Abstract: The present invention is directed to a method and apparatus for heat generation or heat exchange in which a primary medium emits heat while passing through an evaporator in which there is a heat-transfer medium which thereby evaporates or boils and thereby increases the pressure of the heat-transfer medium. Once the pressure has increased, it is transferred to a condensor where a secondary medium is heated from the condensation of the heat-transfer medium. The method and device according to the present invention increase the efficiency, particularly when the primary medium is at a low temperature, by intensifying the heat at least in a portion of the evaporator.