Abstract: The heat exchanger is composed of a plurality of heat conducting finned discs materially shaped and joined to form concentrically and annularly disposed, circumferential passages for isolated flow of fluid streams in indirect countercurrent, cocurrent, and series heat exchange relationship. The circumferential passages are provided with axial flow apertures for axial transport of fluid streams through the rotary heat exchanger and enable recovery of the mechanical energies transferred to the fluid streams by the rotative surfaces. The energy recovery feature facilitates high speed designs in which large relative velocities are maintained between the fluid streams and rotative surfaces. Enhanced heat transfer with low friction losses is achieved.