Fuel-fired water heater with air draft inducer and flue heat exchanger

Abstract

A fuel-fired water heater has a tank which holds a reserve of water to be heated by a burner located in a sealed combustion chamber disposed under a bottom heat transfer wall of the tank. A combustion gas exhaust flue extends vertically through the center of the tank in contact with the water therein. A restrictive baffle is secured inside the gas exhaust flue to retard hot gases rising in the flue from the combustion chamber whereby to increase heat transfer from the hot gases to the water in contact with the exhaust flue. A draft inducing blower is secured in a top end of the exhaust flue above the top wall of the tank. A heat exchanger is in communication with a heat exchange section of the flue above the top end of the exhaust flue to extract further heat from residual hot gases in the exhaust flue.

1 . A fuel-fired water heater comprising a tank for holding a reserve of water to be heated by a burner located in a sealed combustion chamber disposed under a bottom heat transfer wall of said tank, air supply means to supply air for said burner, a combustion gas exhaust flue extending vertically through said tank in contact with water therein, said exhaust flue having a bottom open end thereof in communication with said sealed combustion chamber through said bottom heat transfer wall, said exhaust flue extending through a top wall of said tank, a high-efficiency restrictive baffle secured inside said gas exhaust flue to retard hot gases rising in said gas exhaust flue to increase heat transfer from said hot gases to said water in contact with said exhaust flue, a draft inducing blower in communication with a top end of said exhaust flue above said top wall of said tank to allow for increased efficiency of said restrictive baffle for the transfer of heat from said hot gases, and a heat exchanger in communication with a heat exchange section of said exhaust flue above said top wall of said tank to extract further heat from residual hot gases in said exhaust flue. 
     
     
         2 . A fuel-fired water heater as claimed in  claim 1  wherein said heat exchanger is a heat extracting conduit coil in contact about said heat exchange section of said exhaust flue, said heat extracting conduit coil having an inlet end in communication with a feed tube extending to a lower end of said tank to extract cool water therefrom, said heat extracting conduit coil having an outlet end in communication with a return conduit to discharge heated water from said heat extracting conduit coil in an upper section of said tank, and a pump secured to one of said inlet or outlet end of said heat extracting conduit coil to circulate water therethrough. 
     
     
         3 . A fuel-fired water heater as claimed in  claim 1  wherein said heat exchanger is a heat extracting coil assembly disposed inside said heat exchange section of said exhaust flue, said heat extracting coil assembly having a conduit coil having an inlet end in communication with a feed tube extending to a lower end of said tank to extract cool water therefrom, said heat extracting coil having an outlet end in communication with a return conduit to discharge water from said heat extracting conduit coil in an upper section of said tank, and a pump secured to one of said inlet or outlet end of said heat extracting conduit coil to circulate water therethrough. 
     
     
         4 . A fuel-fired water heater as claimed in  claim 3  wherein said heat extracting coil is secured in a heat transfer module comprised of a series of spaced-apart heat sink fins for extracting heat from said residual hot gases in said exhaust flue and transferring heat to said heat extracting coil, said heat transfer module providing a baffle for exhausting flue gases. 
     
     
         5 . A fuel-fired water heater as claimed in  claim 1  wherein said heat exchanger comprises a housing having a heat exchanger coil supported therein, support means to insulatingly support said housing about an open top end of said exhaust flue above said top wall of said tank, said open top end of said exhaust flue being disposed in a central through hole formed by said heat exchanger coil, a deflector member supported in an upper portion of said central through bore spaced about said open top end and extending inside an inner surface of said heat exchanger coil, said housing having an exhaust port in a top wall thereof spaced above said central through bore, said draft inducing blower being secured about said exhaust port, said heat exchanger coil being supported in said housing spaced above a bottom wall of said housing whereby said hot gases rising in said gas exhaust flue are deflected downwardly by said deflector member to be connected towards a lower end of said heat exchanger coil to heat water pumped through said heat exchanger coil, said hot gases being cooled by said heat exchanger coil and exhausted through said exhaust port. 
     
     
         6 . A fuel-fired water heater as claimed in  claim 5  wherein said heat exchanger coil is comprised of two or more spaced-apart concentric conduit windings, said conduit windings having an inlet end and an outlet end, said inlet and being connected to a water supply conduit in communication with a lower end of said tank to extract cold water therefrom, said outlet end being secured to a return conduit secured to an upper section of said tank to discharge heated water from said heat exchanger coil therein, and a pump secured to one of said inlet or outlet end to circulate water through said heat exchanger coil. 
     
     
         7 . A fuel-fired water heater as claimed in  claim 6  wherein a vent pipe is secured to said draft inducer to exhaust said hot gases exiting said exhaust port to atmosphere. 
     
     
         8 . A fuel-fired water heater as claimed in  claim 6  wherein said housing is a thermally insulated housing. 
     
     
         9 . A fuel-fired water heater as claimed in  claim 5  wherein said deflector member is an inverted casing having a cylindrical side wall, a top wall and an open bottom end; said open bottom end being of larger diameter than the diameter of said exhaust flue to define an annular passage between said cylindrical side wall and said exhaust flue for the connection of said hot gases. 
     
     
         10 . A fuel-fired water heater as claimed in  claim 9  wherein said top wall of said inverted casing is a thermally insulated top wall. 
     
     
         11 . A fuel-fired water heater as claimed in  claim 10  wherein said top wall has a concave curvature in an inner face thereof to facilitate a reverse flow of said hot gases exiting said open top end of said exhaust flue. 
     
     
         12 . A fuel-fired water heater as claimed in  claim 9  wherein said cylindrical side wall is a heat conducting side wall disposed in frictional contact with an inner one of said concentric conduit windings, said inner one of said concentric conduit windings having a coil section thereof flattened for contact with their heat conducting side wall. 
     
     
         13 . A fuel-fired water heater as claimed in  claim 1  wherein said petroleum-fired water heater is a gas-fired domestic water heater. 
     
     
         14 . A fuel-fired water heater as claimed in  claim 13  wherein said tank is one of an inner glass-lined tank or stainless steel tank or other suitable tank, an outer casing spaced from said inner tank and an insulation disposed between said inner tank and said outer casing. 
     
     
         15 . A fuel-fired water heater as claimed in  claim 1  wherein there is further provided a damper in said top end of said exhaust flue to substantially close said exhaust flue when said draft inducer is inoperative. 
     
     
         16 . A fuel-fired water heater as claimed in  claim 1  wherein there is further provided a flammable vapor sensor secured to a bottom and of said water heater to prevent said burner to be ignited in the presence of flammable vapors. 
     
     
         17 . A fuel-fired water heater as claimed in  claim 1  wherein said restrictive baffle provides a thermal efficiency of at least 80%. 
     
     
         18 . A fuel-fired water heater as claimed in  claim 17  wherein said restrictive baffle in combustion with said heat exchanger increases the efficiency to about 93%.