Modelling of a Micro-Extractor

To evaluate the performance of a two-phase separator (gas-liquid or liquid-liquid) the mass transfer coeflicient or the extraction efficiency need to be known. A number of models have been developed for gas-Uquid systems, which estimate the mass transfer coefficient in the continuous liquid phase. In these models the individual contributions of the caps of the plugs and of the fully developed film separating the plugs from the channel wall are estimated. A study 

Based on the kL.eim suggested by van Baten and Krishna (2004), Vandu et al. (2005) developed a correlation (Eq. 7.1.2), with a fitted parameter C based on their experimental data of air absorption in water. 

An empirical correlation for liquid-liquid plug flow was developed by Kahsid et al. (2010) based on dimensional analysis in PTFE capillaries. 

In this chapter experimental mass transfer coefficients are compared against these three predictive models. In addition, a numerical finite element model is developed which solves for the hydrodynamics and mass transfer in both phases and the predictions on amount of extraction are compared against the experimental findings. This model allows parameters, such as film thickness, plug length, length of unit cell, and flow rates to be investigated. 

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