State-of-the-art of two-phase flow and flow boiling heat transfer and pressure drop of CO2 in macro- and micro-channels

A comprehensive review of flow boiling heat transfer and two-phase flow of CO2 is presented that covers both macro-channel tests (diameters greater than about 3 mm) and micro-channel investigations (diameters less than about 3 mm). The review addresses flow boiling heat transfer experimental studies, macro- and micro-scale heat transfer prediction methods for CO2 and comparisons of these methods to the experimental database, highlighting the various limitations of current approaches and the divergence of some data sets from others. In addition, two-phase flow pattern results available in the literature are summarized and compared to some of the leading flow pattern maps, showing significant deviations for CO2 from the maps prepared for other fluids at lower pressures. Available two-phase pressure drop data for CO2 are also compared to leading prediction methods.