Heat exchanger comprising at least: - one duct, extending mainly along a vertical axis, formed at least of one polymer material, the exchanger being intended to make circulate inside the duct, a first fluid partially at least in steam form and to transfer at least one portion of the heat from the first fluid to a second fluid flowing over an outer wall of the duct, this heat transfer producing a condensation of at least one portion of the first fluid over the inner wall of the duct and an evaporation of at least one portion of the second fluid; - one collection orifice vertically located under a lower end of the duct and configured to recover the first fluid having condensed inside the duct; - a fluidic connection device comprising at least: - one keel comprising a head and a rod extending from the head and an inner channel passing through the head and the rod; the head being configured to be inserted inside an end of the duct; a free end of the rod being intended to be inserted into the collection orifice; the keel being configured so as to guide through the inner channel thereof, the first condensed fluid flowing from the end of the duct; - the connection device is configured so as to clamp the duct on an outer wall of the head of the keel so as to ensure the retaining of the keel on the duct characterised in that it comprises a sleeve having an inner passage configured to house said lower end of the duct, the sleeve extending along at least one portion of the inner channel of the keel and being configured such that the second fluid flowing over the outer wall of the duct then flows over an outer wall of the sleeve by being maintained at a distance from the inner channel of the keel; - the connection device being shaped such that the sleeve is retained by the keel or by at least one abutment element (60, 95) returned on the keel so as to prevent the falling of the sleeve through gravity. - one duct, extending mainly along a vertical axis, formed at least of one polymer material, the exchanger being intended to make circulate inside the duct, a first fluid partially at least in steam form and to transfer at least one portion of the heat from the first fluid to a second fluid flowing over an outer wall of the duct, this heat transfer producing a condensation of at least one portion of the first fluid over the inner wall of the duct and an evaporation of at least one portion of the second fluid; - one collection orifice vertically located under a lower end of the duct and configured to recover the first fluid having condensed inside the duct; - a fluidic connection device comprising at least: - one keel comprising a head and a rod extending from the head and an inner channel passing through the head and the rod; the head being configured to be inserted inside an end of the duct; a free end of the rod being intended to be inserted into the collection orifice; the keel being configured so as to guide through the inner channel thereof, the first condensed fluid flowing from the end of the duct; - the connection device is configured so as to clamp the duct on an outer wall of the head of the keel so as to ensure the retaining of the keel on the duct characterised in that it comprises a sleeve having an inner passage configured to house said lower end of the duct, the sleeve extending along at least one portion of the inner channel of the keel and being configured such that the second fluid flowing over the outer wall of the duct then flows over an outer wall of the sleeve by being maintained at a distance from the inner channel of the keel; - the connection device being shaped such that the sleeve is retained by the keel or by at least one abutment element (60, 95) returned on the keel so as to prevent the falling of the sleeve through gravity. - one keel comprising a head and a rod extending from the head and an inner channel passing through the head and the rod; the head being configured to be inserted inside an end of the duct; a free end of the rod being intended to be inserted into the collection orifice; the keel being configured so as to guide through the inner channel thereof, the first condensed fluid flowing from the end of the duct; - the connection device is configured so as to clamp the duct on an outer wall of the head of the keel so as to ensure the retaining of the keel on the duct characterised in that it comprises a sleeve having an inner passage configured to house said lower end of the duct, the sleeve extending along at least one portion of the inner channel of the keel and being configured such that the second fluid flowing over the outer wall of the duct then flows over an outer wall of the sleeve by being maintained at a distance from the inner channel of the keel; - the connection device being shaped such that the sleeve is retained by the keel or by at least one abutment element (60, 95) returned on the keel so as to prevent the falling of the sleeve through gravity.