HEAT EXCHANGER

A condensing heat exchanger comprises a combustion chamber, provided at its top with room for the installation of a premix gas burner. The heat exchanger comprises a flue gas draft,delimited by walls, among which two water cooled walls between which flue gas can flow. Each of the water cooled walls comprises channels for water flow. The combustion chamber is bound at its top at least partly by the room provided for the burner;at its sides by a set of two first combustion chamber walls opposite to each other; and by a set of two second combustion walls opposite to each other; and at its bottom by the flue gas draft. The first combustion chamber walls are provided with channels for water flow. The first combustion chamber walls are provided as extensions of water cooled walls delimiting the flue gas draft. The two first combustion chamber walls each comprise a first segment and a second segment, located below the first segment. The first segments are each curved so that the section of the combustion chamber bound by the first segments widens in the downstream flue gas flow direction. Each of the two first segments is provided with channels for water flow. The second segments are each curved so that the section of the combustion chamber bound by the second segments narrows in flue gas downstream direction. The second segment of the first combustion chamber walls comprises longitudinal fins elongated in the direction away from the top of the combustion chamber and extending into the combustion chamber. The first segment of the first combustion chamber walls is smooth meaning that it does not comprise heat exchange increasing protrusions extending in the combustion chamber. Un échangeur de chaleur à condensation comprend une chambre de combustion, disposée sur sa partie supérieure avec de l'espace pour l'installation d'un brûleur à gaz à prémélange. L'échangeur de chaleur comprend un tirage de gaz de combustion, délimité par des parois, dont deux parois refroidies à l'eau entre lesquelles s'écoule un gaz de combustion. Chacune des parois refroidies à l'eau comprend des canaux pour l'écoulement de l'eau. La chambre de combustion est liée au niveau de sa partie supérieure, au moins en partie, par l'espace destiné au brûleur ; au niveau de ses côtés par un ensemble de deux premières parois de chambre de combustion opposées l'une à l'autre ; et par un ensemble de deux secondes parois de chambre de combustion opposées l'une à l'autre ; et au niveau de sa partie infé