Abstract: The invention relates to a heat-transfer tube, in particular an evaporator tube, with fins circumferentially extending on the shellside, which fins are shaped to essentially closed-off channels. The channels are open to the outside through pores with at least two variable sizes. In order to improve the evaporation characteristics, the invention provides advantageous regions for the ratio of the pore sizes and the ratio of the number of pores.

Abstract: A metallic heat transfer tube, in particular for the evaporation of liquids from pure substances or mixtures on the outside of the tube. Fins are integrally formed on the outside of the tube. Recesses are arranged in the area of the base of the primary grooves and extend between the fins. The recesses are in the form of re-entrant secondary grooves. The mechanical stability of the tube is not negatively influenced because material is primarily removed from the fin flanks toward the base of the groove so that the re-entrant secondary grooves are radially open.

Abstract: The invention relates to a heat-transfer tube, in particular an evaporator tube, with fins circumferentially extending on the shellside, which fins are shaped to essentially closed-off channels. The channels are open to the outside through pores with at least two variable sizes. In order to improve the evaporation characteristics, the invention provides advantageous regions for the ratio of the pore sizes and the ratio of the number of pores.

Abstract: The invention relates to heat-exchanger tubes structured on both inner and outer sides with excellent heat-transfer characteristics, which have recesses on the outside and ribs with specific dimensions on the inside. The structuring tools utilized for the various method modifications are adjusted in such a manner that they are not only able to create aligned, continuous grooves and non-aligned, spaced apart recesses but also secondary structures. The heat-exchanger tubes provided preferably with smooth end sections and smooth intermediate sections are utilized in particular in shell and tube heat-exchangers.

Abstract: A process for producing a heat exchanger tube (1) with a highly porous surface structure, in particular for evaporating liquids from pure substances or mixtures on the outside of the tube. The process starts from a rolling operation, by means of which helical fins (2) are produced on the outside of the tube, which fins, in turn, are deformed in a plurality of compression steps by means of gearwheel-like compression wheels (6, 7) in such a manner that the projections (12a, 12b) formed in each case form a cover (3a) for the passages (3) which are situated between the fins (2). The high level of porosity is achieved as a result of the remaining pores (13) and/or slots (14).