Abstract: In a cross finned tube heat exchanger including a multiplicity of side-by-side fin plates, and a plurality of heat transfer tubes extending through the fin plates at least in one row to provide a serpentine flow passage for a heat transfer medium which exchanges heat with another heat transfer medium flowing across the surfaces of the fin plates, a multiplicity of stepped louvers are formed on the wall of each fin plate between the adjacent heat transfer tubes of the same row. The stepped louvers each extending in a direction at right angles to the direction of air flow across the surfaces of the fin plates include at least one tilting rise wall and may differ from one another in shape depending on their positions. The stepped louvers on each fin plate may be arranged in the form of waves or uniform in height with respect to the direction in which each fin plate extends. The adjacent stepped louvers have edges varying in vertical positions.

Abstract: A cross-fin tube type heat exchanger having a large number of parallel fins and a plurality of heat transfer tubes extended through and fixed to the fins, so that heat may be exchanged between a first heat exchanging medium flowing through the heat transfer tubes and a second heat exchanging medium flowing along the surfaces of the fin, across the walls of the heat transfer tubes and through the fins. In the portions of each fin between adjacent heat transfer tubes of the same row, formed are a number of slits perpendicular to the direction of flow of the second heat exchanging medium. Each elongated section defined between each pair of adjacent slits is bent along its breadthwise bisector line and is raised in the form of a bridge to constitute an upwardly convexed louver element. The upwardly convexed louver element may have a cross section with an obtuse apex angle, or may have an arcuate cross section.