Abstract:
A water heater includes a water tank adapted to contain water; a flue extending through the water tank and having a first end communicating with the water heater&#39;s combustion chamber for the flow of products of combustion through the tank; a damper communicating with the flue; and an apparatus for creating a flow of air proximate the second end of the flue to resist the flow of warm air out of the second end of the flue due to standby convection. The apparatus for creating airflow may be a fan or an ionic wind generator. Additionally, the airflow may be directed into or across the end of the flue at the top of the water heater to either create a downdraft or an air curtain for containing warm air within the flue.

Description:
BACKGROUND  
         [0001]    The invention relates to a damper arrangement in a water heater. More specifically, the invention relates to a damper arrangement that uses an airflow apparatus to substantially reduce standby heat loss due to natural convection cycles in a water heater flue. It is known to use a damper in a water heater flue. Known dampers use a physical obstruction to close the flue during standby. One example of a physical obstruction type damper is disclosed in U.S. Pat. No. 4,953,510.  
         SUMMARY  
         [0002]    The invention provides a water heater comprising a water tank adapted to contain water, a combustion chamber beneath the water tank, a burner within the combustion chamber and operable to create products of combustion, and a flue extending substantially vertically through the water tank. The flue communicates with the combustion chamber to conduct the products of combustion from the combustion chamber and to transfer heat to water stored within the water tank. The water heater also includes an airflow apparatus capable of creating airflow in the absence of any opposition to the airflow. The airflow apparatus communicates with the flue and resists standby convection flow of flue gases out of the flue when the burner is not operating.  
           [0003]    The airflow apparatus may include a fan or an ionic wind device. The airflow apparatus may be oriented to create a downdraft within the flue or an air curtain across the top of the flue. The downdraft creates a downwardly-directed pressure within the flue that countervails upwardly-directed pressure created by standby convection cycles in the flue. The air curtain creates a flow of air across the top of the flue, which flow of air resists the flow of flue gases out of the flue when the water heater is in standby mode.  
           [0004]    The ionic wind device includes one or more first electrodes that are preferably over the top end of the flue. A second electrode, which may be a portion of the flue itself, is spaced from the first electrodes. A power supply is interconnected between the first electrodes and the second electrode to create a voltage difference therebetween. The first electrodes ionize the air, and the second electrode attracts the ions. The ions are therefore biased for movement toward the second electrode. In the absence of an opposition to such movement of the ions, a flow of air is created by the ions as they move from the first electrodes to the second electrode. When there are flue gases present in the flue, the ions bump into flue gas particles and resist the upward movement of the flue gases out of the flue.  
           [0005]    Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a side elevation view of a water heater embodying the present invention.  
         [0007]    [0007]FIG. 2 is a perspective view of the damper portion of the water heater.  
         [0008]    [0008]FIG. 3 is a cross-sectional view taken along line  3 - 3  in FIG. 2.  
         [0009]    [0009]FIG. 4 is a perspective view of a second damper construction.  
         [0010]    [0010]FIG. 5 is a cross-sectional view taken along line  5 - 5  in FIG. 4.  
         [0011]    [0011]FIG. 6 is a cross-sectional view of a third damper construction.  
         [0012]    [0012]FIG. 7 is a cross-sectional view taken along line  7 - 7  in FIG. 6.  
         [0013]    [0013]FIG. 8 is a partial section view of a fourth damper construction.  
         [0014]    [0014]FIG. 9 is a perspective view of the electrodes of the fourth damper construction. 
     
    
       [0015]    Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of “consisting of” and variations thereof herein is meant to encompass only the items listed thereafter. The use of letters to identify elements of a method or process is simply for identification and is not meant to indicate that the elements should be performed in a particular order.  
       DETAILED DESCRIPTION  
       [0016]    [0016]FIG. 1 illustrates a water heater  10  embodying the invention. The water heater  10  comprises a tank  14  for containing water to be heated, an outer jacket  18  surrounding the water tank  14 , insulation  20  between the tank  14  and the jacket  18 , a combustion chamber  22  below the tank  14 , a flue  26  extending substantially vertically through the water tank  14 , and a baffle  28  extending through the flue  26 . The flue  26  includes a first or lower end  30 , and a second or upper end  38 . The water heater  10  also includes a thermostat  40  extending into the water tank  14  and a burner  42  in the combustion chamber  22 . Fuel is supplied to the burner  42  through a fuel line  43 , a gas valve  44 , and a gas manifold tube  45 . The fuel line  43  also provides fuel to a pilot burner  46  next to the burner  42 . The pilot burner  46  ignites fuel flowing out of the burner  42  when the burner  42  is activated. The pilot burner  46  may be continuous such as a small flame or intermittent such as an electric spark igniter.  
         [0017]    In operation, the burner  42  burns the fuel supplied by the fuel line  43 , along with air drawn into the combustion chamber  22  through one or more air inlets  47 . The burner  42  creates products of combustion that rise through the flue  26  and heat the water by conduction through the flue walls. The flow of products of combustion is driven by natural convection, but may alternatively be driven by a blower unit communicating with the flue  26 . The above-described water heater  10  is well known in the art.  
         [0018]    During standby of the water heater  10  (i.e., when the burner  42  is not operating), the air and other gases in the flue  26  (collectively, “flue gases”) are heated by the water in the tank  14  and by the flame of the pilot burner  46 . This creates natural convection currents and imparts a buoyancy to the flue gases that causes the flue gases to flow toward the upper end  38  of the flue  26 . As used herein, “standby convection” means the natural convection within the flue  26  that occurs when the burner  42  is not operating, and that is caused by the water in the tank  14  and/or the flame of the pilot burner  46  warming the flue gases by heat transfer through the flue walls. Unrestricted flow of warm flue gases out of the flue  26  due to standby convection will result in standby heat loss from the water heater  10 .  
         [0019]    As seen in FIGS.  1 - 3 , to help reduce or eliminate standby convection heat losses, the water heater  10  includes a novel damper assembly  48 . The damper assembly  48  includes a hood  49 , a housing  50 , and an airflow apparatus  54 . The hood  49  permits ambient air to mix with the products of combustion as the products of combustion pass through the damper assembly  48 , and before the products of combustion are vented to the atmosphere.  
         [0020]    As used herein, the term “airflow apparatus” means an apparatus capable of creating airflow in the absence of any opposition to the airflow. The apparatus  54  includes a tubeaxial fan  56  having rotatable blades that create a flow of air parallel to an axis of rotation  58  of the fan blades. The axis of rotation  58  is disposed horizontally, and the fan  56  is exposed to the ambient air surrounding the water heater  10  such that air is drawn into the damper assembly  48  substantially along the axis of rotation  58 . The housing  50  defines an annular cavity surrounding the upper end  38  of the flue  26 . Circumferential slots or apertures  66  are provided in the annular cavity, and the slots  66  are preferably angled down to direct airflow out of the annular cavity into the upper end  38  of the flue  26 . With some modifications to the housing  50 , the tubeaxial fan  56  may be replaced with a radial fan.  
         [0021]    The fan  56  is preferably turned on during water heater standby, when the burner  42  is not operating. The fan  56  creates a downward pressure or back pressure zone over or within the upper end  38  of the flue  26 . The fan  56  and the standby convection currents create countervailing downward and upward pressures, respectively, within the flue  26 . In other words, in the absence of the fan  56 , standby convection would cause the flue gases to move vertically upward out of the upper end  38  of the flue  26 . In the absence of standby convection, the fan  56  would push air downwardly through the flue  26  and out of the air inlets  47 .  
         [0022]    A gate  68  is pivotably mounted in the housing  50  and is adjustable to restrict and open the air flow path from the fan  56  into the annular cavity of the housing  50 . The more open the air flow path, the higher the downward pressure exerted by the fan  56  will be. Therefore, for a single-speed fan  56 , the gate  68  setting determines the amount of downward pressure. Alternatively, the fan  56  may be a variable speed fan, in which case the downward pressure may be adjusted by adjusting the speed of the fan  56 , and the gate  68  would not be necessary.  
         [0023]    The water heater  10  also comprises a control system for the fan  56 . With reference to FIG. 1, the control system includes a controller  69  operatively interconnected between the fan  56  and a pressure switch  70  mounted on the gas valve  44 . When there is a call for heat, fuel flows through the gas valve  44  and to the burner  42 . The pressure in the gas valve  44  opens the pressure switch  70 , an electrical signal is relayed to the controller  69 , and the controller  69  turns the fan  56  off. Alternatively, a temperature switch  74  (illustrated in broken lines in FIG. 1) may be operatively interconnected with the controller  69  and mounted at the upper end  38  of the flue  26 . When the burner  42  fires, the flue gas temperature rises, thereby opening the temperature switch  74 . An electrical signal is relayed to the controller  69 , and the controller turns off the fan  56 . Alternatively, if there is a sufficiently strong flow of products of combustion through the flue  26  during operation of the burner  42 , and the fan  56  would not unduly restrict the flow of products of combustion out of the flue  26 , the fan  56  may be operated at all times.  
         [0024]    It is desirable to use as little energy as possible to drive the fan  56 . More specifically, the cost of driving the fan  56  should not exceed the cost savings associated with reducing standby heat loss from the flue  26 . One way to reduce the cost of driving the fan  56  is to use a thermoelectric generator  75  (illustrated in broken lines in FIG. 1) that converts heat provided by the pilot burner  46  (FIG. 1) into electricity that drives the fan  56 .  
         [0025]    FIGS.  4 - 8  illustrate alternative versions of the novel damper assembly  48 . Where elements in these figures are the same or substantially the same as the version described above, the same reference numerals are used.  
         [0026]    [0026]FIGS. 4 and 5 illustrate a second version of the damper assembly  48 . In this version, the axis of rotation  58  of the tubeaxial fan  56  is vertically-oriented, and air is drawn upwardly under the hood  49  of the damper assembly  48 , then downwardly through the fan  56  and into an annular cavity substantially identical to that described above. A portion of the hood  49  overhangs the fan  56  and defines a right angle entry channel  76  into the damper assembly  48 . The air then follows a second right angle turn down through the fan  56 , and a third right angle turn into the slots  66 . The right angle turns may be slightly more or less than 90°.  
         [0027]    The second version may also have similar control and power systems as described above, and may operate under the control of a similar controller  69 . The second version may also employ a gate  68  or variable speed fan as described above with respect to the first version. As with the first version, a radial fan may be used in place of the tubeaxial fan  56  with some modifications to the housing  50 . Because the fan  56  used in the first and second versions would cause a downward flow of air into the flue  26  in the absence of standby convection flow of flue gases, the first and second versions may be termed “circumferential downdraft” versions.  
         [0028]    [0028]FIGS. 6 and 7 illustrate a third version of the damper assembly  48 . This version may be termed an “air curtain” version. In this version, a housing  78  is mounted to the upper end  38  of the flue  26 . The housing  78  includes first and second airflow chambers or ducts  82 ,  86  and a turn-around chamber  90 . The chambers  82 ,  86 ,  90  communicate with each other and define a loop for airflow. A radial fan or blower  94  is in the first chamber  82 .  
         [0029]    During operation of the fan  94 , air is drawn and pushed by the fan  94  from the second chamber  86 , through the first chamber  82 , across the upper end  38  of the flue  26 , into the turn-around chamber  90 , and back into the second chamber  86 . The resulting curtain of air flowing across the upper end  38  of the flue  26  substantially prevents the flow of warm flue gases out of the upper end  38  of the flue  26  under the influence of standby convection alone. The third version may also have similar control and power systems as described above, and may operate under the control of a similar controller  69 . The radial fan  94  of this version may be replaced with a tubeaxial fan with some modifications to the housing  78 .  
         [0030]    [0030]FIG. 8 illustrates a fourth version of the damper assembly  48 . This version includes one or more first electrodes  98  having pointed ends. FIG. 9 illustrates one construction in which the first electrodes  98  include four electrodes  98  arranged in a square pattern with a fifth electrode  98  in the center of the square. It should be noted, however, that other numbers and configurations of electrodes  98  may be substituted for the illustrated arrangement.  
         [0031]    The first electrodes  98  are connected to a device for providing electrical voltage, such as the illustrated spark plug  102 . The spark plug  102  is interconnected with a power supply  106  by way of a conductive wire  110 . It is preferable to supply DC power to the first electrodes  98 , and the power supply  106  may therefore be a DC power source or an AC power source with a DC converter or an AC signal imposed on a DC power source. The power supply  106  is grounded to the flue wall by way of a grounding wire  114 , and therefore a portion of the flue wall acts as a second electrode having a polarity opposite the first electrodes  98 . There is therefore a high voltage difference between the first electrodes  98  and the flue wall. A voltage difference of 8-10 kV is preferable, but it may also be higher.  
         [0032]    When the power supply  106  is actuated, a positive charge is applied to the first electrodes  98 . The positive charge ionizes particles in the air around the first electrodes  98 , and the ionized particles are drawn or attracted to the oppositely-charged flue wall. The pointed ends of the first electrodes  98  facilitate the creation of the ionized particles, and the relatively large size of the second electrode (i.e., the flue  26 ) ensures that the ionized particles will be attracted to the second electrode. The ionized particles are therefore biased for movement toward the flue wall, and bump into flue gas particles in or exiting the upper end  38  of the flue  26 . This creates a downward pressure on the flue gases that substantially prevents the flue gases from escaping through the upper end  38  of the flue  26 . The fourth version may therefore also be considered a downdraft damper.  
         [0033]    Alternatively, the first electrodes  98  may be positioned to the side of the upper end  38  of the flue  26  and a second electrode or electrodes may be positioned on the other side of the upper end  38  such that a cross-flow of ionic wind is created across the upper end  38 , resulting in an air curtain similar to that described above in the third version. The fourth version may also have similar control system as described above, and may operate under the control of a similar controller  69 .  
         [0034]    It should be noted that all versions of the illustrated apparatus for creating airflow are able to substantially prevent the flow of flue gases out of the flue  26  under the influence of standby convection without the use of a physical obstruction (e.g., a conventional solid damper valve) being placed over the upper end  38  of the flue  26 .