HEAT EXCHANGER

The present invention relates to a heat exchanger for exchanging heat between first and second fluids, said exchanger including: a casing and an exchange bundle positioned inside said casing, wherein the exchange bundle includes: a main surface which has a main width and which consists of a plurality of tubes suitable for guiding the first fluid inside said tubes; an intake of the first fluid toward an outlet of the first fluid, making it possible to guide, outside of said tubes, the second fluid; an intake of the second fluid toward an outlet of the second fluid; wherein the tubes are, at least at one first end, assembled such as to form a secondary surface having a secondary width which is smaller than the main width for coupling with the intake and/or the outlet of the first fluid; wherein the secondary surface at the first end of the tubes is formed such as to create a space between the casing and the outer surface of the secondary surface, said space being connected to the intake and/or the outlet of the second fluid.