Abstract: A jet-flow heat exchanging device for transferring heat from or to one or more heat transfer surfaces comprises one or more orifice groups, each for directing a heat carrier medium onto the heat transfer surface with at least one of the orifice groups including a main orifice for generating a main jet-stream, and at least two control orifices associated with the main orifice and configured to generate control jet-streams for interacting with the main jet-stream, so as to cause the heat carrier medium of the main jet-stream to swirl.