Catalytic Heating System and Method for Heating a Beverage or Food
A catalytic heating system for heating a beverage or food that comprises: a container for containing the beverage or food and a catalytic combustion assembly for heating the container, with the catalytic combustion assembly comprising a fuel supply assembly having a fuel canister for supplying a fuel gas having a stoichiometric ratio of about 15 to an air mixing injector for injecting the fuel gas into an elongate sidewall enclosure having curved shape and defining an enclosed catalytic combustion chamber where a catalytic combustion process is generated, causing the complete combustion of all of the fuel gas and heating the container containing the beverage or food.
This application is a continuation-in-part of U.S, application Ser. No. 14/988,526, filed on Dec. 31, 2015, which h a continuation of International Application No. PCT/US2015/38456. filed on Jun. 30, 2015. which claims the benefit of U.S. Provisional Application No. 60/059,510, filed on Oct. 3, 2014.
TECHNICAL FIELDThis application relates to the use of systems and methods for the generation of heat for use in heating portable containers containing beverages or food, and more specifically to systems and methods for the generation of catalytically produced heat within an enclosed catalytic combustion chamber for heating a container containing a beverage or food. Background Art
Portable heating systems, such as camping stoves and lanterns, are well known in the art of designing and manufacturing such systems. Camping stoves generally utilize an open or partially open flame to heat the stove's contents, with an aerosol canister containing a pressured fuel, typically butane or propane or a combination of those fuels, to supply the fuel needed to maintain the flame. Lanterns, on the other hand, operate similarly to produce light. These devices have several well-known limitations, with the most obvious being the use of an open flame and the fire danger it possess. Other less obvious limitations are related to the chemical characteristics of butane and propane.
The working pressure available from fuel canisters containing butane (either iso- butane or n-butane) or propane or a mixture of such gases is effected by variations in temperature that create conditions that are not ideal for operating heating or lighting systems over a wide range of ambient temperatures and altitudes Specifically, the useful working pressure for butane at lower ambient temperatures drops off significantly such that the proper operation of a heating or lighting device is impaired. Propane allows for operation at low ambient temperatures but requires a heavier and more expensive fuel canister to safely handle pressures that are normally encountered at higher ambient temperatures. Mixed fuel combinations of butane and propane have been developed to minimize the impact of pressure and temperature variation. But these combinations still suffer from a tendency of the more volatile components of the combined fuels, which have lower boiling points, to be used up sooner than the less volatile fuel components, resulting in unsatisfactory pressure remaining in the fuel canister as it is depleted, especially under cold conditions.
In addition to the limitations in using butane and propane to fuel an open flame device, butane and propane also have other significant limitations related to their potential use as a fuel source for a catalytic combustion process. An important characteristic for any fuel used in catalytic combustion is the light-off temperature, which is a rough indicator of the propensity for the fuel oxidation reaction to proceed. Light-off temperature is often defined as the temperature at which the conversion rate for the reactants reaches 50%, abbreviated as T50. A low T50 assists in the complete conversion of the fuel to heat without producing intermediate reaction products and pollutants, which may occur when trying to operate the catalytic combustion process at relatively low temperatures. A sufficiently low T50 value will also allow for catalytic reactor designs that can use light weight metals such as aluminum without concern for exceeding material temperature limits or causing catalyst deterioration. The fuel gasses commonly, used such as butane and propane, all have relatively high T50 values, limiting the possible material design choices and catalytic reactor operating parameters for the heating catalytic combustion chamber. The higher operating temperatures may also introduce unwanted design choices necessary to insure safe operating conditions for the user. Prior art is deficient in describing means for insuring fail-safe operation of catalytic heating in a wide variety of circumstances. Irrespective of fuel type, the prior art does not show how to adapt catalytic heating, to applications, such as, self-heated: temperature regulated portable beverage heating or cooking applications in a manner that assures a high degree of operational safety using techniques that are cost effective. Prior art also does not show how compressed gas fuel used in catalytic heat generation can be safely applied to an indoor application or while inside a transport vehicle, or any small enclosure such as a tent. All of these shortcomings, as well as, others associated with prior art catalytic, heat generating devices, limit their applications or area of use.
In view of these and other problems in the prior art, it is a general object of the present invention to provide an improved apparatus and method utilizing a catalytic heat generating device that overcomes the drawbacks relating to the compromise designs of prior art devices as discussed above. Another object of the present invention is to provide a passive technique, which requires no externally provided power, for pre-mixing air and fuel which will provide air to fuel equivalence ratios of one or more when coupled to reactors that have relatively high back pressures.
SUMMARY DISCLOSURE OF THE INVENTIONA catalytic heating system for heating a beverage or food is presented that comprises: a container for containing the beverage or food, and a catalytic combustion assembly for heating the container that comprises: a chamber plate integral with the bottom of the container; an elongate sidewall enclosure integral with the chamber plate, with the elongate sidewall enclosure having a fuel gas inlet and an exhaust outlet within corresponding ends of the elongate sidewall enclosure, and with the elongate sidewall enclosure defining an enclosed catalytic combustion chamber; a catalytic reaction media disposed within the enclosed catalytic combustion chamber, a combustion starting element disposed within the enclosed catalytic combustion chamber; a fuel supply assembly mounted on a fuel supply platform, with the fuel supply assembly having a fuel and air mixing injector fluidly connected to the fuel gas inlet a fuel canister sealably connected to the fuel supply platform and fluidly connected to the fuel supply assembly; and a fuel gas contained within the fuel canister. And, a shell containing the container and catalytic combustion assembly forms the catalytic heating system for heating the beverage or food. In operation the fuel and air mixing injector within the catalytic heating system can entrain the fuel gas with air and inject a fuel gas and entrained air mixture into the enclosed catalytic combustion chamber where the combustion starting element can ignite the fuel gas and entrained air mixture, and the catalytic reaction media can maintain a catalytic combustion process within the enclosed catalytic combustion chamber, and the catalytic combustion process can combust all of the fuel gas and heat the container containing the beverage or food.
A method of heating a container is also presented that comprises: providing for a flow of a fuel gas, with the fuel gas having a stoichiometric ratio of about 15, increasing the velocity of the flow of the fuel gas; entraining the flow of the fuel gas with air, thereby creating a flow of fuel gas and entrained air mixture; maintaining an entrapment ratio of about 15 or above for the flow of fuel gas and entrained air mixture; constraining the flow of fuel gas and entrained air mixture to an enclosed curved path; contacting the flow of fuel gas and entrained air mixture with a catalytic reaction media; igniting the flow of fuel gas and entrained air mixture, thereby generating the catalytic combustion process; combusting all of the fuel gas during the catalytic combustion process; and conducting heat from the catalytic combustion process to the container.
The container 16 and catalytic combustion assembly 18 can be secured to the outer shell 2 by bonding an outside top perimeter of the container 16 to an inside top perimeter of the outer shell 2. And, the fuel supply platform 24 can be secured to the outer shell 2 by using the plurality of screws 12 to attach an inside perimeter of the outer shell 2 to an outside perimeter of the fuel supply platform 24. The shell lid 4 can be removably attached to a top end of the outer shell 2 by screwing the shell lid 4, having female threads around its inside perimeter, to the outer shell 2, having male threads around its top outside perimeter. The container 16 can be any container that can conduct heat, such as a cup, mug or sauce pan; preferably the container will have a metallic composition. And, the outer shell 2 can be made of a thermally non-conductive material, preferably a polymeric material; alternatively, the container 18 can have a thermally insulating layer disposed between a sidewall 17 of the container 16 and the outer shell 2.
The components of the catalytic combustion assembly 18 are illustrated in more detail in
The elongate sidewall enclosure 32 preferably should have a diameter that is relatively small in order to ensure that the curved portion of the sidewall enclosure 32 can bend in a smooth and continuous fashion within the coupled chamber plates 20 and 22; and in order to more evenly distribute the heat generated from the enclosed catalytic combustion chamber 30 to the top chamber plate 20 that forms the bottom of the container 16 which, in turn, provides for a more even distribution of heat to the beverage or food. At the same time, however, the elongate sidewall enclosure 32 should have a diameter and total length that are large enough to contain a sufficient quantity of catalytic reaction media 40 over the length of the elongate sidewall enclosure 32 to produce a sufficient amount of heat to effectively heat the top chamber plate and the beverage or food within container 16. Given these considerations, the inventors have determined that the elongate sidewall enclosure 32 preferably should have a diameter of about 10 millimeters or less, and more preferably between about 5 and 10 millimeters. The elongate sidewall enclosure 32 also has a flow-through fuel gas inlet 32C within one end of the sidewall enclosure 32 and a flow-through exhaust outlet 32D within the other end of the sidewall enclosure 32, with the sidewall enclosure 32 having no other flow-through openings within the sidewall enclosure 32. And, as shown in
It is preferred that the top and bottom chamber plates, 20 and 22, can be coupled together by utilizing a plurality of binder posts 3B, with top portions of the binder posts 38 disposed within corresponding openings the top chamber plate 20, with bottom portions of the binder posts 38 disposed within corresponding openings through the bottom chamber plate 22, and with bottom ends of the binder posts 38, which extend away from the bottom surface of the bottom chamber plate 22, used to couple the top chamber plate 20 to the bottom chamber plate 22 by flattening the ends of the binder posts 38 against the bottom surface of the chamber plate 22. Preferably, the top and bottom chamber plates. 20 and 22, have a metallic composition.
Before the enclosed catalytic combustion chamber 30 is formed by coupling the top and bottom chamber plates, 20 and 22, the catalytic reaction media 40 preferably can be positioned in a curved orientation, as shown in
Once the catalytic reaction media 40 and combustion element 50 are positioned within the curved bottom channel 22 A and the top chamber plate 20 is coupled to the bottom chamber plate 22, the catalytic reaction media 40 and the combustion element 50 are captured in a curved orientation within the curved sidewall section 32A of the elongate sidewall enclosure 32, thereby defining the enclosed catalytic combustion chamber 30 as having the same shape as the elongate sidewall enclosure 32 In this regard, a curved elongate shape for the enclosed catalytic combustion chamber 30 is preferred in order to more evenly distribute the heat from the combustion chamber 30 to the top chamber plate 20 and, thereby, provide for a more even distribution of heat to the beverage or food within container 16. And, the most preferred curved elongate shape for the enclosed catalytic combustion chamber 30 is a curvature having a constant radius of curvature (hereinafter referred to as a “circular curvature”), providing a smooth and continuous surface within the combustion chamber 30. Although the enclosed catalytic combustion chamber 30 having a circular curvature is preferred, other curved catalytic combustion chamber shapes could be utilized. For example, a serpentine shape within a chamber plate 25′, as illustrated in
While there are several types of catalytic reaction media known in the art, the catalytic reaction media 40 preferably is an open cell metal foam substrate, combined with a wash coat and an active catalyst. It has been discovered that the use of an open cell metal foam substrate constructed from an iron, chromium, aluminum and yttrium alloy, under the trade name Fecralloy® or Kanthal® and manufactured by Porvair, Inc., provides an ideal substrate material for the catalytic reaction media 40. Metal foam substrates tend to have very high surface area to volume ratios and very high porosities. The first property is important to enhance the number of catalyst sites per unit volume, which affects the catalytic space velocity (i.e. quotient of the entering volumetric flow rate of the reactants divided by the reactor volume) in the enclosed catalytic combustion chamber 30 and the second property helps to minimize the pressure drop within the enclosed catalytic combustion chamber 30. The particular type of metal foam fabrication technique is important in determining the properties that make for an optimum catalyst media. Metal foams can be constructed by several techniques such as sintering or investment casting. The heat transport properties of metal foams made by sintering are very different than those made by investment casting and are far less costly. Sintered metal foams, such as the ones manufactured by Porvair Inc., have a unique micro-structure that resembles interconnected open cells in the shape of dodecahedrons. The cells are constructed of a series of interconnected metal struts. A cross-section of each strut would show it to be a hollow shell. The resulting light mass allows the material to reach high temperatures with very little energy input. This in turn helps to minimize the energy required by the starter filament to start the reaction. The metal substrate is traditionally given a wash-coat of some very high surface area material (e.g. gamma alumina) upon which a catalyst is deposited (e.g. Platinum). The Fecralloy® alloy contains aluminum, which under a suitable heat treatment will be driven to the surface where it is converted to alumina when exposed to a high temperature oxidizing atmosphere. The conversion to alumina provides a bonding interface if an alumina wash coat is utilized. However, it has been discovered that two additional properties exist that can be used advantageously when the Fecralloy® alloy is used as the catalytic reaction media 40. The first property is that the self-generating aluminum oxide film can act as its own wash coat, albeit of less surface area than a traditional gamma alumina wash coat. In some catalytic reactor designs this may provide an adequate catalyst site attachment points and consequently sufficient catalyst activity levels. By eliminating the traditional wash-coat step, costs are reduced. The second surprising additional property is that the Fecralloy material, after heat treating to induce a native film of aluminum oxide, appears to have a certain amount of inherent catalytic activity on its own, without adding additional catalysts. This further reduces costs by reducing the amount of additional catalyst required to attain a specific space velocity. Although alumina coated cell foam substrates coaled with an active catalyst are preferred, other catalytic reaction can also be used. For instance, free standing porous alumina substrates coated with an active combustion catalysts or flow-through monoliths such as wash coated cordierite with and active catalyst coating could be used as well.
The fuel supply assembly 26 further comprises the programmed microprocessor 60 that is attached to and in electrical connection to a circuit board 74 that is mounted on the top side of the fuel supply platform 24. A battery 76, such as a lithium polymer type GM502030 from PowerStream Technology, Inc., can also be attached to and in electrical connection to the circuit board 74; or the battery 76 can be attached to any other appropriate location within the catalytic combustion assembly 18 or within the outer shell 2 surrounding the catalytic combustion chamber 18. The battery 76 supplies electrical power to the programmed microprocessor 60 when the on/off button 8 is in the “on” position and disconnects electrical power when the on/off button 8 is in the off position. When activated, the programmed microprocessor 60, with inputs from the temperature sensors 72A and 72B, controls the functionality of the solenoid valve 68 in order to control the fuel gas flow rate and temperature within the enclosed catalytic combustion chamber 30. The activated programmed microprocessor 60 also supplies electrical power to the combustion starting element 50, which the microprocessor 60 coordinates with the supply of fuel gas to the enclosed catalytic combustion chamber 30 by opening and closing the solenoid valve 68.
The cross-sectional side view presented in
Specifically, operation of the catalytic heating system 1 can proceed by providing a flow of the dimethyl ether fuel gas 29 by attaching the fuel canister 28, containing the dimethyl ether fuel gas 29, to the fuel supply platform 24, by screwing the fuel flow valve 88 into the platform receptacle 78, which causes the tap within the fuel gas compression fitting 62 to open the fuel flow valve 86 and causes the dimethyl ether fuel gas 29 within the fuel canister 28 to flow through compression fitting 62 and into the fuel supply assembly 26. The dimethyl ether fuel gas 29 will initially flow through the liquid/gas separator 64, where any fuel gas in liquid form will be removed, and then flow through the pressure regulator 66 that will maintain the fuel gas below a predetermined pressure, and continue flowing until it reaches the solenoid valve 68. With the on/off button 8 in the “off” position, the solenoid valve 68 will be closed, which prevents the dimethyl ether fuel gas 29 from flowing into the fuel and air mixing injector 70. Next the catalytic heating system 1 can be operated to heat a beverage or food by, if necessary, removing the shell lid 4 by unscrewing it from its engagement with the top of the outer shell 2. A beverage or food can then be placed into the container 16 and the shell lid 4 reattached to the outer shell 2. The catalytic combustion process that is utilized to heat the beverage or food is initiated by depressing the on/off button 8 to the “on” position, which activates the programmed microprocessor 80 by closing the circuit connection between the battery 78 and programmed microprocessor 60. At a predetermined time after activation, the programmed microprocessor 60 causes the solenoid valve 68 to open, causing the dimethyl ether fuel gas 29 to flow into the fuel and air mixing injector 70. As the dimethyl ether fuel gas 29 flows through the fuel and air mixing injector 70, the velocity of the fuel gas flow 29 will increase due to the distal narrowing of the injector 70. Increasing the velocity of the dimethyl ether fuel gas 29 causes the pressure in the fuel and air mixing injector 70 to decrease, thereby entraining the dimethyl ether fuel gas 29 with atmospheric air in order to produce a dimethyl ether fuel gas and entrained air mixture, while maintaining an entrapment ratio of about 15 or more parts air to about one part dimethyl ether fuel gas 29 for the mixture. The dimethyl ether fuel gas and the entrained air mixture is injected by the fuel and air mixing injector 70 into the flow-through fuel gas inlet elbow 34 and then into the elongate sidewall enclosure 32 defining the enclosed catalytic combustion chamber 30, thereby constraining the flow of the mixture though the enclosed catalytic combustion chamber 30 to the curved and linear path best illustrated in
In addition to the advantages relating to the size and shape of the elongate sidewall enclosure 32 described above, the catalytic heating system 1 provides another beneficial feature related the combustion of the dimethyl ether fuel gas 29 and entrained air mixture within the enclosed catalytic combustion chamber 30. In particular, catalytic combustion process within the enclosed catalytic combustion chamber 30 is confined to the enclosed catalytic combustion chamber 30 defined by the elongate sidewall enclosure 32, with the only openings within the sidewall enclosure 32 being the flow-through fuel gas inlet 32C at one end of the sidewall enclosure 32 and the flow-through exhaust outlet 320 within the opposite end of the sidewall enclosure 32. This feature provides for a controllable and safe combustion process, including the feature of being able to safely transport all of the exhaust from the catalytic combustion through a single flow-through outlet to the environment outside of the catalytic heating system 1.
An inherent thermodynamically related limitation to the ability to achieve the complete combustion of all of the fuel gas in a catalytic combustion chamber is that the combustion process itself generates an amount of pressure in the chamber, generally referred to as “back pressure”, that can prevent complete combustion of the fuel gas. Other factors that can also contribute to an increase in back pressure are related to fluid mechanical limitations involving the geometry of the combustion chamber. In this regard, it is to be reasonably expected that a catalytic combustion process within the enclosed catalytic combustion chamber 30 within catalytic heating system 1 would produce more back pressure than would be expected from the catalytic process itself. This expected increase In back pressure is due to the unique geometry of the enclosed catalytic combustion chamber 30. defined by the partially curved and cylindrical shaped elongate sidewall enclosure 32, and due to the fact that the sidewall enclosure 32 has a single flow-through fuel gas inlet 32C and single flow-through exhaust outlet 32D, with no other flow-through openings within the sidewall enclosure 32. And, in fact, as will be described in more detail below, during the development of me catalytic heating system 1, the inventors determined that neither butane nor propane could be used to overcome the back pressure generated in the enclosed catalytic combustion chamber 30 and achieve the complete combustion of the fuel gas. Achieving complete combustion of the fuel gas in the enclosed catalytic combustion chamber 30 is important because incomplete combustion results in the inefficient utilization of the fuel gas and due to the fact that incomplete combustion can also release toxic substances into the environment and potentially inhaled by a user of the catalytic heating system 1.
From a fluid mechanics standpoint, one way to overcome back pressure and obtain complete combustion of the fuel gas within the enclosed catalytic combustion chamber 30 within the catalytic heating system 1 is to reduce the total amount of work energy required to overcome both the back pressure and the energy needed to carry large quantities of entrained air through the combustion chamber 30 and out the exhaust. A fixed amount of kinetic and potential energy is imparted to the fuel gas stream as it first enters the fuel and air mixing injector 70. The amount of energy the fuel gas stream obtains as it enters mixing injector 70 is dependent upon the fuel gas pressure, the density of the fuel gas, and the geometry (i.e. size and shape) of the mixing injector 70 orifice. With these principals in mind, the inventors of the catalytic heating system 1 carried out experiments to determine if complete combustion in the enclosed catalytic combustion chamber 30 could be attained using either butane or propane, which are the fuel gases used in other portable heating devices for heating beverages or food. In order to achieve a complete combustion of the butane fuel gas, the stoichiometric ratio of butane, about 32 parts of air to one part of fuel, requires the fuel and air mixing injector 70 to produce a butane fuel gas and entrained air mixture having an entrapment ratio also of about 32 or more parts of air to one part of fuel. Similarly, in order to achieve a complete combustion of the propane fuel gas, the stoichiometric ratio of propane, about 25 parts air to one part fuel, dictates that the fuel and air mixing injector 70 produce a propane fuel gas and entrained air mixture having an entrainment ratio also of about 25 parts or more of air to one part of fuel In their experiments, however, the inventors found that it was not possible to overcome back pressure and achieve complete combustion within the enclosed catalytic combustion chamber 30 using butane or propane as a fuel source. It was believed that this might have been due, at least in part, to the fact that attaining complete combustion using butane or propane as the fuel gas with the catalytic heating system 1 requires that air comprise a substantially greater percentage of the fuel gas and entrained air mixture due to the relatively high stoichiometric air to fuel ratios of these fuels. This in turn requires the fuel and air mixing injector 70 to provide relatively high entrainment ratios. The high entrainment ratios required by butane and propane contributes to a substantial increase in the work energy required to entrain air within the fuel and air mixing injector 70, leaving less energy available to perform the work necessary to flow the fuel and entrained air mixture through the enclosed catalytic combustion chamber 30. This explains, at least in part, the inability to overcome back pressures that can arise within the enclosed catalytic combustion chamber 30 when butane or propane is used as the fuel gas source.
A potential solution to this inability to overcome back pressure and achieve the complete combustion within the catalytic heating system 1 would be to use a different fuel having a lower stoichiometric ratio, allowing for a lower entrainment ratio required to achieve complete combustion in the enclosed catalytic combustion chamber 30. The ideal fuel gas would be one with a stoichiometric air to fuel ratio lower than the stoichiometric air to fuel ratios of butane or propane that would, therefore, give rise to less kinetic energy required to entrain air injected by the fuel and air mixing injector 70 into the enclosed catalytic combustion chamber 30, while still providing the same beneficial properties of butane and propane, such as being readily stored in a liquid state at pressures and temperatures compatible with portable consumer products. In fact the inventors experimentally determined that dimethyl ether fuel gas 29 unexpectedly produces sufficient kinetic energy of the fuel gas to entrain an adequate amount of air as it exits the fuel and air mixing injector 70 and still have sufficient amount of kinetic energy remaining to overcome back pressure and achieve complete combustion within the enclosed catalytic combustion chamber 30.
In order to achieve a complete combustion of the dimethyl ether fuel gas 28 within the enclosed catalytic combustion chamber 30, the stoichiometric ratio of the dimethyl ether, about 15 parts of air to one part of fuel, requires the fuel and air mixing injector 70 to produce a dimethyl ether fuel gas 29 and entrained air mixture that has an entrainment ratio of about 15 or more parts of air to one part of fuel. In this regard, given identical flow through conditions within the fuel and air mixing injector 70, the inventors determined that, based upon fluid mechanical principles, the exit velocities from the mixing injector 70 for all three gasses should be within about 10% of each other. Thus, the kinetic energy available for driving the flow of fuel gas and entrained air mixture through the enclosed catalytic combustion chamber 30 should be roughly similar for each gas. As a result, the inventors hypothesized that dimethyl ether might have enough kinetic energy available to outperform butane and propane and possibly be able to overcome enough back pressure within enclosed catalytic combustion chamber 30 to achieve the complete combustion of the dimethyl ether. In fact, in experiments carried out by the inventors, they confirmed that their hypothesis was correct in that the experiments demonstrated not only was the utilization of dimethyl ether able to overcome more back pressure than butane and propane but that the complete combustion of the dimethyl ether was surprisingly achieved in the combustion chamber 30 within the catalytic heating system 1. The specific results of the inventors' experiments are summarized in the Table I below:
As shown in the table, the inventors measured the quantity of air that was contained in the exhaust from using dimethyl ether, butane, and propane as the fuel gases that were combusted within in the catalytic combustion process within the catalytic heating system 1 as described above. In this regard, the specific dimensions for the cylindrical shaped elongate sidewall enclosure 32, enclosing and defining the enclosed catalytic combustion chamber 30, utilized in the experiments were the following: diameter=6.3 mm; radius of circular curvature=16.5 mm; length of circular curvature=50 mm; length of each linear section=4 mm; and overall length of the elongate enclosure from the fuel gas inlet to the exhaust outlet duct=85 mm. The catalytic combustion process utilizing dimethyl ether generated an exhaust containing about 10% more air than required to maintain a complete combustion of the dimethyl ether in the enclosed catalytic combustion chamber 30, establishing that all of tee dimethyl ether was combusted. The results for butane and propane, however, demonstrate that butane and propane generated 30% and 15% less air, respectively, than would have been required to completely combust those fuel gasses, meaning that not all of the butane or propane was completely combusted.
Another unexpected result of using dimethyl ether fuel gas 29 as the fuel source for the catalytic heating system 1 arises from thermodynamic considerations that pertain to light-off temperature, which is often defined as the temperature, often abbreviated as T50 , at which 50% of the fuel gas has been combusted within the combustion chamber. Since the light-off temperature of dimethyl ether is significantly lower than the light-off temperature of butane and propane, complete combustion of dimethyl ether in a catalytic combustion process occurs at a significantly lower temperature than either butane or propane, which also indicates that the complete combustion of dimethyl ether generates less back pressure that butane or propane. As a result the combination of a low entrainment ratio and a low light-off temperature can be expected to work together to reduce back pressure within the enclosed catalytic combustion chamber 30.
In addition, the ability to achieve complete combustion of the dimethyl ether fuel gas 29 in the enclosed catalytic combustion chamber 30 gives rise to another unexpected result related to potential flame propagation within the combustion chamber 30. In any catalytic reaction process within a combustion chamber it is important to limit or prevent flame generation inside or outside of the chamber. For example, if a combustible mixture of fuel gas and air were to accumulate in a region outside of the reaction chamber it would be desirable to Insure that no flame could be generated as a result of the catalytic reaction occurring within the reaction chamber. Similarly, if the temperature within the reaction chamber were to reach levels at or above the lowest temperature at which the fuel gas will spontaneously ignite without an external source for ignition, generally referred to as the “auto-ignition temperature”, flame propagation events could become more likely and should be prevented. In this regard, it has been reported that in order to achieve this result the chamber geometry should have certain dimensional relationships. In particular, reaction chambers, like the enclosed catalytic combustion chamber 30 that are elongated and cylindrical shaped, surprisingly provide the foundation for limiting or preventing flame propagation events. In this regard, an important parameter related to the shape of the reaction chamber is the critical flame quenching diameter. Cylindrical chambers with diameters below this critical value will not allow flames to propagate, and it is generally known that quenching diameters for most hydrocarbon fuels, including dimethyl ether, are in the range of about 10 millimeters or less for mixtures that have an air to fuel equivalence ration of between about 0.6 and 1.0 (e.g., Proceedings of the International Conference on Heat Transfer and Fluid Flow, Prague, Czech Republic. Aug. 11-12, 2014, Paper No. 36:“Quenching Distance and Quenching Diameter Ratio for Flame Propagating in Propane/Air mixtures”, by Arthur N. Gutkowski and Teresa Parra Santos). This critical flame quenching diameter unexpectedly overlaps the preferred diameter of the elongate enclosure 32 enclosing the combustion chamber 30 of between 5 and 10 millimeters. More specifically, by simply specifying that the elongate enclosure 32 preferably has a diameter of about between 5 and 10 millimeters, the catalytic heating system 1 is able to surprisingly achieve the unrelated favorable effects of: 1) an evenly distributed heating pattern for heating the beverage or food and simultaneously fill the enclosed catalytic combustion chamber 30 with a sufficient amount of catalytic reaction media 40 to achieve an adequate heating power to heat the beverage or food; and 2) preventing or limiting flame propagation within the enclosed catalytic combustion chamber 30.
Although dimethyl ether is known to be useful as a fuel source in some contexts, the fuel is not disclosed as a fuel source in a catalytic combustion application as disclosed by the catalytic heating system and 1. And, there are reasons why persons skilled in the art of open flame devices have utilized fuels like butane and propane; rather than dimethyl ether as a potential fuel gas source. One such reason is that dimethyl ether has an energy density of about 68,930 BTU/cubic foot, which is notably less than the energy densities of butane and propane, with butane having an energy density of about 94,000 BTU/cubic foot and propane having an energy density of about 84,250 BTU/cubic foot. Since devices for heating beverages and food have limited amounts of stored fuel gas, it is desirable to use fuel gases like butane and propane with high energy densities so that sufficient heating can be produced with a minimum amount of fuel. Dimethyl ether, with its lower energy density, would most likely not be considered as a suitable alternative. The inventors have surprisingly discovered, however, that due to the combination of dimethyl ether's relatively low light-off temperature, low stoichiometric air to fuel ratio, and a more ideal vapor pressure characteristic, these advantages outweigh the potential disadvantage of the lower energy density of dimethyl ether as a fuel gas utilized in the catalytic heating system and 1.
Another reason that dimethyl ether might not be considered as an acceptable fuel source is that ether compounds are generally known to have the characteristic of forming dangerous peroxide compounds when exposed to air. However, the inventors of the catalytic heating system 1 have determined that dimethyl ether does not exhibit that characteristic.
In addition to having a relatively low entrainment ratio and light-off temperature that combine to achieve complete combustion within the catalytic heating system 1, the utilization of dimethyl ether fuel gas 29 as the fuel source for the catalytic heating system 1 has other unexpected advantages over other fuel gases like butane and propane. One such advantage is that the use of the dimethyl ether fuel gas 29; allows the catalytic heating system 1 to be operated at altitudes above sea level, while still achieving complete combustion. This advantage can be implemented by setting the fuel and air mixing injector 70 to inject less fuel gas into the enclosed catalytic combustion chamber 30, causing the chamber 30 to receive a fuel gas and entrained air mixture having an entrainment ratio somewhat higher than the ratio needed for achieving complete combustion in the chamber 30 at sea level Although the “lean” fuel gas condition would prevent the consumption of all of the air injected into the chamber 30, complete combustion of the fuel gas would still be achieved. Then, as the catalytic heating system 1 is operated at increasingly higher altitudes above sea level, the fuel and air mixing injector 70 will increasingly deliver a richer mixture of air and fuel gas, until reaching an altitude where the mixture will produce a stoichiometric condition, where all of the air and fuel gas are being utilized in a complete combustion process within the enclosed catalytic combustion chamber 30. Fuel gases, such as butane and propane, that require a higher entrainment ratio at sea level than dimethyl ether will not be able to achieve a stoichiometric condition at an altitude as high as that achievable by dimethyl ether. Thus, the catalytic heating system 1 that utilizes the dimethyl ether fuel gas 29 as its fuel source is surprisingly more useful over a greater range of altitudes above sea level than other fuels having higher entrainment ratios.
The catalytic heating system 1 has still other surprising advantages over other devices that use butane or propane to heat beverages or food. Dimethyl ether has a useful working pressure at lower ambient temperatures than butane, thus, enhancing the usefulness of dimethyl ether in outdoor applications. And, although propane can be used at lower temperatures, it cannot be used in lighter weight and less expensive canisters mat comply with Department of Transportation regulation DOT 2Q but must be used in much heavier and more costly canisters. Dimethyl ether, on the other hand, can be used in canisters that comply with the regulation and at a lower cost.
In this regard, a common approach to improve the useful working pressure at lower ambient temperatures is to combine a mix of high and low boiling point liquefied gases. The graph depicted in
The catalytic heating system 1 for heating a beverage or food is also substantially safer than flame based systems used for the same purposes. Flame based systems obviously present a potential that the open flame could ignite flammable objects in the environment. For example, if a flame based device tips over inside a camping tent, it will almost certainly start a fire inside the tent if the flame contacts a sleeping bag or clothing. Since the catalytic combustion process that takes place in the catalytic heating system 1 does not generate a flame and burns a much lower temperature than a flame based system, it is much less likely to start a fire under the same conditions.
Another surprising advantage of the catalytic heating system 1 is that the fuel supply assembly 26 and electronic components, comprising the programmed microprocessor 60 and battery 76, are all mounted on the fuel supply platform 24. The advantage of this feature is that when the fuel canister 28 releases the dimethyl ether fuel gas 29 into fuel supply assembly 26, the Joule-Thompson effect, which occurs during expansion of most gases, including dimethyl ether, cools the fuel supply assembly 28 and fuel supply platform 24, which, in turn, cool down the circuit board 74 containing the microprocessor 60 and battery 76. Consequentially, the distance between the fuel supply platform 24 and the bottom chamber plate 22 only needs to be sufficient to make room for the fuel supply assembly 26, without concern that the convective and radiant heat from the bottom chamber plate 22 will cause an overheating of the circuit board 74 and its electronic components. This cooling effect unexpectedly allows for a more compact design for the catalytic heating system 1.
In an another embodiment, a catalytic heating system 100 for heating a beverage or food as described is described in
The container 120 can be secured to the upper shell module 102 by bonding an outside top perimeter of the container 120 to an inside top perimeter of the upper shell module 102 and by similarly bonding an outside bottom perimeter of the container 120 to an inside bottom perimeter of the upper shell module 102. And, fuel supply platform 128 can be secured to the lower shell module 104 by using the plurality of screws 118 to attach an inside perimeter of the lower shell module 104 to an outside perimeter of the fuel supply platform 128. The shell lid 108 can be removably attached to a top end of the upper shell module 102 by screwing the shell lid 108, having female threads around its inside perimeter, to the upper shell module 102, having male threads around its top outside perimeter. The container 120 can be any container that can conduct heat, such as a cup, mug or sauce pan; preferably the container 120 will have a metallic composition. And, the upper and lower shell modules 102 and 104 can be made of a thermally non-conductive material, preferably a polymeric material; alternatively, the container 120 can have a thermally insulating layer disposed between a sidewall 121 of the container 120 and the upper shell module 102.
The components of the catalytic combustion assembly 122 are illustrated in more detail in
The elongate sidewall enclosure 142 preferably should have a diameter that is relatively small in order to ensure that the curved portion of the sidewall enclosure 142 can bend in a smooth and continuous fashion within the coupled chamber plates 124 and 126; and in order to more evenly distribute the heat generated from the catalytic combustion chamber 140 to the top chamber plate 124 and to the bottom of the container 120 that is adjacent to the top chamber plate 124, which, in turn, provides for a more even distribution of heat to the beverage or food. At the same time, however, the elongate sidewall enclosure 142 should have a diameter and length that are large enough to contain a sufficient quantity of a catalytic reaction media 160 over the length of the sidewall enclosure 142 to produce a sufficient amount of heat to effectively the top chamber plate 124, bottom of the container 120 and the beverage or food within container 120. Given these considerations, the inventors have determined that the elongate sidewall enclosure 142 preferably should have a diameter of about 10 millimeters or less, and more preferably between about 5 and 10 millimeters. The elongate sidewall enclosure 142 also has a flow-through fuel gas inlet 142C within one end of the sidewall enclosure 142 and a flow-through exhaust outlet 142D within the other end of the sidewall enclosure 142, with the sidewall enclosure 142 having no other flow-through openings within the sidewall enclosure 142. And, a flow-through fuel gas inlet elbow 150 and a flow-through exhaust outlet elbow 152 are sealably disposed within the flow-through fuel gas inlet 142C and the flow-through exhaust outlet 142D, respectively. The flow-through exhaust outlet elbow 152 also has a tubular connection 153 with the exhaust outlet duct 116 within the lower shell module 104. The tubular connection 153 effectively extends the enclosed length of the elongate sidewall enclosure 142 from the flow-through exhaust outlet 142D of sidewall enclosure 142 to the exhaust outlet duct 116.
It is preferred that the top and bottom chamber plates, 124 and 126, are coupled together by utilizing a plurality of binder posts 154, with top portions of the binder posts 154 disposed within corresponding openings through the top chamber plate 124, with bottom portions of the binder posts 154 disposed within corresponding openings through the bottom chamber plate 126, and with bottom ends of the binder posts 154, which extend away from the bottom surface of the bottom chamber plate 126, used to couple the top chamber plate 124 to the bottom chamber plate 126 by flattening the ends of the binder posts 154 against the bottom surface of the chamber plate 126. Preferably, the top and bottom chamber plates, 124 and 126, have a metallic composition.
Before the enclosed catalytic combustion chamber 140 is formed by coupling the top and bottom chamber plates, 124 and 126, the catalytic reaction media 160 preferably can be positioned in a curved orientation, as shown in
Once the catalytic reaction media 180 and combustion element 164 are positioned within the curved bottom channel 126A and the top chamber plate 124 is coupled to the bottom chamber plate 126, the catalytic reaction media 160 and the combustion element 164 are captured in a curved orientation within the curved sidewall section 142A of the elongate sidewall enclosure 142, thereby defining catalytic combustion chamber 140 as having the same shape as the elongate sidewall enclosure 142. In this regard, a curved elongate shape for the catalytic combustion chamber 140 is preferred in order to more evenly distribute the heat from the combustion chamber 140 to the top chamber plate 124 and, thereby, provide for a more even distribution of heat to the beverage or food within container 120. And, the most preferred curved elongate shape for the catalytic combustion chamber 140 is a curvature having a constant radius of curvature (hereinafter referred to as a “circular curvature”) providing a smooth and continuous surface within the combustion chamber 140. Although the catalytic combustion chamber 140 having a circular curvature is preferred, as described in connection with catalytic heating system 1, other curved shapes, such as serpentine or coiled, can be used with catalytic heating system 100
The fuel supply assembly 130 further comprises the programmed microprocessor 166 that is attached to and in electrical connection to a circuit bord 137 that is mounted on the top side of the fuel supply platform 128. A battery 138, such as a lithium polymer type GM502030 from PowerStream Technology, Inc., can also be attached to and in electrical connection to the circuit board 137, or the battery 138 can be attached to any other appropriate location within the catalytic combustion assembly 122 or within the lower shell module 104 surrounding the catalytic combustion chamber 140. The battery 138 supplies electrical power to the programmed microprocessor 166 when the on/off button 112 is in the “on” position and disconnects electrical power when the on/off button 112 is in the off position. When activated, the programmed microprocessor 166, with inputs from the temperature sensors 129A and 129B, controls the functionality of the solenoid valve 135 in order to control the fuel gas flow rate and temperature within the enclosed catalytic combustion chamber 140. The activated programmed microprocessor 166 also supplies electrical power to the combustion starting element 164, which the microprocessor 166 coordinates with the supply of fuel gas to the enclosed catalytic combustion chamber 140 by opening and dosing the solenoid valve 135.
The cross-sectional side view presented in
The catalytic heating system 100 has general industrial applicability in that it can be utilized to heat a container containing a beverage or food. Specifically, operation of the catalytic heating system 100 can proceed by providing a flow of the dimethyl ether fuel gas 127 by attaching the fuel canister 132, containing the dimethyl ether fuel gas 127 to the fuel supply platform 128, by screwing the fuel flow valve 188 into the platform receptacle 178, which causes the tap within the fuel gas compression fitting 131 to open the fuel flow valve 188 and causes the dimethyl ether fuel gas 127 within the fuel canister 132 to flow through compression fitting 131 and into the fuel supply assembly 130. The dimethyl ether fuel gas 127 will initially flow through the liquid/gas separator 133, where any fuel gas in liquid form will be removed, and then flow through the pressure regulator 134 that will maintain the fuel gas below a predetermined pressure, and continue flowing until it reaches the solenoid valve 135. With the on/off button 112 in the “off” position, the solenoid valve 135 will be closed, which prevents the dimethyl ether fuel gas 127 from flowing into the fuel and air mixing injector 136. Next, the catalytic heating system 100 can be operated to heat a beverage or food by, if necessary, removing the shell lid 108 by unscrewing it from its engagement with the top of the upper shell module 102. A beverage or food can then be placed into the container 120 and the shell lid 108 reattached to the upper shell module 102. The catalytic combustion process that is utilized to heat the beverage or food is initiated by depressing the on/off button 112 to the “on” position, which activates the programmed microprocessor 166 by closing the circuit connection between the battery 138 and programmed microprocessor 166. At a predetermined time after activation, the programmed microprocessor 166 causes the solenoid valve 135 to open, causing the dimethyl ether fuel gas 127 to flow into the fuel and air mixing injector 136. As the dimethyl ether fuel gas 127 flows through the fuel and air mixing injector 136, the velocity of the fuel gas flow 127 will increase due to the distal narrowing of the injector 136. Increasing the velocity of the dimethyl ether fuel gas 127 causes the pressure in the fuel and air mixing injector 136 to decrease, thereby entraining the dimethyl ether fuel gas 127 with atmospheric air in order to produce a dimethyl ether fuel gas and entrained air mixture, while maintaining an entrainment ratio of about 15 or more parts air to about one part dimethyl ether fuel gas 127 for the mixture. The dimethyl ether fuel gas and the entrained air mixture is injected by the fuel and air mixing injector 136 into the flow-through fuel gas inlet elbow 150 and then into the elongate sidewall enclosure 142 defining the catalytic combustion chamber 140, thereby constraining the flow of the mixture though the catalytic combustion chamber 140 to the curved and linear path best illustrated in
The advantages and unexpected results provided by the catalytic heating system 100 are the same as the advantages, and unexpected results of the catalytic heating system 1 described above. However, the catalytic heating system 100 has the additional advantage of being able to remove the upper shell module 102 and its attached container 120 within the upper shell module 102 from the lower shell module 104, providing the conveniences of using and washing the container 120 separate from the lower shell module 104.
In an another embodiment, a catalytic heating system 200 for heating a beverage or food with a stovetop surface 201 is described in
The catalytic combustion assembly 222 can be used in a manner, which is the same as the manner of utilizing the catalytic combustion, assembly 122, to provide a catalytic heating process within the catalytic heating system 200. Specifically, the fuel canister 232 within catalytic combustion assembly 222, entrained air mixture within the enclosed catalytic combustion chamber 240 generates a catalytic combustion process within the catalytic reaction media 260 disposed within the catalytic combustion chamber 240. The heat generated from the catalytic combustion process heats the top chamber plate 224 within the integrated chamber plate 225, just like the catalytic heating system 100 uses the heat generated from the catalytic combustion chamber 140 to heat the top chamber plate 124 within the Integrated chamber plate 125. In this regard, however, the manner in which the two systems are used to heat a container are different. In the catalytic heating system 100, the heated top chamber plate 124 is brought into adjacent contact with the bottom of container 120 by attaching the top module 102 to the bottom module 104, thereby providing for conduction of heat directly from the heated top chamber plate 124 to the container 120. By contrast, in catalytic heating system 200, the heated top chamber plate 224 within integrated chamber plate 225 is utilized as the stovetop surface 201 that can be used to heat a container, like a pot, pan or similar container that can be used to heat its contents by simply placing the container on the stovetop surface 201.
in an another embodiment, a catalytic heating system 300 for heating a beverage or food, with a stovetop surface 301 is described in
The components of the catalytic combustion assembly 322 are illustrated in more detail in
The perspective and exploded view of
The bottom side 328B of bottom chamber plate 326, as show In
The catalytic combustion assembly 322 within catalytic heating system 300 can be used in a manner, which is the same as the manner of utilizing the catalytic combustion assembly 222 within catalytic heating system 200, in order to generate a fuel gas and entrained air mixture to be injected into a combustion chamber Specifically, the fuel canister 332 within catalytic combustion assembly 322, which is releasably connected to the fuel supply assembly 330, supplies fuel gas to the fuel supply assembly 330, which in turn utilizes the fuel and air mixing injector 336 to generate the fuel gas and entrained air mixture There are differences, however, in the manner in which catalytic combustion assembly 322, as compared to catalytic combustion assembly 222, utilizes the fuel gas and entrained air mixture to generate conductive heat from a catalytic combustion process. The catalytic combustion assembly 322 within catalytic heating system 300 uses the fuel and air mixing injector 336 to inject the fuel gas and entrained air mixture through fuel gas tubular connector 370 into the plurality of enclosed catalytic combustion chambers 360, where catalytic combustion processes heat the top chamber plate 324 and stovetop surface 301. By comparison, catalytic combustion assembly 222 within heating system 200, uses fuel and air mixing injector 236 to inject the fuel gas and entrained air mixture through flow-through fuel gas inlet 150 into a single enclosed catalytic combustion chamber 240, where a catalytic combustion process heats the top chamber plate 224 and stovetop surface 201. The plurality of enclosed catalytic combustion chambers 360 is provided, in part, due to the need to generate sufficient heat to heat the stovetop surface 301 which has a larger surface area as compared to the surface area of stovetop surface 201 within catalytic heating system 200. And, the catalytic combustion assembly 322 uses the plurality of exhaust outlets 358 within the chamber plate perimeter wall 326C of the bottom chamber plate 326 to direct exhaust from the plurality of enclosed catalytic combustion chambers 360 to atmosphere, while catalytic combustion assembly 222 within catalytic heating system 200 utilizes a single exhaust outlet 1420 integral with the bottom chamber plate 228 in order to direct exhaust to atmosphere through exhaust outlet duct 216 within outer shell 202. Further, catalytic combustion assembly 322 preferably uses the combustion starting element 374 within the spark ignition system to ignite the fuel gas and entrained air mixture coming from the fuel supply assembly 330 before the mixture reaches the plurality of catalytic reaction media 364, while the catalytic combustion assembly 222 preferably uses a coiled combustion starting element 264C that is embedded in the catalytic reaction media 260 to ignite the fuel gas and entrained air mixture. With the exception of these differences, the description of the use of catalytic combustion assembly 222 within catalytic heating system 200 to generate a catalytic heating process to conductively heat a container, like a pot, pan or similar container by simply placing the container on the stovetop surface 201 as shown in
Although each enclosed catalytic combustion chamber out of the plurality of enclosed catalytic combustion chambers 360 has a preferred elongate curved shape, other shapes can be utilized. For example, the catalytic combustion chamber can be linear or have a combination of linear and a curved sections. In this regard, however, the preferred elongate curved shape of each of the enclosed combustion chambers out of the plurality of enclosed combustion chambers 360 substantially increases the amount of heat energy that the catalytic combustion process within the enclosed catalytic combustion chamber can transfer to the top chamber plate 324 and its integral stovetop surface 301. As the ignited fuel gas and entrained air mixture reacts with the catalytic reaction media 364 disposed with the catalytic combustion chamber and flows through the chamber, centrifugal force generates an asymmetric laminar flow velocity, causing higher temperatures, causing the majority of the heat energy generated from the catalytic combustion process to be produced in a zone much closer to the sidewall surface of the catalytic combustion chamber that is adjacent to the outside convex portion of the catalytic reaction media than would otherwise occur. This action, in turn, causes a more efferent transfer of heat energy to the integrated chamber plate and its integral stovetop surface. In addition, the heat transferred from the catalytic combustion chamber to the top chamber plate can be more uniformly distributed across the top chamber plate by utilizing a material, such as Annealed Pyrolytic Graphite, which has the characteristic of conducting heat preferentially in the plane of the top chamber plate, rather than equally well in all directions, as is more common. By comparison, a similar catalytic combustion process generated in an enclosed combustion chamber having an elongate linear shape would not accelerate the flow of fuel gas and entrained air mixture through the chamber and, as a result, additional heat energy would not be generated.
Another embodiment of the integrated chamber plate 325 within the catalytic combustion assembly 322 is illustrated in
In an another embodiment, a catalytic heating system 400 for heating a beverage or food, with a stovetop surface 401 is described in
The components of the catalytic combustion assembly 422 are illustrated in more detail in
The perspective and exploded view of
The bottom chamber plate 426, as illustrated in
The catalytic combustion assembly 422 within catalytic heating system 400 can be used in a manner, which is the same as the manner of utilizing the catalytic combustion assemblies 222 and 322 within catalytic heating systems 200 and 300, respectively, to generate a fuel gas and entrained air mixture to be injected into a combustion chamber Specifically, the fuel canister 432 within catalytic combustion assembly 422, which Is releasably connected to the fuel supply assembly 430, supplies fuel gas to the fuel supply assembly 430, which in turn utilizes the fuel and air mixing injector 436 to generate the fuel gas and entrained air mixture. However, the manner in which the catalytic heating system 400 utilizes the fuel gas and entrained air mixture to generate conductive heat from a catalytic combustion process has several significant differences from the other two systems. In the catalytic heating system 400, the injected fuel gas and entrained air mixture is injected through the flow-through fuel gas inlet 440 within the center of bottom chamber plate 426, just like in system 300 where the fuel and a if mixture is injected through flow-through fuel gas inlet 356 within the center of bottom chamber plate 326, but before the fuel gas and entrained air mixture reaches the catalytic reaction media 462, the mixture flows through the plurality of curved guide vanes 470. This action causes the fuel gas and entrained air mixture to divide into a corresponding plurality of curved fluid flows and for the curved fluid flows to accelerate The plurality of curved fluid flows then pass through a corresponding plurality of guide vane ring openings 454A through the guide vane 454 ring. And, as the plurality of curved fluid flows exit the corresponding plurality guide vane ring openings 454A, a corresponding plurality of guide vane ring flaps 456 further accelerate the curved fluid flows, thereby creating a circulating flow field concentration fuel gas and entrained air mixture within the catalytic reaction media 462 and generally adjacent to inside concave surface 462A of the catalytic reaction media 462. More specifically, the circulating flow field has both a velocity distribution and a fuel gas and entrained air mixture concentration distribution that is more spatially uniform within in the catalytic reaction media 462 than would otherwise occur without the circulating flow field. At a predetermined time after the formation of the circulating concentration of the fuel gas and entrained air mixture, the microprocessor 466 activates the ignition system, causing combustion starting element 464 to generate heat and ultimately ignite the fuel gas and entrained air mixture that has started circulating inside the catalytic reaction media 462. Because of the circular flow, the ignition process proceeds in a circular pattern around the catalytic reaction media until all of the reaction media is contributing to the catalytic heat production. The heat generated from the catalytic combustion process will be distributed over a greater reaction zone volume within the catalytic reaction media 462, similarly contributing to a more uniform distribution of heat energy across the integrated chamber plate 425 and its integral stovetop surface 401, as well as inhibiting the heat generation reaction zone in the catalytic reaction media 462 from collapsing toward the flow-through fuel gas inlet 440. As the catalytic combustion process proceeds within catalytic combustion chamber 460, heat is transferred to the top chamber plate 424 and to stovetop surface 401, which can be used to heat a container, like a pot, pan or similar container that can be used to heat its contents by simply placing the container on the stovetop surface 401. Exhaust passes through the outside convex surface 4628 of the catalytic reaction media 462 and ultimately passes through the plurality of exhaust outlets 458 through perimeter wall 442 of bottom chamber plate 426 and then to atmosphere. A microprocessor 366 within fuel supply assembly 330 is utilized to control the spark ignition system which generates an electrical spark between the pair of wires forming the combustion starting element 374. And, a temperature sensor 476 can be integral with the bottom side 426B of bottom chamber plate 426 for sensing the temperature of the catalytic combustion process.
The catalytic heating systems described herein embody novel and thermodynamically significant features that are not present in other portable catalytic heating systems. One such feature is that the stovetop heating surface is integral with the integrated chamber plate that contains the enclosed catalytic combustion chamber. As a result heat from the catalytic combustion process within the catalytic combustion chamber is transferred by thermal conduction through the integrated chamber plate to its integral stovetop surface. Similarly, when a container placed on the stovetop surface, heat is transferred from the stovetop surface by thermal conduction to the bottom of the container that is in contact with the stovetop surface Another feature that is provided for in catalytic heating systems 200 and 300 is that the elongate and enclosed catalytic combustion chamber has a single fuel gas opening and a single exhaust opening, with both openings fluidly connected to the catalytic combustion chamber. As a result, almost all of the heat from the catalytic combustion process within the catalytic combustion chamber is transferred to the integrated chamber plate, rather than having a substantial amount of the heat exit the chamber as exhaust. This feature significantly enhances the efficiency of the systems in heating the stovetop surface. Another feature that is characteristic of catalytic heating systems 200 and 300 is that when dimethyl ether is utilized as the preferred fuel gas, the efficiency of the system is further enhanced due to the fact that dimethyl ether, as compared to other fuel gases, has a relatively low stoichiometric air to fuel ratio which provides for the complete combustion of the fuel gas and entrained air mixture within the catalytic combustion chamber. This complete combustion also has an added safety feature in that no uncombusted fuel gas is discharged to atmosphere, where the fuel gas could contaminate the air, further, the preferred shape of the catalytic combustion chamber within in catalytic heating systems 200 and 300 is curved, which further enhances the heating efficiency of the system. As the ignited fuel gas and entrained air mixture reacts with the catalytic reaction media disposed with the catalytic combustion chamber and flows through the chamber, centrifugal force generates an asymmetric laminar flow velocity, causing higher temperatures to be generated from the catalytic combustion process at the outside convex portion of catalytic reaction media. These higher temperatures, in turn, cause a concentration of heat to be transferred to integrated chamber plate and its integral stovetop surface.
In alternate embodiment of the catalytic heating system 300, each of the plurality of catalytic combustion chambers within the integrated chamber plate can have a linear shape, rather than a curved shape. In this embodiment, the flow of the ignited fuel gas and entrained air mixture through the catalytic combustion chambers would not accelerate causing an increase in the concentration of the ignited fuel gas and entrained air mixture in the chamber. However, a comparable effect can be implemented by using the flow diverter attached to the bottom surface of the top chamber plate. As describe in detail above the flow diverter causes the flow of ignited fuel gas and entrained air mixture to remain adjacent to and in contact with to the bottom surface of the top chamber plate, resulting in an increase in the concentration of the ignited fuel gas and entrained air mixture between the catalytic reaction media and the top chamber plate, which gives rise to a concentration of higher temperatures In the catalytic combustion chamber that conductively heats the top chamber plate and its integral stovetop surface.
The catalytic ideating systems described herein embody novel and thermodynamically significant features that are not present in other portable catalytic heating systems. One such feature is that the stovetop heating surface is integral with the integrated chamber plate that contains the enclosed catalytic combustion chamber. As a result heat from the catalytic combustion process within the catalytic combustion chamber is transferred primarily by thermal conduction through the integrated chamber plate to Its integral stovetop surface. Similarly, when a container placed on the stovetop surface, heat is transferred from the stovetop surface by thermal conduction to the bottom of the container that is in contact with the stovetop surface. Another feature that is provided for in catalytic heating systems 200 and 300 is that the elongate and enclosed catalytic combustion chamber has a single fuel gas opening and a single exhaust opening, with both openings fluidly connected to the catalytic combustion chamber. As a result, almost all of the heat from the catalytic combustion process within the catalytic combustion chamber is transferred to the integrated chamber plate, rather than having a substantial amount of the heat exit the chamber as exhaust. This feature significantly enhances the efficiency of the systems in heating the stovetop surface.
Another feature that is characteristic of catalytic heating systems 200 and 300 is that when dimethyl ether is utilized as the preferred fuel gas, the efficiency of the system is further enhanced due to the fact that dimethyl ether, as compared to other fuel gases, has a relatively low stoichiometric air to fuel ratio which provides for the complete combustion of the fuel gas and entrained air mixture within the catalytic combustion chamber. This complete combustion also has an added safety feature in that no uncombusted fuel gas is discharged to atmosphere, where the fuel gas could contaminate the air. Further, the preferred shape of the catalytic combustion chamber within in catalytic heating systems 200 and 300 is curved, which further enhances the heating efficiency of fee system. As the ignited fuel gas and entrained air mixture reacts with the catalytic reaction media disposed with the catalytic combustion chamber and flows through the chamber, centrifugal force generates an asymmetric laminar flow velocity, causing the majority of the heat energy generated from the catalytic combustion process, to be produced in a zone much closer to the sidewall surface of the catalytic combustion chamber that is adjacent to the outside convex portion of the catalytic reaction media than would otherwise occur. This action, in turn, causes a more efficient transfer of heat energy to the integrated chamber plate and its integral stovetop surface.
Although catalytic heating system 400 does not provide for an elongate and enclosed catalytic combustion chamber as in systems 200 and 300, the catalytic heating system 400 does contain novel integrated chamber plate components that provide for enhanced efficiency in heating the stovetop surface. As discussed in more detail above, the fan-like structure and its related components creates a concentrated flow of circulating fuel gas and entrained air mixture as the flow enters the inside concave surface of the catalytic reaction media. This results in a circulating flow field with both a velocity distribution and a fuel gas and entrained air mixture concentration distribution that is more spatially uniform within the catalytic reaction media than would otherwise occur. In turn, the heat generated from the catalytic combustion process will be distributed over a greater reaction zone volume of the catalytic media, similarly contributing to a more uniform distribution of heat energy across the integrated chamber plate and its integral stove top, as well as, inhibiting the heat generating reaction zone in the catalytic media from collapsing toward the flow-through fuel gas inlet.
The catalytic heating systems described herein have general industrial applicability in that they can be utilized to heat a container containing a beverage or food using a stovetop surface.
Although a preferred embodiment and other embodiments have been described, It will be recognized by those skilled in the art that other embodiments and features can be provided without departing from the underlying principles of those embodiments. The scope of the invention is defined by the appended claims.
Claims
1. A catalytic combustion assembly for heating a stovetop surface, comprising:
- a chamber plate having chamber plate top and bottom sides, with a chamber plate perimeter wall disposed between and integral with the chamber plate top and bottom sides, and with the stovetop surface integral with the chamber plate top side;
- a flow-through fuel gas inlet and a flow-through exhaust outlet integral with the chamber plate bottom side;
- an enclosed catalytic combustion chamber integral with the chamber plate, with the enclosed catalytic combustion chamber having at one end a combustion chamber fuel gas opening fluidly connected to the flow-through fuel gas inlet and at another end a combustion chamber exhaust opening fluidly connected to the flow-through exhaust outlet, and with no other openings providing access to the enclosed catalytic combustion chamber;
- a catalytic reaction media disposed within the enclosed catalytic combustion chamber;
- a combustion starting element disposed within the catalytic reaction media;
- a fuel supply assembly mounted on a fuel supply platform, with the fuel supply assembly having a fuel and air mixing injector fluidly connected to the flow-through fuel gas inlet;
- a fuel canister sealably connected to the fuel supply platform for supplying a fuel gas to the fuel supply assembly; and
- whereby the fuel and air mixing injector within the catalytic combustion assembly can entrain the fuel gas with air and inject a fuel gas and entrained air mixture through the flow-through fuel gas Inlet and into the enclosed catalytic combustion chamber, where the combustion starting element can ignite the fuel gas and entrained air mixture and the catalytic reaction media can generate a catalytic combustion process within the enclosed catalytic combustion chamber, with exhaust from the catalytic combustion process flowing through the flow-through exhaust outlet to atmosphere, with the catalytic combustion process transferring heat to the chamber plate top side and integral stovetop surface, and with the stovetop surface for conductively transferring heat to a container.
2. The catalytic combustion assembly of claim 1 in which the fuel gas is selected from the group consisting of dimethyl ether, butane, propane and mixtures thereof.
3. The catalytic combustion assembly of claim 1 in which the fuel gas has a stoichiometric air to fuel ratio of about 15.
4. The catalytic combustion assembly of claim 1 in which the catalytic reaction media comprises a substrate, combined with a catalyst support and an active catalyst.
5. The catalytic combustion assembly of claim 1 in which the catalytic combustion chamber has an elongate cylindrically shape.
6. The catalytic combustion assembly of claim 1 in which the enclosed catalytic combustion chamber has a curved shape.
7. The catalytic combustion assembly of claim 8 in which the curved shape of the enclosed catalytic combustion chamber has a circular curvature.
8. The catalytic heating assembly of claim 1 in which the enclosed catalytic combustion chamber has a partially curved and linear shape.
9. The catalytic heating assembly of claim 5 in which the enclosed catalytic combustion chamber having a cylindrically shape has a diameter of about 10 millimeters or less.
10. The catalytic heating assembly of claim 5 in which the enclosed catalytic combustion chamber having a cylindrically shape has a diameter of between about 5 millimeters and about 10 millimeters.
11. A catalytic combustion assembly for heating a stovetop surface, comprising:
- a chamber plate having chamber plate top and bottom sides, with a chamber plate perimeter wall disposed between and integral with the chamber plate top and bottom sides, and with the stovetop surface integral with the chamber plate top side;
- a flow-through fuel gas inlet integral with the chamber plate bottom side and a flow-through exhaust outlet integral with the chamber plate perimeter wall;
- a plurality of enclosed catalytic combustion chambers integral with the chamber plate. with each enclosed catalytic combustion chamber out of the plurality of enclosed catalytic combustion chambers having at one end a combustion chamber fuel gas opening fluidly connected to the flow-through fuel gas inlet integral with the chamber plate bottom side, and at another end of the enclosed catalytic combustion chamber a combustion chamber exhaust opening fluidly connected to the flow-through exhaust outlet integral with the chamber plate perimeter wall and with no other openings providing access to the enclosed catalytic combustion chamber:
- a plurality of catalytic reaction media disposed within a corresponding plurality of the enclosed catalytic combustion chambers;
- a combustion starting element disposed within the flow-through fuel gas inlet;
- a fuel supply assembly mounted on a fuel supply platform: with the fuel supply assembly having fuel and air mixing injector fluidly connected to the flow-through fuel gas inlet;
- a fuel canister sealably connected to the fuel supply platform for supplying a fuel gas to the fuel supply assembly; and
- whereby the fuel and air mixing injector within the fuel supply assembly can entrain the fuel gas with air and inject a fuel gas and entrained air mixture into the flow-through fuel gas inlet, where the combustion starting element can ignite the fuel gas and entrained air mixture, and ignited fuel gas and entrained air mixture can then flow through the plurality of catalytic reaction media within a corresponding plurality of enclosed catalytic combustion chambers, where the plurality of catalytic reaction media can generate a catalytic combustion process within the corresponding plurality of enclosed catalytic combustion chambers, with the catalytic combustion process transferring heat to the chamber plate top side and integral stovetop surface, and with the stovetop surface for conductively transferring heat to a container.
12. The catalytic heating assembly of claim 11 in which the fuel gas is selected from the group of dimethyl ether, butane, propane and mixtures thereof.
13. The catalytic heating assembly of claim 11 in which the fuel gas has a stoichiometric air to fuel ratio of about 15.
14. The catalytic heating assembly of claim 11 in which the catalytic reaction media comprises a substrate, combined with a catalyst support and an active catalyst.
15. The catalytic combustion assembly of claim 11 in which each enclosed catalytic combustion chamber out of the plurality of enclosed catalytic combustion chambers has an elongate curved shape.
16. The catalytic combustion assembly of claim 15 in which the enclosed catalytic combustion chamber having an elongate curved shape has four elongate sidewall surfaces, with each elongate sidewall surface normal to adjacent sidewall surfaces and opposite from a sidewall surface.
17. The catalytic combustion assembly of claim 16 in which the distance between opposite sidewall surfaces is between about 5 and 10 millimeters.
18. The catalytic combustion assembly of claim 16 in which the distance between opposite sidewall surfaces is about 10 millimeters or less.
19. The catalytic combustion assembly of claim 11 in which each enclosed catalytic combustion chamber out of the plurality of enclosed catalytic combustion chambers has an elongate linear shape.
20. The catalytic combustion assembly of claim 19 in which the enclosed catalytic combustion chamber has an elongate linear shape having four elongate sidewall surfaces, with each elongate sidewall surface normal to adjacent sidewall surfaces and opposite from a sidewall surface.
21. The catalytic combustion assembly of claim 19 in which the top chamber plate top side has an inside surface with a flow diverter integral with the inside surface and positioned at the center of the inside surface.
22. The catalytic combustion assembly of claim 20 in which the distance between opposite sidewall surfaces is between about 5 and 10 millimeters.
23. The catalytic combustion assembly of claim 20 in which the distance between opposite sidewall surfaces is about 10 millimeters or less.
24. A catalytic combustion assembly for heating a stovetop surface, comprising:
- a chamber plate enclosure having a chamber plate top and bottom sides, with a chamber plate perimeter wall disposed between and integral with the chamber plate top and bottom sides, and with the stovetop surface integral with the chamber plate top side;
- a flow-through fuel gas inlet integral with the chamber plate bottom side and a flow-through exhaust outlet integral with the chamber plate perimeter wall;
- a guide vane ring disposed within the chamber plate enclosure, with the guide vane ring having a plurality of guide vane ring openings and a corresponding plurality of guide vane ring flaps, with each guide vane ring flap out of the plurality of guide vane ring flaps integral at one end with the guide vane ring and with an opposite end of the guide vane ring flap extending away from a guide vane ring opening out of the plurality of guide vane ring openings;
- a catalytic combustion chamber within a space within the chamber plate enclosure, with the space defined by the chamber plate perimeter wall, the chamber plate top and bottom sides, and the guide vane ring;
- a catalytic reaction media disposed within the catalytic combustion chamber;
- a plurality of guide vanes disposed within the chamber plate enclosure and positioned between the guide vane ring and the flow-through fuel gas inlet, with each guide vane out of the plurality of guide vanes adjacent at a proximal end to the flow-through fuel gas inlet and integral at a distal end with the guide vane ring, with each distal end of a guide vane out of the plurality of guide varies positioned such that a guide vane opening out of the plurality of guide vane openings is between distal ends of adjacent guide vanes;
- a combustion starting element disposed within the catalytic reaction media;
- a fuel supply assembly mounted on a fuel supply platform, with the fuel supply assembly having a fuel and air mixing injector fluidly connected to the fuel gas inlet;
- fuel canister sealably connected to the fuel supply platform for supplying a fuel gas to the fuel supply assembly; and
- whereby the fuel and air mixing injector within the fuel supply assembly can be used to entrain the fuel gas with air and inject a fuel gas and entrained air mixture through the flow-through fuel gas inlet and cause a flow of the fuel gas and entrained air mixture to pass between the plurality of guide vanes where the flow accelerates; the flow can then pass through the plurality of guide vane ring openings and then flow past the plurality of guide vane flaps, causing the flow to accelerate further; and the flow can then penetrate the catalytic reaction media within the catalytic combustion chamber, where the flow can be ignited by the combustion starting element, generating a catalytic combustion process within the catalytic combustion chamber, with the catalytic combustion process transferring heat to the chamber plate top side and integral stovetop surface, with the stovetop surface for conductively transferring heat to a container.
25. The catalytic combustion assembly of claim 24 in which the fuel gas is selected from the group of dimethyl ether, butane, propane and mixture thereof.
26. The catalytic heating assembly of claim 24 in which the fuel gas has a stoichiometric air to fuel ratio of about 15.
27. The catalytic combustion assembly of claim 24 in which the catalytic reaction media comprises a substrate, combined with a catalyst support and an active catalyst.
26. The catalytic heating assembly of claim 24 in which the catalytic reaction media has a cylindrical ring shape.
29. A method of heating a stovetop surface:
- providing for a flow of a fuel gas, with the fuel gas having a stoichiometric ratio of about 15;
- increasing the velocity of the flow of the fuel gas;
- entraining the flow of the fuel gas with air, thereby creating a flow of fuel gas and entrained air mixture;
- maintaining an entrainment ratio of about 15 or above for the flow of fuel gas and entrained air mixture;
- constraining the flow of fuel gas and entrained air mixture to an enclosed curved path;
- contacting the flow of fuel gas and entrained air mixture with a catalytic reaction media;
- igniting the flow of fuel gas and entrained air mixture, thereby generating the catalytic combustion process;
- combusting all of the fuel gas during the catalytic combustion process; and
- conducting heat from the catalytic combustion process to the stove top.
Type: Application
Filed: Mar 31, 2016
Publication Date: Aug 18, 2016
Inventors: Clifford G Welles (Pleasanton, CA), Noriko Welles (Pleasanton, CA)
Application Number: 15/088,059