Numerical study of slug flow heat transfer in microchannels

Abstract

In the present paper, the heat transfer of slug flow in rectangular microchannels is studied numerically. The Al2O3-water nanofluid with the volume fraction of 1% is used as a homogeneous liquid. Three different configurations are considered to investigate the hydrodynamics and heat transfer in the microchannels. Boundary mesh adaptation method is used to capture the liquid film around gas bubbles. Slug flow characteristics are simulated with a very low computational time compared to previous researches. Slug and bubble lengths, liquid film properties, pressure drop, gas void fraction and heat transfer characteristics are studied. Results show that different inlet configurations impact on slug and bubble lengths. Gas hold-up is influenced by vortices and high frequency fluctuations that are created in the liquid film due to the difference between gas and slug acceleration. It is found that the Nusselt number is an increasing function of slug length and unit cell length. The results reveal that the hottest point on the wall is where the back tail vortex is generated. The nanofluid enhances the heat transfer coefficient by 10% in comparison with the pure water.