JP2012525954A - Desiccant unit control system and method - Google Patents

Abstract

  The present invention provides a method for controlling an active desiccant dehumidifier comprising: a. Adjusting the air flow through the process zone to control the amount of dehumidification; b. Adjusting the air flow through the reactivation zone as a function of adjusting the process air flow; c. Adjusting the rotational speed of the desiccant wheel as a function of adjusting the process air flow; and a method of controlling an active desiccant dehumidifier. The present invention also provides a system for the method.

Description

  The present invention generally relates to heating, ventilating, and air-conditioning or HVAC systems and methods, and more particularly, to dry process systems and methods, and more particularly to thermal activation. Relates to an air conditioning or dehumidification or drying system that incorporates a desiccant wheel. The present invention also provides an improved method for storing / reducing energy consumed during use of such a system using a desiccant wheel.

  Desiccant wheels and energy recovery wheels are two types of wheels that are used in HVAC or for air conditioning process air. The desiccant wheel is used to transfer moisture from one air stream to another. There are two characteristic types of desiccant wheels: an “active” desiccant wheel and a “passive” desiccant wheel.

  An “active” desiccant wheel uses an external heat source to heat one of the air streams to reactivate / regenerate a portion of the wheel. “Active” desiccant wheels are commonly used in industrial applications that require large amounts of moisture removal, but are also increasingly used in commercial HVAC applications. Examples of such “active” desiccant wheels and systems are described in several patent specifications such as US Pat. Nos. 6,311,511, 5,551,245, 5,816,065. It is disclosed in the specification.

  A “passive” desiccant wheel does not use an external heat source and moves moisture between air streams by relying on the relative humidity difference of two or more air streams. Examples of “passive” desiccant wheel systems and uses are disclosed in US Pat. Nos. 6,237,354 and 6,199,388.

  Thermally activated desiccant wheel systems use a considerable amount of thermal energy (steam, electricity, gas, etc.) to reactivate or regenerate the wheel, so it can be reactivated using various control methods Various methods have been employed in the past with the aim of minimizing the use of energy and / or minimizing the use of additional components. Methods for transferring heat energy from process air to reactivated inlet air or transferring heat from a reactivated air outlet to a reactivated air inlet, such as a heat recovery device, add excessive cost. invited.

  Dehumidification is the process of removing moisture from the air. There are several well-known air dehumidification methods. However, two commonly used methods are those that utilize cooling and desiccants. In the case of dehumidification utilizing cooling, moisture is condensed on the cooling coil, thereby removing the moisture from the air flow that has passed through the cooling coil. In the case of dehumidification using a desiccant, the process employed is one of absorption or adsorption. In the case of absorption, liquid or solid desiccants, typically halide salts or halide solutions are used. In the case of adsorption, a solid desiccant such as silica gel, activated alumina, molecular sieve or the like is used.

  The desiccant system based on the desiccant is a multi-column circulation type or a continuous rotation type. The air to be dried is commonly referred to as process air, and the air used to regenerate the desiccant is referred to as regeneration air or reactivation air.

  Cooling-based dehumidification systems actually limit the moisture that can be removed. This is because in order to achieve dew point humidity below freezing, frost forms on the cooling coil, which makes the system more complex and often requires reheating.

  On the other hand, desiccant dehumidifier systems work independently of the air dew point and can therefore achieve the extremely low dew point humidity required for many industrial applications. Well-known common uses are in the pharmaceutical field for the production of pharmaceuticals and in the food processing field. These fields require lower relative or dew point humidity than can be achieved technically or economically by cooling alone.

  Hybrid systems that use both a cooling unit and a desiccant unit are also commonly used to help reduce energy usage and enable simple and reliable operation of the entire dehumidification system.

  Compared to refrigerated dehumidification units, desiccant dehumidifiers typically use more thermal energy, primarily for regeneration or reactivation of the desiccant. Thus, over the years, several developments to minimize energy usage in the physical form and control strategy of desiccant equipment to control the capacity and energy of desiccant dehumidifier systems Has been done.

  A desiccant dehumidifier unit for dehumidifying / drying air at atmospheric pressure is generally rotary today. In this case, the desiccant is contained in a rotating bed (or wheel). The wheels, typically two compartments (or zones), one for the process and the other for regeneration, move continuously or intermittently. In the process area, the air to be dehumidified (commonly referred to as process air) is passed through the wheel and dried by contact with the desiccant. In the regeneration zone, air is generally introduced from the atmosphere, passed through a heat source that raises the temperature of the reactivated air, and then also called a reactivation zone or regeneration zone that heats the wheel and drives out water. You can pass the rest. Typically, the process area is 50-80% of the total bed / wheel area, but may be larger or smaller, with the remainder being the reactivation area.

  In many cases, another zone is added between the process zone and the regeneration zone, which is called the purge zone. A third air stream (generally purge air) is passed through the purge zone and is used as part of the regeneration air. The incorporation of the purge zone helps to recover any residual heat from the rotating wheel before it enters the process zone, thereby reducing the total energy required for regeneration and reducing the total amount of moisture removed by the wheel. Improve.

  For a typical desiccant dehumidifier unit, the process air flow and reactivation flow are generally fixed and set or adjusted by manual or automatic dampers (doors).

  In the design of a typical dehumidifier system for controlling humidity within a given space, the air flow required to control the space temperature is greater than the amount of dehumidified air required to control the space humidity. Often there are many. In such cases, a portion of the process air is typically diverted around the dehumidifier unit and then combined with the air exiting the dehumidifier unit, and the combined air is then cooled ( Or heated) and then fed into the control space.

  Since desiccant dehumidifier systems inherently use a large amount of heat energy for regeneration, efforts have been made to find methods and means for reducing the amount of heat used by the system.

  One typical well-known system and method used is to control the heated temperature of the regeneration air before it enters the reactivation zone.

  Another well-known method is to control the amount of regenerative heat introduced by controlling the air temperature exiting the reactivation zone.

  Depending on the type and amount of relative humidity and dew point control, the control strategy can employ dehumidifier start / stop once the space or air conditions are met. Similarly, automatic dampers can be used instead to meet operating and design requirements by continuously changing the amount of air that bypasses the dehumidifier unit.

  Correlation between process area and reactivation area area, wheel rotation speed and relative flow rate and speed of process air flow and reactivation air flow through the two areas has been And, in the United States, resulted in a robust mathematical modeling tool that is typically used in a finite form for the design, selection, and incorporation of desiccant wheels in a dehumidifier unit. Such tools are commonly used to optimize the dehumidification system at the design and construction stage.

  One such study and development of a mathematical model is described in detail in the document “Modeling of Rotary Desiccant Wheels” (Harshe, Utikar, Ranade and Pahwa, 2005).

  For rotary desiccant dehumidifier units, use such mathematical modeling tools to select a specific percentage of the reactivation area, as well as process and reactivation flow, and a given bed rotation speed Thus, the facility performance at the design and construction stage can be optimized. In such a case, the dehumidifier capacity is controlled by using the control force under partial load and instantaneously changing moisture load. Some of these strategies are well documented, for example in the Bry Air design manual as well as the Munter design manual.

  During the operation of such a dehumidifier system, the use of traditional well-known dehumidifier capacity control methods limits the reduction in renewable energy usage.

  All of the above do not achieve the maximum or energy reduction that is desirable or fairly balanced in the event of instantaneous moisture load changes.

  Below are some examples of prior art implemented to reduce regenerative energy and / or adjust desiccant wheel speed while optimizing dehumidifier capacity.

  US Pat. No. 4,546,442 is based on a microcomputer for a fixed bed, multi-bed desiccant air dryer commonly used to dehumidify compressed air or other compressed gases. A programmable control system is taught. The control system monitors the moisture level in the desiccant to determine if a regeneration cycle is necessary, and also monitors the complete decompression and reheating of the regeneration bed, and also analyzes and indicates valve failure. Used to do. The application of this invention is limited to compressed air systems.

  U.S. Pat. No. 4,729,774 teaches profile analysis of the temperature of air in the reactivation zone to improve dehumidifier performance.

  U.S. Pat. No. 4,926,618 teaches a desiccant unit having controllable reactivated air recirculation means and variable wheel speed means. Process air humidity is controlled by a main controller that adjusts wheel speed, reactivation air recirculation speed, and reactivation heat introduction. The process air flow and reactivation air flow through the wheel are fixed and the reactivation air heater is controlled to maintain a constant reactivation air temperature exiting the wheel.

  US Pat. No. 5,148,374 describes a multi-wheel adsorbent mass energy transfer system by optimizing a calculated mass transfer rate ratio and a measure of system effectiveness that is not affected by long system time constants. Systems and methods for real-time computer control are taught. The method detects a predetermined parameter set selected from a group such as a wheel inlet temperature and a wheel outlet temperature at a predetermined interval, thereby detecting a predetermined one of a group of control means including control of a fluid flow temperature. Depends on sending a control signal to The purpose of this control method is to improve the response of the controlled device to rapid load changes without causing unstable operation of the device and the resulting variation in controlled variables.

  In the case of the regeneration control apparatus and method for a desiccant dehumidification system taught in US Pat. No. 5,688,305, the reactivation air flow is controlled to maintain a constant reactivation exhaust temperature. And the reactivation air inlet temperature is controlled at a fixed value. The desiccant residence time in reactivation is also controlled to be inversely proportional to the reactivation air flow. The purpose of this document is to reduce the desiccant overproduction under partial load conditions and thus improve the operating efficiency of the desiccant dehumidifier. This cited application uses a dehumidified recirculating air flow to dry granular material in a bottle or hopper when the granular material flow through the bottle occurs batchwise or at a variable rate. belongs to.

  A system and method for controlling temperature and humidity levels in a control space, as taught in US Pat. No. 6,199,388, mainly includes an enthalpy wheel, also known as an energy recovery wheel, a cooling coil, Applies to combinations with “passive” desiccant dehumidification wheels that do not employ external heat or energy introduction for reactivation. The above specification further teaches means for changing the performance of a “passive” desiccant wheel through changes in rotational speed in response to a perceivable potential load in the control space. Control of the desiccant wheel speed has been discussed, and the intent is not to optimize the energy efficiency of the dehumidification process, but to control the dehumidification capacity of the “passive” wheel. The above specification does not teach the use of process air surfaces and bypass dampers to control the capacity of the dehumidifying wheel. Both supply (process) and exhaust (reactivation) airflow are maintained at a constant value throughout all load conditions.

  US Pat. No. 6,355,091 teaches a unitary ventilation and dehumidification system for supplying external ventilation air to an air-conditioned space. This unit is rotated at a low speed to achieve a greater amount of dehumidification and at a higher speed to achieve a greater amount of heat recovery. By applying heat to the exhaust air space upstream of the desiccant wheel, its dehumidification performance can be improved and frost formation during winter operation can be prevented. Both the supply air flow rate and the exhaust air flow rate are fixed, no bypass damper is used, and the rotor speed adjustment is for selecting the operating mode, not for efficiency improvement.

  US Pat. No. 6,767,390 for controlling the performance of a multi-bed fixed bed desiccant dryer for application in compressed air and compressed gas and for supplying the required dew point gas Methods are taught to optimize regeneration and purge cycles. A contemplated field of application is compressed air for use in equipment.

  U.S. Pat. No. 7,017,356 teaches an HVAC system for cooling and dehumidifying a comfortably conditioned space containing a desiccant wheel in a passive dehumidifier. In this device, the speed of the wheel varies with the air flow rate, and the wheel is operated for at least a predetermined time during start-up to prevent inundation of moist air into the conditioned space. This patent also teaches the use of passively sensitive recovery devices and cooling coils to pre-condition external air before mixing with air returned from the conditioned space.

  U.S. Pat. No. 7,101,414 uses an adsorbent bed system that includes material rotated through multiple zones in addition to traditional process and regeneration zones for process fluid flow. A method of reducing the concentration of adsorbent is taught. In this method, one or more pairs of independent recirculating fluid streams other than the process stream and the regeneration stream are used to isolate the process stream and the regeneration stream from each other. The purpose of sequestration may be to prevent mutual leakage of air between the process zone and the reactivation zone, penetration of adsorbate into the adsorption bed, or condensation or frost formation on the adsorption bed.

  US Pat. No. 7,338,548 teaches the use of an apparatus and control method for air conditioning the humidity and temperature in the process air stream from a desiccant dehumidifier. Here, a part of the process exhaust air is used to preheat the regeneration air by using an air-air heat exchanger. The field of use of the invention is in the improvement of structure drying and water damage.

  U.S. Pat. No. 7,389,646 is an earlier divisional application and is similar to U.S. Pat. No. 7,017,356 by the same inventor. It is also intended to cool and dehumidify a comfortably conditioned space and teaches an HVAC system that includes a passive desiccant wheel. The wheel speed varies with the air flow rate and depends on the wheel being operated for at least a predetermined time at start-up, and the system's ability to dehumidify air by employing a heat recovery system upstream of the wheel To increase.

  Most prior art control strategies have only been partially successful in limiting and reducing the amount of reactivation energy used, which is commensurate with the reduced moisture load under partial load conditions. Can not be removes.

  Also, during application using the desiccant wheel and system, the instantaneous moisture load in this air usually varies considerably when fresh air treatment is required, and the space in which moisture is to be controlled. Internal internal potential loads must be controlled based on outdoor temperature and humidity changes, and product and containment load.

  Not only does it significantly reduce the use of reactivation energy and respond to changes in dynamic / instantaneous moisture load, but at the same time reduce the energy usage at the wheel during such moisture load changes. There is a need for a control method that can also be optimized, together with the necessary relevant components.

  The general goal and objective of the present invention is to significantly reduce the amount of accumulated energy used in the current operation of a heat activated desiccant dehumidification system. Energy reduction is generally by adjusting the energy consumed by the desiccant unit in response to moisture changes in the ambient air and / or moisture loads in the control space and / or moisture changes in the process stream. Achieved. Such instantaneous moisture changes, and the resulting moisture load, demands the need to control the capacity of the dehumidification system.

  As the instantaneous moisture load fluctuates and changes constantly, this dehumidification capability control is achieved primarily by controlling the air flow through the wheel process area and the optimal / minimum energy usage within the dehumidifier. The amount controls the air flow through the reactivation zone and keeps the reactivation air temperature constant, while simultaneously and proportionally adjusting the wheel rotation speed to achieve optimal energy efficiency Is achieved by doing

  Although there are established methods for controlling the capacity of a dehumidifier system, the present invention provides a new method that significantly reduces energy usage at part loads compared to previously known methods. To reduce.

The objects of the present invention are achieved by a system and method for controlling the dehumidifying capacity, including the following a) to f).
a) controlling the air flow through the process area of the rotor, controlling a constant reactivation inflow temperature, controlling the reactivation air as a function of the process air flow, and also the rotor speed as a function of the process air flow To control as. And the control function is based on the ratio of the instantaneous process air flow and the design process air flow, all the control functions are exponential functions, the exponents being any numerical value in the range of 0.5-2.0, The index for each variable being controlled is not necessarily equal.
b) by controlling the air flow through the process area of the rotor and using a two-position steam valve on the reactivated air heating coil, for example using constant pressure steam as a reactivation heat source Controlling the reactivation heat source temperature and controlling the reactivation air as a function of the process air flow and also controlling the rotor speed as a function of the process air flow. And the control function is based on the ratio of the instantaneous process air flow and the design process air flow, all the control functions are exponential functions, the exponents being any numerical value in the range of 0.5-2.0, The index for each variable being controlled is not necessarily equal.
c) controlling the air flow through the reactivation zone of the rotor and controlling the constant reactivation inflow temperature, while also maintaining a constant air flow through the process zone, and also controlling the rotor speed to the reactivated air Control as a function of flow. And the control function is based on the ratio of the instantaneous reactivation air flow and the design process air flow, all the control functions are exponential functions, and the exponents are arbitrary numerical values in the range of 0.5 to 2.0. is there.
d) Controlling the air flow through the reactivation zone of the rotor while maintaining a constant air flow through the process zone, and using, for example, constant pressure steam as a reactivation heat source, Controlling a constant reactivation heat source temperature by using a two position steam valve on the coil, and also controlling the rotor speed as a function of the reactivation air flow. The control function is based on the ratio of the instantaneous process air flow to the design process air flow, the control function is an exponential function, and the exponent is an arbitrary numerical value in the range of 0.5 to 2.0.
e) controlling the air flow through the process area of the rotor and controlling a constant reactivation discharge temperature and controlling the reactivation air as a function of the process air flow and also controlling the rotor speed to the process air flow Control as a function of. And the control function is based on the ratio of the instantaneous process air flow and the design process air flow, all the control functions are exponential functions, the exponents being any numerical value in the range of 0.5-2.0, The index for each variable being controlled is not necessarily equal.
f) Controlling the air flow through the reactivation zone of the rotor and controlling the constant reactivation discharge temperature, while also maintaining a constant air flow through the process zone, and also reactivating the rotor speed Control as a function of flow. The control function is based on the ratio between the instantaneous reactivation air flow and the design reactivation air flow, the control function is an exponential function, and the exponent is an arbitrary numerical value in the range of 0.5 to 2.0. It is.

  Another object of the present invention is to provide a system and method for controlling the dehumidification capacity according to the above four control scenarios, and in addition, to be placed continuously between the reactivation zone and the process zone. Incorporating a purge zone into the process zone and the purge zone at the same time, and controlling the purge air flow as a function of the reactivation air flow, the control function includes the instantaneous reactivation air flow and the design reactivation. Based on the ratio to the activated air flow, the control functions are all exponential functions, which are arbitrary numerical values in the range of 0.5 to 2.0.

  Another object of the present invention is to provide a system and method for controlling the dehumidification capacity according to the above four control scenarios, and in addition, at least a pair to be disposed between the process zone and the reactivation zone. And each section has means for recirculating air therethrough according to U.S. Pat. No. 7,101,414 (an improvement is the purging air as a function of rotor speed). And the function is based on the ratio of the instantaneous rotor speed to the design rotor speed, and the function is an exponential function, the index being between 0.5 and 2.0 Any numerical value in the range.

  In the case of the above embodiments, the size of the reactivation area can be easily adjusted at the time of manufacture or after installation in the field to further optimize the design for any given dehumidification system application. As such, there is a further objective of providing design requirements for the base cabinet and plenum. Optimization is achieved by selecting a minimum reactivation energy usage at design conditions and / or a relative size of the process area and reactivation area that allows for the lowest process exhaust humidity.

  An “active” desiccant so that one or more of the above objects of the present invention fully utilize the dynamic behavior of the desiccant-rotor under varying partial load conditions or process flow conditions • To provide a heat activated dehumidification system employing a rotor.

Accordingly, the present invention is an apparatus for dehumidifying air supplied to a closed space or a process bin (bin) or a drying bin, comprising a housing, an interior space, a rotatable desiccant wheel, a heat source, Including at least one bypass damper;
(A) the housing defines an internal space;
(B) The internal space is separated by a separator into a supply part for containing the supply air stream and a regeneration part for containing the regeneration air stream, the supply part for receiving the supply air And an outlet for supplying air to the enclosed space, the regeneration portion having an inlet for receiving the regeneration air and an outlet for discharging the regeneration air;
(C) The rotatable desiccant wheel is arranged such that part of the wheel extends into the supply part and part of the wheel extends into the regeneration part, the wheel dehumidifies the supply air flow And rotatable through the supply air stream and the regeneration air stream;
(D) a heat source is provided to heat the regeneration air stream to regenerate the desiccant wheel as it is rotated by the regeneration air stream; and (f) at least one bypass damper comprises: Provided between the inlet and outlet of the supply section to control the amount of supply air through the desiccant wheel by selectively bypassing the desiccant wheel;
Providing equipment.

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

  In another embodiment, the regeneration portion is equipped with a fan to move the regeneration air flow.

  In another embodiment, ducts and control means are provided to allow recirculation of a portion of the regeneration air.

  In the preferred embodiment, dampers and / or speed adjusting means are provided to allow adjustment of the air flow through the regeneration section.

  In another embodiment, the supply portion comprises a fan for moving the supply air flow, a cooling coil is disposed in the supply air flow, and the rotatable desiccant wheel is downstream of the cooling coil. Has been placed.

  In another embodiment, the rotational speed of the desiccant wheel is controlled to control the amount of moisture removed from the supply air stream and / or to minimize the amount of heat transferred to the supply air stream. A speed regulation mechanism is provided to vary.

  In a further embodiment, the heat source is a direct combustion gas burner.

  In a further embodiment, the heat source is electricity used in a resistance heater.

  In a further embodiment, the heat source is a constant temperature source, such as steam or hot water.

  In a further embodiment, the heat source is a source of recovered heat from a cooling condenser or recovered process from another process.

  In a further embodiment, the heat source is a combination of two or more of the heat sources used in succession.

  In a preferred embodiment, a heat adjustment means is provided for the heat source to adjust the temperature of the regeneration air stream.

  In another embodiment of the invention, adjustment means are provided for the bypass damper to adjust the amount of supply air that passes through the desiccant wheel.

  In another embodiment, the desiccant wheel is sized to process a portion of the required air flow that has been processed by the air conditioning system.

  In another embodiment, means are provided for cooling and / or heating the supply air after it has passed through the dehumidifier and before it is supplied to the conditioned space.

  In another embodiment, the system includes a compartment that houses the condenser, and the device connects the regenerative inflow air to the condenser housing housing to allow the regeneration inflow air to be preheated by the condenser. A duct or opening is provided.

The present invention is also a method for controlling the temperature and humidity of an air conditioned space or process bin or drying bin comprising:
(A) providing an air conditioning system in communication with the air conditioned space;
(B) an active desiccant wheel system defining an interior space;
An internal space, the internal space being separated by a separator into a supply part for containing the supply air stream and a regeneration part for containing and containing the regeneration air stream, the supply part being a closed space or An inlet for receiving supply air from the air conditioning system and an outlet for supplying air to the air conditioning system or the enclosed space are provided, and the regeneration portion includes an inlet for receiving the regeneration air, and the regeneration air. An internal space provided with an outlet for discharging;
A rotatable desiccant wheel, with a portion of the wheel extending into the supply portion and a portion of the wheel extending into the regeneration portion, the wheel supplying and regenerating the supply air flow to dehumidify the supply air flow A desiccant wheel that is rotatable by air flow;
A heat source that heats the regeneration air stream to regenerate the desiccant wheel as it is rotated by the regeneration air stream;
At least one bypass damper between the inlet and outlet of the supply section to control the amount of supply air through the desiccant wheel by selectively bypassing the desiccant wheel;
Preparing steps;
(C) connecting the active desiccant wheel system to the air conditioning system;
(D) cooling and / or heating the supply air stream by allowing the supply air stream to pass through the air conditioning system;
(E) Dehumidify the supply air flow by allowing the supply air flow to pass through the active desiccant wheel system while rotating the wheel with the supply air flow and the regenerative air flow, thereby reducing the humidity between the air flows. Exchanging minutes and / or heat; and (f) supplying air from the air conditioning system to the conditioned space;
Providing a method.

  These and other embodiments and advantages of the present invention will become more fully apparent from the following description and the accompanying drawings.

FIG. 1 (a) is a schematic diagram showing a typical heat activated desiccant dehumidifier unit with a typical / classical 25% regeneration zone along with a regeneration blower. FIG. 1 (b) is a schematic diagram showing a typical heat activated desiccant dehumidifier unit with a typical / classical 25% regeneration zone along with a regeneration blower. FIG. 2 (a) shows a typical heat activated desiccant dehumidifier unit with a regeneration blower, with a typical / classical 25% regeneration zone, and also includes a purge zone. It is the schematic shown in a state. FIG. 2 (b) shows a typical heat activated desiccant dehumidifier unit with a regeneration blower, with a typical / classical 25% regeneration zone, and also includes a purge zone. It is the schematic shown in a state. FIG. 3 (a) shows a typical heat activated desiccant dehumidifier unit with a typical / classical 25% regeneration zone, along with a regeneration blower, and a pair of purge zones. It is the schematic shown in the state containing also. FIG. 3 (b) shows a typical heat-activated desiccant dehumidifier unit with a regeneration blower, with a typical / classical 25% regeneration zone, and a pair of purge zones. It is the schematic shown in the state containing also. FIG. 4 (a) shows a typical heat activated desiccant dehumidifier unit with a typical / classical 25% regeneration zone, along with a regeneration blower, and an additional two pairs. It is the schematic shown in the state also including the purge area of. FIG. 4 (b) shows a typical heat activated desiccant dehumidifier unit with a regeneration blower, with a typical / classical 25% regeneration zone, and an additional two pairs. It is the schematic shown in the state also including the purge area of. FIG. 5 (a) is a schematic diagram illustrating a typical prior art dehumidification system and method. FIG. 5 (b) is a schematic diagram illustrating a typical prior art dehumidification system and method. FIG. 6 (a) is also a schematic diagram illustrating a typical prior art product drying system and method. FIG. 6 (b) is also a schematic diagram illustrating a typical prior art product drying system and method. FIG. 7 (a) is also a schematic diagram showing a typical prior art product drying system and method including a purge zone. FIG. 7 (b) is also a schematic diagram showing a typical prior art product drying system and method including a purge zone. FIG. 8 (a) is a schematic diagram illustrating an embodiment of the system and method of the present invention. FIG. 8 (b) is a schematic diagram illustrating an embodiment of the system and method of the present invention. FIG. 8 (c) is a schematic diagram illustrating an embodiment of the system and method of the present invention. FIG. 8 (d) is a schematic diagram illustrating an embodiment of the system and method of the present invention. FIG. 8 (e) is a schematic diagram illustrating an embodiment of the system and method of the present invention. FIG. 9 is a schematic diagram illustrating one embodiment of the present invention as a flowchart of a process drying / dehumidification system. FIG. 10 (a) is a schematic diagram illustrating one embodiment of the present invention as a diagram of a process drying / dehumidification system. FIG. 10 (b) is a schematic diagram illustrating one embodiment of the present invention as a diagram of a process drying / dehumidification system. FIG. 11A is a graph showing the energy saving of the present invention in comparison with the prior art. FIG. 11B is a graph showing the energy saving of the present invention in comparison with the prior art. FIG. 11 (c) is a graph showing the energy saving of the present invention in comparison with the prior art. FIG. 12 is a schematic diagram illustrating one embodiment of the system and method of the present invention including several HVAC components that can be enabled / used or disabled / disabled. is there.

  The present invention is described below with reference to the accompanying drawings, which illustrate certain specific embodiments of the invention. Changes and modifications can be made without departing from the spirit and scope of the invention.

  FIG. 1A is a flowchart of a typical desiccant dehumidifier. As mentioned above, a typical rotary desiccant bed / wheel 1 has a process zone 2 and a regeneration or reactivation zone 3. A dehumidifier incorporating such a desiccant bed / wheel 1 has a process stream 6 as well as a regeneration stream 8. The regenerative stream rises in temperature by passing through the heat source 10 before entering the regenerated portion of the bed 3. Regenerative air leaving the reactivation zone 3 of the rotating bed is exhausted by a blower 5 commonly referred to as a reactivation blower 5 (9). The desiccant bed / wheel 1 is rotated by the bed drive 4 through the reactivation zone and the process zone.

  FIG. 1 (b) shows a typical area division of the wheel 1. Process area 2 is typically 75% of the total bed area, as shown, and in practice may generally be 50-80%, but is designed to be smaller or larger You can also. The remaining area of the desiccant bed is shown as reactivation zone 3, which may be 20-50%, but can also be designed to be smaller or larger.

  FIG. 2A shows a state where another area called a purge area 11 is added. The purge area is generally 5-40% of the total bed area, and the remainder is divided into process area 2 and reactivation area 3. When the bed is rotated from the reactivation zone 3 to the process zone 2, the bed is still hot. It is well known that especially in the case of silica gel type, the hot part of the bed begins to function when it cools down (i.e. moisture removal). Thus, certain bed portions are substantially inert in performing the dehumidifying function while still at high temperatures. This segment or portion of the bed is often delimited and formed as a purge area 11. Air 12 is passed through this area 11. Here the bed is hot and the air 13 is preheated before passing through the reactivation zone 3. This reduces the amount of reactivation energy required and cools the bed portion before it enters the process zone 2. Thereby, the dehumidification performance through the process area 2 is improved. In addition, less heat is given to the process air. This is because it is cooler when the bed enters the process area.

  FIG. 2 (b) shows the desiccant bed / wheel 1 viewed from another angle. Here, various areas are shown. These area areas are shown to be typical, but can vary as described above.

  FIG. 3 (a) shows another flowchart of the rotary desiccant bed / wheel 1 system. Here, a pair of zones (11a, 12) is added. In such a configuration, a separate fan 15 typically causes a given air flow to circulate through these sections in a closed loop. The recirculated air stream acts as a buffer between the process air stream and the reactivated air stream to capture air leaks or moisture diffusion between the process air stream and the reactivated air stream, thus Improve performance. In some cases, the recirculated air flow may transfer heat between zones, similar to the purge zones shown in FIG. 2, further improving system performance. It should be noted that the air flow forming the recirculation loop described in all drawings may be in any direction, the most advantageous direction depending on the details of the particular application. FIG. 3 (b) shows the desiccant bed / wheel 1 viewed from another angle. Here, various areas are shown. These area areas are shown to be typical, but can vary as clearly described above.

  FIG. 4 (a) is a flowchart of the rotary desiccant bed / wheel 1 where two or more purge zones 11a, 12, 17, 18 have been added. In such a configuration, a separate fan 15, 21 typically causes a given air flow rate 13, 19 to circulate in a closed loop through these sections.

  FIG. 4 (b) shows the desiccant bed / wheel 1 viewed from another angle. Here, various areas are shown. These area areas are shown to be typical, but can vary as clearly described above.

  FIGS. 5 (a) and 5 (b) show a typical traditional dehumidifier system for controlling the space 27. In this system, for example, the need for cooling to the space to be dehumidified requires that a predetermined amount of the total supply air 26 be taken up by the cooling unit or cooling coil 24 and supplied to the control space. . More air flow may be required to meet the cooling needs of the space than is necessary to be passed through the desiccant wheel to meet the need for space dehumidification. To accomplish this, a portion of the air is passed through the dehumidifier and the remainder is diverted (25) to form a total supply air flow through the cooling coil and supply it to the room. It is common. It is often necessary to supply fresh air 31 to meet the requirements of space ventilation / pressurization. Fresh air is generally introduced at the inlet of the dehumidifier and is combined with return air 28 from the control space. Before the fresh air is combined with the return air, it may be advantageous to heat / cool the fresh air using air heating / cooling means 22 and 23 as shown. In this exemplary flowchart / schematic diagram, a damper is used for the controlled flow of air. The fresh air flow is controlled by a damper 35. The bypass damper 32 is used to control the flow that needs to bypass the desiccant dehumidifier unit. The entire supply air flow is controlled by a damper 33 which is usually arranged after the supply air flow. Each of these dampers can be adjusted manually or automatically using actuators and appropriate control devices.

  The regenerative flow is also generally controlled by a damper placed after the reactivation fan 5. The regenerative heat source 10 can be reactivated to electricity, steam, gas or oil burner, hot fluid such as hot water, heat of the cooling condenser, recovered heat from another process, or temperature required for the application. It can be any combination of these that can heat the air. The reactivation heat energy introduction is regulated by the thermostat 30. The thermostat is generally placed in front of the desiccant bed. This thermostat 36 may be placed after the desiccant bed in the reactivation “out” section, as shown in FIG. 5b. In some cases, this alternative arrangement would reduce annual reactivation heat usage compared to placing an automatic temperature controller in front of the desiccant rotor.

  In both the dehumidifier system and the reactivation heat introduction control method described above, the control strategy currently in common use is that the relative humidity or moisture level of a given space, or process air, or supply air is “filled”. When the humidity is satisfied, the reactivation air flow, the bed rotation, and the reactivation heat introduction are stopped. This is commonly referred to as “on / off” control. In the case of another well-known method, generally used with fixed temperature heat sources such as steam or hot water, the unit's dehumidification capacity is adjusted by adjusting the reactivated air flow.

  FIG. 6 (a) shows a typical dehumidifier system used for drying applications. In this system, the dehumidified air 7 is heated through a heating source 22 according to the material requirements in the drying bottle 37. Moisture is adsorbed by passing return air 28 carrying moisture from the product through cooling coil 23 and through desiccant wheel / bed 1.

  The regeneration air stream 8 is provided by a reactivation blower 5. The heat source 10 is used to raise the temperature based on the specific design of the unit. The reactivation inflow temperature is controlled via a thermostat.

  FIG. 6 (b) shows the desiccant bed / wheel viewed from a different angle. Process area 2 is typically 75% of the total bed area, as shown, and in practice may generally be 50-80%, but is designed to be smaller or larger You can also. The remaining area of the desiccant bed is shown as reactivation zone 3, which may be 20-50%, but can also be designed to be smaller or larger.

  FIG. 7 (a) shows a typical dehumidification system for drying applications. This is similar to the system described in FIGS. 6 (a) and 6 (b) except that a purge zone 11 is added. This purge zone may be 5-40% of the total bed area. The purpose of using the purge zone has already been described previously.

  FIG. 7 (b) shows the desiccant bed / wheel 1 viewed from another angle. Here, various areas are shown. These area areas are shown to be typical, but can vary as described above.

  FIG. 8 (a) shows a typical spatial dehumidification system. In this system, an “internal” bypass 39 is interconnected with the process air flow 6 through a face bypass damper 40. Based on the humidity measured in the design space 27, and with instantaneous and changing loads, the face bypass damper 40 regulates the air flow through the wheel while diverting the rest. When it is necessary to supply fresh air 31 due to space design needs, fresh air is generally introduced at the dehumidifier inlet and combined with air 28 returning from the design space 27. Depending on the application, it may be advantageous to heat or cool the fresh air before it mixes with the return air.

  The air exiting from the outlet of the dehumidifier 38 can be mixed with the return air 28 and supplied to the design space 27 as supply air 26 before passing through the cooling coil 24 and the filters 44 and 45.

  The reactivated air stream 8 passes through a heat source 10, which raises the air temperature depending on the specific design of the unit. The thermostat 30 controls the temperature with respect to the set point. In order to control the reactivation air flow, the reactivation blower 5 is continuously variable in speed and has a suitable design according to the purpose. In order to obtain optimum performance, the rotor speed is also varied by the continuously variable speed bed drive 4.

  FIG. 8B schematically shows an example of a typical spatial dehumidification system. This is similar to the example of FIG. 8 (a) except that a purge zone 11 is added in the desiccant bed / wheel. This purge zone may be 5-40% of the total bed area. The remainder is divided into a process area 2 and a reactivation area 3. Air 12 is passed through this area 11. Here, the bed is hot, so that the air 13 is preheated before passing through the reactivation zone 3. This reduces the amount of reactivation energy required and cools the bed portion before it enters the process zone 2. Thereby, the dehumidification performance through the process area 2 is improved. In addition, less heat is given to the process air. This is because it is cooler when the bed enters the process area.

  The air exiting from the outlet of the dehumidifier 38 can be mixed with the return air 28 and supplied to the design space 27 as supply air 26 before passing through the cooling coil 24 and the filters 44 and 45.

  The reactivated air stream 8 passes through a heat source 10, which raises the air temperature depending on the specific design of the unit. The thermostat 30 controls the temperature with respect to the set point. In order to control the reactivation air flow, the reactivation blower 5 is continuously variable in speed and has a suitable design according to the purpose. In order to obtain optimum performance, the rotor speed is also varied by the continuously variable speed bed drive 4.

  FIG. 8 (c) schematically shows an example of a typical spatial dehumidification system. This is similar to the example of FIG. 8 (a) except that the purge zones 11a, 12 are provided in the desiccant bed / wheel. In such a configuration, a separate fan 15 is typically used to circulate the air in the areas 11a, 12 in a closed loop. The heat emanating from within the wheel section 12 following the reactivation zone can be “preheated” in the zone 11a following the process zone by picking up and sending it forward by the air flow indicated at 13. .

  The mixed air 38 leaving the dehumidifier can be mixed with the return air 28 and then passed through a cooling coil 24 for cooling the supply air 26 as needed to cool the design space 27.

  The reactivated inflow air 8 passes through the filter 42 and the temperature of this air is raised through the heat source 10 based on the specific design of the unit. The temperature is controlled by the thermostat 30 and is kept constant. In order to continuously change the reactivation air flow, the reactivation blower 5 is continuously variable in speed and has a suitable design according to the purpose. In order to obtain optimum performance, the rotor speed is also varied by the continuously variable speed bed drive 4.

  FIG. 8D schematically shows an example of a typical spatial dehumidification system. This is the same as the example of FIG. 8C except that one or more pairs of purge zones 17 and 18 are added. In such a configuration, it is typical to circulate a given amount of air 13,19 through two zones so as to form two closed loops, using two separate fans 15,21. As mentioned above, the air flow in each of the closed loops can be in any direction depending on which direction is most advantageous.

  The mixed air 38 exiting the dehumidifier can be mixed with the return air 28 and then passed through a cooling coil 24 for cooling the supply air 26 to cool the design space 27. The reactivated inflow air 8 passes through the filter 42 and the temperature of this air is raised through the heat source 10 based on the specific design of the unit. The temperature is controlled by the thermostat 30 and is kept constant. In order to continuously change the reactivation air flow, the reactivation blower 5 is continuously variable in speed and has a suitable design according to the purpose. In order to obtain optimum performance, the rotor speed is also varied by the continuously variable speed bed drive 4.

FIG. 8 (e) schematically shows an example of a typical spatial dehumidification system. This is an example of a pharmaceutical manufacturing area. Correspondingly, design conditions of 15% and 30% RH (relative humidity) at 75 ° F. (167 ° C.) have been selected for room 27. The total supply air amount 26 calculated in this example is 4000 cfm (114 m ³ / min). In order to satisfy the needs for space cooling and moisture removal, 600 cfm (17 m ³ / min) is taken out as return air 28. The required fresh air 31 (600 cfm = 17 m ³ / min) is passed through the cooling coil 23 and mixed with the return air 28. Face bypass damper 40 controls the air flow through the bypass / desiccant wheel. Return air 28 (2800 cfm = 80 m ³ / min) is mixed with process out air 7 to provide the required supply air flow 26. The total air volume then passes through the cooling coil 24 to provide the required room temperature.

  FIG. 9 shows a flowchart of the process drying / dehumidification system. In order to reduce the moisture load, the ambient air 31 is passed through the cooling coil 23 to cool the air. Bypass damper 32 regulates the air flow to pass through the desiccant wheel and diverts the rest. The mixed air 38 (process out 7 and bypass air 39) is passed through the heating source 24 / cooling source 22 and moderated depending on the requirements of the supply air 26.

  The regenerative flow 8 is also controlled by a damper 34 which is generally arranged behind the regenerative blower 5. The regenerative heat introduction source 10 may be an electric, steam, or gas burner, or may be formed from a variety of heat sources that can raise the temperature based on the specific design of the unit. This temperature is controlled by a thermostat 30.

  FIG. 10 (a) shows the product drying system and method. In such a system, the mixed air (process out 7 and bypass air 39) 38 is supplied to the process heat source 22 to provide the required drying temperature based on the conditions required in the drying bin 37. Is allowed to pass. Return air 28 is cooled through cooling coil 23 and blown through rotor process zone 2 and purge zone 11. A face and bypass damper 40 is used to limit the flow required to bypass the dehumidifier. The air leaving the purge zone is recirculated and mixed with the return air upstream of the cooling coil. This allows the dehumidifier to supply dry air. This purge zone may be approximately 5-40% of the total bed area. The remainder is divided into a process area 2 and a reactivation area 3. The reactivation inflow temperature is controlled through the thermostat 30. FIG. 10 (b) shows the desiccant bed / wheel 1 viewed from another angle. Here, various areas are shown. While these area areas are shown as typical, the area divisions can vary widely.

  FIG. 11 (a) compares the annual aftercooling requirements with different control options.

  FIG. 12 is a flow schematic diagram showing various HVAC element options. Each element may or may not be included based on the performance requirements of the application. The total amount of supply air to be passed through the cooling coil 59 / heating source 60 / dehumidifier 57 is based on the requirements of the space to be conditioned. Return air 28 may pass through cooling coil 54 or heating coil 53 to provide the required condition for mixing with fresh air 31. The fresh air 31 may pass through the heat recovery unit 50 when the required temperature needs to be raised and heating via the heat source 22 is required. If it is advantageous, the cooling coil 23 may be used to cool fresh air. The mixed air passes through the heating source 55 and the cooling source 56 based on requirements, and then passes through the face bypass damper 40. Face bypass damper 40 controls the flow that needs to be dehumidified through the desiccant wheel. The exhaust air exits through the blower 23 through the heat recovery unit 52. The regeneration air passes through the heat recovery unit 49 and then through the heat source to increase the temperature as per the specific design of the unit. The reactivated air stream exiting the reactivation zone 3 passes through the heat recovery zone 48 and passes through the regeneration blower 5. The use of a heat recovery unit reduces the load. The thermostat 30 may be arranged to control the temperature of the reactivation inflow behind the heat source or to control the temperature of the reactivation air exiting the desiccant wheel.

  As mentioned above, the present invention relates to a method and system for controlling the capacity of a desiccant dehumidifier having an active desiccant wheel. Since the moisture load changes instantaneously, the capacity of the dehumidifying unit and system needs to be controlled. Although several currently known control methods for reducing reactivation energy usage have been implemented, the present invention is a novel that significantly reduces reactivation energy usage compared to previously known methods. Provide a way.

  In the case of the present invention, the basic approach is to provide continuously a means of continuously changing the amount of air from the total process stream that will bypass the desiccant wheel. Reducing the process flow through the desiccant unit is generally done by tracking changes in the instantaneous moisture load. As the process flow through the desiccant wheel is reduced, it is no longer necessary to keep the entire regenerative flow through the wheel reactivation zone. If the regenerative stream is correspondingly reduced with some defined correlation, the regenerative energy usage is significantly reduced. In the case of the present invention, the regeneration flow can be configured to continuously decrease or increase through a control function based on a continuously changing process flow through the process zone. As technology changes, it is now economical and natural to use variable speed drives based on several well-known methods that now allow continuous changes in the reactivated air flow. It is.

  Similarly, the basis of the present invention is to use a technique that continuously varies the rotational speed of the wheel through the correlation control function. In developing this control function, the knowledge of the mathematical modeling tool “DRI Cal” or any other similar tool, such as “Procal”, is utilized. Both of these are similar tools currently used worldwide to select the desiccant unit / wheel geometry and flow.

While developing the present invention to continuously control the process variables of the dehumidifier, the energy usage was compared with several well-known and implemented methods. To develop the present invention, a sample project was first selected using the physical facts and assumptions typical of dehumidifying application designs. For this purpose, 70 ° F. (156 ° C.) and 30% RH were selected as design conditions. In order to obtain a better set of energy saving possibilities, a lower RH design of 15% at 70 ° F. (156 ° C.) was also selected for the same pharmaceutical application. The city of Zebulon, NC was selected for typical weather conditions in the southwestern United States. However, in order to demonstrate its effect on a humid climate, Mumbai, India, was selected as a typical one. A flow chart was created from the sample project / design and prepared. Using the given time weather data that is available and used today to provide a more detailed load profile for the project design, the ambient weather bin can be calculated using the average simultaneous dry bulb temperature and frequency of occurrence (hours / year). ) And 10 grains / lb. (1.43 g / kg) with increasing air. This allows for the calculation of several instantaneous load “bins” so that a simple simulation can be performed to estimate the total energy usage for each control method. Table 1 below shows the time bin data generated for both cities, Zebulon, North Carolina, USA, and Mumbai, India.

Using this method, the reactivation energy usage analysis is compared to applying design data based on two or three design points for all three control methods discussed and defined below. Become clearer.
a) Control option 1-fixed reactivation air flow, fixed reactivation inflow temperature, fixed rotor speed, variable process flow;
b) Control option 2-fixed reactivation air flow, fixed reactivation discharge temperature, fixed rotor speed, variable process flow (this is considered as a baseline control option for the purposes of the present invention) );
c) Control Option 3-Fixed reactivation inflow temperature, variable reactivation air flow, variable rotor speed, variable process flow through the wheel (the rest bypassing the wheel).

  Based on the annual bin data and the three control methods / options described above (option 3 is based on the present invention), energy usage (therm / year) for all three options was charted and compared. The comparison is shown in Tables 2, 3, 4, 5 and 6 below. The amount of energy used for post-cooling is also shown in Tables 5 and 6. These tables demonstrate that in addition to reducing renewable energy usage, total cooling energy usage is also significantly reduced.

Referring now to FIG. 11 (b), this graph shows a comparison of reactivation heat consumption (therm / year) for control options 1, 2 and 3. The case study was considered for 15% to 30% RH conditions for Zebulon and Mumbai. In the case of control option 2 (baseline control option), it is observed that the reactivation heat consumption is 11071 therm / year in a 15% RH designed zebran. When control option 1 is selected, the consumption increases to 13059 therm / year. However, when control option 3 is selected, the consumption is greatly reduced to 5747 therm / year. Tables 2, 3 and 4 show complete data on energy consumption of control options 1, 2 and 3 for 15% and 30% design RH for Mumbai and Zebulon. Table 5 is a summary of energy consumption in control options 1, 2 and 3 for the 30% RH design, and Table 6 is a summary of energy consumption in control options 1, 2 and 3 for the 15% RH design.

  Initially, the energy consumption analysis of the present invention for control option 3 was benchmarked against the baseline of control option 2, but using another commonly used dehumidifier capability control method with control option 1. It was further considered useful to complete the analysis.

  Thus, the resulting% energy reduction according to the present invention was compared between all three options using control option 2 as the baseline in Table 7 and control option 1 as the baseline in Table 8. .

Referring now to FIG. 11 (c), this graph shows the percentage of regenerative heat reduction using different control options. As shown, using control option 3, the reduction percentage can be as high as 47%. However, if control option 1 is selected as another baseline, the reduction percentage is even higher. This is a comparison between control options 1 and 3. Table 7 shows a detailed energy consumption comparison between control options 1, 2 and 3.

  From the foregoing, it is clear that the present invention provides a novel system and method of dehumidifier capacity control and allows significant energy savings compared to known techniques and methods.

  The system of the present invention has several other advantages, for example, the size of the reactivation area is selected from the range of 12% to 45% of the total desiccant rotor face area, and without modification to the cabinet design Built-in advantages of basic cabinet and plenum (forced ventilation) designs that can be set during production. In addition, if desired, the foundation cabinet and plenum design can be manually adjusted in the field using hand tools to any value within the range of 66% to 150% of the original design value. Can meet the changed performance requirements. When the system is used with a purge area with simultaneous air flow, the design of the base cabinet and plenum is that the purge area size in the range of 2% to 25% of the rotor face area will make a major design change. Allows to be added without.

  Although the present invention has been described with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. For example, numerous details presented herein, such as details relating to the form and operation of presently preferred embodiments of active desiccant modules and hybrid systems, are provided to facilitate understanding of the present invention. Rather, it is not provided to limit the scope of the invention. Accordingly, the disclosure of embodiments of the invention is intended to illustrate the scope of the invention and is not intended to limit the scope of the invention.

Claims (57)

A method for controlling an active desiccant dehumidifier comprising:
a. Adjusting the air flow through the process area to control the amount of dehumidification;
b. Adjusting the air flow through the reactivation zone as a function of adjusting the process air flow;
c. Adjusting the rotational speed of the desiccant wheel as a function of adjusting the process air flow;
A method of controlling an active desiccant dehumidifier comprising: A method for controlling an active desiccant dehumidifier comprising:
a. Adjusting the air flow through the process area to control the amount of dehumidification;
b. Adjusting the air flow through the reactivation zone as a function of adjusting the process air flow;
A method of controlling an active desiccant dehumidifier comprising: At least a desiccant wheel having a process zone with air flow means, a reactivation zone having air flow means, and means for rotating the desiccant wheel through the process zone and the reactivation zone; A method of controlling an active desiccant dehumidifier comprising a housing comprising reactivated air heating means,
The purpose of the control is to improve operating efficiency in partial load conditions, the method comprising:
a. Adjusting the air flow through the process area to control the amount of dehumidification;
b. Adjusting the air flow through the reactivation zone as a function of adjusting the process air flow;
c. Adjusting the rotational speed of the desiccant wheel as a function of adjusting the process air flow;
A method of controlling an active desiccant dehumidifier comprising:   4. A method according to any one of claims 1 to 3, wherein the adjustment of the process air flow comprises diverting a portion of the process air flow around the desiccant wheel.   4. A method according to any one of the preceding claims, wherein adjusting the process air flow comprises adjusting a damper that controls the process air flow.   Adjusting the process air flow comprises simultaneously controlling the air flow through the desiccant wheel and the air flow bypassing the desiccant wheel such that the total air flow remains substantially constant. Item 4. The method according to any one of Items 1 to 3.   The method of claim 1, wherein adjusting the process air flow includes changing an operating characteristic of the process air flow means.   The method of claim 1, wherein a minimum air flow rate through the process area is limited to a set point.   4. A method according to any one of claims 1 to 3, wherein the control function for regulating the reactivated air flow is a linear function.   4. The method according to any one of claims 1 to 3, wherein the control function for adjusting the reactivation air flow is an exponential function with an exponent of 0.5 to 2.0.   The method according to claim 1, wherein the control function for adjusting the rotational speed of the desiccant wheel is a linear function.   The method according to claim 1, wherein the control function for adjusting the rotational speed of the desiccant wheel is an exponential function having an exponent of 0.5 to 2.0. A method for controlling an active desiccant dehumidifier comprising:
a. Adjusting the air flow through the reactivation zone while maintaining a constant air flow through the process zone to control the amount of dehumidification;
b. Adjusting the rotational speed of the desiccant wheel as a function of adjusting the reactivation air flow;
A method of controlling an active desiccant dehumidifier comprising: At least a desiccant wheel having a process zone with air flow means, a reactivation zone having air flow means, and means for rotating the desiccant wheel through the process zone and the reactivation zone; A method of controlling an active desiccant dehumidifier comprising a housing comprising reactivated air heating means,
The purpose of the control is to improve operating efficiency in partial load conditions, the method comprising:
a. Adjusting the air flow through the reactivation zone while maintaining a constant air flow through the process zone to control the amount of dehumidification;
b. Adjusting the rotational speed of the desiccant wheel as a function of adjusting the reactivation air flow;
A method of controlling an active desiccant dehumidifier comprising:   15. A method according to any one of claims 1 to 3, or claim 13 or claim 14, wherein the heated temperature of the air entering the reactivation zone is maintained at a fixed value.   The method according to claim 15, wherein the heated temperature of the reactivation air is maintained at a fixed value by adjusting the heat introduced into the reactivation air heating means.   15. A method according to any one of claims 1 to 3, or claim 13 or claim 14, wherein the temperature of the reactivation air leaving the reactivation zone is maintained at a fixed value.   18. The method of claim 17, wherein the temperature of the air exiting the reactivation zone is controlled by adjusting the heat introduced into the reactivation air heating means.   The reactivated air heat source is maintained at a fixed value, the temperature of the reactivated heated air changes uncontrolled, increases as the air flow rate decreases, and as the air flow rate increases. 15. A method according to any one of claims 1 to 3, or claim 13 or claim 14, wherein the method is reduced.   20. The method of claim 19, wherein the reactivated air heat source is activated whenever there is an air flow through the reactivation zone.   15. A method according to any one of claims 1 to 3, or claim 13 or claim 14, wherein the adjustment of the reactivation air flow is achieved by adjusting a damper in the reactivation air flow.   15. A method according to any one of claims 1 to 3, or claim 13 or claim 14, wherein adjustment of the reactivation air flow is achieved by changing the operating characteristics of the reactivation air flow means.   The reactivation air flow regulation is achieved by diverting a portion of the reactivation air flow around the desiccant wheel, or any one of claims 1 to 3, or claim 13 or claim Item 15. The method according to Item 14.   15. A method according to any one of claims 1 to 3, or claim 13 or claim 14, wherein the minimum air flow through the reactivation zone is limited to a set point.   The adjustment of the rotational speed of the desiccant wheel is achieved by changing the operating characteristics of the desiccant wheel rotating means, or any one of claims 1 to 3, or claim 13 or claim 14. the method of.   The effective rotational speed of the wheel is achieved by intermittently operating the desiccant wheel rotating means such that the percentage of time that the rotating means operates is proportional to the demand control function. The method according to any one of claims 1 to 3, or claim 13 or claim 14.   15. A method according to any one of claims 1 to 3, or claim 13 or claim 14, wherein the minimum rotational speed of the desiccant wheel is limited to a set value.   15. A method according to claim 13 or claim 14, wherein the control function for adjusting the rotational speed of the desiccant wheel is a linear function of reactivated air flow.   15. A method according to claim 13 or claim 14, wherein the control function for adjusting the rotational speed of the desiccant wheel is an exponential function of a reactivated air flow with an index of 0.5 to 2.0. At least a desiccant wheel having a process zone with air flow means, a reactivation zone having air flow means, and means for rotating the desiccant wheel through the process zone and the reactivation zone; A method of controlling an active desiccant dehumidifier comprising a housing comprising a reactivated air heating means and a control system intended to improve the operating efficiency of the dehumidifier in a partial load condition,
The logical configuration of the control system is
a. Adjusting the air flow through the process area to control the amount of dehumidification;
b. Adjusting the air flow through the reactivation zone as a function of adjusting the process air flow;
c. Adjusting the rotational speed of the desiccant wheel as a function of adjusting the process air flow;
An active desiccant dehumidifier system. At least a desiccant wheel having a process zone with air flow means, a reactivation zone having air flow means, and means for rotating the desiccant wheel through the process zone and the reactivation zone; A method of controlling an active desiccant dehumidifier comprising a housing comprising a reactivated air heating means and a control system intended to improve the operating efficiency of the dehumidifier in a partial load condition,
The logical configuration of the control system is
a. Adjusting the air flow through the process area to control the amount of dehumidification;
b. Adjusting the air flow through the reactivation zone as a function of adjusting the process air flow;
An active desiccant dehumidifier system.   33. A system according to claim 31 or 32, wherein the adjustment of the process air flow includes diverting a portion of the process air flow around the desiccant wheel.   33. A system according to claim 31 or 32, wherein adjusting the process air flow includes adjusting a damper that controls the process air flow.   Adjusting the process air flow includes simultaneously controlling the air flow through the desiccant wheel and the air flow bypassing the desiccant wheel so that the total air flow remains substantially constant. The system according to claim 31 or 32.   33. A system as claimed in claim 31 or 32, wherein the adjustment of the process air flow comprises changing the operating characteristics of the process air flow means.   33. A system according to claim 31 or 32, wherein the minimum air flow through the process area is limited to a set point. At least a desiccant wheel having a process zone with air flow means, a reactivation zone having air flow means, and means for rotating the desiccant wheel through the process zone and the reactivation zone; A method of controlling an active desiccant dehumidifier comprising a housing comprising a reactivated air heating means and a control system intended to improve the operating efficiency of the dehumidifier in a partial load condition,
The logical configuration of the control system is
a. Adjusting the air flow through the reactivation zone to control the amount of dehumidification;
b. Adjusting the rotational speed of the desiccant wheel as a function of adjusting the reactivation air flow;
An active desiccant dehumidifier system.   38. A system according to claim 30, 31 or 37, wherein the heated temperature of the air entering the reactivation zone is maintained at a fixed value.   39. The system of claim 38, wherein the heated temperature of the reactivation air is maintained at a fixed value by adjusting the heat introduced into the reactivation air heating means.   38. A system according to claim 30, 31 or 37, wherein the temperature of the reactivation air leaving the reactivation zone is maintained at a fixed value.   41. The system of claim 40, wherein the temperature of the air exiting the reactivation zone is controlled by adjusting the heat introduced into the reactivation air heating means.   The reactivated air heat source is maintained at a fixed value, the temperature of the reactivated heated air changes uncontrolled, increases as the air flow rate decreases, and as the air flow rate increases. 38. The system of claim 30, 31, or 37, wherein the system is reduced.   44. The system of claim 43, wherein the reactivated air heat source is activated whenever there is an air flow through the reactivation zone.   38. A system according to claim 30, 31 or 37, wherein the adjustment of the reactivation air flow is achieved by adjusting a damper in the reactivation air flow.   38. A system according to claim 30, 31 or 37, wherein the adjustment of the reactivation air flow is achieved by changing the operating characteristics of the reactivation air flow means.   38. A system according to claim 30, 31 or 37, wherein adjustment of the reactivation air flow is achieved by diverting a portion of the reactivation air flow around the desiccant wheel.   38. A system according to claim 30, 31 or 37, wherein the minimum air flow through the reactivation zone is limited to a set point.   38. A system according to claim 30, 31 or 37, wherein the adjustment of the rotational speed of the desiccant wheel is achieved by changing the operating characteristics of the desiccant wheel rotating means.   The effective rotational speed of the wheel is achieved by intermittently operating the desiccant wheel rotating means such that the percentage of time that the rotating means is operated is proportional to the demand control function. 38. A system according to claim 31 or claim 37.   38. A system according to claim 30, 31 or 37, wherein the minimum rotational speed of the desiccant wheel is limited to a set point.   38. The system of claim 37, wherein the control function for adjusting the rotational speed of the desiccant wheel is a linear function of reactivated air flow.   38. The system of claim 37, wherein the control function for adjusting the rotational speed of the desiccant wheel is an exponential function of a reactivated airflow with an index of 0.5 to 2.0.   The dehumidifier also includes an intermediate purge zone between the reactivation zone and the process zone that pretreats a portion of the reactivation air. The method described in 1.   54. The method of claim 53, wherein the air flow through the purge zone is adjusted in direct proportion to the reactivated air flow.   The dehumidifier also includes one or more intermediate purge zones arranged to act as a buffer between the process zone and the reactivation zone, the intermediate purge zone passing through the intermediate purge zone. 17. A method according to any one of claims 1 to 3 or claim 16, comprising means for circulating a closed air stream.   56. The method of claim 55, wherein the air flow circulated through the purge zone is adjusted in direct proportion to the reactivated air flow.   56. The method of claim 55, wherein the air flow circulated through the purge zone is adjusted in direct proportion to the desiccant wheel rotational speed.

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