Abstract: A heat exchanger, illustratively utilized in a fuel-fired pool heater, circumscribes a burner operative to discharge hot combustion gases outwardly through the heat exchanger. The heat exchanger has a tube portion helically coiled about an axis, with a series of heat transfer fins circumscribing the tube portion and spaced apart along it length. The fins on longitudinally adjacent pairs of coils of the tubing have nested facing edge portions which collectively form a seal area that coils between the tubing portion adjacent coil pairs in axially spaced relationships therewith, the seal area substantially impeding combustion gas flow therethrough in a direction generally transverse to the axis of the heat exchanger. Additionally, the fins have deformed laterally outer portions that define a coiled, circumferentially spaced series of restricted combustion gas outlets in substantial axial alignment with the helically coiled tube portion.

Abstract: A heat exchanger, illustratively utilized in a fuel-fired pool heater, circumscribes a burner operative to discharge hot combustion gases outwardly through the heat exchanger. The heat exchanger has a tube portion helically coiled about an axis, with a series of heat transfer fins circumscribing the tube portion and spaced apart along it length. The fins on longitudinally adjacent pairs of coils of the tubing have nested facing edge portions which collectively form a seal area that coils between the tubing portion adjacent coil pairs in axially spaced relationships therewith, the seal area substantially impeding combustion gas flow therethrough in a direction generally transverse to the axis of the heat exchanger. Additionally, the fins have deformed laterally outer portions that define a coiled, circumferentially spaced series of restricted combustion gas outlets in substantial axial alignment with the helically coiled tube portion.