The invention relates to a heat exchanger for transferring heat from a heat source to a fluid flowing in a first channel, comprising an inner wall made of heat conducting material, surrounding the heat source, being thermally connected with the heat source and having the shape of a surface of revolution, a outer wall concentric to the inner wall, wherein the distance between both walls is substantially constant and a first conduit comprising the first channel, extending between both walls and being in thermal contact with the inner wall. Preferably said tube has been deformed by subjecting the inner side of the tube to a pressure sufficiently high to cause such a permanent deforming of the tube that it is clamped between the inner and outer walls.