Experimental assessment of flow distributors for falling-films over horizontal tube banks

•Eight flow distributors compared for falling-film heat and mass exchangers.•Wide range of Reynolds number investigated to observe flow regime transition.•Flow features and maldistribution characterized for different designs.•Box-based distributor designs outperformed the tube-based distributor. Flow distributors are designed to evenly spread fluid along the length of horizontal tube banks used in falling-film heat and mass transfer components. This study comparatively assesses the performance of eight distributor designs described in previous studies under uniform conditions: water at 20 °C and atmospheric pressure with a distribution length of 203 mm over a film Reynolds number range of 12–495. Flow regimes from the droplet to sheet regime were observed, and the levels of maldistribution were quantified using a simple segmented collection system. Droplet and jet characteristics were measured using image analysis of high-speed video, with droplet volumes ranging from 20 mm3 to 540 mm3 and jet diameters ranging from 1.2 mm to 4 mm. Overall, the box-based distributor designs outperformed the tube-based distributors, but maldistribution was significant (>50%) for some flow rates in all the tested designs.