Water-in-oil dispersion separation in the petrochemical industries is important due to safety, ecological and economic reasons. In this work, nanofiber mat filters are fabricated in flat sheet and cylindrical geometries and tested for separation of water dispersions in diesel fuel. The nanofiber mats are formed by electrospinning. Due to the fiber size, pore size, and material composition, the nanofiber mat surfaces are superhydrophobic which aids in the separation of the dispersion. The superhydrophobic surfaces are oleophilic due to their low surface energy. The surface roughness of the nanofiber membranes enhance the hydrophobicity while the oleophilicity allows the non-aqueous phase to easily flow through the nanofiber membrane. The cylindrical nanofiber filters performed with separation efficiency as high as 98% on a total mass basis for water drops in the range of 7-50 mu m in ultra low sulfur diesel fuel (ULSD) with a face velocity of 1.55 cm/min. The flat filter geometry performed at about 92% separation efficiency at a similar face velocity. This work shows practical water-diesel separation filters can be constructed in tubular geometries. (c) 2012 Elsevier B.V. All rights reserved.