As part of the AddVerKon project, which began in July 2024, pressure-resistant compact evaporators and condensers are to be developed and tested experimentally. The operating pressure and temperature should be up to 63 bar_op and 900°C. In order to achieve these goals, the project is divided into three phases. In the first phase, theoretical approaches and numerical calculations will be used to develop heat-transferring segments with modified surfaces that are characterized by the corresponding mechanical stability and high thermal performance. Due to the high targeted pressures, it is necessary to take into account the design in accordance with the Pressure Equipment Directive as well as certification of the manufacturing process with the material and the equipment by the TÜV. To date, various basic structures have been developed and selected for the structured surfaces. These selected structures have been varied in various parameters such as size and height. The first additively manufactured samples are used to assess the production quality and surface wettability. The first heat exchanger segments will be developed on the basis of these samples. In the second phase, these segments will be investigated experimentally in order to test their strength and heat-transfer properties. This requires the development and construction of an appropriate test rig. In the final phase of the project, the heat-transferring segments are scaled/combined into so-called demonstrators. For this purpose, numerical calculations of the flow uniform distribution and a subsequent experimental investigation are carried out. These findings will ultimately be used to provide the design documents for such compact evaporators and condensers, which will enable the future user-specific design of these devices.