Abstract: A tubular heat exchanger includes a substantially cylindrical sheathing tube having a center piece and two end pieces of a length which is shorter than a length of the center piece. Two perforated bases are respectively received in the end pieces and sized to occupy a cross section thereof, and two end caps are respectively secured to axial ends of the end pieces. Extending in substantial parallel relationship inside the sheathing tube between the perforated bases are a plurality of internal tubes to thereby define a first fluid space between an inner surface of the sheathing tube and outer surfaces of the internal tubes, and a separate second fluid space bounded by inner surfaces of the internal tubes and the end caps on the end pieces. A lateral connection pipe is secured to each end piece and fluidly communicates with the first fluid space in a region adjacent to the perforated bases for supply and drainage, respectively, of a first fluid flowing through the first fluid space.