Numerical Study of Liquid-Liquid Slug Flow Hydrodynamics in Serpentine Microchannel for Biodiesel Production Intensification

Abstract

Biodiesel is highly considered within the industrial and research field because of its high heating value, which enables it to be an excellent alternative to fossil fuels such as petroleum diesel [1]. Studies showed that utilizing microfluidic devices for biodiesel transesterification is highly recommended to replace the mechanically stirred batch reactors where the mass transfer is considered low, and the mixing time is very long [2]. Employing a Slug-based serpentine microchannel will enable stronger internal circulations, which means higher vorticity and consequently enhances the mixing efficiency for biodiesel production intensification. Therefore, this work investigates numerically the hydrodynamics of a slug flow pattern in several serpentine microchannels for biodiesel production intensification using the Volume of Fluid (VOF) method. A straight microchannel was also simulated to compare the impact of the geometry configuration on vorticity. Also, for serpentine microchannels, the impact of the geometrical dimensions (i.e., width, corner shape, and curvature radius) and operational parameters (i.e., alcohol-to-oil ratio) was examined to optimize the microchannel performance. The results showed that the serpentine microchannel achieved higher vorticity by 233% compared to the straight microchannel. The smaller width was found to be better using Dean Number analysis and vorticity measurement. Also, the 90-degree corner shape was found to induce slightly higher vorticity than the rounded shape due to the increment of the unbroken internal circulations because of the sharp intrusion.

Moreover, the longer the curvature radius, the better the vorticity. The very short radius caused over-deformation of the internal circulation that weakened vorticity. Regarding the effect of the molar ratio, the 7.6 molar ratio resulted in a higher number of slugs falling in the range of L/D between 2.3 and 6 compared to the 22.9 molar ratio. The mentioned slug L/D range results in the highest vorticity compared to the vorticity produced by other ranges (i.e., L/D6) in the 22.9 molar ratio.

Date of Award	27 Dec 2023
Original language	American English
Supervisor	Nahla Al Amoodi (Supervisor)