A review on numerical studies of slug flow hydrodynamics and heat transfer in microtubes and microchannels

Numerical studies on the hydrodynamic and heat transfer characteristics of two-phase flows in small tubes and channels are reviewed. These flows are non-boiling gas–liquid and liquid–liquid slug flows. The review begins with some general notes and important details of numerical simulation setups. The review is then categorized into two groups of studies: circular and non-circular channels. Different aspects such as slug formation, slug shape, flow pattern, pressure drop and heat transfer are of interest. The primary purpose of the present review is to report the existing numerical studies in order to highlight the research gaps and suggestions for the future numerical simulations. Judging and/or comparing the different works and correlations can be conducted separately for each of the sections reported here. According to this review, there are some large gaps in the research literature, including pressure drop and heat transfer in liquid–liquid slug flows. Gaps in research are also found in applications of non-circular ducts, pressure drop and heat transfer in meandering microtubes and microchannels for both gas–liquid and liquid–liquid two-phase flows.