Abstract
Hydrodynamics plays a major role in transport of heat and mass transfer in microchannels. This includes flow patterns and flow regimes in which the micro-channels are operated. The flow patterns have a major impact the transport properties. Another important aspect is the pressure drop in micro-channels. In the present review, the experimental and Computational Fluid Dynamics (CFD) studies covering all the above aspects have been covered. The effect of geometrical parameters like shape of channel, channel size, material of construction of channels; operating parameters like flow velocity, flow ratio and fluid properties have been presented and analyzed. Experimental and analytical work of different pressure drop models has also been presented. All the literature related to influence of flow patterns on transport properties like volumetric mass transfer coefficients (VMTC) and heat transfer coefficients (HTC) have been presented and analyzed. It is found that most works in Liquid-Liquid Extraction (LLE) systems have been carried out in slug flow and T-junctions. Models for coupled systems of flow and mass transfer have been presented and works carried out for different coupled systems have been listed. CFD simulations match experimental results within 20% deviations in quantitative and qualitative predictions of flow phenomena for most research articles referred in this review. There is a disparity in prediction of a generalized regime map and a generalized regime map for prediction of flow patterns for various systems would need the help of Artificial Intelligence.
Highlights
Microchannels have been an area of interest since the last two decades in various applications including petroleum industries, emulsification, fine and speciality chemicals, extraction processes, biochemical applications etc
2 Approximation of slug movement is considered using the moving boundary approach 3 Outcome of the simulations had no mention of values of volumetric mass transfer coefficients (VMTC) 4 No free surface model was used to tract the deformation of the interface 5 The Sherwood number for rectangular and circular micro-channels has been considered similar 6 Species transport equations have been used for mass transfer 7 VMTC’s obtained from numerical experiments were not validated with experimental results
The brief description is provided as follows: 1. Flow patterns namely parallel, slug, annular, annular-slug, slug-dispersed have been reported by authors but some new patterns like rivulet and serpentine patterns have been observed for liquid-liquid systems in main channels of microchannels
Summary
Microchannels have been an area of interest since the last two decades in various applications including petroleum industries, emulsification, fine and speciality chemicals (like nitration reactions), extraction processes, biochemical applications etc. State of the art of experimental and CFD studies describing flow patterns in liquid-liquid flows have been analyzed This includes flow patterns in different geometries and geometrical parameters like shape, size, material of construction, operating parameters like flow rates, flow ratios, fluids properties of the fluids under consideration, measurement techniques used by researchers to understand internal circulations in slugs of both phases are presented. Pressure drop in microchannels (experimental data) of various authors has been presented for different two phase systems and geometries. The micro-channel geometries are different in cross sectional shape, main channel shape and mixing junction configuration. In the forthcoming sections, we will discuss about the flow patterns, pressure drop in micro-channels using T and Y junctions and review the current experimental and CFD modeling works
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