An internal channel in a metal body for use in applications where internal fluid flow within a metal body is desired, as in a heat exchanger. The internal channel is formed in the metal body by frictionally stirring with a pin plunged into the metal body, and traversing the metal body with the pin....http://www.google.se/patents/US7354657?utm_source=gb-gplus-sharePatent US7354657 - Integral channels in metal components and fabrication thereof
