The prediction of void fraction and two-phase flow regimes are essential for the accurate calculations of pressure drop and heat transfer in liquid-vapour two-phase flow. Data are presented on flow regime and void fraction measurements for the ozone-safe refrigerant R134a liquid-vapour flow in a horizontal pipe. The experiments covered a wide range of conditions that are typically encountered in refrigerating and air conditioning equipment. The test conditions included the stratified, annular, and intermittent flow regimes. The applicability of flow regime predictive methods was assessed. The data were used for the development of void fraction correlations that can be used for design purposes. An empirical approach was used to correlate the void fraction in terms of the Martinelli parameter. Alternatively, the void fraction data for each flow regime were correlated using the drift-flux model.

KEYWORDS: year 1995, properties, refrigerants, R134a, horizontal, pipes, calculating, voids, pressure drop, heat flow, experiment, fluid flow