Patent ID: 7516719

Claim:
A steam generator, comprising: a combustion chamber having funnel shaped side walls, a bottom area, and a top area; a plurality of steam generator pipes, connected together by fins, at least one of the pipes having a diameter at the bottom area that is different than a diameter at the top area; an encircling wall arranged between the bottom and top areas and above the funnel shaped side walls formed from the plurality of steam generator pipes; a flow medium that flows through the steam generator pipes; a center axis A, positioned at the center of the encircling wall and extending parallel to the direction of flow of the flow medium, wherein the outermost steam generator pipes which are the greatest distance from the center axis A are arranged over the entire height of the funnel shaped side walls both with non-reduced pipe diameter and a non-reduced fin width, wherein inner most steam generator pipes with the smallest distance from the center axis A have a reduced pipe diameter and reduced fin width, and steam generator pipes arranged between the outermost and the innermost steam generator pipes form a transition having a first section with reduced pipe diameter and reduced fin width and a second section with non-reduced pipe diameter and non-reduced fin width.