Abstract: A heat exchanger fin according to the invention has a multiplicity of fins arranged substantially in parallel with the direction of air flow and at least one heat transfer tube to which said fins are connected in a heat conducting relation. A multiplicity of louvers inclined by a small angle to the direction of air flow are formed in said fins.According to this construction, it is possible that the air as a whole can flow substantially straight across the heat exchanger and can strongly collide with all louvers, thereby to ensure a reduced flow resistance encountered by the air flow, as well as improved heat transfer performance of the heat exchanger.

Abstract: A fin assembly for heat exchangers used in air conditioners or the like. The fin assembly is formed from a thin plate material which is bent and wound to have a plurality of alternating turns each of which constitutes a fin. The fin is provided with a multiplicity of louvers cut-out and raised from the major plane thereof. The fins are inclined at an angle .theta. which is 30.degree. or smaller to the direction of flow of the gas entering the fin assembly, while the louvers are inclined at an angle .gamma. which is 20.degree. or smaller to the direction of flow of the gas entering the fin assembly in the direction opposite to the direction of inclination of the fin plates.

Abstract: In a crossed fin-tube type heat exchanger wherein tubes are attached at right angles to a large number of fin elements arranged in parallel with one other, the surfaces of these fin elements are roughened to have an unevenness satisfying a relationR.apprxeq.1/cos.theta.where R is a ratio of the extended, uneven or roughened surface to the flat or smooth surface of the fin element; and .theta. is a contact angle for a liquid droplet in contact with the flat or smooth surface of the fin element.

Abstract: A heat transfer pipe for use in a heat exchanger such as air conditioner, freezer and boiler, wherein grooves are formed in the inner wall surface of the pipe, which are by far finer in size than the grooves that have been provided for the purpose of increasing the heat transfer area in general, and slanting relative to the axis of pipe, to thereby improve the heat transfer rate without increasing the pressure loss caused to the fluid flowing through the pipe.