector (2) and the reactivation sector (3), and in which the one or more purification sectors (11) intermediates comprise one or more pairs arranged to act as a buffer between the process sector (2) and the reactivation sector (3) and provided with the means to circulate a flow of air through them. 20. Active desiccant dehumidifying system comprising a housing containing at least one desiccant wheel (1) having a process sector (2) with air flow means; a reactivation sector (3) with air flow means (5); u means (4) of rotation of the desiccant wheel through the reactivation process and sectors; and air heating reactivation means (10); and a control system, characterized by the fact that the control system is operated according to the method as claimed here in any one of claims 1 to 19 to improve the operational efficiency of the dehumidifier under partial load conditions. 21. The active desiccant dehumidifying system as claimed herein in claim 20 in which one or more purification sectors act as a buffer between the process sector and the reactivation sector.

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