Abstract: A heat-exchanger for fluids is designed with an outer cylindrical casing and, inside the same, a plurality of coaxial heat-exchange surfaces forming axial flow passageways for fluids therebetween, with two ends each bearing a connection-box for the fluid inlets and outlets. This connection-box is connected to the outer peripheral heat-exchange surface and includes partitions extending from the axis to the periphery and engaging the edges of the heat-exchange surfaces. Obturators join pairs of edges of successive heat-exchange surfaces whereby each end of the succession of heat-exchange surfaces offers annular passageway portions and annular obturated portions.