A unit for use in evaporative cooling includes a first capped frame and a second open frame opposite the first frame. Posts are located between and coupled to the first and second frames. A porous hollow fiber membrane extends around the posts between and coupled to the first and second frames to form an interior volume. The first and second frames are configured for flow of water between them via the membrane. The membrane is configured to transport the water between the first and second frames and to provide for air flow from the interior volume through the membrane for evaporative cooling. The cooling unit can have a rounded square or diamond-shaped cross-sectional shape.