Unified mechanistic multiscale mapping of two-phase flow patterns in microchannels

To better understand the underlying two-phase phenomena and thus better predict transitions between the various two-phase flow patterns, it is necessary to update our way of thinking from one-of-a-kind flow pattern maps of limited applicability to a generalized approach based on first principles, mechanistic analysis and multi-scale characterization and representation of the important features of these complex flows. While in macro-sized channels and pipes this need is typically addressed by the use of empirically-validated flow regime maps, there is – as yet – no consensus on two-phase flow regime maps for microchannels and miniature pipes.This study presents a set of recommendations for the development of a new comprehensive type of flow pattern map that not only covers adiabatic, evaporating and condensing flows in one seamless flow pattern identification tool, but also includes multiscale information about the flow itself, and furthermore contains embedded mechanistic methods for the principal two-phase phenomena for use in developing unified models for pressure gradients, heat transfer, void fraction, CHF, etc., all in one coherent global method.

► Critical review of the available flow regime maps for microchannels.
► Recommendations for the development of a new comprehensive type of flow pattern map.
► An ambitious new roadmap of development is proposed here.