System and method for managing water content in a fluid

SYSTEM AND METHOD FOR MANAGING WATER

CONTENT IN A FLUID מערכת ושיטה לשליטה בכמות מים בנוזל

Eitan-Mehulal Law GroupAdvocates-Patent AttorneysP11007־-IL PCTflB2007/004333 WO 2008/053367

SYSTEM AND METHOD FOR MANAGINGWATER CONTENT IN A FLUID

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional applicationSerial No. 60/840,312 filed 25 August 2006, which is hereby incorporated hereinby reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates a system and method for managingwater 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 surfacecooled to a temperature that is at or below the dew point of incoming air. As is wellknown in the art, the cooling of air at or below its dew point causes thecondensation 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 of the amountof water that can be introduced into, or removed from, the volume of air.

The humidity and temperature of air varies, however, from region toregion, with hot and humid air in tropical and semi-tropical regions, and cooler, lesshumid air in other parts of the world. The temperature and water vapor content ofair 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 anenvironment more comfortable. PCT/EB2007/004333 WO 2008/053367

In addition to increasing comfort, management of the amount of waterin air may be important to industrial applications. Moreover, it may be desirableto remove water from air so that the water can be utilized, for example, fordrinking, or in other applications where fresh water is desired. Regardless of thereason for managing the amount of water in the air, there are times whenconventional water management systems have undesirable limitations. For example,when the dew point of the air is low, particularly when it is below the freezing pointof water, it may be difficult or impossible to remove the water using a condensationsystem. One way to remove water from air even when the dew point is low is to usea system utilizing a desiccant to extract water from the air.

In a desiccant system, both heat and mass are transferred to and fromthe air. Conventional systems of this type are generally inefficient in at least oneof the two types of transfer—i.e., heat or mass transfer—because the transfer of oneinherently transfers the other, which may be undesirable. For example, a desiccantwheel can be used to remove water vapor from an airflow, thereby transferring massout of the air and reducing the enthalpy of the air. At the same time, however, alarge amount of heat may be added by the phase change occurring as the watercondenses out of the air; this causes an increase in the enthalpy of the air.

Conventional desiccant based dehumidifiers generally require themovement of the desiccant from a first region where it absorbs moisture—i.e,, a"collection" or "dehumidiying" station—to a second region where it expels themoisture—i.e., a regeneration station. In the case of solid desiccants, this transferis achieved by physically moving the desiccant from a dehumidifying station to aregeneration station, for example, by mounting the desiccant on a rotating wheel,a belt or the like. In liquid desiccant systems, two pumps are generally provided:one for pumping the liquid to the regeneration station, and the other for pumping theliquid from the regeneration station to the dehumidifying station. In someembodiments, a single pump is used to pump from one station to the other, with thereturn flow being gravity fed. PCT/IB2007/004333 WO 2008/053367

One such system removes air from a first airflow by spraying the firstairflow with a liquid desiccant. The desiccant may be cooled prior to being sprayed.Water removed from the air is collected by the desiccant, which becomesincreasingly diluted. The cool, diluted desiccant is collected in the bottom of acollection chamber. On the other side of the system, the diluted desiccant is heatedand brought into contact with a second airflow, which removes the water from thedesiccant, thereby leaving it more concentrated. The warm, concentrated desiccantis collected in the bottom of a regeneration chamber.

The two chambers may be connected, for example by an orifice, toallow mixing of the diluted and concentrated desiccant pools. Because aconcentration gradient will exist between the diluted and concentrated desiccants,diffusion between the two chambers will naturally occur. Although the orifice maybe an efficient mechanism to transfer mass—i.e., the water ions—it also facilitatesheat transfer as the warm, concentrated desiccant mixes with the cool, diluteddesiccant. This may be acceptable in some applications, but in others, it may bedesirable to have a system that controls both heat and mass transfer.

Another type of air conditioning desiccant system is described inU.S. Patent No. 4,941,324 issued to Peterson et al. on 17 July 1990. Peterson etal. describes a mechanism to transfer liquid desiccant between a condenser sump andan evaporator sump. Dilute desiccant from the evaporator sump is transferred intothe condenser sump, and concentrated desiccant from the condenser sump istransferred back to the evaporator sump. The transfer mechanism includes a pairof pumps and a series of globe valves that control the amount of desiccanttransferred between the sumps and the amount of desiccant delivered to desiccantdistributors.

One limitation of the Peterson et al. system is limited control over theamount of desiccant transferred between the sumps. Specifically, such a system mayresult in undesirably large quantities of desiccant being pumped between the twosumps in order to continuously regenerate the desiccant. Because the temperatureof the desiccant in the condenser sump may be significantly higher than the PCT/IB2007/004333 WO 2008/053367 temperature of the desiccant in the evaporator sump, an undesirable amount of heattransfer can occur as the large mass of liquid is transferred between the sumps. Thiscan be very inefficient. To help reduce this inefficiency, the Peterson et al. systemutilizes a heat exchanger to transfer heat between the two desiccant streams as theyare pumped between the two sumps. Although this may reduce some of theinefficiency, the process may yet be undesirably inefficient because of the largequantity of liquid being transferred.

In many different fields—e.g., air conditioning, collecting water fromair, and generating power using a combustion engine or gas turbine—controlling thetransfer of both heat and mass of one or more materials is important to the overallefficiency of the process. Therefore, there is a need for a system and method formanaging the water content in a fluid that can extract water from the fluid under avariety of ambient conditions utilizing a desiccant that is at least partly liquid , andthat can efficiently control the transfer of both mass and heat of the water to andfrom the desiccant.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a system and methodfor managing water content in a fluid using a desiccant that is at least partly liquid,and in which the mass transfer and the heat transfer of the water to and from thedesiccant are controlled. Such a system and method can be used in the areas of airconditioning, water production, environmental control, and energy production.

Embodiments of the invention also provide a system and method formanaging water content a fluid iu which cooled desiccant is diluted as it removeswater from an airflow, and is collected in a sump of a collection chamber. Diluteddesiccant is transferred to a regeneration chamber, where it is heated and broughtinto contact with another airflow. This effects removal of the water from thedesiccant, and the now concentrated desiccant is collected in a sump of theregeneration chamber. The desiccant in the sumps is mixed in such a way as toefficiently control the transfer of heat and mass of the water in the desiccant pools. PCT/IB2007/004333 WO 2008/053367

In one embodiment, the two sumps are connected by an aperture,such as an orifice. When the liquid desiccant is sprayed in the collection chamber,its mass and volume increase as it removes water from the air. As the desiccantcontinues to pickup more water from the airflow, its level in the collection sumprises. When it exceeds the level of the orifice, some of the diluted desiccant entersthe regeneration chamber and mixes with the more concentrated desiccant in theregeneration sump; this causes the level of the desiccant in the regeneration sumpto rise. When the desiccant in the regeneration chamber reaches a predeterminedlevel, a float-actuated valve opens to allow some of the desiccant to be pumped backinto the collection chamber. In this way, mass is not transferred from the collectionchamber to the regeneration chamber until the desiccant level in the collectionchamber reaches the orifice. Similarly, mass is not transferred from theregeneration chamber to the collection chamber until the desiccant level in thecollection chamber moves the float to actuate the valve. The orifice and the floatswitch can be positioned as desired, such that the mass flow is efficiently controlled.

Because the temperatures of the desiccant in the two sumps is likelyto be different—the desiccant in the collection sump being cooler than the desiccantin the regeneration sump—the invention also controls the heat transfer between thetwo desiccant chambers. In one embodiment, the wanner, concentrated desiccantfrom the regeneration sump is passed through a heat exchanger—e.g., an evaporatorof a refrigeration system—before it enters the collection chamber. This cools theconcentrated desiccant, and may reduce the required energy input into the system,since the desiccant in the collection chamber will not require as much cooling priorto its being sprayed on the airflow in the collection chamber.

In another embodiment of the invention, the desiccant in thecollection sump is cooled using an evaporative heat exchanger, which is part of arefrigeration vapor compression cycle, prior to being brought into contact with theairflow. Similarly, the concentrated desiccant from the regeneration sump is passedthrough a heat exchanger to pickup heat prior to being sprayed on the airflow in theregeneration chamber. In some embodiments, the heat exchanger may be part of aseparate refrigeration cycle, or alternatively, may be connected to another heat- PCT/IB2007/004333 WO 2008/053367 producing device, such as an engine or generator. In other embodiments, the heatexchanger may be a condenser that is part of the same refrigeration cycle as theevaporator.

To effect efficient transfer of heat between the two chambers, a5 system heat exchanger may be used. The system heat exchanger can be configuredto receive both streams of desiccant as they are transferred from one chamber toanother. Specifically, the cooler, diluted desiccant leaves the collection sump whenit reaches the level of the orifice. It then flows through the system heat exchangerand into the regeneration chamber. On the other side, warmer, concentrated10 desiccant is pumped through the system heat exchanger when the level in theregeneration sump is high enough to actuate the float valve. In the system heatexchanger, the desiccant being pumped to the collection chamber gives up heat,while the desiccant flowing into the regeneration chamber picks up heat. In thisway, less cooling is required of the collection chamber desiccant, and less heating15 is required of the regeneration chamber desiccant. Thus, the heat transfer and themass transfer are both controlled to provide an efficient system.

The systems described above can be adapted for use in a number ofdifferent fields. For example, such a system can be used in environmental control20 to dehumidiiy and cool the air in an interior space. Alternatively, or in concert withthe environmental control system, the water retained by the airflow in theregeneration chamber can be collected for use as potable or non-potable water. Suchwater collection can be effected by passing the moist airflow leaving theregeneration chamber through an evaporator of a refrigeration system. In some25 embodiments, the airflows leaving the collection and regeneration chambers may bepassed through a heat exchanger to transfer heat between the two airflows, therebyresulting in condensation and water collection from the moist airflow.

At least one embodiment of the present invention can sterilize andfilter the condensed water to generate pure drinking water. Accordingly, in one30 embodiment, condensed water from the condensate collector is exposed to suitableultra-violet (UV) radiation in a UV unit to free the water from harmful microscopic ־6- PCT/IB2007/004333 WO 2008/053367 organisms. Additionally, the radiated water is serially passed through a charcoalfilter to remove contaminants and Volatile Organic Compounds (VOC’s) and aplurality of mineral cartridges to mineralize and/or vitaminize the water. Thepurified and mineralized water is collected in a first storage tank. Additionally, thewater 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 atpredetermined intervals of time to maintain quality of water. Embodiments of thepresent invention may also be configured to provide for the introduction of waterfrom external sources in the event of low condensate formation. Accordingly, anexternal source such as a municipal supply faucet is attached through quick-disconnect 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 managingwater 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 watercontent in a fluid in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Figure 1 shows a system 10 for managing water content in a fluid inaccordance with one embodiment of the present invention. In particular, the system10 is configured to manage the water content in air—either to collect water from theair for storage and subsequent use, or to control the humidity of the air. It is worthnoting that although the examples presented herein utilize ambient air as the fluidwhose water content is being managed, the present invention is capable of managingthe water content of other fluids as well. The system 10 includes a first chamber,or collection chamber 12, and a second chamber, or regeneration chamber 14. Thecollection chamber 12 includes an inlet 16 and an outlet 18 which allow a first PCT/IB2007/004333 WO 2008/053367 airflow 20 to flow through the collection chamber 12. As the air flows through thecollection chamber 12, it contacts a desiccant 22, which, in the embodiment shownin Figure 1, is sprayed into the chamber 12 via a conduit 24.

As the air moves through the collection chamber 12, vaporized wateris condensed out, and collects with the desiccant 22 in a collection sump 26 in thebottom portion of the chamber 12. The desiccant 22 is diluted as it adsorbs orabsorbs the water from the air. Although the desiccant 22 shown in Figure 1 is allliquid, the present invention contemplates the use of dual phase desiccants—e.g.,solid and liquid. Any desiccant material effective to produce the desired result maybe used, including lithium chloride (LiCl) and calcium chloride (CaCl2), which aretypical of liquid desiccant solutions; however, other liquid desiccants may beemployed.

Liquid desiccants such as polycols, alone or in mixture, may be used.Typical polycols include liquid compounds such as ethylene glycol, propyleneglycol, butylene glycol, pentylene glycol, glycerol, trimethyol propane, diethytleneglycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropyleneglycol, tetrapropylene glycol, and mixtures thereof. Polyol compounds which arenormally solid, but which are substantially soluble in anhydrous liquid, polyols orliquid hydroxyl amines, may also be used. Typical of these solid polyol compoundsare erythritol, sorbitol, pentaerythritol and low molecular weight sugars. Typicalhydroxyl amines include alkanolamines, such as monoethanol amine, diethanolamine, triethanol amine, isopropanol amine, including mono, di, and tri,isopropanol amine or digylcolamine.

As noted above, the desiccant 22 is a liquid desiccant, which may bea pure substance, or may comprise an aqueous solution of 40% lithium chloride.The desiccant 22 is pumped into the conduit 24 by a pump 28. The pump 28 pumpsthe desiccant 22 through a first heat exchanger 30 prior to its introduction into thecollection chamber 12. By cooling the desiccant 22, its ability to remove waterfrom the first airflow 20 is increased. A fluid, such as a refrigerant, is passedthrough the heat exchanger 30 via conduits 32, 34. For example, the heat exchanger ־8- PCT/1B200 7/0 04333 WO 2008/053367 30 may be an evaporator that is part of a refrigeration system. Such a refrigerationsystem can be used to control ambient environmental conditions, or for some otherpurpose or purposes. The desiccant 22 is cooled in the heat exchanger 30 to atemperature below that of the first airflow 20. In this way, the airflow 20 is cooledas it passes through the collection chamber 12. As an alternative to the heatexchanger 30, a heat exchanger may be placed inside the collection chamber 12 tocool the first airflow 20 directly, or to cool the desiccant 22 after it is sprayed intothe collection chamber 12.

The regeneration chamber 14 also includes an inlet 36 and an outlet38, which facilitate movement of a second airflow 40 into and out of theregeneration chamber 14. As with the collection chamber 12, the regenerationchamber 14 also includes a pump 42 which is used to pump the desiccant 22 into theregeneration chamber 14 through a conduit 44. The desiccant 22 is pumped by thepump 42 through a second heat exchanger 46. Heat can be added to the heatexchanger 46 from any convenient source, via conduits 48, 50. For example, theheat exchanger 46 can be a condenser that forms part of a refrigeration system.Such a refrigeration system can be the same refrigeration system using the heatexchanger 30. In such a case, the heat exchangers would each be connected to acompressor, or refrigerant pump, thereby allowing the system 10 to generate its ownheating and cooling without relying on any external sources. Alternatively, the heatexchanger 46 could receive heat from other sources, such as combustion engines orgenerators.

By passing through the heat exchanger 48, the desiccant 22 is heatedto a temperature above the temperature of the second airflow 40, so that the secondairflow 40 is heated as it passes through the regeneration chamber 14. By heatingthe second airflow 40, more water is evaporated from the desiccant 22 into thesecond airflow 40. As an alternative to the heat exchanger 46, which is locatedoutside the regeneration chamber 14, a heat exchanger (not shown) may be locatedinside the regeneration chamber 14. After the desiccant 22 is sprayed over theairflow 40 in the regeneration chamber 14, it collects in a regeneration sump 52 atthe bottom of the regeneration chamber 14. The warm, humid airflow 40 leaving PCT/IB2007/004333 WO 2008/053367 the regeneration chamber 14 can be introduced into another heat exchanger (notshown) to remove water from the airflow 40.

As described above, the present invention provides an efficientmechanism for transferring heat and mass in a system, such as the system 10. Anaperture, which in the embodiment shown in Figure 1 is an orifice 54, is providedin a wall 55 of the collection chamber 12 at some predetermined height from abottom 57 of the chamber 12. In some embodiments, the orifice 54 may begenerally rectangular with rounded corners, having a width of approximately 1-3centimeters (cm), and a height of approximately 1-10 cm, depending on the capacityof the system 10. As the amount (mass) of water collected by the desiccant 22 inthe collection chamber 12 increases, the level of the desiccant 22 in the sump 26 alsoincreases. When the level exceeds that of the orifice 54, some of the dilutedesiccant 22 in the collection chamber enters the regeneration chamber 14 and mixeswith the more concentrated desiccant 22 in the sump 52. In this way, no masstransfer from the collection chamber 12 to the regeneration chamber 14 occurs untilit is efficient—i.e., until the desiccant in the sump 26 reaches the predeterminedlevel.

In the regeneration chamber 14, the warm desiccant 22 loses wateras it is sprayed into the airflow 40; therefore, the level of the desiccant in the sump52 tends to decrease. An increase in the desiccant level in the sump 52 will occur,however, when the dilute desiccant 22 enters the regeneration chamber 14 throughthe orifice 54. Eventually, the level of the desiccant in the regeneration chamber 14will reach a maximum desired level. In order to control the mass transfer from theregeneration chamber 14 to the collection chamber 12, a level sensor is provided.In the embodiment shown in Figure 1, the level sensor is a float system 56. Thefloat system 56 includes a float 58, attached to an actuator 60, which operates avalve 62 between open and closed positions. In the embodiment shown in Figure1, the valve 62 is located downstream from a heat exchanger 64, the operation ofwhich is explained more fully below. In other embodiments, a heat exchanger, suchas the heat exchanger 64, may be downstream from the valve 62. PCT/IB2007/004333 WO 2008/053367

When the level of the desiccant 22 in the regeneration chamber 14reaches a first predetermined level, the float 58 causes the actuator 60 to facilitateopening of the valve 62. In the open position, the valve 62 allows some of thedesiccant 22 pumped by the pump 42 to be transferred back into the collectionchamber 12. In this way, the float system 56 controls the transfer of mass from theregeneration chamber 14 to the collection chamber 12. In the embodiment shownin Figure 1, the valve is an electro-mechanical device, such as a solenoid valve, andmovement of the actuator 60 actuates a switch that allows current to energi2e a collto open the solenoid. In other embodiments, the valve 62 may be mechanicallyconnected to the actuator 60, such that movement of the actuator 60 mechanicallyopens and closes (he valve 62. Other embodiments may use a non-contact levelsensor, such as a capacitive sensor, which are known in the art. When the level ofthe desiccant 22 in the regeneration chamber falls below a second predeterminedlevel, the actuator 60 causes the valve 62 to close. The first and secondpredetermined levels may be substantially the same, or they may be offset to providea hysteresis such that the valve does not open and close repeatedly for slightfluctuations in the desiccant level.

In addition to controlling the mass transfer, the system 10 alsocontrols the heat transfer between the two chambers 12, 14. In the embodimentshown in Figure 1, this is accomplished with the float system 56 in conjunction withthe heat exchanger 64. Although not shown in Figure 1, it is understood that theheat exchanger 64 can be connected, for example, by conduits 66, 68 to arefrigeration system, or other system that provides a flow therethrough to cool thedesiccant 22 as it is pumped through the heat exchanger 64. Cooling the desiccant22 before it is pumped back into the collection chamber 12 reduces the energy inputrequired into the heat exchanger 30. This provides an efficient control mechanismfor the transfer of heat between the chambers 12, 14.

Figure 2 illustrates a system 10' for managing the water content inair in accordance with another embodiment of the present invention, Elements ofthe system 10' are labeled with the same number as their respective counterparts inthe system 10, shown in Figure 1, and are further designated with the prime (') PCT/IB2007/004333 WO 2008/053367 symbol. As with the system 10, the system 10' includes collection and regenerationchambers 12', 14', each of which has its own heat exchanger 30', 46׳ forcontrolling the temperature of the desiccant 22'. Unlike the system 10, where thecollection and regeneration chambers 12, 14 were effectively abutted against eachother, the chambers 12', 14' in the system 10' are separated by a heat exchanger 70,the function of which is explained in more detail below,

To effect control of the mass and heat transfer between the twochambers 12', 14', the system 10' includes an orifice 54' in the collection chamber12'. When the level of the desiccant 22' in the sump 26' exceeds the level of theorifice 54', desiccant will flow from the collection chamber 12' to the regenerationchamber 14'. This controls mass transfer from the collection chamber 12' to theregeneration chamber 14'. Unlike the system 10, however, the desiccant 22' doesnot flow directly into the regeneration chamber 14', rather, it flows through the heatexchanger 70.

Like the system 10, the system 10' also includes a float system 56',having a float 58' and an actuator 60', which actuates a valve 62’. When the levelof the desiccant 22' in the sump 52' reaches a predetermined level, the float 58’moves the actuator 60', which opens the valve 62'. This allows desiccant 22' to bepumped from the regeneration chamber 14' to the collection chamber 12', andeffectively controls the mass flow.

To effect control of the heat transfer between the two chambers 12',14', the heat exchanger 70 is also used. As shown in Figure 2, the heat exchanger70 is connected to the valve 62', so that when the actuator 60' opens the valve 62',the warm desiccant from the sump 52' is pumped through the beat exchanger 70.As the cooler desiccant 22' passes through the heat exchanger 70 from the collectionchamber 12' on its way to the regeneration chamber 14', it picks up heat from thedesiccant 22' leaving the regeneration chamber 14'. In this way, the desiccant 22’entering the regeneration chamber 14' is warmer than when it left the collectionchamber 12', and the desiccant 22' entering the collection chamber 12' is coolerthan when it left the regeneration chamber 14'. This means that less energy is PCT/IB2007/004333 WO 2008/053367 required to respectively heat and cool the heat exchangers 46' 30', thereby resultingin an increase in efficiency, and overall energy savings. In other embodiments,multiple heat exchangers may be used, such as a combination of the heat exchanger64 shown in Figure 1 and the heat exchanger 70 shown in Figure 2. 5

While embodiments of the invention have been illustrated anddescribed, it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in the specification arewords of description rather than limitation, and it is understood that various changes10 may be made without departing from the spirit and scope of the invention. ;משפטים ה ודנו העתק שנסדק בשלמותו ביום ובשנה המצוינים; ממוחשבת מהימנה מהמסמך המצוי בתיק,לנוהל הבדיקות במשרד המשפטים.וס ;שרד המשפטים(חתימה מוסדית).