Patent ID: 7600316

Claim:
A method of manufacturing a heat exchanger, the heat exchanger having a hot end and a cold end, the hot and cold ends of the heat exchanger being arranged at the axial ends of the heat exchanger, comprising forming a first sheet, forming a second sheet and forming at least one additional sheet, winding the first and second sheets around an axis, each sheet having hot and cold edges at the hot and cold ends respectively of the heat exchanger, joining the hot and cold edges of the first sheet to the hot and cold edges respectively of the second sheet, joining an end of the first sheet 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, joining the at least one additional sheet 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, winding the at least one additional sheet around the first and second sheets about the axis, joining the end of the at least one additional sheet 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.