Device for treating fluid

A device for treating fluid, comprising:

• a first element assembly having first and second tubular elements with the second tubular element being inside the first tubular element, the first tubular element being in a fluid flow direction of and facing an inflow side of the element assembly and the second tubular element being in the fluid flow direction of and facing an outflow side of the element assembly such that fluid flows in succession through the first and second tubular elements from the inflow side to the outflow side during fluid treatment;
• an annular flow chamber between the first and second tubular elements, the annular flow chamber being free of other filter components;
• a first material of the first tubular element having a continuously repeating shape only of uniform first element folds of an equal fold height in radial directions thereof;
• and
• a second material of the second tubular element having a continuously repeating shape of non-uniform second element folds with shorter and longer folds heights in radial directions thereof arranged in an alternating succession forming a waveform of constant frequency and different amplitudes and spaced at distances forming channel guides blocked at deflection points of the second element folds, the defection points having radial offsets, the shorter fold heights being about two-thirds of the longer fold heights.