Patent ID: 7458340
Filing Date: 2008-12-02
Classification: F24H,F28D,F28F,Y02B

Abstract:
1. A water heater comprising a burner, a primary heat exchanger for recovering sensitive heat from combustion gas generated by the burner, and a secondary heat exchanger for recovering latent heat from the combustion gas; the secondary heat exchanger comprising: a plurality of water tubes extending in a predetermined direction and each including a first end and a second end spaced from each other in the predetermined direction; a casing including a plurality of walls surrounding the water tubes, one of the walls being formed with a gas supply port for introducing combustion gas passed through the primary heat exchanger into the secondary heat exchanger, whereas another one of the walls being formed with a gas discharge port for discharging the combustion gas to outside; and a header including a water inlet and a hot-water outlet and connected to the respective first ends of the water tubes for performing water inflow to the water tubes and hot-water outflow from the water tubes; wherein the water tubes are so inclined that the first ends are positioned lower than the second ends for causing water to flow into the header when water inflow is stopped to drain water from the water tubes; wherein the plurality of walls of the casing include an upper wall and a bottom wall positioned above and below the water tubes via an upper gap and a lower gap, respectively, and a rear wall and a front wall positioned behind and in front of the water tubes, respectively, the rear wall comprising the wall formed with the gas supply port whereas the front wall comprising the wall formed with the gas discharge port, so that the combustion gas flows through a space between the water tubes and through the upper and the lower gaps generally horizontally and width wise in a front and rear direction of the casing; and wherein the upper wall and the bottom wall are so inclined that inner surfaces thereof extend generally in parallel with the water tubes, and each of the upper and the lower gaps has a width which is generally constant along said predetermined direction.