Heat exchanger, in particular for a condensation boiler

A heat exchanger for a condensation boiler, comprising a casing in which there is housed a helical flow conduit for a liquid, made with a pipe of extruded thermally conductive material, in particular aluminium or an alloy thereof, provided with a pair of facing and essentially mutually parallel fins, which extend from a portion of a radially outer surface of the pipe, said pipe being helically wound about a longitudinal axis such as to form a sequence of adjacent turns separated by interspaces through which, during use, hot gases, in particular combustion fumes, flow;

• said fins extending helically, towards the outside with respect to the axis of said helical conduit;
• wherein said facing fins have respective pluralities of through-openings which in at least some consecutive turns of the helical conduit interconnect the region comprised between them and the interspaces defined with respect to the adjacent turns, defining flow paths through said fins, outside said helical conduit, for the hot gases which during use pass through said interspaces;
• and
• wherein in each of at least some consecutive turns of the helical conduit said fins have, viewed in cross-section transverse to the axis of the pipe;
• a proximal portion which extends from the pipe away from the longitudinal axis of the said helical conduit, and
• a distal portion which extends longitudinally on the opposite side to the facing fin of the same turn, said distal portion being substantially in contact with the corresponding distal portion of the facing fin of the adjacent turn.