Experimental study on the phase separation behaviors of two-phase refrigerant R134a in the T-junction with microchannel flat branch tube

T-junction is a critical flow distribution component in microchannel heat exchangers and chemical equipment. However, gas-liquid phase flow through T-junctions often leads to flow mal-distribution, due to the complex multiphase flow behavior and multiscale tube structures. In this study, an experimental system was developed to investigate the two-phase flow distribution behavior in the horizontal T-junction, consisting of a semi-transparent PVC header and a heated microchannel parallel flat branch tube. R134a was chosen as the working fluid, with a mass flux range of 1.5 to 5.96 g/s, an inlet quality in the header ranging from 0.16 to 0.7, and an inlet temperature between 10°C and 17°C. The study explores the effects of inlet gas/liquid superficial velocity and inlet quality in the header on phase separation behavior. Based on the dividing streamline theory, a new phase separation model for stratified flow in the T-junction with a microchannel parallel flat branch tube is developed by integrating potential flow theory with complex variable function theory. The correction factor ( C ) in the new model is determined using experimental data. The results demonstrate that the prediction accuracy of the proposed model is significantly improved compared with existing models.