A heat exchanger assembly comprising: a first single-piece manifold; a second single-piece manifold spaced from and parallel to said first single-piece manifold; each of said first and second single-piece manifolds having a tubular wall defining a flow path; a plurality of flow tubes extending in parallel between said first and second single-piece manifolds (22, 24) and in fluid communication with said flow paths; an insert having a distribution surface and slidably disposed in said flow path of said first single-piece manifold to establish a distribution chamber within said first single-piece manifold; and a series of orifices defined in said distribution surface of said insert and in fluid communication with said flow path and said distribution chamber for uniformly distributing a heat exchange fluid between said flow path and said flow tubes, wherein said first single-piece manifold includes a first tube end and a second tube end spaced from said first tube end, said flow path extends between said tube ends (30, 32) of said first single-piece manifold, wherein said heat exchanger assembly further comprises an axis (A-A) extending centrally within said flow path of said first single-piece manifold, and a center plane intersecting said axis (A-A) between said tubular wall of said first single-piece manifold, wherein said insert comprises a pair of side flanges extending opposite each other from said distribution surface of said insert toward and along said tubular wall of said first single-piece manifold for orienting and securing said insert in said flow path of said first single-piece manifold, and wherein said tubular wall of said first single-piece manifold defines at least two indentations with each indentation spaced from and opposite the other with said side flanges mechanically engaging said at least two indentations for orienting and securing said insert in said flow path of said first single-piece manifold, characterized in that said side flanges extend from said distribution surface of said insert in the circumferential direction of the tubular wall toward said center plane such that edges of said side flanges mechanically engage said at least two indentations in the circumferential direction. a first single-piece manifold; a second single-piece manifold spaced from and parallel to said first single-piece manifold; each of said first and second single-piece manifolds having a tubular wall defining a flow path; a plurality of flow tubes extending in parallel between said first and second single-piece manifolds (22, 24) and in fluid communication with said flow paths; an insert having a distribution surface and slidably disposed in said flow path of said first single-piece manifold to establish a distribution chamber within said first single-piece manifold; and a series of orifices defined in said distribution surface of said insert and in fluid communication with said flow path and said distribution chamber for uniformly distributing a heat exchange fluid between said flow path and said flow tubes, wherein said first single-piece manifold includes a first tube end and a second tube end spaced from said first tube end, said flow path extends between said tube ends (30, 32) of said first single-piece manifold, wherein said heat exchanger assembly further comprises an axis (A-A) extending centrally within said flow path of said first single-piece manifold, and a center plane intersecting said axis (A-A) between said tubular wall of said first single-piece manifold, wherein said insert comprises a pair of side flanges extending opposite each other from said distribution surface of said insert toward and along said tubular wall of said first single-piece manifold for orienting and securing said insert in said flow path of said first single-piece manifold, and wherein said tubular wall of said first single-piece manifold defines at least two indentations with each indentation spaced from and opposite the other with said side flanges mechanically engaging said at least two indentations for orienting and securing said insert in said flow path of said first single-piece manifold, characterized in that said side flanges extend from said distribution surface of said insert in the circumferential direction of the tubular wall toward said center plane such that edges of said side flanges mechanically engage said at least two indentations in the circumferential direction.