Vapor–liquid separation in a vertical impact T-junction for vapor compression systems with flash gas bypass

• Vapor–liquid refrigerant separation in vertical impact T-junction is studied.
• Flow pattern transition and effect on liquid separation are discussed.
• An empirical correlation is proposed as a criterion for separator design.

This paper presents results from experimental study of vapor and liquid refrigerant separation in vertical impact T-junctions using R134a and R410A for application in but not limited to vapor compression systems. Inlet flow rate and quality are varied in the range of 10–35 g s−1 and 10–25%. Flow patterns in the T-junction separator are identified and characterized. It is found that liquid separation efficiency strongly depends on the flow pattern right above the impact region (junction). The efficiency deteriorates dramatically when mist turns into churn flow regime, with increasing inlet flow rate and/or quality. An empirical correlation to predict churn flow transition is proposed as a function of Fr and Xtt. That correlation is a bases for good design of T-junction separators.