Abstract:
Apparatus and methods for transforming water vapor into potable water by using a vapor compression refrigeration system which includes first and second cooling elements disposed in a closed loop air passage duct that provides a continuous air circulation pattern driven by a fan or similar device. Water is introduced into the circulating air and undergoes adiabatic cooling followed by two stage cooling, first at a temperature below the dew point and then at a lower temperature at or below freezing. Water is collected from the air in each step and the air is thereafter heated back up by the condensing element of the refrigeration system enabling it to absorb more water vapor at the point of introduction. The air is recirculated and processed as above to permit cyclical water recovery.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to an improved apparatus for transforming atmospheric water vapor, or non-potable water vapor vaporized into air, into potable water, and particularly for obtaining drinking quality water through the formation of condensed water vapor upon one or more surfaces which are maintained at a temperature at or below the dew point for a given ambient condition. The surfaces upon which the water vapor is condensed are kept below the dew point by means of a refrigerant medium circulating through a closed fluid path, which includes refrigerant evaporation apparatus, thereby providing cooling of a bypassing airstream, and refrigerant condensing apparatus for providing heat to the airstream. 
   U.S. Pat. No. 5,301,516—Poindexter and U.S. Pat. Nos. 5,106,512 and 5,149,446—Reidy each disclose potable water collection apparatus comprising refrigeration apparatus to maintain a cooling coil at a temperature below the dew point to cause condensed water to form. Other prior art examples include U.S. Pat. No. 5,669,221—Le Bleu and Forsberg, wherein collected water or municipal water is simply filtered repeatedly until a desired potable quality exists. Other prior art examples for converting water vapor into liquid potable water exist within the public domain. U.S. Pat. No. 6,343,479—Merritt also discloses such techniques. 
   However, much of the above mentioned prior art is limited in scope to performing air to water conversion, thereby exhibiting an undesirable shortcoming. The prior art typically exhibits an inability to efficiently convert into water any quantity near the total amount of water vapor actually present in the atmosphere in the vicinity of surfaces maintained at temperatures below the dew point. The novel water production systems and methods disclosed herein are further capable of performing multiple functions such as water purification, desalination and distillation, as well as the task of converting moist air to water. The systems and methods disclosed herein will provide multiple functions at a substantial increase in efficiency with respect to the conventional techniques used for these functions, thereby overcoming shortcomings of the prior art and providing a much sought after solution to water quality problems which exist worldwide. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide novel means and methods for condensing and collecting water for drinking purposes from the atmosphere. It is a further object of the invention to provide means to purify water not yet fit for human consumption, thereby rendering the water safe to drink. It is yet a further object of the present invention to provide means and methods to distill ordinary water at relatively low ambient temperatures, thereby substantially reducing the energy costs normally associated with this task. These and other objects are fulfilled by employing sophisticated refrigeration techniques including multiple evaporators, adiabatic cooling techniques, reheat, as well as a novel defrost mechanism, all operating within an enclosed ducted air passageway. These techniques allow the apparatus to capture relatively large quantities of water, up to the greatest quantity of moisture per unit volume of air possible under a variety of conditions and situations. Upon determining whether the apparatus is to function as a simple air to water conversion device, a water distillation device, or desalination device, controls relevant to each separate operation may be activated in accordance with the present invention. 
   In accordance with one aspect of the invention, a method and apparatus for providing low temperature water distillation is as follows. A fan forces air through an enclosed air passage duct which is formed to allow for a continuous circulation pattern. The enclosed air duct or passageway preferably is insulated from exterior ambient temperature conditions. Water is introduced into the circulating air in the form of a fine mist which has an immediate effect known as adiabatic cooling. In this case, the adiabatic process is evaporative cooling. As the water vapor is absorbed into the air, energy is transformed from sensible heat into latent heat of vaporization. Accordingly, the temperature of the air falls, and its absolute humidity rises, while the overall energy content remains the same. The vapor laden air is then driven by the fan and passed across at least one surface of a first air stream cooling element which is maintained at a temperature below the dew point. The first cooling element causes a portion of the vapor in the air to convert into liquid water. As the air passes the first cooling element, it is cooled to reach one hundred percent relative humidity. The air stream is then passed across the surface of a second air stream cooling element. The second cooling element is operated at a temperature below the freezing point of water so that a very substantial percentage of the remaining water within the air stream is captured at the second cooling element. As the air stream passes beyond the second cooling element, it is again at one hundred percent relative humidity, though at a much cooler temperature. The air stream is then passed across an air stream heating element where the temperature of the air is drastically increased, simultaneously resulting in a significant drop in relative humidity. The air then returns through the insulated, enclosed ducted air passageway to the region of the backside of the fan which forces the air through the cycle again. At the same time that the airstream passes around the enclosed passageway in, for example, a counterclockwise direction, a refrigerant is passed around the corresponding loop of refrigerant elements in the opposite direction and the operating conditions associated with the refrigerant are controlled at each element to effect the desired temperature and pressure conditions. 
   This arrangement of adiabatic cooling, first and second cooling means, and air reheat, results in the capture of the greatest quantity of water possible in comparison to conventional techniques used for such tasks. Further, the task is accomplished with a significant decrease in energy usage, thereby resulting in higher efficiencies. An adjustable air damper may be positioned in the ducted passageway to control the inlet and exhaust of air into and out of the closed loop, this being determined by the particular function of the device, ambient conditions such as temperature and relative humidity, and pressures within the refrigerant circulating mechanism which control the temperature of the cooling and heating means. In the above described operation the damper is normally closed, completely isolating the air circuit from exterior ambient conditions. The water formed upon the cooled surfaces is collected and subjected, for example, to a germicidal lamp, then filtered through activated carbon to produce potable water as is known in other systems. 
   The foregoing and other aspects of the present invention will be described below, referring to the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic representation of a preferred embodiment of the present invention illustrating operational elements and their relative positions. 
       FIG. 2  is a standard psychrometric chart for water, with state points marked by alphabetic characters, illustrating selected information with reference to the detailed description of the invention. 
       FIG. 3  is schematic illustration of a section of an embodiment of the invention with particular reference to components which control temperatures of first and second cooling elements. 
       FIG. 4  is a schematic representation of an alternate embodiment of the invention illustrating air cooled de-superheating means. 
       FIG. 5  is a schematic representation of a system similar in certain respects to that described in my U.S. Pat. No. 6,343,479, granted Feb. 5, 2002 and further adapted to take advantage of certain characteristics of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , major components of the invention are positioned within a fully enclosed loop air passage duct  11 . In a preferred embodiment, duct  11  is insulated from ambient atmospheric conditions. A continuous flow of air containing water vapor (humidity), or into which moisture is injected (see below), is circulated through the closed loop air passage duct  11  by air movement means  12  such as a motor driven fan in, for example, a counterclockwise direction. A sequence of refrigeration components  14 ,  15 ,  16  is positioned within the duct  11  in ascending numerical order downstream from fan  12 . These refrigeration components comprise a first air stream cooling element  14  such as a first refrigerant evaporator having an exterior surface, a second air stream cooling element  15  such as a second refrigerant evaporator having an exterior surface, and an air stream heating element  16 , which in the preferred embodiment is a condenser of the refrigeration system. The refrigeration system further comprises a compressor  20  and first, second and third metering devices  21 ,  41 , and  22 , respectively. Refrigerant is supplied from compressor  20  to the several heating, cooling and control elements noted above. The state of the refrigerant medium is controllably altered to provide the desired temperature/pressure parameters around the loop. A suction pressure regulator  23  is provided which acts in concert with metering device  22  to cause the first cooling element  14  to operate at a selected pressure corresponding to a temperature below the dew point of the air being forced across the surface of cooling element  14 . At least a portion of the water vapor within the air moving across the surface of the first cooling element  14  condenses into liquid, thereby causing the passing air to cool (drop in temperature) while the humidity rises to 100%. The condensed liquid water is collected in a pan  24  and is passed to a storage vessel  25 . The second cooling element  15  is operated at a pressure corresponding to a temperature below the dew point of the air exiting the first cooling element  14  by controlling first metering device  21 . Preferably, second cooling element  15  is operated at a temperature below the freezing point of water so that substantially all or a large percentage of the remaining water (vapor) in the air stream is captured at the second cooling element  15 . 
   Referring to  FIG. 3 , metering devices  21  and  41  as well as metering device  22  are illustrated as capillary tubing. Controlling this type of metering device consists of determining the correct ratio between the length of the tubing and inside diameter of the tubing. Extremely accurate pressure and temperature relationships are attainable using this dimensioning technique. Other types of metering devices can be used instead. The preferred operating temperature of second cooling element  15  is below the freezing temperature of water. In fact, temperatures down to 0° Fahrenheit (F) are not undesirable for second cooling element  15 . It should be understood that first cooling element  14  and second cooling element  15  may be combined within a single physical structure, thereby creating a multiple temperature refrigeration evaporator element, as well as reducing the part count. A damper  18  is positioned preferably between heating element  16  and fan  12 . Damper  18 , when opened, creates an inlet port  30  and an outlet port  31  which are useful during certain tasks performed by the apparatus, such as simple atmospheric air to water conversion. 
   Referring now to  FIGS. 1 and 2 , specific examples of operating parameters and conditions according to the invention will be described. As shown in  FIG. 2 , at state point A, when the dry bulb temperature of the air flowing in duct  11  upstream of first cooling element  14  is 80° F., with a relative humidity (RH) of 60%, 0.0132 pounds of water per pound of dry air will be present. Using this same  FIG. 2 , it can be determined that 13.90 cubic feet of air corresponds to one pound of air. By circulating three hundred cubic feet per minute (CFM) of air in air passage duct  11 , twenty-one and one half (21.5) pounds of air per minute will be moving across the surface of the first cooling element  14 . The amount of water vapor contained in this amount of air is 0.0132×21.5=0.28 pounds or nearly ⅓ pound of water per minute, which will be passing over first cooling element  14 . The dew point for this condition is 64.9° F. By adjusting the suction pressure regulator  23 , the circulating refrigerant in first cooling element  14  is set to operate, for example, at 40° F. It can then realistically be expected that a twenty-five degree drop in temperature will result and the air will be cooled to a temperature such as 55° F. when it passes over first cooling element  14 . 
   At least a portion of the 0.28 pounds per minute of water vapor in this air will condense into liquid water upon the surface of first cooling element  14 . This portion of water can be calculated by subtracting from the amount of water entering duct  11  which has been previously calculated to be 0.0132 lb./lb. of air. The amount of water available at the temperature the air was cooled to, shown at state point B where the air leaving the evaporator  14  is saturated or 99.9% RH, is 0.0092 lb./lb. This calculation indicates that only 0.004 lb./lb. is captured. Multiplying this number by 21.5 pounds of air per minute means that out of 0.28 pounds per minute that is available, only 0.086 pounds per minute is being captured. Continuing, from state point B where the dew point is 55° F., this saturated air is forced across the surface of second cooling means  15  which is controlled to operate at 0° F. (below the freezing point of water). As the moisture laden air makes contact, the moisture freezes upon the surface of the second cooling means  15  and the air is cooled to 20° F. This is represented as state point C on the psychrometric chart of  FIG. 2 , where it can also be seen that the amount of water is only 0.0021 pounds per pound of air at this point. A new calculation similar to the previous calculation reveals the amount of water captured is 0.0111 lb./lb., nearly all of what was available in the air upstream of the first cooling element  14 . As the second cooling element  15  begins to accumulate ice, thereby restricting the flow of air through the enclosed circuit  11 , the temperature of suction line  23  decreases. This temperature decrease is sensed by a temperature sensing switch  40  which closes, energizing a valve  19  which then opens and allows liquid refrigerant to pass through the second (a parallel connected) metering device  41 . This connection has the immediate effect of an increase in pressure within the second cooling element  15 . Therefore an immediate increase in temperature occurs and the ice on second cooling element  15  begins to melt. This method of defrosting is superior to a hot gas defrost method common in the art of refrigeration since it uses less moving parts and assures the surfaces of the cooling elements are always maintained below the dew point of 55° F. of the entering saturated air as well. As the ice melts, the temperature of second cooling element  15  begins to approach the temperature of the first cooling element  14 . At this point, a temperature sensing switch device  40 , sensing the increase in temperature, opens; de-energizing valve  19 . Once again refrigerant is allowed to flow only through metering device  21 , reducing the temperature of the second cooling element  15  substantially. The resultant water from the melted ice is collected in drain pan  24  and directed to storage vessel  25 . The cooled air continues flowing through the duct  11  and is now directed across the surface of heating element  16  where the temperature of the air is raised to 90° F. This air is exhausted at port  31  as damper  18  is fully opened for this particular task, thereby obstructing the heated air from returning through the duct  11  to the air movement means  12 . 
   Referring to  FIG. 1  and  FIG. 3 , an alternate technique of water distillation at low temperatures is described. In this operation, damper  18  is fully closed, thereby creating a completely closed air circuit  11 . As fan  12  forces air to move throughout the closed air passage duct  11 , water in the form of a fine mist or fog is introduced into the air stream through a water introduction means  13  (for example, a spray nozzle or the like). This water need not be of a potable nature and can be brackish or salt water. A replaceable particulate filter  13   a  assures no foreign matter enters the introduction means  13 . As this water is introduced into the circulating air in the form of a fine mist, there is an immediate effect known as adiabatic cooling. The term adiabatic refers to a change of state without loss or gain of heat energy. In this case, the adiabatic process refers to evaporative cooling. Evaporative cooling can occur when air passes over the surface of water. Even at temperatures well below the boiling point, water molecules at a surface will absorb sufficient energy from passing air to change phase into gas and become water vapor. As the water vapor is absorbed into the air, energy is transformed from sensible heat into latent heat of vaporization. Accordingly, the temperature of the air falls, and its absolute humidity rises, while the overall energy content remains the same. Thus, as the water spray makes contact with the air stream, adiabatic cooling takes place. The temperature of the air stream drops and the absolute humidity rises. A water entrainment means  17  positioned between the water introduction means  13  and the first cooling means  14  assures no droplets of water are allowed to pass beyond this point. If the temperature of the air stream was 90° F. before contact with the water, it is not uncommon for a twenty degree reduction in temperature to occur. Therefore, the new condition of the air stream is 70° F. and nearly completely saturated. This means that the dew point for this condition is near 70°. As in the previous example, the same phenomena occur. That is, the vapor laden air is driven by the fan  12  and passed across at least one surface of a first cooling element  14  which is maintained at a temperature below the dew point. The first cooling element  14  causes a portion of the vapor in the air to convert into liquid water. As the air passes the first cooling element  14 , it is cooled to reach one hundred percent relative humidity. This is the customary condition for air after having passed over a refrigerant evaporator. At this point the air contains all of the moisture not captured by the first cooling element  14 . The air stream is then passed across the surface of a second cooling element  15 . The second cooling element  15  is operated at a temperature below the freezing point of water so that substantially all of the remaining water within the air stream is captured at the second cooling element  15 . As the air stream passes beyond the second cooling element  15 , it is again at one hundred percent relative humidity, though at a much cooler temperature. The air stream is then passed across a heating element  16  where the temperature of the air is drastically increased, simultaneously resulting in a significant drop in relative humidity. The air then returns through the insulated, enclosed ducted air passageway  11  to the fan  12  which forces the air through the cycle again, including the water injection or introduction step. This arrangement of adiabatic cooling, first and second cooling means, and air reheat, results in the capture of the greatest quantity of water possible in comparison to conventional techniques used for such tasks. Further, the task is accomplished with a significant decrease in energy usage, thereby resulting in higher efficiencies, with the result being a significant amount of captured water. By increasing the temperature from 20° F. leaving the second cooling element  15 , to 90° F. by heating element  16 , gives a new condition of 7.5% RH; extremely dry air with a great affinity for water. Since damper  18  is fully closed the air continues to circulate and again the method of moistening air, adiabatically cooling it, subjecting the adiabatically cooled air stream to multiple temperature evaporators thereby significantly drying it, then raising the temperature of the air stream creating an air stream of extremely low relative humidity, is performed in a continuously repeated cycle until the desired amount of water is collected. The water is stored in vessel  25  and subjected to filtering and disinfecting as is common in the art. In extremely hot and dry climates the damper may be adjusted to open to a certain degree during this operation thereby moderating the conditions within the refrigeration components. 
   Referring to  FIG. 4 , an alternate embodiment of the invention is shown in which means to pre-cool or de-superheat refrigerant supplied from a compressor  20  is illustrated. In general, the apparatus shown in  FIG. 4  is substantially the same as that shown in  FIG. 1  with the exception that air supplied by a further fan  20   b  disposed outside the enclosed air passage loop  11  is supplied across a condenser segment  20   a  to provide an air-cooled de-superheater which provides a somewhat similar effect on the circulating refrigerant as the water-cooled de-superheater shown in my U.S. Pat. No. 3,643,479 mentioned above. 
   Specifically, in  FIG. 4 , vapor compressor  20  is in fluid communication with air cooled de-superheater  20   a . Refrigerant is caused to flow out of compressor  20  into de-superheater  20   a  where air supplied by a second air movement device (e.g. a fan)  20   b , which is disposed outside of closed air loop  11 , removes the superheat from the refrigerant. It has been found to be advantageous to use a controllable speed fan  20   b  in order to be able to further control the temperature of condenser  16  and thereby more accurately control temperature of the air within air duct  11 . On-off time control of fan  20   b  similarly may be used to control air temperature within duct  11 . De-superheated refrigerant then flows into condenser  16  where the remainder of the heat content is removed by the air flow within closed loop  11  passing over condenser  16 . This causes the refrigerant to condense completely into liquid form. The liquid refrigerant passes through metering devices  41 ,  21 ,  22 , as explained previously, into controlled temperature/pressure regions of evaporators  15  and  14 , respectively, in order to collect and remove water supplied by water insertion means  13  from the circulating air within closed loop  11 , again as explained above. 
   It can therefore be seen that  FIG. 4  is similar to  FIG. 1  in many respects and the same reference characters have been used in both figures to identify the same or similar parts. 
   Referring to  FIG. 5 , rather than the air cooled de-superheater arrangement  20   a ,  20   b  of  FIG. 4 , a similar function is provided by a water cooled de-superheater  20   a ′ of the type shown in my earlier U.S. Pat. No. 6,343,479 mentioned above. The flow of cooling water for the de-superheater and its recovery is described in my &#39;479 patent and is incorporated herein by reference. In the  FIG. 5  arrangement, only a single evaporator element  14  is shown. However, it should be recognized that, as was mentioned previously, evaporator element  14  may, in fact, be a combination of evaporator elements  14  and  15 , along with the associated control devices described in connection with  FIG. 1 . Furthermore, the coolant water circulated in de-superheater  20   a ′ may be coupled to the water introduction means  13  to provide the desired water vapor in closed loop  11 . In addition, all of the air-cooled de-superheater elements included in  FIG. 4  may be coupled into the system shown in  FIG. 5 , with the elements  20   a  and  20   a ′ being connected in series in the refrigerant path from compressor  20 . In this way, the appropriate one of the de-superheaters may be operated while the other is not, according to the desired conditions of operation. 
   The aforementioned tasks of simple air to water conversion, as well as low temperature water distillation and desalination are all tasks which are well within the capabilities of the above described inventive combinations. 
   Accordingly, while one or more preferred embodiments of the present invention are illustrated and described herein, it will be understood the invention may be embodied otherwise than as herein specifically illustrated or described and that within the embodiments certain changes in the details of construction, as well as the arrangement of parts, may be made without departing from the principles of the present invention as defined by the appended claims.