Patent Document

BACKGROUND OF THE INVENTION  
         [0001]    Flameless combustion heaters are well known. They typically work on the principle that an appropriate hydrocarbon-based fuel, when in contact with a suitable catalyst in the presence of air (or oxygen), will undergo combustion and release heat. This heat can then be distributed and used for a variety of purposes.  
           [0002]    A variety of patents describe the incorporation of such a device on a garment such as a jacket or a belt for providing heat to the body. They typically describe means of pumping the fuel, preheating the fuel-air mixture (often by ignition), and controlling the feeding of the mixture to a catalytic area and distribution of heat resulting from the reaction. These systems tend to add a lot of complexity and cost to the products to which they are incorporated.  
           [0003]    Furthermore, these patents describe heaters which are often based on alkane fuels, preferably propane or butane. These fuels are gases, and as such do not lend themselves to being carried easily in portable applications including garments. When using liquid alcohols as fuels, the fuel-air mixture is preheated and ignited before catalytic combustion occurs. Fuels in this category include methanol, naphtha, and ethanol. It is advantageous to react them in the gas phase with air in the presence of a catalyst. Since alcohols are liquids under operating conditions, one way to achieve this goal is shown in U.S. Pat. No. 6,062,210, which describes means of feeding methanol fuel through pores placed in a feeding tube in close proximity to the catalyst. However, this method is not selective, in that the pores will also allow the passage of other substances, which may happen to be present with the methanol fuel. This method can also allow the passage of liquid fuel to flood the catalyst.  
           [0004]    These and other shortcomings are overcome in the invention described herein.  
         SUMMARY OF THE INVENTION  
         [0005]    The invention described herein refers to a portable catalytic heater in which fuel vapor and air (or other means of oxygen supply), are supplied to a catalyst. The catalyst promotes the flameless combustion of the fuel releasing heat. The liquid fuel is supplied through the use of a selectively permeable membrane, such that only the fuel vapors diffuse through the membrane and are fed to the catalyst. The catalyst is placed on a support that allows for the diffusion and mixing of reactants such as a porous fiber felt coated with catalysts. Alternatively, the selectively permeable membrane may support the catalyst. The supply of fuel to the selectively permeable membrane and the exact identity of the membrane serve as a way to regulate the degree of heating provided by the catalytic heater. The selective molecular filtration of the fuel through the membrane keeps the catalytic heater from being contaminated from impurities in the fuel, such as salts. The selective permeability of the membrane to fuels (e.g. methanol), over the product (i.e. water), keeps the liquid fuel reservoir from being contaminated with the product and maintains the fuel concentration and a steady rate of fuel delivery. By containing the fuel behind the selective membrane and using diffusion to deliver the fuel, the rate is dependent upon the concentration of liquid in contact with the fuel membrane rather than the fuel vapor pressure. This makes the delivery of fuel and air to the catalyst less sensitive to temperature.  
           [0006]    Another feature of the invention is an additional coating which protects the combustion catalyst from contamination and can enhance the catalytic effects. If the coating has the ability to conduct ions (i.e. protons), it may be used to enhance or lower the catalytic combustion rate through electrochemical processes on the catalysts (removal/addition of hydrogen/proton intermediates to catalytic surface). This may be achieved by inserting two electrodes on either side of the coating and applying a voltage across said coating. The coating also has certain permeability to the fuel and the products of the combustion reaction. It serves the purpose of adhering the catalyst powders to the substrate on which they are supported and can limit the catalytic combustion rate serving as yet another regulating mechanism in our invention. The coating can also have an affinity for the fuel, oxidizer, and products to increase the effectiveness of the fuel. The catalytic heater can be incorporated into a system for various applications. One of the unique features of using a liquid fuel with the selectively permeable membrane in proximity to the catalytic heater is when the fuel reaches its boiling point it removes heat from the catalytic reaction site and subsequently limits the maximum temperature. The vaporized fuel can be condensed in a heat exchanger and deliver the thermal output of the heater efficiently. Different mixtures of fuels or a maximum pressure of the fuel reservoir can be chosen to set the boiling point of the fuel and hence the maximum temperature of the heater. This fuel boiling mechanism along with the back diffusion of carbon dioxide and nitrogen can also be used to keep the fuel homogeneous and self purging. By keeping the fuel homogeneous and not in direct contact with catalysts the heater can easily be purged of fuel contamination by draining the fuel.  
           [0007]    Another feature of this invention is the membrane through which the fuel is fed is not prone to failure. Unlike U.S. Pat. No. 6,138,665 where the fuel flows through porous tubes, our invention describes the use of a membrane that works by diffusion. One practical way in which this feature is important is the ability to run a catalytic heater with pure methanol fuel, and no water added.  
           [0008]    Yet another feature of this invention, due to the fueling mechanism of using the selectively permeable membrane, is that the catalytic heater is insensitive to orientation. A steady delivery of liquid fuel or gas fuel is needed to maintain contact with the selectively permeable membrane. Bubbles and gas pockets in the fuel will not significantly effect the diffusion of fuel through the selectively permeable membrane as long as the surface of the membrane is wetted by fuel. A wet coating or wicking material could be used to spread liquid fuel uniformly over the surface of the selectively permeable membranes. Increasing the hydraulic pressure will not significantly increase the concentration of a liquid fuel against a selectively permeable membrane. Thus the diffusion rate of fuel will not be changed if the system is inverted causing a low or high hydraulic pressure on the selectively permeable membrane. This invention also does not depend on the use of pumps which add complexity and cost of the heater, to create a fuel oxidizer mixture.  
           [0009]    Additional features of this invention are the pressurization of the fuel behind the selectively permeable membrane and its flexibility which enable unique passive controls of the diffusion of fuel and air. Temperature selective diffusion through the membrane can also be used to limit or accelerate the fuel delivery. Also, the flexibility of the polymers and rubber materials used in this)invention permits flexibility in packaging into a wide variety of applications such as apparel, blankets, machinery, dwellings, shipping containers, storage containers, insect attractants, humidifiers, and perfume generators.  
         PRIOR ART  
         [0010]    Weiss U.S. Pat. No. 2,764,969 “Heating Device”. This patent describes a catalytic heating system comprising a plurality of tubes which direct the heat generated from the reaction to different parts of the user&#39;s body. It does not describe means of using a selectively permeable membrane.  
           [0011]    Bals et al. U.S. Pat. No. 5,331,845 “Probe and Method for Detecting Alcohol”. This patent describes a probe for measuring the concentration of an alcohol. The probe has a membrane that is permeable for vapors of the alcohol but substantially impermeable for the liquid. It does not teach the application of the system to a catalytic combustion heater.  
           [0012]    Welles U.S. Pat. No. 5,901,698 “Mechanically Compliant and Portable Catalytic Heating Device”. This patent describes a portable catalytic heater where reactants are uniformly released through porous tubes woven with catalyst-impregnated glass filaments into a sheet-shaped, fabric-like structure enclosed in a Mylar envelope. It does not describe the use of membrane materials that are selectively permeable.  
           [0013]    Yates and Yates U.S. Pat. No. 5,928,275 “Body Warmer Belt”. This patent describes a heater system in the shape of a belt for warming the user&#39;s kidney region. It uses a heating pouch made up of activated charcoal, iron powder, and saltwater and wood fibers. It does not cover means of regulating the amount of heat using permeable membranes, and it does not teach how to turn the device off.  
           [0014]    Welles U.S. Pat. No.  6 , 062 , 210  “Portable Heat Generating Device”. This patent describes a portable catalytic heater where reactants are directed through channels contained within a thin, flexible elastomeric sheet of material. The catalytic heat elements are disposed within said channels. It does not describe the use of membrane materials that are selectively permeable.  
           [0015]    Hanada et al. U.S. Pat. No. 6,138,664 “Warming Jacket”. This patent describes a catalytic heater incorporated onto a jacket to provide warmth for a user&#39;s body. It does not describe the use of selectively permeable membrane materials.  
           [0016]    Welles U.S. Pat. No. 6,138,665 “Portable Heat Generating Device”. This patent describes a portable catalytic heater where reactants are uniformly released through porous tubes woven with catalyst-impregnated glass filaments into a sheet- shaped, fabric-like structure enclosed in a Mylar envelope. It does not describe the use of selectively permeable membrane materials.  
           [0017]    Hanada et al. U.S. Pat. No. 6,206,909 B1 “Portable Warmer Suitable for a Body”. This patent describes a portable catalytic heater incorporated onto a belt that is used to warm the user&#39;s body. It does not describe the use of selectively permeable membranes.  
           [0018]    Trade Names/Materials:  
           [0019]    Silicone rubber membranes  
           [0020]    Specialty Silicone Products  
           [0021]    Corporate Technology Park  
           [0022]    3 McCrea hill Road  
           [0023]    Ballston Spa, N.Y. 12020  
           [0024]    DAIS polymer electrolyte (DAC589- 9.1% solid solution)  
           [0025]    DAIS-Analytic Corp.  
           [0026]    11552 Prosperous Dr.  
           [0027]    Odessa, Fla. 33556  
           [0028]    Zylon felt  
           [0029]    Toyobo  
           [0030]    2-8, Dojima Hama 2-Chome, Kita-ku  
           [0031]    Osaka, 530-8230, Japan  
           [0032]    Pt/Ru black catalyst on Carbon  
           [0033]    Alfa-Aesar  
           [0034]    30 Bond Street  
           [0035]    Ward Hill, Mass. 01835-8099  
           [0036]    Cool Max  
           [0037]    DuPont Corporation  
           [0038]    1007 Market Street  
           [0039]    Wilmington, Del. 19898  
           [0040]    Engelhard  
           [0041]    Chemical Catalysts Group  
           [0042]    554 Engelhard Dr.  
           [0043]    Seneca, S.C. 29678  
           [0044]    Nafion: Perfluorosulfonic Acid, DuPont Corporation.  
           [0045]    Alcohol solutions available through:  
           [0046]    Solutions Technology, Inc.,  
           [0047]    P.O. Box 171  
           [0048]    Mendenhall, Pa. 19357.  
           [0049]    Aldrich Chemical Company  
           [0050]    P.O.Box 2060  
           [0051]    Milwaukee Wis. 53201 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0052]    [0052]FIG. 1. Cross-sectional view of the fuel tank with membrane and felt supported catalyst.  
         [0053]    [0053]FIG. 2. Cross-sectional view of the fuel tank with membrane and catalyst embalmed in matrix and an outer diffusion membrane.  
         [0054]    [0054]FIG. 3. Cross-sectional view of a selectively permeable tube fuel delivery and a surrounding tubular catalyst supporting nonwoven fabric.  
         [0055]    [0055]FIG. 4. Cross-sectional view of a tube fuel and air delivery to an enclosed tubular catalyst supporting felt or nonwoven fabric.  
         [0056]    [0056]FIG. 5. Cross-sectional view of the fuel tank with membrane heater and thermopile and heat exchanger surfaces.  
         [0057]    [0057]FIG. 6. Cross-sectional view of the catalytic heater system with thermopile, valves, fans, regulating electronic thermostat and gas flow channels.  
         [0058]    [0058]FIG. 7. Schematic representation of the electrical control system for the catalytic heater system.  
         [0059]    [0059]FIG. 8. Cross-sectional view of the catalytic heater electrochemical cell and diffusion fuel feed.  
         [0060]    [0060]FIG. 9. Cross-sectional view of the catalytic heater with heating regulation with membrane valving.  
         [0061]    [0061]FIG. 10. Cross-sectional view of the catalytic heater configured with a selectively permeable sealed fuel ampoule.  
         [0062]    [0062]FIG. 11. Cross-sectional view of a selectively permeable fuel ampoule with a fuel impermeable container. FIG. 12. Cross-sectional view of the catalytic heater configured with a pump ampoule. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0063]    In FIG. 1 a fuel tank  10  is shown filled with methanol fuel  11 . The aluminum tank  10  has a silicone rubber membrane  8  (Specialty Silicone Products, Corporate Technology Park, 3 McCrea Hill Road, Ballston Spa, N.Y. 12020) sealed to the tank wall with 1000% silicone rubber sealant (GE Silicones, Waterford, N.Y. 12188). The methanol fuel  11  preferentially diffuses through the silicone rubber membrane  8  to mix with air  12 . Several alternative fuels  11  are formaldehyde, formic acid, 1,3,5-trioxane, di-methyl-ether, acetone and pentane, among others. A felt of polybenzoxazol (PBO), a high temperature high performance fiber  5  (Zylon felt, Toyobo, 2-8, Dojima Hama 2-Chome, Kita-Ku, Osaka, 530-8230, Japan) is coated with Platinum and Ruthenium (Pt/Ru) black catalyst  6  (Alfa-Aesar Alfa-Aesar 30 Bond Street Ward Hill, Mass. 01835-8099). Alternative felts are made of fibers of polybenzimidazole (PBI), polyimides, alumina, fiber glass, zirconia, quartz, p-aramids felts. This catalyst layer is then over-coated with a thin coating  7  such as a solid polymer electrolyte DAIS (DAIS-Analytic Corp., 11552 Prosperous Dr., Odessa, Fla. 33556), Nafion (Solution Technology, Inc., Mendenhall, Pa. 19357) or silicone rubber. The example coatings and materials can be deposited by airbrush spraying a suspension of the catalyst powders. Over-coatings can be deposited by airbrush spraying of a solid polymer electrolyte dissolved in a solvent and dried under air or inert gas. In operation air and fuel diffuse into the coated felt  5  and catalytic combustion occurs on the surface of the catalyst Pt/Ru black. The felt  5  provides a substrate resistant to high temperatures and with a low heat capacity. The catalyst  6  breaks down the methanol and oxidizes it with oxygen from the air. Specific catalysts used are those that can oxidize hydrocarbons and carbon monoxide, which is the last step in the catalytic combustion process. The overcoat  7  on the catalyst serves the purposes of protecting and adhering the catalyst powders and coatings to the felt  5 . It also has a high solubility and affinity for the fuel and water so it increases the concentration of the fuel on the catalyst  6 . The overcoat  7  also has a high but limited permeability to fuel and oxygen, which limits the rates of catalytic combustion on the catalyst surface and keeps the catalyst from going into high temperature or flame combustion. High temperature combustion can damage the components. The selective permeability of the coating  7  on the catalyst may protect the catalyst by keeping large organic molecules and salts from reaching the surface of the catalyst  6  and limit the presence of products such as water on the catalyst surface, protecting the catalyst surface from environmental contamination. Coatings  7  on the catalysts such as Nafion or DIAS that are electrolytic may enhance the catalytic oxidation. The coating  7  on the surface of the catalyst  6  can also have a permeability that changes with temperature to act as a fuel and oxidizer moderator. As an example, materials such as the solid polymer electrolytes, (e.g. Nafion and DAIS) have lower methanol permeability when they dehydrate with increasing temperature. The catalyzed felt  3  catalytically burns the methanol and air mixture as the oxygen  12  diffuses from the surrounding air and the methanol diffuses through the selectively permeable membrane  8 . The selective permeability of the membrane  8  prevents water from diluting the fuel and reducing the fuel delivery rate. It also filters many contaminates that could be in the fuel from reaching the catalysts  6 . The selective diffusion through membranes is dominated by the concentration gradient across them and its permeability at particular temperatures. The fuel delivery is therefore independent of the vapor pressure of the fuel when the selective membrane is immersed in fuel. The heat produced by the catalyst felt  3  is conducted into the aluminum fuel tank  10  and into the aluminum cover wall  4 . The heat can be conducted and distributed to the application through these surfaces. Heat can also be moved by vaporizing and condensing the fuel such as methanol from the fuel tank  10  to the vent line  2 . Fuel  11  such as methanol will condense in the vent line  2  and be returned to the fuel tank  10  by gravity. The carbon dioxide produced in the catalytic burner exhausts through the inlet diffusion route  12  or through the silicone membrane  8 . When the heater is running, the temperature can get above the boiling point of the fuel and it will boil. The fuel vapor goes up the vent line  2  and condenses on the walls of the vent line  2 . This boiling of the fuel acts to limit the temperature of the heater  3  by heat removal with the vaporized fuel  9 . The dissolved carbon dioxide in the fuel is also removed from the fuel by boiling  9  of the fuel  11  and vented  1  out of the vent line  2 .  
         [0064]    In FIG. 2, the heater is composed of catalyst particles  13  incorporated into a material such as silicone rubber, Nafion, or DAIS or other selectively permeable embalming material  21 . The catalyst particles  13  can consist of a thin film of platinum and ruthenium (Pt/Ru) catalyst or atomic catalyst clusters of platinum (Pt)  23  dispersed over the surface of a high surface area zeolite, alumina, or activated carbon particles  22 . In this design the fuel diffuses through the selectively permeable membrane  18 , through the embalming material  21  to the catalyst particles  13 . Oxygen diffuses from the air  15  through an outer membrane made of silicone rubber or a porous filter to dust and liquid water such as micro-porous polytetrafluro ethylene  14  (DuPont Corporation, 1007 Market Street, Wilmington, Del. 19898), or Nafion: Perfluorosulfonic Acid, (DuPont Corporation). Alcohol solutions of Nafion are available through: Solutions Technology, Inc., P.O. Box 171, Mendenhall, Pa. 19357., Wilmington, Del. Over this outer membrane  14  perfluoropolyalkylene oxides such as polyperfluropropylene oxide or polyperfluoropropylene oxide co-perfluroformaldehyde, (Aldrich Chemical Company. P.O.Box 2060 Milwaukee Wis. 53201) can be coated to give it more selective permeability to oxygen and selectively retain fuel. The oxygen membrane can also be a material or mechanical mechanism that increases or decreases its rate of oxygen diffusion depending on temperature, thus limiting the catalytic combustion. The outer membrane  14  can also be a material or mechanical mechanism that changes its thermal insulation properties so that at low temperatures it is a good insulator and at higher temperatures it is a heat transfer material. A micro-porous material such as expanded polytetrafluoroethylene (PTFE), polybenzimidazole (PBI) felt or perforated polyimide sheet could also be effective in creating a diffusion filter and thermal insulation region  14  between the catalyst  13  and the outside air  15 . The oxygen diffuses to the surface of the catalyst particles  13  to react with the fuel on the catalyst  23 . The heat generated by the catalytic combustion is conducted into the fuel tank and to the outer surface of the air filter  14 . The heat can be delivered to the application through the case  20  (made of aluminum, PVC or stainless steel), the condensation tube  17  or the surface of the air membrane  14 . The methanol fuel  21  will boil when it reaches its boiling point and remove heat from the surface of the fuel membrane  18 . Water and carbon dioxide produced by combustion at the catalyst  13  will diffuse through the embalming material and the fuel membrane  18  and out through the air membrane  14 . The selective permeability of fuel over water of the fuel membrane  18  compared to the air membrane  14  will lead to the water product being blocked from diffusing into the fuel  21  and the dominant water exhaust route being out through the outer membrane  14 . The silicone rubber, Nafion and DAIS materials will all have a high permeability to carbon dioxide. A large fraction of the product carbon dioxide will diffuse through the fuel membrane  18  and into the fuel  21 . Along with the heat removal by boiling the fuel  19  and condensing  78  on the outlet tubes  17 , carbon dioxide is vented  16  from the fuel with the boiling methanol  19 . The condensed methanol  78  in the outlet tube  17  is returned to the fuel tank via gravitational pull. This device just described with the addition of a fueling scheme could be used as a pocket heater in apparel.  
         [0065]    In FIG. 3 the methanol fuel  26  is contained in a silicone rubber tube  28  lined with a polyester fiber wetting tube liner  33  made of Cool MaxÔ (Du Pont). The silicone rubber tubing  28  is surrounded by cylindrical porous felt of PBO or nonwoven fabric  31  that is coated with catalyst  30 . The catalyst-coated felt tube  31  is then surrounded by an uncoated PBO nonwoven fabric  29 . In operation the methanol fuel  26  diffuses through the wall of the silicone rubber tube  28  and out to the catalyst particles  30 . Oxygen diffuses from the atmosphere  27  through the outer PBO nonwoven fabric  29 . Heat from the catalytic combustion is conducted through the outer PBO nonwoven fabric to the surroundings. This long tube design can be a wrap around or serpentine on the surface of the application to be heated. The fuel  26  will boil  25  when the heater temperature reaches its boiling point. The vaporized fuel  25  goes up the tube and condenses  32  on the vent line  2 . Condensed fuel  32  is returned to fuel in the tube by wicking into the tube liner  33 .  
         [0066]    [0066]FIG. 4 shows a cross-sectional view of cylindrical tubes, where the methanol fuel  49  and the air  35  are contained in parallel tubes  36  and  38 . The methanol fuel  49  is contained in one tube  36  and the air  35  is pumped through the adjacent tube  38  or tubes. The air tube  38  is made of silicone rubber or other polymers and is perforated with small pores  47  to let air  35  flow through. The fuel tube  36  is made of silicone rubber and fuel selectively diffuses out through the silicone rubber to the surrounding PBO felt or nonwoven fabric, which has been coated with catalyst particles  39 . The catalyst particles  39  are supported on a porous material of zeolite, alumina or activated carbon particles  43 . These are then coated with sputter deposited films of Pt/Ru or Pt. The activated carbon  43  supported catalysts  42  can also be obtained from Engelhard (Chemical Catalysts Group, 554 Engelhard Dr., Seneca, S.C. 29678). The catalyst particles  39  are air brushed onto the PBO felt tube  45 . The PBO nonwoven fabric  45  with catalyst particles  39  are then wetted and coated with air brushed solid polymer electrolyte DAIS  41  in a solvent, diluted with 1-propanol (Product number). The solid polymer electrolyte  41  adheres the catalyst particles  39  to the PBO felt. Surrounding the catalyst coated PBO felt tube  45  is a second PBO felt tube  44 . This second PBO felt tube  44  acts as a thermal insulator from the outer skin tube  40 . Vent holes  46  placed at the end of the skin tube  40  are made of stainless steel or silicone rubber. In operation the methanol fuel  49  flows through the fuel tube  51  from a reservoir  37 . The methanol fuel  49  diffuses through the silicone rubber walls of the fuel tube  36  to the catalyst particles  39 . The methanol diffuses through the coating  41  on the particles to the catalytic surface  42 . Air is pumped through the air tube  38  and through the vent holes in the air tube  38  and bypass exit  48 . Air diffuses through the coatings  41  to the Pt/Ru catalyst  42 . The methanol and oxygen combust on the Pt/Ru surfaces  42  and produce carbon dioxide and water. The carbon dioxide diffuses out through the catalyst coating  41  out to be carried away by the air flow and exit  46  or diffusing into the fuel  49  through the fuel tube wall  36 . Carbon dioxide dissolved in the fuel  49  will be carried out with the flow of the fuel tube  36  to the reservoir tank  37 , where it can vent out a vent hole  34  in the reservoir tank  37 . Product water diffuses through the catalyst coating  41  from the catalytic surface  42  and is carried out the air vent  42  with the airflow. Due to the selective permeability of the fuel tube  26  very little product water can back diffuse into the fuel  49 . This keeps the fuel pure and its diffusion rate constant through the fuel tube wall  36 . The heat generated from the catalytic burn conducts from the catalyst surfaces  42 , through the coating  41 , through the felts  45  and  44  to the fuel and air tube and the outer skin surface  40 . The heat produced can be delivered to the application either through conduction of the outer skin  40  or into the flowing fuel  49  and air  35  in the fuel  36  and air  38  tubes. The methanol fuel  49  can also boil  50  and remove heat. Alternatively heat can also be delivered by the flow of air out the bypass flow  48 , the flow of exhaust gases through the vent  46 , and by the condensing of fuel on the walls of the fuel reservoir  37 .  
         [0067]    In FIG. 5 a system of percolation circulation with heat exchangers and a thermopile is shown. In this scheme the fuel reservoir is filled with methanol fuel  76 . The fuel is fed by gravity  75  through the supply tube  70  to the bottom of the fuel membrane  58 . The fuel  76  diffuses through the fuel membrane  58  to the PBO felt  77  coated with sputter deposited Pt/Ru catalyst  56 , and DAIS solid polymer electrolyte  57 . Oxygen diffuses from the outside air  73  through the channels of the heat exchange aluminum block  72 . The resulting combustion products of carbon dioxide and water diffuse out through the channels of the aluminum block  72 . Some carbon dioxide diffuses though the fuel filter  58  into the fuel. The heat produced by the catalytic combustion at the Pt/Ru  56  coated PBO felt  77  goes into the channeled aluminum block  72 , through the fuel membrane  58  into the fuel  76 . When the temperature of the fuel hits its boiling point the fuel boils and creates bubbles  68  in the fuel. The bubbles rise up to an aluminum heat exchanger  60 . At the heat exchanger  60  the vaporized fuel  68  condenses  61  and delivers heat. The carbon dioxide bubbles  59  that are left after the fuel condenses continue with the flow  63  of fuel to the reservoir tank  74 . The carbon dioxide  59  that does not stay in solution in the fuel vents through a vent valve  64  on the vent line tube  62 . The methanol that is carried with the venting gas is catalytically burned by a catalyst coated felt  71  covering the outlet tube  62  and vent valve  64 . The heat that travels into the channeled aluminum block  72  goes through a ceramic insulator  53  into the thermopile  54 . The thermopile consists of the Peltier junctions formed by blocks of bismuth telluride alloy  54 , metal conductors  52  and the output leads  55  and  69 . The heat flows through the thermopile out through a second ceramic insulator  66  and to a channeled aluminum heat exchanger  67 . When the catalytic heater is running the thermopile will generate electrical power in addition to being able to supply heat.  
         [0068]    In FIG. 6 the system shown uses the catalytic heater with heat exchangers, thermopile, pumped airflow, fuel control valves, and electronic controls. This figure is an illustration of an application of the catalytic heater to be an electronic thermostat-controlled flowed air heater. In this scheme the fuel reservoir is filled with methanol fuel  81 . The fuel is fed by gravity through a fuel tube  80  to the bottom of the fuel membrane  108  on the fuel tube  80 . A shut off valve  100  is placed near the inlet to the fuel membrane on the feed line. A second valve  79  is placed near the outlet to the fuel tank. Both valves could be electronically controlled but the most likely mode of operation is to electrically shut just the upper valve  79  and stop the airflow though the system. The lower shut off valve  100  could be a manual valve. The heater  115 ,  106 ,  107  would continue to heat but drive the fuel away from the fuel membrane  108  with vaporized fuel. This would maintain pressure/temperature equilibrium with the heater so that the heater would remain idled with very little fuel. When the temperature drops below the boiling point of the fuel, it would condense and refill the area near the fuel membrane and subsequently start the heater repeating the cycle. Closing the shutoff valve  100  would stop the flow of fuel to the heater which would continue to run until the vaporized fuel  99  and liquid fuel  110  is returned to the fuel reservoir  103  or combusted in the catalytic burner  115 ,  106 ,  107 . This would shut off the heater system. Pressure relief valves  104  and  114  could be placed on the fuel reservoir vent tube  82  and on either side of the upper valve  79  to release excessive pressure and carbon dioxide gas. Relief valves  104 ,  114  and vents can be incorporated as spring-loaded seals in cover caps. The open pressure for these relief valves sets the boiling point of the methanol fuel or other fuels. Different fuels can be used to set the maximum external temperature of the catalytic burner. By using heat pipes in parallel with a boiling fluid and a fixed quantity of non-boiling gas the upper external temperature of the catalytic burner can also be set. To provide warmed airflow to the catalytic heater a duct  92  will be placed parallel to the outlet heat exchanger  85 . Air  84  is drawn through the heat exchanger  85  by a fan  89  to be preheated before it arrives at the catalytic burner. The air goes through the catalytic burner aluminum channels  116  and then the exhaust air  101  passes back past the fuel tank  103 . The exhaust air  101  cools as it passes the fuel tank  103  and water a combustion product can be condensed out of the exhaust air  101  and collected in the exhaust tube  92 . On the other side of a barrier  112  cold air  90  is drawn in through ducting  95  to cool the aluminum heat exchanger  87  on the thermopile  113 . The air  83  is then pumped by a fan  97  to pass out through a heat exchanger  96  and out to the application. In operation the fuel  81  diffuses through the fuel membrane  108  to the coated PBO felt  115  coated with sputter deposited Pt/Ru catalyst  106  and DAIS solid polymer electrolyte  107 . Oxygen is drawn from the outside air with a fan  89  through the channels of the heat exchange aluminum block  116 . The air is preheated as it flows past the fuel reservoir and the heat exchangers with the outgoing air. The resulting combustion products of carbon dioxide and water are carried with the flow out through the channels of the aluminum block  116 . Some of the product water can be condensed as the exhaust air  101  is cooled and can be collected. Some of the product carbon dioxide diffuses though the fuel filter  108  into the fuel. The heat produced by the catalytic combustion at the Pt/Ru  106  coated PBO felt  115  goes into the channeled aluminum block  116  and through the fuel membrane  108  into the fuel  81 . When the temperature of the fuel hits its boiling point, the fuel boils and creates bubbles in the fuel  99 . The bubbles in the fuel rise up to an aluminum heat exchanger  85 . At the heat exchanger the vaporized fuel condenses. and delivers heat. The carbon dioxide bubbles  109  that are left after the fuel condenses  111  continue with the flow of fuel to the reservoir tank  103 . The carbon dioxide  109  that does not stay in solution in the fuel vents through a vent valve  104  on the vent line tube  82 . The heat that travels into the channeled aluminum block  116  goes through a ceramic insulator  93  into the thermopile  113 . The thermopile consists of Peltier junctions formed by blocks of bismuth telluride alloy  105 , metal conductors  117  and the output leads  165  and  94 . The heat flows through the thermopile out through a second ceramic insulator  86  and to a channeled aluminum heat exchanger  87 . When the catalytic heater is running the thermopile will generate electrical power in addition to being able to supply heat. The electrical power from the thermopile can be used to run the fan motor  98 , charge a battery and run the temperature control electronics for the thermostat and the electrically actuated valves. When the system is running the valves  100  and  110  will open. Fuel will flow to the fuel membrane from the reservoir and the heater will turn on and rise in temperature. In very cold conditions a resistance heater  88  using energy from the batteries  122  shown in FIG. 7 the fuel membrane  108  and catalytic felt  115 ,  106 ,  107  would be used to vaporize the fuel  81  and start the catalytic combustion. When the temperature hits the boiling point of the fuel  81  the heat transfer will be increased by vaporization and condensation. The thermopile  113  will produce sufficient power to run the fan  98  motor and recharge the batteries  122  as shown in FIG. 7. When sufficient heat is delivered to the application, the thermostat  118  shown in FIG. 7 will close the second valve  79  and the fans  89 ,  97  will be switched off. The vaporized fuel  99  will force the liquid fuel  81  back away from the fuel membrane  108  back to the fuel reservoir  103 . The catalytic heater  115 ,  106 ,  107  will go into a lower rate of combustion with only oxygen diffusing to the heater through the inlet and outlet ducts and the fuel delivery rate reduced. A simplified version of a temperature regulated heater system could achieve temperature control by temperature regulating the second valve  79  alone. In this simplified thermostatic system gas flow circulation is by convection air flow and boiling and condensation of the fuel. The electrical system could be eliminated by using valves that are differential metal or fluid expansion valves (manufacturer). The heater devices as described can be used in a variety of applications with adaptations of components in apparel, blankets, machinery, dwellings, shipping containers, storage containers, odor generators, humidifiers, and insect attractants.  
         [0069]    In FIG. 7 a schematic drawing of the electrical control system for the heater in FIG. 6 is shown. In this schematic the electrical output from the thermopiles  119  is fed through a diode  124  to charge a battery  122 . The output of the battery  122  and the thermopile  119  is switched through a thermostat  118 . The thermostat  118  is schematically represented for simplicity as a bimetallic switch. There are a large number of alternative thermostat mechanisms such as a thermistor and integrated electronic controls. When the temperature on the thermostat  118  reaches the desired set point the switch is closed and current runs the fan  121  for the catalytic heaters and the delivered airflow. An electromechanical valve  120  is opened by the current flow and lets fuel flow to the diffusion membrane  108  to feed the catalytic heater  115 ,  106 ,  107  fuel shown in FIG. 6. In this schematic FIG. 7 a second bimetallic thermostat switch  171  is shown, that can be set to close when the temperature is lower than the needed temperature to start catalytic combustion in the heater  115 ,  106 ,  107 . This will divert current to a resistant coil heater  123  or catalyst electrolytic cell shown in FIG. 8. An alternative to the resistance heater is an ignition coil that repetitively sparks to ignite the fuel-air mixture over the catalyst region. This will initiate the catalytic combustion so that when the catalytic heater reaches a self sustaining temperature the bimetallic thermostat switch  171  will open, stopping the electrically assisted catalytic combustion. When the heater has delivered sufficient heat to bring the temperature to the desired set point of the load, the thermostat  171  opens the circuit turning off the fan  121 . The electrically actuated valve is closed and the fuel supply to the diffusion membrane  108  is stopped. The catalytic heater  115 ,  106 ,  107  will continue to run until it has used or cleared the fuel away from the diffusion membrane  108 . The thermopile  119  will continue to charge the battery  72  until the temperature of the catalytic heater drops and the voltage of the thermopile falls bellow that of the battery. The diode  124  will then prevent a discharge current flow back through the thermopile  119  from the battery  122 .  
         [0070]    In FIG. 8 an electrochemical combustion cell is shown. This device consists of two electrodes  129 ,  126  formed by gold sputter coating PBO felt  135 ,  133 . Gas permeability into the electrodes is provided by open pores  140  in the felts  135 ,  133 . Pt/Ru black or sputter coated Pt/Ru  136 ,  134  is spray coated onto the PBO felt and a solid polymer electrolyte DAIS  137 ,  125  in a 1-propanol solution is spray coated over the Pt/Ru black  136 ,  134 . A sheet of DAIS electrolyte  138  is inserted between the two electrodes  126 ,  129 . A methanol fuel supply is provided to the cell by methanol diffusion through a selectively permeable membrane  128  and a reservoir  130  of fuel  139  in close proximity to the cell. In operation, the methanol fuel  132  and air  131  diffuse to the surface of the catalyst  136 . A voltage potential is imposed across the cell through the electrodes  126 ,  129 . Methanol and oxygen oxidize on the surface of the catalyst  136 . Different applied potentials across the membrane can be used to accelerate or impede the catalytic combustion. In this way, one can obtain a fine control over the catalytic performance. On the surface of the catalyst  136 ,  134 , protons are removed from methanol and moved through the electrolyte coating  137  through the separator electrolyte  138  and out to the second coating electrolyte  125 . The proton movement through the electrolyte can also ionically drag methanol fuel through the separator electrolyte  138  increasing the delivery of fuel to be oxidized. In some situations with specific concentrations of fuel on the source side  132  and the air source side  131 , the cell will run, as a fuel cell without external power needed to run current through the cell. The products of the cell are carbon dioxide and water, which diffuse out of the cell. This electrochemical combustion cell can include the following five features: First, the electrical potential on the electrodes can clean the catalysts. Second, the proton removal from the catalytic surface accelerates the catalytic performance. Third, the electrical current can heat the catalyst regions through ohmic resistance. Fourth, the electrochemical potentials on the catalysts and fuels can induce accelerated catalytic performance that is very slow at room temperatures. Fifth, the different catalytic breakdown routes can occur on the catalysts at different potentials. Thus, a wider range of fuels and fuel conditions could be handled with this mechanism compared to non-polarized catalysis.  
         [0071]    In FIG. 9 a mechanism of using the diffusion membrane to form a pressure sensitive valve to regulate the fuel and or oxygen delivery to catalytic combustion is shown. In this arrangement of the invention the selective diffusion membrane  158  can be thickened in spots  144  or have disks of an impermeable film  144  such as aluminum glued with silicone sealant or sputter coated onto the membrane  158  that correspond to apertures  153  in a plate  152 . A catalytic felt  143  is placed over the aperture plate  152 . Two air diffusion plates  148 ,  157  made of aluminum with offset apertures  145 ,  149  are placed over the catalytic felt  143 . The aperture plates  148 ,  157  are glued  164 ,  150  with silicone sealant along the perimeter through the catalytic felt  143  to the aperture plate  162 . The diffusion plates  148 ,  157  are spaced apart from each other by the thickness of the glue seal  164 ,  150 . Both the fuel diffusion rate and oxygen diffusion rate can be controlled by either flexible sealing plates or non-aligned compressible aperture plates and are show as an example of each in FIG. 9. The diffusion of oxygen between the catalytic felt  143  and the first flexible outer plate  148 , on the oxygen pores  145  inlet side can be regulated by these same mechanisms as used with the fuel delivery. With the oxygen plates a second outer plate  157  and non-aligned apertures  149  or sealing apertures are used. The oxygen diffusion is reduced when the fuel membrane  158  is pressed up against the fuel aperture plate  152 ; the catalytic felt  143  and the outer plates  148  and  157 . On the vent gas  141  outlet  142  a pressure valve or flow-limiting valve  154  is placed. A fuel tank is formed from aluminum  160 . A silicone rubber fuel membrane  148  is glued with silicone sealant to the aluminum tank  160 . Contained within the fuel manifold formed by the aluminum tank  160  and the silicone rubber membrane  148  is methanol fuel  151 . In operation the fuel  151  is delivered by diffusion through the membrane  158 . Oxygen diffuses from the atmosphere to the catalytic felt  143  through the aperture plates  157  and  148  to the catalytic felt  143  combusting the fuel and oxygen. The heat from the combustion heats the fuel tank  160 , boils the fuel  159  and heats the outer plate  157 . Due to diffusion of gases such as carbon dioxide and nitrogen into the fuel  151 , the fuel tank  160  will pressurize. From this pressurization it bows the fuel membrane  158  and it subsequently presses it against the aperture plates  152 ,  148 ,  157  and the catalytic felt  143 , sealing off the diffusion of fuel and air to the catalytic felt  143 . This stops or reduces the production of heat from the catalyst combustor depending on the amount of diffusion reduction achieved by the fuel membrane  158  and the aperture plates  152 ,  148 ,  157 . The combination of heat production and temperature of the heater can be regulated by the flow rate of the vent valve  154 . The higher the flow rate allowed by the valve the higher the release of in-diffused gases or boiled fuel  159 . The in-diffused gases are dependent upon the temperature of the fuel membrane  158 , and the boiling of the fuel  151 . The in-diffusion of gases and the vaporized fuel create a net source of gases in the fuel tank. By using a regulating valve  154  to vent gas  141  on the outlet tube the fuel tank pressure is regulated, the fuel delivery is regulated through the membrane contact, and subsequently the heat production is regulated. The fuel vapors  141  released by the regulating valve are combusted by a catalyst-coated sleeve  146 ,  155 ,  147  surrounding the vent line. Another mechanism of regulating catalytic combustion occurs when the fuel membrane  158  presses up against the aperture plate  152 , which can also cause the aperture plate  152  to compress the catalytic felt  143  against the outer heat loss surfaces  148 ,  157 . This reduces the insulation of the catalytic combustion felt  143 , cools the catalytic combustion and reduces the reaction rates.  
         [0072]    In FIG. 10 a cross-sectional view of the catalytic heater configured with a selectively permeable sealed fuel ampoule is shown. The fueling of the catalytic heater can be done by ampoules of fuel that deliver the fuel by diffusion through the walls of the ampoule. In this configuration of the catalytic heater, fuel ampoules  196  are formed by sealing a silicone rubber cylinder or bag containing methanol fuel  197  with silicone sealant. These ampoules  196  can be stored in a methanol impermeable container shown in FIG. 11 until use. A re-sealable methanol-impermeable, thermally conductive container such as an aluminum container  170 ,  192  that has a seal  180  around the rim is formed. The container is sealed from the outside (not shown) prior to use. There are many possible mechanisms for the sealing of the container  170 ,  192  one of which is a hinge and a clasp placed around the rim  190  compressing a rim gasket  180 . The aluminum container  170  has air in-diffusion holes in the container wall  191 . Within the methanol-impermeable, thermally conductive container  170 ,  192  the fuel ampoule  196  and PBI felt  193  are contained. The catalyzed felt  193  is formed by coating Pt/Ru on carbon support catalyst powder  194 , and a protective permeable coating DAIS  195 , and is placed next to the air in-diffusion holes  191 . In operation, the fuel ampoule  196  is placed in the container  170 ,  192  and clamped together. The methanol fuel diffuses to the catalyst  194  through the ampoule wall  196  and the protective catalyst coating  195 , while oxygen diffuses through the holes  191  in the aluminum case  192  and the catalyst protective coating  195  to the catalyst  194 . The methanol fuel and oxygen catalytically combust on the catalyst  194  and the products of water and carbon dioxide diffuse out through the protective coating, and the diffusion holes  191 . Some of the carbon dioxide product can diffuse into the fuel ampoule  196 . It will come to equilibrium and diffuse back out of the ampoule since it is sealed. The fuel will boil  198  when the temperature reaches its fuel boiling point. The fuel will condense  199  with subsequent heat transfer to the aluminum container  170 . When the fuel ampoule pressurizes, due to boiling of the fuel  198 , the ampoule  196  expands pressing against the catalytic felt  195 , 194 , 193  and pressing against the container wall  192 . This increases the heat transfer rate from the catalytic felt and can reduce the air diffusion path to the catalytic felt reducing the thermal output of the catalytic heater. Thus a self heat regulation mechanism is achieved in this device.  
         [0073]    In FIG. 11 a cross-sectional view of a selectively permeable fuel ampoule with fuel impermeable container is shown. The fuel ampoule is formed with methanol  182  inside a silicone rubber cylinder  183  and sealed with silicone rubber sealant. The fuel ampoule is then heat sealed inside a polyethylene bag  181 . The silicone rubber walls have a high permeability to methanol fuel, while the polyethylene bag has a low permeability. The outer container  181  enables the fuel ampoule  183  to be stored until needed. When the fuel ampoule is needed the polyethylene bag  181  is torn open and the ampoule  183  is placed into the heater device shown in FIG. 10. The more snug a fit to the silicone container, the more fuel can be stored and the lower the amount of dead volume within the polyethylene bag.  
         [0074]    In FIG. 12 a cross-sectional view of the catalytic heater configured with a pump ampoule is shown. In this configuration the heater has an elastic fuel ampoule and the fuel diffusion region is elastic or there is sufficient gas  201  in the tubing  200  to act as an elastic volume. The heater system is formed by a thermoplastic rubber (Santopreneâ thermoplastic rubber, Advanced Elastomer Systems, 388 S. Main St., Ste 60, Akron, Ohio 44311). The fuel bladder is formed by perimeter heat sealing with a thick wall membrane  218  and a thinner walled membrane  220 . The rubber is chosen to be impermeable to the methanol fuel and flexible. The fuel bladder  218  is filled with methanol fuel  219 . Attached to the fuel bladder are inlet and outlet couplings that have spring loaded  227 ,  228  seals  221 ,  217 . The fuel bladder  218  is coupled to the fuel hoses  200  and  212  with clamps  222 ,  216  or threaded couplings. The couplings  221 ,  217  seal to the fuel hoses  200 ,  212  with Vitonâ (Quality Gasket Company, 511 Gates Street, Philadelphia, Pa. 19128) rubber seals  223 ,  215 . The couplings are opened when hoses are clamped and the opening pins  224 ,  214  push the spring-loaded  228 ,  227  valves open. Two one-way valves  225 ,  213  are placed in the fuel hoses  200 ,  212 . The closing pressure of these one-way valves  225 ,  213  can be set by the closing force such as a restoring spring  226 ,  229 , and thereby set the minimum pressure needed to deliver fuel from the fuel bladder  218 ,  220 . From the one-way valves  225 ,  213  a hose connects to the fuel distribution bladder or capillary hoses  210 . The fuel distribution bladder is made of capillary tubes of silicone rubber  210 ,  230  with wall thickness of 0.5 mm to 0.025 mm thick (SiO flex tubing, Specialty Silicone Fabricators, 3077 Rollie Gates Drive, Paso Robles, Calif. 93446). Alternatively a silicone bladder  230  is made with a wall thickness ranging from 0.5 mm to 0.025 mm thick polyester reinforced silicone membrane  210  (Vulcanized Sheeting, Specialty Silicone Fabricators). A return fuel flow line  212  is connected between the fuel distribution bladder  210 ,  230  back to the second one way valve  213 . The fuel distribution bladder  210 ,  230  is placed in close proximity to the catalytic heating felt formed by coating a PBO felt  206  with Pt/Ru black  207  and overcoated with DAIS polymer electrolyte  208 . The catalytic felt  203  and the fuel distribution bladder  210 ,  230  are glued together with silicone rubber sealant to form a combustion volume  209  within an aluminum or silicone rubber box  204 . Air diffusion holes  205  perforate the aluminum box  204 . In operation the fuel tank is connected to the heater system by making the two connections  215 ,  223 . The fuel tanks can be pre-filled ampoules with the pin connection that bursts and/or opens the seals in the fuel connections. By pressing a finger on the fuel diaphragm  220  the fuel bladder  218  is pressurized and fuel  219  flows through the first coupling  221 , the first one way valve  225  and through the tube  200  to the fuel distribution bladder or capillary tube  230 . The second one way valve  213  is closed to flow back toward the fuel distribution bladder  230 . The opening spring  226 ,  229  force on the one-way valves  225 ,  213  is set high enough to keep the valves closed to avoid gravitational hydraulic pressure causing a siphoning and the fuel to flow freely. When the finger pressure is relieved from the tank diaphragm  220  the first one-way valve  225  is closed and the second valve  213  opens when the pressure is low in the fuel bladder  218 . This draws fuel  219  and fuel vapor  211  out of the fuel distribution bladder  230 . When the methanol fuel  219  is in the distribution bladder  230  the fuel diffuses out through the membrane  202  to catalyst felt volume  209 . The methanol fuel  219  diffuses to the surface of the catalyst coating  208  and through to the catalyst surfaces  207 . Oxygen simultaneously is diffusing through the air inlet holes  205 , into the catalyst-felt volume  209  and through the catalyst coating  208  to the catalyst  207 . The oxygen and methanol fuel catalytically combusts on the surface of the catalyst  207 . The products of water and carbon dioxide diffuse back through the catalyst surface coating  208 , into the catalyst felt volume and out through the air inlet holes  205 . When the catalytic combustion delivers sufficient heat energy to cause the fuel to boil the fuel distribution bladder  210 ,  230  pressurizes. This pressurization causes the second one-way valve  213  to open and the methanol vapor  211  and liquid  219  flows into the fuel bladder  218 . The methanol vapor will condense in the fuel bladder  218 . The pressurization of the fuel distribution bladder from vaporized fuel and in diffusion of gasses due to the boiling of the fuel also results in the diffusion membrane  210  bulging and compressing the catalytic felt  203  against the container wall  204 . This increases the thermal conductivity from the catalytic sites  207  to the outside air and cooling the catalyst  207 . By compressing the catalytic felt  203  against the wall, the space available for diffusion of oxygen also decreases and the oxygen diffusion to the catalytic sites  203  is reduced, thereby reducing the rate of catalytic combustion. The catalytic sites cool and the methanol fuel  211  cools thereby giving this catalytic combustion system temperature feedback control. The pumping of fuel can be used as a feature in applications, such as in apparel where the user presses the fuel tank bladder  220  to receive a pulse of heat. This allows the user to control the time and amount of heating.  
         [0075]    Essential features:  
         [0076]    1. Fuel delivered though a selectively permeable membrane.  
         [0077]    2. The selectively permeable membrane allows fuel to be delivered and not back diluted by the product water.  
         [0078]    3. A selectively permeable membrane to allow oxygen and with a reduced permeability to fuel to retain fuel.  
         [0079]    4. The carbon dioxide and other gasses diffuse into the membrane and vent and circulate through the fuel with the fuel boiling.  
         [0080]    5. A catalyst dispersed over a porous material.  
         [0081]    6. A fuel and oxidizer permeable protective coating over the catalyst.  
         [0082]    7. A selectively permeable coating over the catalyst.  
         [0083]    8. A fuel retaining coating over the catalyst.  
         [0084]    9. A coating over the catalyst that enhances the performance of the catalyst.  
         [0085]    10. A coating over the catalyst that is electrolytic and or acidic or basic.  
         [0086]    11. The fuel vaporization and departure from the membrane to catalyst reaction area to act as a thermostat of upper temperature limit mechanism.  
         [0087]    12. Valving or flow restrictions to regulate the boiling or fuel filling to regulate temperature of heating rates.  
         [0088]    13. Using fuel additives such as water or other hydrocarbon fuel with different boiling points to adjust the catalytic burner temperatures.  
         [0089]    14. Using the fuel vaporization and condensation as a heat pipe heat exchanger.  
         [0090]    15. The onset of boiling of the fuel to keep the reaction area temperature elevated.  
         [0091]    16. To incorporate thermopiles to extract electrical energy from the heater and transfer heat.  
         [0092]    17. To use heat exchangers to warm up air going to the heater and exchange heat with the load.  
         [0093]    18. Extracting water from the condensation of the exhaust from the heater.  
         [0094]    19. Use a selectively permeable membrane to regulate the oxidizer to the catalyst reaction area.  
         [0095]    20. Use of stoma devices to thermally regulate the oxidizer gas to the catalyst area.  
         [0096]    21. Use of fans or pumps to regulate the fuel or oxidizer delivery to the catalyst area or heat exchange.  
         [0097]    22. The use of electrochemical catalysis to enhance the performance.  
         [0098]    23. Use of electric heating to start the catalytic heater.  
         [0099]    24. Use of passive mechanical controls and pressurization of the fuel to control the heat output.  
         [0100]    25. Use of a wick to distribute fuel over the selectively permeable membranes.  
         [0101]    26. Use of the heater on many systems, apparel, blankets, machinery, dwellings, shipping containers, storage containers insect attractants, humidifiers, and perfume generators.  
         [0102]    While the invention has been described with reference to specific embodiments, modifications and variations of the invention may be constructed without departing from the scope of the invention, which is defined in the following claims.

Technology Category: y