Patent ID: 8622030

Claim:
A spiral heat exchanger enclosed in a metal shell having a circular cylindric bottom for producing heating hot water, sanitary hot water or heating hot water for condensation applications, said spiral heat exchanger comprising a first thermally conductive material outer duct having a pear outer contour, a secondary fluid being caused to flow inside said first outer duct to provide two circulating circuits with different characteristics and through one of said circulating circuits heating water being conveyed and through the outer of said circulating circuits sanitary water being conveyed, a second thermally conductive material inner duct arranged in said outer duct, said inner duct having a circular shape or elliptic shape or polygonal shape or other cross sectional shape, said pear outer contour of said first outer duct being defined by joining two circumferences of different diameters, said circumferences being spaced from one another by a constant or variable radius junction contour portion, said first and second ducts being spiral wound on a diameter substantially larger than a size of said outer duct thereby providing a hollow cylinder, characterized in that a primary fluid is caused to expand within said hollow cylinder, to achieve a gaseous status at a high temperature, said primary fluid then flowing to the outside through gaps between said spiral coil turns, thereby releasing heat to the secondary fluid or secondary fluids circulating inside said ducts.