Abstract:
A water heater including a storage tank, a combustion chamber, a burner for producing products of combustion, the burner positioned in the combustion chamber, a flue extending from the combustion chamber through the storage tank, and a baffle positioned within the flue and directing the flow of the products of combustion through the flue. The baffle includes multiple clockwise twist segments and multiple counterclockwise twist segments.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to water heaters, and more particularly to water heaters including flue baffles. 
         [0002]    A flue baffle is positioned in the flue tube of a gas-fired water heater. A burner combusts a fuel and air mixture to create products of combustion or exhaust gases. The gases flow through the flue tube to heat the water stored in a tank. The baffle enhances the heat exchange rate between the gases and the water stored in the tank. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention provides, in one aspect, a water heater including a storage tank, a combustion chamber, a burner for producing products of combustion, the burner positioned in the combustion chamber, a flue extending from the combustion chamber through the storage tank, and a baffle positioned within the flue and directing the flow of the products of combustion through the flue. The baffle includes multiple clockwise twist segments and multiple counterclockwise twist segments. 
         [0004]    The present invention provides, in another aspect, a baffle for use in the flue of a water heater to direct the flow of products of combustion through the flue. The baffle includes multiple clockwise twist segments and multiple counterclockwise twist segments. 
         [0005]    Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a perspective view of a water heater. 
           [0007]      FIG. 2  is a perspective view of a baffle of the water heater of  FIG. 1 . 
           [0008]      FIG. 3  is a front view of the baffle of  FIG. 2 . 
           [0009]      FIG. 4  is a side view of a portion of a sheet used to form the baffle of  FIG. 1 . 
           [0010]      FIG. 5  is a front view of a second embodiment of a baffle. 
       
    
    
       [0011]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
       DETAILED DESCRIPTION 
       [0012]      FIG. 1  illustrates a water heater  100  including a base pan  105 , a tank  110  supported by the base pan  105  and containing water, an insulating jacket  115  surrounding the tank  110 , and a burner  120 . A flammable fuel is provided to the burner  120  by a fuel inlet  125  connected to a fuel valve  130 . The burner  120  is positioned in a combustion chamber  135  beneath the tank  110 . The fuel valve  130  is connected to a fuel supply. The fuel can be, for example, natural gas or propane. The combustion chamber  135  is connected to an air supply, for example, the atmosphere around the water heater  100 . A flue tube  140  extends from the combustion chamber  135  through the tank  110 . The flue tube  140  includes a central longitudinal axis  145 . The products of combustion or exhaust gases created by the burner  120  flow through the flue tube  140  to heat the water stored in the tank  110 . A cold water inlet pipe  150  supplies cold water to the tank  110 . A hot water supply pipe  155  supplies hot water to an end-use location, for example, a faucet. The water heater  100  as described above is conventional. 
         [0013]    As shown in  FIG. 1 , a baffle  160  is positioned within the flue tube  140 . A hanger or cross-bar  165  supports and positions the baffle  160  within the flue tube  140 . In some embodiments, other suitable means are used to support and position the baffle  160  within the flue tube  140 . The baffle  160  extends longitudinally within the flue tube  140 . Preferably, a central longitudinal axis  170  of the baffle  160  is collinear with the longitudinal axis  145  of the flue tube  140 . The baffle  160  is positioned within the flue tube  140  to leave a space  172  between the lower end of the baffle  160  and the lower end of the flue tube  140 . The space  172  facilitates mounting the flue tube  140  and baffle  160  on a glass coating machine that coats the inside and outside of the flue tube  140  and the baffle  160  with a protective coating to resist degradation or corrosion of the flue tube  140  and baffle  160 . Also, the space  172  makes the baffle  160  less likely to be overheated by extreme temperatures in the combustion chamber  135 . The space  172  can be, for example, about three inches (7.62 centimeters) in length but such length may vary based on manufacturing parameters. In other embodiments, the lower end of the baffle  160  is flush with the lower end of the flue tube  140 . 
         [0014]    As shown in  FIGS. 2-3 , the baffle  160  includes six clockwise twist segments or twists  175  and six counterclockwise twist segments or twists  180  that alternate with each other along the longitudinal axis  170  of the baffle  160  so that each clockwise twist  175  is adjacent to a counterclockwise twist  180 . A substantially flat or planar spacer  190  is positioned between each adjacent clockwise twist  175  and counterclockwise twist  180 . Each spacer  190  is positioned in a vertical plane that includes the longitudinal axis  170 . The length of each spacer  190  along the longitudinal axis  170  can vary as necessary. Preferably, the length of a spacer is 0.36 inches (0.91 centimeters). Preferably, each clockwise twist  175  is a one hundred eighty degree twist and each counterclockwise twist  180  is a one hundred eighty degree twist. That is, a sheet or plate  195  is twisted clockwise one hundred eighty degrees about the longitudinal axis  170  to form a clockwise twist  175  and then the same sheet is twisted counterclockwise one hundred eighty degrees about the longitudinal axis  170  to form a counterclockwise twist  180 . The length of each clockwise twist  175  along the longitudinal axis  170  is substantially the same and the length of each counterclockwise twist  180  along the longitudinal axis  170  is substantially the same. In some embodiments, each clockwise twist  175  is twisted more or less than one hundred eighty degrees and each counterclockwise twist  180  is twisted more or less than one hundred eighty degrees. For example, each twist  175  and  180  could be twisted ninety degrees or three hundred sixty degrees. More or fewer twists  175  and  180  can be included as necessary. Preferably, the baffle has a diameter of 3.625 inches (9.207 centimeters) and an overall length of 45.25 inches (114.9 centimeters), the length along the longitudinal axis  170  of each of the twists  175  and  180  is between three inches (7.62 centimeters) and six inches (15.24 centimeters), and the flue tube  140  has a diameter of four inches (10.16 centimeters). In some embodiments, a spacer  190  is not positioned between each adjacent clockwise twist  175  and counterclockwise twist  180 . In other embodiments, the spacer  190  is corrugated. 
         [0015]    As shown in  FIGS. 1-3 , the baffle  160  is corrugated.  FIG. 4  shows a side view of a portion of the sheet  195  used to form the baffle  160  before the sheet  195  is twisted. The sheet  195  includes an alternating series of peaks  200  and valleys  205  that form the corrugations. Alternatively, the baffle  160  is manufactured from a substantially flat or planar sheet or plate. The sheet  195  can be manufactured of mild (i.e., low carbon) steel, stainless steel, Inconel®, nickel alloy, or other suitable materials. For example, the baffle  160  can be cold formed from a steel sheet  195 . However, cold forming a steel sheet  195  limits how short of a twist length can be formed for each of the twists  175  and  180 . It is to be understood that other processes and/or methods of processing a material to form the baffle  160  fall within the scope of the invention. For example, the clockwise twists  175  and the counterclockwise twists  180  can be formed individually and then secured together, for example, by welding, brazing, or soldering. 
         [0016]      FIG. 5  shows an alternative baffle  360  similar to the baffle  160 . Components similar to those of the baffle  160  described above are numbered in a similar fashion plus two hundred. The baffle  360  has a varying pitch so that the length of at least one of the clockwise twists  375  along the longitudinal axis  370  varies with respect to the length of a different one of the clockwise twists  375  and so that the length of at least one of the counterclockwise twists  380  along the longitudinal axis  370  varies with respect to the length of a different one of the counterclockwise twists  380 . The baffle  360  includes three groups  210 ,  215 , and  220  of twists  375  and  380 . In the first group  210 , the lengths of each of the clockwise twists  375  and the counterclockwise twists  380  are a first length. In the second group  215 , the lengths of each of the clockwise twists  375  and the counterclockwise twists  380  are a second length different than the first length. In the third group  220 , the lengths of each of the clockwise twists  375  and the counterclockwise twists  380  are a third length different than both the second length and the first length. Preferably, the first length is three inches (7.62 centimeters), the second length is four inches (10.16 centimeters), and the third length is five inches (12.7 centimeters). More or fewer groups of twists  375  and  380  of the same length can be used as necessary. The number of twists  375  and  380  in a group can vary and a group can consist of a single twist  375  or  380 . 
         [0017]    In use, the burner  120  combusts a fuel and air mixture to create products of combustion or exhaust gases. The gases exit the combustion chamber  135  and enter the lower end of the flue tube  140 . As the gases encounter the baffle  160 , the gases are directed in a circuitous path along the alternating clockwise twists  175  and counterclockwise twists  180 . The alternating clockwise twists  175  and counterclockwise twists  180  create tangential and radial movement of the gases which increases both the amount of contact between the gases and the wall of the flue tube  140  and the turbulent kinetic energy of the gases. These in turn increase the heat transfer rate between the gases and the water stored in the tank  110 . Additionally, the twists  175  and  180  increase the residence time of the gases within the flue tube  140 , which also increases the heat transfer rate. The corrugations of the baffle  160  improve the radiative heat transfer when compared to a non-corrugated baffle. Also, the corrugations increase the amount of turbulent flow in the gases, which increases the convective heat transfer when compared to a non-corrugated baffle. Enhancing the heat transfer rate between the gases and the water stored in the tank  110  improves the energy factor (EF) of the water heater  100 . The baffle  160  with alternating clockwise twists  175  and counterclockwise twists  180  significantly increases the heat transfer rate as compared to a baffle with twists all in the same direction. Shorter twist lengths, which result in more twists  175  and  180  for a baffle  160  of a certain length, provide the most heat transfer enhancement. However, the pressure drop caused by the baffle  160  along the flue tube  140  increases as the twists lengths decrease. The baffle  360  with twists  375  and  380  of varying lengths helps to optimize the heat transfer rate in relation to the pressure drop. Also, the length of the spacers  190 ,  390  can be varied to assist in optimizing the heat transfer rate in relation to the pressure drop. Various features of the invention are set forth in the following claims.