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.

Abstract: A method of producing a heat exchanger in which a fin block of porous metal and fin plates connected to the fin block are unitarily secured to a serpentine heat-transmitting pipe. A plurality of fin molds produced with the use of plastic patterns formed therein with continuous, three-dimensional cavities are assembled with the heat-transmitting pipe shaped beforehand into a serpentine form in such a manner that the fin molds enclose the heat-transmitting pipe with suitable spacing intervals defined between the fin molds themselves and between the fin molds and the heat-transmitting pipe. Molten metal of high thermal conductivity is cast into continuous cavities in the fin molds and into the spacing intervals, and the material of the fin molds is removed after the molten metal has solidified.