In an embodiment there is provided a fluid separation assembly. The assembly has a hollow fiber bundle with a plurality of hollow fiber membranes. The assembly further has a first tubesheet and a second tubesheet encapsulating respective ends of the hollow fiber bundle, wherein one of the tubesheets has a plurality of radial through openings formed in the tubesheet. The assembly further has a housing surrounding the hollow fiber bundle and the first and second tubesheets, the housing having a feed inlet port, a permeate outlet port, and a non-permeate outlet port. The feed gas, permeate gas, or non-permeate gas are introduced into or removed from the hollow fiber membranes via the plurality of radial through openings formed in the tubesheet, such that the radial through openings of the tubesheet intersect each or substantially each of the hollow fiber membranes.