Patent ID: 7523721

Claim:
A heat exchanger comprising: a housing including 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; and a combustion gas path formed around the coiled tube for guiding the combustion gas flowed thereto to the combustion gas outlet; wherein the heat exchanger further comprises a partition which closes an axially intermediate portion of the space to partition the space in the axial direction into a first and a second regions and to partition the coiled tube into a first and a second heat exchanging portions surrounding the first region and the second region, respectively and each including a plurality of loops and a plurality of clearances; wherein combustion gas supplied to the first region flows to the combustion gas path by passing through a plurality of clearances of the first heat exchanging portion and then passes through a plurality of clearances of the second heat exchanging portion, wherein the coiled tube comprises a flat tube having a thickness in the axial direction and a width in a direction crossing the axial direction, the width being larger than the thickness, and wherein the width of the flat tube is larger in the second heat exchanging portion than in the first heat exchanging portion.