Heat exchanger for air conditioning system

Claim 1

A heat exchanger for an air conditioning system comprising: a plurality of heat transfer tubes having their respective axes arranged substantially parallel to one another; a multiplicity of spine fins secured to an outer surface of each of said heat transfer tubes and extending radially outwardly thereof; a refrigerant flow passage defined inside each of said heat transfer tubes; air passages each defined by the adjacent spine fins secured on the outer surface of each of said heat transfer tubes; said spine fins being formed such that a multiplicity of parallel cuts are formed at small pitch in each of fin-base plates, except for their respective base portions, to form a multiplicity of legs, the respective base portions of said fin-base plates being wound around and secured to the outer surfaces of the respective heat transfer tubes so that said legs extend radially outwardly from said heat transfer tubes; said spine fins being of a constructional form such that their coefficient of heat transfer to and from the air is over 1.2 times that of flat fins; each of said heat transfer tubes being formed on the inner wall surface thereof with a multiplicity of spiral grooves; said heat transfer tubes each having an outer diameter in the range between 6 and 16 mm; said spiral grooves formed on the inner wall surface of each of said heat transfer tubes having a depth in the range between 0.1 and 0.6 mm and a pitch in the range between 0.2 and 0.6 mm; the respective spiral ridges formed by the adjacent twos of said spiral grooves each having a sharp-apex, V-shaped cross-section and a vertical angle in the range between 50° and 100°; the spiral grooves formed on the inner wall surface of each of said heat transfer tubes each having a helical angle with respect to the axis of the tube in the range between 16° and 35°; and said heat exchanger being incorporated in a refrigerant circulating cycle of a heat-pump type so as to function selectively as a condenser and an evaporator therein.