Monobloc assembly for a device which can carry out transfer of heat

A method for transfer of heat between a first and a second fluid, wherein the first and the second fluid circulate respectively on both sides of a thermally conductive wall of a monobloc assembly formed in a single piece, which assembly is arranged in the interior of a device, the monobloc assembly comprising:

• a first, three-dimensional, cellular, thermally conductive structure through which the first fluid can pass;
• at least said wall;
• and
• a second, three-dimensional, cellular, thermally conductive structure through which the second fluid can pass;
• the first, three-dimensional, cellular structure and the second, three-dimensional, cellular structure being situated on both sides of said wall and being integral with said wall;
• such that the transfer of heat is carried out from the first fluid to the second fluid through said wall, and each of the first and second fluids is both under liquid phase and under gaseous phase, with the liquid phase of the first fluid circulating in a direction opposite that of the gaseous phase of the first fluid, and the liquid phase of the second fluid circulating in a direction opposite that of the gaseous phase of the second fluid.