Abstract: A finned heat exchanger characterized by disposing main plural raised portions 24a, 24b, 24c only on one side of the surfaces of fins 11, between heat transfer tubes 13 adjacent in the transverse direction, defining the width Wf of the raised portions 24a, 24b, 24c in the principal direction of air stream at about ⅓ of the distance Wb between adjacent raised portions in the principal direction of an air stream, and disposing grooved insulating means such as slits 31, slots 32, or raised portions 33c, 35, 37 in the portion of the fins where there is a temperature difference between fluids flowing in adjacent heat transfer tubes 13 in the principal direction of air stream, said insulating means disposed on the surface of the fins 11 near the middle of the fins between adjacent heat transfer tubes 13 in the principal direction of the air stream to suppress the conduction of heat through the fins caused by fluids flowing in adjacent heat transfer tubes in the principal direction of air stream, and to effec

Abstract: A finned heat exchanger includes a plurality of elongated fins which are arranged at a predetermined interval in parallel with one another such that air flows between neighboring ones of the fins in a predetermined direction. A plurality of heat transfer tubes which contain refrigerant passing therethrough are orthogonally inserted through the fins so as to be arranged in a plurality of columns on the fins. When the finned heat exchanger is operated for condensation, the heat transfer tubes are provided in two paths in the vicinity of an inlet for the refrigerant and are provided in one path in the vicinity of an outlet for the refrigerant, such that the heat transfer tubes of the one path occupy about 5 to 30% of all the heat transfer tubes.

Abstract: An apparatus having a refrigeration cycle using a flammable refrigerant, comprises an oil-free compressor, a condenser, an expansion device and an evaporator, wherein an amount of lubricant in the oil-free compressor is equal to or smaller than 3 cc. With this structure, the charging amount of the flammable refrigerant into the refrigeration cycle can be reduced, and the safety of the apparatus having a refrigeration cycle can be enhanced.

Abstract: A groove configuration, formed on an inside wall of a heat exchanger tube, has a cross-sectional area varying in the longitudinal direction of the heat exchanger tube. An increased rate of the cross-sectional area is differentiated from a decreased rate of the cross-sectional area by changing the height or top width of a protruding portion, or the depth or bottom width of a recessed portion.

Abstract: The fin-tube heat exchanger includes a group of fins arranged parallel to one another at predetermined intervals; cylindrical fin collars formed on each fin at a predetermined column pitch and a predetermined row pitch; and heat transfer tubes extending through the respective fin collars and secured thereto in intimate contact therewith. Seat portions are formed on each fin around the fin collars. A curved protuberance of a generally angular cross-section is formed on the fin adjacent to an outer periphery of each of the seat portions, which has a ridge line of an arcuate or circular shape arranged in concentric relation to the associated fin collar. A plurality of straight protuberances of a generally angular cross-section are formed on each fin adjacent to outer peripheries of the respective seat portions between any two adjacent rows of the fin collars. With this structure, heat transfer performance is improved by a turbulence promoting effect of the straight protuberances.

Abstract: A plate fin heat exchanger has a group of fins arranged at predetermined intervals so that an air current flows between the respective fins and a group of tubes respectively inserted into and joined to the cylindrical fin collars which are formed in the fin group with a predetermined longitudinal pitch and lateral pitch. Elliptical seats each having a longitudinally extending short axis are respectively provided around the fin collars on the surface of each of the fins, and seat-side ridge portions are respectively formed along the outer peripheries of the seats. A plurality of fin-side ridge portions, each having a longitudinally linearly extending ridge and substantially the same height as that of each of the seat-side ridge portions, are formed in each line of the fin collars outside the seat-side ridge portions on each of the fins. The turbulence promoting effect of the fin-side ridge portions, each having a longitudinally linearly extending ridge, improves the heat transfer efficiency.