Numerical Study of Droplets Coalescence in an Oil-Water Separator Zahreddine Hafsi 1(&) , Sami Elaoud 1 , Manoranjan Mishra 2,3 , and Ines Wada 4 1 Laboratory of Applied Fluids Mechanics, Process and Environment Engineering, National Engineering School of Sfax, University of Sfax, Sfax, Tunisia zahreddine.hafsi@enis.tn 2 Department of Mathematics, Indian Institute of Technology Ropar, Rupnagar 140001, Punjab, India 3 Department of Chemical Engineering, Indian Institute of Technology Ropar, Rupnagar 140001, Punjab, India 4 Faculté des Sciences, Département de Chimie, UR13ES63-Chimie Appliquée et Environnement, Boulevard de l’Environnement, Université de Monastir, 5000 Monastir, Tunisia Abstract. Through this paper a numerical modeling of oil-water flow through parallel plates integrated into a rectangular oil-water separator is conducted. Oil droplets of tiny sizes are dispersed in water and rectangular plates are used as coalescing chambers. Results have shown that upgrading a conventional API skimmer by introducing parallel coalescing chambers enhances coalescence of oil droplets by increasing their sizes. Since the buoyancy force that enables oil to float on water surface is proportional to the volume of the submerged oil droplet, droplets of greater sizes are then susceptible to rise to the water surface. Droplets floating on the water surface can be then easily skimmed. COMSOL Multi- physics modeling of two phase flow between two plates of the coalescing chamber has enabled to visualize the coalescence phenomenon and to determine coalesced droplets diameters. Further, the capability of enhancing oil water separation through coalescing chambers was discussed for the studied case. Keywords: Oil water separator Á Droplets coalescence Á Phase field method Á Numerical modeling Á Coalescing chamber 1 Introduction Separation of oil droplets from a volume of water is a key element in numerous industrial applications. This process can be required to remove oil from water in oil and gas productions operations. Indeed, in petroleum industries oil-water separators are of huge importance in order to enhance the productivity, to reduce transport costs and to respect environment policies (Yu et al. 2017). Indeed, for mature oil field, enhanced oil recovery from reservoir wells are mostly performed through injection of water under high pressure (Arnold et al. 2004). Then, the recovered crude oil presents water dro- plets that need to be removed through oil-water separation before shipping crude oil for © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2020 M. Kharrat et al. (Eds.): ICAMEM 2019, LNME, pp. 449–454, 2020. https://doi.org/10.1007/978-3-030-52071-7_61