Influence of Capillary Number on the droplet Shape, Film Thickness, and Pressure Drop in a Liquid-Liquid Taylor Flow inside a Microcapillary

S V B Vivekanand,S Chandrasekhar,V R K Raju

doi:10.33889/ijmems.2019.4.6-111

S V B Vivekanand, S Chandrasekhar + Show 1 more

Open Access

https://doi.org/10.33889/ijmems.2019.4.6-111

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Abstract

Numerical analysis of a two-dimensional, axisymmetric, incompressible, laminar liquid-liquid Taylor flow inside a vertical circular microchannel is carried out in the present study. The focus is laid on fluid flow characteristics in the slug flow regime. Although many researchers have performed numerical and experimental studies of two-phase flows in narrow channels, their efforts seem to have been fairly successful in explaining the underlying mechanisms of fluid flow phenomena, especially for slug flow regime. Here, an attempt has been made to explore the hydrodynamics of such flows. In the present study, dodecane and Pd5 have been used as the carrier phases and water is used as the discontinuous phase. The internal diameter of the circular microchannel is 1.5 mm with its wall being insulated. The flow and volume fraction equations are solved by the finite volume approach (FVM). The volume of fluid (VOF) method has been adopted for capturing the interface. The effect of Capillary number on film thickness and interfacial pressure drop is explained. The film thickness is found to increase with Capillary number and is also found to be in a close match with the models available in the literature. The pressure drop per unit length obtained from the CFD study is compared with a standard model available in the literature. The pressure drop across the unit cell is found to be following the phenomenological model. It is observed that the pressure drop at the interface has the highest contribution to the total pressure drop in contrast to the other pressure drops in the channel, with ~50-55% in dodecane-water and ~55-62% in Pd5-water systems. Besides, the distribution of the velocity, axial, and wall pressure fields inside the microcapillary are also discussed.

Highlights

Two-phase slug flow, whether it is liquid-liquid or gas-liquid, is used for the removal of high heat fluxes at the expense of low coolant flow rate
The numerical study of the flow physics of a two-dimensional, axisymmetric, incompressible, laminar liquid-liquid Taylor flow in a circular channel of diameter 1.5 mm has been discussed in the present paper
The results of interfacial pressure drop have shown a considerable contribution of approximately 50-55% and 55-62% for dodecane-water and Pd5-water systems, respectively, to the overall pressure drop

Summary

Introduction

Two-phase slug flow, whether it is liquid-liquid or gas-liquid, is used for the removal of high heat fluxes at the expense of low coolant flow rate. The potentiality of these flows with respect to the liquid-only flows has been studied and reported by many researchers (Triplett et al, 1999; Asadolahi et al, 2011; Asadolahi et al, 2012). In Taylor flows, the presence of a thin liquid film between the wall and droplets, and Taylor vortices inside the liquid slugs are the key factors for the augmentation in the heat and mass transfer rates. Introducing an immiscible liquid droplet in place of gas bubble significantly increases the heat transfer rates. Asthana et al (2011), Ookawara et al (2007), Song et al (2006), and Urbant et al (2008) have discussed a wide variety of applications of liquidliquid slug flows, such as in polymerase chain reaction, Nitration of benzene to toluene, micro separation, and electronics cooling, respectively

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