Patent ID: 7918268

Claim:
A heat exchanger having a hot end and a cold end the hot and cold ends of the heat exchanger being arranged at axial ends of the heat exchanger, the heat exchanger comprising a first sheet, a second sheet and at least one additional sheet the first and second sheets being wound around an axis, each sheet having hot and cold edges at the hot and cold ends respectively of the heat exchanger, the hot and cold edges of the first sheet being joined to the hot and cold edges respectively of the second sheet, an end of the first sheet being joined to the second sheet by an axially extending join at a position spaced at least one turn away from an end of the second sheet the at least one additional sheet being joined to the end of the second sheet, the at least one additional sheet being thicker and wider than the first and second sheets such that at least one of the hot and cold edges of the at least one additional sheet extend beyond the hot and cold edges of the first and second sheets, the at least one additional sheet being wound around the first and second sheets about the axis, the end of the at least one additional sheet being joined to the at least one additional sheet by an axially extending join, wherein the at least one additional sheet comprises a plurality of sheets, adjacent additional sheets have different thicknesses and/or widths.