The disclosure relates to devices and methods for extracorporeal conditioning of blood. Extracorporeal blood oxygenators and blood oxygenator components, such as conditioning modules, are described. An extracorporeal blood oxygenator includes a conditioning module having an external frame, an inlet cover, an outlet cover, and an internal chamber. A fiber assembly is disposed within the internal chamber and a potting material on the fiber assembly creates a circumferential seal that defines a passageway through the fiber assembly having a substantially circular cross-sectional shape. A fluid inlet is in fluid communication with the passageway, has a lumen that extends along an axis that is substantially perpendicular to the fiber assembly, and has an internal curvilinear surface adjacent the fiber assembly. A fluid outlet on the opposite side of the fiber assembly also has a lumen that extends along an axis that is substantially perpendicular to the fiber assembly.
