NOVELTY - The process of manufacturing a heat exchanger comprising a module (1) traversing through a row of fluid flow channel (2), comprises preparing the module by forming a set comprising parallel metal pipes each forming the fluid flow channels with their interior space, and treating the assembly to obtain a welding of pipes with the metal matrix, plates and two metal joint elements. Pipes are arranged between two metallic plates, and spaces are defined by the consecutive pipes. Metal plates are packed by a metal matrix for filling.    USE - The process is useful for manufacturing a heat exchanger comprising a module traversing through a row of fluid flow channel, where the heat exchanger is useful for the production of chemical or pharmaceutical products and in fuel cell installations.    ADVANTAGE - The process ensures easy, economical, safe, reliable and rapid manufacture of a heat exchanger with improved geometry and performance and increased thermal conductivity.    DETAILED DESCRIPTION - The process of manufacturing a heat exchanger comprising a module (1) traversing through a row of fluid flow channel (2), comprises preparing the module by forming a set comprising parallel metal pipes each forming the fluid flow channels with their interior space, and treating the assembly to obtain a welding of pipes with the metal matrix, plates and two metal joint elements. Pipes are arranged between two metallic plates, and spaces are defined by the consecutive pipes. Metal plates are packed by a metal matrix for filling. An assembly integrating two metal joint elements is provided with many traversing holes that are housed respectively at one of the two ends of the pipes, and the other is provided with traversing holes that are housed respectively with the other of the two pipe ends. The material removal is carried out on one of two metal joint elements between two direct consecutive holes to create a channel of junction between the two holes. A closing plate is placed on the joint element to make the channel of junction sealed between the two directly consecutive holes. The assembly is prepared to integrate a strengthening envelope in which the rest of the set is slided. The heat exchanger further comprises a single holder, and a first and a second superposed module respectively traversed by a row of first fluid flow channels and by a row of second fluid flow channels. The first assembly comprises first metal pipes each forming first fluid flowing channels, first ducts arranged between the first two metal plates, and spaces defined by first consecutive pipes. The first metal plates are packed by a first metal matrix of filling. The second assembly comprises second metal pipes each forming second fluid flow channels, second pipes that are arranged between two second metal plates, and second spaces defined by the second pipes. The second consecutive metal plates are filled by a second metal matrix of filling. The second assembly is superimposed on the first assembly. The treatment includes hot isostatic pressing carried out at a temperature of 1040 degrees C and a pressure of 1200 bars for 2 hours. The metal matrix for filling and the plates are made of high heat conductivity alloy with a powdered metal. The fluid flow channels are equipped with an insert partially coated with a catalyst allowing a catalytic chemical reaction within the channel.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic perspective view of a fluid circulation module.    Module (1)    Fluid flow channel. (2)