Abstract: A heat element comprises three parallel tubes (11), which to a considerable part of their lengths are cast into a body (12) of a metal having good heat transferring properties and having a rectangular cross section. Within the portion of the tubes (11) enclosed by the body, the tubes are externally provided with helical rills (15), running in opposite directions, and are interconnected by tack welding outside the expected body, before the casting operation. The side faces of the body (12) are subdivided by means of transverse and longitudinal grooves (18, 19a, 19b), so heat transferring enlarging members (17) as truncated pyramids are formed. Members in adjacent rows are displaced sidewardly, so a zig zag pattern is formed, which causes turbulence in the second heat transporting medium flowing along the body.