Enhancement of vapor–liquid separation in vertical impact T-junctions for vapor compression systems with flash gas bypass

• Several design options to enhance liquid separation in T-separator are explored.
• The underlying mechanisms are to reduce and change the direction of liquid inertia and decrease phase force interaction.
• A few practical issues are discussed for implementation of T-separator in A/C systems.

As an extension of the previous work studying vapor–liquid separation in vertical impact T-separator (Tuo and Hrnjak, 2013a), this paper presents experimental study of several design options to enhance liquid separation. Five modifications on the baseline T-separator with horizontal inlet are explored using both R134a and R410A as working fluids: inlet inclination angle, dual-inlet as pre-separation, inlet tube diameter, cross-sectional shape and location with respect to the vertical tube. The objective is to avoid or at least delay transition from mist to churn flow by reducing and changing the direction of liquid phase inertia force, and decreasing liquid and vapor force interaction. In addition, a few practical issues are discussed when implementing T-separator in real A/C systems, such as liquid level control, system configuration effect, and periodic reverse flow in microchannel evaporators.