A working cylinder is provided, comprising at least one disc-like displacer (120) rotatably supported in a cylindrical block (114), which displacer (120) is arranged between two annular flanges (110) extending radially inwards from said block (114) on each sides of said displacer (120) such that said displacer (120) will be arranged in parallel with said flanges (110) upon rotation, wherein at least one of said flanges (110) comprises a plurality of sections including a first section (112a) having a first temperature, a second section (112b) having a second temperature being lower than said first temperature, and two insulating sections (112c, 112d) completely preventing contact between said first section (112a) and said second section (112b), and wherein said displacer (120) comprises a cutout (122) for rotating a volume of working fluid across the sections (112), which cutout is dimensioned such that for every rotational position it does not overlap the first section (112a) and the second section (112b) at the same time.