Abstract: The invention relates to an improved fin and tube type heat exchanger wherein thin, heat-conducting fins act as a secondary heat-exchange surface for a heat-conducting medium flowing through the tubes. The thin fin plates substantially lie in a plane perpendicular to the air flow and have angled louvers formed therein. The angled louvers have a short leg and a long leg, with the short leg preferably in the fin plane with the long leg bent therefrom. The unequal length legs permit a larger condensate gap between the trailing edge of one louver and the leading edge of the next louver. With the combination of an angled louver plus the short leg lying in the fin plane, a substantially strong fin is provided even with a thin fin plate. The combination of the short leg lying in the direction of air flow, with the longer leg being inclined thereto, allows a high heat transfer coefficient at the leading edge, while the angled portion behind the leading edge generates a turbulent flow to reduce boundary layer growth.

Abstract: A core for use in a heat exchanger including a tube of heat conductive material and a tape of heat conductive material wrapped around the tube. The tape has a base extending completely about the periphery of the tube in abutment therewith and a plurality of spines extending generally radially from the base in fanned relation over an arc length in the range of about 180.degree.-220.degree.. The tube is essentially free of the spines along a longitudinally extending area having an arc length in the range of approximately 180.degree.-140.degree..

Abstract: A method of making a segmented externally finned tube with at least one fin free area for use in a heat exchanger. The method includes the steps of providing a tape of thermally conductive material with spaced reliefs along one longitudinal edge thereof and slitting the tape from that edge partially across its length between the reliefs. The slit portions of the tape are bent to form an angle with respect to the remainder of the tape which is then used to helically wrap a thermally conductive tube. The area of the reliefs provide fin free areas.

Abstract: This invention relates to a compact high efficiency furnace having a cylindrical combustion chamber and a fin and tube type heat exchanger substantially parallel, transverse to the furnace air flow, and closely spaced in the air flow direction with no other major heat exchange being utilized. Condensation of fluids from the combustion gases occurs at the fin and tube type heat exchanger, whereby a high efficiency furnace results. The fins and tubes of the heat exchanger are of different materials, requiring that the combustion gas temperature at the heat exchanger inlet be limited.