System and method for managing water content in a fluid

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Serial No. 60/748,123, filed ר December 2005, which is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates a system and method for managing water content in a fluid.

2. Background Art

Conventionally, water is collected from air, or other gaseous fluids, using condensation systems. An exemplary condensation system provides a surface cooled to a temperature that is at or below the dew point of incoming air. As is well known in the art, the cooling of ajr at or below its dew point causes the condensation of water vapor from the air and a decrease in the absolute humidity ofthe air. The humidity of a volume of air is substantially determinative ofthe amount of water that can be introduced into, or removed from, the volume of air.

Conventional water generation and removal systems collect water vapor from incoming airflows using condensation systems that lower the temperature of incoming air to a temperature that is at or below the dew point of the air. Therefore, the quantity of water produced by such systems depends on the humidity of the ambient air. The humidity and temperature of air varies, however, from region to region, with hot and humid air in tropical and semi-tropical regions, and cooler, less humid air in other parts of the world. The temperature and

WO 2007/066212 water vapor content of air also varies widely with seasonal weather changes in regions throughout the year. Therefore, depending on the region of the world, and depending on the time of year, humidification or dehumidification may be desirable, for example, to make an environment more comfortable.

Tn addition to increasing comfort, management of the amount of water in air may be important to industrial applications. Moreover, it may be desirable to remove water from air so that the water can be utilized, for example, for drinking, or in other applications where fresh water is desired. Regardless of the reason for managing the amount of water in the air, there are times when conventional water management systems have undesirable limitations. For example, when the dew point of the air is low, particularly when it is below the freezing point of water, it may be difficult or impossible to remove the water using a conventional system. The use of a desiccant inaterial may be effective to remove water from air or other fluid streams in such situations. Conventional systems utilizing desiccants do not account for changes in environmental conditions—e.g., changing temperature and humidity of the fluid stream—which may adversely affect the efficiency of the system.

Therefore, there is a need for a system and method for managing the water content in a fluid that can extract water from the fluid even when the dew point is low. There is also a need for a system and method for managing water content in a fluid that can control desiccant parameters to maintain system efficiency, for example, in light of changing environmental conditions.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a system and method for removing water from a fluid even when the dew point is low.

Embodiments of the invention also provide a system and method for removing water from a fluid using a desiccant having at least one parameter which can be controlled to

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PCI7IB2006/003523 modify the water removal capacity of the desiccant and maintain system efficiency in light of changing environmental conditions.

Embodiments of the invention further provide a system for managing water content in a fluid. The system includes a first chamber having an inlet and an outlet for facilitating movement of a first fluid into and out of the first chamber. A desiccant is capable of being introduced into the first chamber for removing water from the first fluid moving through the first chamber. A second chamber is configured to receive at least a portion of the desiccant after it removes water from the first fluid. The second chamber includes an inlet and an outlet for facilitating movement of a second fluid into and out of the second chamber. This facilitates evaporation of water from the desiccant into the second fluid, thereby increasing water content in the second fluid. A system heat exchanger is configured to receive a third fluid therethrough, and to receive the second fluid from the second chamber to facilitate a transfer of heat from the second fluid to the third fluid. This facilitates removal of water from the second fluid. A valve is operable to control the flow of the third fluid through the system heat exchanger. A sensor is in communication with the valve, and is configured to sense a parameter of the second fluid after its water content is increased. The sensor is configured to output signals to the valve related to the sensed parameter. This effects control of the flow of the third fluid through the system heat exchanger based on the sensed parameter.

The system can also include a first heat exchanger configured to receive the third fluid therethrough and to cool the desiccant before it is introduced into the first chamber. The first heat exchanger is arranged with the valve such that a reduction in flow of the third fluid through the valve increases the flow of the third fluid through the first heat exchanger. This increases the cooling capacity of the first heat exchanger.

Embodiments of the invention further provide a system for managing water content in a fluid. The system includes a first chamber having an inlet and an outlet for facilitating movement of a first fluid into and out of the first chamber. A desiccant is capable of being introduced into the first chamber for removing water from the first fluid moving through the first chamber. A second chamber is configured to receive at least a portion of the desiccant

WO 2007/066212 after it removes water from the first fluid. The second chamber includes an inlet and an outlet ' for facilitating movement of a second fluid into and out of the second chamber. This facilitates evaporation of water from the desiccant into the second fluid, thereby increasing water content in the second fluid. A heat exchanger arrangement having a controllable heat exchange capacity is configured to receive the second fluid from the second chamber to facilitate cooling of the second fluid. This facilitates removal of water from the second fluid. A sensor is configured to sense a parameter of the second fluid after its water content is increased, and is capable of outputting signals related to the sensed parameter. A control system, including at least one controller, is in communication with the heat exchanger arrangement and the sensor. The control system is configured to receive signals from the sensor and to effect control of the heat exchange capacity of the heat exchanger arrangement based at least in part on the signals received.

Embodiments of the invention further provide a method for managing water content in a fluid using a system which includes a desiccant and a system heat exchanger. The method includes removing water from a first fluid using a process that includes exposing at least some of the first fluid to the desiccant. This increases the water content of at least some of the desiccant. At least some of the desiccant having increased water content is introduced into a second fluid, thereby facilitating evaporation of water from the desiccant into the second fluid and increasing water content of the second fluid. The second fluid is passed through the system heat exchanger after the water content of the second fluid is increased. This facilitates cooling of the second fluid and removal of water therefrom. A parameter of the second fluid is sensed after its water content is increased, and the heat exchange capacity of the system heat exchanger is controlled at least partly based on the sensed parameter.

Embodiments of the present invention also provide a system and method for passing ambient air into a first chamber having a suitable desiccant material therein. The desiccant absorbs or adsorbs moisture from the air that comes in contact with the desiccant. In one embodiment, the air contacts desiccant by pumping air through a contact surface, such as a sponge, media, cooling coil, or cooling tower, that has desiccant dispersed therein. The desiccant and/or first chamber may be cooled to enable the more efficient transfer of water from the air to the desiccant. The desiccant absorbs or adsorbs water from the air, thereby transferring

WO 2007/066212 latent heat from the air as the water undergoes a phase change and condenses out of the air.

Because the desiccant and/or first chamber are cooled, sensible cooling—i.e., cooling that is not based on a change of state—is also provided to the air. The resulting dry, cooled air is drawn out from the first chamber.

The now hydrous desiccant collects at the bottom of the first chamber and gets transferred to a second chamber. The second chamber transfer occurs either through active pumping or diffusion via a valve opening provided in a partition between the first and the second chambers. The valve opening enables equalization of desiccant levels in the first and the second chamber. The net flow of hydrous desiccant occurs from the first chamber to the second chamber until the level of the desiccant equalizes in the two chambers. The diffused or pumped hydrous desiccant in the second chamber can be heated and then again exposed to air.

The desiccant can be introduced into the chambers by any method effective to achieve the desired result. For example, the first chamber may include spongy cellulose material through which the hydrated desiccant percolates down to collect at the bottom of the chamber. Alternatively, the desiccant is made to simply drip in the form of drops from points within, such as the top of, the first and second chambers. In one embodiment, the desiccant is sprayed into the interior of the second chamber. A heat exchanger such as a heating element warms the spray of hydrous desiccant falling from the nozzles, thereby evaporating moisture absorbed or adsorbed into the desiccant, generating hot humid air, and also regenerating substantially anhydrous desiccant.‘

The hot, humid air leaving the second chamber can be directed to contact the dew-forming surfaces of a heat absorber, such as an evaporator, that are cooled using a suitable cooling process such as classic boiling fluids contained in tubes, thermoelectric elements, heat pipes, refrigerant-expansion coils or any other system known to persons of ordinary skill in the art. A parameter of the hot, humid air can be sensed—e.g., the humidity or the temperature, and the heat absorbing capacity of the evaporator can be appropriately controlled. For example, if the sensed temperature drops below a set point, the heat absorbing capacity of the evaporator can be reduced. At the same time, the desiccant entering the first chamber can be further cooled, for

WO 2007/066212 example, by increasing the heat absorbing capacity of a heat exchanger through which the desiccant is passed. This will ultimately lead to an increased load in the evaporator, which will cause the temperature to rise above the set point, thereby leading to an increase in the heat absorbing capacity of the evaporator. In this way, changing environmental conditions are accounted for, and the overall efficiency of the system is increased.

At least one embodiment of the present invention can sterilize and filter the condensed water to generate pure drinking water. Accordingly, in one embodiment, condensed water from the condensate collector is exposed to suitable ultra-violet (UV) radiation in a UV unit to free the water from harmful microscopic organisms. Additionally, the radiated water is serially passed through a charcoal filter to remove contaminants and Volatile Organic Compounds (VOC's) and a plurality of mineral cartridges to mineralize and/or vitaminize the water The purified and mineralized water is collected in a first storage tank Additionally, the water is passed through an oxygenator before being stored in the first storage tank. Water from the first' storage tank is recirculated through the UV unit at predetermined intervals of time to maintain quality of water.

At least one embodiment of the present invention can also dispense hot and cold water. Thus, in one embodiment, water from the first storage tank is gravity fed into a second cold storage tank from where it is further gravity fed into a third hot storage tank. Water in the second storage tank is chilled using a suitable cooling process such as Peltier-effect or chemical/magnetic cooling, by the use of a typical expansion-evaporation coils, or by any other method effective to achieve the desired result. The cold water is then dispensed through a first childproof spigot. Also, water in the third tank is heated to a desired temperature by a heating element and dispensed through a second spigot. Ambient temperature water is dispensed from the second spigot when power is disallowed to the heating element of the third tank. In another embodiment, water from the first storage tank can be directly dispensed through a third spigot to provide water at ambient temperature.

Embodiments of the present invention may also be configured to provide for the introduction of water from external sources in the event of low condensate formation.

WO 2007/066212

Accordingly, an external source such as a municipal supply faucet is attached through quickdisconnect fittings to supply supplemental water to the first storage tank.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 shows a schematic diagram of a system for managing water content in a fluid in accordance with one embodiment of the present invention; and

Figure 2 shows a schematic diagram of a system for managing water content in a fluid in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Figure 1 shows a system 10 for managing water content in a fluid in accordance with one embodiment of the present invention, hi particular, the system 10 is configured to manage the water content in air—either to collect water from the air for storage and subsequent use, or to control the humidity of the air. It is worth noting that although the examples presented herein utilize ambient air as the fluid whose water content is being managed, the present invention is capable of managing the water content of other fluids as well—e.g., gases, liquids, or some combination thereof. The system 10 includes a first chamber, or collection chamber 12, and a second chamber, or regeneration chamber 14. The collection chamber 12 includes an inlet 16 and an outlet 18 which allow a first airflow 19 to flow through the collection chamber 12. As the air flows through the collection chamber 12, it contacts a desiccant 20, which, in the embodiment shown in Figure 1, is sprayed into the chamber 12 via a conduit 22.

As the air moves through the collection chamber 12, vaporized water is condensed out, and collects with the desiccant 20 in the bottom portion 24 of the chamber 12. The desiccant 20 is diluted as it adsorbs or absorbs the water from the air. Although the desiccant 20 shown in Figure 1 is all liquid, the present invention contemplates the use of solid desiccants, or dual phase desiccants—e.g., solid and liquid. Any desiccant material effective to

WO 2007/066212 produce the desired result may be used, Including solids, liquids, solutions, aqueous solutions, mixtures, and combinations thereof. Lithium chloride (LiCl) and calcium chloride (CaC12) are typical of liquid desiccant solutions, but other liquid desiccants may be employed.

Liquid desiccants such as polycols, alone or in mixture, may be used. Typical polycols include liquid compounds such as ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, glycerol, trimethyol propane, diethytlene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, and mixtures thereof. Polyol compounds which are normally solid, but which are substantially soluble in anhydrous liquid polytfls or liquid hydroxyl amines, may also be used. Typical of these solid polyol compounds are erythritol, sorbitol, pentaerythritol and low molecular weight sugars. Typical hydroxyl amines include alkanolamines, such as monoethanol amine, diethanol amine, triethanol aipine, isopropanol amine, including mono, di, and tri, isopropanol amine or digylcolamine.

Still other types of desiccants such as montmorillonite clay, silica gel, molecular sieves, CaO, CaSO4 can all be used. As would be evident to persons of ordinary skill in the art, the selection of a desirable desiccant depends, among other parameters, upon the temperature and humidity ranges of ambient air from which moisture is to be absorbed. Still other exemplary desiccants comprise materials such as P2O5, BaO, A12O3, NaOH sticks, KOH fused, CaBr2, ZnC12, Ba(C104)2, ZnBr2.

As noted above, the desiccant 20 is a liquid desiccant, which may comprise an aqueous solution of 40% lithium chloride. Inside the collection chamber 12 is a matrix material 23. The matrix 23 can be a sponge or other medium or media effective to facilitate contact between the desiccant 20 and the air flowing through the collection chamber 12. The desiccant 20 is pumped into the conduit 22 by a pump 26. The pump 26 pumps the desiccant 20 through a first heat exchanger 28 prior to its introduction into the collection chamber 12. By cooling the desiccant 20, its ability to remove water from the first airflow 19 is increased. A fluid, such as a refrigerant, is passed through the heat exchanger 28 via conduits 30, 32. The desiccant 20 is cooled in the heat exchanger 28 to a temperature below that of the first airflow 19 In this way,

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PCI7IB2006/003523 the airflow 19 is cooled as it passes through the collection chamber 12. As an alternative to the heat exchanger 28, a heat exchanger may be placed inside the collection chamber 12 to cool the first airflow 19 directly, or to cool the desiccant 20 after it is sprayed into the collection chamber

12.

The regeneration chamber 14 also includes an inlet 34 and an outlet 36, which facilitate movement of a second airflow 38 into and out of the regeneration chamber 14. As with the collection chamber 12, the regeneration chamber 14 also includes a pump 40 which is used to pump the desiccant 20 into the regeneration chamber 14 through a conduit 42. The desiccant 20 is sprayed into the regeneration chamber 14 to contact a matrix 44, which, like the matrix 23, may be a sponge or other medium or media.

Between the two chambers 12,14 is a flow controller 46, which can be an electronic valve, operable to allow the hydrous desiccant from the collection chamber 12 to mix with desiccant in the regeneration chamber 14, and vice versa. Instead of the valve 46, other flow control devices may be used to control the flow of desiccant between the two chambers 12, 14. For example, a partition may be used for equalization in concentration of the desiccant 20, which can be achieved through osmotic flow. In this way, the desiccant 20 in the collection chamber 12 is not rapidly diluted and rendered ineffective.

The pumps 26,40 can pump the desiccant 20 into their respective chambers 12, 14 through respective conduits 45,47. Alternatively, some or all of the desiccant 20 can be pumped from one of the chambers 12,14, to the other of the chambers 12,14 through the flow controller 46. In some embodiments of the present invention, a flow controller, such as the flow controller 46, can have two inlets connected directly to respective pump outlets, and two outlets connected directly to respective heat exchanger inlets, thereby eliminating the need for conduits 45,47. In some embodiments, the flow through the valve 46 is much less than the flow through the respective conduits 45,47. For example, if the pumps 26,40 have a flow rate of 200 liters per minute (1pm), the flow through the valve 46 may be 100 liters per hour (Iph). Thus, only a fraction of the fluid pumped by the pumps 26,40 is pumped into the opposite chamber 14,12, respectively. Conversely, other embodiments of the present invention may have pumps and flow

־9 controllers with different flow rates—both in terms of absolute flow rates and in terms of flow rates relative to each other.

As shown in Figure 1, the desiccant 20 is pumped by the pump 40 through a second heat exchanger 48. Heat can be added to the heat exchanger 48 from any convenient source, via conduits 50, 52. By passing through the heat exchanger 48, the desiccant 20 is heated to a temperature above the temperature of the second airflow 38, so that the second airflow 38 is heated as it passes through the regeneration chamber 14. By heating the second airflow 38, more water is evaporated from the desiccant 20 into the second airflow 38. As an alternative to the heat exchanger 48, which is located outside the regeneration chamber 14, a heat exchanger (not shown) may be located inside the regeneration chamber 14.

Use of the system 10 results in two separate airflows exiting the chambers 12, 14. The first airflow 19 of now dry air exits the collection chamber 12 through the outlet 18, and the second airflow 38 of now humid air exits the regeneration chamber 14 through the outlet 36. One of ordinary skill in the art will appreciate that the extraction of water from the first airflow 19 increases the latent heat of the desiccant 20, and results in latent cooling of the first airflow

19. Additionally, because the desiccant 20. (or alternatively the chamber 12, or both) is cooled, the first airflow 19 itself undergoes sensible cooling that lowers its temperature level, thereby creating cooled, dry air. In one embodiment, the present invention uses 10 liters of lithium chloride solution to extract 2 liters per hour of moisture from incoming air that is provided by an air blower rated at 250 m³/hour. The result is a sensible cooling capacity of 0.7 kilowatts (kW) and a latent cooling capacity of 1.4 kW, thereby enabling a temperature reduction in the air of 8.4°C.

The warm, humid air 38 leaving the regeneration chamber 14 can be introduced into a system heat exchanger, or evaporator 54. The evaporator 54 includes a contact surface 56, which causes water 58 to condense out of the humid air stream 38. The water 58 may be collected in a storage tank 60 for later use. Depending on the use intended for the water 58, it can be sterilized and/or treated using a secondary system, or by expanding the system 10 to Include such elements. One such system is described in International Patent Publication

W02006/026494, entitled “System and Method for Producing Water”, which is hereby incorporated herein by reference.

The evaporator 54 is part of a refrigeration subsystem 62, which includes the first and second heat exchangers 28, 48. The first and second heat exchangers 28, 48 respectively act as an evaporator and condenser within the subsystem 62. A third fluid, or refrigerant, is pumped through the subsystem 62 by a compressor 64, while throttling devices 66, 68 facilitate expansion of the refrigerant before it reaches a respective evaporator 28, 54.

To selectively control the flow of the refrigerant through the evaporators 28, 54, a control valve 70 is used. The control valve 70 is in communication with a sensor 72 at least partly disposed within the evaporator 54. The sensor 72 is configured to sense a parameter of the second airflow 38 after it has picked up water in the regeneration chamber 14. For example, the sensor 72 can be a hygrometer or other device capable of measuring the humidity of the airflow 38, which may be convenient when the system 10 is used as a dehumidifier. Alternatively, the sensor 72 can be a temperature sensor configured to sense a temperature of the airflow 38, which may be convenient when the system 10 is used to produce water. In any case, the sensor 72 can output signals related to the sensed parameter to control the valve 70.

In the embodiment shown in Figure 1, the sensor 72 is configured to sense the temperature of the airflow 38 in the evaporator 54. When the valve 70 is open, thereby allowing refrigerant to flow through the evaporator 54, the evaporator 54 cools the airflow 38. The sensor 72 is configured such that when the sensed temperature drops to a predetermined set point—e.g., 3°C—the sensor 72 signals the valve 70 to close. This stops the refrigerant from flowing through the evaporator 54, and increases the amount of refrigerant flowing through the other evaporator, or first heat exchanger 28. In this way, the heat absorbing capacity of the evaporator 54 is reduced—i.e., its cooling capacity is increased—while the heat absorbing capacity of the evaporator 28 is increased. The increased cooling of the desiccant 20 entering the collection chamber 12 results in more water being absorbed from the first airflow 19, and thereby increases the vapor pressure of the desiccant 20. In other embodiments, a sensor, such as the sensor 72, can include a hygrometer, configured to measure the humidity of the airflow 38. In such embodiments, a sensed humidity at or below a set point humidity can cause signals to be sent to close the valve 70, again reducing the cooling capacity of the evaporator 54 and automatically increasing the cooling capacity of the evaporator 28.

In situations where the moisture content in the airflows 19,38 is low, the set point—temperature or humidity—will quickly be reached, and the desiccant 20 entering the collection chamber 12 will receive increased cooling. This results in an increase in the amount of water collected in the collection chamber 12 and subsequently transferred to the regeneration chamber 14 through the flow controller 46. This, in turn, causes a higher load in the regeneration chamber 14, and ultimately, an increase in the temperature sensed by the sensor 72. Tn order to keep the valve 70 from constantly cycling between open and shut, a hysteresis can be built in to the system 10. In this way, the valve 70 may be shut when the sensed temperature is at one set point, but it may not be opened until the sensed temperature reaches another set point, slightly higher than the first set point.

In the system 10, either or both of the sensor 72 and the valve 70 may include one or more controllers which can be programmed, for example, with temperature or humidity set points; In addition, the flow controller 46 can be programmed to appropriately manage the flow of the desiccant 20 between the collection and regeneration chambers 12,14. Thus, the system 10 includes a control system made up of independently operating controllers. Alternatively, a system controller can be used to coordinate the functions of the various elements of the system; such a system is illustrated in Figure 2. In Figure 2, the prime symbol (') has been used to identify elements which are related to those found in the system 10 shown in Figure 1.

Figure 2 illustrates a system 10' for managing the water content in air. As with the system 10, shown in Figure 1, the system 10' includes collection and regeneration chambers 12', 14', each of which has its own heat exchanger 28', 48' for controlling the temperature of the desiccant 20'. The heat exchangers 28', 48' are part of a refrigeration subsystem 62'. The refrigeration subsystem 62' also includes a heat exchanger arrangement 74, which includes a heat exchanger, or evaporator 54’, and a refrigerant flow valve 70'. Although the evaporator 54' is shown separately from the flow control valve 70', it is understood that they can be integrated into

WO 2007/066212 a single device, which can also include a sensor 72'. Similar to toe sensor 72, shown in Figure 1, toe sensor 72' is configured to sense a parameter of toe airflow 38'—e.g., temperature, humidity, etc.—and to output signals related to the sensed parameter.

Rather than relying on a number of independent controllers, toe system 10' includes a system controller 76, which communicates with other controllers—e.g., toe flow controller 46' and a controller or controllers within toe valve 70' and toe sensor 72'—to make up a control system. As shown in Figure 2, toe system controller 76 can be used to control other elements of toe system 10', such as pumps 26', 40'. This configuration may conveniently provide a centralized control of toe various elements in a system, such as the system 10. Similar to toe system 10, shown in Figure 1, toe system 10' can function to modify toe heating or cooling capacities of various system elements to accommodate changing environmental conditions.

While embodiments of toe invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, toe words used in toe specification are words of description rather than limitation, and it is understood that various changes may be made without departing from toe spirit and scope of toe invention.