Abstract: Hollow fibre membrane modules (1) with a shell-side configuration often comprise a hollow fibre bundle (2) and a perforated hollow internal core (4) inside the bundle. A plug (5) in the core and a baffle (15) in the bundle are typically employed in order to desirably distribute supplied fluid over the bundle for separation purposes. The fluid flow distribution can be improved by incorporating suitable flow distributors (20, 21) within the internal core itself. Such modules are particularly useful for osmotic membrane distillation.