Correlations of void fraction for two-phase refrigerant flow in pipes

• Correlations of void fraction for two-phase flow are reviewed.
• Survey of experimental data of void fraction for two-phase refrigerant flow is conducted.
• Applicability of the existing void fraction correlations to two-phase refrigerant flow is assessed.
• A new void fraction correlation for two-phase refrigerant flow in pipes is proposed.

The calculation of void fraction for two-phase refrigerant flow in pipes is required in many fields. Although numerous void fraction correlations have been proposed and lots of related assessments have been conducted for the past six decades, almost all of them were on the basis of data gained from two-phase flow experiments on air–water or steam–water, whose applicability to two-phase refrigerant flow needs to be evaluated. In this paper, a state-of-the-art survey of correlations and experimental investigations is conducted. There are 41 correlations reviewed, and 1574 experimental data points of 5 refrigerants are compiled, with hydraulic diameters ranging from 0.5 to 10 mm and mass fluxes ranging from 40 to 1000 kg m−2 s−1. Based on the collected data, a comprehensive evaluation of the reviewed correlations is made, and a new correlation which can give fairly good predictions for both macro- and mini-channels is proposed.