Experimental research on liquid-vapor two-phase flow separation of zeotropic mixtures at an impacting T-junction

Impacting T-junctions could work as a partial vapor-liquid separators by enhancing the mal-distribution of phase that occurs naturally therein. Previous studies have mainly concerned the phase splitting of air-water and pure refrigerants but here the performance of a vertical impacting T-junction using zeotropic mixtures as test fluids is reported. Experiments were conducted to investigate the effect of parameters, including inlet mass velocity, vapor quality, splitting ratio, outlet branch diameter and circulating composition of mixtures, on the liquid separation efficiency, based on mixtures R134a/R245fa and R290/R600a. The inlet flow patterns of each test fluid were also identified by using a high-speed camera under various test conditions. It was found that the mixture composition had an obvious effect on phase splitting at high separation loads, but the separation efficiency would not change linearly versus the R134a mass fraction in mixture R134a/R245fa. Overall, pure refrigerant showed better separation performance than zeotropic mixtures, under the same inlet and outlet conditions. Besides, the vaporization due to pressure drop at T-junction was also discussed by conducting a comparison study between air-water mixture and organic fluids. Calculation results indicated that an increase in pressure drop would promote mass transfer from liquid to vapor phase at the impacting T-junction.