Heat exchanger assemblies including turning vanes are taught herein. In preferred embodiments, the heat exchanger assembly comprises: an inlet duct; a heat exchanger coupled to the inlet duct and a plurality of turning vanes coupled to the heat exchanger and protruding into the inlet duct. The intake plane of the heat exchanger is at an angle between 0 degrees and 90 degrees to the primary flow direction of the inlet duct. The plurality of turning vanes comprise: a straight leading edge of length L that is parallel to the primary flow direction of the inlet duct; a convex lower surface that transitions a bottom of the leading edge to an upper wall of a lower channel of the heat exchanger; and a concave upper surface that transitions a distal point of the turning vane to a second channel of the heat exchanger.