The heat exchanger includes a cool conduit (2,3), a hot conduit (4) and a heat exchanging element (1) arranged between the cool conduit (2,3) and the hot conduit (4). The heat exchanger also includes at least one further conduit (3,2) arranged next to the cool conduit (2,3) or to the hot conduit (4) on a same side of the heat exchanging element (1) as said respective cool or hot conduit. The further conduit is separated from the respective cool or hot conduit by a separator (5) that includes two separating elements (51,52) arranged at a distance to each other and forming a cavity (53) between the two separating elements (51,52). The separator restricts a fluid flow into or in the cavity (53) such as to limit a heat exchange between the further conduit (3,2) and the respective cool or hot conduit on the same side of the heat exchanging element (1).