Abstract: The invention provides a heat exchanger mat, comprising a twin-duct manifold having a duct member comprised of an inlet duct and an outlet duct, a tube-socket member fixedly and fluid-tightly attached to the duct member, and a return manifold having a deflector member and a tube-socket member fixedly and fluid-tightly attached to one another. The mat also includes a plurality of tubes for circulation of a heat-exchanging liquid medium, each tube fixedly and fluid-tightly joined at one of its ends to the tube-socket member of the twin-duct manifold and at the other one of its ends to the tube-socket member of the return manifold. One end of each odd-numbered one of the tubes communicates via at least one aperture with one of the twin ducts, and one end of each even-numbered one of the tubes communicates via at least one other aperture with the other one of the twin ducts, and the other ends of all of the tubes communicate with the return manifold.

Abstract: The invention provides a base unit for a cross flow, tube and shell type heat exchanger comprising a substantially flat double frame consisting of an inner frame member delimiting an opening defining an element of a shell flow space, an outer frame member surrounding at least a portion of the inner member at a distance, which distance defines an element of a header flow space, at least two partition walls connecting the inner and the outer frame members and dividing the header element into an inlet header element and an outlet header element, the inlet and the outlet element being thereby separated from each other.