Abstract:
The system that operates in a zero gravity environment and has an integral ozone generating capability is disclosed. The system contributes to the control of metabolic water vapors in the air, and also provided disinfection of any resulting condensate within the system, as well as disinfection of the air stream that flows throughout the disclosed system.

Description:
The invention described herein was made by an employee of the United States Government and may be used by or for the Government for governmental purposes without payment of any royalties thereon or therefor. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a heat exchanger. Specifically, the invention is a system that provides condensing, cooling, filtering, humidifying and disinfecting for selected environments and is particularly suited to supply life support for astronauts that includes the treatment and revitalization of the air that the astronauts breath. The system provides an ozone generator to correct for air contamination problems encountered in closed environments, such as in the space capsule or planetary outposts, but also encountered in commercial and terrestrial applications. The system improves the quality of air people breath, which has become an important health issue. 
     BACKGROUND OF THE INVENTION 
     Life support for astronauts includes the treatment and revitalization of the air that the astronauts breathe. Part of the revitalization is the removal of the excess water vapor from the air. This excess water vapor is a result of the natural metabolic production of water, and it is exhausted into the air by the astronaut&#39;s respiration and perspiration. The condensation of water in zero gravity and its separation from the remaining gaseous phase while in a zero gravity environment is technically challenging and requires a solution. In addition to the condensing and gas/liquid separation problem, there is the problem of biological fouling of the condensing/separation mechanism, being employed as part of the life support system, due to deposition and subsequent growth by microorganisms on the condensing surface of the condensing/separation mechanism. Not only does this fouling potentially reduce the effectiveness of the condenser/separator, but also represents a contamination point for the astronauts&#39; water system. 
     The problem of condensing the water vapor from humidity laden air in a zero gravity environment is very similar to the problem of removing the liquid water from a two-phase fuel cell gas circulation stream. Several solutions to the fuel cell problem have been implemented and include: centrifugal separators, porous media, and membrane separators. 
     Centrifugal separators (both rotating and non-rotating) operate by imparting an acceleration to water droplets, and since the water drops are denser than the surrounding gas, they are “spun” separated from the gas being treated by the centrifugal separators. If the centrifugal separators are rotating, they consume power, if non-rotating their operation is flow rate dependent. The centrifugal separators are also most susceptible to dry-out conditions. However, the centrifugal separators are the least susceptible, compared to the porous media and membrane support, to fouling or plugging because the treated water does not get squeezed through tiny pathways found in porous media and membrane support devices. Scaling, that is adapting the centrifugal separators to different applications, is the most difficult of the three different type solutions. 
     Porous media (sintered metal, plastic or ceramic particles) operate by absorbing the condensate on a surface of interest, and by a combination of capillary forces and bulk pressure differential to transfer of water from a higher pressure gas/liquid side to a lower pressure liquid only side. The materials (sintered metal, plastic or ceramic particles) must be either inherently hydrophilic or treated to make them hydrophilic in order for a required absorption process to work. These porous media separators are considerably thicker than membrane separators, and therefore are far more resistant to water flow. This means that these separators must be sized larger, or have a greater delta P, known in the art, for driving the water through the separators than that required for membrane technique. However, the porous media technique scales easily, but unfortunately is susceptible to fouling. Furthermore, the porous media devices are generally much heavier than typical membranes, but are easily shaped into different geometries (cylindrical, planar, etc.). 
     Membrane separators (hydrophobic, hydrophilic, or both in combination) are very similar to the porous technique employing porous media for removing water from a two-phase fuel cell gas, but are far less flow restrictive, and therefore can be made much smaller/lighter for a given water removal rate. The membrane separator can be made to operate with low delta P. The membrane separators also scale easily, but also foul just as easily as porous media. Advantageously, the membrane separators can be made into pleated cylindrical or planar geometries. The hydrophobic type of the membrane separators operate by allowing gas to flow through the hydrophobic membrane, but not liquid. Conversely, the hydrophilic type of membrane separators allow liquid to pass, but not gas. These hydrophilic membranes are typically plastic, but sometimes are thin deposited layers of either metals, plastics or ceramics on a thicker supporting substrate. It is desired to incorporate the beneficial features of the hydrophilic membrane and centrifugal separators into a system that corrects for the problem of condensing water vapor from humidity laden air in a zero gravity environment. It is further desired to provide a system that provides purifying, condensing, filtering and humidifying functions for the Zero-G life support system for astronauts, as well as for home and office building air conditioning apparatuses, airplane air systems, automobile air systems, room humidifiers and room air cleaners. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide a system for condensing, cooling, filtering, humidifying, and disinfecting selected environments, and is particularly suited for supplying life support for astronauts, including the treatment and revitalization of the air that the astronauts breathe in a zero gravity environment. 
     It is another object of the present invention to provide a system having an ozone generator that produces ozone at the surface of the condenser of the system, thereby disinfecting the condensed water, as well as disinfecting the air stream impacting the condensing surface. 
     Further, it is an object of the present invention to provide a system whereby the thermal path length between the coolant and air stream channels within the system is minimized, which, in turn, minimizes the temperature differential between the coolant and the air stream and, accordingly, improves the efficiency of the system itself. 
     Still further, it is an object of the present invention to provide a planar flow geometry for the air stream within the system and to provide turbulence for the flow path which assists in moving water droplets from the air being treated in a manner similar to that of a centrifugal separator, as well as removing heat from the air stream. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a system for condensing, cooling, filtering, humidifying and disinfecting selected environments. The system comprises a) a cavity capable of holding water and occupied by a support screen having an upper surface; b) hydrophilic membrane arranged on the upper surface of the support screen; c) a plurality of adjacent and interconnected air channels formed in a material of relatively high thermal conductivity and relatively low density. The plurality of air channels are arranged to cover the hydrophilic membrane. The system further comprises (d) a plurality of adjacent and interconnected coolant cavities formed in the material having the relatively high thermal conductivity and the low density and arranged above the plurality of air channels; and (e) an ozone generator arranged in at least one of the air channels and located over the hydrophilic membrane. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and the advantages of the invention, as well as the invention itself, will be better understood with reference to the following description when considered in conjunction with the accompanied drawings, where like reference numbers designate identical corresponding parts thereof and wherein: 
         FIG. 1  is a block diagram of the system of the present invention; 
         FIG. 2  illustrates one embodiment of the present invention being a circular arrangement of the planar air/water separator of the system of the present invention; 
         FIG. 3  is a cross-sectional, view taken along line  3 - 3  of  FIG. 2 , of the planar air/water separator; 
         FIG. 4  illustrates the hydrophilic membrane of the present invention; 
         FIG. 5  illustrates a family of curves showing, among other things, a pressure drop liquid flow characteristic of the hydrophilic membrane of  FIG. 4 ; 
         FIG. 6  is cut-way view of the planar air/water separator of the present invention; 
         FIG. 7  is a cross-sectional view of the planar air/water separator of the present invention, particularly showing one of the features of the present invention of water droplets being spun outward and toward the hydrophilic membrane of the present invention; 
         FIG. 8  is a cross-sectional view of the planar air/water separator of the present invention, illustrating an ozone layer generated by the ozone generator of the present invention that eliminates the biological growth on the hydrophilic membrane of the present invention so as to disinfect the condensate and purifying the air stream with the system of the present invention; and 
         FIG. 9  is a cross-sectional view of the electrochemical ozone generator of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , there is shown a block diagram of the system  10  of the present invention for condensing, cooling, filtering, humidifying, and disinfecting selected environments and is particularly suited for the treatment and revitalization of air that astronauts breathe in a zero gravity environment condition. Further, the system  10  may be advantageously utilized for a large variety of applications, such as for home and office buildings air conditioning systems, airplane air systems, automotive air systems, room humidifiers and room air cleaners. The system  10  comprises an air/water separator  12  and an ozone generator  14 . The air/water separator  12  comprises an upper housing  16  and a lower housing  18 . 
     The upper housing  16  has provisions  20  and  22 , known in the art, for respectively receiving a coolant input  24  and for transporting a coolant output  26 . Further, the upper housing  16  has provisions  28  and  30 , known in the art, for respectively receiving air input  32  and for transporting air output  34 . The lower housing  18  has provisions  36 , known in the art, so as to transport and remove water therefrom along a water path or side  38 . 
     As will be further discussed, the pressure head of the air stream within the air/water separator is relatively low. Accordingly, it is desired to provide suction on the water side  38  of the lower housing  18 , so as to move condensate through the air/water separator  12  and into the water path  38 . The suction may be applied by a spring loaded bellows  40 . Solenoid valves  42  and  44  are preferably provided to isolate the system  10 , during the filling and emptying operations of the system  10 . The water path  38  passes through the solenoids  42  and  44  and into water line  46 , which, in turn, passes through valve  48  onto line  50  and is shown in  FIG. 1  as water out  52 . The air/water separator  12  may be further described with reference to  FIG. 2 . 
     The air/water separator  12  may have any shape that conforms to the application being used. For example, for the embodiment of  FIG. 2 , the air/water separator  12  has a curved configuration and partially shows the upper and lower housing  16  and  18  respectively. The air/water separator  12 , may be further described with reference to FIG.  3 , taken along lines  3 - 3  of  FIG. 2 , and showing a cross-sectional view of the planar air/water separator  12 . 
     The planar air/water separator  12  comprises a cavity  54  capable of holding water and which is occupied by a water cavity support screen  56 , known in the art. A hydrophilic membrane  58  is arranged on the upper surface of the water cavity support screen  56 . 
     The air/water separator  12 , in particular, the upper housing  16  is dimensioned, so as to provide for plurality of adjacent and interconnected air channels  60  therein, all in fluid communication with each other. The plurality of air channels  60  are arranged to cover the hydrophilic membrane  58 . The upper housing  16  is further dimensioned so as to provide for a plurality of adjacent and interconnected coolant cavities  62  therein, which are in fluid communication with each other. The upper housing  16  is further provided with a cover  64  that is placed over the plurality of coolant cavities  62 . 
     The air/water separator  12  has a planar flow geometry for the air stream and is capable of being stacked or arranged, as shown in  FIG. 3  in a side-by-side manner, to allow for easy scaling of the system  10 . More particularly, the number of air channels  60  and coolant cavities  62  may be selected to adapt the air/water separator  12  to the air circulation requirements for the various applications, such as home and office building air conditioning systems, airplane air systems, automobile air systems, room humidifiers and room air cleaners. 
     The upper housing  16  is selected to be of a relatively high thermal conductive material that also has a relatively low density, so as to minimize mass. The material may be selected from the group comprising aluminum, magnesium, titanium, metal filled or carbon filled plastics, and high thermal conductivity carbon composites. Other materials can also be used wherein the properties of the materials are selected to only effect the mass and temperature of the coolant. It is not essential to the principles of the invention that only certain materials be used. 
     The selection of the material for the upper housing  16  allows the air stream flow in the air channels  60  to be provided with a thermal path, between the coolant in cavities  62  and the air channels  60 , which is minimized or reduced, which, in turn, minimizes the temperature differential between the coolant and the air streams, so as to enhance the overall efficiency of the air/water separator  12 , which, in turn, enhances the overall efficiency of the system  10 . The upper housing  16  acts essentially as a liquid/air heat exchanger. The hydrophilic membrane  58 , located below the air channels  60 , may be further described with reference to  FIG. 4 . 
       FIG. 4  shows the hydrophilic membrane  58  as having a circular shape, microscopic-sized accommodating the embodiment of  FIG. 2 , a thickness  66  and a plurality of microscopic-sized pores  68 . The pores  68  are shown in  FIG. 4  as being circular for the sake of clarity, but in actuality the pores  68  are irregular shaped and act as passageways through a tangled web of polymer fibers that are also highly irregular in shape. The hydrophilic membrane  58  is commercially available and its pores size is selected to minimize the pressure drop of water transported through the hydrophilic membrane  58 , yet has a sufficient bubble pressure to provide robust resistance to gas flow through the membrane  58 . The hydrophilic membrane  58  may be of a plastic material having a thickness  66  of 0.0052 inches, and having a nominal pore size rating of 0.8μ. The selection of hydrophilic membrane  58  allows for minimization of both size and mass. The plastic hydrophilic membrane  58  also has a bubble point, given in pounds/square inch differential psid, of about 15. The benefits of the plastic hydrophilic membrane  58  relative to a prior art stainless steel membrane may be further described with reference to  FIG. 5 . 
       FIG. 5  shows a family of curves  70  illustrating the response of a stainless steel sinter membrane and a plastic membrane of the liquid flow, given in gallons per minute per square foot (gpm/ft 2 ), vs. pressure drop common given in psid. The family of curves  70  include responses  72  and  74 , which are respectively those of a stainless steel sinter membrane and the plastic membrane  58 . The stainless steel sinter is of a medium grade: 0.2μ, has a thickness of 0.039 inches, and a bubble point, given in inches of mercury (in Hg) of 5-6.9. A comparison between the two responses  72  and  74  reveals that the plastic membrane  58  of response  74  offers greater flow at the same delta P or less delta P at the same flow. Delta P is the pressure difference between two sides of the membrane  58 . Delta P is sometimes referred to as differential pressure. Further, the plastic membrane associated with response  74  is thinner, lighter and has a much higher bubble pressure relative to the stainless steel sinter membrane related to response  72 . The plastic membrane  58  may be used in condensing heat exchangers and in air conditioners of any capacity. The air/water separator  12  housing the plastic hydrophilic membrane  58 , may be further described with reference to  FIG. 6 , which is a cut-away view of the planar air/water separator  12 . 
       FIG. 6  shows input and output manifolds  76  and  78 , which are part of the provisions  20  and  22 , previously mentioned with reference to  FIG. 1 , input and output manifolds  80  and  82 , which are part of the provisions  28  and  30 , previously mentioned with reference to  FIG. 1 , and common water manifolds  84  and  86 , which are part of the provisions  36 , previously mentioned with reference to  FIG. 1 . 
       FIG. 6  also illustrates the plurality of adjacent and interconnected coolant cavities  62 , all having fluid communication therebetween and arranged in a side by side manner. Further,  FIG. 6  illustrates, for one embodiment, a spiral pattern of the air channels  60 , all interconnected to provide communication therebetween. The spiral pattern creates radial acceleration of the air flow that assists in the separation of the water droplets from the air flow, to be further described hereinafter. Some of the benefits provided by the air/water separator  12 , may be further described with reference to  FIG. 7 , which is a cross-sectional view of the planar air/water separator  12 . 
       FIG. 7  illustrates, in a general outline, one of the air cavities  60 , which is positioned over part of the hydrophilic membrane  58 , which has a film  88  thereon.  FIG. 7  further illustrates a horizontal directional arrow  90 , and a vertical directional arrow  92 , both of arrows  90  and  92  being associated with a plurality of water droplets  94 . 
     As seen in  FIG. 7 , the water droplets  94  are “spun” outward, as indicated by directional arrow  90  and toward, as indicated by directional arrow  92 , the hydrophilic membrane  58  resulting in a peaked shape fluid portion  96 , shown in  FIG. 7 . 
     The air channels  60  provide changes in a direction of the flow path within the air channels  60  that imparts acceleration, which assists in separating water droplets  94 , as shown in  FIG. 7 . Changes in the width and depth of the air channels  60 , known in the art to create turbulence, also imparts acceleration which assists in separating water droplets  94 . The separation is accomplished while minimizing the difference between the air inlet pressure and air outlet pressure. The imparted accelerations assist in moving the water droplets  94  to the surface of the hydrophilic membrane  58 , in particular, to the film  88  and into the peaked portion  96 . The turbulence in the air channels  60  also enhances heat transport from the air in the air channels to the cooled walls of the coolant cavities  62 . A further benefit of the system  10 , in particular, the ozone generator  14 , may be further described with reference to  FIG. 8 , which is a cross-sectional view of the planar air or water separator  12 . 
       FIG. 8  is similar to  FIG. 7 , with the exception that the directional arrows  90  and  92  are removed, as well as the water droplets  94  not being present, but rather a directional arrow  98 , is shown in  FIG. 8 , in contact with a layer of ozone  100  which, in turn, is in contact with the film  88 . An ozone generator, such as an electrochemical ozone generator  14 , to be further described with reference to  FIG. 9 , generates an ozone layer  100 , which prevents biological growth on the hydrophilic membrane  58 , while also disinfecting the condensate, as well as disinfecting and purifying the air stream flowing with the plurality of air channels  60 . The electrochemical ozone generator  14 , may be further described with reference to  FIG. 9 , which is cross-sectional view of the ozone generator  14  of  FIG. 1 . 
     Under normal operating conditions, the air/water separator  12 , more particularly, air stream flowing in air channels  60  will likely contain microscopic particle matter, as well as biological contamination that would otherwise foul the air/water separator  12 . The electrochemical ozone generator  14  of  FIG. 9 , provides the anti-fouling correction. The electrochemical ozone generator  14  performs an electrolytic process in which electrical energy is applied to cause a chemical change, similar in a manner as described in U.S. Pat. No. 4,416,747 (&#39;747), which is herein incorporated by reference in its entirety. 
       FIG. 9  illustrates a electrochemical ozone generator  14  comprised of a cathode  104 , an anode  106 , and an ion exchange membrane  108  interposed between and separating the cathode  104  and the anode  106 . The cathode and the anode  104  and  106  respectively, are connected to an electrical source  110 . More particularly, the cathode  104  is connected to the negative potential  112  of the electrical source  110 , whereas the anode  106  is connected to the positive potential  114  of the electrical source  110 . 
     The cathode  104 , anode  106 , and ion exchange membrane  108  are dimensioned, so as to fit into at least one of the air channels  60  (not shown) and cover a portion of the plastic hydrophilic membrane  58 . The anode  106  and cathode  104  are preferably made of stainless steel, and the ion exchange membrane  108  is preferably made of a plastic polymer based on perfluorinated sulphonic acids. The ion exchange membrane  108  may be coated on the cathode side with a layer of a mixture of 85% by weight carbon powder and 15% by weight platinum powder. The anode side of the ion exchange membrane  108  may be coated with PbO2 powder. A ion generator  14  causes ozone to be produced in the solution on the anode side of the ion exchange membrane  108 , while water is formed on the cathode side thereof. The H+, which is produced on the anode side by the decomposition of water to form oxygen and ozone (0 2 , 0 3 )  120 , shown in  FIG. 9 , migrates through the ion exchange membrane  108  and reacts with oxygen in the water on the cathode side to form water. 
     The electrochemical ozone generator  14  generates anode and cathode reactions given below:
 
Anode Reaction(s)
 
3H 2 O→O 3 ( g )+6 e   − +6H + 
 
O2+H 2 O→O 3 ( aq )+2 e   − +2H + 
 
2H 2 O→O 2 +4 e   − +4H + 
 
Cathode Reaction
 
O 2 +4 e   − +4H + →2H 2 O
 
     In operation, the hydrophilic membrane  58  providing a condensing separating surface together with an in-situ electrochemical generation of ozone  14  at the condenser surface, which provides for disinfection of the air stream traveling in air channels  60 . In the operation of system  10 , the hydrophilic membrane  58  is cooled below the ambient dewpoint by a coolant flowing in the coolant cavities  62  and made available from a coolant source. 
     The moisture laden ambient air impacting the surface of hydrophilic membrane  58 , in particular film  88 , condenses water on the surface of the hydrophilic membrane  58 . This water is soaked up through the hydrophilic membrane  58  and transported through the hydrophilic membrane  58 , as well as through the screen  56 , and into the water line  38  leaving the air/water separator  12 . 
     During the above process, the electrochemical ozone generator  14  located on the air side of the hydrophilic membrane  58  creates a local concentration of ozone layer  100  in the condensed water, thereby disinfecting it. Excess ozone not absorbed by the water is exhausted into the air stream where it would contribute to the disinfection and purification of the air stream flowing in the air channels  60 . 
     It should now be appreciated that the practice of the present invention, in one embodiment, provides a system  10  for treatment and revitalization of air for astronauts operating in a zero gravity environment. The system  10  may also provide a revitalization of air that is used in home and office building air conditioning systems, airplane air systems, automotive air systems, room humidifiers, and room air cleaners. 
     The invention has been described with reference to preferred embodiments and alternates thereof. It is believed that many modifications and alterations to the embodiment as described herein will readily suggest themselves to those skilled in the art upon reading and understanding the detailed description of the invention. It is intended to include all modifications and alterations insofar as they come within the scope of the invention.