Patent ID: 7428883

Claim:
A heat exchanger comprising: a housing including a cylindrical circumferential wall and axially opposite ends formed with a burner opening and a combustion gas outlet, respectively; a heat-exchange coiled tube including a plurality of loops arranged in the housing along the axial direction via a plurality of clearances; a space surrounded by the coiled tube and having one end communicating with the burner opening; a partition for preventing combustion gas supplied into the space from directly flowing through another end of the space and for causing the combustion gas to flow to the clearances; and a combustion gas path formed around the coiled tube and surrounded by the circumferential wall of the housing for guiding the combustion gas flowed thereto from the space by passing through the clearances to the combustion gas outlet; wherein the loops comprise a tube having a thickness in the axial direction and a width in a direction perpendicular to the axial direction, the width being larger than the thickness; and wherein one of the axially opposite ends of the housing is provided with a drain receiving portion for receiving drain when the drain is generated at the coiled tube; the drain receiving portion being in a form of a ring having a center portion formed with an opening corresponding to either one of the combustion gas outlet and the burner opening and positioned below the coiled tube and the combustion gas path.