Abstract:
An apparatus enhances the efficiency of a combustion heating device such as a fireplace by incorporating an ionic gas propulsion mechanism (e.g., a corona discharge device) to transport ambient air through a heat exchanger. A heat exchanger is configured to warm the ambient air using both heat energy produced by the combustion process and/or by byproducts of the combustion, e.g., exhaust gases. Air scrubber functions collect particulates present in the air including combustion byproducts such as ash and soot. An audio modulator may be used to vary the high voltage applied to electrodes of the corona discharge electrodes to vary air velocity in response to an audio or similar control signal to induce a vibratory motion to the air, i.e., sound, in forms such as music or simulated natural noise, and/or to cancel or attenuate undesirable sounds and noises, such as chimney sounds.

Description:
CLAIM TO PRIORITY 
       [0001]    The present patent application claims benefit of priority to U.S. provisional application Ser. No. 60/862,760, entitled “Fireplace with Electrostatically Assisted Heat Transfer and Method of Assisting Heat Transfer in Combustion Powered Heating Devices”, filed on Oct. 24, 2006 which is incorporated herein in its entirety by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to heat distribution and, in particular, a fireplace heat exchanger including an electrical corona discharge device to enhance heat distribution and provide associated functionalities. 
         [0004]    2. Description of the Related Art 
         [0005]    Fireplaces are designated for both heating dwellings and other structures, for decorative purposes and providing the user with a form of entertainment. At the same time the heated air provided by the fireplace provides the user with physical comfort, it also provides quiet illumination and serves an esthetic function. Unfortunately, a traditional fireplace is not otherwise an efficient means for heating a home or other space. This is because the output product of the fireplace, i.e., the heated or hot air, is actually a mixture of gases and end products of the burned wood, i.e. fly ash, that is exhausted to the outside through the chimney. The result is that the fireplace may take more warm air from the surrounds and exhaust the air to the outside with a net loss of heat to the home, that is, the fireplace may, in some cases, actually cool air in the house rather that heat it. 
         [0006]    To overcome this problem fireplace appliances have been developed that return a portion of the heat from exhaust gases using a hot air return into a room. Such appliances prevent or minimize heat loss and help to recapture heat contained in exhaust gases and other products of combustion back into the room to substantially improve fireplace efficiency. Many of these devices include a form of heat exchanger receiving heat from the combustion site for warming room air. A circulating fan forces room air through the heat exchanger to warm ambient room air with the transferred heat energy. Further details of such devices may be found throughout the art and, for example, in the disclosures of the following issued U.S. patents, each of which is incorporated by reference in its entirety herein: 
         [0000]    
       
         
               
               
             
           
               
                   
               
               
                 Patent No. 
                 Title 
               
               
                   
               
             
             
               
                 4,675,029 
                 Apparatus and method for treating the emission products of a wood 
               
               
                   
                 burning stove 
               
               
                 5,610,366 
                 High performance thermoelectric materials and methods of preparation 
               
               
                 5,702,244 
                 Apparatus and method for reducing particulate emissions from 
               
               
                   
                 combustion processes 
               
               
                 5,747,728 
                 Advanced thermoelectric materials with enhanced crystal lattice 
               
               
                   
                 structure and methods of preparation 
               
               
                 5,769,155 
                 Electrohydrodynamic enhancement of heat transfer 
               
               
                 5,769,943 
                 Semiconductor apparatus utilizing gradient freeze and liquid-solid 
               
               
                   
                 techniques 
               
               
                 6,037,536 
                 TPV fireplace insert or TPV indoor heating stove 
               
               
                 6,047,695 
                 Fireplace heat exchanger 
               
               
                 6,145,502 
                 Dual mode of operation fireplaces for operation in vented or unvented 
               
               
                   
                 mode 
               
               
                 6,227,194 
                 Fireplace 
               
               
                 6,237,587 
                 Woodburning fireplace exhaust catalytic cleaner 
               
               
                 6,527,548 
                 Self powered electric generating space heater 
               
               
                 6,543,698 
                 Fireplace make-up air heat exchange system 
               
               
                 6,550,687 
                 Heat exchange system 
               
               
                 6,588,419 
                 Fireplace insert thermally generating electrical power useful for 
               
               
                   
                 operating a circulating fan 
               
               
                 6,648,750 
                 Ventilation assemblies 
               
               
                 6,666,206 
                 Fireplace insert 
               
               
                 6,729,551 
                 Fireplace make-up air heat exchange system 
               
               
                 6,736,133 
                 Air filtration and sterilization system for a fireplace 
               
               
                 6,742,516 
                 Ventilation system and method 
               
               
                 6,755,138 
                 Ventilation system and method 
               
               
                 6,766,798 
                 Supplemental air directing extension frame for a fireplace 
               
               
                 6,886,626 
                 Chimney heat exchange system 
               
               
                 6,908,039 
                 Heat exchange system 
               
               
                 6,948,454 
                 Airflow apparatus 
               
               
                 7,168,427 
                 Air filtration and sterilization system for a fireplace 
               
               
                 7,182,805 
                 Corona-discharge air mover and purifier for packaged terminal and 
               
               
                   
                 room air conditioners 
               
               
                   
               
             
          
         
       
     
         [0007]    U.S. patent application Ser. No. 11/288,620 filed Nov. 29, 2005 entitled “Corona-discharge air mover and purifier for fireplace and hearth”, U.S. Patent Application Publication No. 20060112955, of Debra Reaves (incorporated herein by reference in its entirety) refers to Applicant&#39;s prior patents directed to electrostatic fluid acceleration. The Reaves device uses techniques described by Applicant for moving air through a fireplace passage. This application, however, does not teach details of how to use this technology for air movement in such an environment. 
         [0008]    One such device that is particularly applicable to the background art of the present invention is shown in  FIG. 1  as disclosed by Buezis et al. in U.S. Pat. No. 6,588,419 (incorporated herein by reference in its entirety). As depicted and described therein, an auxiliary or additional fan is installed in an air duct that surrounds a fireplace box. An air intake as well as air outlet are both open to the room. Cold air is sucked or drawn into the inlet, accelerated though the U-shaped duct around the fireplace box, heated, and resulting hot air is discharged back into the room through the outlet. 
         [0009]    While the device of Buezis recaptures heat otherwise lost in the exhaust gas and combustion byproducts, it has at least three drawbacks. First, the ambient air may not flow directly from the inlet to the outlet. Instead, some air circulates within the duct, e.g., returns to a fan located at the input of the duct after being heated at an upper portion of the duct. As a result, only a small portion of the hot air reaches the room. A second drawback is noise generation created by operation of the electric fan motor and blades, resulting in acoustic noise that may be disruptive to the comfort of the occupants and detract from the esthetic nature and appeal for which the fireplace is designated. Third, the fan moves air while it is highly desirable to clean air at the same time from the combustion by-products like fly ash, soot and dust from other sources. The combustion process produces ashes of from the burned wood that are dusty, with fine particles left to drift throughout the room during operation and, in particular, during maintenance such as removal of ashes and other solid combustion byproducts. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0010]    Embodiments of the invention further address the above detailed and other deficiencies of the prior art. For example, a deficiency of fireplace heat exchangers according to the prior art is the failure to provide air cleaning or disinfection. Another deficiency is the failure of prior art devices to incorporate additional entertainment features such as music, sound effects, or soothing sounds and/or reduce sound produces by the burning wood or outside wind whistling in the chimney. 
         [0011]    Thus, the present invention is directed to an apparatus and method for enhancing the efficiency of a combustion heating device, incorporating an ionic gas propulsion mechanism, such as a corona discharge device, to transport ambient air through a heat exchanger. The heat exchanger is configured to warm the ambient air using both heat energy produced by the combustion process and/or by byproducts of the combustion, e.g., exhaust gases. Embodiments of the invention further include air scrubber functions for collecting particulates present in the air including combustion byproducts such as ash and soot. Further embodiments include audio modulation of the air to produce sound, such as music or simulated natural noise, and/or cancel or attenuate undesirable sounds and noises, such as chimney sounds. 
         [0012]    The present invention includes embodiments in the form of a device for efficiently heating a room using a wood or similar fireplace. The device may be placed within a fireplace duct surrounding or transiting a firebox or firepot and/or portions of a chimney flue. The device may further include an airflow path having an inlet for receiving room air and an outlet to return the (warmed or heated) air to the room. A duct connecting the inlet and outlet may surround the firebox from behind and otherwise be positioned to transfer heat energy from the fireplace and/or combustion byproducts to the room air contained within the duct. The inlet, outlet and duct collectively define or form an airflow path. 
         [0013]    An Electrostatic Fluid Accelerator (EFA) may be mounted within the airflow path to force room air through the airflow path from the inlet to the outlet and through the duct. A Power Supply may be mounted and connected to the EFA. The EFA is located in the hot air flow while a High Voltage Power Supply (HVPS) is preferably located in comparatively cool area suitable for operation of the electronic circuitry. High voltage cable (or wire) may be used to connect the EFA to the HVPS. This cable may be located in a special conduit made of an insulating sleeve material. The sleeve or conduit may run along the side of the fireplace from HVPS to EFA to provide a protective path for the cable. 
         [0014]    The EFA may typically include at least two electrodes. One of the electrodes is a corona electrode, preferably in the form of a sharp needle, or small diameter wire, or blades with sharp edges. The other electrode is a collecting electrode, preferably in the form of a larger diameter rod or other geometry that provides a larger size electrode than that of the corona electrode. Respective groups of each of the electrodes (e.g., an array of corona electrodes and an array of collecting electrodes) are located parallel to each other, space at a distance of from several millimeters to several inches but preferably between ½ and 4″. 
         [0015]    The HVPS generates and supplies a high voltage difference between these electrodes that typically ranges between 8 and 40 kV, sometimes even higher. When this voltage difference exceeds a so called corona onset voltage, a corona discharge takes place in a region surrounding and extending a short distance from the corona electrode or its sharp edge. The corona discharge causes an emission of air ions from the corona electrodes that are attracted to the collecting electrode by the electrostatic force existing between the electrodes due to the potential difference. While transiting from one electrode to the other the ions collide with neutrally charged ambient air molecules that are thereby accelerated toward the collecting electrode creating what is sometimes called termed an ionic wind. 
         [0016]    Aspects of the invention further address certain unwanted byproducts of both the ionic wind generation process and caused by the combustion of certain fuels such as wood. For example, in addition to accelerating and moving air, corona discharge produces by-products, most noticeably ozone, a potential health hazard in high concentrations and prolonged exposures. The excessive production of ozone may limit ionic wind application to some extent. 
         [0017]    One aspect of embodiments of the invention is based on ozone (O 3 ) being a relatively unstable gas that, under proper conditions, easily converts to diatomic oxygen (O 2 ). The rate of conversion depends on many factors among which air temperature is predominant. Accordingly, embodiments of the invention effectively incorporate an EFA device in applications involving heated and hot air or other gases and/or fluids wherein the inherent degradation of ozone back to atomic oxygen and diatomic oxygen is supported and/or enhanced by a high temperature environment so as to reduce or eliminate any risk of ozone exposure. Embodiments of the current invention implement this natural method to enhance ozone decay to efficiently and silently move hot air into the house. Aspects of the invention accomplish this by propelling and transporting air through the duct while maintaining an ozonated portion of the air in a hot area of the duct for some appropriate time period that may be greater than the normal dwell or latency period of the ozonated air absent structure and/or methods to increase ozone degradation. 
         [0018]    The time for degradation of ozone back to diatomic or molecular oxygen necessarily depends on the temperature to which the ozone is heated. That is, the higher the temperature used the shorter the time period required for complete ozone to oxygen conversion. For instance, at temperature higher than 250° C. this time is about 0.1 of second. In contrast, at a temperature of about 200° C., the time required for ozone to convert to oxygen is about 1 second. 
         [0019]    Another important factor for efficient ozone to oxygen conversion is that all, i.e., the entire volume, of ozonated air (i.e., air that passed through the corona discharge area) should pass through the hot area for considerable time. Therefore, the duct and EFA itself should be designed in the way to prevent or minimize air bypass via cooler areas that do not provide sufficient temperature to reconvert the ozone back to oxygen. 
         [0020]    The invention further contemplates various placements and numbers of EFA devices within and external to the duct. For example, the EFA may be located at the inlet of the duct that surrounds the fireplace box or “firebox”. Another location for the EFA is close to or within the outlet of the duct. Both locations have their advantages. For example, if the EFA is located at or adjacent the inlet then airflow at the outlet end of the duct may be reduced such that the ozonated air spends more time in the hot area and may be converted to oxygen at lower temperature. However, this EFA location makes it more challenging to push air through length of the duct since the accelerated air may be reflected from the duct and return back to the EFA. 
         [0021]    If, for example, the EFA is instead located at the outlet of the duct so that airflow through the duct is increased, then a higher temperature is needed for ozone conversion, while more air is moved via the duct since the EFA will “pull” rather than “push” the air. This location is preferable but it requires additional design features to place the EFA, not at the very outlet of the duct but, in a “dip” or recess it several inches inside the duct in order to allow ozonated air to spend sufficient time in this smaller recess portion of only those several inches. 
         [0022]    Design consideration of various embodiments of the invention incorporate an increased spacing distance between the corona electrodes (i.e. corona wires) and the opposite (termed collecting) electrodes. A significant source of ozone and area in which ozone is generated is from and within the plasma region immediately surrounding the corona wire or the corona ion emitting sharp edges. The distance between the corona electrodes and the collecting electrodes defines two important factors providing for the minimization of ozone production. First, when a large spacing distance is implemented, and equivalent air flow (i.e., volume and rate) may be generated using a increased voltage and decreased current, i.e. since airflow is proportional to the electrical power used to generate the corona discharge, an equivalent airflow is produced. However, ozone generation rate is directly proportional to the corona current. Thus, the reduced corona current results in reduced ozone is generation. At the same time, the increase spacing distance between the corona electrode and the collecting electrode provides additional time for the ozone to disintegrate or dissociate. 
         [0023]    Another design consideration is a number (or proximity to each other) of the corona wires implemented. If the corona wires are located close to each other they “shadow” the electric field and thus decrease the electric field strength to the wires that are surrounded with the wires on both sides. Due to this physical phenomenon the inner wires emit less corona current that the outmost wires. To prevent this unevenness the corona wires may be located, not one per the collecting electrode but, wider, usually—one corona electrode (wire) per two collecting electrodes. Any other spacing between the corona wires wider than the distance between the collecting electrodes is also beneficial. 
         [0024]    Outermost (corona) wires preferably should not emit any current to the conductive walls of the fireplace duct. Therefore, these walls should be covered with insulating material having low polarization. This insulating material should be located from the outermost wires substantially at the distance approximating one half of the distance between the (corona) wires themselves. 
         [0025]    Another design consideration incorporated into various embodiments of the invention address shock hazards and providing protection from the high operating voltages used by the EFA and its arrays of corona and collecting electrodes. Thus, it may be important to keep the electrodes that are closer to the room interior at some safe electrical potential, preferably at the ground potential, in order to prevent a potential electrical shock hazard through accidental contact with living creatures such as humans and pets. In embodiments wherein the EFA is installed at the inlet of the duct, the closest element to the inlet is the corona electrode or array of corona electrodes. In such case to avoid any shock hazard the corona electrode is preferably maintained at some ground potential while the collecting electrode (or array of collecting electrodes) should be energized to and maintained at some high electric potential. Preferably the collecting electrode is maintained at some negative potential relative to the corona discharge electrode such that, with the corona electrode maintained at ground potential, the collecting electrode is energized with a negative high voltage. The preference of polarities is due to the fact that positive corona discharge emits much less ozone that negative corona discharge. 
         [0026]    In a configuration wherein the EFA is located at the outlet of the duct, the collecting electrode should be maintained at or close to ground potential to eliminate or reduce any shock hazard from the outwardly facing electrodes. In this case, the internally located corona electrodes are energized with a positive high voltage so as to generate and produce a positive corona discharge. 
         [0027]    In order to clean the air, i.e., reduce or eliminate airborne contaminants including combustion byproducts, dust, pollen, spores, airborne pathogens and germs, etc., in air recirculated and delivered back into the room (house) it is preferable to add one or more sets of the electrodes to the EFA structure, so called repelling electrodes. This technique is further detailed and described in Applicants US Patent Application Publication No. 20050150384, now U.S. Pat. No. 7,150,780 issued Dec. 19, 2006, entitled “Electrostatic air cleaning device” and incorporated herein in its entirety by reference. In such a three-electrode configuration at least three cables should go to the EFA from the PS via a special conduit or HV sleeves preventing HV cables from shorting to each other or to the conductive metal portions of the fireplace. 
         [0028]    Further embodiments provide additional features directed to reducing device and ambient noise and/or providing desirable audio while providing heated air comfort with the silent and efficient delivery of hot air in to the room. One such feature incorporates voltage modulation across the EFA electrodes in response to an audio signal so as to create acoustic sound. When voltage modulates with frequencies between 20 Hz and 20,000 Hz the air acceleration through EFA also accelerates with corresponding frequencies and creates corresponding sound effects. This way music, soothing sounds, or other sonic or even subsonic and supersonic audio may be generated to thereby add one more benefit to the hot air delivery and air cleaning. Further details are provided in Applicant&#39;s U.S. Patent Application Ser. Nos. 60/794,510, filed Apr. 25, 2006 and 11/740,264 and 11/740,266, both filed Apr. 25, 2007, all entitled “Electrostatic Loudspeaker”, and PCT/US07/67434 filed Apr. 25, 2007 and entitled “Electrostatic Loudspeaker and Method of Acoustic Waves Generation”, each of which is incorporated herein by reference in its entirety. 
         [0029]    Another feature of embodiments of the present invention addresses an electrode corrosion and contamination that may occur over time. That is, the electrodes of an EFA are naturally contaminated from time to time depending on the amount, type and density of air contaminants present. Embodiments of the invention may incorporate one or both of two methods of electrode cleaning. 
         [0030]    According one method and configuration, both the electrodes and substrates supporting the electrodes are made of washable materials that can withstand cleaning using available appliances such as home and industrial dish washers without sustaining any damage. This substrate may be designed in the way to prevent water accumulation in cavities and holes and/or to provide water drainage and removal so as to allow water to drip freely. A combination of waterproofing and drainage paths allows the substrate to dry completely in a short time. 
         [0031]    According to another cleaning configuration and method, the electrodes and/or the substrate are constructed of inexpensive materials and are engineered to be readily and easily fabricated. In addition to use of inexpensive materials, minimum weight of materials facilitates distribution and replacement such that dirty and/or contaminated electrodes and/or electrode arrays may be easily and cost effectively replaced with new electrodes. 
         [0032]    It should be noted that the geometry, materials, circuit diagrams used for this invention implementation are previously disclosed in various Kronos Advanced Technologies patents and patent application of Igor Krichtafovitch et al. 
         [0033]    The additional features may be also included in a the current invention such as use of a thermostat to control the EFA so that it operates to blow hot air not cold. Other embodiments may regulate a “speed” of the EFA in response to air temperature (inside the duct and/or the room to be heated), such that the higher the air temperature, the greater the EFA speed so that a constant output air temperature is maintained. A thermostat may be located in the room (e.g., an IR sensor may be located in the device that reads a remote temperature within the room) so that the EFA operates to maintain a desired room temperature. If the room gets too hot, then the extra heat may be permitted to go up the chimney, else, recirculated into the room. Another embodiment detects some quality of the air to determine if it is best to recirculate or exhaust outside. For example, if the ozone level is increasing within the room, the EFA decreases air flow and allow the “bad” air to get sucked out through the chimney until the ozone level drops to some acceptable level, and then starts/recommences recirculating of the heated air. Other criteria might also be considered such as odors, dust, etc., that might dictate whether air is recirculated or ventilated. 
         [0034]    According to an aspect of the invention, a heat exchanger includes a duct for transporting a gas from an inlet to an outlet of the duct, the gas within the such in thermal communication with a heat source external to the duct; and an electrostatic discharge device within the duct for accelerating the gas through the duct from the inlet to the outlet. 
         [0035]    According to an aspect of the invention, the electrostatic discharge device may include a high voltage power supply; at least one corona electrode connected to the high voltage power supply; and a collector electrode located proximate the corona electrode and connected to the high voltage power supply so as to induce a motion of the gas in a direction from the corona electrode toward the collector electrode. 
         [0036]    According to another aspect of the invention, the corona electrode may be a wire-like conductive member; and the collector electrode may be a conductive member with the smallest dimension at least 10 times greater than the corona wire diameter. The corona electrode (wire) and the collecting electrodes may be substantially parallel to each other. 
         [0037]    According to another aspect of the invention, the electrostatic discharge device may include at least one repelling electrode. 
         [0038]    According to another aspect of the invention, the high voltage power supply may be connected to the corona electrode with positive voltage potential with respect to the collecting electrode. 
         [0039]    According to another aspect of the invention, the high voltage power supply may be connected to the repelling electrode with a positive voltage potential with respect to the collecting electrode. 
         [0040]    According to another aspect of the invention, the duct is in direct thermal contact with a firebox of a fireplace so as to transmit heat energy from the firebox to the gas within the duct. 
         [0041]    According to another aspect of the invention, the electrostatic discharge device may include a modulator connected to vary an output from the high voltage power supply so as to control the acceleration of the gas in response to an audio signal. 
         [0042]    According to another aspect of the invention, the electrostatic discharge device may include a plurality of the corona electrodes and a plurality of the collector electrodes and wherein a number of the corona electrodes is equal to a number of the collector electrodes plus-minus one. (Nw=Nc+1) 
         [0043]    According to another aspect of the invention, the electrostatic discharge device may include a plurality of the corona electrodes and a plurality of the collector electrodes and wherein a number of the corona electrodes is equal to the number of the collector electrodes divided by two plus-minus one. (Nw=Nc/2+1) 
         [0044]    According to another aspect of the invention, the distance from the corona wire to the collecting electrode is more twice of a distance between the collecting members. 
         [0045]    According to another aspect of the invention, walls of the duct that are immediately proximate to an outermost corona wire are covered with an electrically insulating material. 
         [0046]    According to another aspect of the invention, the insulating material has a low polarization property. 
         [0047]    According to another aspect of the invention, the electrostatic discharge device may include a plurality of the corona electrodes wherein a distance from an outermost of the corona electrodes to a wall of the duct is approximately ½ of a distance between the corona electrodes. 
         [0048]    According to another aspect of the invention, ones of the electrodes closest to a duct opening are maintained at an electrical potential close to the ground potential. 
         [0049]    According to another aspect of the invention, the heat exchanger may further include a substrate supporting the corona and collector electrodes, wherein the corona and collector electrodes a devoid of any cavities capable of retaining any appreciable quantity of water or other liquid. 
         [0050]    According to another aspect of the invention, the corona and collector electrodes and the substrate are made of inexpensive materials such as thin sheets and/or plastic and are easily removable from the duct. 
         [0051]    According to another feature of the invention, a method of heating a space includes the steps of conducting heat from a heat source to a duct; conducting heat from the duct to a gas; and electrostatically accelerating the gas into a space to be heated. 
         [0052]    Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the accompanying drawings or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0053]    The drawing figures depict preferred embodiments of the present invention by way of example, not by way of limitations. In the figures, like reference numerals refer to the same or similar elements. 
           [0054]      FIG. 1  is a fireplace heat distribution device according to the prior art; 
           [0055]      FIG. 2  is a schematic diagram of a heat distribution device according to an embodiment of the invention; 
           [0056]      FIG. 3  is a schematic diagram of a heat distribution device according to another embodiment of the invention; 
           [0057]      FIG. 4   a  is a schematic drawing of the EFA electrodes geometry and mutual location; 
           [0058]      FIG. 4   b  is a schematic drawing of the EFA electrodes geometry and mutual location according to a preferred embodiment of the invention; and 
           [0059]      FIG. 5  is a schematic sectional view of EFA electrodes positioned with an air duct with associated electronics connected to power the array; and 
           [0060]      FIG. 6  is a diagram depicting relative dimensions of corona and collecting electrodes. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0061]      FIG. 1  is a fireplace heat distribution device according to the prior art. The fireplace consists of a combustion chamber  15  in which a gas burner  24  is located. When working flame  25  heats the air in the chamber and thus heats surrounding it duct  33  with air passages  31  and  30 . To move hot air through the duct and discharge worm air into the room fans  36  or  49  may be installed into the dust. Fins  47  are installed within the air passage to enhance heat exchange from the duct metal body to the passing air. 
         [0062]      FIG. 2  is a schematic diagram of an embodiment of the invention including the fireplace  201  with the air duct  204  surrounding the sides and back of a firebox  203 . Preferably, the firebox  203  is made of a thermally conductive material such as steel such that heat is readily transferred from the fireplace to the air duct  204  and thereby into the air within the duct. Other materials may also be used so as to enhance heat transfer by various means including conduction and radiation. For example, a plurality of fins may be included within the firebox and/or within the duct so as to provide additional surface area actively transferring heat energy. Other means may also be used to enhance and facilitate the capture and recovery of heat energy that might otherwise be lost such as a liquid radiator element located above the firebox in the chimney or flue area, etc. Insulation may be provided to both avoid or minimize heat loss to the surrounds and protect the EFA ( 206 —corona electrode and  207 —collecting electrode) and, in particular, the electronics  205  including the high voltage power supply (HVPS) and control circuitry. Such control circuitry may include means for controlling an operation of the EFA, e.g., operate the EFA capacity (i.e. to control voltage across the corona  207  and collecting  206  electrodes) in response to a thermostat to circulate air only when air temperature within the duct has reached some minimum operating temperature. The control circuitry may further support and include enhanced functionality for modulating the airflow as it exits back into the room. For example, the air may be modulated to generate audible audio sounds of music, some ambient nose or background sounds, or even cancel or minimize undesirable noises and/or sounds (e.g., wind, etc.). Cancellation of certain sounds may necessitate use of some type of sound detector such as a microphone to sense the sound and provide a cancellation signal. 
         [0063]    The embodiment of  FIG. 2  includes and EFA device in the intake or inlet of the duct  204 . In this case, airflow through the duct is fastest and the inlet and slows as it proceeds toward the outlet. Thus, the heated air toward the outlet has a larger dwell time in the duct so that ozone reduction is enhanced. The embodiment of  FIG. 3  instead locates the EFA electrode array ( 307 —corona and  306  collecting) at the outlet of the duct  304 , while optionally maintaining the electronics  305 , such as the HVPS, at the cooler inlet end. This configuration has the advantage of providing an increased airflow rate. However, the higher temperature air located near the outlet has a reduced dwell time in the duct  304  as it is rapidly expelled out of the duct and into the room by the EFA electrode array ( 307  and  306 ). 
         [0064]      FIGS. 4   a  and  4   b  are schematic drawings of the EFA electrodes geometries and mutual location/relative positioning. In  FIG. 4   a  a first arrangement of corona, collecting and repelling electrode geometry is shown. Therein, EFA  410  includes corona electrodes  411 , collecting electrodes  412  and the repelling electrodes  413 . Each corona electrode  411  is located between pairs of collecting electrodes  412  and, preferably, in front of the repelling electrode  413 . The distance between the corona electrodes and the collecting electrodes is such that the three lines connecting the corona electrode (in cross section) to the edges of the collecting electrodes create approximately equilateral triangle  420 . That is, the distance between the corona electrodes  411  is approximately equal to the distance between collecting electrodes  412 . Therefore the number of the corona electrodes  411  is equal to the number of the collecting electrodes “plus-minus” one. Such a relation is kind of a “golden rule” in the art of EFA to which all the design guides essentially follow. 
         [0065]      FIG. 4   b  is a schematic drawing of an EFA electrodes geometry and mutual location according to an embodiment of the invention. The EFA  414  comprises corona electrodes  415 , collecting electrodes  416  and the repelling electrodes  417 . Each corona electrode  415  is located in front of (i.e., to the left of as depicted in  FIG. 4   b ) and between the extended planes containing collecting electrodes  416  and, preferably, in front of (i.e., to the left of in  FIG. 4   b ) repelling electrodes  417 . The distance d 1  between the corona electrodes  415  and the collecting electrodes  416  is such that it exceeds double a distance d 2  between the collecting electrodes  416  (i.e., at least double an inter-collecting electrode distance). In a preferred geometry this distance is more than four times greater than the distance between the collecting electrodes, i.e., d 1 &gt;4×d 2 . For example, with a spacing between collecting electrodes of approximately 10 mm (d 2 =10 mm), a corona electrode to collector electrode spacing distance should be at least 40 mm (d 1 ≧40 mm). At such distance the number of the corona electrodes may be greatly reduced. In a preferred geometry every other corona wire is removed or otherwise eliminated (physically or electrically). Thus, according to an embodiment of the invention, the number of the corona electrodes should be equal to the number of the collecting electrodes divided by 2 “plus-minus” one. That is, for a number of corona electrodes N w  and collecting electrodes N c : 
         [0000]        N   w   =N   c /2±1. 
         [0066]      FIG. 5  is a diagram of an embodiment of the invention wherein the electrostatic accelerator electrodes are mounted within a portion of a duct. Referring to  FIG. 5 , an array of electrostatic accelerator electrodes including corona electrodes  415 , collecting electrodes  416  and (optionally) repelling electrodes  417  are located/mounted within a section of duct  521  (shown in cross-section). Electrical insulation  522  may be positioned proximate the outermost corona electrodes  415  so as to cover nearby portions of the duct walls. Insulation  522  may have a low polarization property. Preferably, those electrodes adjacent to any human-accessible openings (e.g., an intake port or exhaust portion of the duct) are maintained at a safe ground potential. For example, if the electrostatic accelerator electrode array of  FIG. 5  were located nearest an intake vent so that corona electrodes  415  might be accessible, then it would be preferable to maintain those electrodes at or near ground potential, i.e., connect HVPS  521  with the positive voltage at ground. Conversely, if positioned at an exhaust portion of the duct so that collecting electrodes  416  and/or repelling electrodes  417  might pose a shock hazard, those electrodes would be maintained at or near ground potential with corona electrodes  415 , mounted further back within the duct, powered with a positive high voltage above ground potential. 
         [0067]    A distance d 3  from the outermost corona electrodes  415  to adjacent walls of duct  521  is approximately one-half (½) a distance d w  between adjacent corona wires  415 . Electronics  523  includes a high voltage power supply (HVPS)  524  for supplying a suitable high voltage to the electrostatic accelerator electrode array via suitable wiring. A modulator  525  may be included to vary the power supplied to the electrostatic accelerator electrode array to produce a modulated airflow. The modulated airflow may produce a desired sound, be used to cancel undesirable noises, vibrations, etc. 
         [0068]      FIG. 6  depicts another feature of an embodiment of the invention wherein corona electrode  415  is made of a wire or wire-like conductive member having a diameter d corona . Collector electrode should preferably have a smallest dimension h collector  (in the illustrated case, the minimum dimension being the thickness or height of the elongated collector electrode) such that: 
         [0000]        h   collector ≧10 ×d   corona.    
         [0069]    It should be understood that other numbers of the corona wires may be selected once the great distance between the corona and the collecting electrodes is chosen. 
         [0070]    While the foregoing has described what are considered to be the best mode and/or other preferred embodiments of the invention, it is understood that various modifications may be made therein and that the invention may be implemented in various forms and embodiments, and that it may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all modifications and variations that fall within the true scope of the inventive concepts. 
         [0071]    It should further be noted and understood that all publications, patents and patent applications mentioned in this specification are indicative of the level of skill in the art to which the invention pertains. All publications, patents and patent applications are herein incorporated by reference to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety.