The distribution over an impacting T-junction of two-phase R32 under heat pump conditions

This experimental work studies the distribution of a two-phase refrigerant flow over a horizontal impacting T-junction. A setup was built which consists of two parts: a flow conditioner and a test section. The flow conditioner creates a two-phase mixtures (R32) at a saturation temperature between 10 °C and 20 °C with a mass flux of 150 to 700 kg/(m².s) and a vapour quality between 0 and 1. In the test section, the two-phase flow is distributed over two identical parallel sections using an impacting T-junction. The backpressure and heat input of each parallel section can be regulated. The mass flow rates and vapour qualities are measured before and after the T-junction. Further, the pressure gradient over the T-junction is measured and the void fraction is determined before the T-junction using a capacitive void fraction sensor. Using design of experiments, the main effects of superficial vapour velocity, superficial liquid velocity and saturation pressure on the distribution of R32 were studied. For R32, the two phases only distribute uniformly over the T-junction when the mass flow rate through the two outlet branches is equal. Further, the experiments show a decreased tendency of the liquid to exit through the outlet with the lowest mass flow rate with increasing vapour superficial velocity. The influence of the superficial liquid velocity was less pronounced and dependent on the superficial vapour velocity. Finally, no effect of the saturation pressure was found. The obtained results were then compared with the results of water-air mixtures found in literature.