A plate (20) for a heat transfer tube (4) made from a metal sheet includes a peripheral outer wall (10) and having at least one first cavity (24) and least one second cavity (26) respectively formed in the metal sheet. The first cavity (24) is in contact with the peripheral outer wall (10) and the second cavity (26) is arranged at a distance from the outer wall (10). A heat transfer tube (4) of a heat exchanger (1) includes a pair of such plates (20) and a heat exchanger (1) includes a plurality of such tubes (4).