Method for producing a series of at least a first and a second heat exchanger, each exchanger comprising: - at least one heat exchange matrix unit which comprises a successive stack of separator sheets and of corrugated fins delimiting a plurality of passages suited to allowing at least a first fluid, a second fluid and a third fluid to flow through the matrix unit, so that the third fluid can heat or be heated by the first and second fluids, each plate having a length and a width, the stack having a direction of stacking perpendicular to the length and to the width of the sheets, - the matrix unit comprising a predetermined number of openings which are each formed in a peripheral face of the matrix unit and which each communicate with one of the said associated passages, - at least one elongate fluid distribution tank (24, 42) which caps at least some of the openings and which is connected to a pipe (30, 40), the axis of the tank being parallel to the direction of stacking and perpendicular to the width and to the length of the sheets, - the matrix unit or units of the first exchanger being substantially identical to that/those of the second exchanger, - the method consisting in adapting the exchangers of the series by partitioning the tank into several compartments using a partitioning means (26, 32, 34) provided for that purpose, so as to distribute the number of openings assigned to the first fluid and to the second fluid, characterized in that the partitioning means (26, 32, 34) is designed to divide the said tank into several compartments which are each connected to a pipe for the passage of the first fluid or to a pipe for the passage of the second fluid and which each communicate with a number of openings that varies according to the configuration adopted by the partitioning means (26, 32, 34), so as to distribute the number of openings assigned to the first fluid and to the second fluid. - at least one heat exchange matrix unit which comprises a successive stack of separator sheets and of corrugated fins delimiting a plurality of passages suited to allowing at least a first fluid, a second fluid and a third fluid to flow through the matrix unit, so that the third fluid can heat or be heated by the first and second fluids, each plate having a length and a width, the stack having a direction of stacking perpendicular to the length and to the width of the sheets, - the matrix unit comprising a predetermined number of openings which are each formed in a peripheral face of the matrix unit and which each communicate with one of the said associated passages, - at least one elongate fluid distribution tank (24, 42) which caps at least some of the openings and which is connected to a pipe (30, 40), the axis of the tank being parallel to the direction of stacking and perpendicular to the width and to the length of the sheets, - the matrix unit or units of the first exchanger being substantially identical to that/those of the second exchanger, - the method consisting in adapting the exchangers of the series by partitioning the tank into several compartments using a partitioning means (26, 32, 34) provided for that purpose, so as to distribute the number of openings assigned to the first fluid and to the second fluid, characterized in that the partitioning means (26, 32, 34) is designed to divide the said tank into several compartments which are each connected to a pipe for the passage of the first fluid or to a pipe for the passage of the second fluid and which each communicate with a number of openings that varies according to the configuration adopted by the partitioning means (26, 32, 34), so as to distribute the number of openings assigned to the first fluid and to the second fluid.