Abstract:
A humidifier of the present invention includes a bundle of hollow porous tubes made of synthetic material disposed in a housing having a plurality of inlet and outlet ports. The humidifier of the present invention is used to control humidity in a fuel cell and is used in various industrial applications. A method of producing the humidifier is disclosed herein.

Description:
RELATED APPLICATIONS  
       [0001]     This non-provisional application claims priority to a provisional application Ser. No. 60/817,991 filed on Jun. 30, 2006 and incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a humidifier for a fuel cell systems, and specifically to the humidifier utilizing hollow fibers and a method of forming the same.  
       BACKGROUND OF THE INVENTION  
       [0003]     A typical fuel cell presents is an electrochemical energy conversion device for producing electricity from external supplies of fuel and oxidant in the presence of an electrolyte. Generally, the reactants flow in and reaction products flow out while the electrolyte remains in the fuel cell. One of the benefits of the fuel cell over, for example, a battery, is the ability of the fuel cell to operate virtually continuously as long as necessary flows are maintained. Unlike the battery, which store electrical energy chemically in a closed system, the fuel cells consume reactants, which must be replenished. Additionally, while the electrodes within the battery react and change as a battery is charged or discharged, the electrodes of the fuel cell are catalytic and relatively stable.  
         [0004]     Alluding to the above, the fuel cells generate electrical power that can be used in a variety of applications. One of the most reliable types of the fuel cell is a proton exchange membrane (PEM) fuel cell. The core element of modern PEM fuel cell is the membrane electrode assembly (MEA) including the ion exchange membrane, which acts as a solid electrolyte and thin catalytic layers deposed on both sides of the membrane acting as anode and cathode electrodes. The PEM fuel cell gas diffusion layers (GDL) support MEA and distribute reactants to the electrodes and flow plates directing reactants and an electrical current. To produce electricity through an electrochemical reaction, hydrogen-rich fuel is supplied to the anode (mainly the hydrogen) and the oxidant gas (mainly the air) is supplied to the cathode.  
         [0005]     An electrochemical reaction between hydrogen and the oxygen contained in the air produces the electrical current, water and heat as the reaction products. Water is removed from the cathode to make the catalytic layer accessible for the oxygen. On the other hand, the air introduced to the cathode supposed to be rich in water vapor to prevent drying out of the PEM, which results in failure of the fuel cell failure. In some fuel cell systems the hydrogen, delivered to the anode, is also subject for humidification. A humidifier of the fuel cell presents the main device to keep the correct water balance in the fuel cell, thereby transferring the moisture across an internal membrane permeable for water molecules from water carrier to gas introduced into the fuel cell as the reactant. The major sources of water intended for the humidification are DI water or an exhaust gas from the fuel cell cathode.  
         [0006]     Alluding to the above, a dialyzer, as know to those skilled in the art, utilizes membranes of various designs, fabricated from polysulfone, polycarbonate, polyamide, and the like. The high chemical stability and sufficient mechanical durability of these materials allow to the differential pressure commonly used in the hemodialysis, which can exceed 10 psi thereby allowing to re-process the reusable dialyzer. The membrane presents a micro-porous structure and does not expand to the same degree as hygroscopic membranes because water fills the voids in the material instead of creating swelling or volume displacement.  
         [0007]     For the humidification process the most acceptable dialysis membrane is low flux type having the lowest permeability (10 ml/hr/mmHg) to prevent the mixing the reactant with liquid water, (in case of humidification by means of water) or with humid exhaust gas (gas to gas humidification). A dialyzer can be modified in a manner that it can be applicable as a humidifier for fuel cell systems and other applications wherein air humidification is required. The use of a properly modified dialyzer advantageous in that it is a widely distributed and inexpensive device. A humidifier design is highly dependable on the application of a fuel cell system, its concept, etc.  
         [0008]     The art is replete with various humidifier designs as taught by the U.S. Pat. No. 4,801,385 to Sachtler et al. and the U.S. Pat. No. 4,381,267 to Jackson. One of the most effective membrane package is presented by a multitude of hollow tubes arranged in a bundle inserted into a housing wherein the ends of the tubes encapsulated in a resin. The typical membrane type used in the fuel cell humidifiers is Nafion®. Water transport between fluid streams in these humidifiers occurs via a hygroscopic polymer, whose water absorption properties are due to chemical affinity. Although effective humidification is accomplished with these devices, several detriments exist to their use. Among these is the issue of polymer expansion with water uptake, which results in a fragile, failure prone device. During operation, Nafion® polymer membrane expands and contracts as varying levels of humidity are absorbed, which leads to detachment of the tubes from the bonding resin. The pressure difference between fluid streams can results in cracks, tears, fractures and collapsing the tubes. Maximal differential pressure specified for the humidifiers based on Nafion® can not exceed 2 psi, which is in the range of possible pressure fluctuation.  
         [0009]     As such, there is a constant need in the area of a humidifiers for an improved design and a method of forming the humidifier thereby eliminating problems associated with current designs of prior art humidifiers.  
       SUMMARY OF THE INVENTION  
       [0010]     A humidifier device (the humidifier) of the present invention is used with a fuel cell for balancing fluids therein. The humidifier includes a tubular housing presenting a central axis and terminal ends and a pair of housing ports defined therein. A pair of caps cover each of the terminal ends with each cap being exposed to a cap port. A plurality of polymer tubes presenting terminal openings are adjacent one and another and are disposed in the tubular housing for processing and balancing fluids introduced therein. A covering element formed from an epoxy solution at least partially extends into each of the terminal openings of each polymer tube. The covering element also covers exterior of each said polymer tube at the terminal openings. Each covering element of each polymer tube is homogeneously connected with one another for withstanding pressure of fluids in each polymer tube as the polymer tubes process and balance fluids introduced therein.  
         [0011]     In another aspect of the present invention, a medical device for treating a human is disclosed. The medical device processes fluids, such as for example blood, from the human body with a dialyzing solution thereby treating fluids before fluids are re-introduces to the human body. The medical device includes a semipermeable membrane presenting a central axis and having terminal ends and a pair of housing ports and a pair of caps covering each of the terminal ends with each cap exposed to a cap port.  
         [0012]     A plurality of polymer tubes each presenting terminal openings are adjacent one and another and are disposed in the semipermeable membrane for processing and balancing fluids and the dialyzing solution introduced therein. A covering element at least partially extends into each of the terminal openings of each the polymer tube and covers at least part of each polymer tube at the terminal openings for withstanding pressure of fluids and the dialyzing solution in each polymer tube as the polymer tubes process and balance fluids and the dialysis solution introduced therein. Dializer fittings and connected to the tubular housing are designed to flow the dialyzing solution and blood.  
         [0013]     An apparatus for fabricating the aforementioned humidifier and the medical device is also disclosed in the present invention. The apparatus has at least a frame for engaging the housing of the humidifier and the medical device at the respective terminal ends. The frame presents opposite inlet ports exposed to the terminal openings of the polymer tubes. At least one container for holding a solution, such as an epoxy adhesive, is connected to the frame and is fluidly communicated to each of the opposite inlet ports for transferring the solution to the housing through the terminal ends. An activator is connected to the frame for rotating the same about a rotational axis thereby generating a centrifugal force thereby at least partially introducing the solution internally into each of the terminal openings of the polymer tube for bonding the polymer tubes.  
         [0014]     The polymer tubes of the inventive humidifier present invention are hollow fibers, having water-permeable and micro-pores structure and are fabricated from polysulfone, polycarbonate, polyamide, and the like, adaptable to exchange humidity between two fluid streams, i.e. gas to gas or liquid to gas. The water permeability of the membrane is not higher than 10 ml/hr/mmHg to minimize the leakage of water carrier (DI water, humid gas) into the gas stream subject for the humidification.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:  
         [0016]      FIG. 1  is a cross sectional view of an inventive humidifier;  
         [0017]      FIG. 2  is a cross sectional view of an alternative embodiment of the humidifier shown in  FIG. 1 ;  
         [0018]      FIG. 3  is a cross sectional view of a second alternative embodiment of the humidifier of  FIG. 1 ;  
         [0019]      FIG. 4  is a schematic view of fiber tubes of the humidifier interconnected by a pair of retaining rings, shown in a cross section, to form a bundle or a unitary member;  
         [0020]      FIG. 5A  shows the bundle of  FIG. 4  and a container with epoxy adhesive adjacent the bundle is for briefly introduced into the epoxy adhesive before the humidifier is completely fabricated;  
         [0021]      FIG. 5B  is a cross sectional view of the fiber tubes before introduction into the epoxy adhesive;  
         [0022]      FIG. 6A  shows the bundle of  FIG. 4  wherein terminal ends of the bundle are briefly introduced into the epoxy adhesive before the humidifier is completely fabricated;  
         [0023]      FIG. 6B  is a cross sectional view of the fiber tubes being introduced into the epoxy adhesive;  
         [0024]      FIG. 7A  shows the bundle of  FIG. 4  wherein terminal ends of the bundle are removed from the epoxy adhesive after the same are briefly introduced into the epoxy adhesive;  
         [0025]      FIG. 7B  is a cross sectional view of the fiber tubes after the terminal ends had been introduced into the epoxy adhesive;  
         [0026]      FIGS. 8 through 10  illustrate a cross sectional view of an apparatus for forming the humidifier of the present invention;  
         [0027]      FIG. 11A  is a cross sectional view of the humidifier with the terminal ends of the fiber tubes being completely encapsulated by the epoxy adhesive;  
         [0028]      FIG. 11B  is a cross sectional view of terminal ends of the fiber tubes of  FIG. 11A ;  
         [0029]      FIG. 12A  is a cross sectional view of the humidifier with the terminal ends of the fiber tubes being completely encapsulated by the epoxy adhesive;  
         [0030]      FIG. 12B  is a cross sectional view of terminal ends of the fiber tubes of  FIG. 12A ; and  
         [0031]      FIG. 13  is perspective view of a medical device incorporating the humidifier of the present invention for treating a patient. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0032]     Referring to the Figures, wherein like numerals indicate like or corresponding parts, a humidifier device (the humidifier) of the present invention is generally shown at  10 . The humidifier  10  is used with a fuel cell (not shown) for balancing fluids therein. The humidifier  10  includes a tubular housing, generally indicated at  12 , presenting a central axis A and terminal ends  14  and  16 . A pair of housing ports  18  and  20  are defined therein.  
         [0033]     Alluding to the above, the tubular housing  12  presents an annular wall  24  integrally extending a main portion  26  for aligning a unitary member, generally indicated at  28 . The tubular housing  12  further defined a pair of cap engaging portion  30  and  31 . A pair of fittings  32  and  34  are integral with and extend generally perpendicular to the central axis A from the main portion  26  at each of the terminal ends  36  and  38  of the tubular housing  12 . Each fitting  32  and  34  further extend to the cap engaging portions  30  and  31 . A pair of caps  38  and  40  cover each of the terminal ends  36  and  38 . Each cap  38  and  40  are exposed to respective cap ports  42  and  44 . The caps  38  and  40  are mechanically connected to the respective cap engaging portions  30  and  31 .  
         [0034]     Alluding to the above,  FIGS. 2 and 3  show alternative embodiments of the present invention, generally shown at  200  and  300 , respectively. The humidifiers  200  and  300  present the cap ports  202 ,  204 , and  302  and  304  being mechanically engaged with the respective caps  206 ,  208  and  306  and  308 . The humidifiers  200  and  300  also present the fittings  210 ,  212 , and  310  and  312  being mechanically engaged and/or bonded with the main portion of the respective humidifiers  200  and  300 . The mechanical connection defined between the aforementioned elements illustrated in  FIGS. 2 and 3  are not intended to limit the scope of the present invention.  
         [0035]     The unitary member  28  is defined by a plurality of polymer tubes, generally indicated at  50  being adjacent one and another and disposed in the tubular housing  12  for processing and balancing fluids introduced therein. The polymer tubes  50  of the inventive humidifier  10  acting as a membrane, are hollow fibers, having water-permeable and micro-pores structure and are fabricated from polysulfone, polycarbonate, polyamide, and the like, adaptable to exchange humidity between two fluid streams, i.e. gas to gas or liquid to gas. The water permeability of the membrane is not higher than 10 ml/hr/mmHg to minimize the leakage of water carrier (DI water, humid gas) into the gas stream subject for the humidification.  
         [0036]     A pair of retainer rings  51  and  53  keep the tubes  50  as a unitary member before the tubes  50  are placed inside the housing  12 . The rings  51  and  53  peripherally affix the polymer tubes  50  about the terminal opening thereby expanding the polymer tubes  50  extending beyond the rings  51  and  53  with the polymer tubes  50  abutting the tubular housing  12  thereby eliminating gaps between the tubular housing  12  and the polymer tubes  50  for balancing fluids therethrough. The tubes  50  are bonded by a covering element or sealing compound, generally indicated at  60  in such a fashion to exposed internal capillaries of the tubes  50  to opposite chambers  62  and  64  defined between the sealing compounds  60  and the caps  38  and  40 . The covering element  60  is formed from an epoxy compound and at least partially extends into each of the terminal openings  64  of each polymer tube  50 . The covering element  60  also covers exterior of each polymer tube  50  at the terminal openings, as best illustrated in  FIGS. 6A, 6B ,  7 A, and  7 B. Each covering element  60  of each polymer tube  50  is homogeneously connected with one another for withstanding pressure of fluids in each polymer tube  50  as the polymer tubes  50  process and balance fluids introduced therein.  
         [0037]     As illustrated in  FIG. 13 , the humidifier  10  is incorporated into a medical device, such as, for example, a dialysis machine  70  for treating a human. The dialysis machine  70  processes fluids, such as for example blood, from the human body with a dialyzing solution thereby treating fluids before fluids are re-introduces to the human body. In particular, the dialysis machine  70  mixes and monitors the dialysate, i.e. fluid that helps remove the unwanted waste products from human&#39;s blood and helps get your electrolytes and minerals to their proper levels in the human&#39;s body. The dialysis machine  70  holds a plastic jug device  71  hold the liquids used to mix the dialysate. The dialysis machine  70  mixes the dialysate, which is made up of an acidified solution, bicarbonate and purified water. The acidified solution contains electrolytes and minerals.  
         [0038]     While the human  72  is dialyzing, dialysate and blood flow through a semipermeable membrane  72  or dyalizer catridge presented by the polymer tubes  50  as set forth above, adaptable to withstand pressure of fluids and the dialyzing solution in each polymer tube  50  as the polymer tubes  50  process and balance fluids and the dialysis solution introduced therein. having identical structural characteristics as the humidifier  10  presents. Fresh dialysate from the dialysis machine  70  enters the dialyzer catridge  72  throughout your treatment. Impurities are filtered out of your blood into the dialysate. Dialysate containing unwanted waste products and excess electrolytes leave the dialyzer catridge  72  and are washed down the drain (not shown). A pair of tubes  74  are cooperable with the dyalizer catridge  72  for circulating the dialyzing solution and blood to and from the human body. Dializer fittings  76  and  78  are connected to the dyalizer catridge  72  and are designed to flow the dialyzing solution and blood.  
         [0039]     An apparatus for fabricating the aforementioned humidifier  10  is also disclosed in the present invention and is generally shown at  80  in  FIGS. 8 through 10 . The apparatus  80  has at least one frame, generally indicated at  82 , for engaging the housing  12  of the humidifier  10  at the respective terminal ends. The frame  82  presents opposite inlet ports  84  and  86  exposed to the terminal openings of the polymer tubes  50 . A pair of containers  88  and  90  for holding a solution  92 , such as an epoxy adhesive, are connected to the frame  82  and is fluidly communicated to each of the opposite inlet ports  84  and  86  for transferring the solution  92  to the housing  12  through the terminal ends. The frame  82  may include several parts, such as, for example, the opposite inlet ports  84  and  86 .  
         [0040]     Alternatively, the frame may present a unitary piece (not shown). An activator  100  is connected to the frame  82  or to the housing  12  for rotating the same about a rotational axis B thereby generating a centrifugal force to introduce the solution  92  internally into each of the terminal openings of the polymer tube  50  through pipe conduit members  102  and  104  thereby bonding the polymer tubes  50 .  
         [0041]     The process of forming the humidifier  10  for the medical device  70  is clearly illustrated in  FIGS. 4 through 7 B and begins with affixing the tubes  50  with the aforementioned retainer rings  51  and  53  to form a bundle or the unitary piece thereby forming a dense package of the tubes  50  to prevent the tubes  50  from being loose. Each terminal end of the tubes  50  is then briefly applied into a second epoxy solution  94  hold in a container  96  to fill tips of internal capillaries  98  of the tubes  50  with the epoxy solution  94  whereby the retainer rings  51  and  53  restricts submerging the hollow polymer tubes  50  into the epoxy solution  94 , as best shown in  FIGS. 6A and 6B .  
         [0042]     Alluding to the above, the duration of the exposure of the terminal ends of the tubes  50  into the epoxy solution  94  depends on the viscosity of the epoxy solution  94  and the capillary capability to force the epoxy solution  94  into the internal capillaries  98  and, is generally between 2 and 5 seconds, without limiting the scope of the present invention. The expose of the terminal ends of the tubes  50  to the epoxy solution  94  is necessary for the penetration of the epoxy solution  94  in the tubes  50  without entering the tubes  50  beyond the level the rings  51  and  53 , as shown in  FIG. 6A .  FIGS. 7A and 7B  illustrate the next stage of the method also knows as curing the epoxy solution  94  to clogg the internal capillaries  98 .  
         [0043]      FIGS. 8 through 10  illustrate the next step of the formation of the humidifier  10 . The housing  12  with the tubes  50  disposed therein is placed into the frame  82  of the apparatus  80 . As the frame  82  is rotated about the rotational axis B by the activator  100 , the centrifugal force generated thereby forces the solution  92  internally into each of the terminal openings of the polymer tube  50  through the pipe conduit members  102  and  104  thereby bonding the polymer tubes  50  presents opposite inlet ports  84  and  86  exposed to the terminal openings of the polymer tubes  50 . The volume of the solution  92  placed in the containers  88  and  90  is predetermined based upon configuration and volume of the humidifier  10 . The application of the centrifugal force continues until the curing process of the epoxy is complete. All of the aforementioned components of the apparatus  80  are fabricated from a non-adhesive to the epoxy solution material which allows them to be reusable after the housing  12  and the tubes  50  disposed therein are removed from the apparatus  80 .  
         [0044]     While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.