Abstract: A method and equipment for heat-of-vaporization transfer in a heat exchanger, using steam bubbles. To achieve higher transfers at slight overheating, and with a very simple design, steam bubbles are introduced into evaporation chambers formed between heat exchanger walls, said bubbles then being deformed by said walls and rising in-between them. As they rise, the steam bubbles form a thin liquid film between themselves and the heat exchanger walls, with constrained convection inside the film. As a result excellent local conditions for heat conduction are achieved. Moreover the liquid is well mixed and by evaporation into the bubble it is cooled as far as the immediate vicinity of the heat exchanger walls.