Enhancing heat transfer performance in non-mixing liquid slug flow with the use of alumina nanoparticles in microchannels: a numerical study

Abstract

Because of the superior thermal performance and manufacturing readiness, non-mixing two-phase flows in microchannels have recently gained popularity as a method for the implementation of cooling applications. Due to internal fluid recirculation within the slugs, slug-flow is one of the two-phase flow regimes that facilitates greater heat transfer rates in microfluidic devices than other types of two-phase flows. This is because the ratio of surface area to volume of slugs is greater than that of other two-phase flow types. Because of this, the present study is focused on increasing heat transfer capability of two-phase slug flow further by introducing nanoparticles. The nanofluid-based liquid-liquid slug-flow was investigated throughout this research using numerical investigations. The software ANSYS Fluent® was utilised for doing the research in a numerical format. In order to explore the impact that nanoparticles have on the transport of heat, set of numerical investigations were carried out. Nanoparticles made out of aluminium oxide (Al₂O₃) were used for the simulations because of their high heat conductivity, which is also one of the reasons for its excellent physical and chemical stability as a nanofluid. The numerical results were validated against the experimental data that were already published in the literature. The VOF (Volume-of-Fluid) and Eulerian–Eulerian models were utilised in order to successfully capture the interface of a two-phase flow. Using nanoparticles in either phase led to a considerable improvement in heat transport, as demonstrated by the CFD findings. The incorporation of nanoparticles into the secondary phase has resulted in an increase of more than eightfold the Nusselt number compared to two-phase liquid-liquid slug flow. Furthermore, adding nanoparticles to the fluid has a significant increase in its thermal conductivity. 

KEYWORDS:    Numerical Modelling, Nanofluid, CFD, Flow Simulation, Alumina nanoparticles