Dual function high efficiency water heater

A gas-fired natural draft water heater, comprising the combination of

• a vertically aligned insulated cylindrical water-tight sealed storage tank having lower and upper headers, a burner underlying the lower header operable to generate hot flue gases, and cold water inlet and hot water outlet connections in the tank for conveying water there through;
• a water-tight thermally conductive flue pipe extending axially and generally concentrically of the storage tank between sealed end connections in the headers for conveying the flue gases through the tank, with the water in the tank being annular of and substantially contacting all of the exterior surfaces of the flue pipe;
• said flue pipe having inlet and outlet end segments sealed to the headers and an intermediate segment larger in cross-section than the end segments;
• said intermediate segment being continuous and comprised of consecutive upstream, intermediate and downstream contours, where said intermediate contour extends axially of the cylindrical tank, and said upstream and downstream contours are extended transversely of the cylindrical tank;
• and
• an impervious baffle mounted in the intermediate flue pipe segment and disposed transversely of the cylindrical tank, with the baffle peripheral edge being spaced from the intermediate contour of the flue pipe segment operable for defining an annular flue gas flow path around the baffle and transversely of the tank wall for increasing heat transfer between the flue gas and adjacent tank water.

A gas-fired water heater, comprising the combination of

• a vertically aligned insulated generally cylindrical storage tank, an inner shell within the tank, means sealing the shell and tank together at respective lower and upper ends whereby a closed water-tight chamber is defined therebetween, and inlet and outlet connections for the chamber operable to convey water there through;
• said shell having a circular array of impervious axially extended passages between the lower and upper chamber ends, each passage being defined by exterior walls including a curved wall segment spaced inwardly adjacent the tank and a pair of side walls converging inwardly from the opposite ends of each curved wall segment to meet at an inboard liquid-tight corner, and the adjacent passage side walls and inboard corners being circumferentially and radially separated respectively defining starlike extensions of the chamber whereby chamber water can contact all of the exterior passage surfaces;
• and
• a burner underlying the storage tank operable to generate hot flue gases;
• and headers adjacent respective lower and upper open ends of the passages for conducting said flue gases through the passages and away from burner and the water heater.