Using Dimensional Analysis for Development of Empirical Correlations for Estimation of Liquid Holdup and Drop Size in Rotating Disc Contactor K. Swetha Saraswathi and P. R. Naren 1 Introduction Liquid–liquid extraction (LLE) involves preferential separation of components from the liquid feed using another liquid phase as solvent. The rotating disc contactor (RDC) is particularly used for liquid–liquid systems with medium to low interfacial tension. It consists of a vertical column equipped with a series of equally spaced stators and a shaft [1]. Rotor discs are mounted on a shaft driven by a motor. This induces agitation in the column. Further, rotation of the discs creates high shear in the liquid and thus leads to increased interfacial area. The rotor discs accelerate the flow and the stator rings decelerates the flow. A counter-current flow of the two phases is maintained in the contactor. This contactor has many advantages: simplicity in construction, low power consumption, high throughput, operational flexibility, lower cost for solvent inven- tory and maintenance [2]. The performance of the RDC is mainly attributed to the breaking down the light phase droplets and therefore increasing the column performance. The mass transfer efficiency of the commercial RDCs is low due to its structural limitations, high axial back-mixing and entrainment of small droplets. Rotating disc contactor has drawn considerable attention as extraction equipment in deacidification of vegetable oils [3], wastewater treatment and downstream opera- tions to separate inhibitory fermentation. It is also widely used in the petrochemical, chemical, hydrometallurgy [4] and biochemical industries for its low investment and less maintenance [5]. K. S. Saraswathi Chemical Engineering (Integ.), SASTRA Deemed To Be University, Tamil Nadu, Thanjavur 613401, India P. R. Naren (B ) Chemical Engineering, School of Chemical and Biotechnology, SASTRA Deemed To Be University, Tamil Nadu, Thanjavur 613401, India e-mail: prnaren@scbt.sastra.edu © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 T. Prabu et al. (eds.), Fluid Mechanics and Fluid Power, Lecture Notes in Mechanical Engineering, https://doi.org/10.1007/978-981-16-0698-4_15 137