A method for transporting a viscous fluid through a heat exchanger line that includes transporting a viscous fluid through a connecting piece with an excess pressure release component, where the excess pressure relief component separates an interior of the connecting piece from a discharge line in the connecting piece, and is fixed to an edge of the discharge line, mixing a fluid flow in a region of the excess pressure relief component using a mixing element disposed in the interior of the connecting piece and causing the excess pressure release component to release at least a portion of the fluid through the discharge line when the pressure of the fluid is equal to or greater than a preset excess pressure.