Abstract: A heat exchanger tube for effecting a heat exchange between a fluid inside the heat exchanger tube and another fluid flowing outside the heat exchanger tube, which is provided with a first kind of spiral grooves and a second kind of spiral grooves, each being formed on an outer surface of the heat exchanger tube. The twisting direction of the first kind of spiral grooves in relative to the axis of the heat exchanger tube is the same as that of the second kind of spiral grooves but differs in helix angle from each other with helix angles of the first kind of spiral grooves and the second kind of spiral grooves falling within the range of 3.degree. to 80.degree. in relative to the axis of the heat exchanger tube.

Abstract: A ceramic recuperator (18) for a recuperator burner (1) is provided, in its heat exchanger region, with a plurality of radially inward- and outward-extending teeth. On the otherwise hollow-cylindrical recuperator (18), the teeth (19) are arranged in groups, e.g., in rings; the teeth of one ring are each offset from the teeth of an adjacent ring. Alternatively, it is possible to arrange the teeth on a single- or multi-start helical line. The recuperator can be produced economically by the slip-casting method.

Abstract: The invention relates to a metallic heat-exchanger tube (1) with fins (2) which annularly or helically extend or rather extend in axial direction on the outside of the tube for condensing of vapor from pure substances or mixtures on the outside of the tube. To improve the condensation performance by effecting a thinning of a liquid film, the invention includes a making of the fins so that they have a constant fin height H throughout, with the fin flanks (4) being structured by spaced-apart depressions.

Abstract: The object of the present invention is to offer a heat transfer tube having a grooved inner surface, wherein the side edges of the board material do not form a waved shape and cracks do not form during tube expansion. In order to achieve this object, the grooved-inner-surface heat transfer tube of the present invention has a metallic tube with an inner circumferential surface, on which are formed a weld portion which extends in an axial direction of this metallic tube, a pair of projecting strip portions formed parallel to and separate from this weld portion, and a plurality of fins formed in an area between these projecting strip portions. The fins are formed with a constant angle with respect to the tube axis, and the ends of these fins are connected with the projecting strip portions. The thickness of the metallic tube within the grooves formed between the fins is made to increase in approaching the weld portion within an area surrounding the weld portion wherein the central angle is within 30.degree..

Abstract: A heat exchanger tube having a smooth outer surface and a textured inner surface. The inner surface is composed of parallel ribs which run at an angle deviating from 90.degree. relative to the longitudinal axis of the exchanger tube. The ribs further have inclined flanks, channels delimited on the sides by the ribs, and depressions formed in the ribs, which may run crosswise at a distance from the bottom of the channels. The depressions are formed so as to follow a sine-shaped progression, in longitudinal cross-section of the ribs, which are provided with a surface micro-roughness and which are rounded on the top. The center longitudinal planes of the depressions are arranged at an angle deviating from 90.degree. relative to the longitudinal axis of the exchanger tube. The opposite flanks of adjacent ribs are connected by means of rounded channel bottoms. The micro-roughness of the rib surfaces is produced by corundum blasting or laser beams.

Abstract: Heat exchanger has a first surface on which a first fluid flows and a second surface on which a second fluid flows, at least one of the first and second surfaces has at least two projections and a bottom therebetween, and an imaginary line on the bottom along a shortest distance between the projections adjacent to each other is prevented from extending along an imaginary face substantially parallel to a main flow direction of one of the first and second fluids which flows over the bottom.